The subfamily Steninae Macleay, 1825 (Coleoptera: Staphylinidae) of Japan
Part 1. Dianous and Stenus (S. comma group to S. guttalis group)
Shun-Ichiro Naomi1, Shûhei Nomura2 and Volker Puthz3
1Natural History Museum and Institute, Chiba,
Aoba-cho 955–2, Chuo-ku, Chiba 260–8682, Japan
E-mail: naostenus@hb.tp1.jp
2
National Museum of Nature and Science,
Amakubo 4–1–1, Tsukuba, Ibaraki 305–0005, Japan
E-mail: nomura@kahaku.go.jp
3
Burgmuseum Schlitz, Naturwissenschaftliche Abteilung,
Vorderburg 1, Schlitz, D-36110, Deutschland
E-mail: stenus.puthz@t-online.de

Abstract This is the ﬁrst part of a monographic study of the subfamilial-level clade Steninae
Macleay, 1825 of Japan (Puthz: Contribution No. 348 on Steninae; Naomi: Contribution No. 56 on
Steninae). It treats taxonomically the genus Dianous, Leach, 1819 (3 species groups and 6 species)and genus Stenus Latreille, 1797 (30 species groups and 117 species), with detailed illustrations oftaxonomically important characters and habitus photos of Japanese species, in order for unambiguously identifying the species and also for aiding in understanding the phylogenetic system of Steninae names. Following 7 Stenus species, S. intumescens (Honshu: Nagano Pref.); S. displicatus (Honshu: Nara and Mie Prefs.); S. varicosus (Honshu: Hyogo); S. ancyleus (Honshu: Nagano Pref.); S.
oliverbetzi (Honshu: Ibaraki, Saitama and Chiba Prefs.); S. kamezawai (Honshu: Nara Pref.); and S.
mystiformis (Shikoku: Tokushima and Ehime Prefs. and Kyushu: Miyazaki and Kumamoto Prefs.)
are described as new to science. The name Stenus nomurai (Naomi: 1988c) is here resurrected from asubjective junior synonym of S. mikado (Hromádka: 1979a); and likewise, the name Stenus weisei(Bernhauer: 1912) is also from a subjective junior synonym of S. sedatus (Sharp: 1889). Dianous
uedai Naomi, 2010b is newly placed in synonym with D. moritai Naomi, 1997e; and likewise, D.
viridicatus Naomi, 1997e with D. japonicus Sawada, 1960; S. hiroyukii Puthz, 2001d with S. melanarius Stephens, 1833; S. abbreviatus Naomi, 2015b with S. mikado Hromádka, 1979a. Stenus pilosiventris Bernhauer, 1915, S. ﬁnalis Ryvkin, 2011, S. spurius Benick, 1929, and S. sibiricus Sahlberg,
1880 are newly recorded from Japan.

Introduction
The subfamilial-level clade Steninae Macleay, 1825, which is characteristic in having thevery large eyes being prominent laterally, belongs to the staphylinine group (sensu Lawrence &Newton, 1982) of Staphylinidae. The Steninae (comprising 3131 species; Puthz in litt.) presently
consists of two genera Dianous, Leach, 1819 and Stenus Latreille, 1797 (Puthz, 1981a); and the
3rd undescribed genus of Steninae is known from Australia (Clarke & Grebennikov, 2009). The
Steninae seems to be presently conﬁrmed as being monophyletic by having a series of larval andadult autapomorphies (e.g., adult: position of the antennal insertion on frons between eyes; possession of the paired pygidial defence glands lying lateral from the rectum; larva: antennomeres
1 and 2 markedly elongate) (Thayer, 2005; Clarke & Grebennikov, 2009).
Stenus (comprising 2896 species; Puthz in litt.) is an extremely speciose clade, virtually, one

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Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthzof the species-richest genera in the animal kingdom. The Stenus beetles are inhabitants of different environments (e.g., moist humus, plant debris, leaf litter, plant leaves; Betz, 1998). Stenus isdistributed world-wide except for New Zealand (Puthz, 1970a, 1971a, 2008a). It is considered tobe obviously monophyletic by a set of autapomorphies (Clarke & Grebennikov, 2009) represented by a protruding elongate labium that has a function as an adhesive prey-capture apparatus(Weinreich, 1968; Puthz, 1981a; Betz, 1996). On the other hand, Dianous comprises 262 species(Puthz, 2016a); and the beetles are mostly inhabitants of bryomadicolous environments (Vaillant,
1955) but a few are inhabitants of such different environments as bark of trees, dead leaves anddry mosses in open forests (Puthz, 1988, 2000). Dianous is distributed only in the Northernhemisphere, with its major distributional range in the Southeast Asia (including China and India)(Puthz, 1981a, 2016a; Shi & Zhou, 2011a, b). It is, however, problematic as to the matter withwhether or not it has good autapomorphies (e.g., Puthz, 1981). For example, in Dianous species,
the labium is only slightly protrusile, without adhesive prey-capture apparatus; this is seemingly
plesiomorphic relative to the condition that Stenus shows, suggesting that the Dianous is a paraphyletic group (Puthz, 1981).
Although the 3rd undescribed Stenine genus of southern Australia was not treated in theirstudy, Koerner et al. (2013) ﬁrst hypothesized the evolutionary origin of Dianous within the Stenus, based on the molecular phylogenetic approach, using the COI gene in 30 Stenus and 12
Dianous species. Their results obviously suggest a secondary loss of the specialized prey-capture
apparatus from Dianous. On the other hand, Schierling et al. (2013) showed that there are threechemotaxonomic groups in Steninae (basal piperidine group; pyridine group; and the most
evolved epoxypiperideine group); and also that Dianous coerulescens belongs to the basal piperidine group. However, by using three genes (COI, 16S rRNA and Histone) in 17 Stenus and 4
Dianous species, Lang et al. (2015) provided further insights into the molecular phylogeny ofSteninae: Those 4 Dianous species are nested within the basal piperidine Stenus group cluster.
This result supports the hypothesis of Koerner et al (2013) concerning the evolutionary origin of
Dianous within the clade Stenus. In order for conﬁrming their hypothesis, however, further studies will be needed based on the larger number of species including those of the Australian 3rd
genus.
The genus Stenus Latreille, 1797 has long been divided into 6 subgenera since the second
half of 19th century, only on the basis of several convenient characters. All of these subgenera
formally recognized under the traditional classiﬁcation of Stenus are at base non-natural (i.e.
“paraphyletic” or “polyphyletic” in the Hennigian sense). (For further information on Stenus taxonomy, see introductory part of ʻGenus Stenusʼ in the descriptive section.) Modern stenologists
now acknowledge that the traditional subgeneric classiﬁcation simply hinders construction anddevelopment of the truly phylogenetic system of Stenus names. Puthz (2008a) suggested to discard the traditional subgeneric classiﬁcation and decided to gather Stenus species into virtuallymonophyletic species groups. Some colleagues have already begun to directly gather Stenus species into monophyletic species groups, without using the traditional subgeneric names such as
Parastenus, Hemistenus and Hypostenus (e.g., Tang, Zhao and Puthz, 2008; Naomi, 2012).
As necessary steps for systematizing the Stenus of the world into monophyletic species
groups, Puthz have published a series of reviews on Stenus taxonomy. First of all, a general taxonomic review of Stenus at the level of species groups of the world was published by Puthz(2008a), where the 157 named species groups are enumerated and taxonomically surveyed. After
that, several review-papers about the Stenus are followed: First, the Stenus from Africa and Madagascar was reviewed by Puthz (2011a), showing that the Stenus from there comprises about 350

The Steninae of Japan Part 1

3

species. Second, the Stenus from Oriental region was reviewed by Puthz (2013), resulting that
the Stenus from there comprises about 650 species. Third, the Stenus of Melanesian subregion(comprising 152 species) was reviewed by Puthz (2016b,c). See (Puthz 2006a, 2015b, 2016d,
and forthcoming) regarding the revisions on the Stenus of Neotropical region; and see Puthz(1970a, 2010a) regarding the Steninae fauna of Austral region.
As far as the Dianous is concerned, Puthz (1981a, 2000, 2015a, 2016a) studied at base thespecies of this genus world-wide, and showed that the genus is phylogenetically divided into twogroups (group I and II). For further information on Dianous taxonomy, see introductory part ofʻGenus Dianousʼ in the descriptive section.
Keeping in our mind the on-going development of establishing the phylogenetic frameworkof Steninae taxonomy by the afore-mentioned (Puthz, 1971a, 1981a, 2000, 2008a, 2011a, 2013,2015a, 2016a) and related papers (e.g., Naomi, 2006a, 2012; Puthz, 2014, 2015b), this paper
aims at clarifying the Japanese fauna of Steninae. The Steninae fauna of Japan presently consist
of Dianous (3 species groups and 6 species) and Stenus (347 species and 34 species groups); seealso the section of “History of Taxoxomic Studies on the Japanese Steninae”. Notice that the
Dianous is here taxonomically recognized as a genus in Steninae until the phylogeny of Steninae
is adequately clariﬁed. As the ﬁrst part of a monographic study of Japanese Steninae, this paper
treats taxonomically the Dianous (all species groups and species) and Stenus (30 species groups[i.e., S. comma group to S. guttalis group] and 117 species), with the detailed illustrations of taxonomically important characters and the habitus photos of Japanese species, in order for unambiguously identifying the species and also for aiding in understanding the phylogenetic system ofSteninae names.
Materials of the Steninae treated
The holotypes of the most species of Stenus and Dianous treated are examined by Puthz and /or Naomi. The beetles of Steninae examined for the present study are collected by Nomura,
Naomi and our coleopterist colleagues. Depositories of the types and other specimens examined
are as follows:
Institutions:
EUM: Ehime University, Matsuyama
DEIM: Deutsches Entomologosches Institut, Münchberg
FMC: Field Museum of Natural History, Chicago
IRSNB: Institut Royal des Sciences Naturelles de Belgique, Bruxelles
KUF: Kyushu University, Fukuoka
KUMF: Kyushu University Museum, Fukuoka
MHNG: Muséum dʼhistoire naturelle, Genève
CBM: Natural History Museum and Institute, Chiba
MNB: Museum für Naturkunde, Humboldt Universität, Berlin
NHML: Natural History Museum, London
NHMW: Naturhistorisches Museum, WienNMNHW: National Museum of Natural History, Washington, D. C.
NMNST: National Museum of Nature and Science, Tsukuba
OMNH: Osaka Museum of Natural History, Osaka
SMF: Senckenberg Museum, Frankfurt a. M.

4Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

SMNS: Staatliches Museum für Naturkunde, Stuttgart
TUAA: Tokyo University of Agriculture, Atsugi
ZIRAS: Zoological Institute of the Russian Academy of Science, St. Petersburg
ZMH: Zoological Museum, Helsinki
ZMMSU: Zoological Museum of the Moscow State University, Moscow
Private collections:cH: Collection of Lubomir Hromádka, PrahacI: Collection of Tateo Ito, Kyoto
cK: Collection of Hiromu Kamezawa, Saitama
cN: Collection of Shun-Ichiro Naomi, Chiba
cP: Collection of Volker Puthz, Schlitz (which is to be deposited in SMNS)
cSa: Collection of Kohei Sawada, Ohsaka
cS in NMNST: Collection of Aleš Smetana deposited in NMNSTIn cases of the Steninae specimens whose depository is not indicated in “Material examined”,
the specimens presently belong to the collection of Naomi. However, “cN” is added after somespecimens (e.g., paratypes) examined when its addition is considered better for clearly showing
their depositories.
Methods of the Dissection for Observation and Illustration
Postabdomen and aedeagus
Dried specimens are used for dissecting the postabdomen (i.e., 8th to 10th abdominal segments) and aedeagus and also for observing their morphology. Before doing a dissection, a specimen (to be dissected) is boiled in water during several minutes for softening the body, and is dissected under the binocular Wild M8. The postabdomen and aedeagus separated are mounted in
Euparal (Chroma-Gesselschaft) on a plastic card, which is to be pinned under the specimen, fromwhich those parts are dismembered. The postabdomen and aedeagus embedding in the Euparal
are illustrated under the microscope Olympus CH-2, using ocular mesh.
Spermatheca
Dried specimens are used also for dissecting and observing the spermatheca. A female specimen is ﬁrst boiled in water during several minutes for softening the body. After the postabdomen
is separated from other parts of the body, it is boiled again in a KOH solution (about 5%) during
several minutes for dissolving the fat bodies around the spermatheca so that we can clearlyobserve the spermatheca. Before doing illustrations, the gonocoxites, together with a spermatheca, are separated from the terga 9 and 10, for making it easy to illustrate the spermatheca. An
important point here is to see that, in some cases where the spermatheca is not very strongly
sclerorized (i.e., not robust) nor pigmented, the spermatheca (especially its RT-duct) is more orless deformed and/or at least partially melted away when it is embedded into the Euparal. Given
this, the spermatheca be soaked in a drop of water on the slide glass, covered by a cover glass,and then observed and illustrated under the microscope, before embedding it into the Euparal.
Maruyama (2006: 4) also recommended a similar procedure of illustrating the Aleocharine spermatheca.
The spermatheca of a Stenus species can be illustrated only in cases where it is more or less

The Steninae of Japan Part 1

Fig. 1.

5

Stenus comma LeConte. Postabdomen with the aedeagus partially outthrusted posteriorly.

sclerotized so that we can observe it under the microscope. The entirely membranous spermatheca of Stenus (e.g., those in S. comma group, S. humilis group, etc.) is mostly or completely
melted away, before the fat bodies around the spermatheca are dissolved while it is soaked into a
KOH solution. Thus, those entirely membranous spermathecae of Stenus cannot be illustrated
because of the technical difﬁculty in observing them.
Characters Used for the Taxonomy of Steninae
Characters used for the taxonomy of Steninae are described in this section. External structures of body, which are common in male and female, are ﬁrst described. Separately taken up anddescribed are the external structures of body (abdominal ventrite modiﬁcations of male; postabdomen; and cleaning comb) and the internal structures of body (aedeagus and its endophallic
structures; and spermatheca). Homology of some endophallic sclerites are also brieﬂy discussed.
External structures of body
For many of the species groups in Steninae, the shapes (or general structures) of head, prothorax, elytra and abdomen (Fig. 1) are more or less unique; and thus those shapes are useful forunderstanding, to which group a Stenine beetle belongs; and so is the body length. The body is
unicolorous (dark red or dark brown or black) in most species, but it is sometimes bicolorous asin S. ﬂavidulus (Fig. 135C), and brilliantly metallic, for example, in most New Guinean species(e.g., Puthz, 1972a, 2016b, c). It has metallic lustre in S. comma group (Fig. 127F–K), S. clavicornis group (Fig. 128A, B), etc. Elytra are unicolorous in general, but they are sometimes spot-6

Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

ted with a pair of yellow to yellowish red, round maculae in S. comma (Fig. 127F), S. bicolon(Fig. 135I), etc. Legs are unicolorous, namely, entirely yellow or yellowish brown, e.g. in S.
depressus (Fig. 133E); or entirely black, e.g., in S. comma (Fig. 127F); or they are bicolorous,
yellowish red to yellowish brown with knees more or less infuscate, e.g. in S. distans (Fig. 128I),
or bicolorous in different color pattern, e.g. in S. cicindeloides (Fig. 134H).
Head has eyes which are prominent laterally. Vertexal area between the eyes are usuallymore or less concave, with paired longitudinal depressions or grooves; median longitudinal area
between the depressions are weakly convex or swollen in most species. However, the vertexal
area is almost simply ﬂat (i.e. hardly convex nor provided with paired longitudinal grooves) in S.
piliferus group, simply convex or swollen in different species groups. Basically, the morphology
of mouthparts are not so important for grouping the Stenus species, but different forms of theparaglossae of labium are identiﬁed as valuable for grouping the species (e.g., Puthz, 2011b, ﬁgs.
1–4, 2013, ﬁgs. 14–17). Three different forms of paraglossae are observed in Stenus species fromthe Japan and adjacent regions. First, the species of S. sharpi group has elongate-oval paraglossae (S. sharpi, Fig. 2bA–D). Second, the species of S. abdominalis group have conical or elongate-conical paraglossae (e.g., S. bicolon posticus, Fig. 2bH–I; S. coronatus, Fig. 2bF–G). See
also Fig. 2bE for the other example of elongate-conical paraglossae of the Oriental species (S. cf.
luteolunatus). Third, the species of many other species groups in Stenus show the common (i.e.,
ovoidal or oval) condition of paraglossae (e.g., S. biguttatus, Fig. 2aA; S. juno, Fig. 2aB; S. cicindeloides, Fig. 2aC, D; S. gestroi, Fig. 2aE, F; S. guttalis, Fig. 2aG).
Pronotum is strongly convex dorsally, often with a median longitudinal depression or
impunctate area, and it is exceptionally with lateral spines (S. prospector Fauvel, 1907) or withdorsal protuberances (in the S. coelogaster group, e.g., S. monstrosicollis Bernhauer, 1915). Forewings (i.e., elytra) have the developed humeri (Fig. 128A) or are narrowed anteriorly (Figs.
127D, 129H–L), and they are exceptionally with lateral spines (S. spinipennis Puthz, 2006c, ﬁg.
85). Hind wings are developed (or macropterous) or atrophied (or brachypterous) in each species, but some species (e.g., S. hirtiventris) show both conditions. Legs are short (Fig. 134A)
through moderately long (Fig. 134E) to long (Fig. 134F, G) or very long (Fig. 134J–L). The tarsomeres are simple in structure. Otherwise, the 4th tarsomere is often strongly bilobed; and the
2nd and 3rd are also sometimes bilobed in various degrees. The tarsomeres are each usually symmetrical in structure, but they are sometimes bilobed in an asymmetrical manner; for example,
the 3rd tarsomere is weakly, asymmetrically bilobed, with its mesial lap longer than lateral one in
S. piliferus group, etc.; see Betz (2003) and Puthz (2006d) for further information.
Abdomen is narrowed posteriorly (Fig. 133L) or subparallel-sided (Fig. 135I); it is more orless ﬂat above (Fig. 133E–G), moderately convex dorsally, or almost cylindrical (Fig. 134A–L,
etc.). Lateroventrites are very narrow or narrow through moderately wide to very wide, but they
are very often completely missing. The lateroventrite turns ventromesially (Fig. 3B) or dorsomesially (Fig. 3D); or they are horizontal in position (Fig. 3C).
The surface of body is usually covered with punctures; and interstices between the punctures
are covered with reticulate-microsculptures, or they are smooth and shining. Shape, density andsize of the punctures are different from one body part to another in usual. For example, the punctures on elytra are larger than those on abdomen. Shape, density and size of the punctures arealso different from one species to another in most cases, but the punctate conditions on body tend
to be similar among the species of a same species group. The surface of body is covered alsowith pubescence (or short setae) or almost glabrous in usual, but it is rarely covered with long,
suberect setae in S. hirtiventris (Fig. 132I), S. hirtellus (Fig. 133J), S. sedatus (Fig. 134F), S.

The Steninae of Japan Part 1

7

Fig. 2a. A, Stenus biguttatus (Linnaeus); B, S. juno Paykull; C, D, S. cicindeloides (Schaller); E, F, S. gestroi
Fauvel; G, S. guttalis Fauvel. A, B, D, F, G, paraglossae (ventral view); C, E, ditto (dorsal view).

weisei (Fig. 134G) and in S. cirrus group.
Abdominal ventrite modiﬁcations of male
Several posterior ventrites of male abdomen are more or less morphologically modiﬁed byﬂatness (or ﬂat area), depressions, ridges, emargination, protrusion, setation and punctation.
Examples of the modiﬁcations in the case of abdominal ventrites (shown in Fig. 3A) are the ﬂatarea (5th ventrite), shallow depression with dense punctures (6th ventrite), moderately deep
depression with lateral ridges, posterolateral protrusions, and also with dense setae (7th ventrite),
median shallow depression (8th ventrite) and emarginations of various degrees (5th to 8th ventrites).

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Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

Fig. 2b. A–D, S. sharpi; E, S. cf. luteolunatus Puthz, 1972e; F, G, S. coronatus Benick; H, I, S. bicolon posticus
Fauvel. A, E, F, H, paraglossae (dorsal view); B–D, G, I, ditto (ventral view).

The Steninae of Japan Part 1

Fig. 3. Diagrams. A, 5th to 8th ventrites of male showing secondary modiﬁcations (ventral view); B–D, abdominal segment showing the location of a lateroventrite (caudal view); E, F, 9th and 10th terga of male (dorsalview); G, apex of 10th tergum of male and female (dorsal view); H, 9th and 10th terga of female (dorsalview).

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Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

Postabdomen of male
Eighth tergum. Eighth tergum of male is widely rounded apically in usual, but in S. ﬂavidulus, it has a wide apical emargination (Fig. 112G). In the species of S. similis group (e.g., Puthz,
2008a: 174), S. coelogaster group, and S. bispinus group, it has an apicomedian tuft of setae.
Ninth tergum. Ninth tergum of male is dorsal in position, but the lateral parts always more orless extend ventrally to form ventral ﬂaps (Fig. 3E, F). The anterior rim is stout, and a little
thicker than in female (Fig. 3H); and the anterior rim is anterolaterally continuous to the ventral
apophysis (Fig. 3E, F). Small ﬂaps are also sometimes found in a pair at the lateral parts of theanterior rim (Fig. 3E, F: anterolateral ﬂap). The anterolateral ﬂaps are very long in some speciesof S. piliferus group; and they are very thick in some species of S. clavicornis group, or very
thick and spatulate in S. juno. The 9th tergum projects posterolaterally to form the posterolateralprojection (Fig. 3E, F), so that the posteromedian part forms an emargination, which is usuallywide and transverse. Along the posterior margin of 9th tergum, a cleaning comb is found in some
Stenus species; (see the subsection “Cleaning comb in the postabdomen”).
Ninth ventrite. Ninth ventrite of male is composed of the single, median ventral plate (Fig.
4A, E), which is in-situ partly wrapped laterally by the ventral ﬂaps of 9th tergum. Ninth ventrite
is usually elongate, and basally with the stem. When the lateral side of a stem is incised (Fig. 4E:
basilateral emargination), the basilateral part of 9th ventrite projects anteriorly to form the basilateral process (Fig. 4E). The 9th ventrite is provided apicolaterally with paired teeth (Fig. 4A:
apicolateral tooth) and tufts of setae (Fig. 4A: apicolateral setae). The apicolateral teeth are eachlong (Fig. 4A), short (Fig. 4B), thin and incurved (or falcate; Fig. 4C); or they are missing insome cases (Fig. 4D; e.g., S. comma group). The posterior margin of 9th ventrite is almost
straight (Fig. 4A) or weakly rounded posteriorly (i.e., rounded toward the caudal direction; Fig.
4C); or the 9th ventrite is weakly emarginate posteriorly (Fig. 4D, E). The posterior margin issmooth (e.g., Fig. 4A) or weakly serrate (Fig. 4B, D). Notice here that, regarding the structure of
the posterior part of 9th ventrite, other diverse forms are found in Stenus from other zoogeographical regions (e.g., Puthz, 2013, ﬁgs. 50–57, 60–69). The ventral surface of 9th ventrite hasposteriorly the pubescent area (Fig. 4A, E); and the macrosetae in pair are often found in the
pubescent area (Fig. 4A, E).
Tenth tergum. Tenth tergum of male is the simple, median plate which is dorsal in position;and it is always smaller than the 9th tergum (Fig. 3E, F). The 10th tergum is short in usual but
sometimes elongate (e.g., S. circularis group, Fig. 65B; S. melanarius group, Fig. 69A). The posterior area is diverse in shape (e.g., Puthz, 2013, ﬁgs. 147–166). In Japanese species, the 10 tergum is posteriorly rounded or entire (Fig. 3E); or it is weakly emarginate posteromedially (Fig.
3G), or rarely with the wide posterior emargination (Fig. 3F; S. rorellus group, Fig. 97B).
Postabdomen of female
Eighth tergum. As in male, 8th tergum of female is widely rounded apically in usual, but it
has a wide, apical emargination in S. ﬂavidulus. In the species of S. similis group (e.g., Puthz,
2008a: 174), S. coelogaster group, and S. bispinus group, it has an apicomedian tuft of setae, as
in male (Puthz, 2008a).
Ninth tergum. Ninth tergum of female is dorsal in position, and the lateral parts extend ventrally to form ventral ﬂaps, which are obviously smaller than in male (Fig. 3H). The 9th tergum
has the thin anterior rim, without ventral apophysis (Fig. 3H). The 9th tergum projects posterolaterally to form the posterolateral projection (Fig. 3H) and also posterior emargination, as in male.
Along the posterior margin of 9th tergum, a cleaning comb is found in some Stenus species, as in

The Steninae of Japan Part 1

Fig. 4. Diagrams. A, E, 9th ventrite of male (ventral view); B–D, apex of 9th ventrite of male (ventral view); F,
G, gonocoxite of female (ventral view).

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Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

male; (see the subsection “Cleaning comb in the postabdomen”).
Gonocoxites. In Staphylinidae, gonocoxites (elements of 9th abdominal segment) each consist of a proximal sclerite, distal sclerite and stylus (Naomi, 1989e); and in Steninae, such primitive conditions are found in some Dianous species (e.g., Figs. 8B, 9E). In many Stenus species,
the proximal and distal sclerites are at least partially fused to form an elongate sclerite, althoughdemarcation line between the proximal and distal sclerites retains to some degrees (Fig. 4F). The
gonocoxal stylus completely disappears in Stenus; (notice however it is at least theoretically possible that a pointed apicolateral tooth can be regarded as a morphological production as a resultof fusing the stylus with distal gonocoxal sclerite). Thus, in Steninae, the gonocoxal element ofeach side is usually represented by a single, elongate sclerite (e.g., Fig. 4F), so that we here simply call it ʻgonocoxiteʼ for descriptive purpose.
The gonocoxites are usually composed of paired plates (Fig. 4F, G), which are ventral in
position; and they are in-situ contiguous mesially as in Fig. 4F, G, and partly wrapped laterally
by the ventral ﬂaps of 9th tergum. The gonocoxite is apicomesially rounded, obtusely angulate,or provided with a tooth (Fig. 4F: apicomesial tooth); and it is apicolaterally with a tooth (Fig.
4A: apicolateral tooth) and tufts of setae (Fig. 4A: apicolateral setae). The apicolateral tooth issimply short or long; or they are falcate, e.g. in S. concinnus (Fig. 92A), S. hirtellus (Fig. 94E);
or they are missing (Fig. 4G), e.g. in S. comma group (Fig. 14G). The posterior margin of gonocoxite is smooth, regularly (Fig. 4G) or irregularly (Fig. 4F) serrate.
Tenth tergum. Tenth tergum of female is the simple, median plate which is dorsal in position
as in male; and it is always smaller than the 9th tergum (Fig. 3H). The 10th tergum is short inusual but sometimes elongate (e.g., S. circularis group, Fig. 65C; S. melanarius group). The 10th
tergum is rounded posteriorly (Fig. 3H); or it is weakly emarginate posteromedially (Fig. 3G), or
rarely with the wide, posterior emargination (e.g., S. rorellus group, Fig. 97C).
Cleaning comb in the postabdomen
The fringes of spinules (or microtrichiae) are frequently found at or toward the posterior
margins of abdominal terga in Coleoptera (Hammond, 1979). For example, in almost all Staphylinidae, the beetles of winged species bear a single fringe of spinules on the posterior margin of
7th tergum (Hammond, 1979; Blum, 1979). The fringes of staphylinids or other beetles havebeen referred to as “Hautsaum” (Szekessy, 1939), “fringing setae” (Kistner, 1976), etc. The fringe
has primarily a function of alar toiletry although it also has another function of unfolding the alae
(Hammond, 1979: 137). The type, number and position of alar toiletry fringe varies from one
group to another.
As pointed by Hammond (1979), additional fringes occur in some groups of Stenus (see also
Hammond, 1975, ﬁg. 9d). In Stenus, there exists a regular line of thick, straight setae of samelength along the posterior margin of 9th tergum of male and female (e.g., Fig. 97B, C); here we
refer to it as (alar) cleaning comb. An important point here is that, in the case of Stenus, a cleaning comb is not composed of spinules, but distinctly of setae with sockets. Such line of thicksetae is found in all Japanese macropterous species of S. seminiger group, S. piliferus group, S.
rorellus group, S. cylindricollis group, S, coelogaster group, S. wasmanni group, S. pulcher
group, S. bispinus group and S. sharpi group, and 3 species of S. gibbicollis group (i.e., S. nomurai, S. varicosus and S. mikado). However, as far as we know, one brachypterous species (S.
sharpi) retain the comb in the 9th tergum; see “Remarks” of S. sharpi in the section of “Descriptions” regarding the further information on it.
A similar line of thick setae is found along the posterior margin of 10th tergum in the male

The Steninae of Japan Part 1

13(Fig. 8F) and female (Fig. 8G) of Dianous. Given the structure of those setae, we here hypothesize that it is also a candidate of cleaning comb.
Aedeagus
Aedeagus is composed of median lobe and paired parameres (Fig. 5A); notice here that in
the aedeagus of Steninae, dorsal (or parameral) side is in-situ the side where the parameral bases
attach (Fig. 1) and the basal foramen is open, while ventral (or non-parameral) side is the side
where the apical foramen is open (Fig. 5A). Several sclerotized structures (sclerites, bands,
tubes, etc.) are found inside the median lobe, which are here called “endophallic structures”.
Median lobe. Median lobe is more or less bulbous and weakly sclerotized basally, laterallywith sclerotized rim (Fig. 5A: lateral sclerotized rim), apicolaterally with or without angulate
corner (Fig. 5A: apicolateral corner), and apically with sclerotized area (Fig. 5A: apical sclerotized area). The apical sclerotized area is highly diverse morphologically; and it is sometimes
with a median longitudinal keel (ventral) and / or apicomedian projection (Fig. 5A). The dorsalside of median lobe is strongly sclerotized and largely concave medially (Fig. 1), while its ventral side is more or less convex, and it is wrapped laterally with the moderately sclerotized wall(Fig. 5A: ventral wall). The basal foramen is a relatively small, round hole surrounded by thesclerotized rim, the posteromedian part of which is provided with a sclerotized protuberance(Fig. 5A: posteromedian protuberance). On the other hand, the apical foramen is large and bothposteriorly and laterally surrounded with sclerotized rim, but the anterior rim is rather indistinct
because it is membranous and hardly pigmented (Fig. 5A).
The median lobe is highly diverse morphologically in Steninae, so that it is one of the mostimportant characters for species identiﬁcation. In general, it is bilateral-symmetrically built, but
it has asymmetrical shape in the Neotropical S. aeneas group (Puthz, 1984c) and also in the Neotropical species S. perpulcher Solsky, 1875 (Puthz, 2000a). Although its varied forms are notspeciﬁed here, some peculiar structural modiﬁcations found in S. humilis group are described
below: At the apical part of median lobe (where the sclerotization is weak), often found is aunique subtransparent area (but not a hole), which is characteristically round, ovoidal or ellipticalin shape when seen ventrally (Fig. 5B, C). The weakly sclerotized area is here called “apicomedian subtransparent area” (Fig. 5B, C). There exist a pair of small teeth (or humps) usually at themesial edges of the sclerotized, ventro-lateral rims of median lobe (Fig. 5B, C). The tooth is,when seen ventrally, almost located at the apicolateral part of median lobe (i.e., a little before theapicolateral corner of the apical sclerotized area of median lobe). Given the location of the toothin the median lobe, the tooth is here called “apicolateral tooth” in usual (Fig. 5B, C), but when
the apex of apicolateral tooth is almost rounded, it is called “apicolateral hump”. The apicolateral
tooth turns mesially in usual (Fig. 5B) but in some species it turns laterally (Fig. 5C), for example, in S. wasamatanus (Fig. 51B) and S. displicatus (Fig. 56E).
Endophallic structures. Ejaculatory duct enters into median lobe from its basal foramen, andthen goes into the basal room of basal tube where a spermatophore may be shaped. Before ejaculatory duct enters into the basal room, it goes through a sclerotized ring (Fig. 5A: basal ring) insome species; and the ring can be distinctly observed, e.g. in S. bifoveolatus (Fig. 87F), S. hirtellus (Fig. 94D), S. oblitus (Fig. 95B). The function of the ring is unknown, but it may be to protect the ejaculatory duct from its deformation by physical pressure. In S. humilis group, a basalring-like structure is found in common (Figs. 40E, 41C). Given its position and shape, the ringseems to be homologous with the basal ring that we observed, e.g. in S. hirtellus, but presently
we cannot ascertain whether the ring is located inside a highly membranous basal room, or out-

14

Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

Fig. 5. Diagrams. A, aedeagus with endophallic structures (but not groundplan of the aedeagus of Steninae); B,
C, posterior part of aedeagal median lobe, showing its specialized structures such as apicolateral teeth.

The Steninae of Japan Part 1

15

side it.
Under the in-situ condition, a rod-like tube exists at the base of median lobe, so that it is here
called basal tube (Fig. 5A); it has been also called “copulatory piece”, “ﬂagellum”, “endophallus”, etc. in descriptive studies. The basal tube is morphologically diverse; and for example itexists as a sclerotized (but more or less ﬂexible) ﬂagellum (e.g. S. ﬂagellifer group), as a spiculose ﬂexible (and submembranous) tube (e.g., S. confertus, Fig. 97F; Puthz, 2013, ﬁg. 222), or asa stiff, sclerotized tube (common in Stenus, Fig. 5A). When it is stiff, the basal tube is composedof basal room and tube body (Naomi, 2006), with basal constriction often existing as the demarcation between them (Fig. 5A).
The inner sac is an eversible sac which connects the base of basal tube with the rim of apicalforamen of median lobe (Fig. 6D). The inner sac completely wraps the basal tube in usual (Fig.
5A); and it is inverted during a copulation because the basal tube is outthrusted as an intromittent
organ (Fig. 6). The inner sac is completely membranous and non-pigmented in many cases sothat it is not observable, but it sometimes is submembranous and weakly pigmented; or it isdensely covered with spinules and / or small tubercles in some species of S. gibbicollis group(Fig. 76C), S. piliferus group (Fig. 96C), etc. In S. comma group, the inner sac around the basal
tube is weakly sclerotized and also uniquely formed so that it is here called “cloak-like sclerite”.
It seems that the shape of the cloak-like sclerite (Fig. 17A, B) is more or less speciﬁc for every
species of this species group (e.g., Figs. 18F, 19D; Puthz, 2008b, ﬁgs.1, 10–15). In some speciesof S. pallitarsis group (Figs. 87F, 88A), interestingly, the inner sac is strongly sclerotized.
Followings are probably considered accessory structures of the endophallic inner sac.
Median longitudinal bands (Fig. 5A–C) are paired bands which are located ventrally relative tothe basal tube; and they are always ﬁrmly bent dorsoventrally near the anterior margin of apicalsclerotized area. The dorsally bent part of a band is here called dorsal band, while the ventrally
bent part of a band is ventral band (Fig. 5A). Lateral longitudinal bands are paired bands which
are located lateral to the median longitudinal bands (Fig. 5A); they are usually small, narrow,short and observable only in some species. Expulsion hooks are located dorsally relative to thebasal tube (Fig. 5A); they are usually paired, separated and connected each other by a transverserod (Fig. 5A: connecting rod). Each hook is composed of anterior and posterior plates (Fig. 5A),
but these plates are often fused into a simple sclerite or plate. The expulsion hooks are also
sometimes fused to form a single median hook, e.g. in S. comma group (Fig. 14D), S. humilis
group (Fig. 5B, C; Fig. 38F), S. ﬂavipes group (Fig. 90A); or they are atrophied into small sclerites, e.g. in S. oblitus (Fig. 95B). Median sclerite rarely exists between expulsion hooks (Fig.
5A), when seen ventrally; and it is dorsal in position relative to median longitudinal bands. It issometimes franked anterolaterally with apicolateral plates (Fig. 5A). Regarding the further
information of endophallic median sclerite and apicolateral plates, see subsection “Homology ofsome endophallic sclerites”.
The important endophallic elements for outthrusting the basal tube by male during a coitus
are expulsion hooks and median longitudinal bands (Puthz, 1971a: ﬁgs. 27–30). Since understanding of the functions of those endophallic elements aids us in understanding their morphological structures, we also provide the illustrations as to how to outthrust the basal tube by male(Fig. 6A–D). The endophallic elements of a median lobe are in-situ located as in Fig. 6A; noticehere that the median longitudinal bands are each ﬁrmly bent dorsoventrally. When the expulsion
hooks begin to turn over ventrally by using the posterior end of each expulsion hook as a fulcrum, they virtually put the median longitudinal bands a bit toward ventral direction (Fig. 6B).
Then, the median longitudinal bands each become loose so that the ventral and dorsal bands are16

Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

Fig. 6. Diagrams showing how to outthrust the endophallic basal tube by male during a coitus. A, in-situ condition of endophallic structures; B, expulsion hooks begin to slightly turn over ventrally so that median longitudinal band becomes loose; C, median longitudinal band gradually stretches posteriorly out, by posteriorly rolling out its dorsal band; D, basal tube is completely outthrusted.

The Steninae of Japan Part 1

17

separated dorsoventrally (Fig. 6B). In proportion to the degree to which the expulsion hooks turnover ventrally, the median longitudinal bands gradually stretch posteriorly out, by posteriorly
rolling out the dorsal bands (Fig. 6C). The posterior rolling-out of dorsal bands is considered tooccur probably in accordance with the reverse movement of inner sac, which results in outthrusting the basal tube (Fig. 6D); notice here that the anterior end of an expulsion hook in in-situ condition (Fig. 6A) is located at the most posterior end of the hook when the basal tube is completely outthrusted (Fig. 6D; Puthz, 1971a).
Parameres. Parameres are paired and rod-like (Fig. 5A); they are symmetrical but very rarely
asymmetrical (e.g., S. operosus Erichson, 1840; see Puthz, 1971a, ﬁg. 18). Each paramere is connected with median lobe by the lateral or anterolateral side of the sclerotized rim of basal foramen; and it extends posteriorly a little before, at or beyond the apex of median lobe. The paramere is usually composed of the base, stem and apical area. The base is more or less thick andstout in usual, and sometimes is provided with posteromesial projection (Fig. 5A). The stem isthin, moderately thick or very thick; and it is almost straight, weakly incurved or sinuous, or
uniquely, strongly sinuous, e.g. in S. riukiuensis (Fig. 66A). The apical area is more or less swollen mesially so that we can call it “apical swollen area” also (Fig. 5A; see also Naomi, 2006a).
The apical area is furnished sparsely or densely with setae; and the setae occur at the apicalmost
part (Fig. 19A), and also on the mesial surface (Fig. 45A), or along the mesial margin (Fig. 31A),
of apical area. The setae occurring there are uniformly short or moderately long; they are otherwise various in length. In S. glaber Benick, 1938 (S. tenuimarginalis group; Puthz, 2013, ﬁg.
313) and S. lorifer Puthz, 1981c (S. pulcher group), the surface of parameral seta is densely
tuberculate.
Homology of some endophallic sclerites
It is in fact difﬁcult for coleopterists to homologize some small endophallic sclerites in Stenus, so that we here discuss the matter with median sclerite (Fig. 5A), apicolateral plates (Fig.
5A) and “ventral sclerites”.
Median sclerite. The endophallic median sclerite (Fig. 5A) always exists together with
expulsion hook(s) (Fig. 5A); and it is usually arrowhead-like and sclerotized. It is found only in
S. raddei (Fig. 70C), S. shogun (Fig. 71A), S. bifoveolatus (Fig. 87A), S. latitarsis (Fig. 88A) andS. currax (Fig. 113C) within the Japanese species of Stenus. The difﬁculty in identifying themedian sclerite is that it is very similar both in structure and position to a fused condition of
expulsion hook. For example, the arrowhead-like sclerite in the endophallus of S. sexualis (Fig.
65A) (and also of S. concavifrons Puthz, 2003a, ﬁgs. 9, 10) is not the median sclerite but it is a
fused expulsion hook. This is evidently so because the incomplete fused area is found at its
anteromedial part; in other words, it is a partially fused expulsion hook in S. sexualis and its
allied species. This is true also of the endophallus of S. gestroi (Fig. 125B; Puthz, 2011b, ﬁg. 13).
Apicolateral plates. The endophallic apicolateral plates (Fig. 5A) are found only in S. sexualis (Fig. 65A), S. bifoveolatus (Fig. 87A), S. latitarsis (Fig. 88A) and S. currax (Fig. 113C)
within the Japanese species of Stenus. A morphological problem seems to be that the position of
apicolateral plates are different from one species to another. In S. sexualis the apicolateral plates
are dorsal in position relative to median longitudinal bands, and located at the lateral sides of the
fused expulsion hook (Fig. 65A), while they are located almost posterior to the expulsion hooks
in S. bifoveolatus (Fig. 87A) and S. latitarsis (Fig. 88A). They are dorsal in position relative tothe lateral longitudinal bands in S. currax (Fig. 113C). This may suggest that they are not homologous, but they are simply sclerites that have evolved independently in the groups that possess

18

Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

those sclerites. However, they are here tentatively called “apicolateral plates”, given that they all
are in general positioned at the apicolateral portions of aedeagal median lobe.
Ventral sclerites. There scarcely exist “ventral sclerites” in the endophallus of Stenus,
because median longitudinal bands (ventral bands; Fig. 5A) well develop at its ventral side.
When we observe the endophallus of S. similis group (e.g., S. sedatus, S. weisei, S. cicindeloides,
S. kiesenwetteri), however, we ﬁnd a pair of spindle-shaped or ovoidal sclerites there. They aresclerites that are, for example, designated by “a” in Fig. 102G, which are referred to as “Ausstülpﬁnger” by Puthz (2008: 174). An important point here is that they are not expulsion hooks nor
apicolateral plates, given their ventral positions. They are located at or near the base of expulsion
hooks when seen ventrally, but they are obviously ventral to the expulsion hooks (Fig. 104F).
Furthermore, they are uniquely sculptured as on the surface of inner sac (Puthz, 2008: ﬁgs.
61–63).
Discussion. As secondary derivatives from the surface of inner sac, there seems to exist suchsmall sclerites (or plates) as median sclerite (Fig. 5A), apicolateral plates (Fig. 5A) and aforementioned “ventral sclerites” (e.g., Fig. 104F) in Stenus, in addition to expulsion hooks (which
are commonly found). When judging from location and structure of the sclerites in question, theyeach seem to play a role as sclerite that has an expulsive function, as the expulsion hooks do. In
cases where a Stenus species possesses both expulsion hooks and other expulsive sclerites (suchas apicolateral plates), it may be possible to mention that it is equipped with double expulsion
sclerites, suggesting that the Stenus species has a potential that multiply such sclerites during themorphogenesis of aedeagal median lobe. Interestingly, the endophallic expulsive sclerites(treated here) are sporadically found only in a few species in different species groups of Stenus.
As far as the Japanese Stenus is concerned, the species that all possess median sclerite, apicolateral plates as well as expulsion hooks are S. bifoveolatus and S. latitarsis (S. pallitarsis group)and S. currax (S. bispinus group).
Spermatheca
Spermathecae are highly diverse morphologically in Stenus; and at least three different forms
are recognized (Fig. 7A–C). The basic form of spermatheca is composed of capsule, RT-duct,
spermathecal duct, basal valve, basal sclerotized duct and basal porch (＝ infundibulum; Puthz,
2005: 4), in addition to spermathecal gland (Fig. 7A; Naomi, 2006b). The major characteristics
are as follows: the basal valve is developed just distal to the basal sclerotized duct in usual; andthe RT-duct is usually thicker than spermathecal duct. The spermathecal duct is very short (Fig.
92F), short (Fig. 94C), moderately long (Fig. 121F) to very long (Naomi, 2006b, ﬁg. 27; S.
cephalotes group); and it is loosely (Fig. 121F), moderately (Fig. 123G) or tightly (Fig. 113G)
coiled. The basic form is commonly found in Stenus, including, e.g. S. gibbicollis group, S. pallitarsis group, S. asyura group, S. cephalotes group.
The guttalis-form of spermatheca is composed basically of distal duct (C-shaped; thick),proximal duct (irregularly coiled; more or less thin) and basal porch, in addition to spermathecal
gland (Fig. 7B). The distal duct is composed of capsule, RT-duct and thick distal part of spermathecal duct, while the proximal duct is composed of thin proximal part of spermathecal duct. It is
not understood whether or not the basal valve exists in this guttalis-form. Major characteristic is
as follows: the spermathecal duct is strongly bent just at the boundary between the C-shaped distal duct and proximal duct, where opening of the large (or small) spermathecal gland is located(Fig. 7B). This guttalis-form is found in, e.g. S. gestroi group (Fig. 125C), S. guttalis group (Fig.
126A), S. javanus group (Fig. 66B).

The Steninae of Japan Part 1

Fig. 7.

19

Diagrams of spermatheca with its gland. A, basic form; B, S. guttalis-form; C, S. indubius-form.

The indubius-form of spermatheca is composed of capsule, collum, apical valve, apicalchamber, spermathecal duct and basal porch in addition to spermathecal gland (Fig. 7C); noticehere that the apical valve ( + collum) are virtually homologous to the RT-duct of the basic form

20

Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz(Naomi, 2006a, b) and guttalis-form. The basal valve is probably missing in the indubius-form.
Major characteristics are as follows: the capsule and apical chamber are each large and spherical;
and the duct between the capsule and apical chamber is strongly constricted to form the shortcollum; the apical valve is situated between the base of collum and apical chamber. In S. electristigma (Puthz, 2013, ﬁg. 309), opening of the spermathecal gland is located on the lateral surfaceof the duct a little proximal from the apical chamber. The spermathecal duct is very short, short,moderately long (Fig. 7C) or long. The indubius-form is found in S. indubius group, etc.
Methods of descriptions and illustrations
Japanese species of the S. comma group to S. guttalis group of Steninae are revised taxonomically in this monograph. First, species groups are each brieﬂy characterized by describing
important diagnostic characters, but notice here that the characterization of each species group isoften based mainly on Japanese species in such a way that it may not be applied to species ofother zoogeographical regions in some cases. In order to show speciﬁcally examples of some
important diagnostic characters of a species group, one or more ﬁgures are cited for each of thosediagnostic characters. Second, a key to the Japanese species of each species group is also provided. Third, for each species treated, the afore-mentioned characters are described and illustrated. Regarding photos of the habitus of most species treated, see “Habitus Figures” placed at
the end of this monograph.
Method of descriptions
Items for the description of each species are composed of (1) historical records on the studiesof the Stenine species; (2) “Type material”, Type material examined”, “Other material examined”;(3) “Distribution”; (4) “Redescription” or “Description”; (5) “Biology and Ecology”;(6) “Remarks”; and (7) “Etymology”. Annotations about some items for the descriptions of species are as follows:(1) Historical records on the studies of Stenine species in and after 2001 only are cited atbase; see Hermanʼs (2001) Catalog for the records before 2001. Some important records of studies before 2001 are however cited, because readers can easily understand history of the studies ofa species in question by seeing them.
(2) (a) When information on the type specimens of a species is described based on the typespecimens examined by Puthz and/or by Naomi, then title of the item is “Type material examined”. (b) When information on the type specimens of a species is described based on one ormore previously published papers of the species in question (e.g., Sharp, 1874), then title of theitem is “Type material”. In cases where type material of a species in question comprise
Syntype(s), the number of Syntype(s) are not necessarily clariﬁed in the “Type material”, because
the number is sometimes not described nor traced in the paper, in which the species was ﬁrst
described as new to science and/or later studied.
(7) When (re)describing the Stenine species treated, the item “Etymology” is added in the following three cases: (a) The speciﬁc epithet of a known species is derived from a Japanese term;(b) it is from the name of person; and (c) a speciﬁc epithet is that of a new species.
Method of illustrations
All illustrations are real at base in the section “Descriptions”. This is to say that those illustrations are not schematic nor imaginary by illustrating a combining set of typical conditions ofThe Steninae of Japan Part 1

21

the parts of a taxonomic character illustrated. Thus, there will be (not many but at least a few)
cases where the non-typical conditions are illustrated with respect to some parts of a character ofa species. Such situations are difﬁcult to avoid especially in cases where the species in questionis very rare so that we cannot obtain the Steninae beetle specimens that show an ideal conditionof a character for illustration. In such cases, infraspeciﬁc variations of the character in question
are described and also discussed when needed.
For each species treated, the abdominal secondary modiﬁcations of male, 9th tergum andventrite of male, 10th tergum of male, aedeagus with its endophallic structures including expulsion hooks and basal tubes, (apical part of) gonocoxite and spermatheca are illustrated at base,when male and female specimens of the species are at hand, and also available for illustrations.
Other characters such as 8th ventrite of female, 9th tergum of female and 10th tergum of female
are also illustrated when the illustrations are considered necessary. Notice here that the aedeagus(and thus endophallic structures also) are always illustrated from ventral side, because we canobserve more easily its endophallic structures than from dorsal side. In the caption of a ﬁgure
where an endophallic structure is illustrated from dorsal side, add “(dorsal view)” just after thename of structure which is to be illustrated.
We did our best for carefully illustrating those taxonomic characters that we had better illustrate for species identiﬁcation. However, for simplifying procedure of the time-consuming task ofillustrating the taxonomic characters of so many species as treated in this monograph, we omitted
to illustrate some things or elements of a character illustrated. For the components (i.e., tergum
and ventrite) of abdomen, the pubescence, punctures and microsculptures are not illustrated inmost cases of the species treated. In the 9th ventrite of male, the setae occurring at and near theanterior margin of a pubescent area are illustrated in order for demarcating the pubescent area
(Fig. 4E); and the macrosetae as well as the apicolateral setae are also illustrated (Fig. 4E). Outof the setae on the gonocoxite, the apicolateral setae only are illustrated (Fig. 4F, G), but they are
not done so when they are missing in the specimens illustrated. On the endophallic median longitudinal band, a uniform pattern of small dense dots is found in common. Those dots on the bandare not illustrated at base except for the cases where the distribution of the dots on the bandshows a unique pattern so that it may form the character of a species in question.
History of Taxonomic Studies on the Japanese Steninae
In this section, the history of taxonomic studies on the Japanese Steninae are to be described,
which aims at showing how the Japanese fauna of Steninae have been clariﬁed by the coleopterists after the publication of “The Staphylinidae of Japan” by D. Sharp in 1874. The whole periodof those taxonomic activities from 1874 to the present is divided into the following 3 periods: 1st
period from Sharpʼs (1874, 1889) studies on the Japanese Staphylinidae to the publication of acatalog of the Japanese Staphylinidae (part 1) by Shibata (1976); 2nd period beginning with the
publication of Shibataʼs (1976) catalog to the publication of a list of species of Japanese Steninae
by Puthz & Naomi (2003); and 3rd period beginning with the publication of Puthz & Naomiʼs(2003) list to the present. As far as the descriptive studies are concerned, detailed taxonomic
treatments such as synonymization of species and ﬁrst record of species from Japan are basicallynot mentioned here for saving the space, so that we hope that for further details, readers consult“Remarks” of each species treated in the section “Descriptions”.

22

Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

First period
The Steninae of Japan was ﬁrst studied by Sharp (1874), based on a set of specimens collected in Japan by G. Lewis; and he described the following 15 new species (Stenus tenuipes, S.
alienus, S. verecundus, S. rufescens, S. currax, S. macies, S. lewisius, S. puberulus, S. japonicus,
S. sexualis, S. rugipennis, S. cicideloides [as S. cicindela], S. hirtellus, S. oblitus and S. dissimilis). Sharp (1889) studied again the Steninae of Japan, based on the other set of specimens collected in Japan by G. Lewis; and he described the following 17 new species (S. anthracinus, S.
indagator [as S. lentus], S. distans, S. laborator, S. hirtiventris, S. bicolon, S. sharpi [as S. palpalis], S. latitarsis, S. mysticus, S. indubius, S. cephalotes, S. confertus, S. concinnus, S. mercator, S. sedatus, S. velox and S. ﬂavidulus). The Steninae fauna of Japan (comprising 32 species intotal) was, as described above, ﬁrst clariﬁed at a stretch by David Sharp at the second half of
19th century.
After the Sharpʼs studies, the Steninae of Japan has been only sparsely studied during thenext ca. 80 years by Bernhauer, Cameron, Sawada, Nakane, Puthz, etc. For example, Bernhauer(1907) decribed a new species S. sauteri; and Cameron (1930) described a new species S. kobensis. Nakane (1963a) described a new species S. takara (＝S. gestroi). Puthz (1968b) described
two new Stenus species (S. zimmermanni; and S. zipanguensis [＝S. coronatus zipanguensis]),and ﬁrst discovered S. ruralis Erichson from Japan. Puthz (1973a) described a new species S.
riukiuensis; and Puthz (1974) ﬁrst discovered S. calliceps Bernhauer from Japan. As far as
Dianous is concerned, Sawada (1960) ﬁrst discovered Dianous from Japan and described 3 new
Dianous species.
A standard illustrated encyclopedia of Japanese Coleoptera titled Iconographia Insectorum
Japonicorum Colore naturali edita (Volume II) was published in Japanese in 1963; and Nakane(1963b) redescribed there 9 Stenus species (S. alienus, S. anthracinus, S. rufescens, S. currax, S.
cicindeloides [as S. cicindela], S. mercator, S. ﬂavidulus, S. distans and S. gestroi [as S. takara]and 2 Dianous species (D. japonicus and D. shibatai).
Second period
In 1976, Shibata started to publish a catalog of the Staphylinidae of Japan, which is substantial (and very useful at that time) in surveying the Steninae fauna of Japan. Shibata (1976) published a list of Japanese Steninae in the 1st part of his catalog, in which he actually enumerated
42 species (excepting the species whose names were considered junior synonyms). Given thatseveral Japanese coleopterists started their full-scale studies and ﬁeld surveys for clarifying theJapanese fauna of Staphylinidae (including Steninae), using Shibataʼs catalog, the mid 1970ʼs canbe retrospectively regarded as the dawn of 2nd period for clarifying the Japanese fauna of Steninae.
The Japanese Steninae have been still studied under the traditional framework of Steninae
taxonomy based on 6 subgenera during the 2nd period, where many new Stenine species havebeen described by Puthz, Hromádka, Watanabe and Naomi. Many of the new species describedbelong to S. cephalotes group and S. asyura group, but difﬁculties exist as to the descriptive
studies on these species groups at this period. First, the species which should belong to S. cephalotes group or S. asyura group are broadly put into subgenus Hypostenus, because most of thosespecies have no “tergo-sternal suture” nor “paratergites”; notice here that those species are only
recently classiﬁed into two different species groups (as S. cephalotes group and S. asyura group)by Naomi (2012). To make the matter worse, some species of S. cephalotes group and S. asyuragroup have “tergo-sternal suture” and/or “paratergites” so that those species were simply put into

The Steninae of Japan Part 1

23

Parastenus. In other words, the members of each of these two species groups are artiﬁcially classiﬁed into two different subgenera (Hypostenus and Parastenus).
Main taxonomic activities during the 2nd period are as follows: From the end of 1970ʼs to thebeginning of 1980ʼs, Hromádka has published a series of papers on Japanese Stenus (Hromádka,1979a-d; 1980, 1982), based on a set of specimens collected by K. Sawada. He described 15 Stenus species which belong to various species groups including S. indubius group and S. cephalotes group; and he also redescribed S. testaceopiceus as a Japanese species. Hromádka (1990a,b) also described 2 new Stenus species of S. asyura group from Japan. Puthz (1987) described a
new species, S. shogun; and Puthz (1992) ﬁrst discovered S. kiesenwetteri from Japan. Puthz(1993a,b) described 14 new species, most of which belong to S. cephalotes group and S. asyuragroup. And furthermore, Puthz (2001b-d) described 7 new Stenus species, which belong to S.
humilis group, S. cirrus group, etc.
Since the members of S. humilis group, S. cirrus group, S. asyura group, S. indubius group
and S. cephalotes group comprise many endemic species in Japan, Naomi, together with his coleopterist colleagues, has studied taxonomically the Japanese Steninae since 1986, paying special
emphasis on these groups. As the results, the following number of new species / subspecies aredescribed in those groups: 12 (S. humilis group) by Naomi (1988c, 1990d, 1997f, 1998) andNaomi & Puthz (1994a); 7 (S. cirrus group) by Naomi (1988e, 1997d, 1998b), Naomi & Puthz(1994c, 1996), and see also Naomi (1988f); 27 (S. asyura group) by Naomi (1987, 1988 g,
1989b,c, 1990a,b,d, 1997c, 1998b) and Naomi & Puthz (1994b, 1996); 4 (S. indubius group) by
Naomi (1987, 1997c), Naomi & Takeda (1991) and Naomi & Puthz (1996); and 38 (S. cephalotes group) by Naomi (1987, 1988e, 1989b-d, 1990a,b, 1997b, 1998a,b), Naomi & Nomura(1990), Naomi & Puthz (1993, 1994b,c) and see also Naomi (1997a). Other descriptive studies
by Naomi are as follows: 2 new species of S. gibbicollis group (Naomi, 1988c); 3 new species of
S. claviconis group (Naomi, 1988d, 1990d); 1 new species of S. crassus group (Naomi, 1989a); 1
new species of S. pallitarsis group (Naomi, 1988b); 1 new species of S. similis group (Naomi,
1997b; with Puthz); and 1 new species of S. coelogaster (Naomi, 1990c).
As far as Dianous is concerned, Watanabe (1984) described 1 new species (D. coerulescensgroup). From Nansei Islands, Naomi (1988a) described 1 new species of D. chinensis group, andNaomi (1997e) described 1 new species of D. calceatus group.
A standard illustrated encyclopedia of Japanese Coleoptera titeled The Coleoptera of Japanin Color was published in Japanese in 1985; and Watanabe (1985) redescribed there 14 Stenus
species (S. alienus, S. tenuipes, S. anthracinus, S. kobensis, S. macies, S. distans, S. lewisius, S.
melanarius (as S. melanarius vercundus), S. zimmermanni, S. cicindeloides, S. mercator, S. ﬂavidulus, S. rufescens, and S. rugipennis, and 2 Dianous species (D. amamiensis and D. shibatai).
Third period
Third period will be considered the period where, in addition to the continued descriptive
studies, staphylinists have been successful in illuminating the outline of the Japanese fauna of
Steninae, which comprise 34 species groups, as listed below. As far as the studies on the level of
species group is concerned, S. asyura group was ﬁrst characterized by using the structure of
aedeagus, etc., and S. rufescens group was synonymized with S. cephalotes group by Naomi(2012). S. macies was ﬁrst recognized as belonging to S. seminiger group in this monograph.
Main descriptive studies during the 3rd period have been conducted by Puthz, Naomi,
Nomura, Watanabe, Ito, Shimada and Kamezawa, which are summarized as follows: Puthz(2003b) described 2 new Stenus species: S. alter (S. cephalotes group) and S. hayashii (S. asyura

24Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

group). Naomi, together with his colleagues, continues to have studied Japanese Steninae andhave described the following number of new Stenus species: 1 (S. comma group) by Naomi &Watanabe (2015); 1 (S. clavicornis group) by Naomi & Ito (2015b); 6 (S. humilis group) by
Naomi (2004c), Naomi & Shimada (2008) and Naomi & Ito (2014); 1 (S. incanus group) by
Naomi & Nomura (2015a); 2 (S. abdominalis group) by Naomi (2015a) and Naomi & Watanabe(2015); 7 (S. cirrus group) by Naomi (2004d, 2015b), Naomi & Ito (2015a) and Naomi &Nomura (2015a); 31 (S. asyura group) by Naomi (2004a,b,e, 2010a, 2015a,c), Naomi & Nomura(2015b), Naomi, Nomura & Kamezawa (2015), and Naomi & Watanabe (2015); 15 (S. indubius
group) by Naomi (2006b, 2015b) with coauthor of Puthz for several new species; and 31 (S.
cephalotes group) by Naomi (2006b, 2007, 2011a, 2012, 2015a,c), Naomi & Shimada (2008),
Naomi & Nomura (2015b), Naomi, Nomura & Kamezawa (2015), and Naomi & Watanabe(2015).
Based on the afore-mentioned and related studies on the Japanese Steninae, two lists of thespecies of Japanese Steninae were published. Puthz & Naomi (2003) published a preliminary listof the species of Japanese Steninae (comprising 213 species: 9 Dianous species and 204 Stenus
species) in the Newsletter of the Staphylinidological Society of Japan (No. 20). Although it is
only a small 3-paged list, its publication seems to have had a heuristic inﬂuence on the analyticalstudies of Japanese Steninae fauna by staphylinists, because a subclade as S. asyura group(which presently comprises 70 species) was ﬁrst vaguely but adequately recognized between S.
indubius group and S. cephalotes group in the list. This list was lately published as a revised version by Naomi & Puthz (2013), in which 258 species (9 Dianous species and 249 Stenus species)
are listed.
Steninae fauna of Japan
By the afore-mentioned taxonomic studies and relevant activities (including ﬁeld researches)on Japanese Steninae, beginning with the studies by Sharp (1874) to the present, the Steninae
fauna of Japan is presently recognized as consisting of Dianous (3 species groups and 6 species)
and Stenus (347 species and 34 species groups), the species groups of which are listed below,
together with the number of species. Species groups of Stenus not treated in this monograph arebracketed. Note here the following two things. First, the number of total species 347 include thenumber of undescribed species (26) and the number of several (described) subspecies which arecomparable for the level of species (Naomi, unpublished). Second, S. asyura group and S. cephalotes group each may be subdivided into two or more species groups when they are further studied in detail.
Genus Dianous Leach, 1819
Species group of D. calceatus Puthz: 1 species
Species group of D. chinensis Bernhauer: 1 species
Species group of D. coerulescens Gyllenhal: 4 species
Genus Stenus Lateille, 1797
Species group of S. comma LeConte: 7 species
Species group of S. seminiger Champion: 1 species
Species group of S. clavicornis (Scopoli): 15 species
Species group of S. humilis Erichson: 27 species

The Steninae of Japan Part 1

25

Species group of S. circularis (Gravenhorst): 1 species
Species group of S. javanus Cameron: 1 species
Species group of S. palposus Zetterstedt: 1 species
Species group of S. melanarius Stephens: 2 species
Species group of S. canaliculatus Gyllenhal: 2 species
Species group of S. incanus Erichson: 2 species
Species group of S. gibbicollis Sahlberg: 5 species
Species group of S. crassus Stephens: 5 species
Species group of S. opticus Gravenhorst: 1 species
Species group of S. pubescens Stephens: 1 species
Species group of S. pallitarsis Stephens: 3 species
Species group of S. ﬂavipes Stephens: 3 species
Species group of S. piliferus Motschulsky: 5 species
Species group of S. rorellus Fauvel: 2 species
Species group of S. similis (Herbst): 6 species
Species group of S. cylindricollis Boheman: 3 species
Species group of S. coelogaster Champion: 1 species
Species group of S. wasmanni Fauvel: 1 species
Species group of S. pulcher Motschulsky: 1 species
Species group of S. bispinus Motschulsky: 1 species
Species group of S. alpicola Fauvel: 2 species
Species group of S. virgula Fauvel: 1 species
Species group of S. abdominalis Fauvel: 8 species
Species group of S. sharpi Bernhauer et Schubert: 1 species
Species group of S. gestroi Fauvel: 1 species
Species group of S. guttalis Fauvel: 1 species(Species group of S. cirrus Benick: 17 speces)(Species group of S. asyura Naomi: 70 species incl. 1 undescribed species)(Species group of S. indubius Sharp: 27 species)(Species group of S. cephalotes Sharp: 116 species (incl. 25 undescribed species)
Descriptions
Subfamily Steninae Macleay, 1825
Genus Dianous Leach, 1819
Dianous Leach, 1819: 173 (type species: Stenus coerulescens Gyllenhal, ﬁxed by originaldescription and monotypy).
Diagnostic characters. Adults: Eyes each not occupying the whole lateral side of head (Fig.
127A, B); head basically with its post ocular area, which is strongly narrowed posteriorly (Fig.
127A, B); 9th ventrite (Fig. 8A) and gonocoxites (Fig. 8B) each furnished with a pair of very
long apicolateral tufts of setae (Ganglbauer, 1895; Puthz, 1981a); spermatheca not observable.
Larvae: Mala longer than 1st segment of maxillary palpus; ligula densely pubescent (Kasule,
1966; Puthz, 1981a).
Taxonomy. The genus Dianous (comprising 262 species; Puthz, 2016a) is tentatively divided
into two phylogenetic groups (Puthz, 2000, 2015a, 2016a): Group I (with 76 species) is charac-

26

Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

terized by the frons concave between eyes, with its median area not elevated, and the eyes being
very large so that the temples are very short or nearly missing, while group II (with 186 species)
is characterized by the frons with its median area elevated and also with two lateral, longitudinalfurrows, and the eyes being mostly smaller than in group I so that the temples are distinctly
found. The group II is furthermore divided into 9 species groups (D. calceatus group; D. uniformis group; D. luteoguttatus group; D. bimaculatus group; D. lobigerus group; D. aereus group;
D. chinensis group; D. ocellatus group; and D coerulescens group) and incertae sedis (nearDianous group I) (Puthz, 2016a).
As for the Japanese fauna of Dianous, Naomi (1988a) created 3 species groups of Dianous(i.e., D. yoshidai group; D. amamiensis group; and D. japonicus group). However, following thephylogenetic system of Dianous names created by Puthz (2000), the D. yoshidai group is here
actually considered a synomyn of the D. chinensis group, while the D. japonicus group and D.
amamiensis group are considered synonyms of the D. coerulescens group.
Morphology. The morphology of Dianous has been adequately described in Puthz (1981a,
2000); see these papers regarding the detailed morphology of this genus. Only small remarks arehere added on the morphological evolution of Dianous.
When considering Dianous from the morphological viewpoint, it is very interesting to seethat it shows a heterobathmic (or mosaic) evolution of morphological characters. Namely, theDianous seems to be rather apomorphic in having the specialized or advanced conditions ofsome characters: The tarsi with tarsal shoes (Puthz, 2000, ﬁgs. 1–5), the apicolateral tufts of setaevery long in 9th ventrite of male (Fig. 8A) and also in gonocoxites of female (Fig. 8B), the endophallic basal tube often with its basal room very large (Puthz, 2000, ﬁgs. 39, 40, 44–46), etc. On
the other hand, the Dianous seems to show primitive conditions in some characters, when compared with Stenus. For example, the eyes are smaller and less prominent laterally, which do not
occupy the whole lateral side of head (Ganglbauer, 1895: 548). The aedeagi of Dianous are much
more uniform both in external and endophallic structures (Puthz, 2000: 422), when comparedwith Stenus. Furthermore, some Dianous species have the gonocoxites which each distinctly
comprise the proxomal and distal sclerites and stylus (Figs. 8B, 9E).
Since the Dianous seems to be phylogenetically positioned within the genus Stenus (Koerner
et al., 2013), it seems most reasonable to hypothesize that those primitive structures have reappearred in Dianous by reversal evolution to the extant species (in which those primitive ones
are found), as do the short (i.e., primitive) conditions of prementum in Dianous-labium.
Biology and Ecology. The Dianous species are basically hygrobionts (Puthz, 1981a, 2000).
The Dianous beetles live in the vicinity of the headwaters of mountain streams, where the volume of water is less and the fall is steeper, so that the sprey is sprinkled over the mossy boulders(Champion, 1919). The beetles (of D. robustus Cameron, 1924; India) cling to and move over a
vertical rock face down which runs a steady ﬁlm of water; and some beetles stand although thewater is up to the knees, or a few ones are seen totally submerged (de Rougemont, 1985: 139). In
some cases, however, the Dianous beetles live in different habitats (Puthz, 2000: 426). For example, D. corticicola Puthz, 1972d (Vietnam) was found under the bark of trees; D. concretus
Puthz, 1988a (Malaysia) was found in dead leaves and dry mosses in open forests (Puthz,
1988a); and D. sucininotatus Puthz, 2000, etc. (Taiwan) were found in wet mosses grown on rotten woods, and also in debris in forests, etc.
The Japanese species of Dianous all are basically hygrobionts, also; and the beetles basicallyinhabit wet stones with mosses located in or near the mountain torrents. D. shibatai is a hygrobiont, but the beetles of this species are also found under humid dead leaves (Puthz, 1981a), on

The Steninae of Japan Part 1

27

semi-arid sandy lot and humid mountainous roads in natural forests.
Key to the Japanese species of Dianous
1(2) First segment of metatarsus distinctly longer than the following three segments combined....................................................................................................................... D. moritai Naomi
2(1) First segment of metatarsus about as long as or shorter than the following three segments
combined.
3(6) Head distinctly narrower than elytra.
4(5) Antennae and legs yellowish brown to reddish brown; aedeagal median lobe bilobed (Fig.
9B) ............................................................................................................... D. yoshidai Naomi
5(4) Antennae and legs black; aedeagal median lobe pointed apically with a small apicomedianprojection (Fig. 10A) ............................................................................ D. amamiensis Sawada
6(3) Head not narrower than elytra.
7(10) Head about as wide as elytra; lateroventrites wider, ventromesial in position; 8th ventrite ofmale posteromedially with an arcuate emargination.
8(9) Ninth ventrite of male with apicolateral teeth short, bluntly pointed (Fig. 11B); aedeagal
median lobe with apical sclerotized area triangular, acutely pointed posteromedially (Fig.
11D) .................................................................................................... D. iwakisanus Watanabe
9(8) Ninth ventrite of male without (distinct) apicolateral teeth (Fig. 12G); aedeagal median lobe
with apical sclerotized area various in shape, not very acutely pointed (Fig. 12A–E)..................................................................................................................D. japonicus Sawada
10(7) Head distinctly wider than elytra; lateroventrites narrower, dorsomesial in position;
8th ventrite of male posteromedially with an V-shaped emargination (Fig. 13F).................................................................................................................. D. shibatai Sawada
Species group of D. calceatus Puthz
D. calceatus group consists of 1 species in Japan. Diagnostic characters are as follows: Eyes
relatively small; temple at least half the length of eye; tarsi each mostly with tarsal shoe which
comprises willow-leaf-like setae (Puthz, 2000, ﬁgs. 1–3), 1st metatarsomere longer than two tofour metatarsomeres combined, 4th metatarsomere simple or asymmetrical; 8th ventrite offemale entire (Fig. 8E) or emarginate apically; and aedeagal median lobe usually almost conically narrowed apically (Fig. 8C) (Puthz, 2000).
Dianous moritai Naomi(Figs. 8A–G, 127A)
Dianous moritai Naomi, 1997e: 1; Herman, 2001: 2025; Naomi & Puthz, 2013: 137.
Dianous uedai Naomi, 2010b: 41; Naomi & Puthz, 2013: 137. New synonym.
Type material examined. Holotype of D. moritai: ♀ (CBM), Sumiyo River, Nishinakama,
Amami Is., Nansei Isls., 7. v. 1981, S. Morita leg. Paratypes of D. uedai Naomi, 1 ♂2 ♀ (cN), 1 ♂
(cP), Sumiyo-mura, Amami Is., Kagoshima Pref., 28. v. 2004, K. Takanashi leg.
Distribution. Japan (Nansei Isls.: Amami Is.).
Redescription. Male and female: Macropterous; body large, 7.6–8.0 mm (fore body 4.0–4.3

28

Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

Fig. 8. Dianous moritai Naomi (Sumiyo, Amami Is.). A, 9th ventrite of male; B, gonocoxites; C, aedeagus; D,
8th ventrite of male; E, 8th ventrite of female; F, 9th and 10th terga of male; G, 9th and 10th terga of female.
Scale 1: 0.25 mm for A, B, D, E; scale 2: 0.3 mm for C; scale 3: 0.25 mm for F, G.

The Steninae of Japan Part 129mm) in length, rather slender, moderately to weakly shining. Head black, partially with varicolored (purple to dark blue) reﬂection; labrum black, with reddish anterior margin; antennae black
through dark brown to reddish brown; maxillary palpi dark reddish brown to reddish brown; pronotum black but entirely with metallic bluish tinge; elytra black; legs black to dark brown, withapical tarsal segments yellowish brown to reddish brown; abdomen with 3rd to 6th lateroventrites black, 3rd to 8th terga black but entirely with metallic bluish tinge. Head large, broader
than long, strongly narrowed posteriorly behind eyes; eyes relatively small but well convex, a little longer than postocular areas; clypeofrontal area broad, moderately convex at middle; interocular area rather broad, very weakly concave, with antennal tubercles short but distinct, dorsal
tentorial pits distinct, located just behind antennal tubercles; postocular areas gently rounded.
Punctures on head round, very dense, small, regular, but punctures very sparse on the medianpart of clypeofrontal area; interstices between punctures distinctly microsculptured on anterior
part of head, indistinctly or faintly so on posterior part of head. Antennae very slender, extending
posteriorly beyond half of elytra. Pronotum well convex above, longer than broad, with a thinline running along each of anterior and posterior margins of pronotum; surface with a pair oflarge foveae at sides of central part, without median longitudinal line; punctures extremely ﬁne,very sparse; interstices between punctures minutely, evenly microsculptured. Mesoscutellum
almost triangular in shape, covered densely with minute setiferous punctures. Elytra large, elongate, distinctly longer than wide, moderately convex, gently rounded laterally; surface somewhat
uneven, densely covered with very ﬁne punctures; interstices between punctures moderately
shining, devoid of microsculpture or obsoletely microsculptured. Legs long, slender; 4th tarsomere not bilobed, with its dorsal surface covered with yellowish white, long setae. Abdomen
elongate; terga each well convex right and left; 3rd tergum with punctures very ﬁne and sparse,
their diameter distinctly smaller than interstice, interstices between punctures with faint reticulate
microsculpture; punctures becoming denser posteriorly from 3rd to 7th terga; punctures on 8th
tergum, however, distinctly larger than those on 7th but rather sparse. Lateroventrites almost horizontal in position, moderate in width, densely punctate.
Male: Seventh ventrite posteromedially with a shallow, arcuate emargination; 8th ventrite(Fig. 8D) posteromedially with a shallow, relatively broad emargination; 9th tergum (Fig. 8F)
elongate, with ventral apophyses short; 9th ventrite (Fig. 8A) with apicolateral teeth robust,large, pointed, with apicolateral setae very long; 10th tergum (Fig. 8F) posteromedially with avery shallow, arcuate emargination, posterior margin densely furnished with a line of yellowish,
short thick setae. Aedeagal median lobe (Fig. 8C) almost elongate-elliptical, weakly sinuate
around apicolateral corners, covered very sparsely with very minute setae at the apicalmost part,with a minute apicomedian projection. Endophallus (Fig. 8C) with median longitudinal bands
rather short, thin; lateral longitudinal bands very short, thin; basal tube very large, composed ofpaired Y-shaped rods. Parameres (Fig. 8C) slender, thin, extending posteriorly much beyond apexof median lobe; stem furnished sparsely with several setae; apical area not distinctly differentiated, apicomesially with 8 to 9 setae of moderate length.
Female: Eighth ventrite (Fig.8E) entire; 9th tergum (Fig. 8G) almost truncate posteriorly,
without ventral struts; 9th gonocoxites (Fig. 8B) each composed of proximal and distal sclerites;
distal sclerite narrowed apically behind the middle, bluntly pointed, furnished with apicolateral
setae very long; 10th tergum (Fig. 8G) with posterior margin almost straight or very weakly
bisinuate, densely furnished with a line of yellowish, short thick setae. Spermatheca not observable.
Biology and ecology. Dianous moritai is distributed only in the mountainous regions of

30

Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

Amami Is. The beetles inhabit wet stones with mosses located in or near the mountain torrents.
Remarks. Dianous moritai is a very rare, conspicuous and large species. The holotype specimen of D. uedai seems to be a teneral individual of D. moritai; and thus D. uedai Naomi be
newly placed in synonymy with D. moritai Naomi. D. moritai is closely allied to D. arachnipes
Puthz, 1971b, but this species is separable from the latter by the body black with pronotum andabdomen tinged with bluish metallic luster, the head with interocular area less strongly convex,
the eyes less strongly convex, the pronotum smoothly convex dorsally, the elytra with surface
weakly uneven, the 8th ventrite of female entire (Fig. 8E), the aedeagal median lobe more slender, with its posterior half less strongly narrowed posteriorly (Fig. 8C), the endophallic basal
tube very large, composed of a pair of Y-shaped rods (Fig. 8C), and the median longitudinalbands longer, broader (Fig. 8C).
Etymology. This species is named in honour of Mr. S. Morita (Tokyo) who collected theholotype specimen.
Species group of D. chinensis Bernhauer
D. chinensis group consists of 1 species in Japan. Diagnostic characters are as follows: Eyes
large; temple less than half the length of eye; legs with 4th tarsomere simple or moderately
bilobed; 9th ventrite of male serrate or acute apicolaterally (Fig. 9C); aedeagal median lobe
broad apically or broadly bifurcate apically (Fig. 9B); paramere with two sets of setae of different length (Fig. 9B); and 8th ventrite of female with apicomedial projection rounded or obtusely
pointed (Fig. 9F) (Puthz, 2000).
Dianous yoshidai Naomi(Figs. 9A–F, 127B)
Dianous yoshidai Naomi, 1988a: 51; Herman, 2001: 2033; Naomi & Puthz, 2013: 137.
Type material examined. Holotype: ♀ (KUF), Kanpira fall, Iriomote Is., Okinawa Pref., 12.
iv. 1986, M. Yoshida leg.
Other material examined. [NANSEI-ISLS]: 2 ♂1 ♀, Kampira-fall, Iriomote Is., Okinawa
Pref., 8. iii. 2002, Y. Hirano leg.; 1 ♂1 ♀, same locality, 16. iii. 1997, K. Toyoda leg.; 3 ♂3 ♀,same locality, 23. iii. 1998, M. Maruyama leg.; 3 ♂1 ♀, Ootomi-rindo, Iriomote Is., Okinawa
Pref., 27. iii. 1994, M. Kimura leg.; 1 ♂2 ♀, Nishi-funatsuki, Ootomi-rindo, Iriomote Is., Okinawa Pref., 28. iii. 1999, T. Ito & Ohkawa leg.; 2 ♀, Nakamagawa-rindo, Iriomote Is., Okinawa
Pref., 29. xii. 1997, Y. Kurosa leg.
Distribution. Japan (Nansei Isls: Iriomote Is.).
Redescription. Male and female: Macropterous; body 4.6–5.8 mm (fore body 2.7–2.9 mm) in
length, moderately shining, with large elytra. Body entirely black, with dark blue reﬂection;antennae black, with apical segments dark red; mouth parts dark red except for reddish brown
mandibles; legs black with dark blue reﬂection, but tibiae dark red. Head relatively small,strongly narrowed posteriorly behind eyes; eyes well convex laterally; interocular area transverse, not concave, with a pair of distinct longitudinal sulci; surface with setiferous puncturesround to elliptical, dense, distinct. Labrum transverse, with anterior margin rounded. Antennae
long, very slender, with sparse setae. Pronotum well convex dorsally; surface with a shallow,
indistinct U-shaped depression behind the middle; punctures round, various in size, distinct,

The Steninae of Japan Part 1

Fig. 9. Dianous yoshidai Naomi (Ohtomi, Iriomote Is.). A, 9th and 10th terga of male; B, aedeagus; C, 9th ventrite of male; D, 7th and 8th ventrites of male; E, posterior parts of gonocoxites; F, apex of 8th ventrite offemale. Scale 1: 0.2 mm for A, B; scale 2: 0.2 mm for C, E; scale 3: 0.3 mm for D, F.

31

32

Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

sometimes several punctures fused. Elytra well developed; surface almost even, with punctures
very dense, various in size and shape, sometimes rugous; punctures on each elytron running fromanteromesial to mediolateral direction before the middle, while behind the middle they run frommediolateral to posteromesial direction. Legs moderately long; 4th tarsomere weakly bilobed.
Abdomen uniformly narrowed posteriorly; terga each well convex right and left; punctures ﬁne,distinct, nearly regular from 3rd to 8th segments throughout, but punctures on the 3rd a little
sparser than on the 8th. Lateroventrites ventromesial in position, wide, covered regularly with
ﬁne punctures.
Male: Sixth ventrite posteromedially with a ﬂat area which is very weakly emarginate; 7thventrite (Fig. 9D) posteromedially with a semicircular depression which is very shallowly emarginate; 8th ventrite (Fig. 9D) posteromedially with a large, deep emargination; 9th tergum (Fig.
9A) elongate, with ventral apophyses relatively short; 9th ventrite (Fig. 9C) irregularly serrate
posteriorly, with apicolateral teeth robust, pointed, apicolateral setae very long; 10th tergum (Fig.
9A) posteromedially with a very shallow emargination. Aedeagal median lobe (Fig. 9B) broadestnear the middle, weakly constricted before the bilobed apical part, each apical lobe rounded apically. Endophallic median longitudinal bands (Fig. 9B) rather short, thin; expulsion hooks atrophied, fused to form a small T-shaped structure; basal tube stored in inner sac that is densely covered with very ﬁne denticles, basal room very small, with weak, distinct basal constriction, tube
body rod-like, gradually broadened apically. Parameres (Fig. 9B) moderately incurved apically,
gradually broadened toward apex which is rounded; each paramere furnished with 8 setae ofmoderate length on apical and apicodorsal margins, and also with 5 or more setae on basiventral
margin of apical area.
Female: Eighth ventrite (Fig. 9F) narrowed near the apex to form blunt apicolateral corners,
with apicomedian projection relatively large; gonocoxal distal sclerites (Fig. 9E) each elongate,
narrowed apically behind the apical 1/3, pointed, with apicolateral setae very long, stylus (Fig.
9E) very small, tuberculiform, with a long seta. Spermatheca not observable.
Biology and ecology. Dianous yoshidai is distributed only in the plains and mountainous
regions of Iriomote Is. The beetles inhabit wet stones with mosses located in or near the mountain torrents.
Remarks. Given the structural similarity that their aedeagi share, Dianous yoshidai is closely
allied to D. atrocyaneus Puthz, 2000 from Taiwan, but this species is separable from the latter by
the body smaller, the 8th ventrite of male with a deeper emargination (Fig. 9D), the aedeagal
median lobe a little broader apically (Fig. 9B), the endophallic median longitudinal bands narrower (Fig. 9B), and the expulsion hook distinctly shorter (Fig. 9B).
Etymology. This species is named in honour of Mr. Mutuo Yoshida, an entomologist inJapan.
Species group of D. coerulescens Gyllenhal
D. coerulescens group consists of 4 species in Japan. Diagnostic characters are as follows:
Eyes large; temples less than half the length of eyes; legs with 4th tarsomere simple or bilobed;
9th ventrite of male rounded, serrate apicolaterally (Fig. 10C) or acute apicolaterally (Fig. 11B);
aedeagal median lobe with apical part more or less triangular in shape (Fig. 11D); paramere apicomesially with a group of setae (Fig. 11D); 8th ventrite of female rounded, angulate (Fig. 10F)
or slightly projecting apicomedially (Puthz, 2000).

The Steninae of Japan Part 1

33

Dianous amamiensis Sawada(Figs. 10A–F, 127 C)
Dianous amamiensis Sawada, 1960: 11; Herman, 2001: 2011; Naomi & Puthz, 2013: 137.
Type material. Holotype: ♀ (cSa), type locality: Koniya, Amami Is., Kagoshima Pref.
Other material examined. [NANSEI-ISLS]: 6 ♂3 ♀, Naze C., Amami Is., Kagoshima Pref.,19. iv. 1993, R. Kuranishi leg.; 2 ♂, Koniya, Amami Is., Kagoshima Pref., 27. iii. 1979, Y. Tsuda
leg.; 1 ♀, Materia fall, Yamato, Amami Is., Kagoshima Pref., 19. iii. 1999, T. Ito & Ohkawa leg.;1 ♀, Yamatohama, Amami Is., Kagoshima Pref., 24. iii. 1978, S. Naomi leg.; 4 ♂4 ♀, Akirigami
River, Toku Is., Kagoshima Pref., 14. iv. 1996, R. Kuranishi leg.; 1 ♂, Kametoku, Toku Is.,
Kagoshima Pref., 8. iv. 1998, M. Kimura leg.; 1 ♂, Tete, Toku Is., Kagoshima Pref., 4. v. 1988, S.
Nomura leg.
Distribution. Japan (Nansei Isls.: Amami Is., Toku Is.).
Redescription. Male and female: Macropterous; body 4.5–4.6 mm (fore body 2.6–2.7 mm) in
length, moderately shining, with large elytra. Body entirely black but elytra sometimes with apair of vague, yellowish spots; pronotum and elytra often with dark blue coppery reﬂection;mouth parts (except for black labrum), antennae and legs yellowish brown to reddish brown.
Head relatively small, narrowed posteriorly behind eyes; eyes well convex laterally; interoculararea not concave but a little higher in level than eyes at posteromedian swollen part, with a pairof distinct longitudinal sulci; surface with setiferous punctures round to elliptical, moderately
dense (but sometimes very dense), distinct. Labrum very transverse. Antennae long, very slender,
with sparse setae. Pronotum well convex above; surface indistinctly with a large, shallow
V-shaped depression behind the middle, and with a small, elongate fovea a little behind the central area of pronotum; punctures dense, subrugous. Elytra well developed; surface almost even,with punctures rugous, various in shape, density and size; punctures on each elytron runningfrom anteromesial to mediolateral direction before the middle, while behind the middle they run
from mediolateral to posteromesial direction. Legs moderately long; 4th tarsomere moderately
bilobed. Abdomen narrowed posteriorly, well convex above; punctures very ﬁne, regular, distinct
from 3rd to 8th segments throughout, but punctures on 3rd a little larger than on 8th. Lateroventrites ventromesial in position, becoming distinctly narrower posteriorly from 3rd to 6th segments, covered regularly with ﬁne, distinct punctures.
Male: Seventh ventrite posteromedially with a ﬂat area which is very weakly emarginate; 8thventrite (Fig. 10E) posteromedially with a large, broad emargination; 9th tergum (Fig. 10B) elongate, with ventral apophyses short; 9th ventrite (Fig. 10C) rounded apicolaterally, very weakly
serrate posteriorly, with apicolateral setae very long; 10th tergum (Fig. 10B) transverse, posteromedially with a very shallow emargination. Aedeagal median lobe (Fig. 10A) rounded at apicolateral corners, pointed apically with a small apicomedian projection; apical sclerotized area withvery short setae along marginal areas. Endophallus (Fig. 10A) with median longitudinal bands
short; expulsion hooks fused to form a small Y-shaped sclerite; basal tube simple, baculiform,
comprising two thin shafts when seen ventrally. Parameres (Fig. 10A) thin; stem mesially with afew short setae; apical area weakly swollen mesially, furnished apicomesially with 14 to 15 setaeof moderate length.
Female: Eighth ventrite (Fig. 10F) bluntly pointed apicomedially; gonocoxal distal sclerite(Fig. 10D) rounded apicolaterally, hardly or very minutely serrate posteriorly, with apicolateral
setae very long; stylus missing. Spermatheca not observable.

34

Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

Fig. 10. Dianous amamiensis Sawada (A, C, E, Akirigami, Toku Is.; B, D, F, Naze, Amami Is.). A, aedeagus; B,
9th and 10th terga of male; C, 9th ventrite of male; D, apices of gonocoxites; E, apex of 8th ventrite of male;F, apex of 8th ventrite of female. Scale: 0.2 mm.

The Steninae of Japan Part 1

35

Biology and ecology. Dianous amamiensis is distributed only in the plains and mountainous
regions of Amami and Toku Isls.; it is here ﬁrst reported from Toku Is. The beetles inhabit wetstones with mosses located in or near the mountain torrents.
Remarks. Dianous amamiensis is allied to D. suciniguttatus Puthz, 2000, but this species isseparable from the latter by the body smaller (4.5–4.6 mm), the lateroventrites broader, covered
with denser punctures, the aedeagal median lobe narrower in apical half, pointed apically with asmall protuberance (Fig. 3A), and the parameres furnished apically with shorter setae (Fig. 10A).
Dianous iwakisanus Watanabe(Fig. 11A–E)
Dianous iwakisanus Watanabe, 1984: 134; Herman, 2001: 2022; Naomi & Puthz, 2013: 137.
Type material examined. Holotype: ♂ (TUAA), labelled “[HOLOTYPE] Dianous iwakisanus
Y. Watanabe, 1984 / (Mt. Iwaki) Aomori, Japan, 26. viii. 1969, Coll. T. Kiuti”.
Distribution. Japan (Honshu: Aomori Pref.).
Redescription. Male: Brachypterous; body 4.3–4.8 mm (fore body 2.2–2.5 mm) in length,
moderately shining. Head and abdomen black; prothorax and elytra dark bronze; antennae black
but 9th to 11th segments red to reddish brown; labrum and legs black. Head large, with a pair ofnarrow, distinct longitudinal depressions; punctures round, relatively dense. Pronotum with surface uneven, with a large, shallow, indistinct V-shaped depression; punctures round, dense, somewhat irregular. Elytra with sutural area weakly elevated; punctures round, dense, irregular, sometimes subrugous. Legs moderately long; 4th tarsomere weakly bilobed. Abdomen with terga wellconvex above; punctures very small and sparse. Lateroventrites ventromesial in position, wide,
covered with small, sparse and setiferous punctures.
Seventh ventrite posteromedially with a ﬂat area which is very weakly, arcuately emarginate;
8th ventrite (Fig. 11A) posteromedially with a very large, broad emargination; 9th tergum (Fig.
11C) with ventral apophyses short; 9th ventrite (Fig. 11B) not serrate and very weakly rounded
posteriorly, with apicolateral teeth wide, short, pointed, apicolateral setae very long; 10th tergum(Fig. 11C) truncate posteriorly. Aedeagal median lobe (Fig. 11D) almost elongate-ovoidal
basally, narrowed apically, angulate apicolaterally, very acutely pointed at apex, furnished withseveral setae along apicolateral margins, with apical sclerotized area triangular in shape, sporadically covered with pores. Endophallus with median longitudinal bands invisible; expulsion hooks
missing; inner sac partially with thin, sclerotized rims (Fig. 11E); basal tube (Fig. 11E) elongate,sclerotized except for submembranous median part, almost baculiform with its apical part
weakly swollen laterally. Parameres (Fig. 11D) elongate, extending posteriorly much beyond
apex of median lobe; stem weakly sinuate mesially, and also mesially with several setae; apicalarea furnished mesially with dense setae.
Female: Unknown.
Biology and ecology. Dianous iwakisanus is presently known only from the mountainous
regions of Mt. Iwaki located at the most northern part of Honshu. The beetles inhabit wet stones
with mosses located in or near the mountain torrents.
Remarks. Dianous iwakisanus is closely allied to D. japonicus, but this species is separablefrom the latter by the 9th ventrite of male very weakly rounded posteriorly, with apicolateral
setae shorter (Fig. 11B); the aedeagal median lobe more strongly pointed apically (Fig. 11D); theendophallic basal tube well sclerotized except for the submembranous median part (Fig. 11E);

36

Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

Fig. 11. Dianous iwakisanus Watanabe (Iwaki, Aomori). A, apex of 8th ventrite of male; B, apex of 9th ventriteof male; C, 9th and 10th terga of male; D, aedeagus; E, endophallic structures. Scale 1: 0.2 mm for D, 0.1 mm
for E; scale 2: 0.2 mm for A–C.

and the paramere longer (Fig. 11D).

The Steninae of Japan Part 1

37

Dianous japonicus Sawada(Figs. 12A–I, 127D)
Dianous japonicus Sawada, 1960: 9; Herman, 2001: 2022; Naomi & Puthz, 2013: 137.
Dianous gongen Watanabe, 1984: 131; Herman, 2001: 2020; Naomi & Puthz, 2013: 137.
Dianous morimotoi Naomi, 1988a: 48; Naomi, 2011b: 65; Herman, 2001: 2025.
Dianous septentrionalis Naomi, 1988a: 50; Herman, 2001: 2022.
Dianous viridicatus Naomi, 1997e: 3; Herman, 2001: 2032; Naomi & Puthz, 2013: 137. New
synonym.
Type material. Holotype: ♀ (cSa), type locality: Tani, V. Jinryo, Tokushima Pref.
Type material examined. Holotype of D. gongen: ♂ (NMNST) labelled [HOLOTYPE]
Dianous gongen Y. Watanabe, 1984 / Mt. Ushiroeboshi, Mt. Zao, Miyagi Pref., 10. vi. 1976,
Coll. Y. Watanabe. Allotype of D. gongen: ♀ (NMNST) labelled [ALLOTYPE] Dianous gongen
Y. Watanabe, 1984 / Mt. Ushiroeboshi, Mt. Zao, Miyagi Pref., 10. vi. 1976, Coll. Y. Watanabe.
Paratypes of D. septentrionalis: 2 ♂6 ♀ (cN), Kawara-bo, Mt. Hayachine, Iwate Pref., 22–24. vi.
1980, S. Naomi leg.; 12 ♂5 ♀ (cN), Zenjin, Mt. Chokai, Akita Pref., 19–20. vi. 1980, S. Naomi
leg.
Other material examined. [HONSHU]: 1 ♀, Kita-hakkoda, Aomori C., Aomori Pref., 28. v.
1990, T. Shimizu leg.; 1 ♀, Matsukusa Pass, Shimohei-gun, Iwate Pref., 29. vii. 2002, M.
Nishikawa leg.; 3 ♂, Ohtaki River, Miyagi Pref., 5. vi. 1978, M. Sato leg.; 2 ♀, Mts. Zao Miyagi
Pref., 22-25. viii. 1978, M. Sato leg.; 1 ♀, Yokokawa, Shichigashuku, Miyagi Pref., 16. iv. 1995,
H. Yoshitake leg.; 2 ♂, Near-Atsumi, Yamagata Pref., 16. vi. 1960, Y. Shibata leg.; 1 ♂, Mts.
Azuma, Yonezawa, Yamagata Pref., 20. vii. 1986, K. Kusakari leg.; 2 ♂, Sasagamine, Mt.
Myoko, Niigata Pref., 14-15. vi. 1980, S. Naomi leg.; 1 ♂1 ♀, Shiga-kogen, Nagano Pref., 3-6.
viii. 1982, M. Sato leg.; 1 ♀, Near Kamaike, Otari-mura, Nagano Pref., 4. vi. 1994, T. Kishimoto
leg.; 1 ♀, Nigure-gawa, Fukui Pref., 11. vii. 1982, H. Sasaji leg.; 1 ♀, Umenoki-ootsu, Shiga
Pref., 6. vii. 1980, T. Ogata leg.; 1 ♂, Kanzaki, Miyama, Gifu Pref., 7. viii. 1995, Y. Takai leg.;1 ♂, Kurumijima, Asahi, Gifu Pref., 8-9. vi. 1993, Y. Takai leg.; 3 ♂7 ♀, Near Seryo Pass, Kifune,
Kyoto, 6. viii. 1980, Y. Shibata leg.; 1 ♂, Mt. Daisen, Tottori Pref., 30. v. 1990, R. Kuranishi leg.;2 ♂1 ♀, Mt. Hyonosen, Inaba, Tottori Pref., 5. v. 1979, T. & S. Kinoshita leg.; 1 ♀, Kenashizen,
Shinsho-mura, Okayama Pref., 4. v. 1989, O. Yamaji leg.; 1 ♀, Okutsu-cho, Okayama Pref., 4.
viii. 1977, Y. Tsuda leg. [SHIKOKU]: 2 ♂2 ♀, Mt. Kumoso, Kamiyama-cho, Tokushima Pref., 1.
vi. 1996, M. Yoshida leg.; 1 ♀, Konji, Nyuta-cho, Tokushima Pref., 6. xi. 1993, M. Sakai leg.
[KYUSHU]: 1 ♂, Mt. Sefuri, Sefuri-mura, Saga Pref., 5. vi. 2002, T. Watanabe leg.; 1 ♀, Mt.
Tara, Tara-machi, Nagasaki Pref., 3. Vi. 2002, T. Watanabe leg.; 1 ♀, Shiiba Pass, Fukuoka Pref.,11. v. 1986, T. Watanabe leg.
Distribution. Japan (Honshu, Shikoku, Kyushu).
Redescription. Male and female: Brachypterous species; body 3.5–5.4 mm (fore body 1.8–
2.7 mm) in length, moderately shining. Body entirely black but often with reﬂection of various
color (dark bluish green or bronze to dark coppery); antennae black with apical segments dark
red; mouth parts and legs dark red to black. Head large, interocular area not concave but with apair of longitudinal depressions (shallow, indistinctly demarcated, but sometimes distinctly so);punctures round, moderately dense to dense, small, distinct. Pronotum with surface uneven, witha large, shallow, indistinct V-shaped depression; punctures round, dense, irregular, sometimes
subrugous. Elytra with surface weakly uneven; punctures round, dense, irregular, sometimes sub-

38

Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

Fig. 12. Dianous japonicus Sawada (A, Hayachine, Iwate; B, Azuma, Yamagata; C, Shiga-kogen, Nagano; D,
Kifune, Kyoto; E–I, Kumoso, Tokushima). A–D, posterior halves of aedeagi showing variations on the shapeof apical part; E, aedeagus; F, 9th and 10th terga of male; G, 9th ventrite of male; H, apex of 8th ventrite ofmale; I, apices of gonocoxites. Scale 1: 0.2 mm for A–F; scale 2: 0.2 mm for G, I; scale 3: 0.3 mm for H.

The Steninae of Japan Part 1

39rugous. Legs moderately long; 4th tarsomere weakly bilobed. Abdomen with terga well convex
above; punctures very small, sparse. Lateroventrites ventromesial in position, broad, with small,sparse and setiferous punctures.
Male: Sixth ventrite very shallowly emarginate; 7th ventrite posteromedially with a very
shallow, semicircular depression, which is very weakly emarginate; 8th ventrite (Fig. 12H) posteromedially with a very large, broad emargination; 9th tergum (Fig. 12F) with ventral apophyses
relatively short; 9th ventrite almost rounded apicolaterally (Fig. 12G) but often bluntly angulate
or shortly bluntly projecting, hardly serrate posteriorly (Fig. 12G) or ﬁnely, irregularly serrate
posterolaterally, with apicolateral setae very long; 10th tergum (Fig. 12F) posteromedially with avery shallow emargination. Aedeagal median lobe with its apical part and apical sclerotized area
highly various in shape (Fig. 12A–E), furnished with setae along apical and apicolateral margins(Fig. 12E). Endophallus rather simple, median longitudinal bands (Fig. 12E) short, small, eachnarrowed apically in usual, very often with lateral sclerotized rim; expulsion hooks missing;basal tube (Fig. 12E) short, composed only of two thin shafts, connected anteriorly with submembranous elongate sac (basal room?). Parameres (Fig. 12E) slender, thin; stem mesially witha few short setae; apical area short, indistinct, very weakly swollen mesially, furnished apicomesially with sparse long setae.
Female: Eighth ventrite narrowed near the apex to form blunt apicolateral corners, with its
apicomedian part nearly rounded, bluntly or acutely pointed; gonocoxal distal sclerite (Fig. 12I)
angulate apicomesially, with apicolateral setae very long; stylus (Fig. 12I) very small, tuberculiform, with a long seta. Spermatheca not observable.
Biology and ecology. Dianous japonicus is distributed in the mountainous regions. The beetles inhabit wet stones with mosses located in or near the mountain torrents.
Remarks. Dianous japonicus is widely distributed from the northern part of Honshu throughits central and western parts to Shikoku and northern part of Kyushu throughout; and it is notrare (though not common) in Japan, but rather rare in the western distributional range (i.e., Shikoku and Kyushu). D. japonicus was ﬁrst described by Sawada (1960) based only on one female
specimen from Tani, V. Jinryo, Tokushima Pref., Shikoku. Present study distinctly shows that thisspecies has considerable infraspeciﬁc variations regarding several taxonomic characters (e.g.,body coloration; shape of the longitudinal depressions on interocular area; punctation on the pronotum and elytra; shape of the 8th ventrite of female; shape of the 9th ventrite of male; and shapeof the aedeagus).
Out of the characters that show infraspeciﬁc variations, the apical part of aedeagal median
lobe is tremendously variable in shape; and in general the northern populations of D. japonicus(Tohoku district) have narrow apical part of median lobe (Fig. 12A) while its southern populations (Shikoku and Kyushu) have broad apical part of median lobe (Fig. 12E) (see also Naomi,
2011b). There exist other types of variations regarding the median lobe. For example, some populations have the median lobe with a moderate constriction behind the middle (Fig. 12D),
whereas some other populations have the median lobe with its short, apicomedian projection(Fig. 12B, C). There are however also found various intermediate conditions linked between
those types of median lobe. Body coloration is another important character that is diverse in its
conditions among local populations of D. japonicus. The Honshu populations have in generalentirely black body color with or without dark coppery reﬂection, but the populations of Kii Peninsula show black body color distinctly with dark bluish green or bronze reﬂection. The populations of Shikoku and Kyushu also often have the similar coloration as in the populations of Kii
Peninsula in that the body has dark bluish green or bronze reﬂection. As far as other characters40

Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz(that show infraspeciﬁc variations) are concerned, we here omit describing the geographical patterns of variations because they are highly complex so that it is not so valuable to describe themin detail.
When seen retrospectively, the existence of afore-mentioned morphological variations(among D. japonicus populations) certainly urged staphylinists to describe some of its local populations as new (Watanabe, 1984; Naomi, 1988a, 1997e). However, no distinct external andaedeagal characters exist enough to taxonomically distinguish one local population from others;
and furthermore there is at base no variation regarding the structure of endophallus (Fig. 5E)
among different local populations of D. japonicus. Thus, the local populations that have more orless unique characters (e.g., a unique shape of aedeagus) should not be regarded as those that areworth considering species. This is also the case of D. viridicatus that Naomi (1997e) described as
new from Kii Peninsula. Given this, D. viridicatus Naomi be newly placed in synonymy with D.
japonicus Sawada. As things turned out, D. japonicus seems to be a staphylinid species with its
high infraspeciﬁc variations regarding several morphological characters mentioned above.
D. japonicus is closely allied to D. iwakisanus but this species is separable from the latter by
the 9th ventrite of male shallowly, broadly emarginate posteriorly, with apicolateral setae longer(Fig. 12G); the aedeagal median lobe less strongly pointed apically (Fig. 12A–E); the endophallic basal tube short, uniformly sclerotized (Fig. 12E); and the paramere shorter (Fig. 12E).
Dianous shibatai Sawada(Figs. 13A–F, 127E)
Dianous shibatai Sawada, 1960: 10; Herman, 2001: 2029; Puthz, 2001c, 42; Naomi & Puthz,
2013: 137.
Type material. Holotype: ♀ (cSa), type locality: Inagoyu, Nagano Pref.
Other material examined. [HONSHU]: 1 ♂, Houo Lodge, Mt. Houo, Yamanashi Pref., 17.
viii. 1988, A. Yoshida leg.; 1 ♀, same locality, 30. ix. 1988, K. Hosoda leg.; 1 ♀, same locality,
18. vi. 1989, K. Hosoda leg.; 1 ♀, same locality, 24. vii. 1989, T. Kato leg.; 1 ♀, same locality,
14. viii. 1989, T. Ito leg.; 1 ♀, same locality, 25. viii. 1989, K. Hosoda leg.; 1 ♂, same locality,
18. viii. 1989, K. Hosoda leg.; 1 ♀, same locality, 23. vi. 1990, K. Hosoda leg.; 1 ♂, same locality, 16. vii. 1990, K. Hosoda leg.; 1 ♀, same locality, 14. viii. 1990, K. Hosoda leg.; 1 ♀, same
locality, 4. viii. 1992, K. Hosoda leg.; 1 ♂, same locality, 13. viii. 1992, K. Hosoda leg.; 1 ♀,same locality, 26. viii. 1992, K. Hosoda leg.; 1 ♀, Senzusei-zan, Shirane-cho, Yamanashi Pref., 2.
viii. 1992, K. Haga leg.; 2 ♂, Mt. Ryogami, Ryogami Vil., Saitama Pref., 10. v. 1997, M.
Maruyama leg.; 1 ♀, same locality, 10. v. 1997, T. Kishimoto leg.; 1 ♀, Oku-Nikko, Tochigi Pref.,29. vii. 1999, V. Puthz leg.
Distribution. Japan (Honshu).
Redescription. Male: Brachypterous; body 4.8–5.7 mm (fore body 2.7–3.2 mm) in length,
elongate, moderately shining. Body black, often with bluish or greenish coppery reﬂection;mouth parts and legs dark red to black; antennae black with apical segments dark red. Headwider than elytra, large, with a pair of longitudinal sulci which run almost in parallel and moderately deep; surface with setiferous punctures round, moderately dense to dense. Pronotum wellconvex above; surface strongly uneven, with a large, shallow, indistinct V-shaped depression;
punctures dense, rough, irregular. Elytra narrowed basally, with sutural area elevated; surface
strongly uneven, with punctures rough, irregular, subrugous. Legs moderately long; 4th tarso-

The Steninae of Japan Part 1

Fig. 13. Dianous shibatai Sawada (A–D, F, Houo, Yamanashi; E, Shirane, Yamanashi). A, aedeagus; B, 9th and10th terga of male; C, 9th ventrite of male; D, apex of aedeagal median lobe with endophallic structures; E,
apices of gonocoxites, F, apex of 8th ventrite of male. Scale 1: 0.2 mm for A–C, E, 0.1 mm for D; scale 2: 0.5mm for F.

41

42

Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

mere weakly bilobed. Abdomen well convex above; punctures very small, sparse, regular. Lateroventrites in 4th to 6th segments more or less dorsomesial in position, punctate.
Seventh ventrite posteromedially with a ﬂat area which is very weakly emarginate; 8th ventrite (Fig. 13F) posteriorly with a very large, V-shaped emargination; 9th tergum (Fig. 13B) elongate, with ventral apophyses thin, moderately long; 9th ventrite (Fig. 13C) hardly serrate at posterior margin, median part of which is weakly arcuate posteriorly, with apicolateral teeth stout,
pointed, apicolateral setae very long; 10th tergum (Fig. 13B) transverse, very shallowly emarginate. Aedeagal median lobe (Fig. 13A) elongate, gently rounded at apicolateral corners, pointed
apically with a small apicomedian projection. Endophallus with median longitudinal bands (Fig.
13D) short, broad; expulsion hooks (Fig. 13D) comprising a pair of subtrapezoidal sclerites
which are weakly sclerotized; basal tube (Fig. 13D) simple, baculiform. Parameres (Fig. 13A)
thin, slender; stem mesially with a few short setae; apical area very weakly swollen mesially but
indistinct, furnished mesially with 7 to 8 setae of various length.
Female: Eighth ventrite bluntly pointed posteromedially; gonocoxal distal sclerite (Fig. 13E)
acutely pointed, weakly, irregularly serrate at apicomesial margin, with apicolateral setae very
long; 10th tergum (Fig. 13E) bluntly pointed posteromedially, which is rather different in shapefrom the male. Spermatheca not observable.
Biology and ecology. D. shibatai is a rare Dianous species; and it is distributed only in themountainous regions of central Honshu (Chubu district). The beetles inhabit wet stones withmosses located in or near the mountain torrents, but in Mt. Houo, Yamanashi, they are sometimes
found under humid dead leaves, and also on semi-arid sandy lot (about 2400 m) as well as humid
mountainous roads in natural forests.
Remarks. Dianous shibatai is allied to D. japonicus and D. iwakisanus but this species isclearly separable from the latters by the 8th ventrite of male with a large, V-shaped emargination(Fig. 13F); the 9th tergum longer (Fig. 13B); the 9th ventrite of male with apicolateral teeth
larger, more strongly pointed (Fig. 13C); the gonocoxal distal sclerite pointed, without stylus(Fig. 13E); the aedeagal median lobe with apicomedial projection (Fig. 13A); the endophallic
median longitudinal band larger and broader (Fig. 13D); and the expulsion hooks comprising apair of subtrapezoidal sclerites (Fig. 13D).
Etymology. This species was named in honour of Mr. Taichi Shibata, a coleopterist in Japan.
Genus Stenus Latreille, 1797
Stenus Latreille, 1797: 77 (type species: Staphylinus juno Paykull, ﬁxed by subsequent monotypy).
Diagnostic characters. Adults: Eyes being so large that each eye occupies the whole lateralside of head (Fig. 128A, B); head without its postocular area (Fig. 128A, B); 9th ventrite (Fig.
23C) and gonocoxites (Fig. 23G) each furnished with a pair of shorter (i.e., short, moderately
long or long, but not very long) apicolateral tufts of setae (Ganglbauer, 1895; Puthz, 1981a)
excepting South American species; spermatheca strongly sclerotized or not so. Larvae: Mala
shorter than 1st segment of maxillary palpus; ligula not or inconspicuously pubescent (Kasule,
1966; Puthz, 1981a).
Taxonomy. Traditionally, the genus Stenus (comprising 2896 species; Puthz in litt.) has long
been divided into 6 subgenera (i.e., Stenus, Nestus, Tesnus, Hemistenus, Hypostenus and Parastenus) since the second half of 19th century, only on the basis of several convenient characters

The Steninae of Japan Part 1

43(e.g., presence / absence of the “paratergites” and tergosternal sutures in abdomen; and bifurcate /non-furcate conditions of the 4th tarsomeres of legs). Ádám (1987) proposed a generic name
Metastenus with its genotype Stenus binotatus (Ljungh, 1904), which belongs to the subgenus
Hemistenus (auct.). Puthz (1999) downgraded it as a subgeneric name of Stenus. After that,Ádám (2001) proposed a replacement name Metatesnus for the Metastenus because the name
Metastenus is the objective junior homonym of Metastenus Walker, 1834 (a name of Hymenoptera).
Some subgeneric names of Stenus have been inextricably confused before Ádám (1987) proposed a generic name Metastenus as follows: Motschulsky (1860) proposed a subgeneric name
Hemistenus; and its genotype Stenus gilvipes Motschulsky, 1857a was subsequently ﬁxed byBlackwelder (1952). Rey (1884) proposed a subgeneric name Mesostenus (and its genotype is
Stenus impressus Germar, 1824). Since the name Mesostenus was preoccupied by Gravenhorst(1829), Heyden (1905) proposed a replacement name Parastenus for the Mesostenus (and its
genotype is Stenus impressus Germer, 1824). It is unfortunate that Stenus gilvipes Motschulsky,
1857a (i.e., name of the type species of Hemistenus Motschulsky, 1860) is a junior synonym of
Stenus impressus Germar, 1824 (i.e., name of the type species of Parastenus Heyden, 1905).
Since Ádám (2001) proposed the name Metatesnus, with its genotype Stenus binotatus(Ljungh, 1904), two subgeneric name changes of Stenus should be needed as follows: First, theHemistenus (auct.) be renamed Metatesnus Ádám, 2001; and thus, second, the Parastenus benecessarily renamed Hemistenus (sensu Motschulsky, 1860) since the Hemistenus is the seniorsynonym of Parastenus [see Herman, 2001: 2041]).
Özdikmen & Darilmaz (2008) proposed a replacement name Adamostenus for Metastenus(Ádám: 1987). Puthz (2009a) synonymized the name Adamostenus with Metatesnus because
Adamostenus is the objective junior synonym of Metatesnus (Puthz, 2009a). Nestus (Rey: 1884)
was synonymized with Stenus (Latreille: 1797) by Puthz (2001a), but the Nestus was revalidated
as a subgeneric name of Stenus by Ryvkin (2011). Thus, currently, the genus Stenus is divided
into the following 6 subgenera: Stenus s. str., Hemistenus Motschulsky, 1860, Nestus Rey, 1884,
Tesnus Rey, 1884, Hypostenus Rey, 1884, and Metatesnus Ádám, 2001.
As mentioned in the introduction, however, we here systematize the Steninae of Japan, basedon the species groups, without adopting the traditional subgeneric classiﬁcation of Stenus,
although we certainly notice that some species groups adopted are still mixed groups (e.g., S.
pulcher group; Puthz, 2013, p.1352). Regarding concise descriptions and characterizations of thespecies groups of Stenus, to which the Japanese species belong, see Puthz (1968a, 1970a,c,d,
1972a,b, 1980b, 1985, 1988a,b, 1998, 2002, 2003a,c, 2008a,b, 2011a,b, 2013), Naomi (2006a,
2012) and Ryvkin (2012).
Morphology. The morphology of Stenus has been described in detail in previous papers. See
Puthz (1971a, 2008a, 2013) on the general morphology of Stenus; Weinreich (1968) and Betz
(1996) on the morphology of labium as adhesive-capture apparatus; Betz (2002, 2003) on themorphology of tarsus; Blum (1979) on the morphology of abdominal musculature; Naomi(2006a,b) on the morphology of aedeagus and spermatheca.
Paleontology. The clade Stenus is considered to have origined in the Mesozoic (Lower Cretaceous), according to the known fossil records of Stenus species, which was reviewed by Puthz(2008a, 2010b). Presently, there have been known 23 fossil Stenus species world-wide (Puthz,
2008a, 2010b); note here that the number of fossil species do not include undescribed fossil Stenus species which were recently found in Burmesian amber (ca. 100–110 Mya). Out of them, theoldest fossil Stenus species is S. imputribilis Ryvkin, 1988 (Stenus s. str.), which was discovered

44

Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

from the Cretaceous deposits of East Russia (Creataceous ca. 90–110 Mya). Another fossil Stenus from about same old age is S. inexspectatus Schlüter, 1978 (Tesnus?), which was discoveredfrom an amber of the Northwestern France. Fifteen fossil Stenus species from the Baltic amber
were researched, 8 species of which were described as new to science in Puthz (2010b). See
Puthz (2010b) for further information on fossil Stenus species.
Biology and Ecology. The Stenus species are divided into the following 4 groups according
to their habitat preferences: (a) inhabitants of leaf litter; (b) surface runners on open grounds; (c)inhabitants of littoral environments; and (d) plant climbers. So are the Japanese Stenus species.
The Stenus species of different habitat preferences are here brieﬂy described in order. Regarding
life forms and related ecological traits of some European Stenus species, see Betz (1998) and
Betz & Fuhrmann (2001).
(a) Inhabitants of leaf litter. Out of the Japanese Stenus (347 species), most species of S.
humilis group, S. cirrus group, S. asyura group, S. indubius group and S. cephalotes group (about
250 species) are litter dwellers; and these Stenus beetles inhabit leaf litter, leaf debris and/or
humus with mosses, which keep moderate humidity. They inhabit leaf litter heaped in the woods
and forests, which stand from near the seashore and plains, through in the low and high mountainous regions, to the timber limit at alpine zone. For example, the beetles of S. kiyosumiensis
Naomi & Takeda, 1991 inhabit litter in the woods near seashore or in the forests of low mountainous regions, while the beetles of S. fujimontis Puthz, 2001c inhabit litter heaped in the shrubat the timer limit of Mt. Fuji (ca. 2300 m). It was reported that the beetles of S. alpicola group (asrelicts of glacial periods) inhabit grass litter and mosses in the wilderness at alpine zone (Puthz,
2003c); and they also inhabit leaf litter and mosses in the larch and other plant communities inthe subarctic zone (Ryvkin, 2000). However, no solid information has been obtained regarding
habitats of the Japanese species of this group. It is very often common in Japan that two or more
species of different species groups live together in the same litter of the same woods or forests.
These litter dwellers usually move slowly and clumsily; and those of S. humilis group move very
slowly.
(b) Surface runners on open grounds. Habitats of some Stenus species are open or bare lands,
paddy ﬁelds and stony riverbanks, all of which are semi-arid environments. S. alienus is a representative Stenus species as surface runners in Japan, just as S. comma is in Europe (Betz, 1998;
Betz & Fuhrmann, 2001). The beetles of S. alienus are commonly found on the more or lessdried paddy ﬁelds and open lands in plains and low mountainous regions. The beetles of S. lewisius and S. puberulus inhabit stony riverbanks in plains; and the beetles walk around and often gounder stones. The beetles of S. tomitaorum inhabit open grasslands in Hokkaido. The surface
runners usually move moderately or agilely.
(c) Inhabitants of littoral environments. Habitats of many Stenus species of the groups treatedin this monograph are littoral (i.e., waterside) environments. Those beetles inhabit moist or wet
plant debris and leaf litter of grasses (e.g., reeds and sedges) grown near the rivers or ponds. The
representative species are S. anthracinus, S. juno, S. sauteri, S. miyama, S. bohemicus, S. aquilonalis, S. mercator, S. cicindeloides, S. ﬂavidulus, etc. All species of S. pubescens group, S. pallitarsis group, and S. ﬂavipes group are also littoral environment dwellers. S. melanarius seem tohave a broad array of habitat preferences; and the beetles actually inhabit not only the afore-mentioned littoral environments, but also the vicinity of running waters of mountainous areas (as in
Dianous species), and they also live under sea algae at seashores. The inhabitants of littoral environments are usually move slowly.
(d) Plant climbers. The members of S. cylindricollis group, S. coelogaster group (Puthz,

The Steninae of Japan Part 1

45

2013: 1330), and S. bispinus group are arboreal species, which is to say that these beetles inhabit
positively (i.e., prefer inhabiting) tree leaves and stems during (at least some periods of) theirlives. Thus, these beetles are very often collected by coleopterists who aim at collecting the Cerambycids by beating the alive or dead twigs and branches of broadleaved trees. This is highly
likely in cases where these beetles are collected at the evergreen forests in subtropical Nansei
Islands (e.g., Iriomote Is., Ishigaki Is.). All species of S. pubescens group, S. pallitarsis group, S.
ﬂavipes group, and also S. ﬂavidulus are, as mentioned above, dwellers of littoral environments.
However, these beetles can be also considered plant climbers, given that they inhabit also emergent vegetation of standing water, and they very often walk among leaves and stems of the plants(e.g., reeds) (Toyoda, 1999; Naomi & Ito, 2014). These plant climbers usually move moderately
quickly.
Species group of S. comma LeConteS. comma group consists of 7 species in Japan; see Puthz (1981b, 2008b) regarding a characterization and taxonomy on the East Asian species of this group. Diagnostic characters are as follows: Legs with 4th tarsomere simple; lateroventrites distinctly ventromesial in position, moderately broad to broad; 9th ventrite of male usually without apicolateral teeth and macrosetae (Figs.
14B); aedeagal median lobe usually with apical sclerotized area sub-pentagonal in shape, apicolateral corners distinctly angulate (Fig. 14A); endophallic basal tube with tube body arrowheadshaped, which is partially covered with a cloak-like sclerite (Fig. 17A); gonocoxite serrate posteriorly, without apicolateral teeth (Figs. 14G); spermatheca not observable.
Key to the Japanese species of S. comma group1(8) Elytra each with a yellowish spot.
2(5) Tenth tergum of male very shallowly emarginate posteriorly; apex of aedeagal paramerewith long setae which turn posteriorly (Fig. 14A); endophallic median longitudinal bands
with dorsal bands broader; expulsion hooks fused, medium-sized, distinctly protruding
anterolaterally (Fig. 14D).
3(4) Elytral yellowish spots larger (Fig. 127F); abdomen with latroventrites broader; 6th ventriteof male posteromedially with a broad but short ﬂat area (Fig. 14C); aedeagal median lobe
distinctly angulate apicolaterally (Fig. 14A); endophallic cloak-like sclerite longer (Fig.
14E) ............................................................................................................. S. comma LeConte4(3) Elytral yellowish spots smaller (Fig. 127G); abdomen with latroventrites narrower; 6th ventrite of male posteromedially with a semicircular depression (Fig. 15C); aedeagal median
lobe weakly angulate (Fig. 15A) or rounded (Fig. 15G) apicolaterally; endophallic cloaklike sclerite shorter (Fig. 15D) .......................................................................S. tenuipes Sharp
5(2) Tenth tergum of male entire; apex of aedeagal paramere without long setae which turn posteriorly (Fig. 17C); endophallic median longitudinal bands with dorsal bands narrower (Fig.
17C); expulsion hooks fused, atrophied to be a smaller sclerite.
6(7) Legs dark red to black; 7th ventrite of male posteromedially with a smaller depression (Fig.
16E); aedeagal median lobe less strongly angulate apicolaterally, with apical triangular area
shorter (Fig. 17C); endophallic explusion hooks fused to be a nearly Y-shaped sclerite (Fig.
17C) ........................................................................................................S. biguttatus Linnaeus
7(6) Legs yellowish brown to reddish brown; 7th ventrite of male posteromedially with a larger

46

Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

depression (Fig. 18G); aedeagal median lobe more strongly angulate apicolaterally, withapical triangular area longer (Fig. 18C); endophallic explusion hooks fused to be a nearly
heart-shaped sclerite (Fig. 18C) .......................................................................S. alienus Sharp
8(1) Elytra each without yellowish spot.
9(12) Head larger (Fig. 127J); 6th ventrite posteromedially modiﬁed in male (Fig. 20B); aedeagal
median lobe with apical sclerotized area shorter, not covered with setiferous pores (Fig.
19A); paramere apicomesially with setae long to very long (Fig. 19A).
10(11) Body narrower; anteromedian parts of elytra commonly punctate; 6th and 7th ventrites ofmale each posteromedially with a depression smaller, shallower (Fig. 19F); median lobe
broader, usually with a small hump at apicolateral corner (Fig. 19A) .... S. anthracinus Sharp
11(10) Body broader; anteromedian parts of elytra with punctures arranged from anteromesial toposterolateral direction; 6th and 7th ventrites each posteromedially with a depression
larger, deeper (Fig. 20B); median lobe narrower, simply angulate apicolateraly (Fig. 20A)..........................................................................................S. puthzorum Naomi & Watanabe
12(9) Head smaller (Fig. 127K) ; 6th ventrite posteromedially not modiﬁed in male; aedeagal
median lobe with apical sclerotized area longer, distinctly covered with setiferous pores(Fig. 21A); paramere apicomesially with setae short to moderately long (Fig. 21A)................................................................................................................ S. kobensis Cameron
Stenus comma LeConte(Figs. 14A–G, 127F)
Stenus comma LeConte, 1863: 50; Herman, 2001: 2135; Naomi, 1997e: 5; Naomi & Puthz,
2013: 137.
Type material. Type locality: Middle and western States of the U. S. A.
Other material examined. [HOKKAIDO]: 3 ♂2 ♀, Sekihoku Pass, 27. viii. 1977, M. Satoleg.; 1 ♂1 ♀, Touro Lake, 18. vi. 1976, M. Sato leg.; 1 ♂1 ♀, Piribetsu River, Honbetsu-cho, 12.
vii. 1995, K. Haga leg.; 1 ♂1 ♀, Sounkyo, 11. vii. 1985, N. Yasuda leg.; 3 ♀, Iwabokki, Kushiro
Marsh, 26. viii. 1990, M. Sakai leg.; 2 ♀, Shoro nr Kushiro, 26. vi. 1981, S. Morita leg.; 2 ♂,Nukabira, Kamishihoro-cho, 6. vii. 1987, K. Yahiro leg.; 1 ♀, Ohtsu, Toyokoro-cho, 27. v. 1990,
K. Haga leg.; 1 ♀, Oketo, 26. viii. 1992, T. Kato leg.; 1 ♀, Ashoro, 13. vi. 1984, O. Tadauchi leg.
[CHINA]: 3 ♀ (cS), China SW Gansu, road Luqu-Waxu, km 5, 3300 m, 12–13. vii. 1994, K. W.
Anton leg.; 1 ♀ (cS), China, Gansu, Hua er Ge, 5 km SSW Luqu, 3400 m, 13. vii. 1994, A.
Smetana leg.; 1 ♀ (cS), China, Sichuan 70 km N Zoige, 3400 m, 14. vii. 1994, A. Smetana leg.;2 ♀ (cS), China, Gansu, Xinlong Shan, cca 70 km S Lanzhou, 2225–2380 m, 7. viii. 1994, A.
Smetana leg.; 1 ♀ (cS), China, Gansu, Yonghai cca 20 km SW Yuzhong 2700-2800 m, 9. viii.
1994, A. Smetana leg.
Distribution. Japan (Hokkaido); Korea, China, Mongolia, Russia, Europe, Canada, USA.
Redescription. Male and female: Macropterous; body 4.8–6.2 mm (fore-body 2.6–2.8 mm) in
length, robust, with antennae relatively short. Body entirely black, with metallic reﬂection; elytra
each with a yellowish spot; labrum, antennae and legs black. Head concave between eyes, with a
median longitudinal convex area; punctures round to elliptical, very dense, small, distinct. Pronotum with surface uneven, with a median fovea behind the middle; punctures round to elliptical,very dense, small, deep. Elytra with surface weakly uneven; punctures round to elliptical, very
dense. Legs relatively long; 4th tarsomere simple. Abdomen narrowed posteriorly; punctures

The Steninae of Japan Part 1

Fig. 14. Stenus comma LeConte (Touro, Hokkaido). A, aedeagus; B, 9th ventrite of male; C, 6th to 8th ventrites
of male; D, endophallic expulsion hook; E, endophallic cloak-like structure; F, 9th and 10th terga of male; G,
apex of gonocoxite. Scale 1: 0.2 mm for A, B, 0.1 mm for D, E, G; scale 2: 0.3 mm for C; scale 3: 0.2 mm for
F.

47

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Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

round, dense, small and regular in anterior segments, while punctures in posterior segments moderately dense, very small and regular. Lateroventrites ventromesial in position, rather wide,
densely, ﬁnely punctate.
Male: Sixth ventrite (Fig. 14C) posteromedially with a broad, short ﬂat area; 7th ventrite(Fig. 14C) posteromedially with a deep semicircular depression, which is arcuately emarginate,
and also medially with a shallow depression which is contiguous with the posteromedian depression; 8th ventrite (Fig. 14C) posteriorly with a large V-shaped emargination; 9th tergum (Fig.
14F) with ventral apophyses short, broadened laterally at subapical part; 9th ventrite (Fig. 14B)
rounded apicolaterally, emarginate posteriorly, with apicolateral setae short; 10th tergum (Fig.
14F) very shallowly emarginate. Aedeagal median lobe (Fig. 14A) robust, distinctly angulate apicolaterally, almost triangular behind the apicolateral corners, apical sclerotized area posteriorly
covered with small pores. Endophallic median longitudinal bands (Fig. 14A) short, with ventral
bands narrow, covered with dot-like sculptures, dorsal bands very broad; expulsion hooks (Fig.
14A, D) partially fused to form a nearly X-shaped sclerite, which projects apicolaterally; basal
tube (Fig. 14A) with sclerotized part of basal room composed only of left shaft, basal constriction distinct, tube body arrowhead-shaped; cloak-like sclerite relatively long (Fig. 14E). Parameres (Fig. 14A) almost straight, each rounded apically; apical area very long, furnished mesiallywith 25 to 26 setae of short to moderate length, and also most apically with 4 to 5 very long setae
which turn posteriorly.
Female: Eighth ventrite bluntly pointed or angulate posteromedially; gonocoxites (Fig. 14G)
each almost rounded apicolaterally, distinctly serrate posteriorly, with apicolateral setae very
long. Spermatheca not observable.
Biology and ecology. Stenus comma is distributed in the plains and mountainous regions inJapan. The beetles inhabit open lands and forests near there, but collecting records show that theyalso inhabit leaf litter heaped near the shores of rivers, lakes and marshes in Japan.
Remarks. S. comma was ﬁrst recorded from Japan (Hokkaido) by Naomi (1997e). After theﬁrst record in Hokkaido, it was found that this species is relatively common there. Among theJapanese members of S. comma group, S. comma is allied to S. tenuipes, but it is separable fromthe latter by the elytral yellowish spots larger, the abdomen with broader latroventrites, the 6th
ventrite of male posteromedially with a broad but short ﬂat area (Fig. 14C), the 7th ventrite ofmale posteromedially with a smaller semicircular depression (Fig. 14C), the aedeagal median
lobe distinctly angulate apicolaterally (Fig. 14A), and the cloak-like sclerite longer (Fig. 14E).
See Puthz (2008b: 185; ﬁgs. 24–29) regarding variation of the shape of the apical part of aedeagal median lobe.
Stenus tenuipes Sharp(Figs. 15A–G, 127G)
Stenus tenuipes Sharp, 1874: 80; Herman, 2001: 2416; Naomi & Puthz, 2013: 137.
Stenus biguttatus Linnaeus, 1758: Sharp, 1889: 325.
Stenus comma LeConte, 1863: Naomi, 1988d: 55.
Type material. Syntypes (NHML), type localities: Hiogo, Kiu Kiang, China.
Other material examined. [HOKKAIDO]: 1 ♂, Kojyo-hama, Shiraoi, 16. vii. 1953, Y.
Watanebe leg.; 1 ♂, Kitamoshiri, Horokanai-cho, 27. vii. 1998, K. Haga leg.; 1 ♂, Piribetsu
River, Honbetsu-cho, 12. vii. 1995, K. Haga leg.; 1 ♂, Sekihoku Pass, 27. viii. 1977, M. Sato

The Steninae of Japan Part 1

Fig. 15. Stenus tenuipes Sharp (A–E, Itoigawa, Niigata; F, Ohtaki, Miyagi; G, Kitamoshiri, Hokkaido). A,
aedeagus; B, 9th ventrite of male; C, 6th to 8th ventrites of male; D, endophallic cloak-like structure; E, apexof gonocoxite; F, 9th and 10th terga of male; G, posterior part of aedeagal median lobe. Scale 1: 0.2 mm for A,
B, G, 0.1 mm for D, E; scale 2: 0.3 mm for C; scale 3: 0.2 mm for F.

49

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Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

leg.; 1 ♂, Muroran City, Iburi, 13. vii. 1969, K. Miyamori leg.; 1 ♀, same locality, 31. vii. 1971,
K. Miyamori leg. [HONSHU]: 1 ♂, Kawara-bo, Mt. Hayachine, Iwate Pref., 22-24. vi. 1980, S.
Naomi leg.; 1 ♂, Zenjin, Mt. Chokai, Akita Pref., 19-20. vi. 1980, S. Naomi leg.; 1 ♂, same locality, 3. viii. 1994, K. Ohgi leg.; 2 ♂1 ♀, Ohtaki-gawa, Miyagi Pref., 5. vi. 1978, M. Tomokuni
leg.; 1 ♀, same locality and date, M. Sato leg.; 1 ♀, Suge-numa, Miyagi Pref., 5. vi. 1978, M.
Sato leg.; 2 ♂1 ♀, Yakurai Spa., Miyagi Pref., 21. viii. 1978, M. Sato leg.; 2 ♂1 ♀, Kaikake Spa.,
Yuzawa-cho, Niigata Pref., 14. v. 1995, K. Haga leg.; 2 ♂2 ♀, Yunotani-mura, Niigata Pref., 5.
viii. 1995, K. Haga leg.; 1 ♀, Tonaka River, Yuzawa-cho, Niigata Pref., 12. v. 1985, K. Haga leg.;1 ♀, Sasagamine, Mt. Myoko, Niigata Pref., 14-15. vi. 1980, S. Naomi leg.; 1 ♀, Shiga-kogen,
Nagano Pref., 3-6. viii. 1982, M. Sato leg.; 2 ♂, Mt. Ontake, Kiso, Nagano Pref., 27. vii. 1985,
M. Tao leg.; 3 ♂2 ♀, Itoigawa, Niigata Pref., 29. x. 1993, K. Ohgi leg.; 1 ♀, Takanami Pond,
Itoigawa, Niigata Pref., 29. x. 1993, K. Ohgi leg.; 2 ♂2 ♀, Sakura River, Ibaragi Pref., 9. iv. 1978,
M. Tao leg.; 1 ♂, Nakaminato, Ibaragi Pref., 8. iv. 1978, M. Tao leg.; 1 ♀, Yasumori, Tsukuba
City, Ibaragi Pref., 17. iv. 1994, K. Ohgi leg.; 2 ♂3 ♀, Urawa City, Saitama Pref., 16. iv. 1994, K.
Ohgi leg.; 1 ♂1 ♀, Hannou City, Saitama Pref., 3. iv. 1994, K. Ohgi leg.; 1 ♀, Mt. Gori, Hiroshima Pref., 4. vi. 1978, H. Aramaki leg.; 3 ♂4 ♀, Ikenohara, Ube City, Yamaguchi Pref., 20. iii.
1994, K. Ohgi leg.; 3 ♂2 ♀, Tokuchi-cho, Yamaguchi Pref., 19. iii. 1994, K. Ohgi leg.
[KYUSHU]: 1 ♂, Kurusu, Naokawa-mura, Ohita Pref., 30. x. 1984, S. Sasaki leg.; 1 ♂, same
locality and date, K. Kazato leg.; 1 ♀, Tade River, Higashi-sefuri, Saga Pref., 21. vi. 1993, S.
Nomura leg.; 1 ♂1 ♀, Ohmura City, Nagasaki Pref., 9. iv. 1980, S. Imasaka leg.; 1 ♂1 ♀, Ohmura
City, Nagasaki Pref., 20. v. 1980, S. Imasaka leg.; 3 ♂, Hirakawa, Kagoshima Pref., 28. v. 1975,
H. Makihara leg.
Distribution. Japan (Hokkaido, Honshu, Shikoku, Kyushu; Sado Is.); Korea, China.
Redescription. Male and female: Macropterous species; body 4.3–5.8 mm (fore-body 2.2–2.7mm) in length, elongate. Body entirely black, with metallic reﬂection; elytra each with a yellowish spot; labrum black; antennae with 1st segment black, 2nd to 11th segments dark red; legswith femora black, tibiae and tarsi dark red. Head concave between eyes, with a narrow medianlongitudinal convex area; punctures round, dense, small, distinct. Pronotum with surface uneven,with a median fovea behind the middle; punctures round to elliptical, very dense. Elytra with surface weakly uneven; punctures round, very dense, distinct. Legs relatively long; 4th tarsomere
simple. Abdomen narrowed posteriorly; punctures round, moderately dense, and small in 3rd to
7th segments, while punctures in 8th segment very small and sparse. Lateroventrites ventromesial in position, densely punctate.
Male: Fourth ventrite posteromedially with a semicircular ﬂat area; 5th ventrite posteromedially with a semicircular ﬂat area which is very shallowly emarginate; 6th ventrite (Fig. 15C) posteromedially with a crescent-shaped depression, which is very shallowly emarginate; 7th ventrite(Fig. 15C) posteromedially with a large, deep, semicircular depression, which is arcuately emarginate, and also medially with a shallow crescent depression which is contiguous with the posteromedian depression; 8th ventrite (Fig. 15C) posteriorly with a large V-shaped emargination;
9th tergum (Fig. 15F) with ventral apophyses moderately long; 9th ventrite (Fig. 15B) elongate,rounded apicolaterally, very shallowly emarginate posteriorly, with apicolateral setae short; 10th
tergum (Fig. 15F) very shallowly emarginate. Aedeagal median lobe obtusely angulate (Fig.
15A) or weakly rounded (Fig. 15G) apicolaterally, almost triangular behind the apicolateral corners, apical sclerotized area posteriorly covered with small pores. Endophallic median longitudinal bands (Fig. 15A) short, with ventral bands narrow, covered with dot-like sculptures, dorsal
bands very wide; expulsion hooks (Fig. 15A) fused to form a nearly X-shaped sclerite; basal tube

The Steninae of Japan Part 1

51(Fig. 15A) with sclerotized part of basal room composed only of left shaft, tube body arrowheadshaped; cloak-like sclerite as in Fig. 15D. Parameres (Fig. 15A) almost straight, each small but
distinctly incised apicomesially; apical area very long, furnished mesially with 25 to 26 setae ofshort to moderate length; and also most apically with 4 to 5 very long seta.
Female: Eighth ventrite bluntly pointed or angulate posteromedially; gonocoxites (Fig. 15E)
each almost rounded or blunt apicolaterally, distinctly serrate posteriorly, with apicolateral setaevery long. Spermatheca not observable.
Biology and ecology. Stenus tenuipes is distributed in the plains and mountainous regions inJapan. The beetles inhabit litter in natural forests; and they also live in leaf litter heaped near the
shores of rivers and ponds.
Remarks. Sharp (1874) described Stenus tenuipes as new from Japan; and after that, Sharp(1889) recorded S. biguttatus as “S. biguttatus var.” from Japan (Awomori; Hakodate), but the
specimens recorded from Japan by Sharp are not S. biguttatus but S. tenuipes (Puthz, 1981b).
Naomi (1988d) mistook S. tenuipes for S. comma.
Stenus tenuipes is allied to S. comma, but it is separable from the latter by the elytral yellowish spots smaller, the abdomen with narrower latroventrites; the 6th ventrite of male posteromedially with a crescent-shaped depression (Fig. 15C), the 7th ventrite of male posteromediallywith a larger semicircular depression (Fig. 15C), the aedeagal median lobe more weakly angulate
or weakly rounded apicolaterally (Fig. 15A), the paramere small but distinctly incised at the subapico-mesial part (Fig. 15A), and the cloak-like sclerite shorter (Fig. 15D). S. tenuipes shows
infraspeciﬁc variation regarding the size of elytral marking (small: Naomi, 1988d, ﬁg. 1E andlarge: ibid., ﬁg 1F), which sometimes causes coleopterists to do misidentiﬁcation of this species.
This species also shows variation regarding structure of the apical part of aedeagal median lobe.
The median lobe has its apicolateral angle (Fig. 15A) although it is less strongly angulate thanthat in S. comma, but it is sometimes rounded apicolaterally, without the apicolateral corner (Fig.
15G; Puthz, 2008b: 178; ﬁg. 11).
Stenus biguttatus Linnaeus(Figs. 2aA, 16A–E, 17A–D, 127H)
Stenus biguttatus Linnaeus, 1758: 422; Naomi & Puthz, 1996: 160; Naomi, 1997e: 5; Herman,
2001: 2085; Naomi & Puthz, 2013: 137.
Stenus szechuanus Puthz, 1981b: Naomi, 1988d: 56.
Type material. Type locality: Europe.
Other material examined. [HOKKAIDO]: 1 ♂6 ♀, Ohtsu, Toyokoro-cho, 27. v. 1990, K.
Haga leg.; 3 ♂, Rikubetsu, 30. vii. 1986, S. Nomura leg.; 1 ♂1 ♀, Kottaro, Kushiro Moor, 29. viii.
1990, M. Sato leg.; 1 ♀, Bankei, Sapporo, 24. vi. 1977, N. Nishikawa leg.; 1 ♀, Kamayausu,
Ishikari, 6. vi. 1986, M. Ohara leg.; 2 ♂3 ♀, Mt. Hakken, 27. v. 1977, N. Nishikawa leg.; 1 ♂,Shakubetsu, Onbetsu-cho, 3. viii. 1988, K. Haga leg.; 1 ♂, Tanno-cho, 27. viii. 1992, T. Katoleg.; 2 ♀, Iwaubetsu, Shiretoko, 7. vii. 1986, S. Nomura leg.
Distribution. Japan (Hokkaido); China, Russia, Azerbaijan, Armenia, Europe.
Redescription. Male and female: Macropterous; body 4.7–5.6 mm (fore-body 2.3–2.7 mm) in
length, elongate, dull; paraglossae ovoidal (Fig. 2aA). Body black with metallic reﬂection; elytra
each with a yellowish spot; labrum black; antennae and legs dark red to black. Head concave
between eyes, with median longitudinal keel short, very narrow; punctures round to elliptical,

52

Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

Fig. 16. Stenus biguttatus Linnaeus (A, B, D, E, Rikubetsu, Hokkaido; C, Toyokoro, Hokkaido). A, 9th and 10th
terga of male; B 9th ventrite of male; C, posterior part of gonocoxite; D, posterior part of 8th ventrite ofmale; E, 7th ventrite of male. Scale 1: 0.2 mm for A, B, D, 0.1 mm for C; scale 2: 0.3 mm for E.

dense to very dense, small, distinct. Pronotum with surface weakly uneven, with a median fovea
behind the middle; punctures very dense, small, rough. Elytra with surface weakly uneven; punctures round to elliptical, very dense, various in size. Legs relatively long; 4th tarsomere simple.
Abdomen narrowed posteriorly, well convex above; punctures round to elliptical, moderately
dense, small and distinct in anterior segments, while punctures in posterior segments round toThe Steninae of Japan Part 1

Fig. 17. Stenus biguttatus Linnaeus (Tanno, Hokkaido). A, endophallic basal tube with cloak-like structure; B,
cloak-like structure; C, Aedeagus, without showing cloak-like structure; D, endophallic basal tube. Scale 1:
0.1 mm for A, B, D, 0.2 mm for C.

53

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Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

elliptical, very small and regular. Lateroventrites ventromesial in position, wide, covered usuallywith small punctures (but sometimes also with large ones).
Male: Sixth ventrite shallowly emarginate posteromedially; 7th ventrite (Fig. 16E) posteromedially with a very deep depression (or cliff), which is arcuately emarginate, and also mediallywith a large, shallow depression which is contiguous with the posteromedian depression; 8thventrite (Fig. 16D) posteriorlly with a broad, arcuate emargination; 9th tergum (Fig. 16A) withventral apophyses moderately long; 9th ventrite (Fig. 16B) rounded apicolaterally, very shallowly emarginate posteriorly, with apicolateral setae short; 10th tergum (Fig. 16A) almost entire.
Aedeagal median lobe (Fig. 17C) wide, distinctly angulate at apicolateral corners which each has
a small hump, almost triangular behind the apicolateral corners, apical sclerotized area covered
with moderately dense pores which each has a very short seta. Endophallic median longitudinalbands (Fig. 17C) wide, ventral bands each narrowed anteriorly, a little shorter than dorsal bands
which are covered with dot-like sculptures; expulsion hooks (Fig. 17C) atrophied to be a small,Y-shaped sclerite which is located behind posterior margins of median longitudinal bands; basal
tube (Fig. 17A, C, D) with sclerotized part of basal room composed of two shafts of different
length, basal constriction distinct, tube body arrowhead-shaped; cloak-like sclerite as in Fig.
17B. Parameres (Fig. 17C) almost straight, relatively thick, each acutely pointed apically; apicalarea long, furnished mesially with 25 to 30 setae of short to moderate length.
Female: Eighth ventrite entire; gonocoxites (Fig. 16C) each almost rounded apicolaterally,ﬁnely serrate posteriorly, with apicolateral setae very long. Spermatheca not observable.
Biology and ecology. Stenus biguttatus is distributed in the plains and mountainous regionsin Japan. The beetles inhabit open ﬁelds or grass lands; and they also live in leaf litter heapednear the rivers, lakes and marshes in Japan.
Remarks. Naomi (1988d) once recorded S. szechuanus from Hokkaido, but all specimens of
the Stenus species belong to S. biguttatus (Naomi & Puthz, 1996), which was virtually the ﬁrst
record of S. biguttatus from Japan. It was found after the record that the true S. biguttatus is relatively common in the plains of Hokkaido. Among the Japanese members of comma-group, S.
biguttatus is allied to S. alienus, but it is separable from the latter by the legs darker in color(dark red to black), the triangular apical part of aedeagal median lobe shorter (Fig. 17C), and theendophallic cloak-like sclerite structured as in Fig. 17B. In some cases, S. biguttatus is separablefrom S. alienus also by the shape of posteromedian depression of male 7th ventrite (Fig. 16E);
that is, it is shorter in S. biguttatus than in S. alienus. However, since it shows variation in shape
in S. biguttatus, its shape is not necessarily very useful for identifying the species.
Stenus alienus Sharp(Figs. 18A–G, 127I)
Stenus alienus Sharp, 1874: 81; Herman, 2001: 2050; Puthz, 2001c: 42; Naomi & Puthz, 2013:
137.
Type material. Syntypes (NHML), type localities: Simabara, Osaka.
Material examined. [HOKKAIDO]: 3 ♂2 ♀, Mt. Sokuryo, Muroran, 7. viii. 1971, K.
Miyamori leg. [HONSHU]: 1 ♀, Yasumiya, Towada-lake, Aomori Pref., 4-5. viii. 1966, M. Chujo
leg.; 1 ♂, Kawara-bo, Mt. Hayachine, Iwate Pref., 22-24. vi. 1980, S. Naomi leg.; 3 ♂, Uenohara,
Miyagi Pref., 20. viii. 1977, M. Sato leg.; 2 ♀, Nuruyu, Hanayama, Miyagi Pref., 6. viii. 1984, K.
Morimoto leg.; 1 ♀, Shintabaru, Fukushima Pref., 30. vii. 1983, M. Tao leg.; 2 ♀, Senjyogahara,

The Steninae of Japan Part 1

Fig. 18. Stenus alienus Sharp (A, B, D, E, G, Nikko, Tochigi; C, F, Hayachine, Iwate). A, 9th ventrite of male;B, 9th and 10th terga of male; C, aedeagus; D, apex of 8th ventrite of male; E, apex of gonocoxite; F, endophallic cloak-like structure; G, 6th to 7th ventrites of male. Scale 1: 0.2 mm for A, C, D, 0.1 mm for E, F;
scale 2: 0.2 mm for B; scale 3: 0.2 mm for G.

55

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Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

Nikko, Tochigi Pref., 21. vii. 1997, T. Niisato leg.; 1 ♂2 ♀, Yumoto, Nikko, Tochigi Pref., 19. vii.
1977, M. Tao leg.; 1 ♂, Chuzenji, Nikko, Tochigi Pref., 5. V. 1966, Y. Miyake leg.; 1 ♀, Shiobara,
Tochigi Pref., 20. v. 1979, T. Niisato leg.; 2 ♀, Nogi C., Tochigi Pref., 24. xi. 1976, T. Niisato
leg.; 1 ♂, Naka River, Ibaragi Pref., 7. iv. 1978, M. Tao leg.; 2 ♂, Musashino C., Tokyo, 9. vi.
1976, T. Niisato leg.; 1 ♀, Tama River, Fuchu, Tokyo, 29. viii. 1982, M. Tao leg.; 1 ♂1 ♀,Machida C., Tokyo, 28. v. 1981, T. Niisato leg.; 2 ♂1 ♀, Mt. Takao, Tokyo, 2. iv. 1975, K.
Kawada leg.; 1 ♀, Tsurumi-ku, Yokohama C., Kanagawa Pref., 10. vii. 1983, M. Tao leg.; 1 ♂,Tsurukawa, Kanagawa Pref., 14. iii. 1975, K. Kawada leg.; 1 ♂2 ♀, Tsurumi-ku, Yokohama C.,
Kanagawa Pref., 15. iii. 1976, M. Tao leg.; 1 ♀, Noborito, Kanagawa Pref., 25. iii. 1978, M. Taoleg.; 2 ♂, Tsurumi River, Kanagawa Pref., 25. iii. 1979, M. Tao leg.; 1 ♀, Kinome Pass, Fukui
Pref., 25. vi. 1982, H. Sasaji leg.; 2 ♂1 ♀, same locality, 25. iv. 1982, H. Sasaji leg.; 1 ♂1 ♀, Taniyama, Ohno, Fukui Pref., 6. vi. 1976, H. Sasaji leg.; 1 ♂, Mt. Kariyasu, Fukui Pref., 9. v. 1981,
H. Sasaji leg.; 1 ♂, Sugentan, Kono-mura, Fukui Pref.; 22. vii. 1981, H. Sasaji leg.; 1 ♀, Yashaga-ike, Fukui Pref., 9-11. viii. 1975, H. Sasaji leg.; 1 ♀, Mt. Monjyu, Fukui Pref., 22. v. 1973,
H. Sasaji leg.; 1 ♀, Makidani, Mt. Hino, Fukui Pref., 21. v. 1978, H. Sasaji leg.; 1 ♂2 ♀, Kisofukushima, Nagano Pref., 25. vi. 1975, H. Ohishi leg.; 1 ♂, Todai, Nagano Pref., 6. v. 1977, M.
Tao leg.; 1 ♀, Shiga Highland, Nagano Pref., 1-3. viii. 1978, M. Sato leg.; 1 ♂, Inayasu, Nagano
Pref., 5. v. 1977, M. Tao leg.; 3 ♂2 ♀, Shinhotaka Spa, Gifu Pref., 10-12. vi. 1980, S. Naomi leg.;2 ♂, Gifu, 4. iii. 1946, K. Ohbayashi leg.; 2 ♂1 ♀, Nagara River, Gifu C., Gifu Pref., 14. xi. 1954,
Z. Natuse leg.; 1 ♂, Nisshin, Aichi Pref., 25. xii. 1985, T. Kato leg.; 1 ♂, Shimogamo, Kyoto, 11.
xi. 1980, T. Ogata leg.; 1 ♀, Sandoai-cho, Mie Pref., 14. iii. 1976, H. Ohishi leg.; 1 ♀, Mt.
Daisen, Tottori Pref., 3. v. 1991, A. Watanabe leg.; 1 ♀, same locality, 3-5. vi. 1980, S. Naomi
leg.; 3 ♂, Wake, Okayama Pref., 17. iv. 1977, S. Naomi leg.; 1 ♀, same locality, 29. iv. 1997, S.
Naomi leg.; 3 ♂, Okayama C., Okayama Pref., 1. vi. 1977, Fukushima leg.; 1 ♀, Tabarushimo,
Okayama Pref., 26. iv. 1976, S. Naomi leg.; 1 ♂, Okayama C., Okayama Pref., 14. v. 1977, S.
Naomi leg.; 1 ♀, Minamidani, Fuse-mura, Dogo Is., Oki Is., Shimane Pref., 18-25. v. 2004, T.
Shimada leg.; 1 ♀, same locality, 1-11. vi. 2004, T. Shimada leg.; 3 ♀, Kabura-sugi, Saigô-cho,
Dôgo Is., Oki Isls., Shimane Pref., 17. vii. 2003, T. Shimada leg. [SHIKOKU]: 1 ♂, Mt. Odami,
Ehime Pref., 11-13. vi. 1981, S. Naomi leg. [KYUSHU]: 1 ♂1 ♀, Kueyama, Shimabara, Nagasaki Pref., 27. iii. 1979, S. Imasaka leg.; 1 ♂, Senbuki, Shimabara, Nagasaki Pref., 2. xi. 1977, S.
Imasaka leg.; 1 ♂1 ♀, same locality, 21. iv. 1977, S. Imasaka leg.; 2 ♀, Yokogawa, Naokawamura, Oita Pref., 29. iii. 1985, S. Sasaki leg.; 1 ♀, Mt. Tatsuda, Kumamoto C., Kumamoto Pref.,20. v. 1061, H. Aramaki leg.; 1 ♀, Miike, Mt. Kirishima, Kagoshima Pref., 8. v. 1985, S. Nomura
leg.; 1 ♀, Nakatane-cho, Tane Is., Kagoshima Pref., 9-12. v. 1996, M. Maruyama leg. [CHINA]:
1 ♂ (cS), China, Gansu, Dalijia Shan, 46 km W Linia, 2980 m, 10. vii. 1994, A. Smetana leg.; 1 ♀
(cS), China, Shaanxi, Qiniing Shan above Houzhenn 115 km WSW Xiʼan, 1450 m, 5. vii. 2001,
A. Smetana leg.
Distribution. Japan (Hokkaido, Honshu, Shikoku, Kyushu; Oki Isls, Tane Is.); Korea, Taiwan, China, Mongolia, Russia.
Redescription. Male and female: Macropterous; body 4.4–5.6 mm (fore-body 2.0–2.6 mm) in
length, elongate. Body black, with metallic reﬂection; elytra each with a yellowish spot; labrum
black; antennae reddish brown; legs yellowish brown to reddish brown. Head concave betweeneyes, with median longitudinal keel short, very narrow; punctures round to elliptical, dense tovery dense, small, distinct. Pronotum with surface weakly uneven, with a median fovea behindthe middle; punctures very dense, small, rough. Elytra with surface weakly uneven; puncturesround to elliptical, very dense, various in size. Legs relatively long, slender; 4th tarsomere sim-

The Steninae of Japan Part 1

57

ple. Abdomen narrowed posteriorly, well convex above; punctures round to elliptical, moderately
dense, small and distinct in anterior segments, while punctures in posterior segments round to
elliptical, very small, and regular. Lateroventrites ventromesial in position, wide, covered usuallywith small punctures (but sometimes also with large ones).
Male: Fifth ventrite posteromedially with a semicircular ﬂat area; 6th ventrite (Fig. 18G)
posteromedially with a shallow depression, which is very shallowly emarginate; 7th ventrite(Fig. 18G) posteromedially with a very deep, large depression (or cliff), which is arcuately emarginate, and also medially with a large, shallow depression which is contiguous with the posteromedian depression; 8th ventrite (Fig. 18D) posteriorlly with a broad emargination; 9th tergum(Fig. 18B) with ventral apophyses thin, moderately long; 9th ventrite (Fig. 18A) emarginate andﬁnely serrate posteriorly, with apicolateral setae short; 10th tergum (Fig. 18B) entire. Aedeagal
median lobe (Fig. 18C) broad, distinctly angulate at apicolateral corners which each has a small
hump, subtriangular behind the apicolateral corners, acutely pointed apically. Endophallic
median longitudinal bands (Fig. 18C) moderately long, relatively narrow, ventral bands only
covered with dot-like sculptures; expulsion hooks fused to form a nearly heart-shaped sclerite
which is emarginate posteriorly; basal tube (Fig. 18C) with sclerotized part of basal room composed of two shafts of different length, basal constriction distinct, tube body arrowhead-shaped;
cloak-like sclerite as in Fig. 18C. Parameres (Fig. 18C) almost straight, each pointed apically;
apical area long, furnished mesially with 20 to 23 setae mostly of short length.
Female: Eighth ventrite entire; gonocoxites (Fig. 18E) each almost rounded apicolaterally,
distinctly serrate posteriorly, with apicolateral setae long to very long. Spermatheca not observable.
Biology and ecology. S. alienus is one of the commonest Stenus species in Japan; and it is
widely distributed in the plains and low and relatively high mountainous regions. The beetles arefound of semi-arid grounds in open ﬁelds or grass lands, or at stony riverbanks; and they often
walk around there. They inhabit semi-arid grounds at the crop or cultivated ﬁelds; and they also
lives in somewhat dried grass litter heaped at the grasslands or open ﬁelds.
Remarks. Stenus alienus is allied to S. biguttatus, but it is separable from the latter by thelegs paler in color (yellowish brown to reddish brown), the subtriangular apical part of aedeagal
median lobe longer (Fig. 18C), the endophallic cloak-like sclerite structured as in Fig. 9F. See
Puthz (2008b: 177; Figs. 4–9) regarding variation of the setation of aedeagal parameres in S. alienus.
Stenus anthracinus Sharp(Figs. 19A–G, 127J)
Stenus anthracinus Sharp, 1889: 326; Herman, 2001: 2059; Puthz, 2001c: 42; Naomi & Puthz,
2013: 137.
Stenus yanoi Sawada & Nakane, 1954: 8.
Type material examined. Syntypes: 2 ♀ (NHML), type localities: Oyama, Kashiwagi. [examined by Puthz in 1965].
Other material examined. [HONSHU]: 1 ♂, Mt. Atsumi, Yamagata Pref., 4. v. 1962, Y. Watanabe leg.; 1 ♂, same locality, 29. iv. 1962, Y. Watanabe leg.; 1 ♀, same locality, 3. v. 1968, Y.
Watanabe leg.; 2 ♀, same locality, 1. v. 1989, Y. Watanebe leg.; 1 ♂, same locality, 4. v. 1994, Y.
Watanabe leg.; 1 ♂1 ♀, same locality, 7. viii. 1997, Y. Watanabe leg.; 1 ♂, Mt. Banzan, Sendai,

58

Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

Fig. 19. Stenus anthracinus Sharp (A–D, Ohto, Wakayama; E, F, Myoko, Niigata; G, Renge, Niigata). A,
aedeagus; B, 9th and 10th terga of male; C, 9th ventrite of male; D, endophallic cloak-like structure; E, apexof gonocoxite; F, 6th to 7th ventrites of male; G, apex of 8th ventrite of male. Scale 1: 0.2 mm for A–C, G, 0.1
mm for D, E; scale 2: 0.3 mm for F.

The Steninae of Japan Part 1

59

Miyagi Pref., 20. iii. 1996, H. Yoshitake leg.; 1 ♀, Mt. Abukuma, Fukushima Pref., 5. v. 1984, S.
Ohmomo leg.; 3 ♂4 ♀, Sasagamine, Mt. Myoko, Niigata Pref., 14-15. vi. 1980, S. Naomi leg.:2 ♂1 ♀, Renge Spa., Niigata Pref., 20. viii. 1986, M. Sato leg.; 1 ♀, Mt. Nyugasa, Nagano Pref.,13. viii. 1978, M. Sato leg.; 2 ♀, Mt. Hongu, Aichi Pref., 19. ix. 1978, M. Sato leg.; 1 ♀,Marunuma, Nikko, Tochigi Pref., 4-5. vii. 1982, S. Naomi leg.; 1 ♂, Wasabi-zawa, Okuchichibu,
Saitama Pref., 31. vii. 1986, K. Nemoto leg.; 1 ♂, Hirayu, Gifu Pref., 7-9. vi. 1980, S. Naomi
leg.; 1 ♂1 ♀, Hohare Pass, Gifu Pref., 5. v. 1986, K. Suzuki leg.; 5 ♂, Mizune-zawa, Okutama,
Tokyo, 2. v. 1980, Y. Watanabe leg.; 1 ♂1 ♀, Mt. Takao, Tokyo, 26. viii. 1978, M. Tao leg.; 1 ♀,same locality, 1. v. 1984, M. Tao leg.; 1 ♀, same locality, 6. vii. 1985, M. Tao leg.; 1 ♀, Yahatamura, Mie Pref., 9. viii. 1954, Z. Naruse leg.; 2 ♂2 ♀, Mt. Ohto, Wakayama Pref., 28-29. vi.
1981, S. Naomi leg.; 2 ♀, Onzui, Hyogo Pref., 6. vi. 1984, S. Nomura leg.; 2 ♂1 ♀, Urahikimi,
Shimane Pref., 5. vi. 1988, S. Nomura leg.; 3 ♂, Nakatsuya, Yoshiwa-mura, Hiroshima Pref., 7.
vi. 1987, S. Nomura leg. [SHIKOKU]: 2 ♂, Mt. Shiratsue, Ehime Pref., 11. vi. 1972, S. Kinoshita
leg.; 1 ♂1 ♀, Komenono, Matsuyama, Ehime Pref., 25. iv. 1993, L. Li leg.; 1 ♂, Narukawa,
Hiromi, Ehime Pref., 5. v. 1992, M. Sakai leg. [KYUSHU]: 1 ♀, Kikuchi Valley, Kumamoto
Pref., 11. iv. 1981, S. Naomi leg.; 1 ♂, Eadagouchi, Taraki-cho, Kumamoto Pref., 8. ix. 1992, M.
Sakai leg.; 1 ♂, Hagi, Gokanosho, Kumamoto Pref., 11. v. 1982, S. Imasaka leg.; 1 ♂, Kureko,
Gokanosho, Kumamoto Pref., 26. vii. 1962, H. Aramaki leg.; 1 ♀, Mt. Ichifusa, Kumamoto Pref.,1-2. viii. 1988, S. Naomi leg.
Distribution. Japan (Hokkaido?, Honshu, Shikoku, Kyushu); China.
Redescription. Male and female: Macropterous; body 4.3–5.6 mm (fore-body 2.3–2.5 mm) in
length, elongate. Body black, moderately shining; labrum black; antennae dark red; legs black
but tibiae and tarsi often dark red. Head moderately concave between eyes, with median longitudinal keel short, very narrow; punctures round to elliptical, moderately dense to dense, distinct.
Pronotum with surface weakly uneven; punctures elliptical to round, very dense, distinct, andarranging almost transversely near anterior and posterior margins. Elytra well convex above,with surface weakly uneven; punctures round, very dense, various in size, somewhat rough. Legs
slender; 4th tarsomere simple. Abdomen narrowed posteriorly, well convex above; puncturesround to elliptical, moderately dense to dense, various in size, and somewhat irregular in anterior
segments, while punctures in posterior segments round to elliptical, very small and regular. Lateroventrites ventromesial in position, moderately wide, punctate.
Male: Third to 5th ventrites each glabrous on posteromedian area; 6th ventrite (Fig. 19F)
posteromedially with a semicircular depression, which is very shallowly emarginate; 7th ventrite(Fig. 19F) posteromedially with a large, deep and semicircular depression, which is arcuately
emarginate, and also with a shallow, large depression on center, which is contiguous with theposteromedian depression; 8th ventrite (Fig. 19G) posteriorly with a very large, wide V-shaped
emargination; 9th tergum (Fig. 19B) with ventral apophyses long; 9th ventrite (Fig. 19C) elongate, rounded apicolaterally, shallowly emarginate and also ﬁnely serrate posteriorly, with apicolateral setae short; 10th tergum (Fig. 19B) very weakly emarginate. Aedeagal median lobe (Fig.
19A) broad, distinctly angulate at apicolateral corners which each has a small hump or tooth,
subtriangular behind the apicolateral corners, and pointed apically, with apical sclerotized area
covered with ﬁne pores. Endophallic median longitudinal bands (Fig. 19C) short, only ventral
bands covered with dot-like sculptures; expulsion hooks (Fig. 19A) fused to form a nearly heartshaped sclerite; basal tube (Fig. 19A) with sclerotized part of basal room composed only of left
shaft, basal constriction distinct, tube body arrowhead-shaped; cloak-like sclerite as in Fig. 19D.
Parameres (Fig. 19A) long, each rounded apically; stem thin, straight; apical area long, weakly

60

Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

swollen mesially, furnished mesially with 14 to 17 moderately long to long setae, and also mostapically with 3 to 4 very long setae which turn posteriorly.
Female: Eighth ventrite posteromedially obtuse; gonocoxites (Fig. 19E) each distinctly serrate posteriorly, with apicolateral setae very long. Spermatheca not observable.
Biology and ecology. Stenus anthracinus is distributed in the mountainous regions in Japan.
The beetles inhabit moist or wet leaf litter heaped in the vicinity of mountain torrents; and theyalso live in moist litter in natural forests.
Remarks. Stenus anthracinus is closely allied to S. puthzorum, but it is separable from thelatter by the body narrower, the head with longer median longitudinal keel between eyes, thepunctures on elytra simply dense and somewhat rough, the punctures on abdomen distinctly
sparser, the posteromedian depressions on the 7th and 8th ventrites of male smaller and shallower (Fig. 19F), and the aedeagal median lobe broader, with a small hump at the apicolateralcorner (Fig. 19A).
Stenus alienoides was ﬁrst described from Takesaki, Taiwan by Puthz (1981b); and this species is separable from S. anthracinus by the body more strongly shining, the apical triangularpart of aedeagal median lobe narrower and longer, etc. However, S. alienoides is considered avicarient species of S. anthracinus in Taiwan; and the record of S. alienoides from Okitsu, Japanin Puthz (2008b) be regarded as the record of S. anthracinus.
Stenus puthzorum Naomi & Watanabe(Fig. 20A–F)
Stenus puthzorum Naomi & Watanabe, 2015: 95.
Type material examined. Holotype: ♂ (TUAA), Kurokawa, N-Echigo, Niigata Pref., 16. ix.
1960, K. Baba leg.
Distribution. Japan (Honshu: Niigata Pref.).
Redescription. Male: Macropterous; body 5.2 mm (fore-body 2.6 mm) in length, elongate.
Body black, moderately shining, with metallic reﬂection; antennae black with 3rd to 5th segments dark red; legs black except for dark red tibiae. Head deeply concave between eyes, withmedian longitudinal keel short, very narrow; punctures round to elliptical, very dense, small, distinct. Pronotum with surface weakly uneven; punctures very dense, small, rough, sometimes two
or more punctures fused to form a large one. Elytra well convex above, with surface weakly
uneven; punctures round, very dense, moderately large, but punctures on anteromedian areas ofelytra elliptical to elongate ovoidal, almost arranged from anteromedian to posterolateral direction. Legs relatively slender; 4th tarsomere simple. Abdomen narrowed posteriorly, well convex
above; punctures round, dense, small and distinct in anterior segments, while punctures in posterior segments round to elliptical, very small and regular. Lateroventrites ventromesial in position,wide, covered with large punctures.
Third to 4th ventrites each glabrous on posteromedian area; 5th ventrite posteromedially witha ﬂat, glabrous area which is very weakly emarginate; 6th ventrite (Fig. 20B) posteromediallywith a semicircular depression, which is arcuately emarginate; 7th ventrite (Fig. 20B) posteromedially with a very large, deep and semicircular depression, which is arcuately emarginate, andalso with a shallow, round depression on center, which is contiguous with the posteromedian
depression; 8th ventrite (Fig. 20D) posteromedially with a large, semicircular emargination; 9th
tergum (Fig. 20E) with ventral apophyses long, straight; 9th ventrite (Fig. 20C) elongate,

The Steninae of Japan Part 1

Fig. 20. Stenus puthzorum Naomi & Watanabe (Kurokawa, Niigata). A, aedeagus; B, 6th to 7th ventrites ofmale; C, 9th ventrite of male; D, apex of 8th ventrite of male; E, 9th and 10th terga of male; F, endophallic
basal tube. Scale 1: 0.2 mm for A, C, D, E, 0.1 mm for F; scale 2: 0.3 mm for B.

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Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

rounded and also very ﬁnely serrate apicolaterally, emarginate posteriorly, with stem subtriangular in shape, apicolateral setae moderately long; 10th tergum (Fig. 20E) entire. Aedeagal median
lobe (Fig. 20A) relatively narrow, acutely angulate apicolaterally, almost triangular behind theapicolateral corners; apical sclerotized area almost covered with small pores. Endophallic medianlongitudinal bands (Fig. 20A) short, broad, without dot-like sculptures on anterior and anterolateral parts; expulsion hooks fused to form a Y-shaped sclerite; basal tube (Fig. 20A) robust, basal
room almost membranous (Fig. 20F), with left shaft sclerotized, tube body arrowhead-shaped.
Parameres (Fig. 20A) thin, slender; apical area long, furnished mesially with 19 to 20 setae ofmoderate length, and also most apically with 2 to 3 very long setae.
Female: Unknown.
Biology and ecology. Only one male individual of Stenus puthzorum is presently collectedfrom the mountainous region of central Honshu. No data on the habitats of this species are
obtained.
Remarks. Stenus puthzorum is closely allied to S. anthracinus but it is clearly distinguishable
from the latter by the body broader, entirely with silvery reﬂection, the head with shorter andthinner median longitudinal keel between eyes, the punctures on the anteromedian areas of elytra
almost arranged from anteromesial to posterolateral direction, the punctures on abdomen distinctly denser, the posteromedian depressions on the 6th and 7th ventrites larger and deeper (Fig.
20B), and the aedeagal median lobe narrower, without small hump at the apicolateral corner (Fig.
20A).
Etymology. This species is named in honour of Dr. Volker Puthz and Mrs. Marianne Puthz.
Stenus kobensis Cameron(Figs. 21A–H, 127K)
Stenus kobensis Cameron, 1930: 205; Herman, 2001: 2247; Naomi & Puthz, 2013: 137.
Type material examined. Syntypes (NHML), type locality: Kobe, Cascade Valley [examinedby Puthz in 1965].
Other material examined. [HOKKAIDO]: 5 ♂3 ♀, Sekihoku Pass, 27. viii. 1977, M. Satoleg.; 1 ♀, Mt. Kariba, Shiribeshi, 12. vi. 1986, S. Nomura leg.; 2 ♀, same locality, 13. vi. 1986, S.
Nomura leg.; 1 ♂1 ♀, Rausu River, 6. vii. 1986, S. Nomura leg.; 1 ♂, Toyohira Valley, Sapporo
C., 8. ix. 1978, H. Detani leg.; 1 ♂1 ♀, Toyohira River above Jyozankei, 4. v. 1973, Bauman &Kumata leg. (cP, USNM). [HONSHU]: 2 ♀, Okuyagen, Shimokita Peninsula, Aomori Pref., 2.
viii. 1987, S. Nomura leg.; 2 ♂1 ♀, Oirase River, Shiragami, Aomori Pref., 8. viii. 1987, S.
Nomura leg.; 1 ♀, Kuzukawa, Aomori Pref., x. 1958 (Mus. Prague); 1 ♀, Kawara-bo, Mt. Hayachine, Iwate Pref., 22-24. vi. 1980, S. Naomi leg.; 3 ♂, Tohgatta, Miyagi Pref., 19. viii. 1977, M.
Sato leg.; 1 ♂1 ♀, Futakuchi, Miyagi Pref., 20. viii. 1977, M. Sato leg.; 1 ♂, Funamata-zawa,
Fukushima Pref., 9. viii. 1977, H. Akiyama leg.; 1 ♀, Sanbo River, Lake Road, Fukushima Pref.,5. v. 1973, Bauman & Kohno (USNM); 1 ♂1 ♀, Sasagamine, Mt. Myoko, Niigata Pref., 14-15.
vi. 1980, S. Naomi leg.; 1 ♀, Renge Spa., Niigata Pref., 20. viii. 1986, M. Sato leg.; 1 ♀, Nakubusa, Nagano Pref., 21-25. viii. 1961, K. Mizusawa leg. (Genf); 2 ♂3 ♀, same locality, 3. viii.
1986, S. Morita leg. (DEI); 1 ♂, Tochu-dani nr. Nat. Cons. Entre, Mt. Hakusan, 1. ix. 1980, P.
Zwick leg.; 1 ♀, Mittani-dani nr. Ichimose, Mt. Hakusan, 2. ix. 1980, P. Zwick leg.; 1 ♀, Todai,
Nagano Pref., 7. v. 1977, M. Tao leg.; 1 ♂, Oppara, Gifu Pref., 15. vi. 1978, M. Sato leg.; 1 ♀,Jigoku-dani, Mt. Yatsu, Yamanashi Pref., 8. vii. 1982, S. Naomi leg.; 1 ♀, Oku-nikko, Nerazawa,

The Steninae of Japan Part 1

Fig. 21. Stenus kobensis Cameron (A, C, D, Ichihara, Chiba; B, E, G, Aso, Kumamoto; F, Oppara, Gifu; H,
Kamisaibara, Okayama). A, aedeagus; B, 9th ventrite of male; C, endophallic basal tube; D, endophallic
cloak-like structure; E, 9th and 10th terga of male; F, apex of 8th ventrite of male; G, 7th ventrite of male; H,
gonocoxite. Scale 1: 0.2 mm for A, B, H, 0.1 mm for C, D; scale 2: 0.2 mm for E, F; scale 3: 0.3 mm for G.

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Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

Tochigi Pref., 8. ix. 1937, Y. Yano leg. (NHML); 1 ♂, Chuzenji, Nikko, Tochigi Pref., v. 1908
(Mus. Paris); 1 ♀, Tochiyori-zawa, Okutama, Tokyo, Ishikawa leg. (Coll Coiffait, Mus. Paris);
1 ♂, Yoro Valley, Ichihara City, Chiba Pref., 9. v. 1993, K. Ohgi leg.; 2 ♂, Tanzawa, Kanagawa
Pref., 31. viii. 1986, M. Tao leg.; 1 ♀, Gora, Hakone, 17. viii. 1939, S. Suenson leg. (Mus.
Copenhagen); 1 ♂, Mt. Hongu, Aichi Pref., 1. vi. 1956, M. Sato leg.; 1 ♂, Mt. Hongu, Aichi Pref.,18. vi. 1961, Watanabe leg. (Genf); 1 ♂5 ♀, Mt. Daiki, Kyoto, 22. vi. 1951, Y. Wada leg.
(NHMW; SMNS); 2 ♂3 ♀, Mt. Ohto, Wakayama Pref., 28-29. vi. 1981, S. Naomi leg.; 2 ♂,Tamagawa Valley, Kii-nyu River, Wakayama Pref., 9. vi. 2012, P. Zwick leg.; 1 ♂, Onzui, Hyogo
Pref., 6. vi. 1984, S. Nomura leg.; 3 ♀, Gozaisho, Mie Pref., 13. iv. 1956, M. Sato leg.; 1 ♂, same
locality, 28. iii. 1954, M. Sato leg.; 1 ♂, same locality, 9. x. 1954, M. Sato leg.; 1 ♂, Asake, Mie
Pref., vi. 1965, M. Sato leg.; 1 ♂, Okame, Mie Pref., 6. iv. 1944, K. Moribe leg.; 1 ♂, Mt. Daisen,
Tottori Pref., 3-5. vi. 1980, S. Naomi leg.; 1 ♀, Tsuwano, Shimane Pref., 30 x. 1956, T. Wasaki(cHromádka); 1 ♂1 ♀, Nakatsuya, Yoshiwa-mura, Hiroshima Pref., 7. vi. 1987, S. Nomura leg.;1 ♀, Kami-saibara, Okayama Pref., 10. x. 1977, M. Kaneda leg. [SHIKOKU]: 1 ♀, Omogokei,
Iyo, Ehime Pref., 22. viii. 1953, RT. Edashige leg.; 1 ♂, Mt. Ishizuchi, Ehime Pref., 5. vi. 1952,
Y. Wada leg. (NHMW); 3 ♂1 ♀, Mt. Odami, Ehime Pref., 11-13. vi. 1981, S. Naomi leg.; 3 ♂,same locality, 21. vii. 1979, M. Sato leg. [KYUSHU]: 2 ♂, Kachigi, Naokawa-mura, Ohita Pref.,25. iv. 1986, S. Sasaki leg.; 2 ♂, Mt. Kyogatake, Saga Pref., 24. iv. 1987, S. Nomura leg.; 1 ♂,Kugino, Mt. Aso, Kumamoto Pref., 25. vi. 1961, H. Aramaki leg.; 1 ♀, Mt. Ichifusa, Mizukamimura, Kumamoto Pref., 8. vi. 1967, S. Hisamatsu leg.
Distribution. Japan (Hokkaido, Honshu, Shikoku, Kyushu; Oki Isls.).
Redescription. Male and female: Macropterous; body 4.6–5.9 mm (fore-body 2.6–3.2 mm) in
length, elongate. Body black, moderately shining, with metallic reﬂection; labrum and legs
black; antennae dark red. Head deeply concave between eyes, with median longitudinal keel
short, narrow; punctures round, dense, small, distinct. Pronotum with surface weakly uneven,with a distinct or indistinct median longitudinal depression; punctures elliptical to round, very
dense, distinct. Elytra large, well convex above, with surface weakly uneven; punctures round to
elliptical, very dense, distinct. Legs slender; 4th tarsomere simple. Abdomen narrowed posteriorly, well convex above; punctures round, moderately dense to dense, and small in anterior segments, while punctures in posterior segments round to elliptical, small (but sometimes verysmall), and regular. Lateroventrites ventromesial in position, wide, punctate.
Male: Seventh ventrite (Fig. 21G) posteromedially with a shallow, bell-shaped depression,
which is arcuately emarginate; 8th ventrite (Fig. 21F) posteriorly with a very large, wide
V-shaped emargination; 9th tergum (Fig. 21E) with ventral apophyses long; 9th ventrite (Fig.
21B) relatively wide, rounded apicolaterally, ﬁnely serrate posteriorly, with apicolateral setae
long; 10th tergum (Fig. 21E) entire. Aedeagal median lobe (Fig. 21A) elongate, shortly projecting laterally at apicolateral corners, elongate-subtriangular behind the apicolateral corners, withapical sclerotized area covered with moderately dense pores which each has a short but relatively
thick seta. Endophallic median longitudinal bands (Fig. 21A) with ventral bands short, strongly
sclerotized, covered with dot-like sculptures, dorsal bands being rather large and wide in such a
way that they dorsally wrap the basal tube; expulsion hooks (Fig. 21A) fused to form a sclerite
whose posterior margin is straight; basal tube rather complex in structure as in Fig. 21C, apicalbeak-shaped area connected with lateral twig-like sclerites by membranes; cloak-like sclerite as
in Fig.21D. Parameres (Fig. 21A) slender, not reaching posteriorly the apex of median lobe, eachrounded apically; apical area short, a little wide, furnished with about 10 setae of various length
along its mesial margin.

The Steninae of Japan Part 1

65

Female: Eighth ventrite obtusely pointed posteromedially; gonocoxites (Fig. 21H) eachrounded apicolateraly, serrate both posteriorly and mesially, with apicolateral sete very long.
Spermatheca not observable.
Biology and ecology. S. kobensis is a common Stenus species in Japan; and it is widely distributed in the mountainous regions. The beetles inhabit moist or wet leaf litter heaped in thevicinity of mountain torrents; and they also live in moist litter in natural forests.
Remarks. Stenus kobensis is allied to S. anthracinus and S. puthzorum, but it is separablefrom the latter two species by the body larger, the pronotum with the median longitudinal depression, the punctures on posterior abdominal segments similar in size to those on the anterior segments, the 6th and 7th ventrites of male only weakly modiﬁed (Fig. 21G), the gonocoxite serrate
both posteriorly and mesially (Fig. 21H), the aedeagal median lobe slenderer, with the moreelongate apical triangular area behind apicolateral corners (Fig. 21A); the paramere apicomesially with shorter setae (Fig. 21A), and endophallic basal tube unique in structure as in Fig. 21C.
Species group of S. seminiger Champion
S. seminiger group consists of 1 species in Japan; see Puthz (2013: 1298, 1447) regarding thetaxonomic information of this group. Diagnostic characters are as follows: Legs with 4th tarsomere simple; lateroventrites ventromesial in position, moderately broad; 9th tergum with a cleaning comb at posterior margin (Fig. 22E); 9th ventrite of male with apicolateral teeth, macrosetae
missing (Fig. 22B); aedeagal median lobe narrow, with apicomedian projection (Fig. 22C); endophallus with a cloak-like sclerite which partially covers the basal tube (Fig. 22C); gonocoxitewith apicolateral tooth (Fig. 22D); spermatheca not observable.
Stenus macies Sharp(Figs. 22A–H, 127L)
Stenus macies Sharp, 1874: 83; Herman, 2001: 2268; Puthz, 2008b: 187; Naomi & Puthz, 2013:
137.
Type material examined. Holotype: ♂ (NHML), type locality: Nagasaki [examined by Puthz
in 1969].
Other material examined. [HOKKAIDO]: 1 ♂, Shinnosuke-Sannosawa, Mitsumata,Kamishihoro, 12. vii. 1994, K. Miyashita leg.; 1 ♀, Kamisenkyo, Kamiiso-cho, 16. viii. 1997, M.
Nishikawa leg.; 2 ♂, Sounkyo, 26. vii. 1963. Y. Shibata leg. [HONSHU]: 1 ♂, Mt. Kumano,
Miyagi Pref., 24. viii. 1978, M. Sato leg.; 1 ♂, Toubaku-zawa, Oku-chichibu, Saitama Pref., 5. vi.
1986, K. Nemoto leg.; 1 ♀, Mt. Nasu, Tochigi Pref., 3. vi. 1994, S. Naomi leg.; 1 ♀, Kirizumi
Spa., Gunma Pref., 7. vi. 1986, M. Tao leg.; 1 ♀, Okutama, Tokyo, 7. vii. 1986, M. Tao leg.; 2 ♂,Sato-Kurosaki, Mikura Is., Izu Isls., 6. vi. 1996, S. Naomi et M. Maruyama leg.; 1 ♂, Fuji-rindo,
Yamanashi Pref., 4. ix. 1977, K. Kawada leg.; 1 ♂1 ♀, Mt. Fuji, Yamanashi Pref., 18. vi. 1978,
M. Tao leg.; 2 ♂, Daibosatsu, Yamanashi Pref., 22-23. vi. 1985, M. Sato leg.; 1 ♀, Nirazaki City,
Yamanashi Pref., 15. vii. 1993, K. Hosoda leg.; 1 ♂, Tamodani, Izumi-mura, Fukui Pref., 5. v.
1982, H. Sasaji leg.; 1 ♀, Satsura-dani, Izumi-mura, Fukui Pref., 2. viii. 1981, H. Sasaji leg.; 1 ♂,Mt. Hino, Fukui Pref., 5. v. 1975, H. Sasaji leg.; 1 ♀, Mt. Ibuki, Shiga Pref., 9. vii. 1977, Y. Horileg.; 1 ♂1 ♀, Mt. Gomanodan, Wakayama Pref., 22-23. vi. 1981, S. Naomi leg.; 1 ♀, Mt. Takahachi, Tottori Pref., 4. vii. 1976, S. Naomi leg.; 1 ♀, Mt. Dainanji, Dogo Is., Oki Isls., 18-25. v.

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Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

Fig. 22. Stenus macies Sharp (A–C, F–H, Tamodani, Fukui; D, Takahachi, Tottori; E, Kamishihoro, Hokkaido).
A, 5th to 7th ventrites of male; B, 9th ventrite of male; C, aedeagus; D, apex of gonocoxite; E, 9th and 10th
terga of male; F, apex of 8th ventrite of male; G, endophallic structures; H, endophallic basal tube. Scale 1:
0.3 mm for A; scale 2: 0.2 mm for B, C, E, F, 0.1 mm for D, G, H.

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67

2004, T. Shimada leg.; 1 ♀, Kabura-sugi, Saigô-cho, Dôgo Is., Oki Isls., 17. vii. 2003, T. Shimada leg.; 1 ♀, Shinrin Park, Okayama Pref., 18. vi. 1978, M. Kaneda leg. [SHIKOKU]: 1 ♂,Minokoshi, Mt. Tsurugi, Tokushima Pref., 15. vii. 1984, M. Sakai leg.; 1 ♀, Ochiai Pass,
Tokushima Pref., 31. vii. 1976, M. Kaneda leg.; 1 ♀, Mt. Ishizuchi, Ehime Pref., 16. vi. 1981, S.
Naomi leg.; 1 ♂, Komenono, Ehime Pref., 7. vi. 1976, M. Sakai leg. [KYUSHU]: 1 ♂, Mt. Hiko,
Fukuoka Pref., 8. viii. 1977, S. Naomi leg.; 1 ♂, Tashirobaru, Nagasaki Pref., 21. iv. 1977, S.
Imasaka leg.; 1 ♂, Senbuki, Shimabara, Nagasaki Pref., 22. viii. 1977, S. Imasaka leg.; 1 ♀, Mt.
Unzen, Nagasaki Pref., 1. iii. 1977, S. Imasaka leg.; 1 ♀, Mayuyama, Shimabara, Nagasaki Pref.,1. x. 1977, S. Imasaka leg.; 1 ♀, Shimoda, Amakusa Is., Kumamoto Pref., 7. viii. 1977, H. Ohishi
leg.; 1 ♀, Shiratani, Yaku Is., Kagoshima Pref., 13. vii. 1984, M. Tao leg.; 1 ♂, Koseta, Yaku Is.,
Kagoshima Pref., 23. xi. 1984, S. Morita leg.; 1 ♀, Ookawa, Yaku Is., Kagoshima Pref., 12. vii.
1973, O. Yamaji leg.
Distribution. Japan (Hokkaido, Honshu, Shikoku, Kyushu; Sado Is., Miyake Is., Mikura Is.,
Hachijo Is., Oki Isls., Tsushima Is., Yaku Is.); China.
Redescription. Male and female: Macropterous; body 3.8–5.2 mm (fore-body 1.9–2.4 mm) in
length, elongate, moderately shining. Head and abdomen black; pronotum and elytra dark red toblack; labrum black; antennae dark red to black; legs reddish brown through dark red to black.
Head moderately concave between eyes, with median longitudinal area (demarcated laterallywith furrows) almost ﬂat; punctures round to elliptical, dense, distinct. Pronotum with surface
weakly uneven, without median longitudinal depression nor fovea; punctures elliptical to round,very dense, somewhat rough. Elytra with surface weakly uneven; punctures round, very dense,
distinct. Legs moderately long; 4th tarsomere simple. Abdomen weakly convex above; puncturesround, dense to very dense, and small in anterior segments, while punctures in posterior segments very round to elliptical, small, and regular. Lateroventrites ventromesial in position, punctate.
Male: Fourth ventrite posteromedially with a semicircular ﬂat area which is very weakly
emarginate; 5th ventrite (Fig. 22A) posteromedially with a large, shallow semicircular depression, which is very weakly emarginate; 6th ventrite (Fig. 22A) posteromedially with a very large,
moderately deep semicircular depression, which is arcuately emarginate; 7th ventrite (Fig. 22A)
medially with a very large, elongate-subovoidal depression, which is deep or very deep behindthe middle and is arcuately emarginate; 8th ventrite (Fig. 22F) posteromedially with a shallow,
arculate emargination; 9th tergum (Fig. 22E) with ventral apophyses short, moderately thick; 9th
ventrite (Fig. 22B) ﬁnely serrate posteriorly, with apicolateral teeth pointed, apicolateral setae
moderately long to long; 10th tergum (Fig. 22E) elongate, entire. Aedeagal median lobe (Fig.
22C) elongate, almost parallel-sided, rounded apicolaterally, with the relatively long, apicomedian projection; apical sclerotized area long, with very thin, longitudinal linear sculptures andvery ﬁne, sporadical pores. Endophallic median longitudinal bands (Fig. 22C) with ventral bands
more located mesially than dorsal bands, both dorsal and ventral bands covered with dot-like
sculptures; expulsion hooks (Fig. 22C) separated each other, each broad-bean-shaped, submembranous except for lateral rims which are partially sclerotized (Fig. 22G); basal tube almost beakshaped, structured as in Fig. 22G, H; cloak-like sclerite as in Fig. 22G. Parameres (Fig. 22C)
slender, thin, almost straight, each rounded apically; apical area short, furnished mesially with 8
to 9 short to moderately long setae.
Female: Eighth ventrite obtusely pointed posteromedially; gonocoxites (Fig. 22D) each posteriorly with 2 or 3 teeth, apicolateral tooth large, pointed, apicolateral setae very long. Spermatheca not observable.

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Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

Biology and ecology. Stenus macies is widely distributed in the plains and mountainous
regions in Japan; it also lives in such small islands as Miyake and Yaku. The beetles inhabit leaf
litter heaped around or in natural forests.
Remarks. Stenus macies is allied to S. yanoianus Puthz, 1980b from Taiwan and S. fraterculus Puthz, 1980b from China, but it is separable from the latter two species by the legs paler incolor (reddish brown through dark red in usual) and the aedeagal median lobe slender, almost
parallel-sided (Fig. 22C).
There are paired plates in the endophallus of S. seminiger group (i.e., S. macies: Fig. 22G;
see also Puthz, 1971a: 80; 2008b: 187). At ﬁrst glance they are not expulsion hooks because of
the following three reasons: First, they are positioned near the basal tube; second, they aremostly submembranous; and third, in its related species group (e.g., S. comma group), the expulsion hooks are commonly fused to form an arrow-headed sclerite. However, they are considered
the expulsion hooks, given that they are dorsal in position relative to the median longitudinalbands.
Species group of S. clavicornis (Scopoli)
S. clavicornis group consists of 15 species in Japan; and see Puthz (1988a, 2013) for a characterization of this group. Diagnostic characters are as follows: Legs with 4th tarsomere simple;
abdomen with 3rd to 6th terga each with 3 basal longitudinal keels (Fig. 128A); lateroventrites
existing in 4th to 6th segments except for two species (S. takedai and S. laborator); 9th ventriteof male with pointed apicolateral teeth, macrosetae missing (Fig. 28C); aedeagal median lobe
elongate, with its apical part various in shape (bilobed as in Fig. 28B; truncate apically as in Fig.
31A; rounded as in Fig. 33A; spatulate as in Fig. 37B, etc.); expulsion hooks only partially (Fig.
23F) or completely (Fig. 31D) fused, various in shape; gonocoxite with pointed apicolateral
tooth (Fig. 23G); spermatheca not observable.
Key to the Japanese species of S. clavicornis group1(26) Abdomen with laterotergites existing in 4rd to 6th segments; aedeagal median lobe withbasal area well developed, longer before basal foramen (Fig. 29B).
2(9) Legs unicolorous (dark red to black).
3(4) Body larger (5.2–6.0 mm; fore-body: 2.7–3.0 mm); 6th ventrite of male posteromediallywith a longitudinal keel (Fig. 23A); aedeagus as in Fig. 23D ........................... S. juno Paykull
4(3) Body smaller (2.9–4.5 mm; fore-body: 1.6–2.4 mm); 6th ventrite of male posteromediallywithout longitudinal keel.
5(8) Body larger (4.1–4.5 mm; fore-body: 2.0–2.4 mm); depression on the 7th ventrite of malewith its lateral ridges not parallel.
6(7) Body narrower, with elytra smaller (head width/elytral width ＜0.90); pronotum without distinct microscupture; lateroventrites with coarse, moderately dense punctures; 6th ventrite ofmale very weakly projecting posteriorly at posteromedian part (Fig. 25D); 7th ventrite ofmale posteromedially with an ovoidal, shallow depression (Fig. 25D); aedeagus as in Fig.
25C .................................................................................................................S. yamato Naomi
7(6) Body broader, with elytra larger (head width/elytral width ＜0.85); pronotum withdeep microsculpture; lateroventrites with less coarse, dense punctures; 6th ventrite of maleposteromedially with very weak, shallow emargination (Fig. 26C); 7th ventrite of male pos-

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69

teromedially with a moderately deep, subtrapezoidal depression, (Fig. 26C); aedeagus as inFig. 26A.......................................................................................................... S. lewisius Sharp
8(5) Body smaller (2.9–4.0 mm; fore-body: 1.6–2.1 mm); depression on the 7th ventrite of malewith its lateral ridges running almost parallel (Fig. 30E); aedeagus as in Fig. 30B........................................................................................................... S. amurensis Eppelsheim
9(2) Legs bicolorous (yellowish brown to reddish brown, with knees infuscate).
10(13) Body larger (5.5–7.0 mm; fore body: 2.8–3.0 mm).
11(12) Body with abdomen broader, less strongly cylindrical (Fig. 128B); head with vertex only
weakly concave, with its median portion about as high as mesial eye margin; 4th laterotergite distinctly broader than breadth of 2nd antennal segment, coarsely, densely punctate; 5th and 6th ventrites of male each with paired setal bands (Fig. 24A); aedeagus as inFig. 24D ..........................................................................................S. indagator Eppelsheim
12(11) Body with abdomen narrower, more strongly cylindrical (Fig. 128L); head with vertex
deeply concave, with its median portion distinctly lower in level than mesiall eye margin;
4th lateroventrite narrower than breadth of 2nd antennal segment, impunctate; 5th and 6th
ventrites of male each without setal bands (Fig. 34D); aedeagus as in Fig. 34B.............................................................................................................S. formosanus Benick
13(10) Body smaller (3.5–5.7 mm; fore body: 1.9–2.5 mm).
14(19) Lateroventrites broader; 4th lateroventrite about as broad as length of 2nd antennal segment.
15(18) Smaller species (3.6–5.2 mm; fore body: 1.9–2.2 mm); interstices between puncturessmooth on abdomen.
16(17) Fifth and 6th ventrites of male without modiﬁcation; aedeagus as in Fig. 27B.............................................................................................................. S. katoi Naomi & Ito
17(16) Fifth ventrite of male posteromedially with a semicircular ﬂat area or shallow depression;
6th ventrite of male posteromedially with a shallow, bell-shaped depression (Fig. 28E);
aedeagus as in Fig. 28B .........................................................................S. sauteri Bernhauer
18(15) Larger species (5.0–5.7 mm; fore body: 2.1–2.5 mm); interstices between punctures covered with reticulated microsculpture on abdomen; 5th ventrite of male without modiﬁcation; 6th ventrite of male posteromedially only with a ﬂat area (Fig. 35A); aedeagus as inFig. 35B. ...........................................................................................S. clavicornis (Scopoli)19(14) Lateroventrites narrower; 4th lateroventrite more or less shorter than length of 2nd antennal segment.
20(21) Lateroventrites horizontal (or sometimes dorsomesial) in position; abdomen with punctures smaller, sparser, interstices between punctures much larger than half diameter ofpunctures in the middle of anterior terga; 6th and 7th ventrites of male each posteromedially with a larger depression (Fig. 29A); aedeagus as in Fig. 29B....... S. nishikawai Naomi
21(20) Lateroventrites dorsomesial (or sometimes horizontal) in position; abdomen with punctures larger, denser, interstices between punctures distinctly smaller than half diameter ofpunctures in the middle of anterior terga; abdominal ventrites with different modiﬁcations; aedeagi different in structure.
22(23) Seventh tergum with punctures smaller, less dense, interstices between punctures larger
than diameter of punctures; 4th and 5th ventrite of male without modiﬁcation; aedeagus
as in Fig. 32E.........................................................................................S. disterminus Puthz
23(22) Seventh tergum with punctures larger, denser, interstices between punctures smaller thandiameter of punctures; 4th and 5th ventrites of male with modiﬁcation; aedeagi differently

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Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

structured.
24(25) Smaller species (3.9–5.1 mm; fore body 2.0–2.3 mm); abdomen with interstices between
punctures smooth; 6th ventrite of male posteromedially with a larger ﬂat area; aedeagus
as in Fig. 31A ...............................................................................................S. distans Sharp
25(24) Larger species (body 5.0–5.2 mm; fore body 2.3–2.4 mm); abdomen with interstices
between punctures covered with reticulated microsculpture; 6th ventrite of male posteromedially with a smaller ﬂat area (Fig. 33C); aedeagus as in Fig. 33A...................................
............................................................................................................S. calliceps Bernhauer
26(1) Abdomen with laterotergites missing in 4th to 6th segments; legs unicolorous (yellowish
brown to reddish brown); aedeagal median lobe with basal area weakly developed, shorter
before basal foramen (Fig. 37B).
27(28) Body thinner, more strongly shining, with elytra narrower, abdomen slenderer (Fig.
129B); punctures on abdominal terga sparser, smaller; aedeagus as in Fig. 36B ..................
....................................................................................................................S. takedai Naomi
28(27) Body thicker, less strongly shining, with elytra broader, abdomen thicker (Fig. 129C);
punctures on the abdominal terga denser and larger; aedeagus as in Fig. 37B ......................
..................................................................................................................S. laborator Sharp
Stenus juno Paykull(Figs. 2aB, 23A–G, 128A)
Stenus juno Paykull, 1789: 33; Naomi, 1991: 165; Herman, 2001: 2240; Puthz, 2001c: 42;
Naomi & Puthz, 2013: 137.
Type material. Type locality: Suecia.
Other material examined. [HOKKAIDO]: 1 ♂1 ♀, Ootsu, Toyokoro-cho, 24. vi. 1993, K.
Miyashita leg.; 3 ♀, same locality, 13. vii. 1992, K. Haga leg.; 2 ♂, Memanbetsu-cho, 6. vii.
1993, T. Kato leg.; 1 ♀, Shirautoro Lake, Kushiro, 11. vi. 1990, R. Kuranishi leg.; 1 ♀, Hyotan
Pond, Akan N.-P., 4. vii. 1986, S. Nomura leg.; 1 ♂, Mokoto, Abashiri, 10. vii. 1958, T. Nakaneleg. [HONSHU]: 1 ♀, Urabandai, Fukushima Pref., 9. vii. 1985, K. Konishi leg.; 1 ♀, Yunoko
Lake, Oku-Nikko, Tochigi Pref., 29. vii. 1999, V. Puthz leg.; 6 ♂1 ♀, Marunuma Lake, Gunma
Pref., 30. vii. 1954, K. Sawada leg.; 2 ♀, Saikawabashi, Akashima-cho, Nagano Pref., 5. iv. 1993,
S. Nomura leg.
Distribution. Japan (Hokkaido, Honshu: Tohoku, Kanto and Chubu districts); China, Russia,
Azerbaijan, Europe, Canada, USA.
Redescription. Male and female: Macropterous; body 5.2–6.0 mm (fore-body 2.7–3.0 mm) in
length, robust; paraglossae ovoidal (Fig. 2aB). Body black, with metallic reﬂection; labrum
black; antennae with 1st segment black, 2nd to 11th segments dark red; legs with femora black,tibiae and tarsi dark red. Head concave between eyes, with a pair of distinct longitudinal depressions; punctures round to elliptical, very dense, various in size, distinct. Pronotum with surface
weakly uneven, with an indistinct median longitudinal depression; punctures almost round, very
dense, somewhat rough. Elytra with surface weakly uneven; punctures round to elliptical, very
dense, somewhat rough and rugose. Legs relatively long; 4th tarsomere simple. Abdomen thick,subparallel-sided; 3rd to 6th terga each with 3 basal longitudinal keels; punctures almost round,moderately dense to dense, small and distinct in anterior segments, while punctures in posterior
segments sparse very, small and regular. Lateroventrites ventromesial in position, relatively nar-

The Steninae of Japan Part 1

Fig. 23. Stenus juno Paykull (A, B, D–F, Toyokoro, Hokkaido; C, Abashiri, Hokkaido; G, Akan, Hokkaido). A,
6th to 8th ventrites of male; B, 9th and 10th terga of male; C, 9th ventrite of male; D, aedeagus; E, aedeagal
paramere (lateral view); F, endophallic expulsion hook and basal tube; G, apex of gonocoxite. Scale 1: 0.3
mm for A, B; scale 2: 0.2 mm for C, D; scale 3: 0. mm for E, G, 0.1 mm for F.

71

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Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

row, densely punctate.
Male: Legs with femora rather thick; hind femur with the posteromedian part weakly angulate; middle tibia with the apicomesial part shortly pointed; 3rd ventrite posteromedially with asmall, round, shallow depression, whose posterior part only weakly projects posteriorly, and alsowith an indistinct, low median longitudinal keel on the depressed area; 4th ventrite posteromedially with a similar depression as in the 3rd, but the posterior margin almost straight and the
median longitudinal keel on the depressed area higher than that in the 3rd; 5th ventrite posteromedially with a small semicircular depression which is very weakly emarginate, the median longitudinal keel on the depression as high as that in the 4th; 6th ventrite (Fig. 23A) posteromediallywith a medium-sized, semicircular depression, which is very shallowly bi-emarginate posteriorly,
the median longitudinal keel on the depression a little higher than that in the 5th; 7th ventrite(Fig. 23A) posteromedially with a large, deep concavity, its lateral sides each with a high,hatchet-like projection, and a small, round notch existing at the posteromedian part of concavity,
the posteromedian concavity contiguous with the shallow anteromedian depression, median longitudinal keel on the anteromedian depression a little higher than that in the 6th; 8th ventrite(Fig. 23A) posteromedially with a narrow, V-shaped emargination, and medially with a large,
elongate-ovoidal depression; 9th tergum (Fig. 23B) with anterolateral ﬂaps large, ventral apophyses very large, spatulate, posterolateral projections reaching fully the posterior margin of 10th
tergum; 9th ventrite (Fig. 23C) elongate, angulate basilaterally, indistinctly serrate posteriorly,
with stem elongate, narrow, basilateral emarginations small, apicolateral teeth acutely pointed,
apicolateral setae moderately long; 10th tergum (Fig. 23B) rather small, entire. Aedeagal median
lobe (Fig. 23D) elongate, apically with a pair of lobes which each turn dorsally and are roundedapically. Endophallic median longitudinal bands (Fig. 23D) moderately long, with ventral bands
longer than dorsal bands which are truncate anteriorly; expulsion hooks fused to form a V-shapedsclerite (Fig. 23F) posteromedially with a deep, narrow emargination; basal tube (Fig. 23F) short,baculiform, turning dorsally. Parameres (Fig. 23D) narrow and incurved apically when seen ventrally, but rather broad when seen laterally (Fig. 23E); apical area rather long, wide, furnishedapicoventrally with about 30 setae of moderate length, also apicodorsally with a line of 9–10
very short setae.
Female: Eighth ventrite posteromedially with a very shallow emargination; gonocoxites (Fig.
23G) each with apicolateral tooth acutely pointed, apicolateral setae short to moderately long.
Spermatheca not observable.
Biology and ecology. Stenus juno is distributed in the low and high mountainous regions inJapan. The beetles inhabit moist litter heaped near the shores of rivers, lakes and marshes, andalso wet litter in the vicinity of running water.
Remarks. Stenus juno was ﬁrst recorded from Japan (Hokkaido) by Naomi (1991). This species is allied to S. calcaratus Scriba, 1864, but it is easily separable from the latter by the bodysmaller (5.2–6.0 mm), the elytra distinctly longer than prothorax, and the abdominal ventrites ofmale not furnished with suberect long setae (Fig. 23A).
Stenus indagator Eppelsheim(Figs. 24A–E, 128B)
Stenus indagator Eppelsheim, 1887: 428; Herman, 2001: 2230; Naomi & Puthz, 2013: 137.
Stenus lentus Sharp, 1889: 326.

The Steninae of Japan Part 1

73

Type material examined. Holotype of S. indagator: ♀ (NHMW), type locality: Wladiwostok[examined by Puthz in 1965]. Syntypes of S. lentus: 3 exs. (NHML), type locality: Nikko [examined by Puthz in 1967].
Other material examined. [HOKKAIDO]: 1 ♂, Kami-shihoro, 26. vi.−4. vii. 1989, K. Haga
leg.; 1 ♂, Memuro-cho, 15. ix. 1991, K. Ito leg.; 1 ♀, Tohro Lake, Kushiro, 27. vii. 1986, S.
Nomura leg. 1 ♀, Yunosawa, Memanbetsu-cho, 17. ix. 1992, T. Kato leg.
Distribution. Japan (Hokkaido, Honshu); China, Russia.
Redescription. Male and female: Macropterous; body 5.5–7.0 mm (fore-body 2.8–3.0 mm) in
length, robust, relatively broad. Head and abdomen black; pronotum and elytra dark red to black;labrum black; antennae dark red to black; legs yellowish brown to reddish brown, with knees andapical parts of tibiae more or less infuscate. Head concave between eyes, with the sides of vertex
impressed along mesial margins of eyes and with a pair of distinct longitudinal depressions,median part between the depressions moderately elevated; punctures round to elliptical, dense,
various in size, distinct. Pronotum well convex above, with surface very weakly uneven; punctures almost round, very dense, various in size. Elytra with surface weakly uneven; puncturesround to elliptical, very dense, large. Legs relatively long; 4th tarsomere simple. Abdomen relatively wide, weakly narrowed posteriorly; 3rd to 6th terga each with 3 basal longitudinal keels;punctures round, moderately dense to dense, and small in anterior segments, while punctures inposterior segments sparse, very small and regular. Lateroventrites ventromesial in position, wide,
punctate.
Male: Legs with femora rather thick; hind femur shallowly concave and pubescent at theposterior part of basal half; middle tibia with a spine at the apicomesial part; hind tibia compressed dorsoventrally, broadest a little behind the middle, with the mesial area shallowly, widely
concave; 3rd ventrite (Fig. 24A) posteromedially with a small, semicircular ﬂat area, a small tuftof short setae located at each side of the ﬂat area; 4th ventrite (Fig. 24A) posteromedially with amedium-sized, crescent depression, which is very weakly emarginate, and a medium-sized tuft oflong setae located at each side of the depression; 5th ventrite (Fig. 24A) posteromedially with amoderately deep, transverse depression which is emarginated posteriorly, a large setal band
located at each side of the depression; 6th ventrite (Fig. 24A) posteromedially with a very large,
semicircular concavity whose posterior margin is arcuate, a very large setal band located at eachside of the concavity, the posteromedian concavity continuous with the shallow, anteromedian
depression; 7th ventrite (Fig. 24A) medially with a very large, deep concavity, a triangular projection existing at its lateral side, which turns ventrally and is acutely pointed; 8th ventrite (Fig.
24A) posteromedially with a small, V-shaped emargination, and medially with a large, elongateovoidal depression; 9th tergum (Fig. 24B) with anterolateral ﬂaps subtriangular, ventral apophyses very large, wide; 9th ventrite (Fig. 24E) elongate, irregularly serrate posteriorly, with stem
elongate-triangular, pointed apically, basilateral processes small, rounded, apicolateral teeth
short, acutely pointed, apicolateral setae short; 10th tergum (Fig. 24B) entire. Aedeagal median
lobe (Fig. 24D) elongate, with a pair of apical lobes, each of which is round apically and furnished with 4 setae. Endophallic median longitudinal bands (Fig. 24D) with ventral bands each
long, thin, gently curved laterally, minutely incised at anterolateral part, dorsal bands each short,broad; expulsion hooks (Fig. 24D) fused to form a nearly M-shaped sclerite; basal tube (Fig.
24D) short, attenuate apically, with a rounded hump at the middle of its right side. Parameres(Fig. 24D) similarly structured as in S. juno; apical area furnished mesially with about 20 setae ofmoderate length, and also most apically with a tuft of dense setae.
Female: Eighth ventrite posteromedially with a very shallow emargination; gonocoxites (Fig.

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Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

Fig. 24. Stenus indagator Eppelsheim (A, B, D, E, Kamishihoro, Hokkaido; C, Kushiro, Hokkaido). A, 3rd to
8th ventrites of male; B, 9th and 10th terga of male; C, gonocoxite; D, aedeagus; E, 9th ventrite of male.
Scale 1: 0.4 mm for A; scale 2: 0.2 mm for B, D, E; scale 3: 0.2 mm for C.

The Steninae of Japan Part 1

7524C) each indistinctly serrate posteriorly, with apicolateral tooth pointed, apicolateral setae short
to moderately long. Spermatheca not observable.
Biology and ecology. S. indagator is a very rare and magniﬁcent Stenus species in Japan; andit is distributed in the low and high mountainous regions. The beetles inhabit moist litter locatednear the rivers, lakes and marshes.
Remarks. In Stenus indagator a regular line of very long, golden setae arise from the lateral
margin of depression in 5th and 6th ventrites; and they stick one another to form a band-likestructure (Fig. 24A). Thus, the setal modiﬁcation found in male is here called “setal band”. S.
indagator is allied to S. bimaculatus Gyllenhal, 1810, but it is easily separable from the latter by
the elytra unicolorous (dark red to black), without yellowish spots; and the paired “setal bands”
existing on the ventrites of male (Fig. 24A).
Stenus yamato Naomi(Figs. 25A–G, 128C)
Stenus yamato Naomi, 1988d: 57; Herman, 2001: 2230; Naomi & Puthz, 2013: 137.
Type material examined. Holotype: ♂ (KUF), Karikomi Pond, Koike, Fukui Pref., 19. vii.
1981, H. Sasaji leg. Paratypes: 1 ♂ (cN), Inayasu, Nagano Pref., 5. v. 1977, M. Tao leg.; 2 ♂
(cN), Sannomatadani, Fukui Pref., 4. vi. 1983, H. Sasaji leg.; 2 ♂1 ♀ (cN), Monomi Pass, Tanzawa Pref., Kanagawa Pref., 5. viii. 1978, M. Tao leg.
Other material examined. [HONSHU]: 2 ♂, Mt. Yakeishi, Iwate Pref., 3–4. viii. 1985, S.
Morita; 1 ♂, Genta-shimizu, Matsuo-mura, Iwate Pref., 10. ix. 1988, Y. Takanashi leg.; 3 ♂1 ♀,Hama River, Irihirose-mura, Niigata Pref., 10. vi. 1995, K. Haga leg.; 1 ♀, Marunuma, Gunma
Pref., 22. vi. 1982, S. Morita leg.; 1 ♂, Mt. Koya, Wakayama Pref., 7. vi. 1964, T. Ito leg.; 1 ♀,Mt. Koya, Kii, Wakayama Pref., 23. v. 1965, T. Ito leg.; 1 ♂, Mt. Kojin, Nara Pref., 17. vii. 1976,
T. Ito leg.; 1 ♀, same locality, 7. viii. 1966, T. Ito leg. [SHIKOKU]: 1 ♂, Komeno, Matsuyama
City, Ehime Pref., 4. v. 1991, I. Okamoto leg. [KYUSHU]: 1 ♂, Mt. Tara, Takaki-cho, Nagasaki
Pref., 3. vi. 2002, T. Watanabe leg.
Distribution. Japan (Honshu, Shikoku, Kyushu).
Redescription. Male and female: Macropterous; body 4.1–4.4 mm (fore-body 2.0–2.3 mm) in
length, elongate, shining. Body black; labrum, antennae and legs dark red to black. Head concave between eyes, with a pair of distinct longitudinal depressions; punctures round to elliptical,
moderately dense to very dense, various in size. Pronotum with surface weakly uneven, with an
indistinct median longitudinal depression; punctures round to elliptical, very dense, various in
size, somewhat rough. Elytra with surface weakly uneven; punctures round to elliptical, very
dense, sometimes rugose at sutural areas. Legs moderately long, relatively thin; 4th tarsomere
simple. Abdomen weakly narrowed posteriorly; 3rd to 7th terga each with 3 basal longitudinalkeels; punctures round, moderately dense to dense, small and distinct in anterior segments, while
punctures in posterior segments elliptical, sparse, very small and regular. Lateroventrites ventromesial in position, moderately wide, punctate.
Male: Fourth and 5th ventrites each posteromedially with a shining, semicircular ﬂat area,
which is very weakly emarginate; 6th ventrite (Fig. 25D) posteromedially with a semicircular,
shallow depression, which weakly, arcuately projects posteriorly, with setae along its lateral margin; 7th ventrite (Fig. 25D) posteromedially with an ovoidal, shallow depression, which is shallowly emarginate posteriorly and covered densely with setae at its lateral parts; 8th ventrite (Fig.

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Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

Fig. 25. Stenus yamato Naomi (A, B, Matsuo, Iwate; C, F, G, Komeno, Ehime; D, Tara, Nagasaki; E, Tanzawa,
Kanagawa). A, 9th and 10th terga of male; B, 9th ventrite of male; C, aedeagus; D, Sixth to 8th ventrites ofmale; E, apex of gonocoxite; F, endophallic basal tube; G, expulsion hook. Scale 1: 0.2 mm for A–C, 0.1 mm
for E, G; scale 2: 0.3 mm for D; scale 3: 0.2 mm for F.

The Steninae of Japan Part 1

7725D) posteromedially with a V-shaped emargination; 9th tergum (Fig. 25A) with anterolateral
ﬂaps subtriangular, ventral apophyses relatively short; 9th ventrite (Fig. 25B) angulate basilaterally, hardly serrate posteriorly, with stem elongate, thin, apicolateral teeth short, pointed, apicolateral setae moderately long; 10th tergum (Fig. 25A) very shallowly emarginate posteromedially. Aedeagal median lobe (Fig. 25C) moderately thick, with apical part wide, almost truncate orvery weakly emarginate. Endophallic median longitudinal bands (Fig. 25C) short, broad; expulsion hooks (Fig. 25C) fused by the posteromesial corner to form a sclerite as in Fig. 25G; basal
tube (Fig. 25C, F) robust, with basal room almost membranous, tube body very thick, spoonshaped. Parameres (Fig. 25C) each with stem thin, very weakly incurved when seen ventrally;
apical area long, thick, furnished mesially with 25 to 31 short setae, and also most apically with atuft of moderately long setae.
Female: Eighth ventrite posteromedially with a small, very shallow emargination; gonocoxites (Fig. 25E) each distinctly or indistinctly serrate posteriorly, with apicolateral tooth short,pointed, apicolateral setae moderately long. Spermatheca not observable.
Biology and ecology. Stenus yamato inhabits leaf litter in the natural forests of low and highmountainous regions, and also moist litter near the rivers and ponds.
Remarks. Stenus yamato is allied to S. lewisius, but it is separable from the latter by the bodymore slender (Fig. 128C), the elytra smaller, the 7th ventrite of male with posteromedian depression covered laterally with dense setae (Fig. 25D); the 8th ventrite of male with posteromedianemargination smaller (Fig. 25D); the aedeagal median lobe thicker, with its apical part almost
truncate or very weakly emarginate (Fig. 25C); and the endophallic basal tube thicker, withspoon-shaped tube body (Fig. 25F).
Etymology. The speciﬁc epithet is derived from one of the ancient Japanese names of“Japan”.
Stenus lewisius Sharp(Figs. 26A–H, 128D)
Stenus lewisius Sharp, 1874: 82; Herman, 2001: 2260; Puthz, 2001c: 43; Naomi & Puthz, 2013:137.
Stenus gatenpio Naomi, 1990d: 99.
Type material examined. Holotype (NHML), type locality: Mitzuyama, Nagasaki [examinedby Puthz].
Other material examined. [HOKKAIDO]: 1 ♂1 ♀, Sarobetsu, 24. viii. 1977, M. Sato leg.;1 ♀, Shibecha, 18. vi. 1976, M. Sato leg.; 1 ♀, Jozankei, 19. vi. 1976, M. Sato leg. [HONSHU]:
1 ♂2 ♀, Tohgatta, Miyagi Pref., 19. viii. 1977, M. Sato leg.; 1 ♀, Uenohara, Miyagi Pref., 20. viii.
1977, M. Sato leg.; 1 ♀, Yakurai Spa., Miyagi Pref., 21. viii. 1978, M. Sato leg.; 1 ♂2 ♀, Nuruyu,
Hanayama, Miyagi Pref., 6. viii. 1984, K. Morimoto leg.; 1 ♀, Kirizumi Spa., Gunma Pref., 7. vi.
1986, M. Tao leg.; 1 ♀, Urawa City, Saitama Pref., 23. ix. 1983, M. Tao leg.; 1 ♀, Kanso-numa,
Hikari-cho, Chiba Pref., 3. v. 2000, R. Kuranishi leg.; 1 ♀, Noborito, Kawasaki City, Kanagawa
Pref., 3. v. 1978, M. Tao leg.; 1 ♂1 ♀, same locality, 1. x. 1978, M. Tao leg.; 1 ♂1 ♀, Tama River,
Noborito, Kanagawa Pref., 25. ii. 1979, M. Tao leg.; 1 ♀, Tsurumi-ku, Yokohama City,
Kanagawa Pref., 26. ix. 1982, M. Tao leg.; 1 ♂, same locality 16. v. 1987, M. Tao leg.; 1 ♂, Toyota, Aichi Pref., 25. iv. 1976, M. Sato leg.; 1 ♂1 ♀, Sobue, Aichi Pref., 20. iv. 1975, M. Sato leg.;1 ♀, Mt. Daihi, Kyoto, 19. ix. 1981, T. Ito leg.; 1 ♂, Kasuga, Nara Pref., 20. iv. 1985, T. Ito leg.;

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Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

Fig. 26. Stenus lewisius Sharp (A–D, G, H, Sarobetsu, Hokkaido; E, Unagi-ike, Kagoshima; F, Shibecha, Hokkaido). A, aedeagus; B, 9th ventrite of male; C, 6th to 7th ventrites of male; D, apex of 8th ventrite of male;
E, 9th and 10th terga of male; F, apex of gonocoxite; G, endophallic basal tube; H, expulsion hook. Scale 1:
0.2 mm for A, B, D, 0.1 mm for F–H; scale 2: 0.3 mm for D; scale 3: 0.2 mm for E.

The Steninae of Japan Part 179

2 ♂2 ♀, Okayama City, Okayama Pref., 1. vi. 1977, Fukushima leg.; 1 ♂, Okutsu-cho, Okayama
Pref., 2. viii. 1977, M. Kaneda leg.; 2 ♂, Tsudaka-bokujyo, Okayama City, Okayama Pref., 14.
iii. 1977, Fukushima leg.; 1 ♂4 ♀, Nikyukyo, Kure City, Hiroshima Pref., 1. vi. 1985, I. Okamoto
leg. [SHIKOKU]: 2 ♂, Miyanotani Pond, Shikoku-chuo City, Ehime Pref., 30. x. 2005, Y. Katayama leg.; 2 ♀, same locality and date, T. Kurihara leg. [KYUSHU]: 1 ♂, Nishi-koganemaru,
Shima-cho, Fukuoka Pref., 16. viii. 1991, S. Nomura leg.; 1 ♂, Heiwadai, Fukuoka City,
Fukuoka Pref., 22. ix. 1991, S. Nomura leg.; 1 ♂, Kurusu River, Naokawa-mura, Oita Pref., 30.
x. 1984, K. Kazato leg.; 1 ♂, same locality, 31. x. 1984, S. Sasaki leg.; 1 ♂, Mt. Kurodake, Ooitagun, Ooita Pref., 9. v. 1982, S. Sasaki leg.; 1 ♂, same locality, 5. vii. 1982, S. Sasaki leg.; 1 ♀,Sannoh, Yamato-cho, Saga Pref., 24, iii. 1991, S. Nomura leg.; 1 ♂1 ♀, Mt. Unzen, Nagasaki
Pref., 15. xi. 1977, S. Imasaka leg.; 2 ♀, Kunimi-cho, Nagasaki Pref., 14. xi. 1980, S. Imasaka
leg.; 1 ♀, Shinyama, Ohmachi, Saga Pref., 29. iii. 1968, Y. Eguchi leg.; 1 ♂, Unagi-ike,
Kagoshima Pref., 18. v. 1986, M. Sato leg.
Distribution. Japan (Hokkaido, Honshu, Shikoku, Kyushu).
Redescription. Male and female: Macropterous; body 4.1–4.5 mm (fore-body 2.1–2.4 mm) in
length, elongate, weakly or moderately shining. Body black; labrum and antennae dark red; legs
black, sometimes with tibiae and tarsi dark red. Head relatively small, concave between eyes,with a pair of distinct longitudinal depressions; punctures round, dense to very dense, various in
size, distinct. Pronotum with surface weakly uneven; punctures round, very dense, various in
size, distinct. Elytra large, well convex above, with surface weakly uneven; punctures round,very dense, relatively small, deep, sometimes irregular. Legs relatively short; 4th tarsomere simple. Abdomen weakly narrowed posteriorly; 3rd to 7th terga each with 3 basal longitudinal keels;punctures round, moderately dense to dense, small, and distinct in anterior segments, while punctures in posterior segments round to elliptical, moderately dense, and very small. Lateroventrites
ventromesial in position, moderately wide, punctate.
Male: Sixth ventrite (Fig. 26C) posteromedially with a large, semicircular ﬂat area, which isvery weakly emarginate; 7th ventrite (Fig. 26C) posteromedially with a moderately deep, subtrapezoidal depression which is arcuately emarginate and is provided with a longitudinal ridgealong its lateral margin, and also centrally with a shallow depression, which is contiguous withthe posteromedian depression; 8th ventrite (Fig. 26D) posteromedially with a large, almost
V-shaped emargination; 9th tergum (Fig. 26E) with anterolateral ﬂaps subtriangular, ventral
apophyses short, thick; 9th ventrite (Fig. 26B) hardly or very ﬁnely serrate posteriorly, with stem
thin, slender, apicolateral teeth short, pointed, apicolateral setae long; 10th tergum (Fig. 26E)
small, entire. Aedeagal median lobe (Fig. 26A) slender, with its apical part rounded. Endophallic
median longitudinal bands (Fig. 26A) moderately long and wide, pointed apicolaterally; expulsion hooks (Fig. 26A) fused to form a sclerite as in Fig. 26H; basal tube (Fig. 26A) mediumsized, basal room ovoidal, with two thin shafts of different length, tube body simplely baculiform(Fig. 26G). Parameres (Fig. 26A) weakly curved laterally near the middle; apical area long, relatively thick, furnished with 14 to 16 setae along its mesial margin, and also most apically with 3
to 4 long setae.
Female: Eighth ventrite posteromedially with a small, very shallow emargination; gonocoxites (Fig. 26F) each with apicolateral tooth large, pointed, apicolateral setae long. Spermatheca
not observable.
Biology and ecology. S. lewisius is a common Stenus species in Japan; and it is widely distributed in the plains to low mountainous regions. The beetles inhabit semi-arid open areas suchas stony riverbanks; and they walk around the grounds and stones there.

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Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

Remarks. S. lewisius has been an East Asian Stenus species (Herman, 2001), but the Stenus
populations of China, Korea and Russia, which were previously regarded as S. lewisius, are presently considered to be S. lewisius pseudoater Bernhauer, 1938a by Puthz (2013a). Thus, the nominotypical subspecies S. lewisius is indigenous in Japan. S. lewisius is allied to S. yamato, but it isseparable from the latter by the body wider (Fig. 128D), the elytra larger, the 7th ventrite of malewith posteromedian depression hardly covered laterally with setae (Fig. 26C), the 8th ventrite ofmale with posteromedian emargination larger (Fig. 26D), the aedeagal median lobe thinner, with
its apical part round (Fig. 26A), and the endophallic basal tube smaller, with tube body simplely
baculiform (Fig. 26G).
Etymology. This species was named in honour of Mr. George Lewis, England, the collectorof the type material of this species.
Stenus katoi Naomi & Ito(Figs. 27A–G, 128E)
Stenus katoi Naomi & Ito, 2015b: 225.
Type material examined. Holotype: ♂ (OMNH), Kayamura, Shibecha-cho, Hokkaido, 5. viii.
2013, T. Kato leg. Paratypes: 1 ♂1 ♀ (cN), 1 ♂1 ♀ (cI), 1 ♂ (cP), same data as holotype; 1 ♀ (cP),Musa River, Kushiro, Hokkaido, 11. vi. 2010, K. Matsumoto leg.
Distribution. Japan (Hokkaido).
Redescription. Male and female: Macropterous; body 4.7–5.2 mm (fore body 2.0–2.2 mm) in
length, moderately shining. Body black; labrum and antennae dark red to black; legs reddish
brown to dark reddish brown, with knees infuscate. Head concave between eyes, partially,
weakly impressed just along mesial margins of eyes, with a pair of longitudinal depressions;punctures round to elliptical, dense to very dense, various in size. Pronotum with surface weakly
uneven; punctures round, very dense, various in size. Elytra with surface very weakly uneven;punctures round, very dense. Legs moderately long; tibiae thin; 4th tarsomere simple. Abdomen
relatively wide, weakly convex dorsally; 3rd to 6th terga each with 3 basal longitudinal keels;punctures round, sparse small and distinct in anterior segments, while punctures in posterior segments sparse, very small and regular. Lateroventrites ventromesial in position, wide, punctate.
Male: Seventh ventrite (Fig. 27E) posteromedially with a bell-shaped depression, which isarcuately emarginate; 8th ventrite (Fig. 27E) posteromedially with a relatively small, V-shaped
emargination; 9th tergum (Fig. 27A) with ventral apophyses moderately long, posterolateral projections very acute; 9th ventrite (Fig. 27C) indistinctly serrate posteriorly, with stem relatively
narrow, apicolateral teeth acutely pointed, apicolateral setae moderately long; 10th tergum (Fig.
27A) entire. Aedeagal median lobe (Fig. 27B) narrowed apically, very weakly, distinctly constricted just before the apex, which is almost truncate but very shallowly emarginate medially.
Endophallic median longitudinal bands (Fig. 27B) with ventral bands each very long, strongly
curved laterally a little before the middle, dorsal bands each very broad, weakly broadened anteriorly, truncate anteriorly; expulsion hooks (Fig. 27B) fused to form a transverse sclerite as inFig. 27D; basal tube (Fig. 27B) with basal room ovoidal, submembranous, franked dorsally witha pair of board-like sclerites, tube body short, pincer-like in structure (Fig. 27F). Parameres (Fig.
27B) each very weakly sinuous when seen ventrally; apical area long, relatively thick, furnishedmesially with 35 to 46 dense setae.
Female: Eighth ventrite entire but sometimes posteromedially with a very small, shallow

The Steninae of Japan Part 1

Fig. 27. Stenus katoi Naomi & Ito (Shibecha, Hokkaido). A, 9th and 10th terga of male; B, aedeagus; C, 9th ventrite of male; D, expulsion hook; E, 7th to 8th ventrites of male; F, endophallic basal tube; G, apex of gonocoxite. Scale 1: 0.2 mm for A–C, G, 0.1 mm for D, F; scale 2: 0.3 mm for E.

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Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

emargination; gonocoxites (Fig. 27G) each indistinctly serrate posteriorly, with apicolateral toothacutely pointed, apicolateral setae moderately long. Spermatheca not observable.
Biology and ecology. Stenus katoi was recently discovered from Hokkaido by Naomi & Ito(2015b), suggesting that it may be a rare species. It is distributed only in the plains of the easternpart of Hokkaido. The beetles inhabit moist leaf litters of the grasslands and natural forests
located near the rivers and lakes.
Remarks. Stenus katoi is closely allied to S. sauteri, but it is separable from the latter by thelegs darker in coloration (reddish brown to dark reddish brown), the 5th and 6th ventrites of malewithout modiﬁcation, the aedeagal median lobe a little wider, with its apex very shallowly emarginate (Fig. 27B), and the endophallic expulsion hooks fused to form a wider, transverse sclerite(Fig. 27D).
Etymology. This species was named in honour of Mr. T. Kato (Hokkaido), a collector of thetype material of this species.
Stenus sauteri Bernhauer(Figs. 28A–G, 128F)
Stenus sauteri Bernhauer, 1907: 379; Herman, 2001: 2379; Puthz, 2012a: 156; Naomi & Puthz,
2013: 137.
Type material examined. Holotype: ♂, paratype 1 ♀ (FMC), type locality: Kanagawa [examined by Puthz in 1967].
Other material examined. [HOKKAIDO]: 1 ♂, Higashi-ohnuma, Nanae, Oshima, 14. vi.
1986, S. Nomura leg.; 2 ♀, same locality, 16. vi. 1986, S. Nomura leg.; 1 ♀, Wakoto, Teshikagacho, 29. iv. 2008, T. Kato leg.; 1 ♀, Kushiro Marsh, Tsurui, Onʼnenai, 27. viii. 1990, M. Sakai
leg.; 1 ♀, Bekanbeushi Marsh, Akkeshi-cho, 9. vii. 2004, R. Matsumoto leg.; 1 ♀, Tohro Lake,
Kushiro, 27. vii. 1986, S. Nomura leg.; 1 ♀, Tohutsu, Tokoro, Kitami City, 3. vi. 2008, T. Katoleg.; 1 ♀, Otadomari Pond, Rishiri Is., 28. vi. 1986, S. Nomura; 1 ♀, Barato, Ishikari, 8. viii.
1977, N. Nishikawa leg.; 1 ♂1 ♀, Koshimizu, Shari, 28. v. 2013, T. Kato leg. [HONSHU]: 1 ♂,Tonaka River, Yuzawa-cho, Niigata Pref., 13. v. 1995, K. Haga leg.; 1 ♂1 ♀, Uono River, Kawaguchi-cho, Niigata Pref., 30. iv. 1995, K. Haga leg.; 1 ♀, Renge Spa., Niigata Pref., 20. viii.
1986, M. Sato leg.; 2 ♂3 ♀, Estuary of Abe River, Suruga-ku, Shizuoka City, Shizuoka Pref., 16.
vii. 2007, T. Shimada leg.; 1 ♀, Mt. Mitake, Tokyo, 26. vi. 1977, M. Tao leg.; 1 ♂, Machida City,
Tokyo, 5. iv. 1987, M. Tao leg.; 1 ♂, Segami, Yato, Enkaizan, Yokohama, Kanagawa Pref., 10. xi.
1993, H. Watari leg.; 1 ♀, Edo River, Ichikawa City, Chiba Pref., 11. v. 1991, T. Takeda leg.; 1 ♂,Suiseki-bashi, Noda City, Chiba Pref., 12. xi. 1990, T. Takeda leg.; 2 ♂, Kitasuga, Narita City,
Chiba Pref., 25. iii. 1990, T. Takeda leg.; 2 ♂1 ♀, Tega-numa Lake, Sakura City, Chiba Pref., 8. x.
1998, T. Shimada leg. [SHIKOKU]: 3 ♂4 ♀, Akui River, Nakaʼakui, Tokushima Pref., 15. viii.
1988, M. Sakai leg.; 1 ♂, Shigenobu River, Masaki-cho, Ehime Pref., 25. viii. 1993, I. Okamotoleg.; 1 ♀, Estuary of Shigenobu River, Ehime Pref., 3. viii. 1993, M. Sakai leg. [KYUSHU]:
Hazama, Ohita Pref., 5. xi. 1985, A. Miyata leg. [KOREA]: 1 ♀, Yusung, Taejon, Chʼungchʼongnam-do, Korea, 5. viii. 1997, M. Nishikawa leg.
Distribution. Japan (Hokkaido, Honshu, Shikoku, Kyushu); Korea, Russia.
Redescription. Male and female: Macropterous; body 3.6–5.2 mm (fore body 1.9–2.2 mm) in
length, moderately shining, with antennae moderately long, slender. Head and abdomen black;pronotum and elytra dark red; labrum dark red; antennae dark red except for the 1st segments

The Steninae of Japan Part 1

Fig. 28. Stenus sauteri Bernhauer (A, C–E, Oshima, Hokkaido; B, F, Noda, Chiba; G, Akui, Tokushima). A, 9th
and 10th terga of male; B, aedeagus; C, 9th ventrite of male; D, endophallic expulsion hook; E, 6th to 8th
ventrites of male; F, basal tube; G, apex of gonocoxite. Scale 1: 0.2 mm for A–C, 0.1 mm for D, F, G; scale 2:
0.3 mm for E.

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which are black; legs yellowish brown to reddish brown, with knees infuscate. Head concave
between eyes, partially, weakly impressed along mesial margins of eyes, with a pair of longitudinal depressions; punctures round to elliptical, dense to very dense, various in size. Pronotumwith surface almost even; punctures round, very dense, various in size, distinct. Elytra with surface almost even; punctures round, very dense, distinct. Legs moderately long; tibiae thin; 4thtarsomere simple. Abdomen a little wide, weakly convex dorsally; 3rd to 6th terga each with 3basal longitudinal keels; punctures round, sparse, small and distinct in anterior segments, while
punctures in posterior segments sparse, very small and regular. Lateroventrites ventromesial in
position, wide, punctate.
Male: Fifth ventrite posteromedially with a semicircular ﬂat area or shallow depression,
which is sometimes very weakly emarginate posteriorly; 6th ventrite (Fig. 28E) posteromediallywith a bell-shaped, shallow depression; 7th ventrite (Fig. 28E) posteromedially with a subtrapezoidal depression, which is emarginate posteriorly and strongly polished; 8th ventrite (Fig. 28E)
posteromedially with a V-shaped emargination; 9th tergum (Fig. 28A) with ventral apophyses
moderately long, broad, posterolateral projections very acute; 9th ventrite (Fig. 28C) elongate,
weakly serrate posteriorly, with stem elongate-triangular in shape, pointed apically, apicolateral
teeth acutely pointed, apicolateral setae moderately long; 10th tergum (Fig. 28A) almost entire.
Aedeagal median lobe (Fig. 28B) slender, with a short, fan-shaped apex, which is furnished laterally with 2 or 3 very short setae. Endophallic median longitudinal bands (Fig. 28B) with ventral
bands very long, almost straight, dorsal bands rather broad, much shorter than ventral bands;
expulsion hooks fused to form a stout sclerite (Fig. 28D); basal tube (Fig. 28B) with basal room
elongate-ovoidal, submembranous only in anterior part, comprising posteriorly paired sclerotizedshafts, basal constriction distinct, tube body pincer-shaped (Fig. 28F). Parameres (Fig. 28B)
weakly sinuous when seen ventrally; apical area long, moderately thick, furnished mesially with
16 to 17 (mostly) short setae, and also most apically with 4 or 5 moderately long setae.
Female: Eighth ventrite rounded posteriorly; gonocoxites (Fig. 28G) each irregularly serrate
posteriorly, with apicolateral tooth long, acutely pointed, apicolateral setae long. Spermatheca
not observable.
Biology and ecology. S. sauteri is a common Stenus species in Japan; and it is widely distributed in the plains and low mountainous regions. The beetles usually inhabit moist litter of thegrasslands and natural forests located near the rivers, lakes and marshes (e.g., litter of reed growing near the marsh).
Remarks. Stenus sauteri is closely allied to S. katoi, but it is separable from the latter by thelegs righter in coloration (yellowish brown to reddish brown), the 5th and 6th ventrites of malewith modiﬁcations described above (Fig. 28E); the aedeagal median lobe a little narrower, with
its apex almost fan-shaped (Fig. 28B), the expulsion hooks fused to form a narrower, stout sclerite (Fig. 28D).
Etymology. This species was named in honour of Mr. Hans Sauter (München), the collectorof the type material of this species.
Stenus nishikawai Naomi(Figs. 29A–F, 128G)
Stenus nishikawai Naomi, 1988d: 58; Herman, 2001: 2301; Naomi & Puthz, 2013: 137.
Type material examined. Holotype: ♂ (KUF), Higashi-ohnuma, Nanae, Oshima, Hokkaido,

The Steninae of Japan Part 1

85

14. vi. 1986, S. Nomura leg. Paratypes: 1 ♀ (cN), Higashi-ohnuma, Nanae, Oshima, Hokkaido,
14. vi. 1986, S. Nomura leg.; 1 ♀ (cN), same locality, 15. vi. 1986, S. Nomura leg.; 1 ♀ (cN), Mt.
Hakken, Hokkaido, 25. v. 1977, N. Nishikawa leg.; 1 ♂ (cN), Nogi-cho, Tochigi Pref., 10. x.
1977, M. Tao leg.
Other material examined. [HOKKAIDO]: 2 ♂9 ♀, Ohnuma, Nanae-cho, Oshima, 9. ix. 1994,
T. Kishimoto leg.; 1 ♂, Oikawanai, Taiki, 23. v. 1993, K. Shibata leg. [HONSHU]: 1 ♂, Ominesan, Gunma Pref., 11. iv. 1954.
Distribution. Japan (Hokkaido, Honshu, Kyushu?).
Redescription. Male and female: Macropterous; body 3.5–4.3 mm (fore body 1.9–2.2 mm) in
length, moderately shining, with antennae moderately long, slender. Head and abdomen black;pronotum and elytra dark red; labrum and antennae dark red to black; legs yellowish brown toreddish brown, with knees infuscate. Head with a pair of longitudinal depressions; puncturesround to elliptical, dense to very dense, distinct. Pronotum with surface weakly uneven; punctures round to elliptical, dense to very dense. Elytra with surface weakly uneven; puncturesround, dense to very dense, sometimes two punctures partially fused. Legs moderately long; tarsi
with 4th tarsomere simple. Abdomen subcylindrical, moderately convex dorsally; 3rd to 6th tergaeach with 3 basal longitudinal keels; punctures round, moderately dense and rather ﬁne in anterior segments, while punctures in posterior segments sparse, very small and regular. Lateroventrites horizontal or ventromesial in position, relatively narrow, punctate.
Male: Legs with femora relatively thick; 4th ventrite posteromedially with a medium-sized,
ﬂat area; 5th ventrite (Fig. 29A) posteromedially with a semicircular, ﬂat area, which is furnishedwith a line of setae along each lateral side; 6th ventrite (Fig. 29A) posteromedially with a large,
semicircular depression, which is very weakly emarginate posteriorly and furnished with a lineof long to very long setae at each lateral side; 7th ventrite (Fig. 29A) posteromedially with a verylarge, deep concavity, which is largely, arcuately emarginate posteriorly and is also furnished laterally with a line of moderately long setae; 8th ventrite (Fig. 29A) posteromedially with aV-shaped emargination, and anteromedially with a large depression, which becomes broader
anteriorly (to the extent to ﬁt the breadth of posteromedian emargination of 7th ventrite) and also
becomes a little deeper anteriorly; 9th tergum (Fig. 29D) with ventral apophyses short to moderately long, posterolateral projections long, very acute; 9th ventrite (Fig. 29C) elongate, weakly
serrate posteriorly, with stem elongate-hexagonal in shape, basilateral emarginations relatively
small, apicolateral teeth short, acutely pointed, apicolateral setae long; 10th tergum (Fig. 29D)
very weakly emarginate posteromedially. Aedeagal median lobe (Fig. 29B) strongly bulbous
basally, then strongly narrowed apically, with its apex almost truncate or weakly arcuate, very
weakly swollen laterally, and also furnished with 2 or 3 short setae at each side. Endophallic
median longitudinal bands (Fig. 29B) with ventral bands each moderately long, pointed apically,
dorsal bands each short, rounded apically; lateral longitudinal bands (Fig. 29B) very thin; expulsion hooks (Fig. 29B) connected by posteromesial corner, each short, almost rounded anteriorly;
basal tube (Fig. 29B) with basal room ovoidal, submembranous, franked posterolaterally withpaired short shafts, tube body baculiform, asymmetrically bifurcate at apex, ventrally with accessory structure which is thin and pincer-like (Fig. 29F). Parameres (Fig. 29B) relatively short; apical area distinctly swollen mesially, furnished mesially with 21 to 23 moderately long setae, andalso most apically with 3 or 4 long setae which turn posteriorly.
Female: Eighth ventrite obtusely angulate posteromedially; gonocoxites (Fig. 29E) eachindistinctly serrate posteriorly, with apicolateral tooth long, acutely pointed, apicolateral setae
long. Spermatheca not observable.

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Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

Fig. 29. Stenus nishikawai Naomi (Nanae, Hokkaido). A, 5th to 8th ventrites of male; B, aedeagus; C, 9th ventrite of male; D, 9th and 10th terga of male; E, apex of gonocoxite; F, endophallic basal tube. Scale 1: 0.3 mm
for A; scale 2: 0.2 mm for B–D, 0.1 mm for E, F.

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87

Biology and ecology. Stenus nishikawai is distributed in the plains and low mountainous
regions. No ecological data are obtained, but the collecting records suggest that the beetles are
litter inhabitants.
Remarks. Stenus nishikawai is allied to S amurensis, but it is separable from the latter by thelegs lighter in coloration (yellowish brown to reddish brown), the hind femur without modiﬁcation in male, the 7th ventrite of male with posteromedian concavity deeper and more deeply
emarginate (Fig. 29A), the 8th ventrite of male with posteromedian emargination narrower (Fig.
29A), and the endophallic basal tube body asymmetrically bifurcate apically (Fig. 29F).
Etymology. This species was named in honour of Mr. Naomi Nishikawa (Sapporo), a collector of the type material of this species.
Stenus amurensis Eppelsheim(Figs. 30A–G, 128H)
Stenus amurensis Eppelsheim, 1886: 43; Naomi & Puthz, 1994a: 219; Naomi & Puthz, 1996:
160; Herman, 2001: 2055; Naomi & Puthz, 2013: 137.
Type material examined. Holotype: ♀ (NHMW), type locality: Blagowestschensk [examinedby Puthz in 1965].
Other material examined. [HOKKAIDO]: 6 ♂2 ♀, Chitose Lake, Chitose City, 6. vi. 1999,
M. Maruyama leg.; 1 ♂, Echigo Lake, Ebetsu City, 29. iv. 1999, M. Maruyama leg.; 3 ♀, same
locality, 2. vi. 1999, M. Maruyama leg.; 1 ♂, same locality, 23. vi. 1993, K. Miyashita leg.;1 ♂1 ♀, Kimonto Pond, Taijyu-machi, 23. vi. 1993, K. Miyashita leg.; 2 ♀, Hyotan Pond, Akan
N. P., 4. vii. 1986, S. Nomura leg.; 1 ♂1 ♀, Otadomari-numa, Rishiri Is., 25. viii. 1993, T. Kishimoto leg.; 1 ♂, Kirakotan, Kushiro Moor, 25. viii. 1990, M. Sato leg.; 2 ♂, Oshimizu-cho, Nikuru-numa, 27. vii. 1993, K. Haga leg.
Distribution. Japan (Hokkaido); China, Mongolia, Russia, Kuriles (Iturup).
Redescription. Male and female: Macropterous; body 2.9–4.0 mm (fore body 1.6–2.1 mm) in
length, weakly to moderately shining, with antennae relatively short. Body black; labrum black;antennae with basal and apical segments black, middle segments dark red; legs dark red to black.
Head with a pair of longitudinal depressions; punctures elliptical, very dense, regular. Pronotumwith surface weakly uneven; punctures round, very dense, various in size. Elytra large, wellangulate at humeri, with surface weakly uneven; punctures round, very dense, distinct. Legs relatively short; tarsi with 4th tarsomere simple. Abdomen subcylindrical, weakly narrowed posteriorly; 3rd to 6th (or 7th) terga each with 3 basal longitudinal keels; punctures round, sparse andsmall in anterior segments, while in posterior segments punctures sparse, very small and regular.
Lateroventrites horizontal or ventromesial in position, punctate.
Male: Legs with femora thick; hind femur with a small tooth at the posterior side of the base;5th ventrite posteromedially with a small, semicircular ﬂat area, which is furnished with several
long setae at each lateral side; 6th ventrite (Fig. 30E) posteromedially with a large, semicircular
ﬂat area, which is very shallowly emarginate posteriorly and furnished with a line of long setae
along each lateral side; 7th ventrite (Fig. 30E) posteromedially with a large, deep depression,
which is emarginate posteriorly, distinctly ridged laterally, and also furnished laterally with a lineof setae; 8th ventrite (Fig. 30E) posteromedially with a wide, V-shaped emargination, and medially with a large depression which becomes broader and a little deeper anteriorly; 9th tergum(Fig. 30A) with ventral apophyses short, posterolateral projections long, very acute; 9th ventrite

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Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

Fig. 30. Stenus amurensis Eppelsheim (A, C, E, G, Taijyu, Hokkaido; B, D, F, Ebetsu, Hokkaido). A, 9th and10th terga of male; B, aedeagus; C, 9th ventrite of male; D, endophallic expulsion hook; E, 6th to 8th ventrites of male; F, basal tube; G, apex of gonocoxite. Scale 1: 0.2 mm for A–C, 0.1 mm for D, F, G; scale 2: 0.3
mm for E.

The Steninae of Japan Part 1

89(Fig. 30C) elongate, weakly serrate posteriorly, with stem elongate-hexagonal in shape, basilateral emarginations narrow, basilateral projections almost rounded anteriorly, apicolateral teeth
acutely pointed, apicolateral setae moderately long; 10th tergum (Fig. 30A) very weakly emarginate posteromedially. Aedeagal median lobe (Fig. 30B) strongly bulbous basally, and thenstrongly narrowed apically, its apex nearly short fan-shaped, with 4 or 5 short setae at each lateral corner. Endophallic median longitudinal bands (Fig. 30B) relatively wide, with ventral bands
each moderately long, curved laterally near the middle, ventral bands each short, straight; expulsion hooks (Fig. 30B) connected by posteromesial corner, each short, obstusely angulate anteriorly (Fig. 30D); basal tube (Fig. 30B) with basal room ovoidal, submembranous, franked posterolaterally with paired short shafts, tube body baculiform, thick, weakly thickened apically,swollen laterally at apex (Fig. 30F). Parameres (Fig. 30B) each with stem thin; apical area long,
distinctly widened dorsoventrally, furnished mesially with 35 to 45 moderately long, dense setae,
and also most apically with 5 or 6 long setae.
Female: Eighth ventrite rounded posteriorly; gonocoxites (Fig. 30G) each irregularly serrate
posteriorly, with apicolateral tooth large, acutely pointed, apicolateral setae long to very long.
Spermatheca not observable.
Biology and ecology. Stenus amurensis is distributed in the plains and low mountainous
regions in Japan. The beetles inhabits moist litter heaped at the grasslands and natural forests
located near the lakes and marshes, and also wet litter in the vicinity of standing waters.
Remarks. Naomi & Puthz (1994a) tentatively recorded S. amurensis from Japan (Hokkaido),
based on two female specimens, because they did not examine the males. Naomi & Puthz (1996)
conﬁrmed that those Stenus specimens belong to S. amurensis when they additionally examined
its male specimens from Hokkaido.
Stenus amurensis is allied to S. nishikawai, but it is separable from the latter by the legs
darker in coloration (dark red to black), the hind femur of male with a small tooth at the posteriorside of the base, the 7th ventrite of male with posteromedian concavity shallower and more shallowly emarginate (Fig. 30E), the 8th ventrite of male with posteromedian emargination broader(Fig. 30E), and the endophallic basal tube body swollen laterally at apex (Fig. 30F).
Stenus distans Sharp(Figs. 31A–G, 128I)
Stenus distans Sharp, 1889: 327; Herman, 2001: 2163; Naomi & Puthz, 2013: 137.
Stenus beppuensis Bernhauer, 1939b: 151; Puthz, 1974: 435.
Type material examined. Holotype of S. distans: ♀ (NHML), type locality: Nagasaki [examined by Puthz in 1965]. Holotype of S. beppuensis: ♀ (FMC), type locality: Beppu [examined by
Puthz in 1967].
Other material examined. [HOKKAIDO]: 1 ♂, Abashiri, 1. viii. 1954, T. Nakane leg.; 1 ♀,Memanbatsu-cho, 2. ix. 1992, T. Kato leg.; 1 ♀, Tomiiso, Teuri Is., 9. vii. 2001, T. Shimada leg.
[HONSHU]: 1 ♀, Sarukura, Mt. Chokai, Akita Pref., 19. vi. 1980, S. Naomi leg.; 1 ♀, Ochinome,
Sakata City, Yamagata Pref., 3. x. 1992, S. Nomura leg.; 1 ♀, Sanpoku-machi, Niigata Pref., 2.
vii. 1985, S. Nomura leg.; 2 ♂, Fukumizu, Hakui City, Ishikawa Pref., 20. x. 1995, T. Kishimoto
leg.; 1 ♀, Chikuma River, Ueda City, Nagano Pref., 19. ix. 1991, K. Sugiyama leg.; 1 ♂, Mt.
Tomi, Chiba Pref., 4. x. 1970, H. Yamazaki leg.; 7 ♂2 ♀, Karo Sand-dune, Tottori Pref., 26. xi.
1991, N. Tsurusaki leg.; 1 ♂, Mt. Takahara, Okayama Pref., 6. ix. 1981, K. Yoshihara leg. [SHI-90

Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

Fig. 31. Stenus distans Sharp (A, Okino-erabu, Kagoshima; B, D, G, Takahara, Okayama; C, E, Karo, Tottori; F,
H, Asami, Amami Is.). A, aedeagus; B, 9th ventrite of male; C, 7th to 8th ventrites of male; D, endophallic
expulsion hook; E, apex of gonocoxite; F, 9th and 10th terga of male; G, endophallic structures; H, apex of
the posterolateral projection of 9th tergum (lateral view). Scale 1: 0.2 mm for A, B, 0.1 mm for D, E, G; scale
2: 0.3 mm for C; scale 3: 0.2 mm for F, H.

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91

KOKU]: 1 ♂, Mt. Ishizuchi, Ehime Pref., 1. viii. 1977, S. Naomi leg. [KYUSHU]: 1 ♀,Akagawa, Mt. Kujyu, Ohita Pref., 13. viii. 1983, H. Harada leg.; 1 ♀, Hazama, Ohita Pref., 5. xi.
1985, A. Miyata leg. [NANSEI ISLS.]: 1 ♀, Kuchi Is., Tokara, Kagoshima Pref., 1. vii. 1969, H.
Makihara leg.; 1 ♂, Asani, Amami Is., Kagoshima Pref., 5. v. 1966, T. Shibata leg.; 1 ♀, Akirigami River, Toku Is., Kagoshima Pref., 3. v. 1988, S. Nomura leg.; 1 ♂1 ♀, Okino-erabu Is.,
Kagoshima Pref., 24. iii. 1966, T. Ito leg.; 2 ♀, same locality, 25. iii. 1966, T. Ito leg.; 1 ♀, same
locality, 25. iii. 1966, H. Nomura leg. [CHINA]: 1 ♀ (cS), China, border Shaanxi-Sichuan Daba
Shan pass 20 km SSE Zhenping, 1700–1800 m, 9. vii. 2001, A. Smetana leg.
Distribution. Japan (Hokkaido, Honshu, Shikoku, Kyushu; Teuri Is., Kuchi Is., Amami Is.,
Toku Is., Okino-erabu Is.); Korea, China.
Redescription. Male and female: Macropterous; body 3.9–5.1 mm (fore-body 2.0–2.3 mm) in
length, dull to weakly shining, with antennae moderately long and thin. Body black, with metallic reﬂection; labrum black; antennae with 1st to 2nd segments black, 3rd to 11th segments reddish brown; legs yellowish brown to reddish brown, with knees more or less infuscate. Headwith a pair of broad, longitudinal depressions; punctures round, very dense, distinct. Pronotumwith surface weakly uneven, with an indistinct median longitudinal depression; punctures round,very dense, somewhat rough. Elytra with surface almost smooth to weakly uneven; puncturesround to elliptical, very dense, distinct. Legs relatively long; tarsi with 4th tarsomere simple.
Abdomen subcylindrical, well convex above; 3rd to 6th terga each with 3 basal longitudinalkeels; punctures round, dense, small and distinct in anterior segments, while in posterior segments punctures sparse to moderately dense, very small, regular and distinct; interstices between
punctures smooth and shining. Lateroventrites dorsomesial or horizontal in position, narrow,
punctate.
Male: Legs with femora thick; mid tibia with a small tooth at the apicomesial corner; 4th and5th ventrites each posteromedially with a very shallow emargination; 6th ventrite posteromedially with a large ﬂat area, which is very shallowly emarginate; 7th ventrite (Fig. 31C) mediallywith an large, elongate depression, which becomes deeper posteriorly, is arcuately emarginate
posteriorly, and distinctly ridged laterally in its posterior 1/2; 8th ventrite (Fig. 31C) posteromedially with a V-shaped emargination, and medially with a large, elongate shallow depression
which becomes broader anteriorly; 9th tergum (Fig. 31F) with apicolateral ﬂaps subtriangular,
ventral apophyses rather thick, posterolateral projections long, acute, curved dorsally when seen
laterally (Fig. 31H); 9th ventrite (Fig. 31B) very ﬁnely serrate and also arcuately emarginate posteriorly, with stem almost elongate-hexagonal in shape, apicolateral teeth acute, apicolateral setae
short; 10th tergum (Fig. 31F) small, entire. Aedeagal median lobe (Fig. 31A) bulbous basely,
strongly narrowed behind the middle, weakly constricted just before the apex, which is truncate.
Endophallic median longitudinal bands (Fig. 31A) with ventral bands each very long, slender,
straight, dorsal bands each short, weakly curved laterally before the middle; expulsion hooks
fused to form a gate-like sclerite with long anterolateral apophyses (Fig. 31D); basal tube (Fig.
31A) simple, with tube body simply attenuate; inner sac (Fig. 31G) with its anterior sac covered
densely with thin setae. Parameres (Fig. 31A) each with apical area large, very long, broadened
almost dorsoventrally, furnished with 38 to 39 moderately long to long setae along its mesial
margin, and also most apically with 7 to 8 long setae.
Female: Eighth ventrite posteromedially with a very small notch; gonocoxites (Fig. 31E)
each irregularly serrate posteriorly, with apicolateral tooth large, acutely pointed, apicolateral
setae long. Spermatheca not observable.
Biology and ecology. Stenus distans is widely distributed in Japan from Hokkaido through92

Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

Honshu and Shikoku to Kyushu and Nansei Isls. The beetles inhabit litter in the natural forests ofplains and low and high mountainous regions.
Remarks. Stenus distans is closely allied to S. disterminus, but it is clearly separable from thelatter by the 8th ventrite of male with emargination smaller and narrower (Fig. 31C), the aedeagal median lobe narrower behind the middle, with its simply truncate apex (Fig. 31A), the endophallic expulsion hooks narrower (Fig. 31D), and the basal tube body simply attenuate apically(Fig. 31G).
Stenus disterminus Puthz(Figs. 32A–G, 128J)
Stenus disterminus Puthz, 1993b: 179; Herman, 2001: 2163; Naomi & Puthz, 2013: 137.
Type material examined. Holotype: ♂ (CBM), Mt. Kiyosumi, Amatsu-kominato, Chiba Pref.,9. vi. 1991, T. Takeda leg. Paratypes: 1 ♀ (cN), Mt. Kiyosumi, Amatsu-kominato-machi, Chiba
Pref., 14. vii. 1990, T. Takeda leg.; 2 ♀ (cN), Yomogi, Mt. Kiyosumi, Chiba Pref., 13. v. 1990, T.
Takeda leg.
Other material examined. [HONSHU]: 1 ♂, Mt. Daifuku, Ichihara City, Chiba Pref., 19. vi.
1983, H. Yamazaki leg.; 2 ♀, Mt. Takago, Kimitsu City, Chiba Pref., 7. ix. 1996, S. Naomi leg.;2 ♂, same locality, 22. ix. 1997, S. Naomi leg.; 1 ♀, same locality, 7. vi. 1998, S. Naomi leg.; 1 ♀,same locality, 25. x. 1998, S. Naomi leg.; 1 ♀, same locality, 13. v. 2000, S. Naomi leg.; 1 ♀,same locality, 15. v. 2000, S. Naomi leg.; 1 ♂, same locality, 22. v. 2000, S. Naomi leg.; 1 ♂2 ♀,Umagaeshi, Gotenba City, Shizuoka Pref., 10. x. 1991, S. Nomura leg.; 1 ♂, Yamabushi Pass,
Doshi-mura, Yamanashi Pref., 18. x. 2000, S. Nomura leg.
Distribution. Japan (Honshu).
Redescription. Male and female: Brachypterous; body 4.5–5.2 mm (fore-body 2.1–2.3 mm)
in length, moderately shining, with antennae short. Body black, with metallic reﬂection; labrum
black; antennae reddish brown except for 1st black segment; legs yellowish brown to reddish
brown, with knees infuscate. Head with a pair of wide, longitudinal depressions; punctures roundto elliptical, dense to very dense, various in size. Pronotum with surface weakly uneven, with an
indistinct median longitudinal depression; punctures round, very dense, somewhat rough, distinct. Elytra with surface very weakly uneven; punctures round to elliptical, very dense, medium
to large in size. Legs relatively long; tarsi thin, with 4th tarsomere simple. Abdomen subcylindrical, well convex above; 3rd to 6th terga each with 3 basal longitudinal keels; punctures round,
dense, small and distinct in anterior segments, while punctures in posterior segments moderately
dense, very small and regular; interstices between punctures smooth, shining. Lateroventrites
dorsomesial or horizontal in position, narrow, punctate.
Male: Sixth ventrite posteromedially with a large, semicircular ﬂat area; 7th ventrite (Fig.
32A) posteromedially with a large, subtrapezoidal depression, which is arcuately emarginate posteriorly, and weakly ridged laterally; 8th ventrite (Fig. 32A) posteromedially with a wide
V-shaped emargination, and anteromedially with a large, elongate ﬂat area which becomes
broader anteriorly; 9th tergum (Fig. 32B) with apicolateral ﬂaps subtriangular, ventral apophyses
moderately long, very thick, posterolateral projections long, very acute; 9th ventrite (Fig. 32D)
elongate, irregularly serrate posteriorly, with stem elongate, apicolateral teeth acutely pointed,
apicolateral setae short; 10th tergum (Fig. 32B) short, very weakly emarginate posteromedially.
Aedeagal median lobe (Fig. 32E) elongate, narrowed apically behind the middle, truncate at

The Steninae of Japan Part 1

Fig. 32. Stenus disterminus Puthz (A–F, Takago, Chiba; G, Gotenba, Shizuoka). A, 7th to 8th ventrites of male;B, 9th and 10th terga of male; C, endophallic basal tube; D, 9th ventrite of male; E, aedeagus; F, expulsion
hook; G, apex of gonocoxite. Scale 1: 0.3 mm for A; scale 2: 0.2 mm for B, E; scale 3: 0.1 mm for C, F, G, 0.2
mm for D.

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apex, with ventral side of apex widely excavate posteriorly, ﬂanked laterally with sclerotizedwalls which are each acutely pointed apicomesially and furnished apically with 2 or 3 shortsetae. Endophallic median longitudinal bands (Fig. 32E) with ventral bands moderately long,straight, ventral bands short, diverging anteriorly; expulsion hooks large, fused to form a gatelike sclerite (Fig. 32F); basal tube (Fig. 32E) gourd in shape, with a pair of unique apical ﬂaps
which together form a nearly funnel-shaped structure (Fig. 32C). Parameres (Fig. 32E) each withapical area long, wide, furnished with 27 to 31 moderately long setae along its mesial margin,
and also most apically with 6 to 7 long setae.
Female: Eighth ventrite rounded posteriorly; gonocoxites (Fig. 32G) each irregularly serrate
posteriorly, with apicolateral tooth long, acutely pointed, apicolateral setae short. Spermatheca
not observable.
Biology and ecology. Stenus disterminus is distributed in the mountainous regions in central
Honshu. The beetles inhabit leaf litter in the natural forests. It was repeatedly observed in thenatural forests at the foots of Mt. Takago, Chiba that the beetles slowly walk around on the moiststones (on which mosses sometimes grow) existing along the mountain trails.
Remarks. Stenus disterminus is closely allied to S. distans, but it is separable from the latterby the 8th ventrite of male with V-shaped emargination larger and broader (Fig. 32A), the aedeagal median lobe broader behind the middle, with the ventral side of apex broadly excavate posteromedially (Fig. 32E), the endophallic expulsion hooks broader (Fig. 32F), and the basal tube
body gourd-shaped, apically with a pair of unique ﬂaps (Fig. 32C).
Stenus calliceps Bernhauer(Figs. 33A–G, 128K)
Stenus calliceps Bernhauer, 1916: 28; Herman, 2001: 2104; Naomi & Puthz, 2013: 137.
Type material examined. Holotype: ♀ (FMC), type locality: Kiautschou [examined by Puthz
in 1970].
Other material examined. [HONSHU]: 1 ♀, Hiogo; 1 ♂1 ♀ (FMC), 1 ♂ (cP), Okayama,
Japan. Sauter. [KYUSHU]: 1 ♀, Sata, 21. v. 1959, K. Sawada leg. [NANSEI-ISLS]: 1 ♀, TokaraTakara Is., Kagoshima Pref., 25. iii. 1992, S. Nomura leg. (See Puthz [1974: 436] regarding thecollecting data of S. calliceps from Hiogo and Kagoshima.) [CHINA]: 1 ♂ (cS), China, Gansu,
Dalijia Shan, 46 km W Linia, 2980 m, 10. vii. 1994, A. Smetana leg.
Distribution. Japan (Honshu, Kyushu; Nansei Is.); Korea, China.
Redescription. Male and female: Macropterous; body 5.0–5.2 mm (fore-body 2.3–2.4 mm) in
length, robust, dull to weakly shining. Body black, with metallic reﬂection; labrum black; antennae with 1st and 2nd segments black, 3rd to 11th segments reddish brown; legs reddish brown,with knees infuscate. Head concave between eyes, with a pair of distinct longitudinal depressions; punctures round to elliptical, very dense, various in size, distinct. Pronotum with surface
weakly uneven, with an indistinct median longitudinal depression; punctures very dense, somewhat rough, distinct. Elytra with surface weakly uneven; punctures round to elliptical, very
dense, distinct. Legs relatively long; 4th tarsomere simple. Abdomen thick, subparallel-sided; 3rd
to 6th terga each with 3 basal longitudinal keels; punctures round, dense, small and distinct inanterior segments, while punctures in posterior segments dense, very small and regular; interstices between punctures covered with mesh-like microsculpture. Lateroventrites dorsomesial or
horizontal in position, relatively narrow, punctate.

The Steninae of Japan Part 1

Fig. 33. Stenus calliceps Bernhauer (A–C, E, F, Okayama; D, Tokara-Takara Is., Kagoshima). A, aedeagus; B,
9th ventrite of male; C, 6th to 7th ventrites of male; D, apices of gonocoxites; E, 9th and 10th terga of male;F, 8th ventrite of male. Scale 1: 0.2 mm for A, B, D; scale 2: 0.3 mm for C; scale 3: 0.2 mm for E, F.

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Male: Fourth and 5th ventrites each posteromedially with subtriangular glabrous ﬂat area;
6th ventrite (Fig. 33C) posteromedially with a semicircular ﬂat area, which is furnished laterallywith a line of yellowish, long setae; 7th ventrite (Fig. 33C) posteromedially with a subtrapezoidal
depression, which is moderately emarginate posteriorly, distinctly ridged laterally, and also furnished laterally with a line of yellowish, long; 8th ventrite (Fig. 33F) posteromedially with a relatively small emargination; 9th tergum (Fig. 33E) with ventral apophyses long, straight, posterolateral projections long, very acute; 9th ventrite (Fig. 33B) elongate, ﬁnely serrate posteriorly,
with stem elongate, apicolateral teeth thick, weakly incurved apically; 10th tergum (Fig. 33E)
small, entire. Aedeagal median lobe (Fig. 33A) weakly constricted near the middle but relatively
thick behind the middle, with the apex rounded, furnished laterally with 3 pairs of very shortsetae. Endophallic median longitudinal bands (Fig. 33A) relatively short, thick; expulsion hooks(Fig. 33A) connected by anteromesial corner, each hook with anterior area projecting laterally;basal tube (Fig. 33A) simple, with basal room ovoidal in shape, tube body baculiform, weakly
swollen basally. Parameres (Fig. 33A) slender, almost straight, each rounded apically; apical area
furnished mesially and also apically with 32 to 33 dense setae of various length.
Female: Eighth ventrite rounded posteriorly; gonocoxites (Fig. 33D) each hardly serrate posteriorly, with apicolateral tooth moderately thick, apicolateral setae short. Spermatheca notobservable.
Biology and ecology. S. calliceps is a very rare Stenus species in Japan; and only a few beetles are collected at present. No ecological data are obtained, but the collecting records suggestthat the beetles are litter inhabitants.
Remarks. Stenus calliceps was ﬁrst recorded from Japan (Okayama, Hiogo and Kagoshima[Cape Sata]) by Puthz (1974). This species is allied to S. distans and S. disterminus, but this species is clearly separable from the latter two species by the f body somewhat robuster in structure(Fig. 128K), the abdomen with interstices between punctures distinctly covered with mesh-likemicrosculpture, and the aedeagal median lobe rounded apically (Fig. 33A). Note that morphology of the apicolateral ﬂaps of 9th tergum of male is not described here because the ﬂaps are difﬁcult to observe in the specimen examined.
Stenus formosanus Benick(Fig. 34A–F, 128L)
Stenus formosanus Benick, 1914: 285; Herman, 2001: 2184; Naomi & Puthz, 2013: 137.
Type material examined. Holotype: ♂ (DEIM), type locality: Hoozan, Taiwan [examined by
Puthz in 1966].
Other material examined. [NANSEI ISLS.]: 1 ♂, Kawahara, Sonai, Yonaguni Is., Okinawa
Pref., 2. iii. 2007, I. Tanaka leg. [VIETNAM]: 1 ♂, Tam Dao, Tonkin.
Distribution. Japan (Nansei Isls.: Yonaguni Is.); Taiwan, China, Vietnam.
Redescription. Male: Macropterous; body 6.0–6.5 mm (fore-body 2.8–2.9 mm) in length,
moderately shining, with antennae moderately long, elytra large, abdomen slender, cylindrical.
Body black, with metallic reﬂection; labrum black; antennae reddish brown; legs yellowish
brown to reddish brown, with knees infuscate. Head deeply concave, distinctly impressed evenjust inside mesial margins of eyes, with a pair of distinct longitudinal depressions; puncturesround to elliptical, very dense, somewhat rough. Pronotum well convex above, with surface
weakly uneven, with an indistinct median longitudinal depression; punctures very dense, rough,The Steninae of Japan Part 1

Fig. 34. Stenus formosanus Benick (A, C, Tam Dao, Tonkin; B, D–F, Sonai, Yonaguni Is.). A, 9th and 10th tergaof male; B, aedeagus; C, 9th ventrite of male; D, 6th to 7th ventrites of male; E, apex of 8th ventrite of male;F, endophallic expulsion hook. Scale 1: 0.2 mm for A, B; scale 2: 0.2 mm for C, 0.1 mm for E, F; scale 3: 0.3
mm for D.

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2 or more punctures sometimes putting together and running transversely on the central to posteromedian part. Elytra with surface weakly uneven; punctures round to elliptical, very dense,
and arranged characteristically (i.e., running from the anteromesial corners to midlateral parts,and from the midlateral parts to posteromesial cornres). Legs relatively long; femora thick; tarsi
with 4th tarsomere simple. Abdomen thin, subparallel-sided; 3rd to 6th terga each with 3 basal
longitudinal keels; punctures round, dense, small and distinct in anterior segments, while punctures in posterior segments moderately dense, very small and regular. Lateroventrites horizontal
or dorsomesial in position, very narrow, impunctate or simply furrowed.
Fifth ventrite posteromedially with a small ﬂat area, which is very weakly emarginate posteriorly; 6th ventrite (Fig. 34D) posteromedially with a semicircular ﬂat area, which is arcuately
emarginate posteriorly; 7th ventrite (Fig. 34D) posteromedially with a subtrapezoidal concavity,
which is moderately emarginate and distinctly ridged laterally; 8th ventrite (Fig. 34E) posteromedially with a large, U-shaped emargination; 9th tergum (Fig. 34A) with anterolateral ﬂaps
rounded anteriorly, ventral apophyses short, posterolateral projections long, acutely pointed; 9th
ventrite (Fig. 34C) elongate, hardly serrate posteriorly, with stem elongate-triangular in shape,
apicolateral teeth incurved, acute, apicolateral setae moderately long; 10th tergum (Fig. 34A)
almost entire. Aedeagal median lobe (Fig. 34B) slender, distinctly bisinuate laterally, with the
apex rounded, furnished with 5 pairs of very short setae. Endophallic median longitudinal bands(Fig. 34B) with ventral bands long, rounded anteriorly, dorsal bands short; expulsion hooks (Fig.
34B) almost fused to form a subtriangular sclerite, with its median longitudinal part more or lesssubmembranous (Fig. 34F); basal tube (Fig. 34B) pitcher-shaped, basal room submembranouswith its baal constriction distinct, tube body thick, with the apical thin, sclerotized rod. Parameres (Fig. 34B) each slender, distinctly sinuous, rounded apically; apical area short, weakly swollen mesially, furnished mesially with 8 to 9 moderately long setae, and most apically with 3 longsetae.
Female: Unknown from Japan. In Japan, only one male beetle of this species was once collected from Yonaguni Is.
Biology and ecology. No ecological data are obtained.
Remarks. Among the Japanese members of S. clavicornis group, S. formosamus is in generalsimilar in structure to S. distans, S. disterminus and S. calliceps, but this species is clearly separable from the latter three species by the head distinctly impressed just inside the mesial margins ofeyes, the elytra much larger, with punctures characteristically arranged as described above, theabdomen more strongly cylindrical and distinctly narrower, the aedeagal median lobe distinctly
bisinuate laterally (Fig. 34B), and the endophallic basal tube body pitcher-shaped (Fig. 34B).
Stenus clavicornis (Scopoli)(Figs. 35A–G, 129A)
Stenus clavicornis (Scopoli, 1763): 100; Naomi, 1988d: 58; Herman, 2001: 2128; Naomi &Puthz, 2013: 137.
Type material. Type locality: Carniolia.
Other material examined. [HOKKAIDO]: 3 ♂1 ♀, Kami-shunbetsu, 20. vii. 1977, S. Naomi
leg.; 1 ♂1 ♀, Onʼnenai, Tsurui, Kushiro Marsh, 24. viii. 1990, M. Sakai leg.; 3 ♀, Kirakotanmisaki, Kushiro Marsh, 25. viii. 1990, M. Sakai leg.; 3 ♂1 ♀, Shiretoko Pass, Shari-cho, 3. viii.
1989, K. Haga leg.; 1 ♀, Onbetsu-cho, 3. viii. 1988, K. Haga leg.; 1 ♂, Harutori, Kushiro City, 9.

The Steninae of Japan Part 1

Fig. 35. Stenus clavicornis (Scopoli) (A, Hokkaido, Kami-shunbetsu; B–D, G, Hokkaido, Kushiro; E, F, Hokkaido, Shari). A, 6th to 8th ventrites of male; B, aedeagus; C, endophallic expulsion hook; D, basal tube; E,
9th and 10th terga of male; F, 9th ventrite of male; G, apex of gonocoxite. Scale 1: 0.3 mm for A; scale 2: 0.2
for B, E, F; scale 3: 0.1 mm for C, D, G.

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Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

vii. 1998, T. Matsumoto leg.
Distribution. Japan (Hokkaido); Korea, China, Russia, Mongolia, Georgia, Armenia, Azerbaijan, Turkey, Europe, Canada, USA.
Redescription. Male and female: Macropterous (hind wings each folded but only reaching
the posterior margin of 3rd tergum when they are unfolded); body 5.0–5.7 mm (fore-body 2.1–
2.5 mm) in length, dull to weakly shining, with antennae short. Body black, with metallic reﬂection; labrum black; antennae dark brown to black; legs yellowish brown to reddish brown, withknees infuscate. Head with a pair of distinct longitudinal depressions; punctures round to elliptical, very dense. Pronotum with surface weakly uneven; punctures round, very dense, various insize. Elytra with surface weakly uneven; punctures round to elliptical, very dense, and arranged
almost longitudinally on the areas along the suture, where 2 or more punctures sometimes put
together. Legs relatively long; tarsi with 4th tarsomere simple. Abdomen subparallel-sided; 3rd to
6th (or 7th) terga each with 3 basal longitudinal keels; punctures round, dense, small and distinct
in anterior segments, while punctures in posterior segments various is shape, sparse to moderately dense, and very small; interstices between punctures covered with mesh-like microsculptures. Lateroventrites horizontal or ventromesial in position, relatively wide, punctate.
Male: Legs with femora thick; middle tibia with a small tooth at the apicomesial part; 6th
ventrite (Fig. 35A) posteromedially with a semicircular ﬂat area, which is very weakly emarginate posteriorly; 7th ventrite (Fig. 35A) posteromedially with a large, bell-shaped depression,
which is arcuately emarginate posteriorly; 8th ventrite (Fig. 35A) posteromedially with aV-shaped emargination; 9th tergum (Fig. 35E) with apicolateral ﬂaps rounded anteriorly, ventral
apophyses moderately long and wide; 9th ventrite (Fig. 35F) elongate, hardly serrate posteriorly,
with stem elongate, apicolateral teeth short, acute, apicolateral setae short; 10th tergum (Fig.
35E) almost entire, or very weakly emarginate posteriorly. Aedeagal median lobe (Fig. 35B)
slender, narrowed apically, deeply narrowly emarginate (or bilobed) apically, with each apicallobe strongly sclerotized laterally. Endophallic median longitudinal bands (Fig. 35B) with ventral
bands very long, running almost parallel, dorsal bands each very short, truncate anteriorly; expulsion hooks (Fig. 35B) fuse to form a gate-like sclerite with a small, posteromedian tooth, anterolateral arms long, well sclerotized (Fig. 35C); basal tube (Fig. 35B) with basal room subspherical, tube body consisting of two short rods which are weakly curved apically (Fig. 35D).
Parameres (Fig. 35B) slender, almost straight; apical area long, distinctly widened dorsoventrally, furnished mesially with 40 to 45 sense setae, and also most apically with 7 to 8 long setae.
Female: Eighth ventrite posteromedially with a very small notch; gonocoxites (Fig. 35G)
each irregularly serrate posteriorly, with apicolateral tooth long, acute, apicolateral setae very
long. Spermatheca not observable.
Biology and ecology. Stenus clavicornis is distributed in the plains and low mountainous
regions. In Hokkaido, the beetles inhabit relatively dry grasses in the grasslands; and they also
live in moist litter at the grasslands and natural forests located near the lakes and rivers.
Remarks. Stenus clavicornis is widely distributed in the Holarctic region; and it was ﬁrst
recorded from Japan (Hokkaido) by Naomi (1988d). S. clavicornis is allied to S. obsculipalpis
Hubenthal, 1911, but it is separable from the latter by the maxillary palpi and legs righter in coloration (i.e., yellowish brown to reddish brown) and the aedeagal median lobe with apical lobe
strongly sclerotized laterally (Puthz, 1972c). S. clavicornis is also allied to S. caspius Puthz,
1972c, but it is separable from the latter by the abdominal terga medially with denser punctures
and the aedeagal median lobe with apical part more deeply emarginate (Fig. 35B) (Puthz, 1972c).

The Steninae of Japan Part 1

101

Stenus takedai Naomi(Figs. 36A–G, 129B)
Stenus takedai Naomi, 1990d: 103; Herman, 2001: 2412; Naomi & Puthz, 2013: 138.
Type material examined. Holotype: ♂ (CBM), Midori-ku, Yokohama City, Kanagawa Pref.,15. vi. 1985, M. Tao leg. Paratypes: 1 ♂1 ♀ (cN), Suidobashi, Shonan-machi, Chiba Pref., 19. xi.
1984, T. Takeda leg.; 2 ♀ (cN), Midori-ku, Yokohama City, Kanagawa Pref., 5. v. 1986, M. Taoleg.; 1 ♀ (cN), Tsurumi-ku, Yokohama City, Kanagawa Pref., 16. v. 1987, M. Tao leg.
Other material examined. [HONSHU]: 1 ♀, Akigase, Urawa City, Saitama Pref., 23. ix.
1981, H. Oda leg.; 1 ♂1 ♀, Matsuzaki, Inzai, Chiba Pref., 3. v. 1991, T. Takeda leg.; 2 ♂, Midoriku, Yokohama City, Kanagawa Pref., 3. xi. 1986, M. Tao leg.; 2 ♂1 ♀, Totsuka-ku, Yokohama
City, Kanagawa Pref., 31. v. 1986, M. Tao leg.; 1 ♀, Sengokubara, Hakone, Kanagawa Pref., 23.
xi. 1969, Y. Hirano leg.
Distribution. Japan (Honshu).
Redescription. Male and female: Macropterous; body 3.8–5.1 mm (fore-body 1.9–2.2 mm) in
length, slender, moderately shining, with antennae moderately long. Body black; labrum black;antennae dark brown except for 1st black segments; legs yellowish brown to reddish brown.
Head with a pair of shallow longitudinal depressions, median area between the longitudinal
depressions very narrow, weakly convex; punctures round to elliptical, dense to very dense. Pronotum with surface weakly uneven; punctures round to elliptical, very dense, various in size.
Elytra with surface weakly uneven; punctures round, very dense, regular, distinct. Legs long,
slender; tarsi with 4th tarsomere simple. Abdomen slender, cylindrical; 3rd to 6th terga each with
3 basal longitudinal keels; punctures round, moderately dense to dense, small and distinct inanterior segments, while punctures in posterior segments sparse, very small and regular. Lateroventrites missing but tergoventral sutures existing in 4th to 6th segments.
Male: Seventh ventrite (Fig. 36D) posteromedially with a shallow, subtrapezoidal depression,
which is arcuately emarginate; 8th ventrite (Fig. 36D) posteromedially with a V-shaped emargination; 9th tergum (Fig. 36A) with anterolateral ﬂaps rounded anteriorly, ventral apophyses moderately long and wide, posterolateral projections long; 9th ventrite (Fig. 36C) elongate, hardly
serrate posteriorly, with stem elongate, apicolateral teeth long, acute, apicolateral setae short;
10th tergum (Fig. 36A) entire. Aedeagal median lobe (Fig. 36B) slender, becoming narrower apically, weakly constricted near apical 1/3, with apical part very weakly swollen laterally, roundedapicolaterally with 3 or 4 pairs of short setae. Endophallic median longitudinal bands (Fig. 36B)
with ventral bands moderately long, almost rounded apically, dorsal bands short; expulsion
hooks (Fig. 36B) fused to form a gate-like sclerite with anterolateral arms long (Fig. 36G); basal
tube (Fig. 36B, F) short, gourd-shaped, submembranous. Parameres (Fig. 36B) long, slender,
weakly curved; apical area spoon-like, furnished mesially with 10 to 11 sparse setae.
Female: Eighth ventrite entire; gonocoxites (Fig. 36E) each irregularly serrate posteriorly,
with apicolateral tooth large, very acute, apicolateral setae moderately long. Spermatheca notobservable.
Biology and ecology. Stenus takedai is distributed in the plains in central Honshu. The beetles inhabit litter in the grasslands or leaf litter in the vicinity of natural forests.
Remarks. Stenus takedai and S. laborator are characteristic in the following two characters:
The lateroventrites are missing in the 4th to 7th abdominal segments; and the basal area of aedeagal median lobe is rather short before the basal foramen, and thus the parameres attach near the102

Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

Fig. 36. Stenus takedai Naomi (A–E, G, Totsuka, Kanagawa; F, Shonan, Chiba). A, 9th and 10th terga of male;B, aedeagus; C, 9th ventrite of male; D, 7th to 8th ventrites of male; E, apex of gonocoxite; F, endophallic
basal tube; G, expulsion hook. Scale 1: 0.2 mm for A–C, 0.1 mm for E–G; scale 2: 0.3 mm for D.

The Steninae of Japan Part 1

103basal margin of median lobe (Figs. 36B, 37B). S. takedai is considered the sister species of S.
laborator, and it is easily separable from the latter by the body thinner, more strongly shining,with the elytra narrower and abdomen slenderer (Fig. 129B), the abdominal terga with punctures
sparser and smaller, the 7th ventrite of male with posteromedian depression smaller and shallower (Fig. 36D), and the aedeagal median lobe almost rod-like behind the middle (Fig. 36B).
Etymology. This species was named in honour of Mr. Takaaki Takeda, Funabashi who collected most of the type specimens of this species.
Stenus laborator Sharp(Figs. 37A–G, 129C)
Stenus laborator Sharp, 1889: 327; Herman, 2001: 2250; Naomi & Puthz, 2013: 138.
Type material examined. Lectotype: ♂ (NHML), type locality: Yokohama, Japan. Paralectotypes: 3 ♂ (NHML), type locality: Yokohama, Japan; 1 ♀ (NHML), type locality: Osaka, Japan,
6. VII.–8. VII. 81 [designated by Puthz (1968)].
Other material examined. [HOKKAIDO]: 1 ♂, Ishikari, 6. viii. 1962, Y. Shibata leg. [HONSHU]: 1 ♂, Takadate, Hiraizumi, Iwate Pref., 2. x. 1992, S. Nomura leg.; 1 ♀, Naya, Iwanuma
City, Miyagi Pref., 30. xi. 1995, S. Nomura leg.; 1 ♀ (cP), Watarase, Ibaragi, 11. x. 1961, K.
Mizusawa leg.; 1 ♂, Tone River, Toride City, Ibaraki Pref., 6. viii. 1986, M. Tao leg.; 2 ♂3 ♀,Jinbe-ohashi, Inba-mura, Chiba Pref., 28. iii. 1990, T. Takeda leg.; 2 ♂4 ♀, Negina River, Shimousa-machi, Chiba Pref., 3. xi. 1989, T. Takeda leg.; 2 ♂4 ♀, same locality, 21. iii. 1990, T.
Takeda leg.; 1 ♂1 ♀, Tone River, Nakaya, Sakae-cho, Chiba Pref., 6. v. 1991, S. Nomura leg.;1 ♂2 ♀, Suga-shinden, Sakae-cho, Chiba Pref., 30. x. 1989, T. Takeda leg.; 2 ♂, Yahata, Kyoto,
13. iii. 1941, K. Taniguchi leg.
Distribution. Japan (Hokkaido, Honshu).
Redescription. Male and female: Macropterous; body 3.6–5.0 mm (fore-body 2.0–2.3 mm) in
length, slender, weakly shining, with antennae moderately long. Body black; labrum black;antennae reddish brown to dark red except for 1st black segments; legs yellowish brown to reddish brown. Head with a pair of shallow longitudinal depressions, median area between the longitudinal depressions very narrow, weakly convex; punctures round to elliptical, dense to very
dense, various in size. Pronotum with surface weakly uneven; punctures round, very dense,
somewhat rough. Elytra moderately large, with surface uneven; punctures round, very dense,
somewhat rough. Legs long, slender; tarsi with 4th tarsomere simple. Abdomen slender, cylindrical; 3rd to 6th terga each with 3 basal longitudinal keels; punctures round, dense, small and distinct in anterior segments, while punctures in posterior segments sparse to moderately dense,
very small and regular. Lateroventrites and tergoventral sutures missing in 4th to 6th segments.
Male: Legs with mid tibia with a very small tooth at the apicomesial part, hind tibia mesiallywith a small tooth at the subapical part (Fig. 129C); 6th ventrite (Fig. 37D) posteromedially witha semicircular ﬂat area; 7th ventrite (Fig. 37D) medially with a large, elongate depression whichis arcuately emarginate posteriorly, and laterally ridged in posterior 1/2; 8th ventrite (Fig. 37D)
posteromedially with a deep, U-shaped emargination, and anteriorly with a depression with its
sides ridged, the anterior depression smoothly continuing to the central, relatively broad ﬂat area;
9th tergum (Fig. 37C) with anterolateral ﬂaps subtriangular, ventral apophyses moderately long;
9th ventrite (Fig. 37E) elongate, hardly serrate posteriorly, with stem very thin, narrow, basilateral emarginations small, apicolateral teeth very acute, apicolateral setae short; 10th tergum (Fig.
37E) entire. Aedeagal median lobe (Fig. 37B) narrow basally, distinctly spatulate, apicolaterally

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Fig. 37. Stenus laborator Sharp (Shimousa, Chiba). A, apex of gonocoxite; B, aedeagus; C, 9th and 10th terga of
male; D, 6th to 8th ventrites of male; E, 9th ventrite of male; F, endophallic expulsion hook; G, basal tube.
Scale 1: 0.1 mm for A, F, G, 0.2 mm for B, C, E; scale 2: 0.3 mm for D.

The Steninae of Japan Part 1

105with 4 pairs of short setae. Endophallic median longitudinal bands (Fig. 37B) short; expulsion
hooks (Fig. 37B, F) fused to form a H-shaped sclerite; basal tube (Fig. 37B, G) small, nearly
gourd-shaped, submembranous. Parameres (Fig. 37B) long, slender; apical area very long,
weakly incurved, furnished mesially with 18 to 19 (mostly) short, sparse setae.
Female: Eighth ventrite entire; gonocoxites (Fig. 37A) each hardly serrate posteriorly, withapicomesial tooth pointed, apicolateral tooth long, acute, apicolateral setae long. Spermatheca
not observable.
Biology and ecology. Stenus laborator is distributed in the plains and low mountainous
regions. The beetles inhabit leaf litter in the grasslands or near the rivers and ponds.
Remarks. Stenus laborator is closely allied to S. takedai, but it is easily separable from thelatter by the body thicker, less strongly shining, with the elytra broader and abdomen thicker(Fig. 129C), the abdominal terga with punctures denser and larger, the 7th ventrite of male withposteromedian depression larger and deeper (Fig. 37D), and the aedeagal median lobe distinctly
spatulate (Fig. 37B).
Species group of S. humilis Erichson
S. humilis group consists of 27 species in Japan; see Puthz (1970c) regarding a characterization of this group. Diagnostic characters are as follows: Legs with 4th tarsomere very weakly or
not bilobed; 3rd to 5th or 6th terga each with 3 short, basi-longitudinal keels; lateroventrites
almost horizontal or dorsomesial in position, narrow; 9th ventrite of male with apicolateral teeth(Figs. 38B) (or apicolateral parts strongly serrate; Puthz, 1970c, ﬁg.2) and paired macrosetae;
aedeagal medium lobe with paired apicolateral teeth and apicomedian subtransparent area (Fig.
5B, C); endophallic expulsion hooks fused to usually form a U-shaped (Fig. 38F) or transverse(Fig. 43B) sclerite; gonocoxite with apicolateral tooth short, bi- or trifurcate (Figs. 38G); spermatheca not observable.
Japanese members of S. humilis group will be subdivided into 2 subgroups; and the followings are short descriptions about the 2 subgroups.
Subgroup 1. This subgroup is composed of 3 species (S. japonicus, S. mammops and S.
hammondi) in Japan. Distributional range of the subgroup is Japan, China, Russia and northAmerica. This subgroup is clearly diagnosed by the following aedeagal character: The apical partof median lobe is divided longitudinally into the paired, pallet-like, sclerotized lobes (Figs. 38C).
Subgroup 2. This subgroup is composed of 24 species (S. expugnator, S. sakura, S. giushin,
S. zaishin, S. kirin, S. ohbayashii, S. lanceolatus, S. ochiba, S. satushin, S. nipponomontanus, S.
wasamatanus, S. corrugatus, S. hagai, S. curvaticellus, S. intumescens, S. displicatus, S. toukin,
S. ubusuna, S. kokie, S. serratimarginatus, S. zimmermanni, S. yasutoshii, S. houomontis and S.
takashii). They are all indigenous in Japan except for S. expugnator. Distributional range of thesubgroup is Japan and Russia. This subgroup is diagnosed by the following aedeagal characters:
The median lobe is broader or slender, but more or less violin-shaped in many species (Fig.
61A); the apical sclerotized area are narrowed apically (Figs. 43B); and the apicolateral teeth(Fig. 5B, C) are more or less developed (Figs. 43B, 49B); and the apex of median lobe is pointed(Figs. 43B), rounded (Fig. 60A), or with the apicomedian projection (Fig. 41A).
Key to the Japanese species of S. humilis group1(6) Median lobe with apical part bilobed (i.e., divided longitudinally into paired pallet-like,106

Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

sclerotized lobes; Fig. 38C). [Subgroup 1]
2(3) Apex of median lobe simply rounded (Fig. 38C); apical pallet-like lobe of median lobe
rounded without small tooth at anteromesial corner (Fig. 38C) ...................S. japonicus Sharp
3(2) Apex of median lobe medially with a deep, narrow incision (Fig. 39A); apical pallet-likelobe of median lobe angulate with a small tooth at anteromesial corner (Fig. 39A).
4(5) Expulsion hook with posterolateral corner weakly projecting laterally (Fig. 39F); basal tube
narrower, with apex smaller. (Fig. 39C) ......................................................S. mammops Casey
5(4) Expulsion hook with posterolateral corner simply angulate (Fig. 40G); basal tube broader,with apex larger (Fig. 40A) .........................................................................S. hammondi Puthz
6(1) Median lobe with apical part simple, with apical sclerotized area more or less developed.
[Subgroup 2]
7(8) Median lobe with broad apicomedian projection, apicolateral teeth missing (Fig. 41A); basal
tube with apical part beak-shaped (Fig. 41C) .........................................S. expugnator Ryvkin8(7) Median lobe without broad apicomedian projection, with apicolateral teeth; basal tube withapical part simple (i.e., simply rounded).
9(10) Basal tube distinctly divided into basal room and tube body, with paired lateral processes(Fig. 42E) ................................................................................................S. sakura Hromádka
10(9) Basal tube simply baculiform, usually not divided into basal room and tube body.
11(12) Median lobe with apicolateral teeth and also paired teeth located at the middle of lateralsides of apicomedian subtransparent area (Figs. 64A) .............................. S. takashii Naomi
12(11) Median lobe with apicolateral teeth; apicomedian subtransparent area laterally without
any teeth nor humps (Fig. 61A).
13(22) Apicolateral teeth (or humps) located at or near lateral margins of median lobe.
14(15) Apicolateral teeth (or humps) located near lateral margins of median lobe (Fig. 53D);
paramere furnished mesially with setae in stem as well as apical area (Fig. 53D).......................................................................................................................S. hagai Naomi
15(14) Apicolateral teeth (or humps) located just at lateral margins of median lobe; paramere furnished mesially with setae only in apical area.
16(17) Median lobe narrowed apically behind the middle, without apicolateral corners (Fig. 51B)............................................................................................................S. wasamatanus Puthz
17(16) Median lobe broader, with apicolateral corners developed.
18(19) Median lobe violin-shaped, with apicolateral teeth larger (Fig. 55D) ...................................
................................................................. S. intumescens Naomi, Nomura & Puthz sp. nov.
19(18) Median lobe not violin-shaped, with apicolateral teeth smaller.
20(21) Median lobe abruptly narrowed near apicolateral humps to form the lanceolate apicalsclerotized area (Fig. 56E); expulsion hook weakly arched anteriorly (Fig. 56D)....................................................................S. displicatus Naomi, Nomura & Puthz sp. nov.
21(20) Median lobe uniformly narrowed behind the rounded apicolateral corners to form the triangular apical sclerotized area (Fig. 57C); expulsion hook weakly arched posteriorly (Fig.
57C) ............................................................................................... S. toukin Naomi & Puthz
22(13) Apicolateral teeth (or humps) located at the mesial edges of ventro-lateral rims of medianlobe.
23(30) Median lobe with apex not pointed apically (rounded or angulate apically).
24(27) Median lobe strongly narrowed apically behind apicolateral corners, with apex narrow
but still rounded.
25(26) Seventh ventrite of male posteromedially with depression smaller (Fig. 48A); median

The Steninae of Japan Part 1

107lobe not violin-shaped (Fig. 48F, G) .............................................S. ochiba Naomi & Puthz
26(25) Seventh ventrite of male posteromedially with depression larger (Fig. 59E); median lobe
violin-shaped (Fig. 59B) ............................................................................... S. kokie Naomi
27(24) Median lobe distinctly with broad apex.
28(29) Median lobe weakly narrowed apically behind apicolateral corners, with apex angulate(Fig. 60A); median hook simply pointed apicolaterally (Fig. 62C) .......................................
...................................................................................................S. serratimarginatus Naomi
29(28) Median lobe strongly constricted behind apicolateral corners, apical sclerorized area narrow basally, with apex uniformly rounded; median hook shortly incurved anterolaterally(Fig. 62C) .............................................................................................. S. yasutoshii Naomi
30(23) Median lobe with apex more or less distinctly pointed apically (Fig. 43B).
31(40) Median lobe not violin-shaped (distinctly not so).
32(39) Paramere furnished mesially with setae only in apical area.
33(38) Median lobe with apicolateral corners more or less angulate; expulsion hook transverse atmedian part (or not arched posteriorly).
34(35) Median lobe distinctly constricted behind anterolateral corners to form the lanceolate
apex (Fig. 43B); expulsion hook wider (Fig. 43B) ....................................S. giushin Naomi
35(34) Median lobe almost simply narrowed apically, with the triangular apex; expulsion hooknarrower.
36(37) Median lobe with apical sclerotized area anteriorly with the narrower, U-shaped emargination (Fig. 44E); apicolateral teeth larger, located close to each other (Fig. 44E).................................................................................................................... S. zaishin Naomi
37(36) Median lobe with apical sclerotized area anteriorly with the broader, arcuate emargination(Fig. 45B); apicolateral teeth smaller, distantly located to each other (Fig. 45B)...............................................................................................................S. kirin Naomi & Ito
38(33) Median lobe without apicolateral corner (or lateral margin of median lobe uniformly, very
gently curved in apical half; Fig. 52A); expulsion hook weakly but entirely arched posteriorly (Fig. 52F) ................................................................. S. corrugatus Naomi & Shimada
39(32) Paramere furnished mesially with setae in stem as well as apical area (Fig. 54F)........................................................................................................... S. curvaticellus Naomi
40(31) Median lobe more or less violin-shaped.
41(46) Median lobe lanceolate apically.
42(45) Median lobe nearly violin-shaped (or apicolateral corners distinctly narrower than basal
bulbous area), with apical sclerotized area longer.
43(44) Seventh ventrite of male with depression narrower (Fig. 46G); apical sclerotized area of
median lobe with anterior emargination V-shaped (Fig.46E); expulsion hook with anterolateral arm shorter, simply rounded apically (Fig. 46C) ...................... S. ohbayashii Naomi
44(43) Seventh ventrite of male with depression broader (Fig. 47D); apical sclerotized area of
median lobe without anterior emargination (Fig. 47B); expulsion hook with anterolateralarm longer, incurved apically (Fig. 47B) ............................................ S. lanceolatus Naomi
45(42) Median lobe distinctly violin-shaped (or apicolateral corners about as wide as basal bulbous area), with apical sclerotized area shorter (Fig. 63B) ....... S. houomontis Naomi & Ito
46(41) Median lobe not so (or elongate-triangular, triangular or subtriangular apically)
47(50) Median lobe with apical sclerotized area elongate-triangular in shape.
48(49) Median lobe with apical sclerotized area shorter (Fig. 49B); expulsion hook with anterolateral arm moderately long (Fig. 49G) .................................................... S. satushin Naomi

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49(48) Median lobe with apical sclerotized area longer (Fig. 50A); expulsion hook anterolaterally with a small tooth (Fig. 50F) .............................................. S. nipponomontanus Naomi
50(47) Median lobe with apical sclerotized area not so (or triangular or subtriangular in shape).
51(52) Median lobe less strongly pointed apically, with apical sclerotized area triangular in shape(Fig. 58B); expulsion hook distinctly bent posteriorly at the middle (Fig. 58F).........................................................................................................S. ubusuna Naomi & Ito
52(51) Median lobe more strongly (or acutely) pointed apically, with apical sclerotized area subtriangular in shape (Fig. 61A); expulsion hook simply, weakly, entirely arched posteriorly(Fig. 61F)............................................................................................S. zimmermanni Puthz
Stenus japonicus Sharp(Figs. 38A–G, 129D)
Stenus japonicus Sharp, 1874: 84; Herman, 2001: 2237; Naomi & Puthz, 2013: 138.
Stenus niponensis Cameron, 1930: 205; Naomi, 1989a: 41 (cited as S. nipponensis); Naomi &Puthz, 1994a: 217 (synonym of S. japonicus).
Stenus giushin Naomi, 1990: 101 (partim).
Type material examined. Syntypes of S. japonicus (NHML), type locality: Nagasaki [examined by Puthz in 1965]. Holotype of S. niponensis: ♀ (NHML), type localities: Yakushima;
Mimasaka [examined by Puthz in 1968].
Other material examined. [HOKKAIDO]: 3 ♂5 ♀, Onʼnenai, Tsurui, Kushiro Marsh, 24. viii.
1990, M. Sakai leg.; 2 ♀, Higashi-ohnuma, Nanae, Oshima, 14. vi. 1986, S. Nomura leg.; 1 ♀,same locality, 15. vi. 1986, S. Nomura leg.; 1 ♂3 ♀, same locality, 16. vi. 1986, S. Nomura leg.;1 ♀, Shoro Beach, Shiranuka-cho, 28. viii. 1990, M. Sakai leg.; 1 ♂, Tomakomai, 31. viii. 1978,
H. Detani leg.; 1 ♀, Toyokoro, 27. v. 1990, K. Haga leg. [HONSHU]: 1 ♂, Watarase Marsh,
Tochigi Pref., 6. v. 1979, M. Tao leg.; 1 ♀, Tencho, Shioya-cho, Tochigi Pref., 18. v. 1993, T.
Kishimoto leg.; 4 ♀, Oose, Yashio City, Saitama Pref., 12. iv. 1992, Hinakura leg.; 1 ♂, Hizaura,
Oohara-machi, Chiba Pref., 30. xii. 1989, T. Takeda leg.; 1 ♂, Kisarazu City, Chiba Pref., 25. v.
1985, M. Tao leg.; 1 ♀, Matsuzaki, Inzai, Chiba Pref., 10. xii. 1989, T. Takeda leg.; 1 ♂1 ♀,Kawasaki City, Kanagawa Pref., 10. iv. 1977, M. Tao leg.; 1 ♂, Yokohama City, Kanagawa Pref.,1. x. 1983, M. Tao leg.; 1 ♀, Otari, Nagano Pref., 5. vi. 1994, Y. Hirano leg.; 1 ♀, Tokoname City,
Aichi Pref., 3. vi. 1977, M. Ohishi leg.; 1 ♀, Mennoki Pass, Aichi Pref., 5. v. 1983, M. Sato leg.;1 ♀, Oochidani, Tottori City, Tottori Pref., 22. xi. 1991, N. Tsurusaki leg. [SHIKOKU]: 1 ♂, Toyo
City, Ehime Pref., 13. iv. 1985, M. Sakai leg.; 1 ♀, Akui River, Naka-akui, Tokushima Pref., 15.
viii. 1988, M. Sakai leg. [KYUSHU]: 1 ♂1 ♀, Imazu, Fukuoka City, Fukuoka Pref., 29. i. 1989,
S. Nomura leg. (paratypes of S. guishin); 1 ♀, Tsuri River, Genkai-machi, Fukuoka Pref., 26. i.
1992, S. Nomura leg.; 1 ♂2 ♀, Sanʼnou, Yamato-machi, Saga Pref., 24. iii. 1991, S. Nomura leg.;1 ♂, Imari City, Saga Pref., 6. x. 1977, H. Ohishi leg.; 1 ♀, Mt. Iwato, Kazusa, Nagasaki Pref., 7.
ix. 1977, S. Imasaka leg.; 1 ♂1 ♀, Kueyama, Shimabara, Nagasaki Pref., 4. x. 1977, S. Imasaka
leg.; 1 ♂, Kuchinotsu-machi, Nagasaki Pref., 23. xi. 1979, S. Imasaka leg.; 2 ♀, Kumamoto City,
Kumamoto Pref., 30. iii. 1977, S. Naomi leg.; 1 ♂, Hitoyoshi City, Kumamoto Pref., 16. x. 1977,
H. Ohishi leg.; 1 ♀, Miike Pond, Mt. Kirishima, Kagoshima Pref., 18. v. 1983, Y. Sawada leg.;1 ♀, Imuta Pond, Kedoin-cho, Kagoshima Pref., 9. xii. 1989, S. Nomura leg.; 2 ♂1 ♀, Fukiagehama, Kagoshima Pref., 11. xii. 1989, S. Nomura leg.
Distribution. Japan (Hokkaido, Honshu, Shikoku, Kyushu); China, Russia.

The Steninae of Japan Part 1

109

Fig. 38. Stenus japonicus Sharp (A–D, F, G, Hizaura, Chiba; E, Kawasaki, Kanagawa). A, 9th and 10th terga of
male; B, 9th ventrite of male; C, aedeagus; D, endophallic basal tube; E, 7th to 8th ventrites of male; F, expulsion hook; G, apex of gonocoxite. Scale 1: 0.2 mm for A–C, 0.1 mm for D, F, G; scale 2: 0.3 mm for E.

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Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

Redescription. Male and female: Macropterous/brachypterous; body 3.4–4.0 mm (fore body
1.8–2.1 mm) in length, dull to moderately shining, with antennae short. Body and its appendages
almost entirely dark red to black. Head with a pair of shallow longitudinal depressions; puncturesround, very dense, distinct. Pronotum with surface weakly uneven; punctures round, very dense,
distinct. Elytra with surface uneven; punctures round to elliptical, very dense, somewhat rough.
Legs short; tarsi with 4th tarsomere very weakly bilobed. Abdomen weakly narrowed posteriorly; 3rd to 5th terga each with 3 short, basi-longitudinal keels; punctures round to elliptical,
dense, small and distinct in anterior segments, while puncture in posterior segments elliptical,
dense, very small and regular. Lateroventrites horizontal in position, narrow, punctate.
Male: Seventh ventrite (Fig. 38E) posteromedially with a ﬂat area which is very shallowly
emarginate posteriorly; 8th ventrite (Fig. 38E) posteromedially with a wide, arcuate emargination; 9th tergum (Fig. 38A) with ventral apophyses moderately long, thin; 9th ventrite (Fig. 38B)
relatively wide, hardly serrate posteriorly, with stem wide, bilobed (or strongly bifurcate), apicolateral teeth each short, incurved, bi- or trifurcate apically, apicolateral setae short; 10th tergum(Fig. 38A) very weakly emarginate posteriorly. Aedeagal median lobe (Fig. 38C) almost simply
narrowed apically, rounded apically, with paired apical sclerotized lobes which are divided longitudinally, pallet-like, rounded anteromesially, and also furnished apicolaterally with 2 or 3 shortsetae. Endophallic median longitudinal bands (Fig. 38C) with ventral bands very long, dorsal
bands short, distinctly curved laterally before the middle; expulsion hook (Fig. 38C, F) simply
U-shaped; basal tube (Fig. 38C) very large, with basal room nearly triangular in shape, tube body
distinctly spatulate (Fig. 38D). Parameres (Fig. 38C) short, not reaching the apex of median lobe,
each pointed apically; apical area weakly swollen basally, furnished mesially with 12 to 14 setae.
Female: Eighth ventrite entire; gonocoxites (Fig. 38G) each irregularly serrate posteriorly,
with apicolateral tooth tri- or tetrafurcate apically, apicolateral setae moderately long. Spermatheca not observable.
Biology and ecology. Stenus japonicus is a common species in Japan; and it is widely distributed in the plains and low mountainous regions. The beetles inhabit litter in the natural forestsand glass lands.
Remarks. Stenus japonicus is allied to S. mammops and S. hammondi, but this species isclearly separable from the latter two species by the aedeagal median lobe rounded apically (Fig.
38C), the apical sclerotized lobe gently rounded anteromesially (Fig. 38C), the expulsion hook
simply U-shaped (Fig. 38F), and the endophallic basal tube body distinctly spatularte, with the
apex very large, ovoidal (Fig. 38D).
Stenus mammops Casey(Figs. 39A–G, 129E)
Stenus mammops Casey, 1884: 97; Naomi, 1988c: 49; Naomi & Puthz, 1994: 42; Herman, 2001:
2272; Naomi & Puthz, 2013: 138.
Type material examined. Lectotype: ♂ (USNM), type locality: Trenton Falls [designated by
Puthz (1974: 163)].
Other material examined. [HOKKAIDO]: 3 ♀, Shiretoko Pass, Shari-cho, 3. viii. 1989, K.
Haga leg.; 1 ♀, Mt. Yotei, Kucchan-machi, 4-20. vii. 2000, K. Sasaki leg.; 1 ♂1 ♀, same locality,
20. vii. - 4. viii. 2000, K. Sasaki leg.; 2 ♀, same locality, 7. vii. 1989, N. Yasuda leg.; 2 ♂, Himenuma, Rishiri Is., 26. vi. 1986, S. Nomura leg.; 1 ♀, same locality, 9. vii. 1977, S. Naomi leg.;

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111

Fig. 39. Stenus mammops Casey (A, B, D, F, Guchian, Hokkaido; C, E, G, Himenuma, Rishiri Is.). A, aedeagus;
B, 9th and 10th terga of male; C, endophallic basal tube; D, 9th ventrite of male; E, 7th to 8th ventrites ofmale; F, expulsion hook; G, apex of gonocoxite. Scale 1: 0.2 mm for A, B, D, 0.1 mm for C, F, G; scale 2: 0.3
mm for E.

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Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

1 ♂1 ♀, same locality, 9. viii. 1990, T. Kishimoto leg.; 2 ♀, Toyokoro, Ootsu, 13. vii. 1992;
1 ♂1 ♀, Upepe-Sanke, Mt. Daisetsu, 9. vii. 2002, N. Yasuda leg.; 1 ♀, Barasan-to, Bekkai-cho, 5.
vii. 1986, S. Nomura leg. [KYUSHU]: 3 ♂2 ♀, Mt. Mitake, Tsushima Is., Nagasaki Pref., 1. iv.
1999, T. Watanabe leg.
Distribution. Japan (Hokkaido; Rishiri Is., Tsushima Is.); China, Russia, Canada, USA, West
Indies.
Redescription. Male and female: Brachypterous; body 3.2–4.3 mm (fore body 1.7–2.1 mm) in
length, dull to moderately shining, with antennae short. Body and its appendages almost entirely
dark red to black. Head with a pair of shallow longitudinal depressions; punctures round, very
dense, almost regular, distinct. Pronotum with surface weakly uneven; punctures round, very
dense, distinct. Elytra with surface uneven; punctures round to elliptical, very dense, large, somewhat rough. Legs short; tarsi short, moderately thick, with 4th tarsomere very weakly bilobed.
Abdomen wide, weakly narrowed posteriorly; 3rd to 5th terga each with 3 short, basi-longitudinal keels; punctures round to elliptical, dense, small and distinct in anterior segments, while
punctures in posterior segments elliptical, moderately dense, very small and regular. Lateroventrites ventromesial or horizontal in position, narrow, punctate.
Male: Seventh ventrite (Fig. 39E) posteromedially with a small, shallow, depression, which
is very shallowly emarginate posteriorly; 8th ventrite (Fig. 39E) posteromedially with a shallow,
broad emargination; 9th tergum (Fig. 39B) with ventral apophyses moderately long, wide; 9th
ventrite (Fig. 39D) elongate, ﬁnely serrate posteriorly, with stem wide, bilobed, apicolateral teeth
each short, bi- or trifurcate apically, apicolateral setae short; 10th tergum (Fig. 39B) very weakly
emarginate posteriorly. Aedeagal median lobe (Fig. 39A) simply narrowed apically, with the
apex medially with a deep, narrow incision, apical sclerotized lobes divided longitudinally, pallet-like, angulate anteromesially with a small tooth, and also furnished apicolaterally with 2 or 3
short setae. Endophallic median longitudinal bands (Fig. 39A) with ventral bands very wide,
moderately long, dorsal bands short, narrowed apically, strongly curved laterally; expulsion hook
(Fig. 39A) nearly U-shaped, weakly projecting laterally at posterolateral corner (Fig. 39F); basal
tube (Fig. 39A) rod-like but twice weakly constricted, with apex small, ovoidal (Fig. 39C). Parameres (Fig. 39A) short, not reaching the apex of median lobe; apical area furnished mesially with
12 to 13 setae.
Female: Eighth ventrite rounded posteriorly; gonocoxites (Fig. 39G) each strongly, irregularly serrate posteriorly and also apicolaterally, with apicolateral setae moderately long. Spermatheca not observable.
Biology and ecology. Stenus mammops is distributed in the plains, low and high mountainous
regions in Japan; and the previous collecting records show that this species is not rare in Hokkaido. The beetles inhabit leaf litter in natural forests. The syrup and vinegar seem to induce thebeetles of this species; and thus the beetles are sometimes collected by baited traps (with syrup
and vinegar) set in the forests of Hokkaido.
Remarks. Stenus mammops is ﬁrst recorded from Japan (Hokkaido) by Naomi (1988c). This
species is allied to S. hammondi, but it is separable from the latter by the 6th ventrite of malewithout modiﬁcation, the 7th ventrite of male posteromedially with a smaller depression (Fig.
39E), the endophallic median longitudinal bands shorter (Fig. 39A), the expulsion hook weakly
projecting laterally at posterolateral corner (Fig. 39F), and the basal tube body thinner, with apical area smaller (Fig. 39C).

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Stenus hammondi Puthz(Figs. 40A–G, 129F)
Stenus hammondi Puthz, 1970b: 31; Naomi & Puthz, 1996: 160; Herman, 2001: 2211; Naomi &Puthz, 2013: 138.
Type material examined. Holotype: ♂ (NHML), type locality: China: Harbin [examined by
Puthz].
Other material examined. [HOKKAIDO]: 1 ♂1 ♀, Echigo Bog, Ebetsu City, 9. iv. 1993, K.
Miyashita leg.; 2 ♀, same locality, 16. iv. 1993, K. Miyashita leg.; 1 ♀, same locality, 29. iv.
1995, K. Miyashita leg.
Distribution. Japan (Hokkaido); China, Russia.
Redescription. Male and female: Macropterous/brachypterous; body 2.7–3.3 mm (fore body
1.6–1.8 mm) in length, dull to weakly shining, with antennae short. Body black; labrum black;antennae dark red; legs reddish brown, with knees infuscate. Head not cave, with a pair of shallow longitudinal depressions; punctures round to elliptical, very dense, almost regular, distinct.
Pronotum with surface weakly uneven; punctures round, very dense, distinct. Elytra somewhat
ﬂat above, with surface weakly uneven; punctures round, very dense, somewhat rough. Legs
short; tarsi short, moderately thick, with 4th tarsomere very weakly bilobed. Abdomen wide,
weakly narrowed posteriorly; 3rd to 5th terga each with 3 short, basi-longitudinal keels; punctures round to elliptical, dense, small and distinct in anterior segments, while punctures in posterior segments elliptical, dense, very small and regular. Lateroventrites ventromesial or horizontal
in position, narrow, punctate.
Male: Sixth ventrite (Fig. 40B) posteromedially with a semicircular ﬂat area; 7th ventrite(Fig. 40B) posteromedially with a semicircular depression, which is arcuately emarginate posteriorly; 8th ventrite (Fig. 40B) posteromedially with a moderately wide emargination; 9th tergum(Fig. 40D) with ventral apophyses moderately long; 9th ventrite (Fig. 40C) elongate, irregularly
serrate posteriorly, with stem wide, arcuately emarginate anteriorly, basilateral emarginations
deep, narrow, apicolateral teeth each short, trifurcate apically, apicolateral setae short; 10th tergum (Fig. 40D) weakly emarginate posteriorly. Aedeagal median lobe (Fig. 40E) simply narrowed apically behind the middle, with the apex medially with a deep, narrow incision, apicalsclerotized lobes divided longitudinally, pallet-like, angulate anteromesially with a small tooth,and also furnished apicolaterally with 2 or 3 short setae. Endophallic median longitudinal bands(Fig. 40E) with ventral bands long, each weakly incurved apically, dorsal bands short, each narrowed apically; expulsion hook (Fig. 40E) pointed apicomedially, simply angulate posterolaterally (Fig. 40G); basal tube (Fig. 40A) consisting of two sclerotized shafts, twice strongly constricted in the middle, with asymmetrically swollen apex (Fig. 40E). Parameres (Fig. 40E) short,
not reaching the apex of median lobe, each weakly curved laterally before the base of apical area,
which is furnished mesially with 14 to 15 setae of different length.
Female: Eighth ventrite rounded posteriorly; gonocoxites (Fig. 40F) each rather irregularly
serrate posteriorly, with apicolateral tooth short, tri- or tetrafurcate apically, apicolateral setae
moderately long. Spermatheca not observable.
Biology and ecology. Stenus hammondi was presently collected once only at the Echigo Bog,
Ebetsu in Hokkaido; and the beetles inhabit moist litter (e.g. of reeds) around the bog there. In
the April where the Stenus beetles were collected in Hokkaido, the ice was thinly covered on thelitter around the Echigo Bog. During this very cold season, the adult beetles of S. hammondi

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Fig. 40. Stenus hamonndi Puthz (Ebatsu, Hokkaido). A, endophallic basal tube; B, 6th to 8th ventrites of male;C, 9th ventrite of male; D, 9th and 10th terga of male; E, aedeagus; F, apex of gonocoxite; G, expulsion hook.
Scale 1: 0.1 mm for A, F, G, 0.2 mm for C–E; scale 2: 0.3 mm for B.

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lives on and in the litter that are covered by thin ice; and in the warm season (June) where the ice(that covered the litters) has already melted away, the adult beetles were not observed at the same
litter where they lived in April (per. com. by K. Miyashita). The beetles were collected also on
the pathways near river, and at the plant roots on dry waste ground; they are also collected bysweeping the overgrown gardens (Puthz, 1970b).
Remarks. Stenus hammondi is ﬁrst recorded from Japan (Hokkaido) by Naomi & Puthz(1996). S. hammondi is allied to S. mammops, but this species is clearly separable from the latterby the 6th ventrite of male posteromediallly with a ﬂat area (Fig. 40B), the 7th ventrite of maleposteromedially with a larger depression (Fig. 40B), the median longitudinal bands longer (Fig.
40E), the endophallic expulsion hook simply angulate apicomedially, (Fig. 40G), and the basal
tube body thicker, with the larger apical swollen area (Fig. 40A).
Etymology. This species is named in honour of an eminent staphylinist, Mr. Peter Hammond(Natural History Museum, London).
Stenus expugnator Ryvkin(Figs. 41A–G, 129G)
Stenus expugnator Ryvkin, 1987a: 123; Naomi, 1997f: 143; Herman, 2001: 2173; Naomi &Puthz, 2013: 138.
Type material. Holotype: ♂ (ZIRAS), type locality: Kunashir, Russia.
Material examined. [HOKKAIDO]: 1 ♂, Oikawanai, Taiki-cho, 1. viii. 1993, K. Shibata leg.;1 ♂1 ♀, Bansei Shore, Taiki-cho, 19. vi. 2009, T. Watanabe leg. [HONSHU]: 1 ♂6 ♀, ObitsuRiver, Kuroto, Kisarazu, Chiba Pref., 5. v. 1996, S. Nomura leg.; 1 ♂, Near Kuroto, Kisarazu,
Chiba Pref., 27. iv. 1986, R. Inagawa leg.
Distribution. Japan (Hokkaido, Honshu: Chiba Pref.); Russia.
Redescription. Male and female: Brachypterous; body 3.5–4.1 mm (fore body 1.7–2.0 mm) in
length, weakly shining, with antennae short. Body black; labrum black; antennae and legs dark
red. Head not concave, with a pair of shallow longitudinal depressions; punctures round to elliptical, very dense, distinct. Pronotum with surface weakly uneven; punctures round, very dense,
distinct. Elytra with surface almost even; punctures round, very dense, somewhat rough. Legs
short; tarsi short, moderately thick, with 4th tarsomere very weakly bilobed. Abdomen wide,
weakly narrowed posteriorly; 3rd to 5th terga each with 3 short, basi-longitudinal keels; punctures round to elliptical, dense, small and distinct in anterior segments, while punctures in posterior segments elliptical, dense, very small and regular. Lateroventrites ventromesial or horizontal
in position, narrow, punctate.
Male: Eight ventrite (Fig. 41E) posteromedially with a semicircular, very shallow depression,
which is shallowly emarginate posteriorly; 9th tergum (Fig. 41B) with ventral apophyses moderately long; 9th ventrite (Fig. 41D) elongate, ﬁnely serrate posteriorly, with stem subtrapezoidal,
constricted basally, apicolateral teeth each short, trifurcate apically, apicolateral setae short; 10th
tergum (Fig. 41B) truncate posteriorly. Aedeagal median lobe (Fig. 41A) elongate, weakly swollen laterally near basal oriﬁce, widely rounded apicolaterally, with the apicomedian projection
short, wide, weakly emarginate posteriorly. Endophallic median longitudinal bands (Fig. 41A)
very long, slender; expulsion hook (Fig. 41A, F) almost M-shaped, with its posterolateral part
angulate posteriorly; basal tube (Fig. 41A) with basal room ovoidal, submembranous, tube bodyalmost baculiform, with beak-shaped apex (Fig. 41C). Parameres (Fig. 41A) slender, almost

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Fig. 41. Stenus expugnatur Ryvkin (A–D, F, Taiki, Hokkaido; Em G, Obitsu, Chiba). A, aedeagus; B, 9th and10th terga of male; C, endophallic basal tube; D, 9th ventrite of male; E, 7th to 8th ventrites of male; F, expulsion hook; G, apex of gonocoxite. Scale 1: 0.2 mm for A, B, D, 0.1 mm for C, F, G; scale 2: 0.3 mm for E.

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straight, short, not reaching the apex of median lobe; apical area short, furnished mesially with 9
to 10 setae.
Female: Eighth ventrite rounded posteriorly; gonocoxites (Fig. 41G) each rather irregularly
serrate posteriorly, with apicolateral tooth trifurcate apically, apicolateral setae moderately longto long. Spermatheca not observable.
Biology and ecology. The beetles of Stenus expugnator inhabit the litter of reeds and othergrasses grown at the estuary of rivers, suggesting that this is a halophilous species.
Remarks. Stenus expugnator was ﬁrst recorded from Japan (Hokkaido, Chiba) by Naomi(1997f). This species is closely allied to S. proclinatus Benick, 1922 from China, but it is separable from the latter by the 8th ventrite of male with posteromedian emargination larger andbroader (Fig. 41E), the aedeagal median lobe with apicomedian projection only weakly emarginate apically (Fig. 41A), and the endophallic expulsion hook being M-shaped as in S. proclinatus
but narrower, thicker medially, and only less shallowly emarginate posteriorly (Fig. 41F). S.
expugnator is also allied to S. carbonarius Gyllenhal, 1827, which is widely distributed in thewestern part of Eurasian continent, but it is separable from the latter by the endophallic expulsion
hook being M-shaped (Fig. 41F) and the basal tube beak-shaped apically.
Stenus sakura Hromádka(Fig. 42A–F)
Stenus sakura Hromádka, 1979a: 115; Herman, 2001: 2376; Naomi & Puthz, 2013: 138.
Type material examined. Holotype: ♂ (MHNG), Mt. Ohdai, Nara Pref., 24. viii. 1968, K.
Sawada leg.
Distribution. Japan (Honshu: Nara Pref.).
Redescription. Male: Brachypterous; body 3.5 mm (fore body 1.6 mm) in length, moderately
shining, with antennae relatively short. Body black, slightly with reddish tinge on pronotum andelytra; labrum black; antennae dark red; legs dark reddish brown to black. Head with a pair of
longitudinal depressions; punctures round to elliptical, very dense, various in size, distinct. Pronotum with surface weakly uneven; punctures round, very dense, various in size. Elytra with surface uneven; punctures round, very dense, various in size. Legs short; tarsi short, with 4th tarsomere very weakly bilobed. Abdomen relatively wide; 3rd to 5th terga each with 3 short,basi-longitudinal keels; punctures round to elliptical, moderately dense to dense, and various insize in anterior segments, while punctures in posterior segments very elliptical, moderately
dense, small and regular. Lateroventrites dorsomesial or horizontal in position, narrow, punctate.
Sixth ventrite (Fig. 42D) posteromedially with a semicircular depression, which is shallowly
emarginate posteriorly, sparsely covered with setae, and also furnished with several relatively
long setae at posterolateral corners; 7th ventrite (Fig. 42D) posteromedially with a large, bellshaped depression, which is arcuately emarginate, ridged posterolaterally, and covered denselywith short setae; 8th ventrite (Fig. 42D) posteromedially with a V-shaped emargination, and centrally with a shallow depression, which become shallower posteriorly; 9th tergum (Fig. 42A)
with ventral apophyses long; 9th ventrite (Fig. 42C) elongate, ﬁnely serrate posteriorly, withstem elongate-rectangular in shape, apicolateral teeth each short, bifurcate apically; 10th tergum(Fig. 42A) transverse, shallowly emarginate posteriorly. Aedeagal median lobe (Fig. 42B) elongate, gently rounded apicolaterally, its apex acutely pointed, ventromedially with a longitudinal
keel; apicomedian subtransparent area large, almost pentagonal in shape; apicolateral teeth

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Fig. 42. Stenus sakura Hromádka (Ohdaigahara, Nara). A, 9th and 10th terga of male; B, aedeagus; C, 9th ventrite of male; D, 6th to 8th ventrites of male; E, endophallic basal tube; F, expulsion hook. Scale 1: 0.1 mm for
A–C; scale 2: 0.3 mm for D; scale 3: 0.1 mm for E, F.

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pointed, each located at the mesial margin of lateral rim. Endophallic median longitudinal bands(Fig. 42B) broad, moderately long; expulsion hook structured as in Fig. 42B, F; basal tube (Fig.
42B) with basal room large, elongate-ovoidal in shape, tube body simply baculiform, ventrallywith paired lateral processes which are thin and weakly incurved (Fig. 42E). Parameres (Fig.
42B) thin, slender, very weakly incurved; apical area moderately long, covered mesially with 17
to 18 moderately long setae.
Female: Not examined.
Biology and ecology. S sakura is a very rare Stenus species; and only a few beetles were collected in the natural forests of mountainous regions in Honshu (Kii-Peninsula). The beetles areleaf litter inhabitants.
Remarks. Stenus sakura was originally described by Hromádka in 1979a, based on 1 maleand 2 female (Ohdai, Nara) and 1 female (Chuzenji, Tochigi). We examined the paratype specimen from Chuzenji (cP) and found that it belongs to S. zimmermanni Puthz, 1968b. Being distinctly different from all other members of subgroup 2 in Japan, S. sakura is very characteristic
in having the endophallic basal tube ventrally with paired lateral processes (Fig. 42E). Given
this, it is difﬁcult to detect the closely related species of S. sakura among the Japanese membersof S. humilis group, but it is clearly distinguished from them by the endophallic structures mentioned above.
Etymology. The speciﬁc epithet of this species is derived from the Japanese name of cherry
tree “Sakura”.
Stenus giushin Naomi(Figs. 43A–F, 129H)
Stenus giushin Naomi, 1990d: 101; Herman, 2001: 2201; Naomi & Puthz, 2013: 138.
Type material examined. Holotype: ♂ (CBM), Ryumon Valley, Saga Pref., 23. x. 1977, H.
Ohishi leg. Paratypes: 9 ♂5 ♀ (cN), same data as holotype; 1 ♂ (cN), Kyogatake, Saga Pref., 6.
vi. 1983, S. Nomura leg.; 1 ♀ (cN), Mt. Seira, Imari City, Saga Pref., 3. iii. 1985, S. Nomura leg.;1 ♂2 ♀ (cN), Kikuchi Valley, Kumamoto Pref., 11. iv. 1981, S. Naomi leg.
Other material examined. [KYUSHU] 4 ♂1 ♀, Mt. Unzen, Shimabara, Nagasaki Pref., 16. v.
1986, T. Ito leg.
Distribution. Japan (Kyushu). In the original description by Naomi (1990), S. giushin isrecorded also from Fukuoka Pref. northern Kyushu, but it was clariﬁed that the specimens of S.
japonicus recorded from Fukuoka are mistook for those of S. giushin.
Redescription. Male and female: Brachypterous; body 2.6–3.3 (fore body 1.4–1.6 mm) in
length, moderately shining, with antennae relatively short. Body black, slightly with reddish
tinge on pronotum and elytra; labrum black; antennae dark red; legs reddish brown, with knees
more or less infuscate. Head with a pair of longitudinal depressions; punctures round, very
dense, almost regular. Pronotum with surface weakly uneven; punctures round, very dense. Elytra with surface weakly uneven; punctures round, very dense, somewhat rough. Legs relatively
short; tarsi short, with 4th tarsomere very weakly bilobed. Abdomen relatively wide to wide; 3rd
to 5th or 6th terga each with 3 short, basi-longitudinal keels; punctures round to elliptical, moderately dense, small and distinct in anterior segments, while punctures in posterior segments elliptical, sparse to moderately dense, very small and regular. Lateroventrites dorsomesial or horizontal
in position, narrow, punctate.

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Fig. 43. Stenus giushin Naomi (A, Kyogatake, Saga; B, F, Kikuchi, Kumamoto; C–E, Ryumon, Saga). A, 5th to
8th ventrites of male; B, aedeagus; C, apex of gonocoxite; D, 9th and 10th terga of male; E, 9th and 10th tergaof female; F, 9th ventrite of male. Scale 1: 0.3 mm for A; scale 2: 0.1 mm for B; scale 3: 0.1 mm for C; 0.2 mm
for D–F.

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121

Male: Fifth ventrite (Fig. 43A) posteromedially with a very shallow emargination; 6th ventrite (Fig. 43A) posteromedially with a subtrapezoidal ﬂat area, which is arcuately emarginate,
and furnished sparsely with setae along posterior margin, and also with several setae at posterolateral corners; 7th ventrite (Fig. 43A) posteromedially with a large, bell-shaped depression,
which is arcuately emarginate and furnished with short setae at posterolateral corners; 8th ventrite (Fig. 43A) posteromedially with a small emargination, and centrally with a shallow depression, which become shallower posteriorly; 9th tergum (Fig. 43D) with ventral apophyses moderately long; 9th ventrite (Fig. 43F) elongate, indistinctly serrate posteriorly, with stem rounded
anteriorly, apicolateral teeth each short, bi- or trifurcate apically, apicolateral setae short; 10th
tergum (Fig. 43D) entire. Aedeagal median lobe (Fig. 43B) elongate, gently rounded apicolaterally, moderately constricted behind the apicolateral corners to form the lanceolate apex; apicalsclerotized area anteromedially with very short, sparse setae; apicomedian subtransparent area
elongate-ovoidal in shape; apicolateral teeth very large, pointed, well sclerotized, broad-triangular in shape, each located at the mesial margin of lateral rim. Endophallic median longitudinalbands (Fig. 43B) moderately long; expulsion hook (Fig. 43B) transverse, with short posterolateral arms; basal tube (Fig. 43B) large, baculiform. Parameres (Fig. 43B) slender; apical area
weakly swollen mesially, furnished mesially with 18 to 20 moderately long setae.
Female: Eighth ventrite rounded posteriorly; 9th tergum (Fig. 43E) without ventral apophyses; gonocoxites (Fig. 43C) each irregularly serrate posteriorly, with apicolateral tooth bi- or trifurcate apically, apicolateral setae moderately long; 10th tergum (Fig. 43E) entire. Spermatheca
not observable.
Biology and Ecology. Stenus giushin is distributed in the mountainous regions of Kyushu.
The beetles inhabit leaf litter heaped in the natural forests and also near the mountain torrents.
Remarks. Stenus guishin is allied to S. zaishin, but it is clearly separable from the latter by
the 7th ventrite of male with posteromedian depression larger (Fig. 43A), the aedeagal median
lobe with apicolateral corners more distinctly developed and apicolateral teeth distinctly larger(Fig. 43B), and the endophallic expulsion hook broader and thicker (Fig. 43B).
Etymology. The speciﬁc epithet of this species “giushin” is derived from a name of ancient
Chinese mask.
Stenus zaishin Naomi(Figs. 44A–G, 129I)
Stenus zaishin Naomi, 1990d: 102; Herman, 2001: 2438; Naomi & Puthz, 2013: 138.
Type material examined. Holotype: ♂ (CBM), Mt. Tsurugi, Tokushima Pref., 15–17. x. 1980,
S. Naomi leg. Paratypes: 7 ♂7 ♀ (cN), same data as holotype.
Other material examined. [HONSHU] 1 ♂1 ♀, Mt. Ohdai, Nara Pref., 1. v. 1969, T. Ito leg.
[SHIKOKU] 1 ♂, Motokawa, Ino-machi, Kochi Pref., 18. viii. 2007, T. Miyata leg.
Distribution. Japan (Honshu, Shikoku).
Redescription. Male and female: Brachypterous; body 3.3–3.6 (fore body 1.5–1.7 mm) in
length, weakly shining, with antennae short. Body black; labrum black; antennae and legs reddish brown to dark red. Head with a pair of longitudinal depressions; punctures round to elliptical, very dense. Pronotum with surface very weakly uneven; punctures round to elliptical, very
dense, sometimes two or more punctures combined. Elytra with surface uneven; punctures roundto elliptical, very dense, somewhat rough. Legs relatively short; tarsi short, with 4th tarsomere

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Fig. 44. Stenus zaishin Naomi (A, C–G, Tsurugi, Tokushima; B, Ohdaigahara, Nara). A, 5th to 8th ventrites ofmale; B, 9th and 10th terga of male; C, endophallic basal tube; D, endophallic expulsion hook; E, aedeagus;
F, 9th ventrite of male; G, apex of gonocoxite. Scale 1: 0.3 mm for A; scale 2: 0.2 mm for B, E, F; scale 3: 0.1
mm for C, D, G.

The Steninae of Japan Part 1

123very weakly bilobed. Abdomen relatively wide to wide 3rd to 5th or 6th terga each with 3 short,basi-longitudinal keels; punctures round to elliptical, dense, small and distinct in anterior segments, while punctures in posterior segments elliptical, moderately dense, very small and regular.
Lateroventrites dorsomesial or horizontal in position, narrow, punctate.
Male: Fifth ventrite (Fig. 44A) posteromedially with a very shallow emargination; 6th ventrite (Fig. 44A) posteromedially with a semicircular ﬂat area, which is very shallowly emarginate
posteriorly and furnished with several moderately long setae at posterolateral corners; 7th ventrite (Fig. 44A) posteromedially with a semicircular depression, which is arcuately emarginate
posteriorly and furnished with short setae at posterolateral corners; 8th ventrite (Fig. 44A) posteromedeally with a medium-sized emargination, and centrally with a shallow depression, whichbecomes shallower posteriorly; 9th tergum (Fig. 44B) with ventral apophyses moderately long;
9th ventrite (Fig. 44F) elongate, ﬁnely serrate posteriorly, with stem elongate-rectangular inshape, apicolateral teeth each bi- or trifurcate apically, apicolateral setae moderately long; 10th
tergum (Fig. 44D) entire. Aedeagal median lobe (Fig. 44B) elongate, almost uniformly narrowed
apically, with the lanceolate apex; apical sclerotized area anteromedially with a U-shaped emargination, and covered with very ﬁne setae along the rim of emargination; apicomedian subtransparent area elongate; apicolateral teeth small, sclerotized, pointed, each located at the mesial
margin of lateral rim. Endophallic median longitudinal bands (Fig. 44E) short; expulsion hook
(Fig. 36E, D) transverse, with anterior arms turning anterolaterally; basal tube (Fig. 44E, C)
large, baculiform. Parameres (Fig. 44E) slender, almost straight; apical area short, swollen mesially, covered mesially with 20 to 25 short setae.
Female: Eighth ventrite rounded posteriorly; gonocoxites (Fig. 44G) each irregularly serrate
posteriorly, with apicolateral teeth bi- or trifurcate apically, apicolateral setae moderately long tolong. Spermatheca not observable.
Biology and Ecology. Stenus zaishin is distributed in the low to high mountainous regions.
The beetles inhabit litter in the natural forests.
Remarks. Stenus zaishin is allied to S. giushin, but it is clearly separable from the latter by
the7th ventrite of male with posteromedian depression smaller (Fig. 44A), the aedeagal median
lobe almost simply narrowed apically, without distinct apicolateral corners (Fig. 44E), the apicolateral teeth of median lobe distinctly smaller (Fig. 44E), and the expulsion hook narrower andthinner (Fig. 44E).
Etymology. The speciﬁc epithet of this species “zaishin” is derived from a name of ancient
Chinese mask.
Stenus kirin Naomi & Ito(Figs. 45A–G, 129J)
Stenus kirin Naomi & Ito, 2014: 281.
Type material examined. Holotype: ♂ (OMNH), Mt. Kojin, Yamato (Nara Pref.), 2. v. 1968,
T. Ito leg. Paratypes: 1 ♀ (cN), same data as holotype; 1 ♀ (cN), same locality as holotype, 30. vi.
1968, T. Ito leg.; 1 ♂ (cN), Mt. Tateri-kojin, Oku-koya, Nara Pref., 4. v. 1969, M. Goto leg.
Distribution. Japan (Honshu: Nara Pref.).
Redescription. Male and female: Brachypterous; body 2.9–3.1 (fore body 1.5–1.6 mm) in
length, moderately shining, with short antennae. Head and abdomen black; pronotum and elytra
dark red to black; labrum black; antennae reddish brown; legs reddish brown, with knees more or

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Fig. 45. Stenus kirin Naomi & Ito (Nara). A, endophallic basal tube; B, aedeagus; C, 9th ventrite of male; D,
expulsion hook; E, 9th and 10th terga of male; F, 9th, 10th terga and gonocoxites of female; G, apex of 8th
ventrite of male. Scale: 0.1 mm for A, D 0.2 mm for B, C, E–G.

The Steninae of Japan Part 1

125less infuscate. Head with a pair of longitudinal depressions; punctures round, dense. Pronotumwith surface weakly uneven; punctures round to subrugose, very dense. Elytra with surface very
weakly uneven; punctures very dense, rough. Legs short; tarsi short, moderately thick, with 4thtarsomere very weakly bilobed. Abdomen weakly narrowed posteriorly; 3rd to 5th terga eachwith 3 short, basi-longitudinal keels; punctures round to elliptical, dense, small and distinct inanterior segments, while punctures in posterior segments elliptical, dense, very small and regular.
Lateroventrites dorsomesial or horizontal in position, narrow, punctate.
Male: Sixth ventrite posteromedially with a triangular ﬂat area, which is very weakly emarginate posteriorly; 7th ventrite posteromedially with a shallow, semicircular depression, which isarcuately emarginate; 8th ventrite (Fig. 45G) posteromedially with a medium-sized emargination; 9th tergum (Fig. 45E) with ventral apophyses long, thin; 9th ventrite (Fig. 45C) elongate,
hardly serrate posteriorly, with stem elongate-rectangular in shape, apicolateral teeth each short,bi- or tridenticulate apically, apicolateral setae short; 10th tergum (Fig. 45E) entire. Aedeagal
median lobe (Fig. 45B) slender, gradually narrowed apically, pointed apically; apical sclerotizedarea subtriangular in shape, widely arcuately emarginate anteriorly; apicomedian subtransparent
area narrow, fusiform; apicolateral teeth very small, each located at the mesial margin of lateralrim. Endophallic median longitudinal bands (Fig. 45B) moderately long, broad, gradually divergent anteriorly; expulsion hook (Fig. 45B, D) transverse, with short antero-lateral arm and postero-lateral arm; basal tube (Fig. 45A, B) large, thick, weakly swollen apically. Parameres (Fig.
45B) slender, thin; apical area weakly swollen, furnished mesially with thin, short setae.
Female: Eighth ventrite rounded posteriorly; 9th tergum (Fig. 45F) without ventral apophyses; gonocoxites (Fig. 45F) each serrate posteriorly, with apicolateral tooth bi- or trifurcate apically, apicolateral setae short; 10th tergum (Fig. 45F) entire. Spermatheca not observable.
Biology and Ecology. Stenus kirin is distributed in the low mountainous regions. The beetles
inhabit litter in the natural forests.
Remarks. Stenus kirin is allied to S. giushin and S. zaishin, but it is clearly separable from thelatter two species by the aedeagal median lobe more slender, with the apicolateral teeth muchsmaller (Fig. 45B), and the endophallic expulsion hook with posterolateral arm longer and turning posterolaterally (Fig. 45D).
Etymology. The speciﬁc epithet of this species is derived from the Japanese noun ʻKirinʼ, thatis, the name of imaginary animal which is considered a symbol of ʻGood Luckʼ.
Stenus ohbayashii Naomi(Figs. 46A–G, 129K)
Stenus zaishin ohbayashii Naomi, 1997f: 141; Herman, 2001: 2438; Naomi & Puthz, 2013: 138.
Stenus ohbayashii Naomi, 1997f: Naomi & Ito, 2014: 287.
Type material examined. Holotype of S. zaishin ohbayashii: ♂ (CBM), Hontani, Mt. Odami,
Ehime Pref., 30. vii. 1994, M. Sakai leg.
Other material examined. [SHIKOKU]: 29 ♂24 ♀, Mt. Odami, Ehime Pref., 11. vii. 1994, E.
Yamamoto leg.
Distribution. (Shikoku: Ehime Pref.).
Redescription. Male and female: Brachypterous; body 3.4–3.6 mm (fore body 1.5–1.6 mm) in
length, weakly to moderately shining, with antennae short. Body almost entirely black; labrum
black; antennae and legs dark red. Head with a pair of longitudinal depression; punctures round126

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Fig. 46. Stenus ohbayashii Naomi (Odami, Ehime). A, 9th and 10th terga of male; B, apex of gonocoxite; C,
endophallic expulsion hook; D, basal tube; E, aedeagus; F, 9th ventrite of male; G, 6th to 8th ventrites ofmale. Scale 1: 0.2 mm for A, E, F, 0.1 mm for B–D; scale 2: 0.3 mm for G.

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127

to elliptical, very dense, distinct. Pronotum with surface weakly uneven; punctures round, very
dense, sometimes subrugous. Elytra with surface weakly uneven; punctures very dense, rough,somewhat subrugous. Legs relatively short; tarsi with 4th tarsomere very weakly bilobed. Abdomen moderately wide; 3rd to 6th terga each with 3 short, basi-longitudinal keels; punctures roundto elliptical, moderately dense, small and in anterior segments, while punctures in posterior segments elliptical, moderately dense and very small. Lateroventrites horizontal or dorsomesial in
position, narrow, punctate.
Male: Sixth ventrite (Fig. 46G) posteromedially with a semicircular ﬂat area, which is
weakly emarginate and furnished posteriorly with moderately long setae; 7th ventrite (Fig. 46G)
posteromedially with a large, deep depression, which is arcuately emarginate; 8th ventrite (Fig.
46G) posteromedially with a medium-sized emargination, centrally with a shallow depression,
which become shallower posteriorly; 9th tergum (Fig. 46A) with ventral apophyses moderately
long; 9th ventrite (Fig. 46F) elongate, weakly serrate posteriorly, with stem elongate-rectangularin shape, apicolateral teeth each short, bi- or trifurcate apically, apicolateral setae short; 10th tergum (Fig. 46A) entire. Aedeagal median lobe (Fig. 46E) weakly constricted near the middle, lanceolate and acute apically; apical sclerotized area long, deeply emarginate anteriorly to form a
V-shaped notch, covered sparsely with short setae along the rim of emargination; apicomediansubtransparent area elongate-subovoidal in shape; apicolateral teeth small, each located at theanterior corner of emargination. Endophallic median longitudinal bands (Fig. 46E) long, moderately wide; expulsion hook (Fig. 46E) transverse, thin, with its anterolateral arm turning anterolaterally, and also posteriorly with two short humps (Fig. 46C); basal tube (Fig. 46D, E) large,
simple, baculiform. Parameres (Fig. 46E) slender, weakly incurved; apical area short, weakly
swollen mesially, furnished mesially with 16 to 17 thin, short setae.
Female. Eighth ventrite rounded posteriorly; gonocoxites (Fig. 46B) each irregularly serrate
posteriorly, with apicolateral teeth short, bi- or trifurcate apically, apicolateral setae moderately
long. Spermatheca not observable.
Biology and Ecology. Stenus ohbayashii is distributed in the mountainous regions. The beetles inhabit leaf litter in the natural forests.
Remarks. Stenus ohbayashii was ﬁrst described by Naomi (1997f) as a subspecies of S.
zaishin Naomi, 1990d; and the subspecies was subsequently upgraded to a distinct species by
Naomi & Ito (2014). Given the highly structural similarity of their aedeagi, S. ohbayashii is thesister species of S. lanceolatus, but it is separable from the latter by the 7th ventrite of male withposteromedian depression smaller (Fig. 46G), the apical sclerotized area of aedeagal median lobe
anteriorly with the V-shaped emargination (Fig. 46E), the apicomedian subtransparent area muchlarger (Fig. 46E), and the endophallic expulsion hook with anterolateral arms shorter (Fig. 46C).
Etymology. The speciﬁc epithet of this species is named in honour of a Japanese coleopterist,
Dr. Nobuo Ohbayashi (Ehime Univ.).
Stenus lanceolatus Naomi(Figs. 47A–F, 129L)
Stenus lanceolatus Naomi, 1997f: 135; Herman, 2001: 2253; Naomi & Puthz, 2013: 138.
Type material examined. Holotype: ♂ (CBM), Kenashizen, Shinsho-mura, Okayama Pref.,14. v. 1994, O. Yamaji leg.
Other material examined. 2 ♂2 ♀, Hajiri, Hidaka-cho, Toyooka City, Hyogo Pref., 20. xi.

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Fig. 47. Stenus lanceolatus Naomi (Toyooka, Hyogo). A, 9th and 10th terga of male; B, aedeagus; C, 9th ventrite of male; D, 6th to 8th ventrites of male; E, 9th and 10th terga of female; F, gonocoxites. Scale 1: 0.2 mm
for A–C, E, F; scale 2: 0.3 mm for D.

The Steninae of Japan Part 1

1292007, M. Matsumoto leg.
Distribution. Japan (Honshu: Hyogo and Okayama Prefs.).
Redescription. Male and female: Brachypterous; body 3.0–3.7 mm (fore body 1.5–1.6 mm) in
length, weakly to moderately shining, with antennae relatively short. Head and abdomen black;pronotum and elytra dark red to black; labrum black; antennae dark red; legs dark red, withknees more or less infuscate. Head with a pair of longitudinal depressions; punctures round,
dense to very dense, small, distinct, two punctures sometimes fused. Pronotum with surface
uneven; punctures round, very dense, somewhat rough. Elytra with surface weakly uneven;punctures round, very dense, somewhat rough. Legs relatively short; tarsi with 4th tarsomere
very weakly bilobed. Abdomen wide; 3rd to 5th terga each with 3 short, basi-longitudinal keels;punctures round to elliptical, moderately dense, small and distinct in anterior segments, while
punctures in posterior segments elliptical, dense, very small, regular and distinct. Lateroventrites
horizontal or dorsomesial in position, narrow, punctate.
Male: Sixth ventrite (Fig. 47D) posteromedially with a semicircular ﬂat area, which is
weakly emarginate posteriorly; 7th ventrite (Fig. 47D) posteromedially with a very large, deep
depression, which is widely emarginate posteriorly, and distinctly ridged laterally; 8th ventrite(Fig. 47D) posteromedially with a medium-sized, V-shaped emargination, medially with a longitudinal furrow, which is narrowed anteriorly; 9th tergum (Fig. 47A) with ventral apophyses relatively thick, moderately long; 9th ventrite (Fig. 47C) elongate, weakly serrate posteriorly, withstem almost square in shape, apicolateral teeth each short, bi- or trifurcate apically, apicolateral
setae short. Aedeagal median lobe (Fig. 47B) lanceolate apically, with pointed apex; apical sclerotized area developed, long, declivous ventrolaterally, and partially covered with short, sparsesetae; apicomedian subtransparent area small, fusiform; apicolateral teeth small, pointed. Endophallic median longitudinal bands (Fig. 47B) with ventral bands moderately long, dorsal bands
short; expulsion hook (Fig. 47B) almost C-shaped, anterolateral arm slender with the small clawlike apex; basal tube (Fig. 47B) large, simple, baculiform. Parameres (Fig. 47B) slender, very
weakly incurved; apical area moderately long, very weakly swollen mesially, furnished mesiallywith 21 to 22 thin, short setae.
Female. Eighth ventrite rounded posteriorly; 9th tergum without ventral apophyses (Fig.
47E); gonocoxites (Fig. 47F) each irregularly serrate posteriorly, with apicolateral teeth short, bior trifurcate apically, apicolateral setae short; 10th tergum (Fig. 47E) entire. Spermatheca notobservable.
Biology and Ecology. Stenus lanceolatus is distributed in the plains to low mountainous
regions. The beetles inhabit leaf litter in the natural forests.
Remarks. Stenus lanceolatus is closely allied to S. ohbayashi, but it is separable from the latter by the 7th ventrite of male with posteromedian depression larger (Fig. 47D), the apical sclerotized area of aedeagal median lobe without anterior emargination (Fig. 47B), the apicomediansubtransparent area very small (Fig. 47B), and the endophallic expulsion hook with anterolateralarms longer (Fig. 47B).
Stenus ochiba Naomi & Puthz(Figs. 48A–G, 130A)
Stenus ochiba Naomi & Puthz, 1994a: 213; Herman, 2001: 2310; Naomi & Puthz, 2013: 138.
Type material examined. Holotype: ♂ (cP), Mt. Ontake, Nagano Pref., 3000 m, 23. ix. 1972,
R. Yosii leg. Paratypes: 1 ♂ (cN), same data as holotype; 1 ♂ (cN), Nakatsuya, Yoshiwa-mura,130

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Fig. 48. Stenus ochiba Naomi & Puthz (A, D–F, Yoshiwa, Hiroshima; B, C, G, Ontake, Nagano). A, 7th to 8th
ventrites of male; B, 9th and 10th terga of male; C, 9th ventrite of male; D, 9th and 10th terga of female; E,
apices of gonocoxites; F, G, aedeagus. Scale 1: 0.3 mm for A; scale 2: 0.2 mm for B–G.

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131

Hiroshima Pref., 28. vii. 1990, I. Okamoto leg.
Other material examined. [HONSHU] 1 ♀, Nakatsuya, Yoshiwa-mura, Hiroshima Pref., 7.
vi. 1987, S. Nomura leg.
Distribution. Japan (Honshu: Nagano and Hiroshima Prefs.).
Redescription. Male and female: Brachypterous; body 2.7–3.3 mm (fore body 1.5–1.6 mm) in
length, subcylindrical, moderately shining, with short antennae. Head and abdomen black; pronotum and elytra dark red to black; labrum black; antennae reddish brown; legs reddish brown,with knees more or less infuscate. Head with a pair of longitudinal depressions; punctures round,very dense, distinct. Pronotum with surface weakly uneven; punctures round, very dense, somewhat rough. Elytra with surface uneven; punctures very dense, rough. Legs short; tarsi short,moderately thick, with 4th tarsomere very weakly bilobed. Abdomen wide, weakly narrowed
posteriorly; 3rd to 5th terga each with 3 short, basi-longitudinal keels; punctures moderately
round to elliptical, dense and distinct in anterior segments, while punctures in posterior segments
moderately dense, very small and regular. Lateroventrites horizontal or dorsomesial in position,
narrow, punctate.
Male: Seventh ventrite (Fig. 48A) posteromedially with a subtrapezoidal depression, whichis arcuately emarginate posteriorly; 8th ventrite (Fig. 48A) posteromedially with a medium-sized
emargination, and centrally with an elongate-bell-shaped depression, which becomes gradually
shallower posteriorly; 9th tergum (Fig. 48B) with ventral apophyses long, straight, thin; 9th ventrite (Fig. 48C) elongate, ﬁnely serrate posteriorly, with stem rounded anteriorly, apicolateral
teeth each short, bi- or tridenticulate apically, apicolateral setae short; 10th tergum (Fig. 48B)
transverse, entire. Aedeagal median lobe (Fig. 48F, G) strongly narrowed apically behind apicolateral corners, with apex narrow but still rounded; apical sclerotized area anteromedially covered with short sparse setae; apicomedian subtransprarent area small, elliptical; apicolateral teeth
very small, each located at the mesial margin of lateral rim. Endophallic median longitudinalbands (Fig. 48F, G) with ventral bands moderately long, each gradually narrowed anteriorly, dorsal bands short; expulsion hook (Fig. 48F, G) transverse, thin, with its anterolateral arm a little
longer than postero-lateral arm; basal tube (Fig. 48F, G) large, simple, baculiform. Parameres(Fig. 48F, G) slender, thin, almost straight; apical area weakly swollen mesially, furnished mesially with very short setae (Fig. 48F) or with moderately long setae (Fig. 48G).
Female: Eighth ventrite rounded posteriorly; 9th tergum (Fig. 48D) without ventral apophyses; gonocoxites (Fig. 48E) each irregularly serrate posteriorly, with apicolateral teeth short,bifurcate apically, apicolateral setae moderately long; 10th tergum (Fig. 48D) entire. Spermatheca not observable.
Biology and ecology. S. ochiba is distributed in the low and high mountainous regions. The
beetles inhabit leaf litter in the natural forests.
Remarks. Stenus ochiba is closely allied to S. satushin and S. nipponomontanus, but it is separable from the latter two species by the 6th ventrite of male without modiﬁcations, and theaedeagal median lobe with apex narrowly but distinctly rounded (Fig. 48F, G). Presently, S.
ochiba has been collected from two distantly separated localities (alpine zone of Mt. Ontake,central Honshu and lowland of Hiroshima, western Honshu). The aedeagus shows slight morphological difference between these two populations with respect to the length of parameral setae(Naomi & Puthz, 1994a), but we treat here the difference as an infraspeciﬁc variation.
Etymology. The speciﬁc epithet of this species is derived from the Japanese noun ʻOchibaʼ,
which means “fallen leaves”; and the beetles inhabit leaf litters or fallen leaves.

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Stenus satushin Naomi & Puthz(Figs. 49A–G, 130B)
Stenus satushin Naomi & Puthz, 1994a: 212; Herman, 2001: 2378; Naomi & Puthz, 2013: 138.
Type material examined. Holotype: ♂ (CBM), Mt. Takanawa, Hojo City, Ehime Pref., 14. iv.
1991, I. Okamoto leg. Paratypes: 1 ♂ (cN), Mt. Takanawa, Hojyo City, Ehime Pref., 14. iv. 1991,
I. Okamoto leg.; 2 ♂ (cN), same locality, 30. iv. 1991, I. Okamoto leg.; 1 ♂ (cN), same locality, 6.
v. 1991, I. Okamoto leg.; 1 ♂ (cN), same locality, 24. viii. 1991, I. Okamoto leg.
Other material examined. [HONSHU]: 1 ♂1 ♀, Mado Pass, Tanbara-cho, Ehime Pref., 27. xi.
1968, M. Yoshida leg.
Distribution. Japan (Shikoku: Ehime Pref.).
Redescription. Male and female: Brachypterous; body 3.2–3.3 mm (fore body 1.5–1.6 mm) in
length, subcylindrical, moderately shining, with short antennae. Head and abdomen black; pronotum and elytra dark red to black; labrum black; antennae reddish brown; legs reddish brown,with knees more or less infuscate. Head with a pair of longitudinal depressions; punctures roundto elliptical, very dense, distinct. Pronotum with surface weakly uneven; punctures round, very
dense, somewhat rough. Elytra with surface uneven; punctures round to elliptical, very dense,
somewhat subrugous. Legs short; tarsi short, with 4th tarsomere very weakly bilobed. Abdomenwide; 3rd to 5th or 6th terga each with 3 short, basi-longitudinal keels; punctures round to elliptical, moderately dense, small and distinct in anterior segments, while punctures in posterior segments moderately dense, very small and regular. Lateroventrites dorsomesial or horizontal in
position, narrow, punctate.
Male: Sixth ventrite (Fig. 49D) posteromedially with a small, shallow semicircular depression, which is shallowly emarginate posteriorly; 7th ventrite (Fig. 49D) posteromedially with abell-shaped depression, which is emarginate posteriorly; 8th ventrite (Fig. 49D) posteromediallywith a medium-sized emargination, and centrally with an elongate depressed area which becomes
gradually shallower posteriorly; 9th tergum (Fig. 49A) with ventral apophyses moderately long;
9th ventrite (Fig. 49E) elongate, hardly serrate posteriorly, with stem rectangular in shape, apicolateral teeth each short, di- or trifurcate apically, apicolateral setae short; 10th tergum (Fig. 49A)
entire. Aedeagal median lobe (Fig. 49B) nearly violin-shaped, pointed apically; apical sclerotizedarea medially covered with short, sparse setae; apicomedian subtransprarent area rather small,
elliptical; apicolateral teeth very small, each located at the mesial margin of lateral rim. Endophallic median longitudinal bands (Fig. 49B) moderately long; expulsion hook (Fig. 49B) transverse but weakly arched posteriorly, with its anterolateral arm longer than posterolateral arm(Fig. 49G); basal tube (Fig. 49B, C) large, baculiform. Parameres (Fig. 49B) slender, thin,weakly incurved; apical area weakly swollen mesially, furnished mesially with 21 to 22 setae(Fig. 49B).
Female: Eighth ventrite almost rounded posteriorly; gonocoxites (Fig. 49F) each irregularly
serrate posteriorly, with apicolateral tooth indistinct (or 2 or 3 teeth of various size at apicolateralpart, apicolateral setae moderately long. Spermatheca not observable.
Biology and ecology. Stenus satushin is distributed in the low mountainous regions. The beetles inhabit leaf litter in the natural forests.
Remarks. Stenus satushin is closely allied to S. nipponomontanus, but this species is separable from the latter by the 6th and 7th ventrites of male each with a smaller depression (Fig. 49D),
the aedeagal median lobe with its lateral rim narrower, and apical sclerotized area shorter andThe Steninae of Japan Part 1

133

Fig. 49. Stenus satushin Naomi (A, D–F, Tanbara, Ehime; B, C, G, Hojyo, Ehime). A, 9th and 10th terga of
male; B, aedeagus; C, endophallic basal tube; D, 6th to 8th ventrites of male; E, 9th ventrite of male; F, apexof gonocoxite; G, endophallic expulsion hook. Scale 1: 0.2 mm for A, B, E, 0.1 mm for C, F, G; scale 2: 0.3
mm for D.

narrower (Fig. 49B), and the endophallic expulsion hook wider, with its anterolateral arm relatively long (Fig. 49G).
Etymology. The speciﬁc epithet of this species “satushin” is derived from a name of ancient134

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Chinese mask.
Stenus nipponomontanus Naomi(Figs. 50A–G, 130C)
Stenus nipponomontanus Naomi, 1988c: 48; Herman, 2001: 2301; Naomi & Puthz, 2013: 138.
Type material examined. Holotype: ♀ (KUF), Ohdaigahara, Nara Pref., 25–26. vi. 1981, S.
Naomi leg. Paratypes: 1 ♂1 ♀ (cN), same data as holotype.
Other material examined. [HONSHU] 1 ♂, Ohdaigahara, Nara Pref., 20. vii. 1975, T. Itoleg.; 1 ♂1 ♀, Mt. Kasuga, Nara Pref., 4. v. 1969, Y. Watanabe leg.; 2 ♂1 ♀, same locality, 3. iv.
1992, T. Kishimoto leg.
Distribution. Japan (Honshu: Nara Pref.).
Redescription. Male and female: Brachypterous; body 3.2–3.7 mm (fore body 1.6–1.8 mm) in
length, subcylindrical, moderately shining, with short antennae. Body almost entirely black;labrum black; antennae reddish brown; legs dark red to black. Head with a pair of longitudinal
depressions; punctures round, very dense, distinct. Pronotum with surface uneven; puncturesround, very dense, various in size, somewhat rough. Elytra with surface uneven; punctures roundto elliptical, very dense, various in size, somewhat subrugous. Legs short; tarsi short, with 4thtarsomere very weakly bilobed. Abdomen wide; 3rd to 5th terga each with 3 short, basi-longitudinal keels; punctures round, moderately dense, small and various in size in anterior segments,
while punctures in posterior segments round to elliptical, moderately dense and very small. Lateroventrites dorsomesial or horizontal in position, narrow, punctate.
Male: Sixth ventrite (Fig. 50C) posteromedially with a shallow, semicircular depression,
which is shallowly emarginate; 7th ventrite (Fig. 50C) posteromedially with a large, bell-shaped
depression, which is arcuately emarginate posteriorly; 8th ventrite (Fig. 50C) posteromediallywith a small, U-shaped emargination, and medially with an elongate depressed area whichbecomes shallower and broader posteriorly; 9th tergum (Fig. 50D) with ventral apophyses short,broad; 9th ventrite (Fig. 50E) elongate, very ﬁnely serrate posteriorly, with stem elongate-rectangular in shape, apicolateral teeth each short, bi- or tridenticulate apically, apicolateral setae moderately long; 10th tergum (Fig. 50D) entire. Aedeagal median lobe (Fig. 50A) nearly violinshaped, acutely pointed apically; apical sclerotized area long, elongate-triangular in shape,
anteromedially covered with short, sparse setae; apicomedian subtransprarent area small, ovoidal; apicolateral teeth very small, each located at the mesial margin of lateral rim. Endophallic
median longitudinal bands (Fig. 50A) with ventral bands long, thin, dorsal bands short; explusion
hook (Fig. 50A) transverse but weakly arched posteriorly, anterolaterally with a small tooth, posterolaterally with a triangular tooth (Fig. 50F); basal tube (Fig. 50A, B) large, baculiform. Parameres (Fig. 50A) very thin, slender, almost uniformly incurved; apical area moderately long,
hardly swollen mesially, furnished mesially with 20 to 21 short setae (Fig. 50A).
Female: Eighth ventrite rounded posteriorly; gonocoxites (Fig. 50G) each irregularly serrate
posteriorly, with apicolateral tooth indistinct or bifurcate apically, apicolateral setae moderately
long. Spermatheca not observable.
Biology and ecology. Stenus nipponomontanus is distributed in the low to high mountainous
regions. The beetles inhabit leaf litter in the natural forests.
Remarks. Stenus nipponomontanus is closely allied to S. satushin, but this species is separable from the latter by the 6th and 7th ventrites of male each with a larger depression (Fig. 50C),

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Fig. 50. Stenus nipponomontanus Naomi (Ohdaigahara, Nara). A, aedeagus; B, endophallic basal tube; C, 6th to
8th ventrites of male; D, 9th and 10th terga of male; E, 9th ventrite of male; F, expulsion hook; G, apex of
gonocoxite. Scale 1: 0.2 mm for A, D, E, 0.1 mm for B, F, G; scale 2: 0.3 mm for C.

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the aedeagal median lobe with its lateral rim wider, and apical sclerotized area longer and wider(Fig. 50A), and the endophallic expulsion hook narrower, anterolaterally with a small tooth (Fig.
50F).
Stenus wasamatanus Puthz(Figs. 51A–G, 130D)
Stenus wasamatanus Puthz, 2001c: 43; Naomi & Puthz, 2013: 138.
Type material examined. Holotype: ♂ (SMNS), type locality: Mt. Wasamata, Nara Pref.
[examined by Puthz]. Paratypes: 1 ♂1 ♀ (cN), Mt. Wasamata, Nara Pref., 11. vii. 1999, V. Puthz
leg.
Other material examined. [HONSHU] 5 ♂5 ♀, Mt. Wasamata, Kami-kitayama, Nara Pref.,11. vii. 1999, M. Maruyama leg.; 2 ♂, same locality, 14-15. vi. 1997, Y. Hayashi leg.; 1 ♂1 ♀, Mt.
Inamura, Oomine, Nara Pref., 5. v. 1994, T. Ito leg.; 2 ♂1 ♀, same locality, 1. vi. 1985. T. Ito leg.
Distribution. Japan (Honshu: Nara Pref.).
Redescription. Male and female: Brachypterous; body 2.7–3.3 mm (fore body 1.5–1.6 mm) in
length, weakly shining, with short antennae. Body black; labrum black; antennae dark red; legs
reddish brown, with knees more or less infuscate. Head with a pair of distinct longitudinal
depressions; punctures round, very dense, regular, distinct. Pronotum with surface weakly
uneven; punctures round, very dense, somewhat rough. Elytra with surface uneven; puncturesround to elliptical, very dense, somewhat rough. Legs moderate in length; tarsi short, with 4thtarsomere very weakly bilobed. Abdomen moderately wide to wide; 3rd to 5th or 6th terga eachwith 3 short, basi-longitudinal keels; punctures round to elliptical, sparse to moderately dense,and small in anterior segments, while punctures in posterior segments round to elliptical, sparseto moderately dense, and very small. Lateroventrites dorsomesial or horizontal in position, narrow, punctate.
Male: Sixth ventrite (Fig. 51E) posteromedially with a very shallow emargination, which isfurnished sparsely with setae along the posterior margin; 7th ventrite (Fig. 51E) posteromediallywith a bell-shaped depression, which is arcuately emarginate, and furnished sparsely with shortsetae along the posterior margin; 8th ventrite (Fig. 51E) posteromedially with a medium-sized
emargination; 9th tergum (Fig. 51C) with ventral apophyses moderately long; 9th ventrite (Fig.
51G) elongate, very ﬁnely serrate posteriorly, with stem elongate-subrectangular in shape, apicolateral teeth each short, bi- or tridenticulate apically, apicolateral setae short; 10th tergum (Fig.
51C) transverse, gently rounded posteriorly. Aedeagal median lobe (Fig. 51B) nearly spindleshaped, with the short lanceolate apex; apical sclerotized area furnished with short (Fig. 51B) or
moderately long setae on anterolateral parts; apicomedian subtransparent area medium-sized,
ovoidal in shape; apicolateral teeth small, each located at the lateral margin just before the apicalsclerotized area. Endophallic median longitudinal bands (Fig. 51B) moderately long and broad;
expulsion hook (Fig. 51B) almost arc-shaped, with anterolateral arm distinctly longer than postero-lateral arm (Fig. 51D); basal tube (Fig. 51A, B) large, baculiform. Parameres (Fig. 51B)
thin, weakly incurved; apical area weakly swollen mesially, furnished mesially with 18 to 20
short setae.
Female: Eighth ventrite rounded posteriorly; gonocoxites (Fig. 51F) each serrate posteriorly,
with apicolateral tooth bi- or trifurcate apically, apicolateral setae moderately long. Spermatheca
not observable.

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Fig. 51. Stenus wasamatanus Puthz (A, B, D, G, Ohmine, Nara; C, E, F, Wasamata, Nara). A, endophallic basal
tube; B, aedeagus; C, 9th and 10th terga of male; D, endophallic expulsion hook; E, 6th to 8th ventrites ofmale; F, gonocoxite; G, 9th ventrite of male. Scale 1: 0.2 mm for B, C, G, 0.1 mm for A, D, F; scale 2: 0.3 mm
for E.

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Biology and Ecology. Stenus wasamatanus is distributed in the mountainous regions. The
beetles inhabit leaf litter in the natural forests.
Remarks. Stenus wasamatanus is allied to S. corrugatus, but it is separable from the latter by
the 10th tergum of male more strongly transverse (Fig. 51C), the aedeagal median lobe with apical part lanceolate, with apicolateral teeth located at the lateral margins (Fig. 51B), the endophallic median longitudinal band shorter (Fig. 51B), and the basal tube weakly swollen apically (Fig.
51A).
Stenus corrugatus Naomi & Shimada(Figs. 52A–F, 130E)
Stenus corrugatus Naomi & Shimada, 2008: 54; Naomi & Puthz, 2013: 138.
Type material examined. Holotype: ♂ (CBM), Ooku, Okinoshima-cho, Dogo Is., Oki Isls.
Shimane Pref., 7. x. 2004, T. Shimada leg. Paratypes: 1 ♂ (cN), same data as holotype; 1 ♂ (cN),
Mt. Tokibari, Saigo-cho, Dogo Is., Oki Isls. Shimane Pref., 12. vi. 2003, T. Shimada leg.
Distribution. Japan (Honshu: Oki Isls.).
Redescription. Male: Brachypterous; body 2.8–3.2 mm (fore body 1.5–1.7 mm) in length,
weakly shining, with short antennae. Body black; labrum black; antennae dark red; legs reddish
brown, with knees more or less infuscate. Head with a pair of distinct longitudinal depressions;punctures round to elliptical, very dense, distinct. Pronotum with surface weakly uneven; punctures round, very dense, somewhat rough. Elytra with surface rather uneven; punctures very
dense, rough. Legs moderate in length; tarsi short, with 4th tarsomere very weakly bilobed.
Abdomen weakly narrowed posteriorly; 3rd to 5th terga each with 3 short, basi-longitudinalkeels; punctures round to elliptical, moderately dense to dense, and small to moderate in size inanterior segments, while punctures in posterior segments round to elliptical, moderately dense,
very small and regular. Lateroventrites dorsomesial or horizontal in position, narrow, punctate.
Sixth ventrite (Fig. 52D) posteromedially with a shallow, subtriangular depression, which is
weakly emarginate posteriorly; 7th ventrite (Fig. 52D) posteromedially with a moderately deep
depression, which is arcuately emarginate; 8th ventrite (Fig. 52D) posteromedially with a
U-shaped emargination; 9th tergum (Fig. 52C) with ventral apophyses moderately long; 9th ventrite (Fig. 52B) elongate, irregularly ﬁnely serrate posteriorly, with stem constricted basally, subtrapezoidal in shape, apicolateral teeth each short, bi- or tridenticulate apically, apicolateral setae
short; 10th tergum (Fig. 52C) entire. Aedeagal median lobe (Fig. 52A) gradually narrowed apically behind the middle (so that the apicolateral corner is not formed), with a small apicomedianprojection; apical sclerotized area almost triangular in shape, partly covered with short setae; apicomedian subtransparent area elongate-elliptical in shape; apicolateral teeth small, each locatedat the mesial margin of lateral rim. Endophallic median longitudinal bands (Fig. 52A) with ventral bands moderately long, broad, dorsal bands short to moderately long; expulsion hook (Fig.
52A) almost arc-shaped, with the posterolateral arm short, a small hump located ventrally near
the base of posterolateral arm (Fig. 52F); basal tube (Fig. 52A) simple, baculiform, weakly bent
dorsally near the middle (Fig. 52E). Parameres (Fig. 52A) thin, with stem weakly incurved; apical area weakly swollen mesially, covered mesially with 22 to 26 short setae.
Female: Unknown.
Biology and Ecology. S. corrugatus is an insular Stenus species. The beetles inhabit leaf litterin the natural forests of mountainous regions in Oki Islands.

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Fig. 52. Stenus corrugatus Naomi & Shimada (Dogo Is., Shimane). A, aedeagus; B, 9th ventrite of male; C, 9th
and 10th terga of male; D, 6th to 8th ventrites of male; E, endophallic basal tube; F, expulsion hook. Scale:
0.2 mm for A–C, 0.1 mm for E, F, 0.25 mm for D.

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Remarks. Stenus corrugatus is allied to S. wasamatanus, but it is separable from the latter by
the 10th tergum of male narrower (Fig. 52C), the aedeagal median lobe with apical part almost
triangular in shape, with apicolateral teeth located at the mesial margins of lateral rims (Fig.
52A), the endophallic median longitudinal band longer (Fig. 52A), and the basal tube narrowly
apically (Fig. 52E).
Stenus hagai Naomi(Figs. 53A–F, 130F)
Stenus hagai Naomi, 1997f: 138; Herman, 2001: 2211; Naomi & Puthz, 2013: 138.
Stenus zimmermanni curvaticellus Naomi, 1997f: 142 (partim).
Type material examined. Holotype of S. hagai: ♂ (CBM), Kurakake Pass, Irihirose-mura,
Niigata Pref., 11. vi. 1995, K. Haga leg. Paratypes of S. hagai: 1 ♀ (cN), same data as holotype.
Paratype of S. zimmermanni curvaticellus: 1 ♂ (cN), Near Atsumi, Yamagata Pref., 16. vii. 1960,
Y. Shibata leg.
Distribution. Japan (Honshu: Yamagata and Niigata Prefs.).
Redescription. Male and female: Brachypterous; body 3.5–3.7 mm (fore body 1.6–1.7 mm) in
length, weakly to moderately shining, with antennae relatively short. Head and abdomen black;pronotum and elytra dark red; labrum black; antennae dark red; legs reddish brown, with knees
more or less infuscate. Head with a pair of longitudinal depressions; punctures round, dense,
small, almost regular. Pronotum with surface weakly uneven; punctures round, very dense. Elytra
with surface uneven; punctures round, very dense, rough, subrugous. Legs short; tarsi with 4thtarsomere very weakly bilobed. Abdomen wide, weakly convex above; 3rd to 5th terga each with
3 short, basi-longitudinal keels; punctures round to elliptical, moderately dense, small and distinct in anterior segments, while puncture in posterior segments round to elliptical, moderately
dense, very small and regular. Lateroventrites horizontal or mesiodorsal in position, narrow,
punctate.
Male: Seventh ventrite (Fig. 53B) posteromedially with a large, bell-shaped depression,
which is arcuately emarginate; 8th ventrite (Fig. 53B) posteromedially with a relatively small
emargination, and centrally with an elongate-subovoidal depression, which becomes shallower
posteriorly; 9th tergum (Fig. 53A) with ventral apophyses moderately long, thick; 9th ventrite(Fig. 53E) elongate, very ﬁnely serrate posteriorly, with stem elongate-subrectangular in shape,
apicolateral teeth each short, indistinctly bi- or tridenticulate apically, apicolateral setae short;
10th tergum (Fig. 53A) entire. Aedeagal median lobe (Fig. 53D) elongate-ovoidal in shape,
pointed apically; apical sclerotized area triangular in shape, ﬂat ventrally, partly covered withsparse setae of different length, with a dense tuft of long setae just behind the apicolateral hump;apicomedian subtransparent area large, subovoidal in shape; apicolateral humps medium-sized,rounded, each located near lateral margin of median lobe. Endophallic median longitudinal bands(Fig. 53D) rather broad, moderately long; expulsion hook (Fig. 53D) almost C-shaped, withanterolateral arm long, thin; basal tube (Fig. 53D) large, baculiform. Parameres (Fig. 53D) slender; stem mesially with several short setae; apical area weakly swollen mesially, furnished mesially with 14 to 15 thin, short setae.
Female: Eighth ventrite rounded posteriorly; 9th tergum (Fig. 53F) without ventral apophyses; gonocoxites (Fig. 53C) each irregularly serrate posteriorly, with apicolateral teeth short,incurved, bi- or tridenticulate apically, apicolateral setae short; 10th tergum (Fig. 53F) entire.

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Fig. 53. Stenus hagai Naomi (Irihirose, Niigata). A, 9th and 10th terga of male; B, 7th to 8th ventrites of male;C, gonocoxites; D, aedeagus; E, 9th ventrite of male; F, 9th and 10th terga of female. Scale 1: 0.2 mm for A,
C–F; scale 2: 0.3 mm for B.

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Spermatheca not observable.
Biology and ecology. Stenus hagai is distributed in the mountainous regions. The beetles
inhabit leaf litter in the natural forests.
Remarks. Stenus hagai is allied to S. curvaticellus, but it is separable from the latter by the
5th and 6th ventrites of male without modiﬁcations, and the aedeagal median lobe elongate-ovoidal in shape, with apical sclerotized area triangular in shape, ﬂat ventrally, and with a dense tuft
of long setae just behind the apicolateral hump (Fig. 53D). Notice here that the apical sclerotizedarea of median lobe is usually weakly convex ventrally in Stenus, and thus the ﬂat condition of
apical sclerotized area is a diagnostic (apomorphic) condition for the species in which the condition is found (see also descriptions of S. intumescens and S. yasutoshii).
Etymology. This species is named in honour of Mr. Kaori Haga (Saitama) who collected thetype material of this species.
Stenus curvaticellus Naomi(Figs. 54A–G, 130G)
Stenus zimmermanni curvaticellus Naomi, 1997f: 142; Herman, 2001: 2439; Naomi & Puthz,
2013: 138.
Stenus curvaticellus Naomi, 1997f: Naomi & Ito, 2014: 288.
Type material examined. Holotype of S. zimmermanni curvaticellus: ♂ (CBM), Nabetani,
Tatsunokuchi-cho, Ishikawa Pref., 21. iv. 1995, Y. Sugie leg. Paratypes of S. zimmermanni curvaticellus: 1 ♂ (cN), same locality, 10. iv. 1995, Y. Sugie leg.; 1 ♂ (cN), same locality, 13. iv.
1995, Y. Sugie leg.; 1 ♀ (cN), same locality, 15. iv. 1995, Y. Sugie leg.; 1 ♀ (cN), same locality,
18. iv. 1995, Y. Sugie leg.; 1 ♂ (cN), same locality, 4. vi. 1995, Y. Sugie leg.; 1 ♀ (cN), same
locality, 11. iv. 1995, Y. Sugie leg.
Other material examined. [HONSHU] 1 ♂1 ♀, Ohno City, Fukui Pref., 24. vii. 2010, M. Sato
leg.
Distribution. Japan (Honshu: Ishikawa and Fukui Prefs.).
Redescription. Male and female: Brachypterous; body 3.3–4.3 mm (fore body 1.5–2.1 mm) in
length, weakly to moderately shining, with antennae relatively short. Body black, slightly withreddish tinge on pronotum and elytra; labrum black; antennae reddish brown; legs reddish
brown, with knees more or less infuscate. Head with a pair of longitudinal depressions; puncturesround to elliptical, dense to very dense, small. Pronotum with surface weakly uneven; puncturesround, very dense, various in size. Elytra with surface uneven; punctures round, very dense,
sometimes subrugous. Legs short; tarsi with 4th tarsomere very weakly bilobed. Abdomen moderately wide, well convex above; 3rd to 5th terga each with 3 short, basi-longitudinal keels;punctures round to elliptical, moderately dense to dense, and small in anterior segments, while
punctures in posterior segments round to elliptical, moderately dense and very small. Lateroventrites mesiodorsal in position, narrow, punctate.
Male: Fifth ventrite (Fig. 54A) posteromedially with a ﬂat area, which is covered sparselywith setae; 6th ventrite (Fig. 54A) posteromedially with a very shallow depression, which is shallowly emarginate, and covered sparsely with setae; 7th ventrite (Fig. 54A) posteromedially witha moderately deep depression, which is arcuately emarginate, and covered densely with short,thin setae; 8th ventrite (Fig. 54A) posteromedially with a medium-sized emargination, and centrally with an elongate-subovoidal depression which becomes shallower posteriorly; 9th tergum

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Fig. 54. Stenus curvaticellus Naomi (A, E, Ohno, Fukui; B–D, F, G, Nabetani, Ishikawa). A, 5th to 8th ventrites
of male; B, 9th ventrite of male; C, apex of gonocoxite; D, endophallic expulsion hook; E, 9th and 10th tergaof male; F, aedeagus; G, basal tube. Scale 1: 0.3 mm for A; scale 2: 0.2 mm for B, E, F, 0.1 mm for C, D, G.

144

Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz(Fig. 54E) with ventral apophyses short, moderately thick; 9th ventrite (Fig. 54B) elongate, irregularly serrate posteriorly, with stem elongate-subrectangular in shape, apicolateral teeth each
short, bi- or trifurcate apically, apicolateral setae short; 10th tergum (Fig. 54E) entire. Aedeagal
median lobe (Fig. 54F) nearly spindle-shaped, nearly lanceolate apically; apical sclerotized area
anteriorly with a V-shaped emargination, and furnished with short setae along the rim of emargination; apicomedian subtransparent area elongate-subovoidal in shape; apicolateral teeth
medium-sized, each located at the mesial margin of lateral rim. Endophallic median longitudinalbands (Fig. 54F) long, rather broad; expulsion hook (Fig. 54D, F) thin, almost transverse, withanterolateral arm relatively long; basal tube (Fig. 54F, G) large, baculiform. Parameres (Fig. 54F)
slender, weakly incurved; stem mesially with several short setae just before the apical area; apical area hardly swollen mesially, and furnished mesially with 16 to 18 thin setae.
Female: Eighth ventrite rounded posteriorly; gonocoxites (Fig. 54C) each apicomesiallywith a blunt tooth, apicolateral tooth bi- or trifurcate apically, apicolateral setae moderately long.
Spermatheca not observable.
Biology and ecology. Stenus curvaticellus is distributed in the plains and mountainous
regions. The beetles inhabit leaf litter in the natural forests.
Remarks. Stenus curvaticellus was ﬁrst described by Naomi (1997f) as a subspecies of S. Stenus zimmermanni; and this subspecies was later upgraded to a distinct species by Naomi & Ito(2014). The present study shows that S. curvaticellus is probably closely allied to S. hagai (butnot to S. zimmermanni); and this species is separable from S. hagai by the 5th and 6th ventrites
of male with modiﬁcations (Fig. 54A), the aedeagal median lobe nearly spindle-shaped, lanceolate apically, with apical sclerotized area weakly convex ventrally, and furnished with short setae
along the rim of anterior emargination (Fig. 54F).
Stenus intumescens Naomi, Nomura & Puthz sp. nov.
(Figs. 55A–F, 130H)
Type material examined. [HONSHU] Holotype, ♂ (NSMT-I-C-200318 in NMNST), Uchinokaya, Ina, Nagano Pref., 13. viii. 1999, Y. Hayashi leg.
Distribution. Japan (Honshu: Nagano Pref.).
Description. Male: Brachypterous; body 3.7 mm (fore body 1.8 mm) in length, weakly shining, with antennae short. Body black; labrum black; antennae dark red; legs reddish brown, withknees more or less infuscate. Head with a pair of longitudinal depressions; punctures round to
elliptical, very dense, small. Pronotum with surface uneven; punctures round to almost round,very dense, somewhat rough. Elytra with surface uneven; punctures round to elliptical, very
dense, rough. Legs short, moderately thick; tarsi with 4th tarsomere very weakly bilobed. Abdomen moderately wide; 3rd to 5th terga each with 3 short, basi-longitudinal keels; punctures roundto elliptical, moderately dense to dense, and small in anterior segments, while punctures in posterior segments elliptical, moderately dense, and very small. Lateroventrites horizontal or mesiodorsal in position, narrow, punctate.
Five ventrite (Fig. 55A) posteromedially with a very short depressed area, which is very
weakly emarginate; 6th ventrite (Fig. 55A) posteromedially with a shallow depression, which isarcuately emarginate, and covered with short to moderately long setae; 7th ventrite (Fig. 55A)
posteromedially with a bell-shaped depression, which is arcuately emarginate, and covered withshort setae; 8th ventrite (Fig. 55A) posteromedially with a small emargination, and medially witha large, shallow, elongate depression which becomes shallower posteriorly; 9th tergum (Fig.

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Fig. 55. Stenus intumescens Naomi, Nomura & Puthz sp. nov. (Ina, Nagano). A, 5th to 8th ventrites of male; B,
9th and 10th terga of male; C, endophallic expulsion hook; D, aedeagus; E, basal tube; F, 9th ventrite of male.
Scale 1: 0.3 mm for A; Scale 2: 0.2 mm for B, D, F, 0.1 mm for E.

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55B) with ventral apophyses moderately long; 9th ventrite (Fig. 55F) elongate, hardly serrate
posteriorly, with stem elongate-rectangular in shape, apicolateral teeth each short, bi- or tridenticulate apically, apicolateral setae short; 10th tergum (Fig. 55B) entire. Aedeagal median lobe (Fig.
55D) violin-shaped, nearly lanceolate apically; apical sclerotized area ﬂat ventrally, partly covered with thin, short setae; apicomedian subtransparent area relatively small, elongate-ellipticalin shape; apicolateral humps large, rounded, each located at the lateral margins of apical sclerotized area. Endophallic median longitudinal bands (Fig. 55D) moderately long; expulsion hook
(Fig. 55D) transverse, very wide, weakly arched anteriorly, with anterolateral arm angulate laterally, sharply pointed anteriorly, posterolateral arm turning laterally, sharply pointed (Fig. 55C);
basal tube (Fig. 55D, E) large, baculiform. Parameres (Fig. 55D) slender, thin, weakly incurved;
apical area moderately long, furnished mesially with short setae.
Female: Unknown.
Biology and ecology. Only one male of Stenus intumescens was presently collected from themountainous region of Nagano (central Honshu). The beetle inhabits leaf litter in the natural forest.
Remarks. Stenus intumescens is allied to S. hagai and S. curvaticellus, but it is separablefrom the latter two species by the aedeagal median lobe violin-shaped, with apicolateral humplarger and located at the lateral margin of median lobe (Fig. 55D), and the endophallic expulsion
hook wider, with posterolateral arm turning laterally and sharply pointed (Fig. 55C).
Etymology. The speciﬁc epithet of this species is derived from the Latin participle “intumescens” which means “swelling”; and the apicolateral humps of median lobe are weakly swelling.
Stenus displicatus Naomi, Nomura & Puthz sp. nov.
(Figs. 56A–G, 130I)
Type material examined. Holotype: ♂ (NSMT-I-C-200319 in NMNST), Mt. Ohdai, Nara
Pref., 1. v. 1969, T. Ito leg. Paratypes: 2 ♂7 ♀, same data as holotype; 1 ♂1 ♀, Mt. Ohdai, Nara
Pref., 20. vii. 1975, T. Ito leg.; 1 ♂1 ♀, same locality, 20. x. 1985, M. Yasui leg.; 1 ♂ (cN),
Kouraibiro, Ise City, Mie Pref., 10. i. 1998, H. Yokozeki leg.; 1 ♂ (cN), Mt. Jinro, Ise City, Mie
Pref., 22. i. 2004, H. Yokozeki leg.; 1 ♂ (cN), Hirokuri Val., Miyakawa, Mie Pref., 12. vi. 1996,
H. Ichihashi leg.
Distribution. Japan (Honshu: Nara and Mie Prefs.).
Description. Male and female: Brachypterous; body small 3.3–3.6 mm (fore body: 1.5–1.7mm) in length, weakly shining, with antennae short. Body black; labrum black; antennae dark
red; legs reddish brown, with knees more or less infuscate. Head with a pair of longitudinal
depressions; punctures round, very dense, distinct. Pronotum with surface uneven; puncturesround, very dense, somewhat rough. Elytra with surface rather uneven; punctures round to elliptical, very dense, somewhat rough. Legs moderately long; tarsi short, with 4th tarsomere very
weakly bilobed. Abdomen moderately wide; 3rd to 5th or 6th terga each with 3 short, basi-longitudinal keels; punctures round to elliptical, moderately dense to dense, and small in anterior segments, while punctures in posterior segments round to elliptical, moderately dense to dense, andvery small. Lateroventrites horizontal or dorsomesial in position, narrow, punctate.
Male: Sixth ventrite (Fig. 56C) posteromedially with a very shallow emargination; 7th ventrite (Fig. 56C) posteromedially with a bell-shaped depression, which is shallowly emarginate
posteriorly; 8th ventrite (Fig. 56C) posteromedially with a small emargination, and centrally witha shallow, subovoidal depression; 9th tergum (Fig. 56B) with ventral apophyses straight, moder-

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Fig. 56. Stenus displicatus Naomi, Nomura & Puthz sp. nov. (Ohdaigahara, Nara). A, endophallic basal tube; B,
9th and 10th terga of male; C, 6th to 8th ventrites of male; D, expulsion hook; E, aedeagus; F, 9th ventrite ofmale; G, gonocoxite. Scale 1: 0.1 mm for A, D, G, 0.2 mm for B, E, F; scale 2: 0.3 mm for C.

ately long; 9th ventrite (Fig. 56F) elongate, very ﬁnely serrate posteriorly, with stem rectangularin shape, apicolateral teeth each short, bi- or trifurcate apically, apicolateral setae short; 10th tergum (Fig. 56B) entire. Aedeagal median lobe (Fig. 56E) wide, strongly narrowed apically behind
the rounded apicolateral corners, acutely pointed apically; apical sclerotized area almost pentago-

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nal in shape, covered anteriorly with sparse setae; apicomedian subtransparent area elongateelliptical in shape; apicolateral humps small, rounded, weakly projecting laterally, each locatedjust at the lateral margin behind apicolateral corner. Endophallic median longitudinal bands (Fig.
56E) long; expulsion hook (Fig. 56E) transverse, thin, very wide, weakly arched anteriorly, withanterolateral arm provided laterally with a small sclerotized tooth (Fig. 56D); basal tube (Fig.
56A, E) long, baculiform. Parameres (Fig. 56E) slender, thin; apical area short, weakly swollen
mesially, furnished mesially with 18 to 20 short setae.
Female: Eighth ventrite rounded posteriorly; gonocoxites (Fig. 56G) each serrate posteriorly,
with apicolateral tooth indistinct (or 2 or 3 teeth at apicolateral part), apicolateral setae moderately long. Spermatheca not observable.
Biology and ecology. Stenus displicatus is distributed in the low and high mountainous
regions of Kii-Peninsula (Honshu). The beetles inhabit leaf litter in the natural forests.
Remarks. Stenus displicatus is closely allied to S. toukin, but this species is separable fromthe latter by the aedeagal median lobe strongly (or abruptly) narrowed apically behind apicolateral corners to form the pentagonal apical sclerotized area (Fig. 56E) and the endophallic expulsion hook weakly arched anteriorly, with its anterolateral arm provided laterally with a small
sclerotized tooth (Fig. 56D).
Etymology. The speciﬁc epithet of this species is derived from the Latin participle “displicatus” which means “scattered”; and the setae are scattered on the anterior part of the apical sclerotized area of median lobe.
Stenus toukin Naomi & Puthz(Figs. 57A–E, 130J)
Stenus toukin Naomi & Puthz, 1994a: 216; Herman, 2001: 2419; Naomi & Puthz, 2013: 138.
Type material examined. Holotype: ♂ (CBM), Mennoki Pass, Aichi Pref., 13. viii. 1990, S.
Nomura leg. Paratype: 1 ♀ (cN), same data as holotype.
Other material examined. [HONSHU] 1 ♂, Inatake-cho, Mennoki Pass, Aichi Pref., 7. ix.
1986, T. Hozumi leg.
Distribution. Japan (Honshu: Aichi Pref.).
Redescription. Male and female: Brachypterous; body small 1.9–2.2 mm (fore body: 1.2–1.3mm) in length, subcylindrical, weakly shining, with short antennae. Head and abdomen black;pronotum and elytra dark red to almost black; labrum black; antennae dark red; legs dark red,with knees more or less infuscate. Head with a pair of longitudinal depressions; punctures round,very dense, regular, distinct. Pronotum with surface weakly uneven; punctures round, very dense.
Elytra with surface weakly uneven; punctures almost round to round, very dense. Legs short;tarsi short, with 4th tarsomere very weakly bilobed. Abdomen wide; 3rd to 5th terga each with 3
short, basi-longitudinal keels; punctures round to elliptical, dense, small and distinct in anterior
segments, while punctures in posterior segments elliptical, moderately dense, very small, regularand distinct. Lateroventrites horizontal or dorsomesial in position, narrow, punctate.
Male: Seventh ventrite (Fig. 57F) posteromedially with a relatively small, bell-shaped
depressed area, which is emarginate posteriorly; 8th ventrite (Fig. 57D) posteromedially with arelatively wide emargination, and centrally with a shallow, subovoidal depression; 9th tergum(Fig. 57A) with ventral apophyses thin, moderately long; 9th ventrite (Fig. 57B) elongate, ﬁnely
serrate posteriorly, with stem subtrapezoidal in shape, apicolateral teeth each short, bi- or triden-

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Fig. 57. Stenus toukin Naomi & Puthz (Omonoki, Aichi). A, 9th and 10th terga of male; B, 9th ventrite of male;C, aedeagus; D, 8th ventrite of male; E, 9th and 10th terga of female; F, 7th ventrite of male; G, apices ofgonocoxites. Scale 1: 0.2 mm for A–E, G; scale 2: 0.3 mm for F.

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ticulate apically, apicolateral setae short; 10th tergum (Fig. 57A) entire. Aedeagal median lobe
(Fig. 57C) wide, strongly narrowed apically behind the rounded apicolateral corners, acutely
pointed apically; apical sclerotized area almost triangular in shape, covered sparsely with setae;
apicomedian subtransparent area ovoidal in shape; apicolateral humps small, each located at thelateral margin. Endophallic median longitudinal bands (Fig. 57C) moderately long; expulsion
hook (Fig. 57C) transverse, very wide, with anterolateral arm a little longer than posterolateralarm; basal tube (Fig. 57C) long, baculiform. Parameres (Fig. 57C) slender, thin, weakly
incurved; apical area short, weakly swollen mesially, furnished mesially with 15 to 16 thin, shortsetae.
Female: Eighth ventrite rounded posteriorly; 9th tergum (Fig. 57E) without ventral apophyses; gonocoxites (Fig. 57G) each irregularly, ﬁnely serrate posteriorly, with apicolateral toothindistinct (or 2 or 3 small setae at apicolateral part); 10th tergum (Fig. 57E) entire. Spermatheca
not observable.
Biology and ecology. Stenus toukin is distributed in the mountainous regions. The beetles
inhabits leaf litter in the natural forests.
Remarks. Stenus toukin is closely allied to S. displicatus, but it is separable from the latter by
the aedeagal median lobe almost uniformly narrowed apically behind the apicolateral corners toform the triangular apical sclerotized area (Fig. 57C) and the endophallic expulsion hook almost
transverse or weakly arched posteriorly, with its anterolateral arm simple (Fig. 57C).
Etymology. The speciﬁc epithet of this species is derived from a name of ancient Chinesemask “Toukin”.
Stenus ubusuna Naomi & Ito(Figs. 58A–G, 130K)
Stenus ubusuna Naomi & Ito, 2014: 286.
Type material examined. Holotype: ♂ (KUM): Mt. Nonobori, Mie Pref., 3. xi. 1995, H.
Yokozeki leg. Paratypes: 1 ♀ (cN), same data as holotype; 1 ♂ (cN), same locality, 23. xi. 1992,
H. Yokozeki leg.
Distribution. Japan (Honshu: Mie Pref.).
Redescription. Male and female: Brachypterous; body 2.7–3.2 mm (fore body 1.5–1.6 mm) in
length, moderately shining, with antennae relatively short. Head and abdomen black; prothorax
and elytra dark red to black; labrum black; antennae and legs dark brown. Head with a pair ofbroad, longitudinal depressions; punctures round, dense, somewhat rough. Pronotum with surface weakly uneven, with median longitudinal depression indistinct; punctures round, very
dense, rough. Elytra with surface uneven; punctures very dense, rough. Legs short; tarsi short,moderately thick, with 4th tarsomere very weakly bilobed. Abdomen weakly narrowed posteriorly; 3rd to 5th terga each with 3 short, basi-longitudinal keels; punctures round to elliptical,
moderately dense, small and distinct. Lateroventrites dorsomesial or horizontal in position, narrow, punctate.
Male: Sixth ventrite posteromedially with a broad-triangular ﬂat area, which is very weakly
emarginate posteriorly; 7th ventrite (Fig. 58G) posteromedially with a bell-shaped depression,
which is arcuately emarginate posteriorly; 8th ventrite (Fig. 58G) posteromedially with amedium-sized emargination; 9th tergum (Fig. 58E) with ventral apophyses moderately long, eachweakly widened at subapical part; 9th ventrite (Fig. 58C) elongate, ﬁnely serrate posteriorly, with

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Fig. 58. Stenus ubusuna Naomi & Ito (Nonobori, Mie). A, endophallic basal tube; B, aedeagus; C, 9th ventriteof male; D, 9th, 10th terga and gonocoxites of female; E, 9th and 10th terga of male; F, expulsion hook; G,
7th to 8th ventrites of male. Scale 1: 0.2 mm for B, C, D, E, 0.1 mm for A, F; scale 2: 0.2 mm for G.

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stem transverse, apicolateral teeth each short, bi- or tridenticulate apically, apicolateral setae
short; 10th tergum almost truncate or very shallowly emarginate posteriorly (Fig. 58E). Aedeagal
median lobe (Fig. 58B) violin-shaped, bluntly pointed apically; apical sclerotized area almost
subtriangular in shape, sharply emarginate anteriorly, partly covered sparsely with short setae;
apicomedian subtransparent area elongate-ovoidal in shape; apicolateral humps medium-sized,
each located at the anterior margin of apical scleritozed area. Endophallic median longitudinalbands (Fig. 58B) with ventral bands broad, moderately long, dorsal bands rather short; expulsion
hook (Fig. 58B) thin, broad-V-shaped, with its posterolateral arm acutely pointed (Fig. 58F);
basal tube (Fig. 58A, B) large, baculiform. Parameres (Fig. 58B) slender, thin, weakly incurved;
apical area weakly swollen mesially, furnished mesially with thin setae.
Female: Eighth ventrite rounded posteriorly; 9th tergum (Fig. 58D) without ventral apophyses; gonocoxites (Fig. 58D) each ﬁnely serrate posteriorly, with apicolateral tooth short, indistinctly bi- or trifurcate apically, apicolateral setae short; 10th tergum (Fig. 58D) entire. Spermatheca not observable.
Biology and ecology. Stenus ubusuna is distributed in the low mountainous regions. The beetles inhabit leaf litter in the natural forests.
Remarks. Stenus ubusuna is allied to S. displicatus and S. toukin, but this species is separablefrom the latter two species by the aedeagal median lobe less strongly pointed apically, with apicolateral hump located at the anterior margin of apical scleritozed area (Fig. 58B), and the endophallic expulsion hook broad-V-shaped (Fig. 58F). S. ubusuna is also allied to S. kokie, but it isseparable from the latter by the median lobe with apical scleritozed area almost triangular inshape (Fig. 58B) and the endophallic expulsion hook with its median area bent posteriorly (Fig.
58F).
Etymology. The speciﬁc epithet of this species is derived from the Japanese noun ʻUbusunaʼ,
which means the guardian angel of native place.
Stenus kokie Naomi(Figs. 59A–G, 130L)
Stenus kokie Naomi, 2004c: 13.
Type material examined. Holotype: ♂ (CBM), Mt. Bunagadake, Hira, Shiga Pref., 22. vii.
1984, T. Watanabe leg.
Other material examined. [HONSHU] 1 ♂, Mt. Daihi, Kyoto Pref., 30. iv. 1987, T. Ito leg.;1 ♀, same locality, 22. vii. 1968, T. Ito leg.
Distribution. Japan (Honshu: Shiga and Kyoto Prefs.).
Redescription. Male and female: Brachypterous; body 3.6–3.7 mm (fore body 1.6–1.7 mm) in
length, moderately shining, with antennae relatively short. Head and abdomen black; prothorax
and elytra dark red to black; labrum black; antennae dark reddish brown; legs dark red, withknees more or less infuscate. Head with a pair of broad, longitudinal depressions; puncturesround to elliptical, dense to very dense, small. Pronotum with surface weakly uneven; puncturesround, very dense, sometimes subrugose. Elytra with surface uneven; punctures round to elliptical, very dense, rough. Legs short; tarsi short, with 4th tarsomere very weakly bilobed. Abdomenwide; 3rd to 6th terga each with 3 short, basi-longitudinal keels; punctures round, moderately
dense and distinct in anterior segments, while punctures in the posterior segments round to elliptical, moderately dense, very small and distinct. Lateroventrites dorsomesial or horizontal inThe Steninae of Japan Part 1

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Fig. 59. Stenus kokie Naomi (A–F, Hira, Shiga; G, Daihi, Kyoto). A, 9th and 10th terga of male; B, aedeagus; C,
endophallic basal tube; D, 9th ventrite of male; E, 7th to 8th ventrites of male; F, expulsion hook; G, apex of
gonocoxite. Scale 1: 0.2 mm for A, B, D, 0.1 mm for C, F, G; scale 2: 0.2 mm for E.

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position, narrow, punctate.
Male: Sixth ventrite posteromedially with a shallow, semicircular depression, which is
weakly emarginate; 7th ventrite (Fig. 59E) posteromedially with a bell-shaped depression, whichis arcuately emarginate; 8th ventrite (Fig. 59E) posteromedially with a V-shaped emargination,and medially with a large, shallow, elongate-ovoidal depression; 9th tergum (Fig. 59A) with ventral apophyses moderately long; 9th ventrite (Fig. 59D) elongate, ﬁnely serrate posteriorly, withstem rectangular in shape, apicolateral teeth each short, bi- or tridenticulate apically, apicolateral
setae short; 10th tergum (Fig. 59A) entire. Aedeagal median lobe (Fig. 59B) violin-shaped, withapex narrow but still rounded; apical sclerotized area anteriorly with V-shaped emargination,
covered sparsely with setae of various length along the rim of emargination; apicomedian subtransparent area elongate-elliptical in shape; apicolateral humps medium-sized, each located at
the anterior margin of lateral rim. Endophallic median longitudinal bands (Fig. 59B) with ventral
bands long, dorsal bands moderately long, relatively wide; expulsion hook (Fig. 59B) transverse,
thin, with anterolateral arm and postero-lateral arm short, laterally with a small sclerotized hump
(Fig. 59F); basal tube (Fig. 59B, C) large, baculiform. Parameres (Fig. 59B) weakly incurved;
apical area moderately long, very weakly swollen mesially, and furnished mesially with 16 to 17
thin setae.
Female: Eighth ventrite rounded posteriorly; gonocoxites (Fig. 59G) each distinctly serrate
posteriorly, with apicolateral teeth moderately long, bi- or trifurcate apically, apicolateral setae
moderately long. Spermatheca not observable.
Biology and ecology. Stenus kokie is distributed in the low mountainous regions. The beetles
inhabit leaf litter in the natural forests.
Remarks. Stenus kokie is allied to S. ubusuna, but it is separable from the latter by the aedeagal median lobe with apical sclerotized area longer, narrower and a little more rounded apically(Fig. 59B), and the exdophallic expulsion hook simply transverse (Fig.59F).
Etymology. The speciﬁc epithet of this species “kokie” is derived from the Japanese name of
the three small stars located at the eastern side of Aries.
Stenus serratimarginatus Naomi(Figs. 60A–G, 131A)
Stenus serratimarginatus Naomi, 1997f: 139; Herman, 2001: 2387; Naomi & Puthz, 2013: 138.
Stenus zimmermanni Puthz, 1968b: Naomi & Takeda, 1991: 10.
Type material examined. Holotype: ♂ (CBM), Fudago, Kimitsu City, Chiba Pref., 20. iv.
1989, S. Naomi leg. Paratypes: 4 ♂ (cN), Fudago, Kimitsu City, Chiba Pref., 20. iv. 1989, S.
Naomi leg.; 2 ♂2 ♀ (cN), Mt. Kiyosumi, Amatsu-kominato, Chiba Pref., 9. vi. 1991, T. Takeda
leg.; 1 ♀ (cN), Uchiurayama, Amatsu-kominato, Chiba Pref., 12. v. 1991, T. Takeda leg.; 1 ♂2 ♀
(cN), Yomogi, Mt. Kiyosumi, Amatsu-kominato, Chiba Pref., 27. v. 1990, T. Takeda leg.; 1 ♀
(cN), same locality, 4. iv. 1990, T. Takeda leg.; 1 ♂ (cN), Yoro Valley, Ichihara City, Chiba Pref.,20. v. 1990, T. Takeda leg.; 1 ♂ (cN), Mt. Daifuku, Ichihara City, Chiba Pref., 29. vi. 1991, T.
Takeda leg.; 1 ♂2 ♀ (cN), Chikura-cho, Chiba Pref., 26. vi. 1994, S. Naomi leg.
Distribution. Japan (Honshu: Chiba Pref.).
Redescription. Male and female: Brachypterous; body 2.7–3.6 mm (fore body 1.5–1.6 mm) in
length, weakly to moderately shining, with antennae short. Head and abdomen black; pronotumand elytra dark red to black; labrum black; antennae dark red; legs dark red, with knees more or

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Fig. 60. Stenus serratimarginatus Naomi (A, B, D–F, Kimitsu, Chiba; C, G, Kiyosumi, Amatsu-kominato). A,
aedeagus; B, 9th ventrite of male; C, 6th to 8th ventrites of male; D, endophallic expulsion hook; E, 9th and10th terga of male; F, basal tube; G, apex of gonocoxite. Scale 1: 0.1 mm for A, B; scale 2: 0.3 mm for C;
scale 3: 0.2 mm for E, 0.1 mm for D, G, F.

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less infuscate. Head with a pair of longitudinal depressions; punctures round, dense to very
dense, small. Pronotum with surface weakly uneven; punctures round, very dense, somewhat
rough. Elytra with surface uneven; punctures round to elliptical, very dense, various in size,
rough. Legs short; tarsi with 4th tarsomere very weakly bilobed. Abdomen wide; 3rd to 5th or
6th terga each with 3 short, basi-longitudinal keels; punctures round to elliptical, moderately
dense and small in anterior segments, while punctures in posterior segments elliptical, dense,
very small and regular. Lateroventrites horizontal or dorsomesial in position, narrow, punctate.
Male: Sixth ventrite (Fig. 60C) posteromedially with a semicircular ﬂat area, which is very
shallowly emarginate, and also furnished with moderately long setae along the posterior margin;
7th ventrite (Fig. 60C) posteromedially with a bell-shaped depression, which is arcuately emarginate, and covered densely with thin, short setae; 8th ventrite (Fig. 60C) posteromedially with amedium-sized emargination, and medially with an elongate depression which becomes shallower
posteriorly; 9th tergum (Fig. 60E) with ventral apophyses moderately long; 9th ventrite (Fig.
60B) elongate, moderately serrate posteriorly, with stem rectangular in shape, apicolateral teeth
each short, weakly incurved, bidenticulate apically, apicolateral setae short; 10th tergum (Fig.
60E) entire. Aedeagal median lobe (Fig. 60A) violin-shaped, bluntly angulate apically; apicalsclerotized area distinctly incised anteriorly, covered anteromedially with sparse, short setae; apicomedian subtransparent area large, subovoidal in shape; anterolateral humps large, each locatedat the mesial margin of lateral rim (Fig. 60A). Endophallic median longitudinal bands (Fig. 60A)
moderately long, wide; expulsion hook (Fig. 60A) transverse, arc-shaped, anterolateral arm basimesially with a small sclerotized hump (Fig. 60D); basal tube (Fig. 60A, F) large, baculiform.
Parameres (Fig. 60A) slender, weakly incurved; apical area short, weakly swollen mesially, covered mesially with 18 to 19 thin, short setae.
Female: Eighth ventrite rounded posteriorly; gonocoxites (Fig. 60G) each serrate posteriorly,
with apicolateral tooth bifurcate apically, apicolateral setae moderately long. Spermatheca notobservable.
Biology and ecology. Stenus serratimarginatus is presently indigenous to the southern part ofBoso-Peninsula, Chiba. This species is distributed in the plains and low mountainous regions
there. The beetles inhabit leaf litter in the natural forests, and also moist litter heaped near themountain streams.
Remarks. Naomi & Takeda (1991) ﬁrst recorded Stenus serratimarginatus as S. zimmermanni
from Boso-Peninsula. Naomi (1997f) later regarded and described those local populations as a
new species independently from S. zimmermanni. S. serratimarginatus is closely allied to S. zimmermanni, but it is separable from the latter by the 6th ventrite of male with posteromedian ﬂatarea (Fig. 60C), the aedeagal median lobe with apical sclerotized area blunt apically, and covered
anteromedially with sparse, short setae (Fig. 60A), and the endophallic expulsion hook withanterolateral arm shorter, basimesially with a small sclerotized hump (Fig. 60D).
Stenus zimmermanni Puthz(Figs. 61A–E, 131B)
Stenus zimmermanni Puthz, 1968b: 43; Herman, 2001: 2439; Naomi & Puthz, 2013: 138.
Stenus sakura Hromádka, 1979a (partim).
Type material examined. Holotype: ♀ (MHNG), Mt. Takao, Hachioji, Tokyo, 8. iv. 1966, G.
Zimmermann leg. [examined by Puthz]. Paratype of S. sakura: 1 ♀ (cP), Chuzenji, Nikko,

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Tochigi Pref., 13. xi. 1953, K. Sawada leg.
Other material examined. [HONSHU] 1 ♂, Kirizumi Spa, Matsueda-cho, Gunma Pref., 22.
vii. 1990, T. Kishimoto leg.; 1 ♂1 ♀, same locality, 25. v. 1962, Y. Shibata leg.; 1 ♂2 ♀, Mt. Jyomine, Yoshida-cho, Saitama Pref., 12. ix. 1999, S. Arai leg.; 2 ♂, Mt. Ryogami, Ryogami-mura,
Saitama Pref., 10. v. 1997, M. Maruyama leg.; 1 ♂, same locality, 31. x. 1999, T. Shimada leg.;1 ♂, Mt. Takao, Tokyo, 6. vii. 1985, M. Tao leg.; 1 ♀, same locality, 10. x. 1992, S. Hashimoto
leg.; 1 ♀, same locality, 14. v. 1977, M. Tao leg.; 2 ♂, Umenoki-daira, Hachioji City, Tokyo, 17.
iv. 1996, M. Maruyama leg.; 1 ♂, Mt. Mitake, Tokyo, 6. v. 1962, Y. Shibata leg.; 1 ♂, Near
Atsugi, Kanagawa Pref., 7. iv. 1960, Y. Shibata leg.; 1 ♂, Uchinokaya, Ina, Nagano Pref., 13. viii.
1999, Y. Hayashi leg.; 1 ♂, Mt. Amagi, Izu Pen., Shizuoka Pref., Y. Watanabe leg.
Distribution. Japan (Honshu).
Redescription. Male and female: Brachypterous; body 3.5–3.7 mm (fore body 1.6–1.7 mm) in
length, weakly to moderately shining, with antennae short. Head and abdomen black; pronotumand elytra dark red; labrum black; antennae dark red; legs dark red, with knees more or lessinfuscate. Head with a pair of longitudinal depressions; punctures round, dense, almost regular.
Pronotum with surface uneven; punctures round, very dense, somewhat rough. Elytra with surface uneven; punctures round, very dense, rough. Legs short; tarsi with 4th tarsomere very
weakly bilobed. Abdomen wide, weakly convex above; 3rd to 5th terga each with 3 short, basilongitudinal keels; punctures round to elliptical, moderately dense, small and distinct in anterior
segments, while punctures in posterior segments elliptical, moderately dense, very small and regular. Lateroventrites almost horizontal or dorsomesial in position, narrow, punctate.
Male: Seventh ventrite (Fig. 61G) posteromedially with a semicircular depression, which isarcuately emarginate; 8th ventrite (Fig. 61G) posteromedially with a relatively wide emargination, and medially with an elongate depression which becomes shallower posteriorly; 9th tergum(Fig. 61B) with ventral apophyses long; 9th ventrite (Fig. 61C) elongate, hardly serrate posteriorly, with stem subtrapezoidal in shape, apicolateral teeth each short, di- or trifurcate apically;
10th tergum (Fig. 61B) very shallowly emarginate. Aedeagal median lobe (Fig. 61A) violinshaped, acutely pointed apically; apical sclerotized area subtriangular in shape, anterolaterallywith a pair of setose areas; apicomedian subtransparent area elongate-elliptical in shape; anterolateral humps medium-sized, each located at the mesial margin of lateral rim. Endophallic
median longitudinal bands (Fig. 61A) long; expulsion hook (Fig. 61A) transverse, arc-shaped,with anterolateral arm distinctly longer than posterolateral arm (Fig. 61F); basal tube (Fig. 61A,
D) large, baculiform. Parameres (Fig. 61A) slender, thin; apical area weakly swollen mesially,
covered mesially with 18 to 19 thin, short setae.
Female: Eighth ventrite rounded posteriorly; gonocoxites (Fig. 61E) each serrate posteriorly,
with apicolateral teeth each distinctly bi- or trifurcate apically. Spermatheca not observable.
Biology and ecology. Stenus zimmermanni is distributed in the plains and mountainous
regions. The beetles inhabit leaf litter in the natural forests.
Remarks. Stenus zimmermanni is closely allied to S. serratimarginatus, but it is separablefrom the latter by the 6th ventrite of male without modiﬁcation, the aedeagal median lobe withapical sclerotized area acutely pointe apically, and anterolaterally with a pair of setose areas (Fig.
61A), and the endophallic expulsion hook with anterolateral arm longer and simple (Fig. 61F).
Etymology. This species was named in honour of Mr. Gustav Zimmermann, a member of the
Berlin Philharmonic Orchestra, who collected the holotype of this species.

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Fig. 61. Stenus zimmermanni Puthz (A, B, D–F, Takao, Tokyo; C, G, Hachioji, Tokyo). A, aedeagus; B, 9th and10th terga of male; C, 9th ventrite of male; D, endophallic basal tube; E, apex of gonocoxite; F, expulsion
hook; G, 7th to 8th ventrites of male. Scale 1: 0.2 mm for A–C, 0.1 mm for D–F; scale 2: 0.3 mm for G.

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Stenus yasutoshii Naomi(Figs. 62A–G, 131C)
Stenus yasutoshii Naomi, 1997f: 137; Herman, 2001: 2438; Naomi & Puthz, 2013: 138.
Type material examined. Holotype: ♂ (CBM), Near Akazawa-Spa, Masuho, Yamanashi
Pref., 4. v. 1974, Y. Shibata leg. Paratypes: 2 ♀ (cN), same data as holotype.
Distribution. Japan (Honshu: Yamanashi Pref.).
Redescription. Male and female: Brachypterous; body 3.2–3.6 mm (fore body 1.5–1.7 mm) in
length, weakly to moderately shining, with antennae relatively short. Head and abdomen black;pronotum and elytra dark red; labrum black; antennae dark red; legs dark red, with knees more orless infuscate. Head with a pair of longitudinal depressions; punctures round, dense, almost regular. Pronotum with surface uneven; punctures round, very dense, somewhat rough. Elytra withsurface uneven; punctures round, very dense, rough. Legs short; tarsi with 4th tarsomere very
weakly bilobed. Abdomen wide, weakly convex above; 3rd to 5th terga each with 3 short, basilongitudinal keels; punctures round to elliptical, moderately dense, and distinct in anterior segments, while punctures in posterior segments elliptical, moderately dense, very small and regular.
Lateroventrites almost horizontal in position, narrow, punctate.
Male: Sixth ventrite posteromedially with a very shallow emargination; 7th ventrite (Fig.
62G) posteromedially with a semicircular depression, which is arcuately emarginate; 8th ventrite(Fig. 62E) posteromedially with a small emargination, and centrally with an elongate-ovoidal
depression which becomes shallower posteriorly; 9th tergum (Fig. 62A) with ventral apophyses
moderately long; 9th ventrite (Fig. 62B) elongate, irregularly serrate posteriorly, with stem elongate-subrectangular in shape, apicolateral teeth each short, bi- or tridenticulate apically; 10th tergum (Fig. 62A) entire. Aedeagal median lobe (Fig. 62B) violin-shaped, distinctly angulate apicolaterally, then almost abruptly constricted to form the apical sclerotized area which is ﬂat
ventrally, rounded apically and covered sparsely with short setae; apicomedian subtransparent
area ovoidal in shape; anterolateral humps small, each located at the anterolateral corners of apical sclerotized area. Endophallic median longitudinal bands (Fig. 62C) very long, broad at base,gradually divergent anteriorly; expulsion hook (Fig. 62C) arc-shaped, with anterolateral arm
shortly incurved apically; basal tube (Fig. 62C) large, baculiform. Parameres (Fig. 62B) slender,
thin, very weakly incurved; apical area weakly swollen mesially, furnished mesially with 18 to
19 thin, (mostly) short setae.
Female: Eighth ventrite rounded posteriorly; 9th tergum (Fig. 62D) without ventral apophyses; gonocoxites (Fig. 62F) each irregularly serrate posteriorly, with apicolateral teeth each bi- or
trifurcate apically, apicolateral setae short; 10th tergum (Fig. 62D) entire. Spermatheca notobservable.
Biology and ecology. Stenus yasutoshii is distributed in the mountainous regions. The beetles
inhabit leaf litter in the natural forests.
Remarks. Stenus yasutoshii is closely allied to S. hououmontis, but it is separable from thelatter by the aedeagal median lobe with apical sclerotized area rounded apically (Fig. 62C) andthe endophallic expulsion hook with anterolateral arm shortly incurved (Fig. 62C).
Etymology. This species was named in honour of an eminent staphylinist, Mr. Yasutoshi Shibata (Tokyo) who collected the type material of this species.

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Fig. 62. Stenus yasutoshii Naomi (Masuho, Yamanashi). A, 9th and 10th terga of male; B, 9th ventrite of male;C, aedeagus; D, 9th and 10th terga of female; E, 8th ventrite of male; F, apices of gonocoxites; G, 7th ventriteof male. Scale 1: 0.2 mm for A–D, F; scale 2: 0.2 mm for E; scale 3: 0.3 mm for G.

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Stenus houomontis Naomi & Ito(Figs. 63A–E, 131D)
Stenus houomontis Naomi & Ito, 2014: 283.
Type material examined. Holotype: ♂ (OMNH), Mt. Houo, Yamanashi Pref., 22. viii. 1989,
K. Hosoda leg. Paratypes: 2 ♂3 ♀, same data as holotype; 1 ♂, Maruno-cho, Yamanashi Pref., 19.
vi. 1992, K. Hosoda leg.; 2 ♂ (cN), Sessokyo, Honkawane-cho, Shizuoka Pref., 9-10. v. 1982, T.
Kishimoto leg.
Distribution. Japan (Honshu: Yamanashi and Shizuoka Prefs.).
Redescription. Male and female: Brachypterous; body 2.8–3.0 mm (fore body 1.5–1.6 mm) in
length, dull to moderately shining, with antennae relatively short. Body entirely dark red toblack; labrum black; antennae and legs dark red to dark brown. Head with a pair of broad, longitudinal depressions; punctures round, dense to very dense. Pronotum somewhat ﬂat on medianarea, with surface uneven; punctures round, very dense, distinct. Elytra with surface uneven;punctures very dense, rough. Legs short; tarsi short, moderately thick, with 4th tarsomere very
weakly bilobed. Abdomen weakly narrowed posteriorly; 3rd to 6th terga each with 3 short, basilongitudinal keels; punctures small, moderately dense and distinct in anterior segments, while
punctures in posterior segments round to elliptical, very small and shallow. Lateroventrites horizontal or dorsomesial in position, narrow, punctate.
Male: Sixth ventrite posteromedially with a triangular ﬂat area, which is very weakly emarginate; 7th ventrite (Fig. 63E) posteromedially with a semicircular depressed area, which is arcuately emarginate; 8th ventrite (Fig. 63E) posteromedially with a small emargination; 9th tergum(Fig. 63A) with ventral apophyses long, thin; 9th ventrite (Fig. 63C) elongate, very ﬁnely serrate
posteriorly, with stem subtrapezoidal in shape, apicolateral teeth each very short, bi- or tridenticulate apically; 10th tergum (Fig. 63A) entire. Aedeagal median lobe (Fig. 63B) violin-shaped,
widely rounded apicolaterally, and then strongly constricted behind the apicolateral corners toform a lanceolate apical sclerotized area which is acutely pointed apically, and covered sparselywith short setae; apicomedian subtransparent area elongate-ovoidal in shape; anterolateral humps
small, each located at the mesial margin of lateral rim. Endophallic median longitudinal bands
moderately long; expulsion hook (Fig. 63B) transverse, thin, with anterolateral arm a little longer
than posterolateral arm; basal tube (Fig. 63B) large, almost baculiform. Parameres (Fig. 63B)
slender, thin, weakly incurved; apical area weakly swollen mesially, furnished mesially with thin,short setae.
Female: Eighth ventrite rounded posteriorly; 9th tergum (Fig. 63D) without ventral apophyses; gonocoxites (Fig. 63D) each irregularly serrate posteriorly, with apicolateral tooth indistinct(or one or two small teeth at apicolateral part); 10th tergum (Fig. 63D) entire. Spermatheca notobservable.
Biology and ecology. Stenus houomontis is distributed in the mountainous regions up toalpine zones (about 3000 m) in central Honshu. The beetles inhabit leaf litter in the natural forests.
Remarks. Stenus houomontis is allied to S. yasutoshii, but it is separable from the latter by
the aedeagal median lobe with apical sclerotized area lanceolate (Fig. 63B), and the endophallic
expulsion hook with anterolateral arm simply turning anterolaterally (Fig. 63B). S. houomontis isalso allied to S. takashii, but it is separable from the latter by the aedeagal median lobe strongly
constricted behind apicolateral corners to form the lanceolate apical sclerotized area (Fig. 63B),

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Fig. 63. Stenus houomontis Naomi & Ito (Houo, Yamanashi). A, 9th and 10th terga of male; B, aedeagus; C, 9th
ventrite of male; D, 9th, 10th terga and gonocoxites of female; E, 7th to 8th ventrites of male. Scale 1: 0.2 mm
for A–D; scale 2: 0.2 mm for E.

the expulsion hook distinctly thinner (Fig. 63B); and the apicomedian subtransparental area without lateral teeth.

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Stenus takashii Naomi(Fig. 64A–D)
Stenus takashii Naomi, 2004c: 15; Naomi & Puthz, 2013: 138.
Type material examined. Holotype: ♂ (CBM), Yoshizawa, Sakuma, Shizuoka Pref., 30. iv.
1994, T. Watanabe leg.
Distribution. Japan (Honshu: Shizuoka Pref.).
Redescription. Male: Brachypterous; body 3.3 mm (fore body 1.6 mm) in length, moderately
shining, with antennae relatively short. Head and abdomen black; pronotum and elytra dark red
to black; labrum black; antennae and legs dark red. Head with a pair of longitudinal depression;
punctures round, dense to very dense, various in size, distinct. Pronotum with surface weakly
uneven; punctures round, very dense, somewhat rough. Elytra with surface uneven, each with ashallow longitudinal depression near humeral area; punctures round to elliptical, very dense,
large. Legs relatively short; tarsi with 4th tarsomere very weakly bilobed. Abdomen wide; 3rd to
5th terga each with 3 short, basi-longitudinal keels; punctures round to elliptical, moderately
dense, small and distinct in anterior segments, while punctures in the posterior segments elliptical, very small, regular and distinct. Lateroventrites horizontal in position, narrow, punctate.
Seventh ventrite (Fig. 64C) posteromedially with a bell-shaped depression, which is arcuately emarginate; 8th ventrite (Fig. 64C) posteromedially with a V-shaped emargination; 9th tergum (Fig. 64B) with ventral apophyses thin, long; 9th ventrite (Fig. 64D) elongate, ﬁnely serrate
posteriorly, with stem subquadrangular, arcuately emarginate anteriorly, posterolateral teeth each
short, bifurcate apically. Aedeagal median lobe (Fig. 64A) nearly gourd-shaped, with lateral rim
wide, apicomedian projection relatively long; apical sclerotized area anteromedially covered
with sparse, short setae; apicomedian subtransparent area large, elongate-elliptical in shape, witha pair of pointed teeth near the middle of the lateral sides of subtransparent area; apicolateral
humps very large, low, sclerotized, rounded, and each located at the mesial margin of wide lateral rim. Endophallic median longitudinal bands (Fig. 64A) very long, gradually diverging anteriorly; lateral longitudinal bands distinct, short (Fig. 64A); expulsion hook (Fig. 64A) transverse,very thick, stout, with anterolateral arm short, pointed, and a little shorter than posterolateralarm; basal tube (Fig. 64A) large, baculiform. Parameres (Fig. 64A) slender, thin, very weakly
incurved; apical area moderately long, weakly swollen mesially, furnished mesially with 20 to
21, thin, short setae.
Female. Unknown.
Biology and Ecology. Only one male of Stenus takashii was presently collected in the low
mountainous region of Central Honshu (Chubu). The beetle inhabits leaf litter in the natural forest there.
Remarks. Among the Japanese members of S. humilis group, Stenus takashii is unique inhaving the following apomorphic characters of aedeagus (Fig. 64A): the median lobe has its
broadly expanded lateral rims, with the acutely pointed apicomedian projection; a pair of pointed
teeth exist at the middle of the lateral sides of apicomedian subtransparent area; and the endophallic expulsion hook is very thick and stout. However, given structural similarities on the modiﬁcations of 7th and 8th ventrites of male, the ventral apophyses of 9th tergum of male, etc., S.
takashii is probably most closely allied to S. houomontis. S. takashii is easily separable from S.
houomontis and also other Japanese members of this species group by the unique characters
mentioned above.

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Fig. 64. Stenus takashii Naomi (Sakuma, Shizuoka). A, aedeagus; B, 9th and 10th terga of male; C, 7th to 8th
ventrites of male; D, 9th ventrite of male. Scale 1: 0.1 mm for A; scale 2: 0.2 mm for B, D; scale 3: 0.2 mm forC.

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Etymology. This species is named in honour of Mr. Takashi Watanabe, Kanagawa, who collected the holotype of this species.
Species group of S. circularis (Gravenhorst)
S. circularis group (＝S. rugicollis group; ＝S. cameratus group; Puthz, 2011a: 816) consistsof 1 species (S. sexualis) in Japan (Puthz, 1968b); see Puthz (2003a: 59–61) regarding a key tospecies of this group, and see Puthz (1988a: 634) regarding a characterization of this group.
Diagnostic characters are as follows: Legs with 4th tarsomere simple; 3rd to 6th (or 7th) tergaeach with 3 basi-longitudinal keels; lateroventrites ventromesial in position, broad; 9th ventriteof male broad basally, glabrous but with apicolateral teeth and paired macrosetae (Fig. 65F); 10th
tergum rather elongate (Fig. 65B, C), with setaceous spot (Puthz, 1988a: 634); aedeagal median
lobe often with rather slender apical portion (Fig. 65A; Puthz, 2003a, ﬁgs. 4, 7, 9, 13); gonocoxite widely rounded apicomesially (Fig. 65E); spermatheca not observable.
Stenus sexualis Sharp(Figs. 65A–F, 131E)
Stenus sexualis Sharp, 1874: 84; Herman, 2001: 2387; Naomi & Puthz, 2013: 138; Naomi &Watanabe, 2015: 108.
Type material examined. Syntypes: (NHML, FMCh), type localities: Sapporo (Hokkaido),
Miyanoshita (Kanagawa) [examined by Puthz in 1965].
Other material examined. [HOKKAIDO]: 1 ♀, Haboro-cho, 24. vii. 1998, K. Haga leg.
[HONSHU]: 1 ♂, Shiobara, Tochigi Pref., 17. iv. 1988, S. Ohmomo leg.; 1 ♀, Suidobashi,
Shonan-cho, Chiba Pref., 13. iii. 1990, T. Takeda leg.; 1 ♂, Tanida, Shirai-cho, Chiba Pref., 14. ii.
1989, T. Takeda leg.; 1 ♀, Mt. Daifuku, Ichihara C., Chiba Pref., 27. vi. 1991, T. Takeda leg.; 3exs., Kanagawa Pref.; 1 ♀, Komanoyu, Niigata Pref., 4. vii. 1963, Y. Watanabe leg.; 1 ♂1 ♀,Uono River, Kawaguchi-cho, Niigata Pref., 30. iv. 1995, K. Haga leg.; 3 ♂5 ♀, Okayama, Sauter;1 ♀, Bukenji, Kanagawa?, Sauter; 1 ♀, Hichitukabara, Shobara C., Hiroshima Pref., 14. viii.
1974, I. Okamoto leg. [KYUSHU]: 1 ♀, Mt. Sobo, Ohita Pref., 15. vii. 1960, K. Mizusawa leg.
Distribution. Japan (Hokkaido, Honshu, Kyushu); China, Laos.
Redescription. Male and female: Macropterous; body 2.3–2.6 mm (fore body 1.4–1.6 mm) in
length, surface strongly shining with interstices between punctures on body lustrous and smooth,antennae short, elytra large, gently convex. Head and abdomen black; pronotum and elytra dark
reddish brown; labrum black; antennae dark red; legs yellowish brown to reddish brown. Headwith a pair of distinct longitudinal depressions which are convergent anteriorly, median vertexal
area between the depressions rather narrow, elongate-triangular; punctures round to elliptical,very dense. Pronotum with surface weakly uneven, often with an indistinct small fovea on the
median area before posterior margin; punctures round to elliptical, very dense, sometimes two or
more punctures partially fused. Elytra with surface almost even; punctures round, very dense,
distinct. Legs moderate in length; tarsi moderate in length, 4th tarsomere simple. Abdomen distinctly narrowed posteriorly (Fig. 131E), covered sparsely with short, thin setae; 3rd to 6th or 7th
terga each with 3 basi-longitudinal keels, median keel larger, longer than lateral ones in each segment, median keel on 3rd tergum rather large, almost triangular; punctures basically rather sparseand small on all terga, but punctures on 7th tergum a little larger than those on anterior segments.

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Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

Fig. 65. Stenus sexualis Sharp (A, D, Tanida, Chiba; B, F, Uono, Niigata; C, E, Daifuku, Chiba). A, aedeagus; B,
9th and 10th terga of male; C, 9th and 10th terga of female; D, 7th to 8th ventrites of male; E, gonocoxite; F,
9th ventrite of male. Scale 1: 0.1 mm for A–C, E, F; scale 2: 0.2 mm for D.

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Lateroventrites ventromesial in position, broad, distinct, punctate.
Male: Seventh ventrite (Fig. 65D) posteromedially with a very shallow emargination; 8thventrite (Fig. 65D) posteromedeally with a subtriangular emargination; 9th tergum (Fig. 65B)
with ventral apophyses long, spatulate; 9th ventrite (Fig. 65F) rather wide basally, strongly narrowed apically, with stem subtriangular in shape, apicolateral teeth stout, sclerotized, moderately
long, surface glabrous but with macrosetae and apicolateral setae moderately long; 10th tergum(Fig. 65B) elongate, subtriangular in shape, rounded apically. Aedeagal median lobe (Fig. 65A)
broad and elongate-elliptical in anterior 2/3, thin and rod-like lobe in posterior 1/3, with a pair ofelongate anterolateral impressions, and the apicomedian projection. Endophallic median longitudinal bands (Fig. 65A) very thin, with ventral bands moderately long, dorsal bands short; laterallongitudinal bands (Fig. 65A) very short; expulsion hooks (Fig. 65A) fused to form an arrowshaped sclerite; apicolateral sclerites (Fig. 65A) widely separated, each very small, triangular inshape; basal tube (Fig. 65A) very long, with basal room partly submembranous, distinctly demarcated from tube body by membranous area, the tube body distinctly divided by a membranousarea into the anterior thick rod and the posterior sinuous and attenuate rod. Parameres (Fig. 65A)
thin, straight; apical area long, furnished mesially with 14 to 15 short setae.
Female: Eighth ventrite rounded posteriorly; gonocoxites (Fig. 65E) each widely roundedapicomesially, narrowed and incurved apically, with apicolateral tooth elongate, bidenticulate
apically, apicolateral setae moderately long. Spermatheca not observable.
Biology and Ecology. S. sexualis is a rare Stenus species in Japan; and it is distributed in theplains and low mountainous regions. The beetles inhabit leaf litter in or near the natural forests or
shrubs.
Remarks. Stenus sexualis is allied to S. calcarifer Puthz, 1991a, but this species is separablefrom the latter by the elytra with punctures less dense, distinct and regular, the abdomen with
punctures ﬁner, and the aedeagal median lobe much thinner in apical 1/3 (Fig. 65A). This species
is here ﬁrst recorded from Kyushu.
Species group of S. javanus Cameron
S. javanus group consists of 1 species in Japan (Puthz, 1973a); see Puthz (1980b, 2009b)
regarding a taxonomy of this group. Diagnostic characters are as follows: Head about as wide as
elytra (Fig. 131F); legs with 4th tarsomere simple; lateroventrites ventromesial in position, moderately broad; 9th ventrite of male very sparsely setous, with paired macrosetae and acute apicolateral teeth (Fig. 66E); 10th tergum transverse (Fig. 66C); aedeagal median lobe with ﬂagellum
very long, parameres large, characteristically sinuous medially (Fig. 66A); endophallic expulsion
hooks separated (Fig. 66A); gonocoxite with acute apicolateral tooth (Fig. 66F); spermatheca
being of guttalis form (Figs. 7B, 66B).
Stenus riukiuensis Puthz(Figs. 66A–F, 131F)
Stenus riukiuensis Puthz, 1973a: 6; Herman, 2001: 2369; Naomi & Puthz, 2013: 138; Puthz,
2012b: 91; Puthz, 2013: 1296.
Type material examined. Holotype: ♀ (NMNHW), type locality: Amami-Oshima (Nansei
Isls.) [examined by Puthz].

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Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

Fig. 66. Stenus riukiuensis Puthz (A, C, D, E, Hatsuno, Amami Is.; B, F, Yona, Okinawa Is.). A, aedeagus; B,
spermatheca; C, 9th and 10th terga of male; D, 6th to 8th ventrites of male; E, 9th ventrite of male; F, , apexof gonocoxite. Scale 1: 0.1 mm for A, C; scale 2: 0.1 mm for B, F, 0.2 mm for E; scale 3: 0.2 mm for D.

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Other material examined. [NANSEI ISLS.]: 3 ♂, Hatsuno, Amami Is., Kagoshima Pref., 27.
iii. 1978, S. Naomi leg.; 1 ♂, Yona, Okinawa Is., Okinawa Pref., 13. iii. 1985, S. Nomura leg.;1 ♀, Yona, Kunigami-son, Okinawa Is., Okinawa Pref., 6. v. 1991, T. Ueno leg. [TAIWAN]: 1 ♂
(cS), Taiwan, Kaohsiung Hsien, Tengchih, 1610 m, 24. iv. 1990, A. Smetana leg.; 1 ♂1 ♀ (cS),
Taiwan, Taitung Hsien, Hsinkangshan above Chengkang, 750 m, 18. iv. 1998, A. Smetana leg.
Distribution. Japan (Nansei Isls.: Amami Is., Okinawa Is.); Taiwan, Malaysia, Laos.
Redescription. Male and female: Macropterous; body 2.5–2.7 mm (fore body 1.4–1.5 mm) in
length, somewhat robust, moderately shining, with short antennae and relatively long legs. Headblack; pronotum and elytra dark reddish brown, lustrous; abdomen black but apical segments
dark red; labrum black; antennae and legs almost clear yellowish brown to reddish brown. Headwide, with a pair of longitudinal depressions, median vertexal area between the depressions
rather narrow; punctures round to elliptical, very dense, various in size, distinct. Pronotum withsurface weakly uneven, often with an indistinct small fovea on the median area before posterior
margin; punctures round, very dense, various in size. Elytra with surface weakly uneven; punctures round to almost round, very dense, various in size. Legs with tarsi relatively long, 4th tarsomere simple. Abdomen distinctly narrowed posteriorly (Fig. 131F); terga without basi-longitudinal keels; punctures round to elliptical, moderately dense, various in size, and distinct in anterior
segments, while punctures in posterior segments elongate-ovoidal to elliptical, large, distinct, andalmost regularly arranged longitudinally. Lateroventrites ventromesial in position, distinct, andset with some moderately large punctures.
Male: Sixth ventrite (Fig. 66D) posteromedially with a semicircular ﬂat area; 7th ventrite(Fig. 66D) posteromedially with a large, moderately deep concavity, which is broadly emarginate
posteriorly and strongly ridged laterally, with its posterolateral part weakly projecting posteriorly
beyond the posterior margin of segment; 8th ventrite (Fig. 66D) broadly emarginate posteriorly,
apicolaterally with triangular pointed projection; 9th tergum (Fig. 66C) with ventral apophyses
large, each mesially with the ﬂap which is rather wide basally; 9th ventrite (Fig. 66E) widelyrounded anterolaterally, hardly serrate posteriorly, with the median thread-like, sclerotized area
running longitudinally, apicolateral teeth pointed, surface very sparsely setous, with macrosetae
paired, apicolateral setae short; 10th tergum (Fig. 66C) subtrapezoidal in shape. Aedeagal median
lobe (Fig. 66A) nearly fusiform, rounded apicolaterally, with a short apicomedian projection, apical sclerotized area well-developed. Endophallic median longitudinal bands (Fig. 66A) thin,short, divergent anteriorly; expulsion hooks (Fig. 66A) widely separated but connected by a narrow thread (Puthz, 2012, ﬁg. 12), each elongate, rounded posteriorly; ﬂagellum (Fig. 66A) very
long and thin, and in situ being out from the apical foramen except for its basal portion, basal
room crescent in shape. Parameres (Fig. 66A) very large, much extending posteriorly beyond theapex of median lobe, and uniquely sinuous medially, each furnished mesially with setae of various length behind the middle of paramere.
Female: Eighth ventrite distinctly angulate posteromedially; gonocoxites (Fig. 66F) eachvery ﬁnely serrate posteriorly, with apicolateral tooth acute. Spermatheca (Fig. 66B) thin, with 4
distinct turns, capsule and basal valve missing; RT-duct comprising the almost long, apical ductbut extending a little proximally beyond the 4th turn; spermathecal duct swollen at the anterior
part of duct between 2nd and 3rd turns, and also strongly bent at the 3rd turn, where a small,
ovoidal spermathecal gland opens and turns just anteriorly.
Biology and Ecology. Stenus riukiuensis is distributed in the plains and low mountainous
regions in Nansei Isls. The beetles inhabit leaf litter in or near the natural forests.
Remarks. Stenus riukiuensis is closely allied to S. sannio Puthz, 1980a from India and Nepal

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Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz(see also Puthz, 2012b), but this species is separable from the latter by the 8th ventrite of maleposteriorly with a simple, wide emargination (Fig. 66D), and the aedeagal median lobe narroweraround the apicolateral corner (Fig. 66D). S. riukiuensis is also allied to S. spongifera Cameron,1929 from Malaysia and Sumatra, but the punctures are basically ﬁner on body, and the lateroventrites are set with some moderately large punctures (Puthz, 1973a).
Species group of S. palposus Zetterstedt
S. palposus group consists of 1 species in Japan; see Puthz (1988b) regarding a characterization of, and a key to the Nearctic species of, this group; and see Puthz (1970) regarding a key to
the Palaearctic species of this group. Diagnostic characters are as follows: Body covered with silvery pubescence (Fig. 131G); maxillary palpi entirely black; legs with 4th tarsomeres simple;
abdomen with 4 short basi-longitudinal keels in each of 3rd to 6th terga; lateroventrites ventromesial to horizontal in position; 9th ventrite of male with paired macrosetae and pointed apicolateral teeth (Fig. 67E); 10th tergum elongate, rounded apically (Fig. 67B, C); aedeagal median
lobe with apical sclerotized area wide, angulate apicolaterally, often medially with a longitudinalridge (Fig. 67A); endophallic expulsion hooks fused to form a nearly U- (Fig. 67H) or H-shapedsclerite; gonocoxite with apicolateral tooth incurved, acute (Fig. 67F); spermatheca not observable.
Stenus ruralis Erichson(Figs. 67A–H, 131G)
Stenus ruralis Erichson, 1840: 697; Herman, 2001: 2374; Naomi & Puthz, 2013: 138; Naomi &Watanabe, 2015: 109.
Type material examined. Lectotype: ♂ (MNB), type locality: Austria [designated by Puthz,
1967: 289].
Other material examined. [HOKKAIDO]: 1 ♂1 ♀, Hakodate, Japan, G. Lewis leg.; 1 ♂, Kuccharo Lake, Kawayu, Teshikaga, 6. vi. 1992, M. Ohara leg. [HONSHU]: 1 ♂ (TUAA), Sasaguchi-hama, N.-Echigo (Niigata Pref.), 9. v. 1961, K. Baba leg.; 6 ♂5 ♀, Kamanashi River nearNirasaki, Yamanashi Pref., 1974, H. Franz (Mus. Vienna and cP); 1 ♂, Tatsikama (Tachikawa inTokyo?), v. 1910, Museum Paris (coll. Jarrige).
Distribution. Japan (Hokkaido, Honshu); Korea, China, Mongolia, Azerbaijan, Russia,
Europe.
Redescription. Male and female: Macropterous; body 3.5–4.0 mm (fore body 1.8–2.1 mm) in
length, moderately shining, with short antennae and relatively long legs. Body black, covered
with silvery pubescence; labrum and maxillary palpi black; antennae with ﬁrst 2 segments black,3rd to 11th dark red; legs dark red to black. Head relatively small, hardly concave, with a pair of
longitudinal depressions; punctures round to elliptical, very dense, various in size, distinct. Pronotum with surface weakly uneven, with an indistinct median longitudinal depression; puncturesround to elliptical, very dense, various in size. Elytra with surface almost smooth or weakly
uneven; punctures very dense, round to elliptical in shape but variable from regular to subrugose
conditions. Legs with tarsi short, 4th tarsomere simple. Abdomen narrowed posteriorly; 3rd to
6th terga each with 4 short basi-longitudinal keels; punctures round, dense and regular throughout, but those in anterior segments a little larger than in posterior segments. Lateroventrites ven-

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171

Fig. 67. Stenus ruralis Erichson (A, B, D, E, G, H, Teshikaga, Hokkaido; C, F, Liaoning, China). A, aedeagus;
B, 9th and 10th terga of male; C, 9th and 10th terga of female; D, 7th to 8th ventrites of male; E, 9th ventriteof male; F, gonocoxite; G, endophallic basal tube (dorsal view); H, expulsion hook. Scale 1: 0.2 mm for A–C,
E, 0.1 mm for F–H; scale 2: 0.3 mm for D.

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Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

tromesial to horizontal in position, distinct, punctate.
Male: Seventh ventrite (Fig. 67D) posteromedially with a semicircular ﬂat area, which iscovered with setae; 8th ventrite (Fig. 67D) posteromedially with an arcuate emargination; 9th
tergum (Fig. 67B) with ventral apophyses moderately long; 9th ventrite (Fig. 67E) elongatesubovoidal in shape, arcuate posteriorly and very ﬁnely serrate at posterior margin, with stemtransverse, apicolateral teeth thin, strongly incurved, macrosetae paired, apicolateral setae short;
10th tergum (Fig. 67B) elongate, rounded posteriorly. Aedeagal median lobe (Fig. 67A) wide,
distinctly angulate apicolaterally, obtusely angulate apically; apical sclerotized area mediallywith a longitudinal ridge. Endophallic median longitudinal bands (Fig. 67A) very long, a little
thick anteriorly; expulsion hooks fused to form a nearly U-shaped sclerite (Fig. 67A), which isprovided apicolaterally with a short, pointed projection (Fig. 67H); basal tube (Fig. 67A) short,
weakly curved, observable only from the dorsal side (Fig. 67G). Parameres (Fig. 67A) thin,weakly incurved; stem weakly constricted before the apical swollen area, which is furnished with17 to 18 moderately long setae.
Female: Eighth ventrite rounded posteriorly; 9th tergum (Fig. 67C) without ventral apophyses; gonocoxites (Fig. 67F) each with apicolateral tooth strongly incurved, pointed; 10th tergum(Fig. 67C) elongate, rounded posteriorly. Spermatheca not observable.
Biology and Ecology. S. ruralis is a very rare Stenus species in Japan. Although the information is missing as to the habitats of S. ruralis in Japan, but judging from the collecting data, thebeetles probably inhabit dry riverbeds in or near the natural forests of plains and low mountainous regions, as in Europe (Ganglbauer, 1895).
Remarks. Stenus ruralis was ﬁrst recorded from Japan (Hokkaido: Hakodate) by Puthz(1968b). S. ruralis is allied to S. palposus Zetterstedt, 1838, but this species is separable from thelatter by the body smaller, and the pronotum broadest near the middle, and gradually, lineallynarrowed basally, with its median longitudinal depression indistinct (Lohse, 1964).
Species group of S. melanarius Stephens
S. melanarius group consists of 2 species in Japan; see Puthz (1980b) regarding the taxonomy of this group. Diagnostic characters are as follows: Legs with 4th tarsomeres simple; abdomen with 4 short basi-longitudinal keel in each of 3rd to 6th terga, lateroventrites dorsomesial toventromesial in position, narrow; 9th ventrite of male with apicolateral teeth pointed (Fig. 69D);
10th tergum elongate (Fig. 69A); aedeagal median lobe with apical sclerotized area subtriangular(Fig. 68A) or subrectangular (Fig. 69E); endophallic expulsion hooks fused to form a nearlyH-shaped sclerite (Fig. 69F); gonocoxite with apicolateral tooth acutely pointed (Fig. 69G); spermatheca not observable.
Key to the Japanese species of S. melanarius group1(2) Body larger (3.5–4.1 mm); elytra with punctures denser, often weakly subrugose; abdomenwith anterior segments more densely punctate; aedeagal median lobe broader, with apicalsclerotized area subtriangular (Fig. 68A) ........................................................ S. boops Ljungh
2(1) Body smaller (2.7–3.3 mm); elytra with punctures sparser, distinct; abdomen with anterior
segments less densely punctate; aedeagal median lobe narrower, with apical sclerotized area
subrectangular (Fig. 69E, I).................................................................. S. melanarius Stephens

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Stenus boops Ljungh(Figs. 68A–F, 131H)
Stenus boops Ljungh, 1810: 158; Herman, 2001: 2095; Naomi & Puthz, 2013: 138.
Type material. Type locality: Skjarsjo.
Other material examined. [HOKKAIDO]: 8 ♂2 ♀, Utonai Lake, Chitose City, 20. vi. 1999,
M. Maruyama leg.; 1 ♂1 ♀, Kirakotan, Kushiro Moor, 25. viii. 1980, M. Sato leg.; 1 ♀, Tannocho, 28. viii. 1992, T. Kato leg.; 1 ♀, Ashoro, 13. vi. 1984, O. Tadauchi leg.
Distribution. Japan (Hokkaido); Mongolia, Georgia, Russia, Europe.
Redescription. Male and female: Macropterous; body 3.5–4.1 mm (fore body 1.8–2.1 mm) in
length, weakly shining to matt, with short antennae and relatively short legs. Body black; labrum
black; antennae with 1 or 2 basal segments black, remaining segments dark red; legs dark red toblack. Head relatively small, hardly concave, with a pair of shallow, longitudinal depressions;punctures round to elliptical, very dense, various in size, distinct. Pronotum with surface very
weakly uneven; punctures round, very dense, somewhat irregular. Elytra with surface very
weakly uneven; punctures round to elliptical, very dense, often subrugose. Legs with tarsi short,
4th tarsomere simple. Abdomen narrowed posteriorly; 3rd to 6th terga each with 4 short basi-longitudinal keels; punctures round, moderately dense and very small in anterior segments, while
punctures in posterior segments elliptical, dense, very small and regular. Lateroventrites ventromesial to dorsomesial in position, narrow, punctate.
Male: Seventh ventrite posteromedially with a semicircular ﬂat area; 8th ventrite posteromedially with a shallow (Fig. 68D) or moderately deep, broad emargination; 9th tergum (Fig. 68C)
with ventral apophyses moderately long; 9th ventrite (Fig. 68B) elongate-ovoidal in shape, arcuate posteriorly and very ﬁnely serrate at posterior margin, with apicolateral teeth strongly
incurved, acute, macrosetae paired, apicolateral setae moderately long; 10th tergum (Fig. 68C)
elongate, rounded posteriorly. Aedeagal median lobe (Fig. 68A) broad, distinctly angulate apicolaterally, with a very small apicomedian projection; apical sclerotized area subtriangular, anterolaterally with an oblique depression. Endophallic median longitudinal bands (Fig. 68A) very
long, broad, straight; expulsion hook (Fig. 68A) nearly H-shaped, with posterolateral arm
incurved apically; basal tube (Fig. 68A) submembranous except for apical elongate-rectangularsclerite, with a large basal ring. Parameres (Fig. 68A) relatively thick; apical area short, weakly
swollen mesially, furnished mesially with 20 to 25 setae of various length.
Female: Eighth ventrite rounded posteriorly; gonocoxites (Fig. 68F) each with apicolateral
tooth very acute, apicolatral setae long; basal porch of spermatheca (?) existing between the
gonocoxites (Fig. 68E) elongate, with sclerotized rim; 10th tergum elongate, obtuse apically.
Spermatheca not observable.
Biology and Ecology. Stenus boops is distributed in the plains and low mountainous regionsin Hokkaido. The beetles inhabit moist litter at or near the shores of rivers, lakes and marshes.
Remarks. Stenus boops was ﬁrst discovered from Japan (Hokkaido) by Naomi & Puthz(1994a). This species is allied to S. incrassatus Erichson, 1939 known from the Palaearctic
region, but it is separable from the latter by the head wider than pronotum (Fig. 131H), the elytra
hardly longer than pronotum, without depression near the suture (Lohse, 1964), and the aedeagal
median lobe wider, with its apical sclerotized area subtriangular (Fig. 68A). Among the Japanese
members of this species group, S. boops is similar to S. melanarius, but it is separable from thelatter by the body larger (3.5–4.1 mm), the elytra with punctures denser, often weakly subrugose,174

Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

Fig. 68. Stenus boops Ljungh (A–C, Kushiro, Hokkaido; D–F, Utonai, Hokkaido). A, aedeagus; B, 9th ventriteof male; C, 9th and 10th terga of male; D, 8th ventrite of male; E, basal pouch of spermatheca; F, gonocoxite.
Scale 1: 0.2 mm for A, B, F, 0.1 mm for E; scale 2: 0.2 mm for C; scale 3: 0.3 mm for D.

the abdomen with anterior segments more densely punctate, the aedeagal median lobe broader(Fig. 68A), with apical sclerotized area subtriangular, with a very small apicomedian projection(Fig. 68A).

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Stenus melanarius Stephens(Figs. 69A–J, 131I)
Stenus melanarius Stephens, 1833: 299; Herman, 2001: 2276; Puthz, 2008a: 149; Naomi &Puthz, 2013: 138.
Stenus verecundus Sharp, 1874: 81; Puthz, 2008a: 149 (synonym of S. melanarius).
Stenus melanarius verecundus Sharp: Benick, 1941: 281.
Stenus hiroyukii Puthz, 2001d: 103. New synonym.
Type material. Type localities: Suffolk, New Forest, Bristol.
Other material examined. [HOKKAIDO]: 1 ♂2 ♀, Hyotan Pond, Akan N. P., 4. vii. 1986, S.
Nomura leg.; 1 ♀, Akanuma, Kushiro Moor, 28. viii. 1990, M. Sato leg.; 1 ♀, Sapporo Lake, Sapporo City, 21. vi. 1994, T. Kishimoto leg. [HONSHU]: 1 ♀, Obanazawa City, Yamagata Pref., 2.
viii. 1994, K. Ohgi leg.; 1 ♀, Akigase, Urawa City, Saitama Pref., 8. v. 1994, K. Ohgi leg.; 1 ♂,Kasumigaseki, Kawagoe, Saitama Pref., 3. iv. 1994, K. Ohgi leg.; 1 ♀, Urawa City, Saitama
Pref., 16. iv. 1994, K. Ohgi leg.; 1 ♀, Imori, Saitama Pref., 11. v. 1994, K. Ohgi leg.; 2 ♀,Numata, Gunma Pref., 10. v. 1951, T. Takei leg.; 1 ♂, Watarase River, Fujioka-cho, Tochigi Pref.,1. iv. 1997, M. Maruyama leg.; 1 ♂2 ♀, Nakaminato, Ibaraki Pref., 8. iv. 1978, M. Tao leg.; 1 ♂,Kisarazu City, Chiba Pref., 7. vii. 1985, M. Tao leg.; 1 ♂, Miyaura-cho, Awa-gun, Chiba Pref.,14. v. 1978, M. Tao leg.; 2 ♂2 ♀, Fudago, Kimitsu City, Chiba Pref., 20. iv. 1989, S. Naomi leg.;1 ♂, Hachioji City, Tokyo Metropolis, 20. v. 1978, M. Tao leg.; 1 ♂, Tama River, Fuchu City,
Tokyo Metropolis, 29. viii. 1982, M. Tao leg.; 1 ♀, Yokohama City, Kanagawa Pref., 3. iv. 1977,
M. Tao leg.; 1 ♂, Kawasaki City, Kanagawa Pref., 10. iv. 1977, M. Tao leg.; 1 ♀, Noborito,
Kanagawa Pref., 25. iii. 1978, M. Tao leg.; 1 ♂, Yokohama City, Kanagawa Pref., 29. iv. 1984,
M. Tao leg.; 2 ♀, Tsurumi, Yokohama City, Kanagawa Pref., 16. v. 1987, M. Tao leg.; 1 ♀, Ikenokochi, Fukui Pref., 22. viii. 1974, H. Sasaji leg.; 3 ♂3 ♀, Senami Spa, Murakami, Niigata Pref., 5.
v. 2000, M. Nishikawa leg.; 1 ♂, Mt. Komagatake, Kamiina, Nagano Pref., 9. viii. 1959, H.
Yokoyama leg.; 1 ♂, Handa City, Shizuoka Pref., 12-14. vii. 1989, S. Saito leg.; 1 ♀, Nisshin,
Aichi Pref., 25. xii. 1985, T. Kato leg. [KYUSHU]: 2 ♂4 ♀, Imazu, Fukuoka City, Fukuoka Pref.,29. i. 1989, S. Nomura leg.; 2 ♀, Mt. Tsubaki, Hamatama-cho, Saga Pref., 10. vi. 1990, S.
Nomura leg.
Distribution. Japan (Hokkaido, Honshu, Shikoku, Kyushu; Sado Is., Tane Is.); Korea, Taiwan, China, Philippines, Indonesia, Vietnam, Myanmar, Nepal, India, Sri Lanka, Mongolia, Russia, Georgia, Azerbaijan, Turkey, Iran, Europe, Canada, USA.
Redescription. Male and female: Macropterous; body 2.7–3.3 mm (fore body 1.5–1.7 mm) in
length, weakly shining to matt, with short antennae and relatively short legs. Body black; labrum
black; antennae with 1 or 2 basal segments black, remaining segments dark red; legs dark red toblack. Head relatively small, hardly concave, with a pair of indistinct longitudinal depressions;punctures round to almost round, very dense, various in size, distinct. Pronotum with surface
weakly uneven; punctures round to almost round, very dense, somewhat irregular. Elytra withsurface very weakly uneven, with weak longitudinal depressions along suture; punctures roundto almost round, very dense, distinct. Legs with tarsi short, 4th tarsomere simple. Abdomen narrowed posteriorly; 3rd to 6th terga each with 4 short basi-longitudinal keels; punctures very
round, sparse to moderately dense, and small in anterior segments, while punctures in 7th and 8th
segments round to elliptical, dense and very small. Lateroventrites ventromesial in position, narrow, punctate.

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Fig. 69. Stenus melanarius Stephens (A, C, D, H, I, Hachioji, Tokyo; B, E, F, Komagatake, Nagano; G, J, Nakaminato, Ibaraki). A, 9th and 10th terga of male; B, 9th ventrite of male; C, apex of 8th ventrite of male; D,posterior half of 9th ventrite of male; E, aedeagus; F, endophallic expulsion hook; G, gonocoxite; H, basal
tube; I, posterior half of aedeagus; J, basal pouch of spermatheca and its related sclerite. Scale 1: 0.2 mm for
A, B, D, E, G, I, J, 0.1 mm for F, H; scale 2: 0.3 mm for C.

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Male: Eighth ventrite (Fig. 69C) posteromedially with a shallow, wide emargination; 9th tergum (Fig. 69A) with ventral apophyses moderately long; 9th ventrite (Fig. 69B, D) elongateovoidal in shape, arcuate posteriorly (Fig. 69D) or almost straight at posterior margin (Fig. 69B)
which is very ﬁnely serrate, with stem short, apicolateral teeth hook-like, strongly acute, apicolateral setae short to moderately long; 10th tergum (Fig. 69A) elongate, rounded apically. Aedeagal median lobe (Fig. 69E) elongate, rounded or obtusely angulate (Fig. 69I) apicolaterally, withapicomedian projection long, weakly swollen at tip; apical sclerotized area (Fig. 69E, I) large,
subrectangular, medially with a low longitudinal keel, and anterolaterally with a shallow, obliqueimpression. Endophallic median longitudinal bands (Fig. 69E) very long, distinctly diverging
anteriorly; expulsion hook (Fig. 69E, F) nearly H-shaped, with its connecting rod arcuate anteriorly; basal tube (Fig. 69H) submembranous except for sclerotized basal room and weakly spatulate apical sclerite. Parameres (Fig. 69E) thin, slender, straight, pointed apically; apical area
hardly swollen mesially, and furnished mesially with 17 to 18 setae of various length.
Female: Eighth ventrite rounded posteriorly; gonocoxites (Fig. 69G) each with apicolateral
tooth hook-shaped, very acute, apicolateral setae moderately long; basal pouch of spermatheca(?) elongate (Fig. 69J); a sclerite existing between the gonocoxites transverse (Fig. 69J); 10th tergum elongate, obtusely rounded apically. Spermatheca not observable.
Biology and Ecology. S. melanarius is one of the common Stenus species in Japan, but relatively rare in Shikoku and Kyushu. It is widely distributed in the plains and low mountainous
regions. The beetles have diverse habitat preferences as follows: They inhabit moist places at theshores of rivers, lakes and marshes and the grasslands near there; and they live in the moist litterand near or under stones there. They often walk on wet rocks and mosses near the running waterin mountain streams. They also sometimes inhabit the sea algae.
Remarks. Sharp (1874) ﬁrst described Stenus verecundus from Japan as an allied species to S.
melanarius. Benick (1941) regarded S. verecundus as a subspecies of S. melanarius; and thus theJapanese population of this Stenus species has long been called S. melanarius verecundus Sharp
by Japanese Coleopterists (e.g., Watanabe, 1985). S. melanarius is in fact widely distributed in
the whole region of Northern hemisphere; and it shows considerable amounts of intraspeciﬁcvariations, especially with the density of punctures on body and the size of elytra. Puthz (2008a)
re-examined those variations in detail, resulting in the synonymic status of S. verecundus with S.
melanarius. This is also the case of S. hiroyukii Puthz, 2001d; and thus S. hiroyukii is herein
newly placed in synonym with S. melanarius.
S. melanarius is allied to S. subdepressus Mulsant et Rey, 1861 from Europe, but this species
is separable from the latter by the body larger in size (2.7–3.3 mm), the elytra distinctly wider,somewhat longer than pronotum, each with a weak longitudinal depression along suture (Lohse,1964), and the aedeagal median lobe with apicomedian projection (Fig. 69E, I). Among the Japanese members of this species group, S. melanarius is similar to S. boops, but this species is separable from the latter by the body smaller, the elytra with punctures a little sparser and distinct, theabdomen with anterior segments sparsely punctate, the aedeagal median lobe narrower (Fig.
69E), with apical sclerotized area subrectangular, with a long apicomedian projection (Fig. 69E,
I).
Species group of S. canaliculatus Gyllenhal
S. canaliculatus group consists of 2 species in Japan; see Benick (1925) and Ryvkin (2012)
for a review of, and a key to the species of this group. Diagnostic characters are as follows: Head

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Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

not broader than elytra (Fig. 131K); pronotum usually a median longitudinal furrow; legs with
4th tarsomere simple; abdomen with 4 short basi-longitudinal keels in each of 3rd to 6th terga;
lateroventrites ventromesial to horizontal in position, narrow to moderately broad; 9th ventrite ofmale with apicolateral teeth (Fig. 70B); 10th tergum of male rounded posteriorly (Fig. 70E);
aedeagal median lobe relatively broad (Fig. 70C) or slender (Fig. 71A), pointed apically; endophallic expulsion hooks fused to form an almost H- or M-shaped sclerite (Fig. 70C); gonocoxitewith apicolateral tooth pointed (Fig. 70B); spermatheca with tube thick, with 3 or 4 turns (Fig.
70D).
The presence of a median longitudinal furrow on the pronotum is a diagnostic character ofthis species group (Benick, 1925). This will be appropriately considered so, but the median longitudinal furrow is missing on the pronotum in the Japanese species (S. raddei and S. shogun).
As far as S. raddei is concerned, the median longitudinal furrow certainly exists at the base of
pronotum in the specimens from Maritime Prov., etc., (Ryvkin, 1987c: 157, and by our observation), but it is missing in the specimens from Hokkaido, suggesting that this species shows an
infraspeciﬁc variation regarding this character.
Key to the Japanese species of S. canaliculatus group1(2) Elytra distinctly smaller, narrower (Fig. 131J); abdomen less strongly narrowed posteriorly(Fig. 131J); aedeagal median lobe broader, with apical sclerotized area shorter (Fig. 70C)........................................................................................................................ S. raddei Ryvkin2(1) Elytra distinctly larger, broader (Fig. 131K); abdomen more strongly narrowed posteriorly(Fig. 131K); and aedeagal median lobe much narrower, with apical sclerotized area longer(Fig. 71A) .........................................................................................................S. shogun Puthz
Stenus raddei Ryvkin(Figs. 70A–F, 131J)
Stenus raddei Ryvkin, 1987c: 156; Naomi & Puthz, 1994: 219; Herman, 2001: 2365; Naomi &Puthz, 2013: 139; Ryvkin, 2012: 12.
Type material examined. Paratype: 1 ♂ (ZMMSU), type locality: Kedrovaya Pad [examinedby Puthz].
Other material examined. [HOKKAIDO]: 1 ♂, Akanuma, Kushiro Moor, 25. viii. 1990, M.
Sato leg.; 1 ♂, same locality, 28. viii. 1990, M. Sakai leg.; 1 ♀, Onʼnenai, Tsurui, Kushiro Moor,
24. viii. 1990, M. Sakai leg.
Distribution. Japan (Hokkaido); China, Russia.
Redescription. Male and female: Macropterous; body 3.3–3.4 mm (fore body 1.6–1.8 mm) in
length, weakly to moderately shining, with relatively short antennae and legs. Body black;labrum black; antennae with 1 or 2 basal segments black, remaining segments dark red; legs dark
red to black. Head hardly concave dorsally nor with longitudinal depressions; punctures basicallyelliptical but sometimes round, very dense, various in size. Pronotum with surface very weakly
uneven, without median longitudinal depression; punctures round, very dense, various in size,
distinct. Elytra with surface very weakly uneven; punctures round, very dense, almost regular,
distinct. Legs with fore and mid tarsi short, hind tarsi relatively long, 4th tarsomere simple.
Abdomen weakly narrowed posteriorly; 3rd to 6th terga each with 4 short basi-longitudinal

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Fig. 70. Stenus raddei Ryvkin (A–C, E, Akanuma, Hokkaido; D, F, Amur, Russia). A, 5th to 8th ventrites ofmale; B, 9th ventrite of male; C, aedeagus; D, spermatheca; E, 9th and 10th terga of male; F, apex of gonocoxite. Scale 1: 0.3 mm for A; scale 2: 0.1 mm for B, C; scale 3: 0.2 mm for E, 0.1 mm for D, F.

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keels; punctures sparse and very small in anterior segments, while punctures in posterior segments moderately dense and very small to small. Lateroventrites ventromesial to horizntal in
position, narrow to moderately wide, punctate.
Male: Fifth ventrite (Fig. 70A) posteromedially with a semicircular ﬂat area; 6th ventrite(Fig. 70A) posteromedially with a very large, shallow, bell-shaped depression, which is very
weakly emarginate posteriorly, and furnished with sparse setae along posterior margin; 7th ventrite (Fig. 70A) posteromedially with a very large, bell-shaped depression, which is arcuately
emarginate, and furnished with setae along posterior margin; 8th ventrite (Fig. 70A) posteromedially with a wide, triangular emargination; 9th tergum (Fig. 70E) relatively wide, short, withventral apophyses relatively long, posterolateral projections long; 9th ventrite (Fig. 70B) wide,
widely rounded anterolaterally, with stem short, apicolateral teeth acutely pointed, apicolateral
setae long; 10th tergum (Fig. 70E) entire. Aedeagal median lobe (Fig. 70C) relatively wide,
rounded apicolaterally, simply pointed apically; apical sclerotized area triangular. Endophallic
median longitudinal bands (Fig. 70C) very long, each narrowed apically; lateral longitudinalbands (Fig. 70C) very short and thin; expulsion hook (Fig. 70C) almost H-shaped; basal tube
(Fig. 70C) with basal room weakly swollen, tube body rod-like, attenuate; median sclerite (Fig.
70C) arrowhead-shaped, sclerotized. Parameres (Fig. 70C) slender; apical area long, weakly
swollen mesially, and furnished mesially with 14 to15 setae.
Female: Eighth ventrite obtusely angulate posteromedially; gonocoxites (Fig. 70F) eachhardly serrate posteriorly, with apicolateral tooth large, acute. Spermatheca (Fig. 70D) with capsule very small, conical; RT-duct moderately long, thick; spermathecal duct thick, tightly coiled,with 4 turns; basal valve not observable.
Biology and Ecology. S. raddei is a rare Stenus species in Japan; and it is presently known
only from Kushiro Moor in Hokkaido. The beetles inhabit moist litter of the grasses grown at theshore of the Moor.
Remarks. Stenus raddei was ﬁrst discovered from Hokkaido, Japan by Naomi & Puthz(1994a). This species is allied to S. latipennis Sahlberg, 1880 from Holaractic region and S. illusor Ryvkin, 1987c from Russia, but it is separable from the latter two species by the head almost
smooth (i.e., not depressed laterally nor convex medially) between eyes, and the aedeagal
median lobe not constricted (but only narrowed) near the middle and more strongly pointed atapex (Fig. 70C). Among the Japanese members of this species group, S. raddei is similar to S.
shogun, but it is separable from the latter by the elytra distinctly smaller and narrower, the abdomen less strongly narrowed posteriorly, and the aedeagal median lobe much wider, with apicalsclerotized area shorter (Fig. 70C).
Etymology. The speciﬁc epithet of this species is named after a Russian zoologist, Mr. G. I.
Radde.
Stenus shogun Puthz(Figs. 71A–F, 131K)
Stenus shogun Puthz, 1987: 45; Herman, 2001: 2388; Naomi & Puthz, 2013: 139; Naomi & Ito,2014: 290.
Type material examined. Holotype: ♂ (IRSNB), type locality: Nishigo, Uzan, [examined by
Puthz].
Other material examined. [HONSHU]: 1 ♂2 ♀, Oze Moor, Katashina-mura, Gunma Pref.,The Steninae of Japan Part 1

181

Fig. 71. Stenus shogun Puthz (Oze, Gunma). A, aedeagus; B, 9th ventrite of male; C, 9th and 10th terga of male;
D, 6th to 8th ventrites of male; E, apex of gonocoxite; F, spermatheca. Scale 1: 0.1 mm for A, B; scale 2: 0.2
mm for C, 0.1 mm for E, F; scale 3: 0.3 mm for D.

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23. x. 1994, H. Sakayori leg.
Distribution. Japan (Honshu).
Redescription. Male and female: Macropterous; body 3.3–3.7 mm (fore body 1.7–1.9 mm) in
length, moderately to strongly shining, with relatively short antennae and legs. Body black;labrum black; antennae with 1 or 2 basal segments black, remaining segments dark red; legs dark
red to black. Head small, with indistinct longitudinal depressions; punctures round to elliptical,very dense, various in size, distinct. Pronotum with surface almost smooth, without median longitudinal depression; punctures round to elliptical, very dense, various in size, distinct. Elytra
large, with surface very weakly uneven; punctures round, very dense, almost regular, distinct.
Legs with tarsi short, 4th tarsomere simple. Abdomen narrowed posteriorly; 3rd to 6th terga eachwith 4 short basi-longitudinal keels; punctures sparse and very small in all segments. Lateroventrites ventromesial to horizontal in position, narrow to relatively wide, punctate.
Male: Fifth ventrite posteromedially with a semicircular ﬂat area; 6th ventrite (Fig. 71D)
posteromedially with a shallow, bell-shaped depression; 7th ventrite (Fig. 71D) posteromediallywith a large, subovoidal depression, which is emarginate posteriorly and distinctly ridged laterally; 8th ventrite (Fig. 71D) posteromedially with a triangular emargination; 9th tergum (Fig.
71C) relatively broad, uniquely bisinuate at anterodorsal margin, with ventral apophyses very
thin, long; 9th ventrite (Fig. 71B) elongate, with stem elongate, rounded apically, apicolateral
teeth large, acute, macrosetae paired, apicolateral setae long; 10th tergum (Fig. 71C) entire.
Aedeagal median lobe (Fig. 71A) very slender, narrowed apically, pointed at apex; apical sclerotized area rather long. Endophallic median longitudinal bands (Fig. 71A) moderately long, eachnarrowed apically; lateral longitudinal bands (Fig. 71A) wide; expulsion hook (Fig. 71A) almost
M-shaped; basal tube (Fig. 71A) with basal room elongate-ovoidal in shape, partly submembranous, tube body short, thin, weakly curved; median sclerite (Fig. 71A) consisting of basal ovoidal plate and apical thin process. Parameres (Fig. 71A) thick, straight, each pointed apically;basal area with posteromesial projection elongate, submembranous at its base; apical area very
long, hardly or weakly swollen mesially, and furnished mesially with 15 to18 setae.
Female: Eighth ventrite obtusely angulate posteromedially; gonocoxites (Fig. 71E) eachhardly serrate posteriorly, with apicomesial tooth acute, apicolateral tooth large, pointed, apicolateral setae very long. Spermatheca (Fig. 64F) with capsule small, rounded apically; RT-ductmoderately long and thick; spermathecal duct thick, almost tightly coiled, with 3 turns; basal
valve not observable.
Biology and Ecology. S. shogun is a very rare Stenus species in Japan; and it is distributed in
the mountainous regions. The beetles inhabit moist litter of grasses grown at the shore of moor.
Remarks. Stenus shogun was newly described by Puthz (1987) from Nishigo, Uzan (Honshu?), Japan, based on one male specimen. This species is allied to S. canaliculatus Gyllenhal,1827 from Holarctic region and S. vinnulus Casey, 1884 from North America and Finland, but it
is separable from the latter two species by the dorsum of body not covered with net-like microsculpture. Among the Japanese members of this species group, S. shogun is similar to S. raddei,
but this species is separable from the latter by the elytra distinctly larger and wider, the abdomen
more strongly narrowed posteriorly and the aedeagal median lobe much narrower, with apicalsclerotized area longer (Fig. 71A).
Etymology. The speciﬁc epithet of this species is named after the Japanese term “Shogun”
which means “Shogunate”.

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Species group of S. incanus Erichson
S. incanus group (including S. puberulus group; Puthz, 2002: 131) consists of 2 species inJapan; see Puthz (2002, 2012b) for a characterization and taxonomic information of this group.
Diagnostic characters are as follows: Legs with 4th tarsomere simple; abdomen without basi-longitudinal keels on terga; lateroventrites ventromesial to horizontal in position, narrow to moderately wide; 9th ventrite of male with apicolateral teeth acute, apicolateral setae very long (Fig.
72E); aedeagal median lobe narrowed apically, with more or less triangular apical sclerotizedarea (Fig. 72A); parameres more or less short and thick (Fig. 72A); endophallic expulsion hookwith posterior plates widely separated (Fig. 72A); gonocoxite with apicolateral tooth acute, apicolateral setae very long (Fig. 72B); spermatheca not observable.
Key to the Japanese species of S. incanus group1(2) Legs reddish brown to dark reddish brown; abdomen with punctures smaller and sparser;
7th ventrite of male posteromedially with a semicircular, shallow depression, which is more
shallowly emarginate (Fig. 72C); aedeagus distinctly broader, more obtusely pointed apically (Fig. 72A); parameres longer (Fig. 72A)............................................ S. puberulus Sharp
2(1) Legs dark red to dark brown; abdomen with punctures larger and denser; 7th ventrite ofmale posteromedially with a semicircular, ﬂat area, which is more deeply emarginate;aedeagus distinctly narrower, more acutely pointed apically (Fig. 73B); parameres shorter...................................................................................................S. aboblitus Naomi & Nomura
Stenus puberulus Sharp(Figs. 72A–F, 131L)
Stenus puberulus Sharp, 1874: 83; Herman, 2001: 2355; Puthz, 2012b: 93; Naomi & Puthz,
2013: 139.
Stenus sasajii Naomi, 1988c: 43.
Type material examined. Syntypes: 2 exs. (NHML), type locality: Mitzuyama, Nagasaki[examined by Puthz].
Other material examined. [HONSHU]: 2 ♂, Shizukuishi River, Morioka, Iwate Pref., 9. v.
1970, J. Kamei leg.; 1 ♀, Honnou City, Saitama Pref., 3. iv. 1994, K. Ohgi leg.; 1 ♂, Mt. Takao,
Hachioji, Tokyo Metropolis, 1. vi. 1986, A. Izumi leg.; 1 ♂, Keitokuin, Koshu City, Yamanashi
Pref., 8. vii. 1988, T. Ito leg.; 1 ♀, Yanagawa, Ohtsuki City, Yamanashi Pref., 13. v. 1994, H.
Hayakawa leg.; 1 ♀, Hohare Pass, Gifu Pref., 8. v. 1986, K. Suzuki leg.; 3 ♂3 ♀, Mt. Koya,
Wakayama Pref., 2. v. 1968, T. Ito leg.; 1 ♂2 ♀, Ina River, Hyogo Pref., 15. iv. 1968, Y. Imai leg.;1 ♂1 ♀, Gohkei, Okayama Pref., 16. v. 1993, T. Ito leg.; 2 ♂, Sandan Valley, Hiroshima Pref., 1.
vi. 1986, I. Okamoto leg.; 1 ♀, Kabura-sugi, Saigo-cho, Dogo Is., Oki Isls., Shimane Pref., 17.
vii. 2003, T. Shimada leg. [SHIKOKU]: 1 ♀, Amagoi Fall, Kamiyama-cho, Tokushima Pref., 18.
v. 1996, M. Yoshida leg. [KYUSHU]: 1 ♀, Kuma River, Hitoyoshi City, Kumamoto Pref., 6. iv.
1977, S. Naomi leg.; 3 ♂, Shiratake, Tsushima Is. Nagasaki Pref., 7. vi. 1988, Y. Hayashi leg.
Distribution. Japan (Honshu, Shikoku, Kyushu; Oki Is., Tsushima Is.).
Redescription. Male and female: Macropterous; body 3.1–3.6 mm (fore body 1.5–1.8 mm) in
length, wholly covered with short, silvery pubescence, with antennae short. Body black, weakly

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Fig. 72. Stenus puberulus Sharp (A, Ina, Hyogo; B, D, Koya, Wakayama; C, E, F, Keitokuin, Yamanashi). A,
aedeagus; B, apex of gonocoxite; C, 7th to 8th ventrites of male; D, 9th and 10th terga of female; E, 9th ventrite of male; F, 9th and 10th terga of male. Scale 1: 0.1 mm for A; scale 2: 0.2 mm for C; scale 3: 0.1 mm for
B, 0.2 mm for D–F.

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185

shining; labrum black; antennae with 1 or 2 basal segments piceous, lustrous, remaining segments dark red; legs reddish brown to dark reddish brown. Head shallowly concave betweeneyes, with a pair of distinct longitudinal depressions; punctures round to elliptical, dense, distinct. Pronotum with surface very weakly uneven; punctures round, very dense, almost regular,
distinct. Elytra with surface almost smooth, similarly punctate as on pronotum, but punctures alittle larger than those on pronotum. Legs with tarsi short, 4th tarsomere simple. Abdomen subparallel-sided; 3rd to 6th terga without basi-longitudinal keels; punctures round, sparse to moderately dense, ﬁne and distinct throughout. Lateroventrites ventromesial to horizntal in position,
narrow to moderately wide, punctate.
Male: Body slender; 7th ventrite (Fig. 72C) posteromedially with a semicircular, shallow
depression, which is arcuately emarginate and furnished with sparse setae; 8th ventrite (Fig. 72C)
posteromedially with a wide-triangular emargination; 9th tergum (Fig. 72F) with ventral apophyses moderately long; 9th ventrite (Fig. 72E) elongate, very ﬁnely serrate posteriorly, with stem
short, apicolateral teeth short, pointed, apicolateral setae very long; 10th tergum (Fig. 72F)
entire. Aedeagal median lobe (Fig. 72A) moderately broad, narrowed apically behind the middle,
with apical sclerotized area subtriangular in shape, covered with very small pores, apicomedianprojection very small. Endophallic median longitudinal bands (Fig. 72A) very long, almost running in parallel; expulsion hook (Fig. 72A) large, with anterior plates mostly connate, posterior
plates widely separated, each well-sclerotied, baculiform, weakly incurved; basal tube (Fig. 72A)
entirely membranous, basal room very large, elongate-ovoidal, with a thin, almost straight,
setous tube in it, tube body acicular. Parameres (Fig. 72A) very thick, bluntly pointed, extending
posteriorly a little before the apex of median lobe; apical area distinctly swollen mesially, furnished with 18 to 19 setae of various length along the mesial margin.
Female: Body thicker than in male; 8th ventrite gently rounded posteriorly; 9th tergum without ventral apophyses (Fig. 72D); gonocoxites (Fig. 72B) each serrate posteriorly, with apicolateral tooth large, acute, apicolateral setae very long; 10th tergum entire (Fig. 72D).
Biology and Ecology. Stenus puberulus is distributed in the plains and low mountainous
regions in Japan. The beetles inhabit riverbanks and shores of rivers and lakes; and they also livein litter at the grasslands near there.
Remarks. Stenus puberulus is closely allied to S. aboblitus, but this species is separable fromthe latter by the legs paler in coloration (reddish brown to dark reddish brown) the abdomen with
punctures smaller and sparser, the 7th ventrite of male posteromedially with a semicircular, shallow depression (Fig. 72C), the aedeagal median lobe distinctly broader, and more obtusely
pointed apically, with longer paramere (Fig. 72A). Stenus species that has been previously
recorded from Korea as S. puberulus all are S. pubiformis Puthz, 2012b. Thus, S. puberulus ispresently indigenous to Japan.
Stenus aboblitus Naomi & Nomura(Figs. 73A–F, 132A)
Stenus aboblitus Naomi & Nomura, 2015a: 55.
Stenus puberulus Sharp, 1974: Naomi, 1988c: 39, ﬁg. 1D (partim); Puthz, 2012b: 93, 97, ﬁgs.
25–26 (partim).
Type material examined. Holotype: ♂ (NMNST), Okuyagen, Shimokita Peninsula, Aomori
Pref., 2. viii. 1987, S. Nomura leg. Paratypes: 2 ♂3 ♀ (cN), same data as holotype; 1 ♂, Ikushina

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Fig. 73. Stenus aboblitus Naomi & Nomura (A–C, E, F, Okuyagen, Aomori; D, Hakken, Hokkaido). A, gonocoxite; B, aedeagus; C, 9th and 10th terga of male; D, 8th ventrite of male; E, 9th ventrite of male; F, apex of
aedeagal paramere; G, 9th and 10th terga of female. Scale : 0.1 mm for A, F, 0.2 mm for B–E, G.

River, Ikushina, Shari-cho, Hokkaido, 11. vi. 2014, T. Kato leg.; 1 ♂1 ♀ (cN), Mt. Hakken-zan,
Hokkaido, 27. v. 1997, N. Nishikawa leg.; 1 ♂ (cN), Misumai, Sapporo, Hokkaido, 7. vii. 1977,
S. Naomi leg. [HONSHU]: 1 ♂ (NMNST), Yugawa River, Wakamatsu, Fukushima Pref., 1. viii.
1948, Y. K. leg.; 1 ♂ (cN), Shiobara, Tochigi Pref., 22. viii. 1976, T. Niisato leg.; 1 ♂ (NMNST),
Ohme, Tokyo Metropolis, 19. viii. 1976, Y. Kurosawa leg.; 2 ♂ (cN), Yoro Valley, Ichihara,
Chiba Pref., 9. v. 1993, K. Ohgi leg.
Other material examined. [HONSHU]: 1 ♀, Sakawa River near Odawara, Kanagawa Pref., 5.
v. 1978, S. Morita leg.

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Distribution. Japan (Hokkaido, Honshu).
Redescription. Male and female: Macropterous; body 2.7–3.0 mm (fore body 1.5–1.6 mm) in
length, wholly covered with short, silvery pubescence, with antennae short. Body black, weakly
shining; labrum black; antennae with 1 or 2 basal segments piceous, lustrous, remaining segments dark red; legs dark red to dark brown. Head concave between eyes, with a pair of distinct
longitudinal depressions, median longitudinal area between the depressions narrow; puncturesround to elliptical, dense, distinct. Pronotum with surface very weakly uneven; punctures round,very dense, regular, distinct. Elytra with surface similarly punctate as on pronotum, but punctures
a little larger than those on pronotum. Legs with tarsi short, 4th tarsomere simple. Abdomen subparallel-sided; 3rd to 6th terga without basi-longitudinal keels; punctures dense, distinct, small
and round throughout. Lateroventrites ventromesial to horizntal in position, narrow to relatively
wide, ﬁnely punctate.
Male: Seventh ventrite posteromedially with a lustrous, semicircular ﬂat area, which is moderately emarginate; 8th ventrite (Fig. 73D) posteromedially with a wide emargination; 9th tergum(Fig. 73C) with ventral apophyses short; 9th ventrite (Fig. 73E) elongate, ﬁnely serrate posteriorly, with stem relatively short, apicolateral teeth short, pointed, apicolateral setae very long;
10th tergum entire or very weakly emarginate (Fig. 73C). Aedeagal median lobe (Fig. 73B) narrow, gently rounded apicolaterally, with apical sclerotized area moderately long, subrectangular,
covered with very small pores, apicomedian projection relatively long. Endophallic median longitudinal bands (Fig. 73B) very long, narrow, almost running in parallel; expulsion hook (Fig.
73B) large, with anterior plates mostly connate, posterior plates widely separated, each wellsclerotied, baculiform, slender, weakly incurved; basal tube (Fig. 73B) entirely membranous,
basal room large, elongate-ovoidal, with a thin, setous tube in it, tube body almost baculiform,
weakly swollen in the middle. Parameres (Fig. 73B) thick, slightly incurved, rather short, notreaching the apex of median lobe; apical area very short or short, furnished mesially with 17 to
20 short (Fig. 73B) or long (Fig. 73F) setae.
Female: Body thicker than in male; 8th ventrite gently rounded posteriorly; 9th tergum (Fig.
73G) without ventral apophyses; gonocoxites (Fig. 73A) each irregularly serrate posteriorly, withapicolateral tooth acute, apicolateral setae very long; 10th tergum (Fig. 73G) entire.
Biology and Ecology. Stenus aboblitus is distributed in the plains and low mountainous
regions. The beetles inhabit riverbanks and shores of rivers and lakes; and they also live in litterat the grasslands near there.
Remarks. Stenus aboblitus is closely allied to S. puberulus, but this species is separable fromthe latter by the legs darker in coloration (dark red to dark brown), the abdomen with punctureslarger and denser, the 7th ventrite of male posteromedially with a semicircular, ﬂat area, theaedeagal medial lobe distinctly narrower, and more acutely pointed apically, with shorter paramere (Fig. 73B).
Species group of S. gibbicollis Sahlberg
S. gibbicollis group consists of 5 species in Japan; see Puthz (2002) for a review of thisgroup. Diagnostic characters are as follows: Legs with tarsi short, 1st tarsomere shorter than thefollowing two tarsomeres combined, 4th tarsomere simple; abdomen without basi-longitudinalkeels on terga; lateroventrites ventromesial to horizontal in position, basically wide to very wide;
9th tergum with a cleaning comb at posterior margin (in some species; Fig. 76A); 9th ventrite ofmale without apicolateral teeth but with macrosetae (Fig. 76B); aedeagal median lobe various in188

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shape, with more or less baculiform endophallic basal tube (Fig. 76C); gonocoxite with apicomesial tooth (Figs. 74D, 77D), apicolateral tooth missing (Fig. 76D); spermatheca sclerotized (Fig.
77A) or not observable.
Key to the Japanese species of S. gibbicollis group1(6) Head shorter, with eyes more strongly prominent laterally; lateroventrite wider, with a large,
elongate depression; aedeagus very acute apically, with (Fig. 74C) or without (Fig. 76C) the
apicalmost globe; gonocoxite basically without apicomesial tooth or with a small one (Fig.
74D); spermatheca not observable.
2(5) Apical sclerotized area of aedeagal median lobe without longitudinal impressions, with theapicalmost globe; endophallic expulsion hooks thinner; basal tube longer and broader.
3(4) Endophallic median longitudinal bands in situ separated (Fig. 74C); expulsion hook withanterior plate shorter than posterior plate (Fig. 74C); basal tube distinctly longer and thicker(Fig. 74B) ..................................................................................................... S. nomurai Naomi
4(3) Endophallic median longitudinal bands in situ contiguous in basal 2/3 (Fig. 75B); expulsion
hook with anterior plate about as long as posterior plate (Fig. 75B); basal tube shorter, witha very long, sclerotized lobe located right to the tube body (Fig. 75F) .....................................
..........................................................................S. varicosus Naomi, Nomura & Puthz sp. nov.
5(2) Apical sclerotized area of aedeagal median lobe with paired longitudinal impressions, without the apicalmost globe (Fig. 76C); endophallic expulsion hooks wider (Fig. 76C); basal
tube shorter and thinner (Fig. 76F–H) ......................................................S. mikado Hromádka
6(1) Head longer, with eyes less strongly prominent laterally; lateroventrite narrower, simply
punctate; aedeagus simply rounded or obtuse apically; gonocoxite with a large apicomesial
tooth (Fig. 77D); spermatheca sclerotized (Fig. 77A).
7(8) Aedeagal median lobes wider at apex (Fig. 77C); endophallic expulsion hooks much larger,
each elongate (Fig. 77C); paramere more strongly incurved and sclerotied apically, with 4 to
5 short setae (Fig. 77C) ............................................................................S. pudefactus Ryvkin8(7) Aedeagal median lobe narrower at apex (Fig. 78C); endophallic expulsion hooks very small,each ginko-shaped (Fig. 78C); paramere less strongly incurved and sclerotized apically, with
7 to 8 short setae (Fig. 78C) .......................................................................... S. miyama Naomi
Stenus nomurai Naomi sp. propr.
(Figs. 74A–F, 132B)
Stenus nomurai Naomi, 1988c: 45.
Stenus mikado Hromádka, 1979a: Naomi & Puthz, 1994a: 218 (synonym of S. mikado).
Type material examined. Holotype of S. nomurai: ♀ (KUF), Iwaubetsu, Shiretoko, Hokkaido, 7. vii. 1986, S. Nomura leg. Paratypes of S. nomurai: 2 ♂1 ♀ (cN), Mt. Kariba, Shiribeshi,
Hokkaido, 12. vi. 1986, S. Nomura leg.
Other material examined. [HOKKAIDO]: 1 ♂, Nukabira, Kamishihoro-cho, 25. vi. 2009, T.
Watanabe leg.; 2 ♂, Sekihoku Pass, 27. viii. 1977, M. Sato leg. [HONSHU]: 1 ♂1 ♀, Okukinu,
Tochigi Pref., 21. vii. 1987, S. Nomura leg.; 1 ♂1 ♀, Toubaku-zawa, Okuchichibu, Saitama Pref.,5. vi. 1986, K. Nemoto leg.
Distribution. Japan (Hokkaido, Honshu).

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Fig. 74. Stenus nomurai Naomi (A–C, Tobakuzawa, Saitama; D, F, Kariba, Hokkaido; E, Sekihoku, Hokkaido).
A, 9th and 10th terga of male; B, endophallic basal tube; C, aedeagus; D, apex of gonocoxite; E, 6th to 8th
ventrites of male F, 9th ventrite of male. Scale 1: 0.2 mm for A, B, F, 0.1 mm for D; scale 2: 0.2 mm for C;
scale 3: 0.3 mm for E.

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Redescription. Male and female: Macropterous; body 3.2–3.5 mm (fore body 1.7–1.8 mm) in
length, with head short, eyes large, prominent laterally, abdomen relatively wide, moderately ﬂator weakly convex dorsally. Body black, moderately shining; labrum black; antennae with basal 1
or 2 segments black, remaining segments dark red; legs dark red to black. Head with a pair of
longitudinal depressions; punctures round, sparse, distinct. Pronotum with surface weakly
uneven; punctures round, very dense, distinct. Elytra with surface weakly uneven; puncturesround, dense to very dense, distinct. Legs moderately long; tarsi with 4th tarsomere simple.
Abdomen weakly narrowed posteriorly; 9th tergum (Fig. 74A) posteriorly with cleaning comb
relatively short; punctures sparse to moderately dense, small and distinct in anterior segments,
while punctures in posterior segments a little smaller and shallower than in anterior segments.
Lateroventrites ventromesial in position, wide to very wide, each with a large, elongate depression which almost occupies the anterior 2/3, sparsely punctate in posterior 1/3.
Male: Legs with femora thick; 6th ventrite (Fig. 74A) with a shallow, bell-shaped depression,
which is very shallowly emarginate; 7th ventrite (Fig. 74A) posteromedially with a very shallow,
bell-shaped depression; 8th ventrite (Fig. 74E) posteromedially with a V-shaped emargination;
9th tergum (Fig. 74A) with anterolateral ﬂaps, ventral apophyses thin, very long; 9th ventrite(Fig. 74F) elongate, very ﬁnely serrate posteriorly, rounded apicolaterally, with stem rounded
anteriorly, macrosetae paired, apicolateral setae short; 10th tergum (Fig. 74A) entire. Aedeagal
median lobe (Fig. 74C) elongate-ovoidal in shape, with apical sclerotized area elongate-triangular, with the apicalmost globe very small. Endophallic median longitudinal bands (Fig. 74C) distinctly diverging anteriorly, each anterolaterally with an ovoidal sclerotized area; expulsion
hooks (Fig. 74C) widely separated, each very small, with anterior plate shorter than posterior
plate; basal tube (Fig. 74C) very large, long, with tube body baculiform, consisting of basal andapical rods which are partially articulated (Fig. 74B); inner sac wholly enveloped the basal tube,
covered densely with very small spicules (Fig. 74C). Parameres (Fig. 74C) very thin; apical area
short, distinctly swollen mesially, furnished mesially with 9 to 10 short setae.
Female: Legs with femora thinner than in male; 8th ventrite rounded posteriorly; gonocoxites(Fig. 74D) each irregularly serrate posteriorly, rounded apicolaterally, with a blunt apicomesial
tooth, apicolateral setae long; spermatheca not observable.
Biology and Ecology. Stenus nomurai is distributed in the mountainous regions. The beetles
inhabit the vicinity of mountain streams; and they are found on and near the stones and mosses
near there.
Remarks. Stenus nomurai was ﬁrst described as a new species from Hokkaido, Japan by
Naomi (1988c); and after that, Naomi & Puthz (1994a) synonymized Stenus nomurai with S.
mikado Hromádka, 1979. However, S. nomurai is obviously different from the latter in structureof the apical part of aedeagal median lobe as well as the structures of endophallic elements(including basal tube, expulsion hooks and median longitudinal bands). Therefore, the name Stenus nomurai (Naomi: 1988) is here resurrected from a subjective junior synonym of S. mikado(Hromádka: 1979).
S. nomurai is allied to S. latissimus Bernhauer, 1938, but this species is separable from thelatter by the body smaller in length, 9th ventrite of male shallowly emarginate posteriorly (Fig.
74F), the aedeagal median lobe with apical sclerotized area elongate-triangular in shape, with theapicalmost globe smaller (Fig. 74C), and the endophallic basal tube distinctly longer and thicker(Fig. 74B). Among the Japanese members of this group, S. nomurai is allied to S. varicosus, but
it is separable from the latter by the endophallic median longitudinal bands in situ separated (Fig.
74C), the expulsion hook with anterior plate shorter than posterior plate (Fig. 74C) and the basal

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191

tube distinctly longer and thicker (Fig. 74B).
Etymology. The speciﬁc epithet of this species is named after the second author Shûhei
Nomura.
Stenus varicosus Naomi, Nomura & Puthz sp. nov.
(Figs. 75A–F, 132C)
Type material examined. Holotype, ♂ (No. NSMT-I-C-200320 in NMNST), Onzui Valley,
Hyogo Pref., 6. vi. 1984, S. Nomura leg. Paratype 1 ♂ (cN), same data as holotype.
Distribution. Japan (Honshu: Hyogo Pref.).
Redescription. Male: Macropterous; body 3.5 mm (fore body 1.8 mm) in length, with head
short, eyes large, prominent laterally, abdomen relatively wide, weakly convex dorsally. Body
black, moderately shining; labrum black; antennae and legs dark red to black. Head with a pair of
longitudinal depressions; punctures round, sparse to moderately dense, distinct. Pronotum withsurface weakly uneven; punctures round, very dense, distinct. Elytra with surface weakly
uneven; punctures round, dense to very dense, distinct. Legs moderately long; femora thick; tarsi
with 4th tarsomere simple. Abdomen weakly narrowed posteriorly; 9th tergum (Fig. 75D) posteriorly with cleaning comb relatively short; punctures moderately dense to dense, small and distinct in anterior segments, while punctures in posterior segments moderately dense to dense, veryﬁne and regular. Lateroventrites ventromesial in position, wide to very wide, each similarly modiﬁed and punctate as in S. nomurai.
Sixth ventrite (Fig. 75C) posteromedially with a shallow, bell-shaped depression, which isshallowly emarginate posteriorly; 7th ventrite (Fig. 75C) posteromedially with a bell-shaped, ﬂatarea, which is very shallowly emarginate posteriorly; 8th ventrite (Fig. 75C) posteromediallywith a V-shaped emargination; 9th tergum (Fig. 75D) with ventral apophyses thin, very long; 9th
ventrite (Fig. 75A) relatively wide, rounded apicolaterally, very ﬁnely serrate posteriorly, withstem elongate, basilateral emarginations deep, narrow, with macrosetae paired, apicolateral setae
short; 10th tergum (Fig. 75D) entire. Aedeagal median lobe (Fig. 75B) elongate-ovoidal in shape,with apical sclerotized area elongate-triangular, with the apicalmost globe very small. Endophallic median longitudinal bands (Fig. 75B, E) contiguous in basal 2/3, distinctly diverging anteriorly before the middle, each acutely pointed at anterior tip; expulsion hooks (Fig. 75B) widely
separated, each very thin, with anterior plate about as long as posterior plate; basal tube (Fig.
75B) very large, long, with tube body baculiform, thick basally, very thin and subulate apically,
with a very long, separated sclerotized lobe existing right to the tube body, weakly turning rightapically (Fig. 75F); inner sac wholly enveloped the basal tube, and covered with very ﬁne spicules (Fig. 75B). Parameres (Fig. 75B) very thin; apical area short, swollen mesially, furnishedmesially with 8 to 9 setae.
Female: Unknown.
Biology and Ecology. Stenus varicosus is presently known only from the mountainous regionin Hyogo, Honshu. The beetles inhabit the vicinity of mountain streams; and they are found on
and near the stones and mosses near there.
Remarks. Stenus varicosus is allied to S. nomurai, but this new species is separable from thelatter by the endophallic median longitudinal bands in situ contiguous in basal 2/3 (Fig. 75B), theexpulsion hook with anterior plate about as long as posterior plate (Fig. 75B), and basal tube
shorter and thinner (Fig. 75F).
Etymology. The speciﬁc epithet of this species is derived from the Latin adjective “varico-

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Fig. 75. Stenus varicosus Naomi, Nomura & Puthz (Onzui, Hyogo). A, 9th ventrite of male; B, aedeagus; C, 6th
to 8th ventrites of male; D, 9th and 10th terga of male; E, endophallic expulsion hook; F, basal tube. Scale 1:
0.2 mm for A, F, 0.1 mm for E; scale 2: 0.2 mm for B, D; scale 3: 0.3 mm for C.

sus”, which means “dilated”; and the endophallic median longitudinal bands are obviously dilated
anteriorly before the middle (Fig. 75E).

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193

Stenus mikado Hromádka(Figs. 76A–J, 132D)
Stenus mikado Hromádka, 1979a: 117; Herman, 2001: 2285; Naomi & Puthz, 2013: 139.
Stenus nomurai Naomi, 1988c: 46, ﬁg. 1B (partim).
Stenus abbreviatus Naomi, 2015a: 217. New synonym.
Type material. Holotype of S. mikado: ♂ (cH), Sendai, Oschiu, Japan, 28. x. 1955, Yosio
Higo leg. Paratype of S. mikado: ♂ (cP), same data as holotype [examined by Puthz]. Holotype
of S. abbreviatus: ♂ (EUMJ), Omogo, Ehime Pref., Shikoku, 30. iii. 1957, F. Takechi leg. Paratypes of S. abbreviatus: 1 ♂ (cN), Takada, Shingu City, Wakayama Pref., 10. viii. 1991, I. Matoba
leg.; 1 ♂ (cN), Sandankyo, Hiroshima Pref., 1. vi. 1986, I. Okamoto leg.; 1 ♀ (cN), same locality,
19. vii. 1986, I. Okamoto leg.; 1 ♂1 ♀ (cN), Riv. Katsuura, Tonogouchi, Kamikatsu, Tokushima
Pref., 6. v. 1996, M. Yoshida leg.; 1 ♀ (cN), Mt. Shiraga, Kumamoto Pref., 18. iv. 1982, I.
Ohtsuka leg.
Other material examined. [HONSHU]: 1 ♂, Mt. Mitake, Oume City, Tokyo Metropolis, 26.
vi. 1977, M. Tao leg.; 2 ♂, Gozaisho Spa, Mt. Houo, Yamanashi Pref., 16. iv. 1989, K. Hosoda
leg.; 3 ♂1 ♀, Usokkozawa-goya, Shizuoka City, Shizuoka Pref., 9. x. 1991, H. Kojima leg.; 1 ♀,Abe River, Suruga-ku, Shizuoka City, Shizuoka Pref., 15. vii. 2007, T. Shimada leg.; [NANSEIISLS.]: 1 ♂, Miyanoura, Yaku Is., Kagoshima Pref., 29. iv. 1984, M. Yasui leg.; 1 ♂4 ♀, Kawauchi River, Uken-son, Amami Is., Kagoshima Pref., 4. v. 1987, S. Nomura leg.; 1 ♂1 ♀, Hatsuno,
Amami Is., Kagoshima Pref., 4. iv. 1966, H. Nomura leg.; 1 ♂, Maruhata, Amami Is., Kagoshima
Pref., 17. vi. 1980, S. Imasaka leg.
Distribution. Japan (Honshu, Shikoku, Kyushu, Nansei Isls.).
Redescription. Male and female: Macropterous; body 3.7–3.8 mm (fore body 1.7–1.8 mm) in
length, with head short, eyes large, prominent laterally, abdomen relatively wide, moderately ﬂator weakly convex dorsally. Body black, moderately shining; labrum black; antennae with basal
segments black, apical segments dark red; legs black except for dark reddish tarsi. Head weakly
concave between eyes, with a pair of longitudinal depressions; punctures round, dense, various in
size, distinct. Pronotum with surface smooth; punctures round, very dense, regular, distinct. Elytra with surface smooth, similarly punctate as on pronotum. Legs relatively short; tarsi with 4thtarsomere simple. Abdomen weakly narrowed posteriorly; 9th tergum (Fig. 76A) posteriorly withcleaning comb relatively short; punctures various in shape, moderately dense, small and distinct
in anterior segments, while punctures in posterior segments round, moderately dense, small andregular. Lateroventrites ventromesial in position, wide to very wide, each similarly modiﬁed andpunctate as in S. nomurai.
Male: Legs with femora thick; 6th and 7th ventrites each posteromedially with a very shallow emargination; 8th ventrite (Fig. 76J) posteromedially with a V-shaped emargination; 9th tergum (Fig. 76A) with ventral apophyses thin, very long; 9th ventrite (Fig. 76B) elongate, projecting laterally at base, rounded apicolaterally, very ﬁnely serrate posteriorly, with stem elongate,
almost rounded apically, macrosetae paired, apicolateral setae short; 10th tergum (Fig. 76A)
entire. Aedeagal median lobe (Fig. 76C) bulbous basally, and then gradually becoming narrower
apically toward the very acutely pointed apex; apical sclerotized area elongate-triangular inshape, impressed laterally. Endophallic median longitudinal bands (Fig. 76C) short, very thin,each distinctly curved laterally; expulsion hooks (Fig. 76C) separated, each medium-sized, withanterior plate about as long as posterior plate; basal tube with basal room almost spherical, sub-

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Fig. 76. Stenus mikado Hromádka (A, B, J, Takada, Wakayama; C, Omogo, Ehime; D, Katsuura, Tokushima; E,
G, H, Gozaishi, Yamanashi; F, Sendai, Miyagi; I, Sandankyo). A, 9th and 10th terga of male; B, 9th ventriteof male; C, aedeagus; D, gonocoxite; E, F, endophallic basal tube, with inner sac; G–I, basal tube; J, apex of
8th ventrite of male. Scale 1: 0.2 mm for A, B, E–I, 0.1 mm for D; scale 2: 0.1 mm for C, J.

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195

membranous (Fig. 76E), tube body baculiform but its basal area various in structure (simply narrowed to weakly swollen; Fig. 76C, E–I); inner sac (Fig. 76C, E, F) developed, covered denselywith spinules, with its apical part bent left from the ventral side to dorsal direction. Parameres(Fig. 76C) very thin, each weakly curved laterally near the middle; apical area short, weakly
swollen mesially, furnished mesially with 5 to 6 setae.
Female: Legs with femora thinner than in male; 8th ventrite rounded posteriorly; gonocoxites(Fig. 76D) each very ﬁnely serrate both posteriorly and mesially, angulate apicomesially (with avery small tooth), rounded apicolaterally, with apicolateral setae very long.
Biology and Ecology. Stenus mikado is widely distributed in the low and high mountainous
regions from Honshu through Shikoku and Kyushu to Nansei Isls. The beetles inhabit the vicinity of mountain streams and the grasses grown near there; and they are found in the moist littersor mosses, and near or under stones there.
Remarks. Hromádka (1979a) ﬁrst described Stenus mikado from Honshu (Tohoku district),
Japan; and after that, Naomi (2015a) described S. abbreviatus from Honshu (Kinki and Chugoku
districts), Shikoku and Kyushu, Japan. During the course of this study, we examined the holotypes of S. mikado and S. abbreviatus; and we conﬁrmed that S. abbreviatus is conspeciﬁc with
S. mikado, given that they show the same structure of aedeagal median lobe and endophallus(i.e., holotype of S. abbreviatus: Fig. 76C; and holotype of S. mikado; Fig. 76F). Thus, S. abbreviatus is herein newly synonymized with S. mikado.
All specimens of the various populations examined share basically common structures not
only of the body, the aedeagal median lobe and parameres, and also of the endophallic expulsion
hooks and median longitudinal bands. On the other hand, structures of the inner sac (e.g., Fig.
76F: Miyagi: Sendai; Fig. 76E: Yamanashi: Gozaishi; Fig. 76C: Ehime, Omogo) and endophallic
basal tube (e.g., Fig. 76C: Ehime, Omogo; Fig. 76G, H: Yamanashi, Gozaishi; Fig. 76I, Hiroshima, Sandankyo) more or less vary from one local population to another. No distinct morphological gaps are, however, found among those local populations with respect to these two characters. This means that even if we ﬁnd two or more seemingly different forms of these characters,
there exist intermediate conditions between those different forms of the character in question.
Therefore, we here consider the variations to be infraspeciﬁc with respect to the structures of
inner sac and endophallic basal tube.
S. mikado is allied to S. nomurai and S. varicosus, but this species is separable from the lattertwo species by the apical sclerotized area of aedeagal median lobe with paired longitudinal
impressions, and without the apicalmost globe (Fig. 76C), the endophallic median longitudinalbands much thinner (Fig. 76C), the expulsion hooks wider (Fig. 76C), the basal tube much
shorter and thinner (Fig. 76F-H) and the inner sac more densely covered with spinules throughout, with its apical part bent left from the ventral side to dorsal direction (Fig. 76C).
Etymology. The speciﬁc epithet of this species is named after the Japanese term “Mikado”.
Stenus pudefactus Ryvkin(Figs. 77A–F, 132E)
Stenus pudefactus Ryvkin, 1987a: 124; Herman, 2001: 2357; Puthz, 2009a: 38; Naomi & Puthz,
2013: 139.
Type material. Holotype: ♂ (ZIRAS), type locality: Kunashir Is., Russia.
Other material examined. [HOKKAIDO]: 1 ♂, Shikaribetsu, Kamishihoro, 13. vii. 1992, T.

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Fig. 77. Stenus pudefactus Ryvkin (A, D, Saruru, Hokkaido; B, C, E, F, Shikaribetsu, Hokkaido). A, spermatheca; B, 9th and 10th terga of male; C, aedeagus; D, apex of gonocoxite; E, 9th ventrite of male; F, 7th to 8th
ventrites of male. Scale 1: 0.1 mm for A, D, 0.2 mm for B, C, E; scale 2: 0.3 mm for F.

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Watanabe leg.; 1 ♂, Sapporo Lake, Sapporo City, 28. vii. 1994, T. Kishimoto leg.; 1 ♂, Saruru
River, Erimo-cho, 9. ix. 1994, K. Miyashita leg.; 1 ♀, same locality, 10. ix. 1994, K. Miyashita
leg.; 1 ♀, Hirayama, Engaru, Monbetsu, 6. vii. 2013, T. Watanabe leg.; 2 ♂, Mt. Chiroro, Hidakacho, 10. vii. 1992, K. Haga leg.
Distribution. Japan (Hokkaido); Russia.
Redescription. Male and female: Macropterous; body 3.9–4.1 mm (fore body 1.8–1.9 mm) in
length, with antennae short. Body and its appendages entirely black, moderately shining. Headhardly concave dorsally, with a pair of longitudinal depressions between eyes, median part ofvertex distinctly higher in level than inner margin of eyes; punctures round, dense to very dense,
distinct. Pronotum with surface weakly impressed on basal 1/3; punctures round, very dense, regular, distinct, interstices between punctures distinctly miscrosculptured. Elytra with surface
weakly impressed around the suture in about basal 1/2, similarly punctate as on pronotum butpunctures a little larger than on pronotum, interstices between distinctly miscrosculptured. Legs
moderately long; tarsi with 4th tarsomere simple. Abdomen subparallel-sided or weakly narrowed posteriorly; punctures moderately dense, small and somewhat irregular in anterior segments, while punctures in posterior segments dense, small and regular. Lateroventrites ventromesial or horizontal in position, moderately wide to wide, densely punctate.
Male: Seventh ventrite (Fig. 77F) shallowly emarginate posteromedially; 8th ventrite (Fig.
77F) posteromedially with a V-shaped emargination; 9th tergum (Fig. 77B) with ventral apophyses thin, long; 9th ventrite (Fig. 77E) elongate, rounded apicolaterally, bi-emarginate posteriorly,
with stem elongate-triangular in shape, macrosetae paired, apicolateral setae short; 10th tergum(Fig. 77B) entire. Aedeagal median lobe (Fig. 77C) elongate, weakly narrowed apically behindthe middle (so that the apical sclerotized area is still wide), and rounded or weakly obtuse apicomedially. Endophallic median longitudinal bands (Fig. 77C) long, thin, running almost in parallel; lateral longitudinal bands (Fig. 77C) very thin; expulsion hooks (Fig. 77C) separated, divergent posteriorly, each thin, laterally with a small notch at the middle; basal tube (Fig. 77C) withbasal room small, globous, tube body slender, attenuate, and once curved right near apical 1/3.
Parameres (Fig. 77C) stout, thick, each very strongly incurved apically to form the ladle-shaped
apex, which is very strongly sclerotized, with 4-5 short setae.
Female: Eighth ventrite rounded posteriorly; gonocoxites (Fig. 77D) each almost roundedapicolaterally, with apicomesial tooth large, acutely pointed, apicolateral setae very long. Spermatheca (Fig. 77A) with two distinct turns; capsule very small; RT-duct thick, straight; spermathecal duct submembranous from the base to 1st turn; basal valve medium-sized; basal pouch
large, almost cone-shaped; spermathecal gland elongate-spherical in shape, with its opening
located mesially on the tube between 1st and 2nd turns.
Biology and Ecology. Stenus pudefactus is distributed in the low and high mountainous
regions in Japan. The beetles inhabit the shores of rivers, lakes and marshes and the grasses
grown near there; and they are found in moist litters or mosses, and near or under moist stones
there.
Remarks. Stenus pudefactus was ﬁrst recorded from Hokkaido, Japan by Puthz (2009a). S.
pudefactus is considered the sister species of S. miyama, but this species is separable from thelatter by the 7th ventrite of male modiﬁed only by a shallow, posteromedian emargination (Fig.
77F), the aedeagal median lobe wider at apex (Fig. 77C), the endophallic expulsion hook muchlarger and elongate (Fig. 77C), and the paramere more strongly incurved and sclerotized apically,
with 4 to 5 short setae (Fig. 77C).

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Stenus miyama Naomi(Figs. 78A–F, 132F)
Stenus miyama Naomi, 1988c: 47; Puthz, 2009a: 37; Naomi & Puthz, 2013: 139.
Stenus pudefactus Ryvkin, 1987a: Puthz, 1991b: 105.
Type material examined. Holotype: ♂ (KUF), Marunuma, Oku-nikko, Tochigi Pref., 4–5. vii.
1982, S. Naomi leg. Paratype: 2 ♀ (cN), Same data as holotype; 1 ♂1 ♀ (cN), Toubaku-zawa,Oku-chichibu, Saitama Pref., 5. vi. 1986, K. Nemoto leg.; 1 ♂ (cN), Kaminikkawa Pass, Mt. Daibosatsu, Yamanashi Pref., 15–18. vii. 1982, S. Naomi leg.
Other material examined. [HONSHU]: 1 ♀, Mt. Zaou, Miyagi Pref., 22-25. viii. 1978, M.
Sato leg.; 1 ♂2 ♀, Mt. Tashiro, Tateiwa-mura, Fukushima Pref., 24. vii. 1996, S. Naomi leg.; 1 ♂,Mt. Ohdai, Nara Pref. (Yamato), 26. viii. 1979, M. Yasui leg.
Distribution. Japan (Honshu).
Redescription. Male and female: Macropterous; body 3.5–4.1 mm (fore body 1.8–2.1 mm) in
length, covered with silvery-white, short setae, antennae short, relatively thick. Body black,weakly shining; labrum black; antennae 1 or 2 basal segments black, remaining segments dark
red; legs black except for dark red tarsi. Head hardly concave dorsally, with a pair of longitudinal
depressions between eyes; punctures round, very dense, distinct. Pronotum with surface shallowly impressed on basal 1/3; punctures round to elliptical, very dense, distinct, interstices
between punctures miscrosculptured. Elytra with surface weakly impressed around the suture in
about basal 1/2, similarly punctate as on pronotum, interstices between punctures miscrosculptured. Legs moderately long; tarsi with 4th tarsomere simple. Abdomen weakly narrowed posteriorly; punctures sparse to moderately dense and small throughout. Lateroventrites ventromesial
or horizontal in position, moderately wide to wide, densely punctate.
Male: Seventh ventrite (Fig. 78D) posteromedially with a wide-subtriangular ﬂat area, whichis shallowly emarginate; 8th ventrite (Fig. 78D) posteromedially with a V-shaped emargination;
9th tergum (Fig. 78E) with ventral apophyses long, straight; 9th ventrite (Fig. 78B) elongate,
almost rounded or obtusely angulate apicolaterally, bi-emarginate posteriorly, with stem subrectangular, macrosetae paired, apicolateral setae moderately long; 10th tergum (Fig. 78E) entire.
Aedeagal median lobe (Fig. 78C) elongate, weakly narrowed apically, obtusely pointed apically,
with ventrolateral rims thick. Endophallic median longitudinal bands (Fig. 78C) long, thin, running almost in parallel; lateral longitudinal bands (Fig. 78C) very thin; expulsion hooks (Fig.
78C) separated, each very small, gingko-shaped; basal tube (Fig. 78C) with basal room globous,
tube body slender, attenuate but bi-sinuous. Parameres (Fig. 78C) stout, thick, strongly incurved
apically to form the ladle-shaped apex, which is moderately sclerotized, with 7 to 8 short setae.
Female: Eighth ventrite rounded posteriorly; gonocoxites (Fig. 78F) each rounded apicolaterally, with apicomesial tooth, apicolateral setae of various length (moderately long to very long).
Spermatheca (Fig. 78A) stout, with two turns; capsule very small; RT-duct very thick; spermathecal duct submembranous behind the middle of duct between 1st and 2nd turns; basal valve
relatively short; basal pouch large, bell-shaped; spermathecal gland almost spherical, with its
opening located mesially on the tube between 1st and 2nd turns.
Biology and Ecology. Stenus miyama is distributed in the high mountainous regions in Honshu. The beetles inhabit the vicinity of mountain streams; and they are found in the moist littersor mosses, and near or under moist stones there.
Remarks. Stenus miyama was ﬁrst described from Honshu, Japan by Naomi (1988c). Puthz

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Fig. 78. Stenus miyama Naomi (A, F, Tashiro, Fukushima; B–E, Tobaku-zawa, Saitama). A, spermatheca; B, 9th
ventrite of male; C, aedeagus; D, 7th to 8th ventrites of male; E, 9th and 10th terga of male; F, apex of gonocoxite. Scale 1: 0.1 mm for A, F, 0.2 mm for B, C, E; scale 2: 0.3 mm for D.

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Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz(1991b) synonymized this species with S. pudefactus Ryvkin, 1987a; and after that, Puthz(2009a) resurrected this species as a valid species. S. miyama is closely allied to S. pudefactus,
but this species is separable from the latter by the 7th ventrite of male posteromedially with awide-subtriangular ﬂat area, which is shallowly emarginate posteriorly (Fig. 78D), the aedeagal
median lobe narrower apically (Fig. 78C), the endophallic expulsion hook very small and ginkoshaped (Fig. 78C), and the paramere less strongly incurved and sclerotied apically, with 7 to 8
short setae (Fig. 78C).
Etymology. The speciﬁc epithet of this species is derived from the Japanese term “miyama”,
which means “mountainous regions” where this species is distributed.
Species group of S. crassus StephensS. crassus group consists of 5 species in Japan; see Puthz (1968a, 2006a) and Ryvkin (2011)
regarding reviews and characterization of this group; and see Puthz (1968a) regarding a key to
the Palearctic species of this group. Diagnostic characters are as follows: Legs with 4th tarsomere simple; abdomen with 4 short basi-longitudinal keels on terga; lateroventrites missing in
4th to 6th segments; 9th ventrite of male basically with apicolateral teeth pointed, hook-shaped(or incurved) (Fig. 79B); aedeagal median lobe various in shape (Figs. 79A, 81A; see also Puthz,
1968a, 2006a); endophallic expulsion hook medium-sized to large, almost H-shaped (Fig. 80E),
M-shaped (Puthz, 2006a, ﬁg. 9), etc.; gonocoxite with apicolateral tooth (Fig. 79F); spermathecastrongly sclerotized, with its duct thick to extremely thick (Fig. 79E).
Key to the Japanese species of S. crassus group1(6) Body sparsely covered with short setae (Fig. 132G).
2(3) Aedeagal median lobe wider apically, not constricted apicolaterally, with its apical sclerotized area subpentagonal in shape (Fig. 79A) .....................................S. immarginatus Mäklin
3(2) Aedeagal median lobe narrower apically, more or less constricted near the apex, with its apical sclerotized area pentagonal in shape.
4(5) Aedeagal median lobe with apical sclerotized area shorter (Fig. 80G); spermatheca with its
gland opened simply on the surface of duct (Fig. 80C) .......................... S. tomitaorum Naomi
5(4) Aedeagal median lobe with its apical sclerotized area longer (Fig. 83A); spermatheca with
its gland opened on a large tubercle projected from the duct (Fig. 83B) ........ S. ﬁnalis Ryvkin6(1) Body densely covered with moderately long or long setae (Fig. 132J).
7(8) Body covered entirely with very thin, long and suberect setae, with the longest setae almost
equal in length to the 1st to 3rd antennal segments taken together; aedeagal median lobe feebly constricted at the base of apical sclerotized area (Fig. 81A); endophallic basal tube
shorter, thicker, straight (Fig. 81A) ........................................................... S. hirtiventris Sharp
8(7) Body covered entirely with thin, moderately long, and declinate setae, with the longest setae
almost equal in length to the 1st and 2nd antennal segments taken together; aedeagal median
lobe slightly but distinctly constricted at the base of apical sclerotized area (Fig. 82A); endophallic basal tube longer, thinner, with the curved apex (Fig. 82A) ..........................................
.......................................................................................................... S. pilosiventris Bernhauer

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Stenus immarginatus Mäklin
(Figs. 79A–F, 132G)
Stenus immarginatus Mäklin, 1853: 192; Naomi, 1998a: 103; Herman, 2001: 2223; Naomi &Puthz, 2013: 139.
Type material examined. Syntypes: 2 ♀ (ZMH), type locality: Kadjak [examined by Puthz in1967].
Other material examined. [HOKKAIDO]: 1 ♀, Mt. Teshio, Asahi-cho, 28. vii. 1987, N.
Yasuda leg.; 2 ♀, Sekihoku Pass, Rubeshibe-cho, 24. vii. 2000, S. Nomura leg.; 1 ♀, Kamishihoro, 25. vi. 2008, K. Haga leg.; 1 ♀, Upepe-sanke, Mt. Daisetsu, 9. vii. 2002, N. Yasuda leg.;1 ♀, Ukishima moor, Kamikawa-cho, 24. vii. 2000, S. Nomura leg.
Distribution. Japan (Hokkaido); China, Russia, Canada, USA.
Redescription. Male and female: Macropterous; body 2.1–3.1 mm (fore body 1.2–1.6 mm) in
length, subcylindrical, only sparsely, shortly setous, moderately shining, with antennae short,thick. Body black; labrum black; antennae with 1 or 2 basal segments black, remaining segments
dark red; legs dark red to black. Head small, weakly convex dorsally, with a pair of longitudinal
impressions at sides of median longitudinal swollen area; punctures round to elliptical, dense tovery dense, irregular, distinct. Pronotum with surface weakly uneven; punctures round, dense tovery dense, somewhat irregular. Elytra with surface moderately uneven; punctures round, dense,
almost regular. Legs relatively short; tarsi short, thick, with 4th tarsomere simple. Abdomen narrowed posteriorly; 3rd to 6th terga each with 4 short basi-longitudinal keels; punctures round,sparse to moderately dense, and small to medium-sized in anterior segments, while punctures inposterior segments sparse, very small to small, and somewhat irregular. Third lateroventrite distinct, narrow; 4th to 5th lateroventrites each distinct only at base, fused with the corresponding
ventrite in the remaining posterior part but tergo-ventrite suture distinct; 6th lateroventrite completely fused with the ventrite, tergo-ventrite suture distinct.
Male: Sixth and 7th ventrites (Fig. 79D) each posteromedially with a semicircular ﬂat area;
8th ventrite (Fig. 79D) posteromedially with a shallow, wide emargination; 9th tergum (Fig. 79C)
with ventral apophyses long, almost straight; 9th ventrite (Fig. 79B) wide, irregularly serrate posteriorly, with stem subtrapezoidal in shape, apicolateral teeth short, acutely pointed, apicolateral
setae moderately long; 10th tergum (Fig. 79C) entire. Aedeagal median lobe (Fig. 79A) relatively
wide, almost rounded apicolaterally, obtusely angulate apically; apical sclerotized area subpentagonal in shape, mostly covered with short, sparse setae. Endophallic median longitudinal bands(Fig. 79A) long, diverging anteriorly; lateral longitudinal bands (Fig. 79A) very short; expulsion
hooks (Fig. 79A) large, connected by a transverse rod to form an almost H-shaped structure, eachwith posterior plate larger than, and distinctly demarcated by transverse suture from, anterior
plate; basal tube (Fig. 79A) with basal room ovoidal, tube body rod-like, once weakly constricted
near the middle, with strongly curved apex. Parameres (Fig. 79A) almost straight; apical area
long, hardly swollen mesially, and furnished mesially with 14 to 15 setae.
Female: Abdomen distinctly wider than in male; 8th ventrite posteromedially obtuse; gonocoxites (Fig. 79F) each apicomesially angulate, with apicolateral tooth short, acutely pointed.
Spermatheca (Fig. 79E) with capsule almost missing; RT-duct thick, almost straight; spermathecal duct well-sclerotized, coiled with 5 turns, thick but very thick around 3rd turn; basal valve
narrow; basal pouch cone-shaped; spermathecal gland very large, with its opening located at the
3rd turn of the duct.

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Fig. 79. Stenus immarginatus Mäklin (A–D, Ummak, Alaska; E, F, Tesio, Hokkaido). A, aedeagus; B, 9th ventrite of male; C, 9th and 10th terga of male; D, 6th to 8th ventrites of male; E, spermatheca; F, gonocoxite.
Scale 1: 0.1 mm for A, B; scale 2: 0.2 mm for C, 0.1 mm for E, F; scale 3: 0.3 mm for D.

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Biology and Ecology. Stenus immarginatus is distributed in the plains, low and high mountainous regions in Hokkaido. No solid data are obtained for the habitats of this species, but thecollecting records suggest that the beetles inhabit moist litters of the shores of the rivers, lakes
and marshes as well as leaf litter near there.
Remarks. Stenus immarginatus was ﬁrst discovered from Japan (Hokkaido) by Naomi(1998a). This species is allied to S. formicetorum Mannerheim, 1843 and S. transbaicalicus
Bernhauer, 1900, but it is separable from them by the body larger (2.1–3.1 mm) and wider, andthe aedeagal median lobe distinctly wider apically (Fig. 72A). Among the Japanese members of
this group, S. immarginatus is similar to S. tomitaorum and S. ﬁnalis, but this species is separablefrom the latter two species by the aedeagal median lobe wider apically, and not constricted near
the apex, with its apical sclerotized area subpentagonal in shape (Fig. 79A).
Stenus tomitaorum Naomi(Figs. 80A–H, 132H)
Stenus tomitaorum Naomi, 1989a: 38; Herman, 2001: 2418; Naomi & Puthz, 2013: 139.
Type material examined. Holotype: ♂ (KUF), Kami-shunbetsu, 20. vii. 1977, S. Naomi leg.
Paratypes: 4 ♂1 ♀ (cN), same data as holotype; 2 ♂ (cN), Nemuro-shibetsu, 18. vii. 1977, S.
Naomi leg.
Other material examined. [HOKKAIDO]: 1 ♀, Ohtsu, Toyokoro-cho, 27. v. 1990, K. Haga
leg.; 1 ♀, mouth of Tokachi river, 23. v. 1993, K. Shibata leg.; 1 ♀, Onʼnenai Tsurui, Kushiro
Marsh, 27. viii. 1990, M. Sakai leg.; 1 ♀, Akanuma, Kushiro Marsh, 28. viii. 1990, M. Sakai leg.;1 ♀, same locality and date, M. Sato leg.
Distribution. Japan (Hokkaido).
Redescription. Male and female: Macropterous; body 2.5–3.0 mm (fore body 1.4–1.6 mm) in
length, subcylindrical, only sparsely, shortly setous, moderately shining, with antennae short,thick. Body black; labrum black; antennae and legs dark red to black. Head weakly convex dorsally, with a pair of shallow longitudinal depressions; punctures round to elliptical, dense, various in size (including large ones), irregular, sometimes two or more punctures fused to form avery large one. Pronotum with surface vaguely impressed posteromedially; punctures round, very
dense, almost regular. Elytra with surface impressed on basal 1/2 near the suture; puncturesround, very dense, almost regular. Legs relatively short; tarsi short, with 4th tarsomere simple.
Abdomen narrowed posteriorly; 3rd to 6th terga each with 4 short basi-longitudinal keels; punctures round to elliptical, sparse to moderately dense, small and irregular in anterior segments,
while punctures in posterior segments sparse to moderately dense, very small to small, and somewhat irregular. Third lateroventrite distinct, narrow, narrowed posteriorly; 4th to 6th lateroventrites each distinct only about at basal 1/2, fused with the corresponding ventrite in the remaining
posterior part, but tergo-ventrite suture distinct.
Male: Eighth ventrite (Fig. 80D) posteriorly with a shallow, wide emargination; 9th tergum(Fig. 80B) with ventral apophyses moderately long; 9th ventrite (Fig. 80A) wide, weakly arcuate
posteriorly, indistinctly serrate at posterior margin, with stem wide, rounded anteriorly, apicolateral teeth incurved, acutely pointed, apicolateral setae long; 10th tergum (Fig. 80B) subhexagonal in shape. Aedeagal median lobe (Fig. 80G) elongate, weakly constricted at the base of apicalsclerotized area, and obtusely angulate apically; apical sclerotized area pentagonal in shape, distinctly demarcated by a transverse suture from the rest of median lobe, covered with very short,204

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Fig. 80. Stenus tomitaorum Naomi (A, B, D, E, G, H, Kamishunbetsu, Hokkaido; C, F, Toyokoro, Hokkaido). A,
9th ventrite of male; B, 9th and 10th terga of male; C, spermatheca; D, apical part of 8th ventrite of male; E,
endophallic expulsion hook; F, gonocoxite; G, aedeagus; H, basal tube. Scale 1: 0.1 mm for A, C, F, H, 0.05
mm for E; scale 2: 0.1 mm for B, G; scale 3: 0.3 mm for D.

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205

setae on apical 1/2, and also furnished laterally with 5 to 6 short setae. Endophallic median longitudinal bands (Fig. 80G) with ventral bands long, dorsal bands moderately long, diverging anteriorly; expulsion hooks (Fig. 80G) connected by a transverse rod to form an almost H-shaped
structure, each with posterior plate distinctly demarcated by a transverse suture from anterior
plate, acutely pointed (Fig. 80E); basal tube (Fig. 80G) with basal room ovoidal, tube body rodlike, moderately thick, constricted near the middle, with strongly curved apex (Fig. 80H). Parameres (Fig. 80G) slender, almost straight; apical area long, hardly swollen mesially, and furnished mesially with 6 to 7 sparse setae.
Female: Eighth ventrite rounded posteriorly; gonocoxites (Fig. 80F) each apicomesiallyangulate, with apicolateral tooth thin, very acute, apicolateral setae moderately long. Spermatheca (Fig. 80C) with capsule very small, subconical; RT-duct thick, almost straight; spermathecal duct well-sclerotized, coiled with 4 turns, thick but extremely thick around 3rd turn; basal
valve narrow, short; basal pouch relatively narrow, subconical; spermathecal gland large, with its
opening located at the anterior surface of 3rd turn of the duct.
Biology and Ecology. Stenus tomitaorum is distributed in the plains and low mountainous
regions in Hokkaido. The beetles inhabit litter in the grasslands, and also moist litter of thegrasses grown at the shores of the rivers, lakes and marshes.
Remarks. Stenus tomitaorum is allied and also very similar in external structure to S. crassus
Stephens, 1833 (Ganglbauer, 1895: 582), but this species is separable from the latter by theaedeagal median lobe with apical sclerotized area a little shorter and more strongly angulate laterally (Fig. 80G). Among the Japanese members of this species group, S. tomitaorum is similarin external character to S. ﬁnalis, but this species is separable from the latter by the aedeagal
median lobe with apical sclerotized area shorter (Fig. 80G), and the spermatheca with its gland
opened on the simple surface of duct (Fig. 80C).
Etymology. The speciﬁc epithet of this species is named after Mr. Tsuneo Tomita and Mrs.
Yukie Tomita, Kumamoto, who have kindheartedly supported the entomological activity of S.-I.
Naomi for very long time from his childhood to the present.
Stenus hirtiventris Sharp(Figs. 81A–F, 132I)
Stenus hirtiventris Sharp, 1889: 328; Herman, 2001: 2214; Naomi & Puthz, 2013: 139.
Type material examined. Holotype: ♀ (NHML), type locality: Niigata, Japan [examined by
Puthz].
Other material examined. [HONSHU]: 1 ♂1 ♀, Tomiyachi, Shariki-mura, Aomori Pref., 30.
ix. 1992, S. Nomura leg.; 1 ♂, Mt. Iwaki, Aomori Pref., 29. ix. 1992, M. Sakai leg.
Distribution. Japan (Honshu: Aomori and Niigata Prefs.); China.
Redescription. Male and female: Macropterous / brachypterous; body 2.5–2.7 mm (fore body
1.3–1.4 mm) in length, subcylindrical, moderately shining, densely covered with very thin, longand suberect setae, with antennae short, thick. Head and abdomen black; pronotum and elytra
dark red; labrum black; antennae and legs reddish brown to dark red. Head weakly convex dorsally, with a pair of shallow longitudinal depressions; punctures round to elliptical, dense to very
dense, distinct. Pronotum with surface smooth or very weakly uneven; punctures round, very
dense, various in size, distinct. Elytra with surface almost smooth; punctures round, very dense,
almost regular. Legs relatively short; tarsi short, with 4th tarsomere simple. Abdomen weakly

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Fig. 81. Stenus hirtiventris Sharp (A, Iwaki, Aomori; B–F, Tomiyachi, Aomori). A, aedeagus; B, spermatheca;
C, 9th ventrite of male; D, gonocoxite; E, 9th and 10th terga of male; F, 7th to 8th ventrites of male. Scale 1:
0.1 mm for A, B, D, 0.2 mm for F; scale 2: 0.1 mm for C, E.

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207

narrowed posteriorly; 3rd to 6th terga each with 4 short basi-longitudinal keels; punctures sparse,
small and irregular in all segments. Lateroventrites existing only in 3rd segment, while tergoventrite sutures only existing in 4th to 6th segments.
Male: Seventh and 8th ventrites (Fig. 81F) each posteromedially with a shallow, wide emargination, but the emargination in the 8th a little deeper than in the 7th; 9th tergum (Fig. 81E)
with ventral apophyses relatively short; 9th ventrite (Fig. 81C) relatively wide, hardly serrate
posteriorly, with stem subtriangular in shape, apicolateral teeth thin, incurved, acute, macrosetae
paired, apicolateral setae long; 10th tergum (Fig. 81E) very ﬁnely serrate and rounded posteriorly. Aedeagal median lobe (Fig. 81A) elongate, feebly constricted at the base of apical sclerotized area, angulate apically; apical sclerotized area pentagonal in shape, distinctly demarcatedby a transverse or arcuate suture from the rest of median lobe, and covered with very short, setae
on apical 2/3. Endophallic median longitudinal bands (Fig. 81A) with ventral bands fused toform a single median band which is strongly sclerotized laterally, dorsal bands longer than theventral band, distinctly diverging anteriorly; expulsion hooks (Fig. 81A) connected by a transverse rod to form an almost H-shaped structure, with posterior plate partially fused with anterior
plate, acutely pointed, anterolaterally with a small, pointed tooth; basal tube (Fig. 81A) moderately thick, short, with basal room ovoidal, tube body baculiform, weakly constricted at base.
Parameres (Fig. 81A) slender, each weakly curved laterally a little before apical area; apical area
very long, hardly swollen mesially, and furnished mesially with 9 to 10 setae.
Female: Eighth ventrite rounded posteriorly; gonocoxites (Fig. 81D) each simply angulateapicomesially, with apicolateral tooth thin, acute. Spermatheca (Fig. 81B) with capsule short,
almost rounded apically; RT-duct thick, relatively long; spermathecal duct well-sclerotized,tightly coiled with 4 turns, thick but very thick around 3rd turn; basal valve rather narrow, long;
basal pouch cone-shaped; spermathecal gland large, spherical, with its opening located at theanterior surface of 3rd turn of the duct.
Biology and Ecology. S. hirtiventris is a very rare Stenus species in Japan; and it is presently
known only from the plains and low mountainous regions of Niigata and Aomori in Japan. No
solid data are obtained for the habitats of this species.
Remarks. Stenus hirtiventris is closely allied to S. pilosiventris, but it is separable from thelatter by the body covered with very thin, long and suberect setae (Fig. 132I), the aedeagal
median lobe only feebly constricted at the base of apical sclerotized area, the apical half of whichis covered with short setae (Fig. 81A), the endophallic basal tube distinctly shorter, thicker andstraight (Fig. 81A), and the basal valve of spermatheca much longer and thinner (Fig. 81B).
Stenus pilosiventris Bernhauer(Figs. 82A–F, 132J)
Stenus pilosiventris Bernhauer, 1915: 70; Herman, 2001: 2340; Naomi & Puthz, 2013: 139.
Stenus hirtiventris Sharp, 1889: Naomi, 1989: 40; Naomi & Takeda, 1991: 12.
Type material examined. Holotype: ♀ (FMC), type locality: Gensan, Korea [examined by
Puthz in 1970].
Other material examined. [HONSHU]: 1 ♂1 ♀, Watarase Marsh, Koga City, Ibaraki Pref.,28. ix. 1996, K. Haga leg.; 1 ♂, Mikuni-bashi, Watarase Marsh, Ibaraki Pref., 13. ix. 1987, K.
Haga leg.; 1 ♂1 ♀, Tajimagahara, Urawa City, Saitama Pref., 28. iv. 1984, K. Nemoto leg.;4 ♂4 ♀, Tone Canal, Nagareyama City, Chiba Pref., 6. iv. 1990, T. Takeda leg.; 3 ♀, Suidobashi,

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Fig. 82. Stenus pilosiventris Bernhauer (A, D, Suidobashi, Chiba; B, C, Sakae, Chiba; E, F, Watarase, Ibaraki).
A, aedeagus; B, spermatheca; C, gonocoxite; D, 7th to 8th ventrites of male; E, 9th and 10th terga of male; F,
9th ventrite of male. Scale 1: 0.1 mm for A–C, 0.2 mm for D; scale 2: 0.1 mm for E, F.

Shonan-machi, Chiba Pref., 10. xii. 1989, T. Takeda leg.; 1 ♂, same locality, 9. i. 1990, T. Takeda
leg.; 2 ♂2 ♀, same locality, 13. iii. 1990, T. Takeda leg.; 1 ♂, Nakaya, Sakae-cho, Chiba Pref., 17.
x. 1989, T. Takeda leg.; 1 ♀, Suga-shinden, Sakae-cho, Chiba Pref., 25. iii. 1990, T. Takeda leg.;2 ♀, Mebuki-Ohashi, Noda City, Chiba Pref., 12. xi. 1989, T. Takeda leg.; 1 ♂, Tomen, Yoro Val-

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ley, Chiba Pref., 22. v. 1990, T. Takeda leg.; 1 ♂, Noborito, Kanagawa Pref., 25. iii. 1978, M. Taoleg.; 1 ♀, Mogami River, Bunsui-cho, Niigata Pref., 22. v. 1996, M. Maruyama leg.; 1 ♀, Mikunicho, Sakai City, Fukui Pref., 8. v. 2010, M. Saito leg.; 1 ♀, Jinbe-cho, Hiroshima Pref., 4. v.
1986, I. Okamoto leg.; 1 ♀, Haigamine, Hiroshima Pref., 7. ix. 1985, I. Okamoto leg.; 1 ♂,Nikyukyo, Hiroshima Pref., 11. ix. 1985, I. Okamoto leg.; 1 ♂, Kurose-cho, Hiroshima Pref., 15.
ii. 1986, I. Okamoto leg. [SHIKOKU]: 3 ♂1 ♀, Shirasaki Lake, Matsuyama City, Ehime Pref.,17. iii. 1991, I. Okamoto leg. [CHINA]: 1 ♀ (cS), China, Gansu, Dalijia Shan, 46 km W Linia,
2980 m, 10. vii. 1994, A. Smetana leg.
Distribution. Japan (Honshu, Shikoku); Korea, China, Mongolia, Russia.
Redescriptions. Male and female: Macropterous; body 2.9–3.3 mm (fore body 1.5–1.7 mm)
in length, subcylindrical, weakly to moderately shining, densely covered with thin, declinate,moderately long setae, with antennae short, thick. Head and abdomen black; pronotum and elytra
dark red; labrum black; antennae and legs reddish brown to dark red. Head weakly convex dorsally, with a pair of shallow longitudinal depressions; punctures round, very dense, distinct. Pronotum with surface smooth or very weakly uneven; punctures round, very dense, distinct. Elytra
with surface almost weakly uneven; punctures round, very dense, distinct. Legs relatively short;tarsi short, with 4th tarsomere simple. Abdomen weakly narrowed posteriorly; 3rd to 6th tergaeach with 4 short basi-longitudinal keels; punctures round to elliptical, moderately dense todense, small and distinct in all segments. Lateroventrites existing only in 3rd segment, whiletergo-ventrite sutures only existing in 4th to 6th segments.
Male: Seventh ventrite (Fig. 82D) posteromedially with a very shallow emargination; 8thventrite (Fig. 82D) posteriorly with a shallow, wide emargination; 9th tergum (Fig. 82E) withventral apophyses relatively long; 9th ventrite (Fig. 82F) wide, weakly arcuate posteriorly, hardly
serrate at posterior margin, with stem elongate-subtrapezoidal in shape, apicolateral teeth thin,incurved, very acute, macrosetae paired, apicolateral setae long; 10th tergum (Fig. 82E) almost
subhexagonal in shape, ﬁnely serrate posteriorly. Aedeagal median lobe (Fig. 82A) elongate,
slightly but distinctly constricted at the base of apical sclerotized area, angulate apically; apicalsclerotized area pentagonal in shape, distinctly demarcated by a transverse or arcuate suture fromthe rest of median lobe, and covered posteriorly with very short setae and also laterally withmoderately long setae. Endophallic median longitudinal bands (Fig. 82A) with ventral bands
fused to form a single median band, dorsal bands wide, longer than the ventral band; expulsion
hooks (Fig. 82A) connected by a transverse rod to form an almost H-shaped structure, with posterior plate almost separated by a narrow submembranous area from and also distinctly larger
than anterior plate, and anterolaterally with a small, pointed tooth; basal tube (Fig. 82A) long,with basal room almost ovoidal, tube body rod-like, swollen near the middle, distinctly curved
apically. Parameres (Fig. 82A) slender, straight; apical area long, hardly swollen mesially, andfurnished mesially with 9 to 10 sparse setae.
Female: Body distinctly wider than in male; 8th ventrite rounded posteriorly; gonocoxites(Fig. 82C) each simply angulate apicomesially, with apicolateral tooth acute. Spermatheca (Fig.
82B) with capsule very small; RT-duct thick, relatively long; spermathecal duct well-sclerotized,tightly coiled with 4 turns, thick but very thick around 3rd turn; basal valve short; basal pouch
well sclerotized, almost cone-shaped; spermathecal gland with its opening located at the anterior
surface of 3rd turn of the duct.
Biology and Ecology. Stenus pilosiventris is distributed in the plains and low mountainous
regions in Japan. The beetles inhabit leaf litter in the grasslands and in the forests near grasslands; and they also inhabit moist litter of the grasses grown at the shores of the rivers, lakes and210

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marshes.
Remarks. Stenus pilosiventris was ﬁrst described from Korea by Bernhauer (1915). It seems
that after that, no coleopterists have formally and also correctly recorded this species from Japan,
because this species has been taxonomically confused with S. hirtiventris (e.g., Naomi, 1989a;
Naomi & Takeda, 1991). Naomi & Puthz (2013) simply enumerated S. pilosiventris in the Catalog of Japanese Staphylinidae, but they did not add its collecting records there. Given this, wehere virtually ﬁrst record S. pilosiventris from Japan.
S. pilosiventris is closely allied to S. hirtiventris, but this species is separable from the latterby the body covered with thin, moderately long, and declinate setae (Fig. 132J); the aedeagal
median lobe slightly but distinctly constricted at the base of apical sclerotized area, which is covered posteriorly with very short setae, and also laterally with moderately long setae (Fig. 82A),
the endophallic basal tube distinctly longer, thinner, and curved apically (Fig. 82A), and the spermatheca with basal valve much shorter and thicker (Fig. 82B).
Stenus ﬁnalis Ryvkin(Figs. 83A–F, 132K)
Stenus ﬁnalis Ryvkin, 2011: 62.
Stenus ﬁnitor Ryvkin, 2011: Naomi & Ito, 2014: 290.
Type material. Holotype: ♂ (ZMMSU), Sakhalin Is., Korsakovskiy, 4. vi. 1990, K. V.
Makarov leg.
Other material examined. [HOKKAIDO]: 1 ♂, Ichani, Shibetsu, Hokkaido, 16. v. 2009, T.
Kato leg.
Distribution. Japan (Hokkaido); Russia.
Redescriptions. Male and female: Brachypterous; body 2.3–2.8 mm (fore body 1.2–1.5 mm)
in length, weakly to moderately shining, only sparsely, shortly setous, with antennae short, thick.
Body black; labrum black; antennae with 1st segment black, remaining segments dark red; legs
reddish brown, with knees more or less infuscate. Head weakly convex dorsally, with a pair ofshallow longitudinal depressions; punctures round to elliptical, very dense, distinct. Pronotumwith surface smooth or very weakly uneven; punctures round, very dense, regular, distinct. Elytra
with surface almost even; punctures round, very dense, regular, distinct. Legs short; tarsi short,thick, with 4th tarsomere short, weakly widened apically. Abdomen weakly narrowed posteriorly; 3rd to 6th terga each with 4 short basi-longitudinal keels; punctures round to elliptical,
sparse to moderately dense, small and distinct in anterior segments, while punctures in posterior
segments elliptical, very ﬁne, shallow and regular. Third lateroventrite distinct, narrow; 4th to 5thlateroventrites each distinct only at base, fused with the corresponding ventrite in the remaining
posterior part, but tergo-ventrite suture distinct; 6th lateroventrite completely fused with the ventrite, tergo-ventrite suture distinct.
Male: Eighth ventrite (Fig. 83D) posteromedially with a shallow emargination; 9th tergum(Fig. 83E) with ventral apophyses relatively long; 9th ventrite (Fig. 83F) relatively wide, hardly
serrate posteriorly, with stem subtrapezoidal in shape, apicolateral teeth thin, incurved, very
acute, macrosetae paired, apicolateral setae long; 10th tergum (Fig. 83E) entire. Aedeagal median
lobe (Fig. 83A) elongate, slightly but distinctly constricted at the base of apical sclerotized area,
pointed apically; apical sclerotized area elongate-pentagonal in shape, mostly demarcated by atransverse suture from the rest of median lobe, and covered with very short setae except for theThe Steninae of Japan Part 1

211

Fig. 83. Stenus ﬁnalis Ryvkin (A, D–F, Ichani, Hokkaido; B, Sakhalin, Russia); S. ﬁnitor Ryvkin (C, Amur, Russia). A, aedeagus; B, C, spermatheca; D, 8th ventrite of male; E, 9th and 10th terga of male; F, 9th ventrite of
male. Scale 1: 0.1 mm for A–C, 0.2 mm for D; scale 2: 0.1 mm for E, F.

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basal part. Endophallic median longitudinal bands (Fig. 83A) with ventral bands fused to form asingle median band, dorsal bands long, wide; expulsion hooks (Fig. 83A) connected by a transverse rod to form an almost H-shaped structure, with posterior plate separated by a suture fromanterior plate, and anterolaterally with a small, pointed tooth; basal tube (Fig. 83A) with basal
room relatively large, ovoidal, tube body rod-like, swollen near the middle, slightly curved apically. Parameres (Fig. 83A) thick; apical area moderately long, swollen mesially at its basal part,and furnished mesially with 15 to 20 setae of various length.
Female: Eighth ventrite rounded posteriorly. Spermatheca (Fig. 83B) with capsule small,rounded apically; RT-duct moderately thick, relatively long; spermathecal duct stout, well-sclerotized, almost tightly coiled with 4 turns, thick but very thick around 3rd turn (at which there is amedium-sized hump laterally); basal valve moderately long, thin; basal pouch almost coneshaped; spermathecal gland opened on a large tubercle projected from the lateral side of 3rd turnof the duct.
Biology and Ecology. Stenus ﬁnalis is considered to be a very rare species in Japan; and it ispresently known only from Shibetsu, Hokkaido in Japan. The beetles inhabit moist litter of thegrasses grown at the shores of marshes. In Sakhalin, the beetles are collected from algae heapedat seashore (Ryvkin, 2011).
Remarks. Stenus ﬁnalis was ﬁrst reported as S. ﬁnitor Ryvkin, 2011 from Japan (Hokkaido)
by Naomi & Ito (2014). However, after our closer re-examination of the Stenus specimen collected from Hokkaido, it was found that it is S. ﬁnalis when judging from the structure of
aedeagus and related characters as illustrated in Fig. 83. Given this, we here virtually ﬁrst record
S. ﬁnalis from Hokkaido, Japan.
S. ﬁnalis is closely allied to S. ﬁnitor, but this species is separable from the latter by the
median longitudinal part of vertex more strongly convex (Ryvkin, 2011), the apical sclerotizedarea of aedeagal median lobe wider and shorter, laterally with denser setae (Fig. 83A), the endophallic expulsion hooks a little more widely separated (Fig. 83A), the parameres distinctly
thicker (Fig. 83A), and the spermatheca with its duct a little thicker especially around its 3rd turn(Fig. 83B) when compared with that of S. ﬁnitor (Fig. 83C). Among the Japanese members of
this group, S. ﬁnalis is similar to S. tomitaorum, but this species is separable from the latter by
the aedeagal median lobe with its apical sclerotized area longer (Fig. 83A), and the spermathecawith its gland opened on a large tubercle projected from the duct (Fig. 83B).
Species group of S. opticus Gravenhorst
S. opticus group consists of 1 species in Japan; see Ryvkin (2002) and Puthz (2006a) regarding the review of this group; and see Ryvkin (2002) regarding a key to the Palaearctic species ofthis group. Diagnostic characters are as follows: Legs with 4th tarsomere simple; abdomen with
4 short basi-longitudinal keels on terga; lateroventrites missing in 4th to 6th segments; 9th ventrite of male with apicolateral tooth hook-shaped, pointed (Fig. 84B); aedeagal median lobe with
(Fig. 84A) or without endophallic expulsion hooks (Puthz, 2006a); gonocoxite with apicolateral
tooth pointed (Fig. 84D); spermatheca not observable.
Stenus strobilus Ryvkin(Figs. 84A–F, 132L)
Stenus strobilus Ryvkin, 2002: 290.

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Fig. 84. Stenus strobilus Ryvkin (Ebetsu, Hokkaido). A, aedeagus; B, 9th ventrite of male; C, 9th and 10th tergaof male; D, apices of gonocoxites; E, apex of 8th ventrite of male; F, 9th and 10th terga of female. Scale 1:
0.1 mm for A, B, D, F; scale 2: 0.1 mm for C; scale 3: 0.3 mm for E.

Stenus nubilus Ryvkin, 2002: Naomi, 1997e: 6.
Type material. Holotype: ♂ (ZIRAS), Kiya River mouth, 15–28. v. 1915, Pavlenko leg.
Other material examined. [HOKKAIDO]: 1 ♂2 ♀, Echigo Pond, Ebetsu City, 29. iv. 1995, K.
Miyashita leg.
Distribution. Japan (Hokkaido); Russia.

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Redescriptions. Male and female: Brachypterous; body 2.3–2.8 mm (fore body 1.2–1.4 mm)
in length, matt, with antennae relatively short. Body black; labrum black; antennae and legs dark
red to black. Head almost ﬂat dorsally, hardly provided with paired longitudinal depressions;punctures round to elliptical, very dense, distinct. Pronotum with surface weakly uneven; punctures round, very dense, regular, distinct. Elytra with surface uneven; punctures round, very
dense, somewhat rough. Legs short; tarsi short, with 4th tarsomere simple. Abdomen weakly narrowed posteriorly; 3rd to 6th terga each with 4 short basi-longitudinal keels; punctures round to
elliptical, sparse to moderately dense, and small in anterior segments, while punctures in posterior segments elliptical, ﬁne and regular, interstices between punctures microsculptured in all
segments. Third lateroventrite distinct, very narrow, narrowed posteriorly; 4th to 6th lateroventrites each completely fused with the corresponding ventrite, tergo-ventrite suture indistinct.
Male: Eighth ventrite (Fig. 84E) posteriorly with a very shallow emargination; 9th tergum(Fig. 84C) with ventral apophyses moderately long and wide; 9th ventrite (Fig. 84B) wide, very
ﬁnely serrate posteriorly, with stem subtrapezoidal in shape, apicolateral teeth thin, incurved,
very acute, macrosetae paired, apicolateral setae long; 10th tergum (Fig. 84E) entire. Aedeagal
median lobe (Fig. 84A) elongate, well sclerotized along the lateral rim, widely rounded apicolaterally, acutely pointed apically; apical sclerotized area moderately long. Endophallic median longitudinal bands (Fig. 84A) with ventral bands very thin, moderately long, dorsal bands long,
diverging anteriorly; expulsion hooks (Fig. 84A) connected each other by the mesial point ofmesially pointed projection, each hook subtriangular, with posterior plate separated by a transverse suture from, and much larger than anterior plate; basal tube (Fig. 84A) with basal room
large, elongate-ovoidal in shape, tube body rather short, thick, with the left, long projection.
Parameres (Fig. 84A) slender, almost straight; apical area weakly swollen mesially, and furnished mesially with 6 to 8 sparse setae.
Female: Eighth ventrite rounded posteriorly; gonocoxites (Fig. 84D) each with apicolateral
tooth thin, incurved and very acute, apicolateral setae moderately long. Spermatheca not observable.
Biology and Ecology. Stenus strobilus is presently known only from Ebetsu, Hokkaido inJapan. The beetles inhabit moist litter of the grasses grown at the shores of pond; and they also
inhabit the river mouth (Ryvkin, 2002).
Remarks. Stenus strobilus was ﬁrst recorded as S. nubulus from Japan (Hokkaido) by Naomi(1997e), but after our closer examination it is S. strobilus as described above. S. strobilus isclosely allied to S. nubilus, but this species is separable from the latter by the elytra along suture
longer than pronotum (Ryvkin, 2002), the aedeagal median lobe narrower in apical 1/3 (Fig.
84A), and the endophallic expulsion hooks connected each other by the mesio-medial corner, andeach subtriangular in shape (Fig. 84A).
Species group of S. pubescens Stephens
S. pubescens group consists of 1 species (exactly, a subspecies of S. pubescens : S. pubescens
fraternus) in Japan; see Puthz (1972b) regarding a taxonomy of, and a key to, S. pubescens andits allied species. Diagnostic characters are as follows: Legs with 3rd and 4th tarsomeres strongly
bilobed; lateroventrites wide to very wide; 9th ventrite of male with apicolateral teeth pointed(Fig. 85D); aedeagal median lobe heavily sclerotized, gradually tapering apically (Fig. 85C);
endophallic expulsion hooks each elongate, thin (Fig. 85C); gonocoxite with apicolateral tooth
pointed (Fig. 85B); spermatheca not observable.

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Stenus pubescens fraternus Casey(Figs. 85A–F, 133A)
Stenus pubescens Stephens, 1833: 297.
Stenus pubescens fraternus Casey, 1884: 155; Puthz, 2001a: 38; Herman, 2001: 2357; Naomi &Ito, 2014: 288.
Type material. Syntypes of S. pubescens fraternus: 3 exs., type locality: Wyoming Territory,
Marquette Lake Superior.
Other material examined. [HOKKAIDO]: 2 ♂1 ♀, Mitoyo, Abashiri City, Hokkaido, 6-8. v.
2009, T. Kato leg.; 1 ♂, same locality, 19. v. 2010, T. Kato leg.
Distribution. Japan (Hokkaido); Russia, North America.
Redescription. Male and female: Macropterous; body 4.8–5.7 mm (fore-body 2.5–2.9 mm) in
length, robust, relatively ﬂat, weakly shining, with antenna short; surface wholly covered with
net-like microsculptures. Body black; labrum black; antennae with 1st segment pitchy black, 2nd
to 11th segments reddish brown to brown; legs black except for dark red 4th tarsomere. Head relatively small, hardly concave dorsally, with a pair of short longitudinal impressions at the sidesof median longitudinal swollen area; punctures round to elliptical, very dense, almost regular,
distinct. Pronotum with surface provided with a pair of oblique, shallow depressions which aredivergent anteriorly; punctures round, dense, almost regular, distinct. Elytra elongate-rectangularin shape; surface weakly uneven, similarly punctate as on pronotum. Legs relatively long; tarsi
short, with 3rd and 4th tarsomeres strongly bilobed, but 4th tarsomere more strongly bilobed thanthe 3rd. Abdomen subparallel-sided; punctures basically round, moderately dense, small and regular, but punctures in posterior segments smaller than in anterior segments. Lateroventrites ventromesial in position, wide to very wide, densely punctate, pubescent.
Male. Fourth ventrite posteromedially with a small, shallow semicircular depression which isvery shallowly emarginate; 5th ventrite (Fig. 85G) anteromedially with a shallow depression, andposteromedially with a small semicircular depression which is arcuately emarginate, and also at
posterolateral parts weakly projects posteriorly and is angulate; 6th ventrite (Fig. 85G) with asimilar modiﬁcation as in 5th, but the depressed area a little more deeper and more strongly
emarginate; 7th ventrite (Fig. 85G) anteromedially with a large, shallow depression, and posteromedially with a small, semicircular ﬂat area, which is very weakly emarginate; 8th ventrite (Fig.
85G) posteriorly with a large, wide emargination, and medially with a narrow, longitudinal ﬂatarea; 9th tergum (Fig. 85A) stout, ventral apophyses each with a subtriangular, anteromesial ﬂap;
9th ventrite (Fig. 85D) elongate, arcuately emarginate posteriorly, with stem unique in shape,strongly constricted at base, basilateral emarginations large, basilateral processes wide, truncate
obliquely, apicolateral teeth small, pointed, apicolateral setae moderately long; 10th tergum (Fig.
85A) entire. Aedeagal median lobe (Fig. 85C) heavily sclerotize, bulbous basally, graduallytapering toward the apex which is narrowly truncate. Endophallic median longitudinal bands(Fig. 85C) short, sclerotized; expulsion hooks (Fig. 85C) separated, each elongate, thin; basal
tube (Fig. 85C) with tube body baculiform, moderately swollen laterally at apical part. Parameres(Fig. 85C) very stout, wide and thick; apical area large, triangular, and acutely pointed at themesial and apical corners, and furnished with 3 to 4 setae at apex, 3 to 4 short setae along posterior margin, and also 2 to 3 short setae at mesial margin.
Female. Eighth ventrite (Fig. 85E) projecting posteriorly at posteromedian part to form a triangular area which is acutely pointed; 9th tergum (Fig. 85F) without ventral apophyses; gono-

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Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

Fig. 85. Stenus pubescens fraternus Casey (Abashiri, Hokkaido). A, 9th and 10th terga of male; B, gonocoxite;
C, aedeagus; D, 9th ventrite of male; E, apex of 8th ventrite of female; F, 9th and 10th terga of female; G, 5th
to 8th ventrites of male. Scale 1: 0.2 mm for A–F; scale 2: 0.3 mm for G.

The Steninae of Japan Part 1

217

coxites (Fig. 85B) each with apicolateral tooth very small, pointed, apicolateral setae moderately
long; 10th tergum (Fig. 85F) entire. Spermatheca not observable.
Biology and Ecology. Stenus pubescens fraternus is a very rare species in Japan; and it ispresently known only from the plain of Abashiri, Hokkaido. The beetles live under moist deadleaves near the watersides, but they occasionally climb the stalk of Carex and ramble along theleaves, together with S. bohemicus.
Remarks. S. pubescens is a polytypic Stenus species which comprises 2 subspecies: S. pubescens pubescens (distribution: Europe and western Siberia) and S. pubescens fraternus (distribution: eastern Russian including Kamchatka and north America) (Puthz, 1972b, 2001a). The subspecies S. pubescens fraternus only is known from Japan, which was ﬁrst recorded only recently
from Japan by Naomi & Ito (2014). S. pubescens fraternus is separable from the nominotypicalsubspecies by the aedeagal median lobe more slender and narrower, with the apicalmost truncate
part of apical sclerotized area distinctly narrower (Fig. 85C; Sanderson, 1946, ﬁg. 19A).
Species group of S. pallitarsis Stephens
S. pallitarsis group consists of 3 species in Japan; see Puthz (1972b) regarding the taxonomy
of, and a key to, S. pallitarsis and its allied species. Diagnostic characters are as follows: Legs
with 3rd tarsomere more or less bilobed, 4th tarsomere strongly bilobed; lateroventrites very narrow through narrow to wide or very wide; 9th ventrite of male without apicolateral teeth (Fig.
86B); gonocoxite without apicolateral tooth (Fig. 86D); spermatheca with tube hardly coiled,basal pouch developed. (Fig. 86C).
Key to the Japanese species of S. pallitarsis group1(2) Abdomen without basi-longitudinal keel on terga ........................................S. aestivus Naomi
2(1) Abdomen with basi-longitudinal keel(s) on terga.
3(4) Body smaller (3.2–4.0 mm), with elytra wider than long; anterior abdominal segments with
punctures larger; aedeagal median lobe narrower, weakly angulate apicolaterally, with paramere shorter (Fig. 87A) ..................................................................... S. bifoveolatus Gyllenhal
4(3) Body larger (4.5–5.2 mm), with elytra about as long as wide; anterior abdominal segmentswith punctures smaller; aedeagal median lobe wider, uniformly rounded apicolaterally, withparamere longer (Fig. 88B) ........................................................................... S. latitarsis Sharp
Stenus aestivus Naomi(Figs. 86A–F, 133B)
Stenus aestivus Naomi, 1988b: 28; Herman, 2001: 2046; Naomi & Puthz, 2013: 139.
Type material examined. Holotype: ♀ (KUF), Kabuto-mura, Toyotomi-cho, Hokkaido, 12.
vii. 1980, H. Takemoto leg.
Other material examined. [HOKKAIDO]: 21 ♂24 ♀, Shirarutoro Lake, Kushiro City, 4. vi.
1991, R. B. Kuranishi leg.; 3 ♀, same locality, 11. vi. 1990, R. Kuranishi leg.; 1 ♀, Akanuma,
Kushiro Marsh, 16. vi. 1995, I. Matoba leg.
Distribution. Japan (Hokkaido).
Redescription. Male and female: Macropterous; body 4.0–5.7 mm (fore-body 2.1–2.7 mm) in218

Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

Fig. 86. Stenus aestivus Naomi (A, B, E, F, Shirarutoro, Hokkaido; C, D, Akanuma, Hokkaido). A, aedeagus; B,
9th ventrite of male; C, spermatheca; D, apex of gonocoxite; E, 4th to 8th ventrites of male; F, 9th and 10th
terga of male. Scale 1: 0.2 mm for A; scale 2: 0.2 mm for B; scale 3: 0.2 mm for C, D; scale 4: 0.5 mm for E;
scale 5: 0.5 mm for F.

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219

length, relatively ﬂat, weakly shining, with short antenna; surface wholly covered with short, silvery-white setae and also reticulately microsculptured. Body black; labrum black; antennae with
1st segment pitchy black, 2nd to 11th segments reddish brown to brown; legs black but tarsomeres reddish brown to dark red. Head relatively small, with a pair of longitudinal impressions at
the sides of median longitudinal swollen area; punctures round, dense to very dense, almost regular, distinct. Pronotum with a pair of oblique, shallow depressions, which are divergent anteriorly; surface similarly punctate as on head. Elytra longer than wide, elongate-rectangular inshape; surface weakly uneven, similarly punctate as on pronotum. Legs relatively long; tarsi
short, with 3rd and 4th tarsomeres strongly bilobed, but 4th tarsomere more strongly bilobed thanthe 3rd. Abdomen slender, narrowed posteriorly; punctures basically round, moderately dense,
small and regular, but punctures in posterior segments smaller than in anterior segments. Lateroventrites ventromesial in position, wide, densely punctate and pubescent.
Male. Fourth ventrite (Fig. 86E) posteromedially with a semicircular ﬂat area; 5th ventrite(Fig. 86E) anteromedially with a ﬂat area, and posteromedially with a semicircular depression
which weakly projects posteriorly and angulate at posterolateral parts, and also is arcuately emarginate posteriorly; 6th ventrite (Fig. 86E) with a similar modiﬁcation as in 5th; 7th ventrite (Fig.
86E) anteromedially with a shallow depression, and posteromedially with a semicircular ﬂat
area, which is very weakly emarginate; 8th ventrite (Fig. 86E) posteromedially with a deep,
V-shaped emargination; 9th tergum (Fig. 86F) with ventral apophyses very long; 9th ventrite(Fig. 86B) elongate, almost truncate posteriorly, with stem elongate, emarginate anteriorly, basilateral emarginations very narrow, deep, basilateral processes acutely pointed, apicolateral setae
moderately long, apicolateral teeth missing; 10th tergum (Fig.86F) entire. Aedeagal median lobe
(Fig. 86A) slender, strongly sclerotized, with a very long apicomedian projection, which has avery small globe at the apicalmost part. Endophallic median longitudinal bands (Fig. 86A) moderately long; expulsion hooks (Fig. 86A) separated, each very thin, strongly curved laterally at
posterior part; basal tube (Fig. 86A) baculiform, with basal room elongate ovoidal, tube body
simple, attenuate; inner sac (Fig. 86A) visible, with a ring near the middle of basal tube. Parameres slender, weakly sinuous, strongly sclerotized; apical area unique in shape (Fig. 86A), andfurnished with 5 to 6 long setae at the apicalmost part, and also mesially with 17 to 20 setae ofvarious length.
Female. Eighth ventrite almost triangular behind the apicolateral corners, distinctly angulate
apically; gonocoxites (Fig. 86D) each almost rounded and irregularly serrate posteriorly, withapicolateral setae very long, apicolateral tooth missing. Spermatheca (Fig. 86C) with capsulesmall; RT-duct moderately long and thick; spermathecal duct hardly coiled, moderately long,with 5 turns, distal part of the duct between the base and 1st turn moderately sclerotized; basal
valve invisible; basal pouch heavily sclerotized, elongate-conical in shape; spermathecal glandspherical, with its opening located on the lateral side of the duct a little distal from the 3rd turn.
Biology and Ecology. Stenus aestivus is presently distributed in the plains and low mountainous regions in Hokkaido. The beetles inhabit moist litter of the grasses grown at the shores ofrivers, lakes and marshes. They occasionally climb the stalk of Carex and other grasses, and ramble along the leaves.
Remarks. Stenus aestivus is allied to S. niveus Fauvel, 1865 (which is widely distributed in
the Holarctic region), but this species is separable from the latter by the aedeagal median lobe
with a very long apicomedian projection which has a very small globe at the apicalmost part(Fig. 86A), and the paramere with apical area longer and more strongly pointed apically (Fig.
86A).

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Stenus bifoveolatus Gyllenhal(Figs. 87A–I, 133C)
Stenus bifoveolatus Gyllenhal, 1827: 500; Herman, 2001: 2083; Naomi & Nomura, 2015a: 57.
Type material. Type locality: Suecia.
Other material examined. [HOKKAIDO]: 1 ♂(NMNST): Mitsumata, Kami-shihoro, Tokachi, 22. vii. 1984, M. Tomokuni leg.; 1 ♂, Akan, 16. vi. 1976, M. Sato leg.; 1 ♀, Furuume,
Bihoro-cho, 27. viii. 1993, T. Kato leg.; 1 ♀, Kushihoku Pass, Oketo-cho, 16. vii. 1999, K. Haga
leg.; 1 ♀, Aizankei Spa, Kamikawa-cho, 2. vii. 2011, K. Haga leg.; 1 ♂, Nakashibetsu, Shibetsugun, 8. v. 2015, T. Kato leg.
Distribution. Japan (Hokkaido); Russia, Kurile, Caucasus, Europe.
Redescription. Male and female: Brachypterous; body 3.2–4.0 mm (fore body: 1.5–1.8 mm)
in length, weakly shining, with antennae short. Body black; labrum black; antennae yellow toyellowish brown except for 1st black segment; legs dark red to black but tarsi pale red to reddish
brown. Head hardly concave dorsally, with the central part of vertex a little higher in level thanmesial margins of eyes, and with a pair of shallow, longitudinal depressions; punctures round,
dense, regular, distinct. Pronotum with surface weakly uneven laterally; punctures round, dense,
regular, distinct. Elytra wider than long; surface slightly uneven laterally, similarly punctate as on
pronotum, but punctures a little larger than those on pronotum (Fig. 87E). Legs relatively short;tarsi short, 3rd tarsomere emarginate posteriorly (or V-shaped), 4th tarsomere strongly bilobed.
Abdomen moderately convex dorsally; 3rd tergum with 3 short basi-longitudinal keels, 4th to 6th
terga each with 1 short basimedian keel; punctures round, moderately dense to dense, and distinct in anterior segments, while punctures in posterior segments sparse, very small to small andregular. Lateroventrites very narrow or narrow, punctate, pubescent.
Male: Sixth ventrite posteromedially with a shallow, narrow and semicircular depression,
which is shallowly emarginate; 7th ventrite medially with an elongate-elliptical depression,
which does not reach the posterior margin; 8th ventrite (Fig. 87C) posteromedially with a large,
wide emargination; 9th tergum (Fig. 87H) with ventral apophyses long; 9th ventrite (Fig. 87G)
rather wide, gently rounded and serrate posteriorly, with stem arcuately emarginate anteriorly,
basilateral emarginations indistinct, apicolateral setae moderately long, apicolateral teeth missing; 10th tergum (Fig. 87H) transverse, rounded posteriorly. Aedeagal median lobe (Fig. 87A)
well-pigmented, weakly angulate apicolaterally, acutely pointed apically; apical sclerotized area
very long, almost parallel-sided before the apical triangular part. Endophallic median longitudinal bands (Fig. 87F) moderately long, with ventral bands strongly narrowed anteriorly, dorsal
bands distinctly diverging anteriorly; expulsion hooks (Fig. 87F) small, separated, anterior platecompletely fused with posterior plate; median sclerite (Fig. 87A) spear-shaped, acute posteriorly,
apicolateral plates fused to form a heart-shaped plate; basal tube (Fig. 87F) located in the sclerotized inner sac, with basal room weakly bulbous, tube body baculiform, simple, pointed. Parameres (Fig. 87A) moderately thick, each reaching posteriorly a little before the apex of median
lobe; apical area distinctly swollen mesially, and furnished mesially with about 30 setae of various length.
Female: Eighth ventrite (Fig. 87D) obtusely pointed posteromedially; 9th tergum (Fig. 87B)
without ventral apophyses; gonocoxites (Fig. 87I) each rounded and ﬁnely serrate posteriorly,
without apicolateral tooth; 10th tergum (Fig. 87B) transverse, almost entire. Spermatheca withbasal pouch bowl-shaped, but the duct membranous and thus not observable.

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Fig. 87. Stenus bifoveolatus Gyllenhal (A, E, F, Akan, Hokkaido; B, D, I, Furuume, Hokkaido; C, G, H, Tokachi,
Hokkaido). A, aedeagus; B, 9th and 10th terga of female; C, apex of 8th ventrite of male; D, apex of 8th ventrite of female; E, right elytron; F, endophallic structures; G, 9th ventrite of male; H, 9th and 10th terga of
male; I, gonocoxite. Scale 1: 0.2 mm for A–D, G–I, 0.1 mm for F; scale 2: 0.3 mm for E.

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Biology and Ecology. Stenus bifoveolatus is distributed in the plains and low mountainous
regions. No exact data are obtained on the habitats of this species, but the collecting records suggest that the beetles inhabit moist litter of the grasses grown at the shores of rivers, lakes andmarshes.
Remarks. Stenus bifoveolatus was ﬁrst recorded only recently from Japan by Naomi &Nomura (2015a). S. bifoveolatus is closely allied to S. latitarsis from Japan and S. exter Puthz,
2006b from Taiwan, but this species is separable from the latter two species by the body smaller(3.2–4.0 mm), with elytra wider than long, the anterior segments of abdomen with punctureslarger, the aedeagal median lobe narrower and weakly angulate apicolaterally (Fig. 87A), and theparameres shorter, and not reaching the apex of median lobe (Fig. 87A).
Stenus latitarsis Sharp(Figs. 88A–G, 133D)
Stenus latitarsis Sharp, 1889: 329; Herman, 2001: 2256; Naomi & Puthz, 2013: 139.
Type material examined. Holotype: ♂ (NHML), paratype: 1 ♀ (NHML), Miyanoshita, Kanagawa [examined by Puthz in 1968].
Other material examined. [HONSHU]: 1 ♂, Ooike, Tsuchiura City, Ibaraki Pref., 23. vi.
1984, S. Ohmomo leg.; 1 ♂, Migimomi, Tsuchiura City, Ibaraki Pref., 3. v. 1984, S. Ohmomoleg.; 1 ♀, Urawa City, Saitama Pref., 16. iv. 1994, K. Ohgi leg.; 1 ♂, Hizaura, Ohara-cho, Chiba
Pref., 30. iii. 1990, T. Takeda leg.; 1 ♂, same locality, 23. xii. 1989, T. Takeda leg.; 1 ♀, Nakazawa, Kamagaya City, Chiba Pref., 2. iv. 1990, T. Takeda leg.; 1 ♀, Onari, Chiba City, Chiba
Pref., 3. vi. 1990, T. Takeda leg.; 1 ♀, Akame, Mikurashiba, Mobara City, Chiba Pref., 3. vi.
1990, T. Takeda leg.; 1 ♀, Tomigasawa, Shirai-cho, Chiba Pref., 24. vi. 1990, T. Takeda leg.; 1 ♀,Funabashi City, Chiba Pref., 29. v. 1990, T. Takeda leg.; 1 ♀, Kaneoya-cho, Chiba City, Chiba
Pref., 21. xi. 1989, T. Takeda leg.; 1 ♂3 ♀, Ookusa, Chiba City, Chiba Pref., 24. v. 2005, R. Kuranishi leg.; 3 ♂1 ♀, Sakura City, Chiba Pref., 14. v. 1994, K. Ohgi leg.
Distribution. Japan (Honshu).
Redescription. Male and female: Brachypterous; body 4.5–5.2 mm (fore body: 2.1–2.5 mm)
in length, moderately shining, with antennae short. Body black; labrum black; antennae with 1st
segment black, remaining segments yellow to yellowish brown; legs dark red to black but tarsi
pale red to reddish brown. Head hardly concave dorsally, with a pair of shallow, longitudinal
depressions at the sides of median longitudinal swollen area; punctures round to elliptical, dense
to very dense, various in size. Pronotum with surface weakly uneven laterally, sometimes with a
median longitudinal impunctate area; punctures round, dense to very dense, various in size, distinct. Elytra about as long as wide; surface rather uneven, punctures round to elliptical, dense,
somewhat irregular. Legs relatively short; tarsi short, with 3rd tarsomere emarginate posteriorly,
4th tarsomere strongly bilobed. Abdomen moderately convex dorsally; 3rd tergum with 3 short,basal keels, 4th to 6th terga each with 1 short, basimedian keel; punctures basically very sparseto moderately dense, small to small and distinct, but somewhat irregular throughout. Lateroventrites very narrow or narrow, punctate, pubescent.
Male: Sixth and 7th ventrites each posteromedially with a semicircular, ﬂat area; 8th ventrite(Fig. 88F) posteromedially with a large, wide emargination; 9th tergum (Fig. 88D) with ventral
apophyses long; 9th ventrite (Fig. 88E) wide, almost rounded and ﬁnely serrate apicolaterally,
with stem very wide, shallowly emarginate anteriorly, spicolateral setae moderately long, apico-

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223

Fig. 88. Stenus latitarsis Sharp (A, B, D–F, Ooike, Ibaraki; C, G, Kaneoya, Chiba). A, Endophallic structures; B,
aedeagus; C, spermatheca; D, 9th and 10th terga of male; E, 9th ventrite of male; F, apex of 8th ventrite ofmale; G, gonocoxite. Scale 1: 0.1 mm for A, 0.2 mm for C, G; scale 2: 0.2 mm for B, D, E; scale 3: 0.3 mm for
F.

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lateral teeth missing; 10th tergum (Fig. 88D) transverse, rounded posteriorly. Aedeagal median
lobe (Fig. 88B) well-pigmented, uniformly rounded apicolaterally, acutely pointed apically, withapical sclerotized area very long. Endophallic median longitudinal bands (Fig. 88A) similarly
structured as in S. bifoveolatus; expulsion hooks (Fig. 88A) contiguous at the posteromesial corners, diverging anteriorly, with anterior plate completely fused with posterior plate; median sclerite (Fig. 88A) spear-shaped, very acute, apicolateral plates contiguous by the posteromesial corners, each plate elongate-triangular in shape, weakly folded along the posterior margin; basal
tube (Fig. 88A) very long, with basal room spherical, tube body baculiform, weakly swollen
behind the middle, acutely pointed apically. Parameres (Fig. 88B) each very weakly incurved,
weakly sinuate at mesial margin, extending posteriorly a little beyond the apex of median lobe;
apical area moderately swollen mesially, and furnished mesially with about 30 to 35 setae of various length.
Female: Eighth ventrite obtusely pointed posteromedially; gonocoxites (Fig. 88G) each truncate but serrate posteriorly, and simply angulate apicolaterally (i.e., distinct apicolateral toothmissing), apicolateral setae moderately long. Spermatheca (Fig. 88C) with duct hardly coiled,moderately wide, with 5 turns; capsule, RT-duct and duct not distinctly differentiated; basal valve
simple; basal pouch large, bowl-shaped.
Biology and Ecology. Stenus latitarsis is distributed in the plains. The beetles inhabit moist
litter of the grasses grown at the shores of rivers and ponds; and they also inhabit moist leaf letter
heaped in the grasslands.
Remarks. Stenus latitarsis is closely allied to S. bifoveolatus, but this species is separablefrom the latter by the body larger (4.5–5.2 mm), with elytra about as long as wide, the anterior
segments of abdomen with punctures smaller, the aedeagal median lobe wider and uniformlyrounded apicolaterally (Fig. 88B), and the parameres longer and reaching posteriorly a little
beyond the apex of median lobe (Fig. 88B).
Species group of S. ﬂavipes Stephens
S. ﬂavipes group (Puthz, 2013: 1282) consists of 3 species in Japan; see Puthz (1972b)
regarding the taxonomy of, and a key to, S. ﬂavipes and its allied species. Diagnostic characters
are as follows: Body relatively ﬂat dorsally (Fig. 133E); legs with 2nd to 4th tarsomeres more orless bilobed; lateroventrites very narrow to narrow; 9th ventrite of male without apicolateral
teeth (Fig. 89E); aedeagal median lobe with apical sclerotized area developed (Fig. 89A); gonocoxite serrate posteriorly, without apicolateral tooth (Fig. 89F); spermatheca with its duct notcoiled with 4 or 5 turns (Fig. 90F).
Key to the Japanese species of S. ﬂavipes group1(4) Body wider, with elytral humeri well developed (Fig. 133E); and aedeagal median lobe withapicolateral corners more or less angulate.
2(3) Seventh ventrite of male posteromedially with a wider, semicircular ﬂat area (Fig. 89B);
aedeagal median lobe simply pointed apicomedially (Fig. 89A); endophallic expulsion hooksmaller, pointed posteromedially (Fig. 89A)............................................... S. depressus Puthz
3(2) Seventh ventrite of male posteromedially with a narrower, almost ovoidal depression (Fig.
83B); aedeagal median lobe with a pointed, apicomedial projection (Fig. 90A); endophallic
expulsion hooks larger, widely emarginate posteriorly (Fig. 90A) ...........................................

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225...........................................................................S. ancyleus Naomi, Nomura & Puthz sp. nov.
4(1) Body narrower, with elytral humeri narrowed (Fig. 133G); and aedeagal median lobe without apicolateral corners (Fig. 91A) ......................................................... S. benefactor Ryvkin
Stenus depressus Puthz(Figs. 89A–F, 133E)
Stenus depressus Puthz, 1973; Naomi, 1988b: 28; Herman, 2001: 2159; Naomi & Puthz, 2013:
139.
Type material examined. Holotype: ♂ (MHNG), paratypes: 2 ♀ (cP), Suputinsky Reserve,
Ussurisk, 22. vi. 1967, A. Tichomirova leg. [examined by Puthz].
Other material examined. [HOKKAIDO]: 1 ♂, Tomakomai, 30. vi. 1973; 1 ♀, Mt. Kariba,
Shiribeshi, 12. vi. 1986, S. Nomura leg.; 1 ♀, Memanbetsu, 28. v. 1992, T. Kato leg.; 2 ♀, Hyotan
Pond, Akan N. P., 4. vii. 1986, S. Nomura leg.; 2 ♂1 ♀, Motobetsu River, Motobetsu-cho, 7. vii.
2004, K. Haga leg.; 2 ♀, Nakayama Pass, 22. vi. 1986, K. Morimoto leg.; 1 ♀, Onʼnenai, Tsurui,
Kushiro Moor, 24. viii. 1990, M. Sakai leg.; 2 ♂1 ♀, Oketo, 14. ix. 1992, T. Kato leg. [HONSHU]: 2 ♂, Yachi Spa, Aomori Pref., 6. viii. 1964, Y. Shibata leg.; 1 ♀, Saitu, Tohoku-machi,
Aomori Pref., 3. viii. 1998, H. Yoshitomi leg.; 2 ♀, Mt. Dogyo, Tadami-cho, Fukushima Pref., 2.
vii. 1995, K. Haga leg.; 1 ♂, Jikkoku, Ami-machi, Ibaragi Pref., 2. v. 1990, S. Ohmomo leg.;2 ♂6 ♀, Mt. Kurohime, Shinano-machi, Nagano Pref., 6. vii. 2008, K. Kanno leg.; 1 ♂, Kurakake
Pass, Irihirose-mura, Niigata Pref., 11. vi. 1995, K. Haga leg.; 2 ♀, Hiwada, Takane-mura, Gifu
Pref., 25. vi. 1995, H. Yoshitomi leg.; 1 ♀, Mennoki Pass., Inabu-cho, Aichi Pref., 30. vi. 1995,
H. Yoshitomi leg.; 1 ♀, Mt. Koya, Wakayama Pref., 7. viii. 1984, I. Matoba leg.
Distribution. Japan (Hokkaido, Honshu); Taiwan, China, Russia.
Redescription. Male and female: Macropterous / brachypterous; body 3.5–4.0 mm (fore
body: 1.8–2.0 mm) in length, somewhat ﬂat dorsally, moderately shining, with antennae short.
Body dark brown to black; labrum black; antennae and legs wholly yellow to pale yellowish red.
Head hardly concave dorsally, with a pair of shallow depressions; punctures round, dense to very
dense and distinct, but the central part of median longitudinal swollen area almost impunctate.
Pronotum with surface even, with a short, median longitudinal impunctate area; punctures round,
dense, distinct. Elytra with humeri developed; surface weakly uneven, similarly punctate as on
pronotum. Legs relatively short, moderately thick; tarsi short, with 2nd and 3rd tarsomeres eachemarginate posteriorly, 4th tarsomere strongly bilobed. Abdomen subparallel-sided; puncturesmoderately dense, small and distinct in general, but punctures in 8th segment very small andsparse. Lateroventrites narrow, punctate, pubescent.
Male: Fifth ventrite (Fig. 89B) posteromedially with a semicircular, ﬂat area; 6th ventrite(Fig. 89B) posteromedially with a semicircular, shallow depression; 7th ventrite (Fig. 89B) posteromedially with a relatively large, semicircular ﬂat area, which is very shallowly emarginate
posteriorly; 8th ventrite (Fig. 89B) posteromedially with a V-shaped emargination; 9th tergum(Fig. 89C) with ventral apophyses long, straight; 9th ventrite (Fig. 89E) wide, rounded apicolaterally, very shallowly emarginate and also serrate posteriorly, with stem transverse, submembranous in marginal part, with apicolateral setae long, apicolateral teeth missing; 10th tergum (Fig.
89C) very shallowly emarginate apicomedially. Aedeagal median lobe (Fig. 89A) elongate, bulbous basally, narrowed apically toward the pointed apex, with apicolateral corners angulate; apical sclerotized area long, declivous laterally, and anteromedially with a narrow, V-shaped emargi-

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Fig. 89. Stenus depressus Puthz (A, B, E, Yachi, Aomori; C, Motobetsu, Hokkaido; D, F, Hyotan, Hokkaido). A,
aedeagus; B, 5th to 8th ventrites of male; C, 9th and 10th terga of male; D, basal part of spermatheca; E, 9th
ventrite of male; F, apex of gonocoxite. Scale 1: 0.1 mm for A; scale 2: 0.3 mm for B; scale 3: 0.2 mm for C,
E, 0.1 mm for D, F.

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227

nation. Endophallic median longitudinal bands (Fig. 89A) moderately long and wide; laterallongitudinal bands (Fig. 89A) short; expulsion hooks (Fig. 89A) fused to form a small, transverse
sclerite which is pointed posteromedially; basal tube (Fig. 89A) with basal room invisible, tube
body very long, baculiform, swollen near the middle, and simply attenuate behind the middle.
Parameres (Fig. 89A) moderately thick, very weakly incurved; apical area distinctly swollen
mesially, and furnished mesially with about 22 to 25 setae.
Female: Eighth ventrite obtusely pointed posteromedially; gonocoxites (Fig. 89F) eachweakly rounded and also distinctly serrate posteriorly, with apicolateral setae very long, apicolateral tooth missing. Spermatheca with basal pouch large, conical (Fig. 89D); spermathecal duct
membranous and thus not observable.
Biology and Ecology. Stenus depressus is distributed in the plains and mountainous regionsin Japan. The beetles inhabit moist litter of the grasses (e.g., reeds) grown at the shores of rivers,
lakes and marshes. They often climb the stalk of Carex and other grasses, and ramble along theleaves.
Remarks. Stenus depressus was ﬁrst recorded from Japan (Hokkaido) by Naomi (1988b).
This species is allied to S. ﬂavipes Stephens, 1833 from Europe, but it is separable from the latterby the coloration of antennae (wholly pale yellow to yellowish red) (Puthz, 1973b). Among theJapanese members of this group, S. depressus is allied to S. ancyleus, but this species is separablefrom the latter by the 7th ventrite of male posteromedially with a wider, semicircular ﬂat area
(Fig. 89B), the aedeagal median lobe simply pointed apicomedially (Fig. 89A), and the endophallic expulsion hook completely fused, smaller, and pointed posteromedially (Fig. 89A).
Stenus ancyleus Naomi, Nomura & Puthz, sp. nov.
(Figs. 90A–F, 133F)
Type material examined. [HONSHU]: Holotype, ♂ (No. NSMT-I-C-200321 in NMNST),Asama Spa, Matsumoto City, Nagano Pref., 24. iv. 1996, Y. Furihata leg. Paratypes: 1 ♂2 ♀ (cN),same data as holotype.
Distribution. Japan (Honshu: Nagano Pref.).
Description. Male and female: Macropterous; body 3.5–4.1 mm (fore body: 1.8–2.1 mm) in
length, somewhat ﬂat dorsally, moderately shining, with antennae short. Body dark brown to
black; labrum black; antennae and legs wholly pale yellow to yellowish red. Head hardly concave dorsally, with a pair of shallow depressions; punctures round, dense to very dense and distinct, but the central part of median longitudinal swollen area often impunctate. Pronotum withsurface almost even, with a short median longitudinal area which is impunctate but indistinct inoutline; punctures round, dense, irregular, distinct. Elytra with humeri developed; surface weakly
impressed along suture; punctures round, dense, regular, distinct. Legs relatively short; tarsi
short, with 2nd and 3rd tarsomeres each emarginate posteriorly, 4th tarsomere strongly bilobed.
Abdomen subparallel-sided; punctures moderately dense, very small to small, distinct. Lateroventrites narrow, punctate, pubescent.
Male: Fifth ventrite (Fig. 90B) posteromedially with a semicircular ﬂat area; 6th ventrite(Fig. 90B) posteromedially with a bell-shaped, shallow depression which is very shallowly emarginate posteriorly; 7th ventrite (Fig. 90B) posteromedially with a subovoidal depression, which isarcuately emarginate posteriorly; 8th ventrite (Fig. 90B) posteromedially with a medium-sized
emargination; 9th tergum (Fig. 90C) elongate, with ventral apophyses very long; 9th ventrite(Fig. 90E) elongate, rounded apicolaterally, shallowly emarginate and also ﬁnely serrate posteri-228

Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

Fig. 90. Stenus ancyleus Naomi, Nomura & Puthz sp. nov. (Matsumoto, Nagano). A, aedeagus; B, 5th to 8th
ventrites of male; C, 9th and 10th terga of male; D, gonocoxite; E, 9th ventrite of male; F, spermatheca. Scale
1: 0.2 mm for A, C, E, 0.1 mm for D, F; scale 2: 0.3 mm for B.

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229

orly, with stem wide, submembranous laterally, apicolateral setae long, apicolateral teeth missing; 10th tergum (Fig. 90C) very shallowly emarginate apicomedially. Aedeagal median lobe
(Fig. 90A) elongate, very weakly constricted near the middle, with the pointed apicomedian projection; apical sclerotized area long, declivous laterally. Endophallic median longitudinal bands(Fig. 90A) with ventral bands relatively short, dorsal bands long, each narrowed anteriorly; lateral longitudinal bands (Fig. 90A) very short; expulsion hooks (Fig. 90A) fused only posteriorly,
shallowly emarginate posteriorly, each hook pointed anteriorly; basal tube (Fig. 90A) with basal
room very short, tube body very long, baculiform, weakly swollen at the basal 2/3, sinuous
behind the swollen area, and pointed apically. Parameres (Fig. 90A) weakly incurved; apical area
weakly swollen mesially, and furnished mesially with about 23 to 25 setae.
Female: Eighth ventrite rounded posteriorly; gonocoxites (Fig. 90D) each serrate posteriorly,
with apicolateral setae very long. Spermatheca (Fig. 90F) with duct submembranous, not coiled,with 4 or 5 turns; basal pouch conical.
Biology and Ecology. Stenus ancyleus is presently distributed only in the mountainous regionof Nagano Pref., central Japan. The beetles inhabit moist litter of the grasses grown at the shoresof marshes.
Remarks. Stenus ancyleus is allied to S. depressus, but this species is separable from the latter by the 7th ventrite of male posteromedially with a narrower, subovoidal depression (Fig.
90B), the aedeagal median lobe with its apicomedial projection pointed, (Fig. 90A), the endophallic expulsion hooks partially fused posteriorly, larger, and shallowly emarginate posteriorly(Fig. 90A).
Etymology. The speciﬁc epithet of this species is derived from the Latin adjective “ancyleus”,
which means “ancyleous” or “curved”; and the parameres are weakly curved mesially in the middle as in Fig. 90A.
Stenus benefactor Ryvkin(Figs. 91A–F, 133G)
Stenus benefactor Ryvkin, 1985: 853; Herman, 2001: 2080; Naomi & Puthz, 2013: 139.
Stenus kanmiyai Naomi, 1988b: 31.
Type material. Holotype: ♂ (ZMMSU), type locality: Primorskii Krai, Sudzukhinskii zapovednik.
Other material examined. [HOKKAIDO]: 1 ♂1 ♀, Chitose Lake, Chitose City, 17. vi. 1995,
K. Miyashita leg.; 1 ♂, Akanuma, Kushiro Moor, 25. viii. 1990, M. Sato leg. [HONSHU]:
1 ♂4 ♀, Takahama, Kamisu-cho, Ibaraki Pref., 19. iii. 2005, M. Maruyama leg.; 3 ♂, Watarase
Marsh, Tochigi Pref., 15. ix. 1993, H. Ohkawa leg.; 1 ♀, Watarase River, Fujioka-cho, Tochigi
Pref., 1. iv. 1997, M. Maruyama leg.; 1 ♀, Kotanuki Marsh, Inogashira, Fujinomiya City, Shizuoka Pref., 3. viii. 2008, Y. Tahira leg. [SHIKOKU]: 2 ♂1 ♀, Ryujindaira, Mt. Saragamine,
Ehime Pref., 20. xi. 1993, M. Sakai leg.
Distribution. Japan (Hokkaido, Honshu, Shikoku, Kyushu); Russia.
Redescription. Male and female: Brachypterous; body 3.1–4.0 mm (fore body: 1.4–1.8 mm)
in length, rather thin, somewhat ﬂat dorsally, weakly shining, with antennae short. Body darkbrown to black; labrum black; antennae and legs wholly pale yellow to yellowish red. Headhardly concave dorsally, with a pair of shallow depressions; punctures round, dense to very
dense, distinct. Pronotum with surface even, with a short median longitudinal area which is

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Fig. 91. Stenus benefactor Ryvkin (A–C, Akanuma, Hokkaido; D, F, Takahama, Ibaraki; Chitose, Hokkaido). A,
aedeagus; B, 9th ventrite of male; C, 5th to 8th ventrites of male; D, spermatheca; E, 9th and 10th terga of
male; F, apex of gonocoxite. Scale 1: 0.1 mm for A, B; scale 2: 0.3 mm for C; scale 3: 0.1 mm for D, F, 0.2
mm for E.

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231

impunctate; punctures round, dense, almost regular, distinct. Elytra narrowed at humeri; surface
similarly punctate as on pronotum. Legs relatively short; tarsi short, with 2nd tarsomere weakly
and 3rd one distinctly emarginate posteriorly, 4th tarsomere strongly bilobed. Abdomen subparallel-sided; punctures moderately dense to dense, small, distinct. Lateroventrites very narrow tonarrow, punctate, pubescent.
Male: Fifth ventrite (Fig. 91C) posteromedially with a semicircular ﬂat area; 6th ventrite(Fig. 91C) posteromedially with a semicircular, shallow depression which is very shallowly
emarginate posteriorly; 7th ventrite (Fig. 91C) medially with an elongate depression; 8th ventrite(Fig. 91C) posteromedially with a V-shaped emargination; 9th tergum (Fig. 91E) with ventral
apophyses long; 9th ventrite (Fig. 91B) wide, distinctly serrate apicolaterally, shallowly emarginate posteriorly, with apicolateral setae long; 10th tergum (Fig. 91E) very shallowly emarginate
apicomedially. Aedeagal median lobe (Fig. 91A) bulbous basally, then narrowed apically without
apicolateral corners, and very acutely pointed at apex; apical sclerotized area elongate-triangularin shape, ventrally with a median longitudinal keel. Endophallic median longitudinal bands (Fig.
91A) with ventral bands relatively short; lateral longitudinal bands (Fig. 91A) very short; expulsion hooks (Fig. 91A) fused to form a subtrapezoidal sclerite which is widely emarginate posteriorly; basal tube (Fig. 91A) with basal room very narrow, tube body consisting of two partiallynested pipes (which each open ventrally), proximal pipe widened posteriorly, distal pipe nested
basally in proximal pipe, strongly constricted a little before the middle, with the apical partbehind the constriction strongly narrowed to the pointed apex. Parameres (Fig. 91A) each weakly
sinuous; apical area weakly swollen both mesially and laterally, and furnished mesially with
about 23 to 26 setae.
Female: Eighth ventrite obtusely angulate posteromedially; gonocoxites (Fig. 91F) each serrate posteriorly, with apicolateral setae very long. Spermatheca (Fig. 91D) with duct submembranous, not coiled, with 3 turns; basal pouch large, conical.
Biology and Ecology. Stenus benefactor is distributed in the plains and low and high mountainous regions in Japan. The beetles inhabit moist litters of the grasses (e.g., reeds) grown at theshores of the rivers, lakes and marshes; and they often climb the stalk of Carex and other grasses,
and ramble along the leaves.
Remarks. Stenus benefactor is allied to S. depressus and S. ancyleus, but this species isclearly separable from the latter two speciess by the body distinctly narrower, the elytra distinctly
narrowed at humeral parts (Fig. 133G), and the aedeagal median lobe almost uniformly narrowed
apically, without apicolateral corners (Fig. 91A).
Species group of S. piliferus Motschulsky
S. piliferus group consists of 5 species in Japan; see Puthz (1972a) regarding a characterization of this group and Puthz (2013) regarding a list of the species of this group. Diagnostic characters are as follows: Vertex narrow with 5 smooth, lustrous areas (Fig. 133L) except for somespecies; antennae short; pronotum short, convex; legs reddish yellow, but such portions as knees
and apices of tibiae often more or less infuscate (Figs. 133K, 133L); 3rd and 4th tarsomeres moreor less bilobed; lateroventrites and tergo-ventrite sutures on abdomen completely missing; 9th
tergum of male usually with ventral apophyses very long, posteriorly with a cleaning comb (Fig.
96A); 9th ventrite of male pubescent posteromedially (Fig. 95D), with apicolateral teeth falcate(Fig. 92G) or acutely pointed (Fig. 96B); aedeagal median lobe various in shape, but usually with
inner sac which is at least partially furnished with short spines, spinules and / or small tubercles

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Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz(Fig. 96C); gonocoxite usually with apicolateral tooth falcate (Fig. 94E); spermatheca with sclerotized RT-duct (Fig. 92F), entirely with submembranous duct (Fig. 94C), or not sclerotized andthus not observable.
Key to the Japanese species of S. piliferus group1(4) Vertex with two or three smooth, lustrous areas, or without such lustrous areas.
2(3) Body distinctly wider; head without smooth, lustrous areas (Fig. 133H); posterior segmentsof abdomen with punctures denser; aedeagal median lobe more slender, narrower (Fig.
92B); parameres longer (Fig. 92B) ............................................................. S. concinnus Sharp
3(2) Body distinctly narrower; head with two or three smooth, lustrous areas (Fig. 133I); posterior segments of abdomen with punctures sparser; aedeagal median lobe thicker, wider (Fig.
93D); parameres shorter (Fig. 93D) ............... S. oliverbetzi Naomi, Nomura & Puthz sp. nov.
4(1) Vertex with ﬁve smooth, lustrous areas.
5(6) Body furnished sparsely with long, suberect setae (Fig. 94F); aedeagal median lobe withbasal and lateral ﬂaps in basal 2/3 (Fig. 94B) ................................................S. hirtellus Sharp
6(5) Body covered only with short setae; aedeagal median lobe without ﬂaps.
7(8) Body narrower, smaller on average (2.8–4.0 mm); 8th ventrite of male posteromedially witha shallower emargination (Fig. 95A); aedeagal median lobe simply pointed apically (Fig.
95B) .................................................................................................................. S. oblitus Sharp
8(7) Body wider, larger on average (3.6–4.2 mm); 8th ventrite of male posteromedially with adeeper emargination (Fig. 96D); aedeagal median lobe with the very long, lanceolate apicomedian projection (Fig. 96C) ..............................................................S. piliferus Motschulsky
Stenus concinnus Sharp(Figs. 92A–G, 133H)
Stenus concinnus Sharp, 1889: 332; Herman, 2001: 2138; Naomi & Puthz, 2013: 139; Puthz,
2013: 1361.
Stenus shaowuensis Puthz, 1968c: 43; Puthz, 2013: 1361 (as synonym of S. concinnus).
Type material examined. Holotype: ♂ (NHML), type locality: Niigata, Japan [examined by
Puthz in 1969, 2012].
Other material examined. 1 ♀, Mitsui-cho, Wajima City, Ishikawa Pref., 20. x. 1990, K.
Yamaaki leg.
Distribution. Japan (Honshu); China.
Redescription. Male and female: Macropterous; body 2.5–3.2 mm (fore body 1.3–1.6 mm) in
length, strongly shining, with antennae short, elytra large. Body black; labrum and palpi yellowish brown to reddish brown; antennae with basal segments reddish brown, posterior segments
infuscate; legs pale yellowish brown to reddish brown, with knees infuscate. Head small, simply
ﬂat dorsally; punctures round, very dense, various in size, distinct. Pronotum with surface
weakly uneven, similarly punctate as on head, but punctures a little larger than those on head.
Elytra well-convex dorsally, arcuately emarginate posteriorly; surface weakly uneven, with punctures round, very dense, their interstices very smooth, strongly shining. Legs relatively long; tarsi
short, 3rd tarsomere weakly, asymmetrically bilobed with its mesial lap longer than lateral one,
4th tarsomere strongly bilobed. Abdomen cylindrical; 9th tergum (Fig. 92E) with a cleaning

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Fig. 92. Stenus concinnus Sharp (A, C, D, E, F, Wajima, Ishikawa; B, G, Fukien, China after Puthz, 1968c). A,
gonocoxite; B, aedeagus; C, 8th ventrite of female; D, 8th tergum of female; E, 9th and 10th terga of female;F, spermatheca; G, , 9th ventrite of male. Scale 1: 0.1 mm for A, F, 0.2 mm for C, D; scale 2: 0.1 mm for B, E,
G.

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Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

comb; punctures round, moderately dense to dense, small, distinct. Lateroventrites and tergoventrite sutures missing on abdomen.
Male: Seventh ventrite ﬁnely, densely punctate and pubescent at posteromedian part, andvery shallowly emarginate posteromedially; 8th ventrite posteromedially with a narrow, subtriangular emargination; 9th ventrite (Fig. 92G) spindle-shaped, very ﬁnely serrate posteriorly, withapicolateral teeth falciform, acute; 10th tergum rounded posteromedially. Aedeagal median lobe
(Fig. 92B) slender, acutely pointed apically, with apical sclerotized area elongate-triangular inshape. Endophallic median longitudinal bands (Fig. 92B) very long; basal tube (Fig. 92B) rather
long, simply acicular; inner sac (Fig. 92B) densely covered internally with spinules and small
scales. Parameres (Fig. 92B) each thick basally, very long and extending posteriorly far beyond
the apex of median lobe; apical area short, hardly swollen mesially, and furnished mesially with
about 10 to 12 short setae.
Female: Eighth tergum (Fig. 92D) truncate posteriorly; 8th ventrite (Fig. 92C) gently
rounded posteriorly; gonocoxites (Fig. 92A) each elongate, rounded apicomedially, with apicolateral tooth long, falciform, acute; 10th tergum (Fig. 92E) subpentagonal in shape, angulate posteromedially. Spermatheca (Fig. 92F) with capsule long, rounded apically; RT-duct moderately
sclerotized, weakly curved; spermathecal duct very short; basal valve invisible; basal pouch
large, almost cone-shaped; spermathecal gland very small, ovoidal, with its opening located at
the lateral side of the apical part of RT-duct.
Biology and Ecology. Stenus concinnus was ﬁrst described from Niigata, Central Japan by
Sharp (1889). After that, no additional beetles of this species have been collected from Japan;
and thus the present record of this species from Ishikawa (which is geographically placed near
the type locality of this species) is probably the 2nd report, suggesting that this is a very rare Stenus species in Japan. When considering the previous two records, this species is known only
from the plains of the northern part of Chubu district of Honshu. The female beetle of this species examined was collected from litter of the grasses near the paddy ﬁelds.
Remarks. Stenus concinnus is allied to S. oliverbetzi, but this species is separable from thelatter by the body distinctly wider (Fig. 133H), the posterior segments of abdomen with punctures denser, the aedeagal median lobe more slender and narrower (Fig. 92B), the endophallic
basal tube simply acicular (Fig. 92B) and the paramere longer (Fig. 92B).
Stenus oliverbetzi Naomi, Nomura & Puthz sp. nov.
(Figs. 93A–I, 133I)
Type material examined. Holotype: ♂ (No. NSMT-I-C-200322 in NMNST), Ketsuka,
Higashi-matsuyama City, Saitama Pref., 5. iv. 1998, T. Kishimoto leg. Paratypes: 1 ♂2 ♀ (cN),
Ushiku Pond, Ryugasaki City, Ibaraki Pref., 18. iii. 1998, C. Ishikawa leg.; 3 ♂4 ♀ (cN), Takahama, Kamisu-cho, Ibaraki Pref., 19. iii. 2005, M. Maruyama leg.; 2 ♂ (cN), Yataba, Hasakimachi, Ibaraki Pref., 23. iv. 1999, T. Kishimoto leg.; 1 ♂1 ♀ (cN), Takahamairi, Ishioka City,
Ibaraki Pref., 5. x. 1996, T. Kishimoto leg,; 2 ♀ (cN), same data as holotype; 1 ♂, same locality,
31. viii. 1997, K. Toyoda leg.; 1 ♀ (cN), Shinkoji, Hikage, Tamagawa-mura, Saitama Pref., 24.
xi. 1997, K. Toyoda leg.; 1 ♂1 ♀ (cK), Shinshuku-shinden, Showa-machi, Saitama Pref., 23-24.
x. 2004, H. Kamezawa leg.; 1 ♀ (cK), same locality, 10. x. 2004, H. Kamezawa leg.; 3 ♂2 ♀
(cN), Teganuma Lake, Sakura City, Chiba Pref., 8. x. 1998, T. Shimada leg.; 1 ♂ (cN), same
locality, 11. x. 1998, T. Ishikawa leg.; 1 ♂ (cN), same locality, 8. xi. 1998, T. Ishikawa leg.; 1 ♂
(cN), same locality, 28. iii. 1998, C. Ishikawa leg.; 1 ♀ (cN), Shinjyuku, Tonocho-machi, Chiba

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235

Fig. 93. Stenus oliverbetzi Naomi, Nomura & Puthz sp. nov. (A, C, G, H, Ketsuka, Saitama; B, D–F, Ushiku,
Ibaraki). A, 9th ventrite of male; B, endophallic basal tube; C, 9th and 10th terga of male; D, aedeagus; E,
expulsion hook; F, giraffeʼs ﬂeck-like pattern on median longitudinal bands; G, spermatheca; H, gonocoxite; I,
7th to 8th ventrites of male. Scale 1: 0.1 mm for A, C, G, H, 0.05 mm for B, E, F; scale 2: 0.1 mm for D; scale
3: 0.3 mm for I.

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Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

Pref., 23. iv. 1999, T. Kishimoto leg.; 1 ♀ (cN), Katousu, Sawara City, Chiba Pref., 8. vi. 1996, T.
Kishimoto leg.; 1 ♂ (cN), Inzai-mura, Chiba Pref., 28. iii. 1990, T. Takeda leg.; 1 ♀ (cN), Funagata, Noda City, Chiba Pref., 6. iv. 1990, T. Takeda leg.
Distribution. Japan (Honshu).
Description. Male and female: Macropterous; body 2.5–3.2 mm (fore body 1.2–1.4 mm) in
length, strongly shining, with antennae short, abdomen slender. Body black but elytra and 8th
abdominal segment reddish brown to dark red; labrum reddish brown; antennae with 2 or 3 basal
segments reddish brown, remaining segments dark brown; legs yellowish brown to dark reddish
brown, with knees infuscate. Head small, almost simply ﬂat dorsally, with 2 or 3 smooth, lustrous areas (two areas are behind the antennal tubercles, and other one is, if present, at the posteromedian area between eyes); punctures round, very dense. Pronotum with surface almost
even; punctures round, very dense, distinct. Elytra well-convex dorsally, arcuately emarginate
posteriorly; surface almost even, similarly punctate as on pronotum. Legs relatively long; tarsi
short, 3rd tarsomere weakly, asymmetrically bilobed with its mesial lap longer than lateral one,
4th tarsomere strongly bilobed. Abdomen cylindrical; 9th tergum (Fig. 93C) with a cleaning
comb; punctures round to elliptical and dense to very dense at the bases of 3rd and 4th segments,
while punctures on the other parts of abdomen round, sparse and very small to small. Lateroventrites and tergo-ventrite sutures missing on abdomen.
Male: Seventh ventrite (Fig. 93I) posteromedially with a semicircular ﬂat area which is furnished laterally with several setae; 8th ventrite (Fig. 93I) posteromedially with a very shallow
emargination; 9th tergum (Fig. 93C) with ventral apophyses moderately long; 9th ventrite (Fig.
93A) elongate-subovoidal in shape, very ﬁnely serrate posteriorly, with stem rounded anteriorly,
apicolateral teeth long, falciform, apicolateral setae moderately long, surface densely setous onlyat the median area a little behind the middle; 10th tergum (Fig. 93C) very ﬁnely serrate posteriorly, and also posteromedially with a very weakly emargination. Aedeagal median lobe (Fig.
93D) elongate, subparallel-sided, rounded apicolaterally, with a very short apicomedian projection; apical sclerotized area sclerotized laterally, with the apicomedian subtransparent area ovoidal in shape. Endophallic median longitudinal bands (Fig. 93D) wide, with ventral bands longer
than dorsal bands, surface covered densely with giraffeʼs ﬂeck-like pattern (Fig. 93F); expulsion
hook (Fig. 93E) almost heart-shaped, covered densely with short, thick spines; basal tube (Fig.
93B) composed of a thick, rod-like structure, and its posterior part just overlapped with inner sac
where scale-like denticles are densely arranged (when seen ventrally). Parameres (Fig. 93D)
slender, straight; apical area hardly swollen mesially, and furnished mesially with 20 to 22 setae.
Female: Eighth ventrite obtusely angulate posteromedially; gonocoxites (Fig. 93H) eachangulate apicomedially, with apicolateral tooth thin, falciform, acutely pointed, apicolateral setae
long. Spermatheca (Fig. 93G) small, with capsule rounded apically; RT-duct moderately sclerotized, curved; spermathecal duct very short; basal valve invisible; basal pouch almost coneshaped.
Biology and Ecology. Stenus oliberbetzi is presently distributed only in the plains of Kanto
district, central Japan. The beetles inhabit moist litter of the grasses (e.g., reeds) grown at theshores of the rivers, lakes and marshes.
Remarks. Stenus oliverbetzi is allied to S. concinnus, but this species is separable from thelatter by the body distinctly narrower (Fig. 133I), the posterior segments of abdomen with punctures sparser, the aedeagal median lobe distinctly thicker and wider (Fig. 93D), the endophallic
basal tube thicker, composed of a rod-like structure (Fig. 93B); and the paramere shorter (Fig.
93D).

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237

Etymology. The speciﬁc epithet of this species is named in honour of a distinguished morphologist and coleopterist Dr. Oliver Betz (University of Tübingen, Tübingen).
Stenus hirtellus Sharp(Figs. 94A–H, 133J)
Stenus hirtellus Sharp, 1874: 86; Herman, 2001: 2214; Naomi & Puthz, 2013: 139; Puthz, 2013:
1362.
Type material examined. Syntypes: 2 ♂ (NHML), type locality: Orakami Marsh, Nagasaki[examined by Puthz in 1969].
Other material examined. [MALAYSIA]: 1 ♂2 ♀, Tapah, 27. ii. 1974, Y. Kiyoyama leg.
Distribution. Japan (Kyushu); China, Taiwan, Malaysia.
Redescription. Male and female: Macropterous; body 3.4–3.6 mm (fore body 1.7–1.8 mm) in
length, strongly shining, furnished sparsely with long, suberect setae (Fig. 133J), antennae short.
Body dark red to black; labrum dark red; antennae with basal segments yellowish brown, apicalsegments dark brown; legs yellowish brown to reddish brown, with knees infuscate. Head small,with a pair of narrow longitudinal depressions, ﬁve smooth, lustrous areas (two areas are behindantennal tubercles; other two areas at posterolateral parts of vertex; and the other area at posteromedian area between eyes); punctures round to elliptical, dense. Pronotum with surface almost
even, with a median longitudinal area impunctate; punctures moderately round, dense to very
dense, distinct. Elytra large, arcuately emarginate posteriorly; surface almost even, similarly
punctate as on pronotum. Legs moderately long; femora and tibiae sparsely with long, suberectsetae; tarsi short, 3rd tarsomere weakly, asymmetrically bilobed, with its mesial lap longer thanlateral one, 4th tarsomere strongly bilobed. Abdomen cylindrical, sparsely with long, suberectsetae (Fig. 94F); 9th tergum (Fig. 94A) with a cleaning comb; punctures round, dense andmedium-sized in 3rd segment, while punctures in other posterior segments round, sparse andvery small to small. Lateroventrites and tergo-ventrite sutures completely missing on abdomen.
Male: Fifth ventrite (Fig. 94F) densely punctate posteromedially; 6th ventrite (Fig. 94F) posteromedially with a shallow depression which is densely punctate and very shallowly emarginate
posteriorly; 7th ventrite (Fig. 94F) posteromedially with a relatively small, shallow depression,
which is densely punctate and pubescent, and also very shallowly emarginate posteriorly; 8th tergum truncate posteriorly (Fig. 94H); 8th ventrite (Fig. 94F) strongly narrowed posteriorly, posteromedially with a small, V-shaped emargination; 9th tergum (Fig. 94A) with ventral apophyses
thin, very long; 9th ventrite (Fig. 94G) with apicolateral teeth falciform, thin, acute; 10th tergum(Fig. 94A) moderately narrowed apically. Aedeagal median lobe (Fig. 94B) fusiform, strongly
narrowed apically behind the middle, obtusely pointed apically, and in addition very unique inhaving the basilateral sclerotized ﬂaps and lateral subtransparent ﬂaps in basal 2/3. Endophallic
median longitudinal bands (Fig. 94D) narrow, short; expulsion hooks (Fig. 94D) each very thin,rod-like, weakly curved laterally at anterior and posterior ends; basal tube (Fig. 94D) large, basal
room with distinct basal constriction, tube body rod-like, curved twice dorsoventrally; inner sac(Fig. 94D) covered densely with small tubercles. Parameres (Fig. 94B) thin, weakly incurved;
apical area rather short, weakly swollen laterally, and furnished with 14 to 16 short setae along
the mesial margin.
Female: Eighth ventrite rounded posteriorly; gonocoxites (Fig. 94E) each angulate apicomesially, with apicolateral tooth falcate, slender, acutely pointed. Spermatheca (Fig. 94C) entirely

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Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

Fig. 94. Stenus hirtellus Sharp (Tapah, Malaysia). A, 9th and 10th terga of male; B, aedeagus; C, spermatheca;
D, endophallic structures; E, 5th to 8th ventrites of male; F, apex of gonocoxite; G, 9th ventrite of male; H,
8th tergum of male. Scale 1: 0.2 mm for A, B, G, H, 0.1 mm for C–E; scale 2: 0.3 mm for F.

submembranous (i.e., not differentiated into capsule, RT-duct and spermathecal duct), its duct
short with 2 turns; basal pouch conical.
Biology and Ecology. In Japan Stenus hirtellus was probably collected only once from

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239

Orakami Marsh, Nagasaki Pref. in the second half of 19th century; and after that no additional
beetles have been collected, showing that this is a very rare Stenus species. The collecting
records suggest that the beetles probably inhabit moist litter of the grasses grown at the shores oflakes and marshes.
Remarks. Stenus hirtellus is allied to S. oblitus and S. piliferus, but this species is easily separable from the latter two species by the body covered sparsely with long, suberect setae (Fig.
94F); and the aedeagal median lobe with its basal and lateral ﬂaps in basal 2/3 (Fig. 94B).
Stenus oblitus Sharp(Figs. 95A–F, 133K)
Stenus oblitus Sharp, 1874: 87; Herman, 2001: 2308; Naomi & Puthz, 2013: 139.
Type material examined. Syntype: ♀ (NHML), type locality: Kobe, Japan [examined by Puthz
in 1969].
Other material examined. [HOKKAIDO]: 1 ♂, Takkobu Pond, Kushiro Marsh, 11. vi. 1990,
R. Kuranishi leg. [HONSHU]: 3 ♂5 ♀, Shimoyashi, Sendai City, Miyagi Pref., 8. viii. 1994, H.
Yoshitake leg.; 1 ♀, Numata, Gunma Pref., 15. v. 1951, T. Takei leg.; 1 ♀, Yaita City, Tochigi
Pref., 22. viii. 1987, K. Sato leg.; 1 ♂, Imori, Saitama Pref., 11. v. 1994, K. Ohgi leg.; 1 ♀, Mt.
Takao, Hachioji, Tokyo Metropolis, 16. ix. 1960, Y. Shibata leg.; 1 ex., Jinbei-Ohashi, Inbanuma, Chiba Pref., 28. iii. 1990, T. Takeda leg.; 2 ♂, Kamishiro, Nagano Pref., 16. vi. 1960, Y.
Shibata leg.; 1 ♀, Shimonogo, Ueda City, Nagano Pref., 17. vi. 1990, K. Sugiyama leg.; 1 ♂1 ♀,Gakuda-cho, Aichi Pref., 22. ix. 1993, R. Kuranishi leg.; 1 ♂, Tako, Onsen-cho, Hyogo Pref., 8-9.
x. 1992. [KYUSHU]: 1 ♂, Ukiha-cho, Fukuoka Pref., 14. vi. 1950, N. Gyotoku leg.
Distribution. Japan (Hokkaido, Honshu, Kyushu); Korea, China, Russia, Vietnam.
Redescription. Male and female: Macropterous; body 2.8–4.0 mm (fore body 1.5–1.8 mm) in
length, shining, with antennae relatively short. Body black; labrum dark red; antennae with basal
segments yellowish brown, apical segments dark brown; legs yellowish brown to reddish brown,
but apical part of femur and apical half of tibia dark brown. Head small, with a pair of narrow
longitudinal depressions, and ﬁve smooth, lustrous areas (two areas are behind antennal tubercles; two areas at posterolateral parts of vertex; and the other area located at posteromedian part
between eyes are large, elongate and weakly swollen); punctures round to elliptical, dense. Pronotum with surface almost even, with a median longitudinal area which is impunctate but indistinct in outline; punctures round, very dense, distinct. Elytra large, arcuately emarginate posteriorly; surface almost even, similarly punctate as on pronotum. Legs moderately long; tarsi short,
3rd tarsomere weakly, asymmetrically bilobed, with its mesial lap longer than lateral one, 4th tarsomere strongly bilobed. Abdomen cylindrical; punctures round to elliptical, very dense and distinct in anterior segments, while punctures in posterior segments sparse and very small. Lateroventrites and tergo-ventrite sutures completely missing on abdomen.
Male: Sixth ventrite (Fig. 95A) sparsely pubescent on posteromedian area, which is very
shallowly emarginate; 7th ventrite (Fig. 95A) posteromedially with a bell-shaped, ﬂat area,
which is very shallowly emarginate; 8th ventrite (Fig. 95A) distinctly narrowed posteriorly, posteromedially with a V-shaped emargination; 9th tergum (Fig. 95C) with ventral apophyses thin,very long, straight; 9th ventrite (Fig. 95D) widest a little before the middle, bisinuate at posterior
margin, with apicolateral teeth short, acutely pointed, apicolateral setae very long; 10th tergum(Fig. 95C) very weakly emarginate posteriorly. Aedeagal median lobe (Fig. 95B) elongate, dis-240

Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

Fig. 95. Stenus oblitus Sharp (A–D, Ukiha, Fukuoka; E, F, Shimoyashi, Miyagi). A, 6th to 8th ventrites of male;B, aedeagus; C, 9th and 10th terga of male; D, 9th ventrite of male; E, 9th and 10th terga of female; F, gonocoxite. Scale 1: 0.3 mm for A; scale 2: 0.2 mm for B–E, 0.1 mm for F.

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241

tinctly bulbous basally with a constriction at its posterior part, and acutely pointed apically, withapical sclerotized area almost triangular in shape. Endophallic median longitudinal bands? (Fig.
95B) indistinct, located posterolaterally to the inner sac; expulsion hooks (Fig. 95B) paired, verysmall; basal tube? (Fig. 95B) discernible only at its apical part, which is located in the posteromedian part of inner sac; inner sac (Fig. 95B) widened apically, and covered with lines of smalltriangular spines around the posterior 4/5, and also with very small tubercles in most area of theanterior portion. Parameres (Fig. 95B) thin, slender and rounded apically, each gently, uniformly
incurved but weakly curved laterally behind the base of apical area; apical area widened dorsoventrally, and furnished with 30 to 35 short setae along the mesial margin.
Female: Eighth ventrite rounded posteriorly; 9th tergum (Fig. 95E) without ventral apophyses; 10th tergum (Fig. 95E) very weakly emarginate posteriorly; gonocoxites (Fig. 95F) eachrounded apicomesially, with apicolateral tooth pointed, apicolateral setae long. Spermatheca notobservable.
Biology and Ecology. Stenus oblitus is distributed in the plains and low mountainous regionsin Japan. The beetles inhabit litter of the grass lands and natural forests, but they also often livein moist litter of the grasses grown at the shores of the rivers and marshes.
Remarks. Stenus oblitus is allied to, and also similar in external structure to S. piliferus, but
this species is separable from the latter by the body narrower and smaller on average (2.8–4.0mm), the 8th ventrite of male posteromedially with a shallower emargination (Fig. 95A), the 9th
ventrite of male with apicolateral tooth shorter (Fig. 95D), and the aedeagal median lobe simply
pointed apically (Fig. 95B).
Stenus piliferus Motschulsky(Figs. 96A–F, 133L)
Stenus piliferus Motschulsky, 1857: 514; Naomi, 1997b: 746; Herman, 2001: 2339; Naomi &Puthz, 2013: 139; Puthz, 2013: 1362.
Type material. Type locality: Indes orientales.
Other material examined. [NANSEI ISLS.]: 2 ♂3 ♀, Sonai, Iriomote Is., Okinawa Pref., 5.
viii. 1985, K. Sugiyama leg.; 2 ♂3 ♀, Nakano, Iriomote Is. Okinawa Pref., 29. iv. 1998, K.
Toyoda leg. [TAIWAN]: 2 ♀ (cS), Taiwan, Ilan Hsien, Shen-Mi Lake, 1110 m, 9. v. 1995, A.
Smetana leg.
Distribution. Japan (Nansei Isls.: Iriomote Is.); China, Oriental region, Australia, Bismarck
Isls.
Redescription. Male and female: Macropterous; body 3.6–4.2 mm (fore body 1.7–2.1 mm) in
length, robust, shining, with antennae relatively short. Body black; labrum dark red; antennae
yellowish brown to reddish brown; legs yellowish brown to reddish brown, but apical part offemur and apical half of tibia often dark brown (Fig. 133L). Head rather small, with a pair of narrow longitudinal depressions, and ﬁve smooth, lustrous areas (located as in S. oblitus); puncturesround, dense, small. Pronotum with surface almost even, densely punctate, with median longitudinal lustrous area and also several small, lateral lustrous areas. Elytra large, arcuately emarginate posteriorly; surface almost even, with punctures round, very dense, distinct. Legs moderately
long; tarsi short, with 3rd and 4th tarsomeres similarly bilobed as in S. oblitus. Abdomen cylindrical, narrowed posteriorly; punctures round, very dense and distinct in anterior segments, while
punctures in posterior segments sparse to moderately dense and very small. Lateroventrites and242

Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

Fig. 96. Stenus piliferus Motschulsky (A–E, Sonai, Iriomote Is.; F, Nakano, Iriomote Is.). A, 9th and 10th tergaof male; B, 9th ventrite of male; C, aedeagus; D, 6th to 8th ventrites of male; E, 8th tergum of male; F, apexof gonocoxite. Scale 1: 0.2 mm for A–C, E, 0.1 mm for F; scale 2: 0.3 mm for D.

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tergo-ventrite sutures completely missing on abdomen.
Male: Sixth ventrite (Fig. 96D) posteromedially with a semicircular ﬂat area, which issparsely pubescent and very shallowly emarginate posteriorly; 7th ventrite (Fig. 96D) posteromedially with an elongate-bell-shaped, ﬂat area, which is pubescent and very shallowly emarginate
posteriorly; 8th tergum (Fig. 96E) almost truncate posteriorly; 8th ventrite (Fig. 96D) distinctly
narrowed posteriorly, posteromedially with a deep V-shaped emargination; 9th tergum (Fig. 96A)
with ventral apophyses thin, very long, straight; 9th ventrite (Fig. 96B) widest near the middle,
densely pubescent only posteromedially, with apicolateral teeth thin, pointed apically, apicolateral setae very long; 10th tergum (Fig. 96A) very weakly emarginate posteriorly. Aedeagal
median lobe (Fig. 96C) almost elongate-ovoidal in basal 3/4, with the very long, lanceolate apicomedian projection. Endophallic median longitudinal bands (Fig. 96C) very short, narrow;
expulsion hooks (Fig. 96C) located anteriorly to the median longitudinal bands, strongly sclerotized; basal tube (Fig. 96C) discernible only at its apical part, which is located in the posteromedian part of inner sac; inner sac (Fig. 96C) large, comprising two lateral longitudinal areas which
are covered posteriorly with small-triangular spines, and also anteriorly with very small tubercles. Parameres (Fig. 96C) slender, each gently incurved before the middle; apical area long, andfurnished mesially with 23 to 26 setae of moderate length.
Female: Eighth ventrite rounded posteriorly; gonocoxites (Fig. 96F) each with apicolateral
tooth long, thin, apicolateral setae very long. Spermatheca not observable.
Biology and Ecology. Stenus piliferus is widely distributed in the East Asia, Southeast Asia
and Australia, but in Japan it is presently distributed only in the plains of Iriomote Is. The beetles
inhabit moist litter of the grasses grown at the shores of rivers and wetlands (see also Puthz,2013).
Remarks. Stenus piliferus is presently classiﬁed into 8 subspecies on the basis of such characters as aedeagus, punctuation of elytra, coloration of legs, microsculpture of abdomen, etc.
(Puthz, 1972a; Puthz, 1994). Of these subspecies, the nominotypical one only is distributed inJapan; and it was ﬁrst recorded from Japan by Naomi (1997b). This species is allied to, and alsosimilar in external structure to S. oblitus, but it is separable from the latter by the body wider andlarger on average (3.6–4.2 mm), the 8th ventrite of male posteromedially with a deeper emargination (Fig. 96D), the 9th ventrite of male with apicolateral tooth longer (Fig. 96B), and theaedeagal median lobe with the very long, lanceolate apicomedian projection (Fig. 96C).
Species group of S. rorellus Fauvel
S. rorellus group (＝S. cursorius group) consists of 2 species in Japan; see Puthz (1972a,
2013) regarding a review and characterization of this group; and see Puthz (2013) regarding a
key to the Oriental species of this group. Diagnostic characters are as follows: Body matt (Fig.
134A) or weakly shining (Fig. 134B), covered with very dense punctures; head with vertex wideto very wide; antennae short; pronotum short; legs with 4th tarsomere strongly bilobed; lateroventrites and tergo-ventrite sutures completely missing on abdomen; 9th tergum posteriorly witha cleaning comb (Fig. 97B, C); 9th ventrite of male strongly serrate posteriorly, without apicolateral tooth (Fig. 97A); 10th tergum widely emarginate posteriorly, apicolaterally with a small
tooth (Fig. 97B, C); aedeagus narrowed apically to pointed apex, with inner sac furnished withspicules, etc. (Fig. 97F); gonocoxite strongly serrate posteriorly, without apicolateral tooth (Fig.
97E); spermatheca not sclerotized.

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Key to the Japanese species of S. rorellus group1(2) Body larger (2.7–3.1 mm), matt; antenna with 1st segment reddish brown; 10th tergum lessdeeply emarginate posteriorly (Fig. 97B, C); aedeagal median lobe wider (Fig. 97F)...................................................................................................................... S. confertus Sharp
2(1) Body smaller (2.3–2.8 mm), weakly shining; antenna with 1st segment black; 10th tergum
more deeply emarginate posteriorly (Fig. 98B, E); aedeagal median lobe narrower (Fig.
98F) .............................................................................................................. S. dissimilis Sharp
Stenus confertus Sharp(Figs. 97A–F, 134A)
Stenus confertus Sharp, 1889: 331; Herman, 2001: 2138; Naomi & Puthz, 2013: 139; Puthz,
2013: 1314.
Stenus cribellatus Motschulsky, 1857: Puthz, 1973c: 51 (as synonym of S. cribellatus).
Type material examined. Lectotype: ♂ (NHML), paralectotype: ♂ (NHML), type locality:
Sanjyo, Japan, 3. ix. 1881, Lewis. [examined by Puthz in 1969 and designated by Puthz, 1973].
Other material examined. [CHINA]: 1 ♂1 ♀, Caota Town, Zhuji City, Zhejiang Prov., 29. x.
2011, Zhao Tie-Xiong leg.
Distribution. Japan (Honshu); China.
Redescription. Male and female: Macropterous; body 2.7–3.1 mm (fore body 1.5–1.6 mm) in
length, matt, with short antennae. Body black but pronotum and elytra with a reddish tint; labrum
black; antennae reddish brown but 3 to 4 apical segments infuscate; legs pale yellowish brown toreddish brown, with knees infuscate. Head small, concave dorsally, weakly depressed alongmesial margin of eye, median area between the depressions weakly convex; punctures round,very dense, distinct. Pronotum with surface almost even; punctures round, very dense, strong.
Elytra well-convex dorsally but shallowly impressed at the basal 1/3 of suture, with humeri
developed; surface similarly punctate as on pronotum but punctures a little larger than on it. Legs
short; tarsi short, with 4th tarsomere strongly bilobed. Abdomen cylindrical, distinctly narrowed
posteriorly; punctures round, very dense and regular, but punctures becoming gradually smaller
posteriorly toward 8th segment; 9th tergum posteriorly with a cleaning comb, which is composedof a regular line of thick, straight setae of same length (Fig. 97B, C); 10th tergum widely emarginate posteriorly, apicolaterally with a short, acute tooth at each side (Fig. 97B, C). Lateroventrites and tergo-ventrite sutures completely missing on abdomen.
Male: Seventh ventrite posteromedially with a shallow, bell-shaped depression, which isshallowly emarginate posteriorly; 8th ventrite (Fig. 97D) posteromedially with a subtriangularemargination; 9th tergum (Fig. 97B) with apicolateral ﬂaps small, ventral apophyses long; 9th
ventrite (Fig. 97A) widely emarginate posteriorly, strongly serrate at posterior margin, with stem
almost submembranous, apicolateral setae moderately long. Aedeagal median lobe (Fig. 97F)
elongate-ovoidal in shape, gently rounded apicolaterally, and acutely pointed apically, with apicolateral rim wide, strongly sclerotized (when seen ventrally). Endophallic median longitudinalbands (Fig. 97F) relatively short, very thin; lateral longitudinal bands (Fig. 97F) very short andthin; expulsion hooks existing as paired very thin, stick-like structures located between the
median bands (Fig. 97F); basal tube existing as a densely spiculose ﬂexible tube (Fig. 97B)
which is thick and thrice bent. Parameres (Fig. 97F) extending posteriorly a little before the apex

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245

Fig. 97. Stenus confertus Sharp (Zhuji, China). A, 9th ventrite of male; B, 9th and 10th terga of male; C, 9th and10th terga of female; D, 8th ventrite of male; E, gonocoxites; F, aedeagus. Scale 1: 0.1 mm for A, E, 0.2 mm
for D; scale 2: 0.1 mm for B, C, F.

of median lobe; each moderately constricted near the middle; apical area short, hardly swollen
mesially, and furnished mesially with about 12 to 14 setae.
Female: Eighth ventrite gently rounded posteriorly; gonocoxites (Fig. 97E) each strongly serrate posteriorly, with long apicolateral setae, without distinct apicolateral tooth; 10th tergum (Fig.
97C) more strongly narrowed posteriorly than in male. Spermatheca not observable.
Biology and Ecology. In Japan Stenus confertus was collected only once by. G. Lewis from246

Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

Sanjo (2 exs., 3. ix. 1881) in the late 19th century; and after that, no additional beetles have beencollected, showing that this is a very rare Stenus species. We have no data regarding the habitatsof this species in Japan.
Remarks. Stenus confertus was ﬁrst described by Sharp (1889). The name of this species wasonce synonymized with S. cribellatus Motschulsky, 1857 by Puthz (1973c), but it was resurrected as valid by Puthz (2013). This species is closely allied to S. kubani Puthz, 2013 from Laos,but it is separable from the latter by the body smaller in average (2.7–3.1 mm), the 7th tergum
with denser punctures, the aedeagal median lobe weakly rounded apicolaterally, with the spiculose, ﬂexible basal tube which is longer and thrice bent (Fig. 97F). Among the Japanese membersof this group, S. confertus is similar to S. dissimilis, but this species is easily separable from thelatter by the 1st segment of antenna reddish brown and the 10th tergum less deeply emarginate
posteriorly (Fig. 97B, C).
Stenus dissimilis Sharp(Figs. 98A–F, 134B)
Stenus dissimilis Sharp, 1874: 87; Herman, 2001: 2162; Naomi & Puthz, 2013: 139; Puthz, 2013:
1315.
Type material examined. Holotype: ♂ (NHML), type locality: Japan [examined by Puthz in1969].
Other material examined. [HONSHU]: 1 ♀, Nomikanayama, Chonan-machi, Chiba Pref., 5.
vii. 1989, S. Naomi leg.; 1 ♀, Tsurumi-ku, Yokohama City, Kanagawa Pref., 4. viii. 1984, M. Taoleg.; 1 ♀, Sato, Mikura Is., Izu Isls., Tokyo Metropolis, 15. v. 2013, H. Kamezawa leg.; 1 ♂,Mukogawa, Hyogo Pref., 14. vi. 1939, K. Taniguchi leg. [SHIKOKU]: 1 ♀, Nishinokawa,Tosashimizu City, Kochi Pref., 10. iii. 2007, T. Miyata leg.; 1 ♀, Daimyojika, Shimanto City,
Kochi Pref., 10. ii. 2008, T. Miyata leg. [KYUSHU]: 1 ♀, Kueyama, Shimabara, Nagasaki Pref.,27. iii. 1979, S. Imasaka leg. [NANSEI ISLS.]: 1 ♂1 ♀, Nagata, Yaku Is., Kagoshima Pref., 7. iv.
1965, M. Yasui leg.; 1 ♀, Mt. Megami, Takara Is., Tokara, Kagoshima Pref., 25. iii. 1992, S.
Nomura leg.; 1 ♀, Mt. Yuwan, Amami Is., Kagoshima Pref., 5. v. 1987, S. Nomura leg.; 1 ♀, Shirase River, Kume Is., Okinawa Pref., 14-16. iii. 1998, M. Maruyama leg.; 1 ♀, Ishigaki Is., Okinawa Pref., Jan. 1998-Dec. 1999, K. Takahashi leg.; 1 ♀, same locality, 31. vii.- 19. x. 1995, K.
Takahashi leg.; 1 ♂, Mt. Omoto, Ishigaki Is., Okinawa Pref., 18. iii. 1997, K. Toyoda leg.; 1 ♂,same locality, 17. iii. 1978, S. Naomi leg.; 1 ♀, same locality, 20. iii. 1978, S. Naomi leg.; 1 ♀,Mt. Banna, Ishigaki Is., Okinawa Pref., 15. iii. 1978, S. Naomi leg.
Distribution. Japan (Honshu, Shikoku, Kyushu; Mikura Is., Nansei Isls.); Taiwan, China.
Redescription. Male and female: Macropterous; body 2.3–2.8 mm (fore body 1.3–1.5 mm) in
length, weakly shining, with short antennae. Body dark brown to black; labrum black; antennae
with 1st segment black, remaining segments yellowish brown to reddish brown; legs pale yellowish brown to reddish brown, with knees infuscate. Head widely but shallowly depressed dorsally, but the depressed area between eyes almost ﬂat; punctures round, very dense, distinct. Pronotum with surface weakly uneven; punctures round, very dense, strong. Elytra well-convex
dorsally; surface similarly punctate as on pronotum. Legs short; tarsi short, with 4th tarsomere
strongly bilobed. Abdomen cylindrical, narrowed posteriorly; punctures round, very dense andregular, but punctures becoming gradually smaller posteriorly toward 8th segment; 9th tergum
posteriorly with a cleaning comb (Fig. 98B, E); 10th tergum widely, moderately deeply emargin-

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Fig. 98. Stenus dissimilis Sharp (Yaku, Kagoshima). A, 7th to 8th ventrites of male; B, 9th and 10th terga offemale; C, gonocoxites; D, 9th ventrite of male; E, 9th and 10th terga of male; F, aedeagus. Scale 1: 0.2 mm
for A; scale 2: 0.1 mm for B, E, F; scale 3: 0.1 mm for C, D.

ate posteriorly, apicolaterally with an acute tooth at each side (Fig. 98B, C). Lateroventrites andtergo-ventrite sutures completely missing on abdomen.
Male: Seventh ventrite (Fig. 98A) medially with a large, elongate-subovoidal depression,
which is moderately deep and shallowly emarginate; 8th ventrite (Fig. 98A) anteromedially witha very shallow, subovoidal depression, and posteromedially with a wide emargination; 9th tergum (Fig. 98E) with anterolateral ﬂaps rounded, ventral apophyses very long; 9th ventrite (Fig.
98D) widely emarginate and also strongly serrate posteriorly, with stem quadrangular in shape,

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Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

apicolateral setae moderately long. Aedeagal median lobe (Fig. 98F) slender, angulate at apicolateral corners, and very acutely pointed apically. Endophallic median longitudinal bands (Fig.
98F) relatively short, diverging anteriorly; expulsion hook (Fig. 98F) U-shaped; basal tube (Fig.
98F) comprising a simple rod wrapped by the inner sac which is posteriorly covered with dense
spinules. Parameres (Fig. 98F) slender, almost straight; apical area short, weakly swollen mesially, and furnished mesially with 9 to 10 sparse setae of various length.
Female: Eighth ventrite gently rounded posteriorly; gonocoxites (Fig. 98C) each strongly
serrate posteriorly, with apicolateral setae moderately long; 10th tergum (Fig. 98B) a little morestrongly narrowed posteriorly than in male. Spermatheca not observable.
Biology and Ecology. S. dissimilis is a relatively rare Stenus species in Japan; and the beetles
inhabit leaf litter in or near the shrubs and forests of plains and low mountainous regions. The
beetles were collected by car-net trap in Ishigaki Is., Okinawa.
Remarks. Stenus dissimilis is closely allied to S. bicuspis Puthz, 1983 from Vietnam, but thisspecies is separable from the latter by the elytra smaller and the lateral part of 10th tergum
rounded (Fig. 98B, E). Among the Japanese members of this group, S. dissimilis is similar to S.
confertus, but this species is easily separable from the latter by the 1st segment of antenna blackand the 10th tergum more deeply emarginate posteriorly (Fig. 98B, E).
Species group of S. similis (Herbst)
S. similis group consists of 7 species in Japan; see Puthz (2008a) regarding a taxonomic
information of this group and a key to the species of S. cicindeloides complex. Diagnostic characters are as follows: Body robust, with cylindrical abdomen (Fig. 134C); legs with 3th tarsomere more or less emarginated posteriorly, 4th tarsomere strongly bilobed; lateroventrites andtergo-ventrite sutures missing on abdomen; aedeagal median lobe more or less pointed apically(Fig. 99B), with endophallic basal tube thick (Fig. 103A); spermatheca not observable.
The Japanese members of this group will be divided into two subgroups on the basis of themorphology of 9th ventrite of male, gonocoxite, etc. in the following way: (1) S. bohemicus andS. aquilonalis: 9th ventrite of male with stem elongate and narrow, apicolateral teeth missing;gonocoxite without (distinct) apicolateral teeth (if present it is very small); and aedeagal median
lobe simply pointed apically; and (2) S. sedatus, S. weisei, S. mercator, S. cicindeloides and S.
kiesenwetteri: 9th ventrite of male with stem wide, mostly transverse, more or less constrictedbasally, and widely emarginate anteriorly (or projecting anterolaterally; or bilobed), with apicolateral teeth distinctly pointed; gonocoxite with distinct apicolateral teeth; aedeagal median lobe
pointed apically but also with a small globe or tubercle at the apicalmost part.
Key to the Japanese species of S. similis group1(4) Antennae with 1st segment dark brown to black; 9th ventrite of male with stem elongate,apicolateral teeth missing (Fig. 99C).
2(3) Eighth ventrite of female with posteromedian projection shorter, rounded (Fig. 99H); 9th
ventrite of male rounded posteriorly (Fig. 99C); 10 tergum longer, more strongly narrowed
apically (Fig. 99A); aedeagal paramere distinctly longer (Fig. 99B).........................................
............................................................................................................. S. bohemicus Machulka
3(2) Eighth ventrite of female with posteromedian projection longer, pointed (Fig. 100F); 9th
ventrite of male widely emarginate posteriorly (Fig. 100B); 10 tergum shorter, less strongly

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249

narrowed apically (Fig. 100A); aedeagal paramere distinctly shorter (Fig. 100C)................................................................................................... S. aquilonalis Naomi & Puthz
4(1) Antennae with 1st segment yellowish brown; 9th ventrite of male with stem wide, widened
anteriorly, apicolateral teeth pointed (Fig. 104A).
5(8) Abdomen covered with relatively long, suberect pubescence.
6(7) Body more slender (Fig. 134F); aedeagal median lobe with apicolateral part gently rounded(Fig. 102A, B); endophallic expulsion hook simply narrowed apically (Fig. 102F, G); basal
tube narrowed apically (Fig. 102E) ................................................................. S. sedatus Sharp
7(6) Body thicker and wider (Fig. 134G); aedeagal median lobe with apicolateral part almost
straight (Fig. 103A, B); endophallic expulsion hook weakly spatulate apically (Fig. 103A,
H); basal tube gradually widened apically (Fig. 103A, D) ........................S. weisei Bernhauer
8(5) Abdomen covered with very short, decumbent pubescence.
9(12) Elytra without colored maculae; 5th and 6th ventrite of male without modiﬁcations.
10(11) Body thinner, narrower (Fig. 134E), and black in coloration with weak greenish reﬂection; pronotum and elytra with punctures smaller .....................................S. mercator Sharp
11(10) Body thicker, wider (Fig. 134H), and simply black in coloration; pronotum and elytra
with punctures larger ....................................................................S. cicindeloides (Schaller)
12(9) Elytra with a pair of reddish maculae; 5th and 6th ventrite of male each posteromediallywith a depression (Fig. 105A) .....................................................S. kiesenwetteri Rosenhauer
Stenus bohemicus Machulka(Figs. 99A–H, 134C)
Stenus bohemicus Machulka, 1947: 88; Herman, 2001: 2094; Naomi & Puthz, 2013: 139.
Type material. Type ♂, type locality: Bohemia mer.: Veselí n. Lužnicí.
Other material examined. [HOKKAIDO]: 1 ♂3 ♀, Ashoro, 25. vi. 1986, K. Morimoto leg.;1 ♂6 ♀, Nakayama Pass, 22. vi. 1986, K. Morimoto leg.; 1 ♂, Harutori, Kushiro City, 9. vii.
1998, T. Matsumoto leg.; 1 ♀, Yubetsu River, Engaru, 27. vii. 1999, S. Ohmomo leg.; 1 ♀, Obihiro City, 6. vi. 1980, H. Togawa leg.; 1 ♂5 ♀, Iwabokki, Kushiro Moor, 25. viii. 1990, M. Satoleg.; 1 ♂4 ♀, Kirakotan, Kushiro Moor, 25. viii. 1990, M. Sato leg.; 1 ♂2 ♀, Akanuma, Kushiro
Moor, 25. viii. 1990, M. Sato leg.; 1 ♀, Shirarutoro, Kushiro Moor, 24. viii. 1990, M. Sato leg.;1 ♂, same locality, 11. vi. 1990, R. Kuranishi leg.; 1 ♀, same locality, 4. vi. 1991, R. B. Kuranishi
leg.; 1 ♀, Guchian. [HONSHU]: 2 ♂2 ♀, Kasamatsu, Towadako-machi, Aomori Pref., 2. viii.
1998, H. Yoshitomi leg.; 1 ♀, Sukayu Spa, Aomori City, Aomori Pref., 2. viii. 1998, A. Ishizuka
leg.
Distribution. Japan (Hokkaido, Honshu: Aomori Pref.); Korea, China, Mongolia, Europe.
Redescription. Male and female: Macropterous; body 4.0–5.3 mm (fore body 2.1–2.7 mm) in
length, weakly shining, covered with short, silvery pubescence, with antennae short. Body
entirely black; labrum black; antennae with 1st and also 2 or 3 apical segments dark brown,
remaining segments clear yellow to yellowish red; legs black but tarsi reddish brown. Head notconcave dorsally, with a pair of elongate depressions, median area between the depressions
weakly convex, and a little higher in level than mesial margin of eye; punctures round, very
dense, small, distinct. Pronotum distinctly narrower than elytra; surface behind the middle with apair of oblique, shallow furrows which converge posteriorly; punctures round to almost round,very dense. Elytra large, shallowly impressed around the basal half of suture, with humeri devel-

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Fig. 99. Stenus bohemicus Machulka (A, Akanuma, Hokkaido; B–E, G, Iwabokki, Hokkaido; F, H, Guchian,
Hokkaido). A, 9th and 10th terga of male; B, aedeagus; C, 9th ventrite of male; D, endophallic basal tube; E,
5th to 8th ventrites of male; F, gonocoxite; G, expulsion hooks; H, apex of 8th ventrite of female. Scale 1: 0.2
mm for A–C, H, 0.1 mm for D; scale 2: 0.5 mm for E; scale 3: 0.2 mm for F, 0.1 mm for G.

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oped; surface similarly punctate as on pronotum. Legs moderately long; tarsi with 3th tarsomere
widely emarginate posteriorly, 4th tarsomere strongly bilobed. Abdomen cylindrical, weakly narrowed posteriorly, 3rd tergum with a short, basimedian keel; punctures round, moderately dense
to dense, small and somewhat irregular in anterior segments, while punctures in posterior segments round, very dense, small and almost regular. Lateroventrites and tergo-ventrite suturescompletely missing on abdomen.
Male: Fifth ventrite (Fig. 99E) posteromedially with a very shallow emargination; 6th ventrite (Fig. 99E) posteromedially with a shallow emargination and also a very narrow, depressedarea along the emargination; 7th ventrite (Fig. 99E) without modiﬁcation; 8th ventrite (Fig. 99E)
posteromedially with a wide emargination; 9th tergum (Fig. 99A) elongate, with ventral apophyses thick, weakly spatulate apically; 9th ventrite (Fig. 99C) elongate, rounded posteriorly, withstem elongate-rectangular in shape, with apicolateral setae short, apicolateral teeth missing; 10th
tergum (Fig. 99A) elongate, rounded posteriorly. Aedeagal median lobe (Fig. 99B) relatively
short, bulbous basally, then strongly narrowed apically toward the acutely pointed apex, with apical sclerotized area ventrally with median longitudinal keel, and lateral rim narrow but distinctly
declivent (when seen ventrally). Endophallic median longitudinal bands (Fig. 99B) very long,reaching anteriorly the posterior margin of basal room; lateral longitudinal bands (Fig. 99B)
short, thin; expulsion hooks (Fig. 99B, G) comprising the paired elongate sclerites; basal tube
(Fig. 99B) robust, basal room connected with a basal-ring-like structure, tube body thick, withsclerotized ventral rims, and a V-shaped sclerite nested within the basal tube (Fig. 99D); innersac (Fig. 99B) visible with the areas which are covered densely with small spicules along the lateral margins of tube body. Parameres (Fig. 99B) very long, straight, and extending posteriorly
much beyond the apex of median lobe; apical area subtriangular, and furnished mesially with 13
to 15 short setae, and 7 to 8 setae of moderate length at the mostapical part.
Female: Eighth ventrite (Fig. 99H) posteromedially with a short, round projection; gonocoxites (Fig. 99F) each angulate apicomesially, rounded apicolaterally, with apicolateral setae moderately long; 10th tergum elongate, rounded posteriorly. Spermatheca not observable.
Biology and Ecology. Stenus bohemicus is distributed in the plains and low mountainous
regions. The beetles live under dead leaves near the watersides; and they occasionally climb thegrasses (such as Carex) and ramble along the leaves.
Remarks. Stenus bohemicus was ﬁrst discovered from Japan (Hokkaido) by Naomi (1990c);
and it is here ﬁrst discovered from Honshu (Aomori). This species is allied to S. tarsalis Ljungh,
1810, but it is separable from the latter by the body distinctly covered with silvery short pubescence, the elytra distinctly wider than pronotum, the 3rd tergum with a short, basimedian keel,
and the aedeagal paramere much longer (Fig. 99B) (Lohse, 1964). Among the Japanese membersof this group, S. bohemicus is allied to, and also very similar in external structure to S. aquilonalis, but it is separable from the latter by the 8th ventrite of female with posteromedian projection
shorter and rounded (Fig. 99H), the 9th ventrite of male rounded posteriorly (Fig. 99C), the 10
tergum longer (Fig. 99A), and the aedeagal paramere distinctly longer, with its apical area
smaller (Fig. 99B).
Stenus aquilonalis Naomi & Puthz(Figs. 100A–G, 134D)
Stenus aquilonalis Naomi & Puthz, 1997: 748; Herman, 2001: 2060; Naomi & Puthz, 2013: 139.

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Type material examined. Holotype: ♂ (CBM), Daisetsu Lake, Kamikawa, Hokkaido, 11. vi.
1993, N. Yasuda leg. Paratypes: 1 ♀ (cN), same locality as holotype; 1 ♂ (cN), Hoshino, Tochigi
City, Tochigi Pref., 25. ii. 1990, H. Yoshitomi leg.
Other material examined. [HOKKAIDO]: 2 ♀, Goshiki Spa, Niseko-machi, 12. vii. 1999.
[HONSHU]: 1 ♀, Okukinu River, Shioya-machi, Tochigi Pref., 20. vi. 1998, K. Sato leg.; 1 ♂,Koukawa, Daisen-cho, Tottori Pref., 25. ii. 1990, H. Yoshitomi leg.
Distribution. Japan (Hokkaido, Honshu); Russia (Sakhalin).
Redescription. Male and female: Macropterous; body 4.5–4.9 mm (fore body 2.5–2.7 mm) in
length, stout, weakly shining, covered with short, silvery pubescence, and with antennae short.
Body entirely black; labrum black; antennae with 1st and also apical 2 or 3 segments dark brown
to black, remaining segments yellowish brown to reddish brown; legs black but tarsi reddish
brown. Head not concave dorsally, with a pair of elongate depressions, median area between the
depressions weakly convex; punctures round, very dense, small, distinct. Pronotum with surface
behind the middle with a pair of oblique, shallow furrows which converge posteriorly; puncturesround to almost round, very dense, distinct. Elytra large, shallowly impressed around the basal
half of suture; surface similarly punctate as on pronotum, but punctures a little larger than thoseon it. Legs moderately long; tarsi with 3th tarsomere widely emarginate, 4th tarsomere strongly
bilobed. Abdomen cylindrical, 3rd tergum with a short, basimedian keel; punctures round, dense
and small in anterior segments, while punctures in posterior segments round to elliptical, very
dense, very small and regular. Lateroventrites missing, but only tergo-ventrite sutures existingand extremely thin on 4th to 6th segments.
Male: Seventh ventrite (Fig. 100G) posteromedially with a very shallow emargination; 8thventrite posteromedially with a simple, shallow emargination or a shallow bi-emargination (Fig.
100G); 9th tergum (Fig. 100A) with posterolateral projections long, ventral apophyses wide, subtriangular in shape; 9th ventrite (Fig. 100B) wide, parallel-sided, weakly angulate apicolaterally,
and widely emarginate posteriorly, with stem elongate, weakly apatulate apically, apicolateral
setae very long; 10th tergum (Fig. 100A) rounded posteriorly. Aedeagal median lobe (Fig. 100C)
weakly constricted at about basal 1/3, gently rounded apicolaterally, and acutely pointed apically;
apical sclerotized area ventrally with a median longitudinal keel. Endophallic median longitudinal bands (Fig. 100C) short, ventral bands each strongly sclerotized along mesial margin; expulsion hooks (Fig. 100C, E) paired, connected each other by a mesial corner; basal tube with basal
room small, tube body widened toward apex, thick (Fig. 100C) or very thick; inner sac (Fig.
100C) laterally covered with small spicules. Parameres (Fig. 100C) robust; stem with a sclerotized, longitudinal keel; apical area very large, hatchet-shaped, and ﬂat horizontally, and furnished with 13 to 15 setae of various length along mesial margin, with several long setae at theapicalmost part, and also with a few setae on the ventral surface, which is mesially covered with
dense, scale-like sculptures.
Female: Eighth ventrite (Fig. 100F) posteromedially with a short, pointed projection; gonocoxites (Fig. 100D) each angulate apicomesially, very ﬁnely serrate posteriorly, with apicolateral
tooth small, pointed, apicolateral setae very long. Spermatheca not observable.
Biology and Ecology. S. aquilonalis is a very rare Stenus species in Japan. The beetles live inthe vicinity of rivers and torrents running at the mountainous regions.
Remarks. Stenus aquilonalis is allied to S. bohemicus, but this species is separable from thelatter by the 8th ventrite of female with posteromedian projection longer and pointed (Fig. 100F),
the 9th ventrite of male wider, and shallowly emarginate posteriorly (Fig. 100B), the 10 tergum
shorter, and less strongly narrowed apically (Fig. 100A), and the aedeagal paramere distinctly

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Fig. 100. Stenus aquilonalis Naomi & Puthz (A–C, E, G, Hoshino, Tochigi; D, F, Daisetsu, Hokkaido). A, 9th
and 10th terga of male; B, 9th ventrite of male; C, aedeagus; D, gonocoxite; E, endophallic expulsion hooks;
F, 8th ventrite of female; G, 7th to 8th ventrites of male. Scale 1: 0.2 mm for A–C, F; scale 2: 0.2 mm for D,
0.1 mm for E; scale 3: 0.3 mm for G.

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shorter, with its apical area larger (Fig. 100C).
Stenus mercator Sharp(Figs. 101A–G, 134E)
Stenus mercator Sharp, 1889: 333; Herman, 2001: 2283; Naomi & Puthz, 2013: 139.
Type material. Syntypes (NHML), type locality: Junsai, Niigata.
Other material examined. [HOKKAIDO]: 2 ♀, Iwabokki, Kushiro Moor, 25. viii. 1990, M.
Sato leg.; 2 ♂1 ♀, same locality, 26. viii. 1990, M. Sato leg.; 5 ♂2 ♀, same locality, 29. viii. 1990,
M. Sato leg.; 1 ♂, Kabuto-mura, Toyotomi-machi, 12. vii. 1980, H. Takemoto leg.; 1 ♀, Porotoko
Lake, Tomakomai City, 30. v. 1991, R. B. Kuranishi leg.; 3 ♀, Shirarutoro Lake, Kushiro City, 4.
vi. 1991, R. B. Kuranishi leg.; 1 ♂1 ♀, Shibetsu River, Shibetsu-cho, 25-28. Vi. 2001, T. Shimadaleg. [HONSHU]: 1 ♂2 ♀, Kasumigaura, Ibaraki Pref., 30. iv. 1984, S. Ohmomo leg.; 1 ♂2 ♀,Suidobashi, Shonan-cho, Chiba Pref., 6. i. 1990, T. Takeda leg.; 1 ♂, Misugi-mura, Mie Pref., 29.
iv. 1955, Z. Naruse leg. [KYUSHU]: 1 ♀, Imuta, Soyo-cho, Kumamoto Pref., 1. v. 1993, S.
Nomura leg.
Distribution. Japan (Hokkaido, Honshu, Shikoku, Kyushu); Korea, China, Russia.
Redescription. Male and female: Macropterous; body 5.3–5.6 mm (fore body 2.5–2.7 mm) in
length, shining, covered with very short, decumbent pubescence, with antennae moderately long.
Body black, with bluish and/or greenish reﬂection; labrum black, with its anterior margin reddish
brown; antennae clear yellow to reddish brown; legs yellowish brown to reddish brown, but apical part of femur, middle of tibia, and apical part of each of 1st to 3rd tarsomeres infuscate. Headwith a pair of elongate depressions, median area between the depressions distinctly convex;
punctures round, very dense, small, distinct. Pronotum with surface weakly uneven; puncturesround to almost round, dense to very dense, distinct. Elytra shallowly impressed around the basal
half of suture; surface similarly punctate as on pronotum, but punctures a little larger than thoseon it. Legs moderately long; tarsi with 3th tarsomere emarginate, 4th tarsomere strongly bilobed.
Abdomen strongly cylindrical; punctures dense and very small to small throughout, but becoming on average gradually smaller toward 8th segment. Lateroventrites and tergo-ventrite sutures
missing on abdomen.
Male: Eighth ventrite (Fig. 101E) posteromedially with a triangular emargination; 9th tergum(Fig. 101A) elongate, with posterolateral projections long, very acute apically, ventral apophyses
long, straight; 9th ventrite (Fig. 101D) distinctly serrate posteriorly, with stem wide, widely
emarginate anteriorly, and acutely pointed anterolaterally, apicolateral teeth very acute, apicolateral setae long; 10th tergum (Fig. 101A) entire. Aedeagal median lobe (Fig. 101C) moderately
bulbous in basal 2/3, rounded apicolaterally, and strongly narrowed apically with a small subglobose apex; apical sclerotized area subtriangular in shape, with a very small apicoventral protuberance which turns anteriorly. Endophallic median longitudinal bands (Fig. 101C) long, slender;
expulsion hooks (Fig. 101C) almost H-shaped, connected by the point a little before the middleof mesial margin, each hook weakly widened posteriorly; basal tube (Fig. 101C) with basal room
probably missing, tube body consisting of the straight basal rod and the apical subfusiform structure; inner sac (Fig. 101C) posteriorly covered with small spicules. Parameres (Fig. 101C) thin,
slender; apical area short, weakly swollen mesially, and furnished with 21 to 22 setae of various
length.
Female: Eighth ventrite (Fig. 101G) obtusely pointed posteromedially; gonocoxites (Fig.

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Fig. 101. Stenus mercator Sharp (A, E, Misugi, Mie; B–D, G, Suidobashi, Chiba; F, Iwabokki, Hokkaido). A,
9th and 10th terga of male; B, gonocoxites; C, aedeagus; D, 9th ventrite of male; E, 8th ventrite of male; F,
endophallic expulsion hook; G, apex of 8th ventrite of female. Scale 1: 0.2 mm for A, C, D; scale 2: 0.2 mm
for B, 0.1 mm for F; scale 3: 0.3 mm for E, G.

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101B) each narrowed apically, rounded apicomesially, with apicolateral tooth very acute, apicolateral setae long. Spermatheca not observable.
Biology and Ecology. Stenus mercator is distributed in the plains and low mountainous
regions. The beetles inhabit the watersides of rivers and marshes.
Remarks. Stenus mercator is allied to S. sedatus and S. weisei, but this species is easily separable from the latter two species by the abdomen covered with very short, decumbent pubescenceand also with smaller, denser and more regular punctures (Fig. 134E), and the aedeagal median
lobe distinctly wide apically (Fig. 101C).
Stenus sedatus Sharp(Figs. 102A–H, 134F)
Stenus sedatus Sharp, 1889: 333; Herman, 2001: 2385; Naomi & Puthz, 2013: 140.
Type material examined. Holotype: ♀ (NHML), type locality: Niigata, Japan [examined by
Puthz in 1970].
Other material examined. [HONSHU]: 2 ♂, Saitu, Tohoku-machi, Aomori Pref., 3. viii.
1998, H. Yoshitomi leg.
Distribution. Japan (Honshu); Korea, China?
Redescription. Male: Macropterous; body 4.5–4.6 mm (fore body 2.2–2.3 mm) in length,
slender, shining, with antennae long. Body black, with greenish-bluish or coppery reﬂection;
labrum dark brown to black; antennae clear yellow to reddish brown; legs yellowish brown toreddish brown, but knees and apical part of each of 1st to 3rd tarsomeres more or less infuscate.
Head laterally with a pair of wide depressions, median longitudinal area between the depressions
distinctly convex; punctures round, very dense and small on head, but the median longitudinal
area impunctate. Pronotum with surface almost smooth, punctures round and dense to very
dense, but a median longitudinal area impunctate and indistinct in outline. Elytra weakly uneven;punctures round, very dense. Legs long; tarsi with 3th tarsomere weakly emarginate, 4th tarsomere strongly bilobed. Abdomen cylindrical, covered with relatively long, suberect pubescence;
punctures round to elliptical, dense to very dense, and moderately large in anterior parts of 3rd to
6th segments, while they are sparse and very small in posterior parts of 3rd to 6th segments;
punctures dense, very small to small in 7th and 8th segments. Lateroventrites and tergo-ventrite
sutures missing on abdomen.
Fifth ventrite (Fig. 102H) posteromedially with a short, very shallow depression, which isvery shallowly emarginate posteriorly; 6th ventrite (Fig. 102H) posteromedially with a narrow,moderately deep, bell-shaped depression, which is arcuately emarginate posteriorly; 7th ventrite(Fig. 102H) posteromedially with a bell-shaped, ﬂat area, which is very shallowly emarginate;
8th tergum shallowly, widely emarginate posteriorly; 8th ventrite (Fig. 102H) posteromediallywith a V-shaped emargination; 9th tergum (Fig. 102C) elongate, with posterolateral projections
long, ventral apophyses long, straight; 9th ventrite (Fig. 102D) elongate, with stem wide, weakly
constricted at base, and arcuately emarginate anteriorly, apicolateral teeth short, pointed, apicolateral setae moderately long; 10th tergum (Fig. 102C) entire. Aedeagal median lobe (Fig. 102A,
B) weakly or moderately bulbous in basal half, gently rounded apicolaterally, and narrowed apically with a small tubercle at the apicalmost part; apical sclerotized area a little behind the middle with a very small apicoventral protuberance which turns anteriorly. Endophallic median longitudinal bands (Fig. 102E) moderately long, ventral bands long, dorsal bands in situ with

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Fig. 102. Stenus sedatus Sharp (Saitu, Aomori). A, aedeagus; B, aedeagal median lobe; C, 9th and 10th terga of
male; D, 9th ventrite of male; E, endophallic structures; F, G, endophallic expulsion hook; H, 5th to 8th ventrites of male. Scale 1: 0.2 mm for A–D; scale 2: 0.3 mm for H; scale 3: 0.2 mm for E, 0.1 mm for F, G.

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anterior 2/3 smooth on the surface; expulsion hooks (Fig. 102F, G) almost V-shaped, fused atleast at the anterior 1/3, with each hook simply, weakly narrowed apically; basal tube (Fig. 102E)
thick, rod-like, basal room very large but without basal constriction, tube body narrowed apically, with a narrow, rod-like tube partially nested in it; inner sac furnished ventrally with a pairof fusiform sclerites (Fig. 102F, G). Parameres (Fig. 102A) short, thin, slender; apical area very
weakly swollen mesially, and furnished with 5 to 6 short, thin setae at the basal part of its mesialside, and with 11 to 12 moderately long setae at the apical half of its mesial side, and also with 1
moderately long seta at the apicalmost part.
Biology and Ecology. S. sedatus is a very rare Stenus species in Japan; and it is distributed in
the plains and low mountainous regions. The beetles inhabit watersides of the rivers andmarshes. They occasionally climb the stalk of Carex and other grasses, and ramble along theleaves.
Remarks. Only two male specimens of Stenus sedatus are examined, but they show variations regarding the following two points. First, median lobe of one male (Fig. 102B) is a little
narrower than that of the other male (Fig. 102A); and second, anterior emargination of the apicalsclerotized area of median lobe of one male (Fig. 102B) is distinctly shallower than that of theother male (Fig. 102A). However, these two males certainly show the common general shape of
median lobe as described above; and furthermore, there is no variation regarding the endophallic
structures, suggesting that they belong to the same species.
S. sedatus is the sister species of S. weisei, but this species is separable from the latter by the
body more slender (Fig. 134F), the 6th ventrite of male posteromedially with a narrower depression (Fig. 102H), the 9th ventrite of male simply, arcuately emarginate (Fig. 102D), the aedeagal
median lobe gently rounded at apicolateral part, with the apicoventral protuberance locatedbehind the middle of apical sclerotized area (Fig. 102A, B), the endophallic expulsion hook simply narrowed apically (Fig. 102F, G), and the basal tube narrowed apically (Fig. 102E).
Stenus weisei Bernhauer sp. propr.
(Figs. 103A–H, 134G)
Stenus weisei Bernhauer, 1912: 259.
Stenus sedatus Sharp, 1889: Puthz, 1971c: 14.
Type material examined. Holotype: ♀ (FMC), type locality: Nemoro, Hokkaido [examinedby Puthz in 1967].
Other material examined. [HOKKAIDO]: 1 ♂, Shibecha, 16. vi. 1985, M. Abe leg.; 1 ♀,Futatsuyama, Shibecha, 1. ix. 1993, K. Iijima leg.; 3 ♂, Daijyu-cho, 8. vii. 2001, K. Haga leg.;1 ♂, Zaimoku-cho, Kushiro City, 9. vii. 1998, T. Katsumoto leg.
Distribution. Japan (Hokkaido); Russia (?).
Redescription. Male and female: Macropterous; body 4.6–5.0 mm (fore body 2.5–2.6 mm) in
length, elongate but somewhat robust, shining, with antennae long. Body black, with feeble
greenish-bluish or coppery reﬂection; labrum black with its anterior margin reddish brown;
antennae clear yellow to reddish brown; legs yellowish brown to reddish brown, but knees andapical part of each of 1st to 3rd tarsomeres infuscate. Head laterally with a pair of moderately
deep, wide depressions, median longitudinal area between the depressions distinctly convex;
punctures round, very dense and small on head, but the median longitudinal area impunctate.
Pronotum with surface depressed obliquely on each lateral side; punctures round, dense to very

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Fig. 103. Stenus weisei Bernhauer (A, C, E, G, Shibecha, Hokkaido; B, D, Zaimoku, Hokkaido; F, H, Daijyu,
Hokkaido). A, aedeagus; B, aedeagal median lobe; C, 9th and 10th terga of male; D, endophallic basal tube;
E, gonocoxite; F, 5th to 8th ventrites of male; G, 9th ventrite of male; H, expulsion hook. Scale 1: 0.2 mm for
A–C, G, 0.1 mm for D; scale 2: 0.2 mm for E, 0.1 mm for H; scale 3: 0.3 mm for F.

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dense. Elytra with surface weakly uneven; punctures round, very dense, almost regular. Legs
long; tarsi with 3th tarsomere weakly emarginate, 4th tarsomere strongly bilobed. Abdomencylindrical, covered with relatively long, suberect pubescence; punctures round to elliptical,
dense to very dense, and moderately large in anterior parts of 3rd to 6th segments, while they aresparse and very small to small in posterior parts of 3rd to 6th segments; punctures dense, verysmall to small in 7th and 8th segments. Lateroventrites and tergo-ventrite sutures missing on
abdomen.
Male: Fifth ventrite (Fig. 103F) posteromedially with a very shallow, bell-shaped depression,
which is shallowly emarginate posteriorly; 6th ventrite (Fig. 103F) posteromedially with a moderately deep depression, which is ridged laterally and arcuately emarginate; 7th ventrite (Fig.
103F) medially with an elongate ﬂat area, which is very shallowly emarginate; 8th ventrite (Fig.
103F) posteromedially with a deep V-shaped emargination; 9th tergum (Fig. 103C) elongate,with posterolateral projections long, ventral apophyses long, straight; 9th ventrite (Fig. 103G)
elongate, shallowly bi-emarginate posteriorly, with stem wide, distinctly constricted at base, andarcuately emarginate anteriorly, apicolateral teeth short, pointed, apicolateral setae very long;
10th tergum (Fig. 103C) large, rounded posteriorly. Aedeagal median lobe (Fig. 103A, B) moderately bulbous in basal half, almost uniformly narrowed apically toward the apex with a small
tubercle (or a tuberculous apicomedian projection) at the apicalmost part; apical sclerotized area
elongate-triangular in shape, at or a little before the middle with a very small apicoventral protuberance. Endophallic median longitudinal bands (Fig. 103A) with ventral bands long, dorsal
bands short; expulsion hooks (Fig. 103A, H) fused at anterior part, each elongate, weakly spatulate; basal tube (Fig. 103A, D) with basal room short, narrower than tube body, tube body wide,
gradually widened apically, and with a narrow, rod-like tube entirely nested in it; inner sac ventrally with a pair of spindle-shaped sclerites (Fig. 103A, H). Parameres (Fig. 103A) short, thin,
slender; apical area weakly swollen mesially, and furnished with 5 to 6 short, thin setae at thebasal part of its mesial side, and with 10 to 12 moderately long setae at the apical half of its
mesial side, and also with 1 or 2 moderately long seta at the apicalmost part.
Female: Eighth ventrite pointed posteromedially; gonocoxites (Fig. 103E) each slender,rounded apicomesially, with apicolateral tooth very acute, apicolateral setae long. Spermatheca
not observable.
Biology and ecology. S. weisei is a rare Stenus species in Japan; and it is presently distributedin the plains of the eastern part of Hokkkaido. The beetles inhabit moist litter of the grasses andreeds grown around the rivers, lakes and marshes. They often climb up the grasses such that they
are collected by sweeping those grasses grown at watersides.
Remarks. Stenus weisei was ﬁrst described as a new species by Bernhauer (1912) from
“Nemoro” (＝Nemuro), Hokkaido; and after that, Stenus weisei was synonymized with S. sedatus
by Puthz (1971c). When considering the above-described morphological differences between
these two species, it is however considered that S. weisei is not conspeciﬁc with S. sedatus.
Given this, the name Stenus weisei is here resurrected from a subjective junior synonym of S.
sedatus (Sharp: 1889).
S. weisei is closely allied to, and also similar in external structure to S. sedatus, but it is separable from the latter by the body thicker (Fig. 134G), the 6th ventrite of male posteromediallywith a wider depression (Fig. 103F), the 9th ventrite of male bi-arcuate at posterior margin (Fig.
103G), the aedeagal median lobe almost straight at apicolateral part, with the apicoventral protuberance located at or before the middle of apical sclerotized area (Fig. 103A, B), the endophallic
expulsion hook weakly spatulate apically (Fig. 103A, H), and the basal tube gradually widened

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apically (Fig. 103A, D).
Etymology. The speciﬁc epithet of this species is named in honour of a German coleopterist
Dr. Julius Weise.
Stenus cicindeloides (Schaller)(Figs. 2aC, D, 104A–G, 134H)
Stenus cicindeloides (Schaller, 1783): 324; Herman, 2001: 2121; Naomi & Puthz, 2013: 140.
Stenus cicindela Sharp, 1874: 85.
Type material. No data on type material are obtained (see also Herman, 2001: 2121).
Other material examined. [HOKKAIDO]: 2 ♂2 ♀, Ashoro, 25. vi. 1986, K. Morimoto leg.;1 ♀, same locality, 26. vi. 1986, K. Morimoto leg.; 1 ♀, same locality, 24. vi. 1980, H. Takemotoleg.; 1 ♀, Nakayama Pass, 22. vi. 1986, K. Morimoto leg.; 1 ♀, Shirarutoro Lake, Kushiro, 4. viii.
1990, R. Kuranishi leg.; 1 ♂, Aioi, 24. vi. 1986, K. Morimoto leg. [HONSHU]: 2 ♂1 ♀, Sekinehama, Sekine, Mutsu City, Aomori Pref., 30. v. 1982, B. Tanaka leg.; 1 ♀, Mt. Kurikoma, Miyagi
Pref., 21. vi. 1983, K. Morimoto leg.; 1 ♂, Nuruyu, Mt. Kurikoma, Miyagi Pref., 22. vi. 1983, Y.
Sawada leg.; 2 ♂1 ♀, same locality, 23. vi. 1983, K. Morimoto leg.; 1 ♂, same locality, 6. viii.
1984, K. Morimoto leg.; 1 ♀, Mt. Kurikoma, Miyagi Pref., 21. vi. 1983, S. Nomura leg.; 1 ♂,Komanoyu, Mt. Kurikoma, Miyagi Pref., 21. vi. 1983, S. Nomura leg.; 1 ♂, Ishidoshuku,
Saitama Pref., 11. v. 1986, M. Sato leg.; 1 ♀, Nakaminato, Ibaraki Pref., 8. iv. 1978, M. Tao leg.;1 ♀, Marunuma, Oku-Nikko, Gunma Pref., 4–5. vii. 1982, S. Naomi leg.; 1 ♀, Shiobara, Tochigi
Pref., 22. viii. 1996, T. Niisato leg.; 1 ♀, Yokohama City, Kanagawa Pref., 1. x. 1983, M. Taoleg.; 1 ♀, Midori-ku, Yokohama City, Kanagawa Pref., 5. v. 1987, M. Tao leg.; 1 ♀, Miyaura,
Chiba Pref., 4. i. 1984, M. Tao leg.; 1 ♀, Yamazawa River, Kosuga-mura, Yamanashi Pref., 14.
vi. 1991, R. B. Kuranishi leg.; 1 ♂, Naramata, Ikeda, Fukui Pref., 26. v. 1974, H. Sasaji leg.; 1 ♀,Fukui City, Fukui Pref., 28. v. 1980, H. Sasaji leg.; 2 ♀, Ohkochi, Imajo, Fukui Pref., 20. viii.
1973, H. Sasaji leg.; 1 ♂, Mt. Kyogatake, Ohno, Fukui Pref., 21. vii. 1980, H. Sasaji leg.; 4 ♂2 ♀,Kasugai, Aichi Pref., 20. v. 1956, M. Sato leg.; 1 ♀, Gounodo-koike, Aichi Pref., 9. vi. 1963, Z.
Naruse leg.; 2 ♀, Seki, Gifu Pref., 4. vi. 1953, K. Ohbayashi leg.; 2 ♀, Wake, Okayama Pref., 17.
iv. 1977, S. Naomi leg.; 1 ♂, same locality, 29. iv. 1977, S. Naomi leg.; 1 ♀, Okutsu-machi,
Okayama Pref., 2. viii. 1977, M. Kaneda leg.; 1 ♀, same locality, 4. viii. 1977, Y. Tsuda leg.; 1 ♀,Araki, Saigo-cho, Dogo Is., Oki Isls., Shimane Pref., 7. viii. 2003, Y. Notsu leg. [KYUSHU]:
1 ♂, Chojabaru, Oita Pref., 26. vii. 1969, K. Kanmiya leg.; 1 ♂, Mt. Sobo, Oita Pref., 20-24. vii.
1980, K. Konishi leg.; 1 ♂, Jizobaru, Kokonoe-cho, Oita Pref., 26. v. 1988, K. Morimoto leg.;1 ♂, Mt. Kuju, Ohita Pref., 23. ix. 1980, H. Makihara leg.; 1 ♂, Bogatsuru, Mt. Kuju, Oita Pref.,27. v. 1988, K. Morimoto leg.; 1 ♂, Mt. Kurodake, Kuju, Oita Pref., 3. ix. 1982, K. Konishi leg.;1 ♂, Mt. Hiko, Fukuoka Pref., 13. vi. 1974, M.-T. Chujo leg.; 1 ♀, Mt. Tachibana, Fukuoka Pref.,7. v. 1980, S. Naomi leg.; 1 ♀, Chidori Pond, Koga-machi, Fukuoka Pref., 16. xi. 1991, S.
Nomura leg.; 2 ♂2 ♀, Madara Is., Saga Pref., 1. x. 1989, S. Nomura leg.; 2 ♀, Teraura, Hizencho, Saga Pref., 5. vi. 1993, S. Nomura leg.; 2 ♀, Imari City, Saga Pref., 30. x. 1977, H. Ohishi
leg.; 2 ♂1 ♀, Kazusa-cho, Nagasaki Pref., 23. ii. 1979, S. Imasaka leg.; 2 ♂, Kuchinotsu-cho,Nagasaki Pref., 23. ii. 1979, S. Imasaka leg.; 1 ♀, Mt. Unzen, Nagasaki Pref., 21. viii. 1979, S.
Imasaka leg. [TAIWAN]: 43 ♂57 ♀ (cS), Taiwan, Ilan Hsien, Shen-Mi Lake, 1110 m, 9. v. 1995,
A. Smetana leg.; 2 ♂5 ♀ (cS), China, N-Yunnan Dali Bai Nat. Aut. Pref. 4 km E Dali Er Hai lake,2020 m, 27. viii. 2003, A. Smetana leg.

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Fig. 104. Stenus cicindeloides (Schaller) (A, B, G, Marunuma, Gunma; C, Kuchinotsu, Nagasaki; E, Ohkochi,
Fukui; D, F, Ashoro, Hokkaido). A, 9th ventrite of male; B, 7th to 8th ventrites of male; C, aedeagus; D,
endophallic basal tube; E, gonocoxites; F, expulsion hooks with elongate-ovoidal sclerites; G, 9th and 10th
terga of male. Scale 1: 0.2 mm for A, E, 0.1 mm for D, F; scale 2: 0.3 mm for B; scale 3: 0.2 mm for C, G.

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Distribution. Japan (Hokkaido, Honshu, Shikoku, Kyushu; Madara Is.); Korea, Taiwan,
China, Vietnam, Mongolia, Russia, Europe, Madeira.
Redescription. Male and female: Macropterous; body 4.0–6.0 mm (fore body 2.3–2.7 mm) in
length, robust, shining, with antennae moderately long; paraglossae ovoidal (Fig. 2aC, D). Headand abdomen black; pronotum and elytra dark red; labrum black; antennae with basal segments
clear yellow to yellow, apical segments reddish brown; legs yellowish brown to reddish brown,
but knees (or apical 1/3 of femora, and lateral surfaces of tibiae of almost full length) and also
apical part of each of 1st to 3rd tarsomeres dark red to dark brown. Head with vertex relatively
narrow, with a pair of midlateral longitudinal depressions; punctures various in shape and size,
and rough on head, but median longitudinal convex area impunctate. Pronotum with surface
weakly uneven; punctures dense to very dense, rough, irregular. Elytra with surface weakly
uneven; punctures round, dense to very dense. Legs relatively short; tarsi with 3th tarsomere
weakly emarginate, 4th tarsomere strongly bilobed. Abdomen cylindrical, covered with short,decumbent pubescence; 3rd to 5th or 6th terga each with a short basimedian keel; punctures on
the anterior parts of 3rd to 6th terga very dense and large, while punctures on the posterior partsof 3rd to 6th terga sparse to moderately dense and small; punctures on 7th and 8th terga sparse tomoderately dense, very small to small. Lateroventrites and tergo-ventrite sutures missing on
abdomen.
Male: Seventh ventrite (Fig. 104B) posteromedially furnished with moderately dense setae;
8th ventrite (Fig. 104B) posteromedially with a subtriangular emargination; 9th tergum (Fig.
104G) with posterolateral projections very long, ventral apophyses long; 9th ventrite (Fig. 104A)
with stem wide, constricted at base, and arcuately emargnate anteriorly, apicolateral teeth very
acute, apicolateral setae very long; 10th tergum (Fig. 104G) entire. Aedeagal median lobe (Fig.
104C) bulbous in basal half, gently rounded apicolaterally, and narrowed apically toward theapex with a medium-sized globe at the apicalmost part; apical sclerotized area with a small apicoventral protuberance near the middle. Endophallic median longitudinal bands (Fig. 104C) withventral bands very long, dorsal bands short; expulsion hooks (Fig. 104C, F) separated, each comprising an elongate sclerite; basal tube (Fig. 104C, D) with basal room short and narrow, tube
body baculiform, gradually widened apically; inner sac (Fig. 104C) covered densely with verysmall spicules, and ventrally with a pair of elongate-ovoidal sclerites (Fig. 104F). Parameres(Fig. 104C) short, thin, slender; apical area short, weakly swollen mesially, and furnished mesially with 12 to 13 setae, and also with 2 or 3 setae at the apicalmost part.
Female: Eighth ventrite rounded posteriorly; gonocoxites (Fig. 104E) each pointed or angulate apicomesially, with apicolateral tooth acutely pointed, apicolateral setae moderately long.
Spermatheca not observable.
Biology and Ecology. Stenus cicindeloides is widely distributed in the plains, low and relatively high mountainous regions in Japan. It shows highly diverse habitats as follows: The beetles live under dead leaves of the grasses grown in the grasslands and around the natural forests.
The beetles inhabit the relatively dry, stony riverbanks, and walk around the stones. The beetles
also inhabit moist litter of the grasses and reeds grown around the rivers, lakes and marshes.
Since they often climb up the grasses, they are collected by sweeping those grasses grown near
the watersides.
Remarks. Stenus cicindeloides is allied to S. batak Puthz, 2008a from Sumatra, but this species is separable from the latter by the vertex of head with punctures larger and denser, the 8th
ventrite of male posteromedially with a shorter emargination (Fig. 104B), the aedeagal median
lobe with a smaller apicomedian protuberance on apical sclerotized area (Fig. 104C) (Puthz,

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2008a). Among the Japanese members of this group, S. cicindeloides is similar to S. kiesenwetteri, but it is easily separable from the latter by the elytron unicolorous (dark red), without colored maculae, and the 5th and 6th ventrites of male without modiﬁcation.
Stenus kiesenwetteri Rosenhauer(Figs. 105A–G, 134I)
Stenus kiesenwetteri Rosenhauer, 1856: 76; Herman, 2001: 2246; Naomi & Puthz, 2013: 140.
Type material. Type locality: Erlangen.
Material examined. [HOKKAIDO]: 1 ♂, Iwabokki, Kushiro Moor, 25. viii. 1990, M. Satoleg.; 4 ♂, Chitose Lake, Chitose City, 6. vi. 1999, M. Maruyama leg.; 1 ♀, Echigo Pond, Ebetsu
City, 5. vi. 1993, K. Miyashita leg.; 5 ♂3 ♀, same locality, 29. iv. 1995, K. Miyashita leg.; 1 ♀,Kimontou Pond, Daijyu-cho, 23. vi. 1993, K. Miyashita leg.; 1 ♀, Ozu, Toyokoro-cho, 5. viii.
1990, K. Haga leg.
Distribution. Japan (Hokkaido); Russia, Europe.
Redescription. Male and female: Macropterous; body 4.7–6.5 mm (fore body 2.6–3.2 mm) in
length, robust, weakly shining, with antennae relatively short. Body dark brown to black; elytra
with paired reddish maculae (Fig. 134I); labrum black; antennae reddish brown to dark brown;legs with basal 2/3 of femora yellowish brown to reddish brown, apical 1/3 of femora, tibiae andtarsi all dark red to black. Head with vertex relatively narrow, with a pair of midlateral longitudinal depressions; punctures round to elliptical, very dense, various in size. Pronotum with surface
almost even; punctures round, very dense, various in size. Elytra with surface weakly uneven;punctures round, dense to very dense, somewhat irregular. Legs thick, moderately long; tarsi
with 3th tarsomere emarginate, 4th tarsomere strongly bilobed. Abdomen cylindrical, covered
with thin, short and decumbent pubescence; 3rd to 5th terga each with a short basimedian keel;punctures on the anterior parts of 3rd to 6th terga elliptical to round, very dense and large while
punctures on the posterior parts of 3rd to 6th abdominal terga round, sparse to moderately dense,
small; punctures on 7th and 8th terga round, dense very, small to small and regular. Lateroventrites and tergo-ventrite sutures missing on abdomen.
Male: Fifth ventrite (Fig. 105A) posteromedially with a bell-shaped, ﬂat area which isdepressed along the posterior margin; 6th ventrite (Fig. 105A) posteromedially with a moderately
deep depression, which is shallowly emarginate posteriorly; 7th ventrite (Fig. 105A) moderately,
densely pubescent posteromedially; 8th ventrite (Fig. 105A) posteromedially with an arcuate
emargination; 9th tergum (Fig. 105B) elongate, with posterolateral projections very long, ventral
apophyses long; 9th ventrite (Fig. 105D) slender, hardly serrate posteriorly, with stem wide,
weakly constricted at base, and arcuately emargnate anteriorly, apicolateral teeth very acute, apicolateral setae long; 10th tergum (Fig. 105B) entire. Aedeagal median lobe (Fig. 105C) elongate,
slender, uniformly rounded apicolaterally, and narrowed apically toward the apex, with the apicomedian projection which is rounded apically; apical sclerotized area very long, with a medianlongitudinal keel. Endophallic median longitudinal bands (Fig. 105C) with ventral bands very
long, dorsal bands short; expulsion hooks (Fig. 105C, F) connected by submembranous rod, eachposteriorly covered with scale-like microsculptures; basal tube (Fig. 105C, E) short, widened
apically; inner sac (Fig. 105C) covered with very small spicules, and ventrally with a pair ofovoidal sclerites. Parameres (Fig. 105C) thin, slender; apical area short, weakly swollen mesially,and furnished mesially with 14 to 15 moderately long setae, and also 1 long seta at the api-

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Fig. 105. Stenus kiesenwetteri Rosenhauer (A, C, Iwabokki, Hokkaido; B, D–G, Ebetsu, Hokkaido). A, 5th to
8th ventrites of male; B, 9th and 10th terga of male; C, aedeagus; D, 9th ventrite of male; E, endophallic basal
tube; F, expulsion hook; G, apex of gonocoxite. Scale 1: 0.3 mm for A; scale 2: 0.2 mm for B–D; scale 3: 0.1
mm for E, F, 0.2 mm for G.

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Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

calmost part.
Female: Eighth ventrite angulate posteromedially; gonocoxites (Fig. 105G) each with apicomesial tooth pointed, apicolateral tooth large, pointed, apicolateral setae long. Spermatheca notobservable.
Biology and Ecology. S. kiesenwetteri is a rare Stenus species in Japan; and it is distributed
only in the plains and low mountainous regions of Hokkaido. The beetles inhabit moist litter ofthe grasses and reeds grown around the rivers, lakes and marshes; they are collected also fromsphagnum bogs.
Remarks. Stenus kiesenwetteri was ﬁrst reported from Japan by Puthz (1992). This species isallied to S. decoripennis Puthz, 2008a, but it is separable from the latter by the elytral maculae
smaller (Fig. 134I), the aedeagal median lobe with apical sclerotized area longer (Fig. 105C), andthe endophallic expulsion hook structured as in Fig. 105F (Puthz, 2008a). Among the Japanese
members of this group, S. kiesenwetteri is similar to S. cicindeloides, but it is separable from thelatter by the elytron with a reddish macula, and the 5th and 6th ventrites of male each posteromedially with modiﬁcations (Fig. 105A).
Etymology. The speciﬁc epithet of this species is named in honour of a German entomologist
Dr. Ernst A. H. Kiesenwetter.
Species group of S. cylindricollis Boheman
S. cylindricollis group consists of 3 species in Japan; see Puthz (1972a, 2013) regarding acharacterization of this group. Diagnostic characters are as follows: body rather slender; pronotum distinctly longer than wide; legs yellowish in general, with 3th tarsomere more or less emarginate, 4th tarsomere strongly bilobed; lateroventrites and tergo-ventrite sutures missing on
abdomen; 8th ventrite of male posteromedially with a deep emargination (Fig. 106D); 9th tergum
posteriorly with a cleaning comb (Fig. 106B); 9th tergum of male posterolaterally serrate, without apicolateral teeth (Fig. 106C); aedeagus various in shape but in Japanese species it is truncate
apically (Fig. 106E); endophallic expulsion hooks fused to be a sclerite with two posterior plates
or arms (Figs. 106G, 107E); basal tube long and slender (Fig. 107A); gonocoxite distinctly serrate posteriorly, without apicolateral tooth (Fig. 106F); spermatheca consisting of moderately
thick duct, uniformly pinstriped, with two turns, spermathecal gland large, spherical (Figs. 106A,
109C).
Key to the Japanese species of S. cylindricollis group1(2) Body (especially abdomen) thicker (Fig. 134J); 8th ventrite of male posteromedially with adeep emargination (Fig. 106D); endophallic expulsion hook with its non-fused part of posterior plate wider (Fig. 106 G); aedeagal paramere furnished only with thin setae (Fig. 106E).............................................................................................................................S. velox Sharp
2(1) Body (especially abdomen) thinner (Fig. 134K, L); 8th ventrite of male posteromediallywith a very deep emargination; endophallic expulsion hook with its non-fused part of posterior plate thinner; aedeagal paramere furnished with short, thick setae as well as common
thin setae (Figs. 107A, 108D).
3(4) Aedeagal median lobe with apicolateral part a little more strongly rounded (Fig. 107A);
endophallic expulsion hook thicker, with (fused) anterior plate on each side almost turning
anterolaterally (Fig. 107E)........................................................................S. hanami Hromádka

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267

4(3) Aedeagal median lobe with apicolateral part a little less strongly rounded (Fig. 108D); endophallic expulsion hook thinner, almost transverse (Fig. 108H) .........S. plagiocephalus Benick
Stenus velox Sharp(Figs. 106A–G, 134J)
Stenus velox Sharp, 1889: 333; Herman, 2001: 2429; Puthz, 2012a: 155; Naomi & Puthz, 2013:140.
Type material examined. ♂ lectotype (NHML): Tokio, 25. IX. - 27. IX. 81; 1 ♂1 ♀ paralectotypes (NHML, FMC): Nikko, June 1880; 1 ♀ (FMC): Fukushima. Notes: In the NHML there are
two syntypes; and one syntype is also deposited in the FMC. Puthz designated a male collectedfrom Tokyo as the lectotype in 1969; the specimen was dissected and has the labels as follows: ♂
lectotype / Puthz 1969; Japan G. Lewis 1910-320; Tokio 25. IX. - 27. IX. 81; Stenus velox Sharp
Puthz vid. 1969. Although a syntype (female; collected from Nikko) was labeled “type” by
Sharp, but it was not chosen as the lectotype because it is female specimen. In the NHML there
is another ♀ from “Oyayama, 28. IV. 1881”, but it probably belongs to a different species. The
type material was re-examined in 1997 by Puthz.
Other material examined. [HONSHU]: 1 ♂, Hirokawara, Yamagata Pref., 1. vi. 1961, Y.
Kimura leg.; 1 ♂, Kurino-machi, Tochigi Pref., 20. v. 1991, K. Sato leg.; 1 ♂1 ♀, Mt. Takao,
Hachioji City, Tokyo Metropolis, 23. vi. 1996, H. Yoshitake leg.; 1 ♂, Hikagezawa, Mt. Takao,
Tokyo Metropolis, 20. iv. 1997, S. Nomura leg.; 1 ♀, Nagatsuda, Yokohama City, Kanagawa
Pref., 27. x. 1994, T. Kishimoto leg.; 1 ♂, Yamakita-machi, Mt. Azegamaru, Kanagawa Pref., 27.
vi. 1993, K. Haga leg.; 1 ♂, Nabetani, Tatsunokuchi-cho, Ishikawa Pref., 2. vi. 1995, Y. Sugie
leg.; 1 ♂, same locality, 4. v. 1995, Y. Sugie leg.; 1 ♂, same locality, 7. vi. 1995, Y. Sugie leg.;1 ♂, Nakajima-cho, Ishikawa Pref., 16. viii. 1992, T. Kishimoto leg.; 1 ♀, Mt. Sanjyusanken,
Mikata-machi, Fukui Pref., 18. vi. 2009, M. Saito leg.; 1 ♂, Nakago City, Miyama, Gifu Pref.,27. vii. 1996, I. Kiriyama leg.; 1 ♀, Otogari, Mino City, Gifu Pref., 21. vi. 1987, Y. Takai leg.;1 ♀, Kaishonomori, Seto, Aichi Pref., 16. vi. 1996, Y. Takai leg.; 1 ♂, Amagase, Uji City, Kyoto
Pref., 4. v. 1955, Takahashi leg.; 1 ♂, Mt. Koya, Wakayama Pref., 7. viii. 1984, I. Matoba leg.;1 ♀, Hitari, Kumanogawa-cho, Wakayama Pref., 21. iv. 1993, I. Matoba leg. [SHIKOKU]: 1 ♂,Teppoishi River, Omogo Valley, 20. vi. 1992, M. Sakai leg. [KYUSHU]: 1 ♀, Hagi, Gokanosho,
Kumamoto Pref., 11. v. 1982, S. Imasaka leg.; 1 ♂, same locality, 24. vi. 1982, S. Imasaka leg.
Distribution. Japan (Honshu, Shikoku, Kyushu; Oki Is.).
Redescription. Male and female: Macropterous; body 4.0–5.9 mm (fore body 1.9–2.3 mm) in
length, slender, weakly to moderately shining, with antennae very long. Body dark brown to
black; labrum reddish brown to dark brown; antennae and legs clear yellow to yellowish red.
Head concave dorsally, vertex narrow, with a pair of thin longitudinal depressions; puncturesround and very dense on head, but median longitudinal convex area impunctate. Pronotum withsurface almost smooth; punctures very dense and rough, but median longitudinal narrow area
often impunctate. Elytra with surface shallowly depressed around the base of sutural area; punctures very round, dense, regular. Legs thin, very long; tarsi with 3th tarsomere weakly emarginate, 4th tarsomere strongly bilobed. Abdomen cylindrical, slender; 9th tergum posteriorly with acleaning comb, which is composed of a regular line of thick, straight setae of same length (Fig.
106B); punctures on 3rd to 7th terga round, dense to very dense, small to medium-sized, andalmost regular, while punctures on 8th tergum sparse and very small. Lateroventrites and tergo-268

Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

Fig. 106. Stenus velox Sharp (A, F, Gokanosho, Kumamoto; B, D, Koya, Wakayama; C, E, G, Amagase, Kyoto).
A, spermatheca; B, 9th and 10th terga of male; C, 9th ventrite of male; D, 6th to 8th ventrites of male; E,
aedeagus; F, apex of gonocoxite; G, endophallic expulsion hook. Scale 1: 0.1 mm for A, F, G, 0.2 mm for B,
C; scale 2: 0.3 mm for D; scale 3: 0.2 mm for E.

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269

ventrite sutures missing on abdomen.
Male: Sixth ventrite (Fig. 106D) posteromedially with a bell-shaped, ﬂat area; 7th ventrite(Fig. 106D) medially with an elongate depression, which is deepest at the median part; 8th ventrite (Fig. 106D) posteromedially with a deep, V-shaped emargination; 9th tergum (Fig. 106B)
with anterolateral ﬂaps small, ventral apophyses long, straight; 9th ventrite (Fig. 106C) gently
rounded anterolaterally, distinctly serrate posteriorly, with stem very thin, elongate-rectangular inshape, with apicolateral setae moderately long; 10th tergum (Fig. 106B) trapezoidal, very shallowly emarginate posteriorly. Aedeagal median lobe (Fig. 106E) nearly violin-shaped, with truncated apex; apical sclerotized area developed, with a longitudinal keel before the middle. Endophallic median longitudinal bands (Fig. 106E) with ventral bands very long, dorsal bands
moderately long; expulsion hooks (Fig. 106E) fused medially to form a unique sclerite (Fig.
106G), with non-fused parts of anterior plates widely separated, and non-fused parts of posterior
plates each narrowed posteriorly; basal tube (or ﬂagellum; Fig. 106E) thin, attenuate. Parameres(Fig. 106E) slender, weakly incurved; apical area short, weakly swollen mesially, and furnishedmesially with 22 to 25 setae.
Female: Sixth ventrite posteromedially with a very shallow emargination; 8th ventrite
rounded posteriorly; gonocoxites (Fig. 106F) each strongly serrate posteriorly, without apicolateral tooth. Spermatheca (Fig. 106A) consisting simply of moderately thick duct and uniformly
pinstriped in its whole length, with two turns, so that it does not differentiate into the capsule,RT-duct and spermathecal duct; basal porch conical, submembranous; spermathecal gland large,
spherical, with its opening located at the posterior corner of 2nd turn of the duct.
Biology and Ecology. Stenus velox is distributed in the plains and low mountainous regions.
This species is arboreal but the collecting records suggest that this may also inhabit leaf litter innatural forests.
Remarks. Stenus velox is closely allied to S. hanami and S. plagiocephalus, but this species isseparable from the latter two species by the body thicker (Fig. 134J), the 8th ventrite of maleposteromedially with a shallower emargination (Fig. 106D), and the endophallic expulsion hookwith non-fused part of posterior plate wider (Fig. 106G).
Stenus hanami Hromádka(Figs. 107A–H, 134K)
Stenus hanami Hromádka, 1979: 65; Herman, 2001: 2211; Puthz, 2012a: 155; Naomi & Puthz,
2013: 140.
Type material examined. Holotype: ♂ (MHNG), type locality: Miyanoshita, Kanagawa[examined by Puthz].
Other material examined. [HONSHU]: 1 ♂, Ootaki-cho, Isumi-gun, Chiba Pref., 11. ix.
1992. [SHIKOKU]: 1 ♂, Ohuchi, Inomachi, Kochi Pref., 12. ii. 2007, T. Miyata leg.
Distribution. Japan (Honshu, Shikoku).
Redescription. Male: Macropterous; body 4.3–4.8 mm (fore body 2.2–2.5 mm) in length,very slender, weakly to moderately shining, with antennae long. Body dark brown to black;labrum reddish brown to dark brown; antennae and legs clear yellow to yellowish red. Head simply concave dorsally, without median longitudinal convex area; punctures round, dense, almost
regular. Pronotum elongate, with surface almost smooth; punctures round, very dense, almost
regular. Elytra with surface gently convex, smooth, and similarly punctate as on pronotum, but

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Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

Fig. 107. Stenus hanami Hromádka (A, C, E–G, Ohuchi, Kochi; B, D, H, Ohtaki, Chiba). A, aedeagus; B, 9th
ventrite of male; C, 8th ventrite of male; D, apical half of endophallic basal tube; E, expulsion hook; F, 8th
tergum of male; G, 5th to 7th ventrites of male; H, 9th and 10th terga of male. Scale 1: 0.2 mm for A, B, H,
0.1 mm for D, E; scale 2: 0.3 mm for C, G; scale 3: 0.2 mm for F.

The Steninae of Japan Part 1

271punctures a little larger than those on it. Legs thin, very long; tarsi each with 3th tarsomere
weakly emarginate, 4th tarsomere strongly bilobed. Abdomen cylindrical, very slender; 9th tergum posteriorly with a cleaning comb (Fig. 107H); punctures on 3rd to 7th terga similarly punctate as on elytra, while punctures on 8th tergum sparse and very small. Lateroventrites and tergoventrite sutures missing onabdomen.
Fifth ventrite (Fig. 107G) posteromedially with a bell-shaped, ﬂat area, which is very shallowly emarginate posteriorly; 6th ventrite (Fig. 107G) posteromedially with a bell-shaped, ﬂatarea, which is emarginate posteriorly and also shallowly depressed in its mesial part; 7th ventrite(Fig. 107G) medially with an elongate depression, which is shallowly emarginate posteriorly; 8thventrite (Fig. 107C) posteromedially with a very deep, V-shaped emargination; 9th tergum (Fig.
107H) with anterolateral ﬂaps rounded anteriorly, posterolateral projections very short, ventral
apophyses long, thick; 9th ventrite (Fig. 107B) distinctly serrate posteriorly, with stem relatively
wide, pointed anteriorly, with apicolateral setae moderately long; 10th tergum (Fig. 107H) subtrapezoidal, very shallowly emarginate posteriorly. Aedeagal median lobe (Fig. 107A) elongate,
moderately constricted near apical 2/5, and truncate apically, with a sclerotized, obtuse tooth atthe ventrolateral rim on each side; apical sclerotized area developed, with a short, median longitudinal keel. Endophallic median longitudinal bands (Fig. 107A) with ventral bands very long,
dorsal bands moderately long; expulsion hooks (Fig. 107A) fused medially to form a uniquesclerite (Fig. 107E), the anterior plates widely fused basally, with non-fused parts of anterior
plates short, widely separated, and the posterior plates V-shaped, each plate (or arm) rather thin;basal tube (Fig. 107A, D) with basal room elongate-ovoidal, tube body baculiform, attenuate, but
weakly turned left apically; only near the anterior ends of ventral bands, inner sac (Fig. 107A)
visible, which is covered densely with very small spicules. Parameres (Fig. 107A) slender, very
weakly incurved; apical area relatively long, weakly swollen mesially, and furnished with 12 to
13 short to modelately long, thin setae at the apicalmost part and near the ventral margin of apical area, and also with 6 to 7 short, thick setae near its dorsal margin.
Female: Not studied.
Biology and Ecology. S. hanami is a very rare Stenus species in Japan. It is distributed in theplains and low mountainous regions. No ecological information of this species is obtained.
Remarks. Stenus hanami is closely allied to S. plagiocephalus, but this species is separablefrom the latter by the aedeagal median lobe with apicolateral part a little more strongly rounded(Fig. 107A), and the endophallic expulsion hook thicker, with its (fused) anterior plate on eachside almost turning anterolaterally (Fig. 107E).
Etymology. The speciﬁc epithet of this species is derived from a Japanese term “hanami”,
which means “cherry blossom viewing”.
Stenus plagiocephalus Benick(Figs. 108A–H, 109A–E, 134L)
Stenus plagiocephalus Benick, 1940: 567; Herman, 2001: 2343; Naomi & Puthz, 2013: 140;
Puthz, 2012a: 155.
Type material examined. Holotype: ♂ (FMC), type locality: Tienmuschan, China [examinedby Puthz].
Other material examined. [NANSEI ISLS.]: 1 ♂, Kobo, Miyako, Ishigaki Is., Okinawa Pref.,10–20. xi. 1952, C. E. Bohart leg.; 2 ♀, Mt. Banna, Ishigaki Is., Okinawa Pref., 1 ♀, Mt. Omoto,272

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Fig. 108. Stenus plagiocephalus Benick (Kobo, Ishigaki Is.). A, 4th to 5th ventrites of male; B, 6th to 7th ventrites of male; C, 8th ventrite of male; D, aedeagus; E, endophallic basal tube; F, 9th ventrite of male; G, 9th
and 10th terga of male; H, expulsion hook. Scale 1: 0.3 mm for A–C; scale 2: 0.2 mm for D, F, G; scale 3: 0.1
mm for E, H.

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273

Ishigaki Is., Okinawa Pref., 25–27. iii. 1998, M. Maruyama leg.; 2 ♀, Aira River, Iriomote Is.,
Okinawa Pref., 13. iv. 2013, I. Tanaka leg.
Distribution. Japan (Nansei Isls.: Ishigaki Is., Iriomote Is.); China.
Redescription. Male and female: Macropterous; body 4.5–4.9 mm (fore body 2.2–2.3 mm) in
length, slender, moderately shining, with antennae very long. Body dark brown to black; labrum
reddish brown to dark brown; antennae and legs clear yellow to yellowish red. Head almost simply concave dorsally; punctures round and dense on head, but median longitudinal narrow area
impunctate. Pronotum elongate, with surface weakly uneven; punctures round, very dense,
almost regular. Elytra with surface smooth, and similarly punctate as on pronotum, but punctures
a little larger than those on it. Legs thin, very long; tarsi with 3th tarsomere weakly emarginate,
4th tarsomere strongly bilobed. Abdomen cylindrical, very slender; 9th tergum posteriorly with acleaning comb (Figs. 108G, 109E); punctures on 3rd to 6th terga round, moderately dense todense, and somewhat irregular, while punctures on 7th and 8th terga sparse and very small tosmall. Lateroventrites and tergo-ventrite sutures missing on abdomen.
Male: Fourth ventrite (Fig. 108A) posteromedially with a bell-shaped, ﬂat area, which is very
shallowly emarginate posteriorly; 5th ventrite (Fig. 108A) similarly modiﬁed as on 4th ventrite,
but the ﬂat area a little more deeply emarginate posteriorly; 6th ventrite (Fig. 108B) posteromedially with a bell-shaped, moderately deep depression, which is arcuately emarginate posteriorly;
7th ventrite (Fig. 108B) medially with an elongate, very shallow depression, which is very shallowly emarginate; 8th ventrite (Fig. 108C) posteromedially with a very deep, V-shaped emargination; 9th tergum (Fig. 108G) with anterolateral ﬂaps rounded anteriorly, ventral apophyses
very long; 9th ventrite (Fig. 108F) distinctly serrate posteriorly, with stem obtusely angulate,with apicolateral setae relatively long; 10th tergum (Fig. 108G) subtrapezoidal, very shallowly
emarginate posteromedially. Aedeagal median lobe (Fig. 108D) elongate, very weakly constricted near apical 2/5, with truncated apex; apical sclerotized area with a short, median longitudinal keel. Endophallic median longitudinal bands with ventral bands very long; expulsion hooks(Fig. 108H) fused medially to form a unique sclerite, the anterior plates fused at base to form atransverse plate, with non-fused parts of anterior plates short, widely separated and pointed, andthe posterior plates V-shaped, each plate (or arm) rather thin; basal tube (Fig. 108E) with tube
body very long, slender, baculiform but weakly bent near the apical 1/3 and also distinctly bent
near the apex. Parameres slender; stem weakly constricted before the apical area (when seen ventrally); apical area moderately long, weakly swollen mesially, and furnished mesially with 12 to
13 short or moderately long setae, and also with 5 to 6 short, thick setae.
Female: Sixth ventrite posteromedially with a very shallow emargination; 8th tergum (Fig.
109B) truncate posteriorly; 8th ventrite (Fig. 109A) almost rounded posteriorly; 9th tergum (Fig.
109E) with posterolateral projections short; gonocoxites (Fig. 109D) each distinctly serrate posteriorly, with apicolateral setae relatively long. Spermatheca (Fig. 109C) with capsule elongateovoidal in shape, large; RT-duct missing; spermathecal duct short, uniformly pinstriped in its
whole length, with two turns; spermathecal gland very large, spherical, with its opening locatedat the lateral corner of 2nd turn of the duct.
Biology and Ecology. In Japan, Stenus plagiocephalus is distributed in the plains and mountainous regions of Nansei Isls. No ecological information of this species is obtained.
Remarks. Stenus plagiocephalus is ﬁrst recorded from Japan (Ishigaki Is.) by Puthz (2012a).
This species is closely allied to S. hanami, but it is separable from the latter by the aedeagal
median lobe with its apicolateral part a little less strongly rounded (Fig. 108D), and the endophallic expulsion hook thinner, and almost transverse (Fig. 108H).

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Fig. 109. Stenus plagiocephalus Benick (Banna, Ishigaki Is.). A, 8th ventrite of female; B, 8th tergum of female;C, spermatheca; D, gonocoxites; E, 9th and 10th terga of female. Scale 1: 0.2 mm for A, B, D, E, 0.1 mm forC.

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Species group of S. coelogaster Champion
S. coelogaster group consists of 1 species in Japan; see Puthz (2008a: 187) regarding a characterization of this group; and see also Puthz (2013) regarding the taxonomic information on it.
The diagnostic characters are as follows: Head distinctly narrower than elytra (Fig. 135A); legs
yellow, tarsus with 2nd and 3th tarsomeres each weakly emarginate, 4th tarsomere strongly
bilobed; lateroventrites and tergo-ventrite sutures missing on abdomen; 8th tergum with linear
sculptures on posterior part (Fig. 110F); 9th tergum posteriorly with a cleaning comb (Fig. 110B,
C); 9th ventrite of male serrate posteriorly, without apicolateral teeth (Fig. 110D); aedeagal
median lobe ventrally with a median longitudinal keel (Fig. 110A); endophallic expulsion hooks
consisting of paired small sclerites (Fig. 110A); basal tube short and thick (Fig. 110A); gonocoxite serrate posteriorly, without apicolateral tooth (Fig. 110D); spermatheca not observable.
Stenus oshimaensis Naomi(Figs. 110A–G, 135A)
Stenus oshimaensis Naomi, 1990c: 198; Herman, 2001: 2316; Naomi & Puthz, 2013: 140.
Type material examined. Holotype: ♂ (KUF), Marubatake, Amami Is., Kagoshima Pref., 22.
iii. 1986, T. Ogata leg. Paratypes: 1 ♂ (cN), Hatsuno, Amami Is., Kagoshima Pref., 11. xi. 1962,
Y. Miyatake leg.; 1 ♂ (cN), Nishinakama, Amami Is., Kagoshima Pref., 10. iv. 1976, H. Makihara leg.; 1 ♂ (cN), Maruhata, Amami Is., Kagoshima Pref., 22. iii. 1986, T. Ogata leg.; 1 ♀ (cN),
Kanpira fall, Iriomote Is., Okinawa Pref., 15. iv. 1975, H. Irie leg.
Other material examined. [NANSEI ISLS.]: 1 ♂, Kosugidani, Yaku Is., Kagoshima Pref., 17.
v. 1980, Y. Kimura leg.: 1 ♂, Hatsuno, Amami Is., Kagoshima Pref., 2. v. 1977, A. Oda leg.; 1 ♂,same locality, 11. xi. 1962, Y. Miyatake leg.; 2 ♀, Kinsakubaru, Amami Is., Kagoshima Pref., 3.
xi. 1984, M. Tomokuni leg.; 1 ♂, Mt. Yuwan, Amami Is., Kagoshima Pref., 29-31. vii. 1963, Y.
Hirashima leg.; 1 ♀, same locality, 5. v. 1977, M. Sakai leg.; 1 ♀, Santaro Pass, Sumiyo-son,
Amami Is., Kagoshima Pref., 15. x. 1988, K. Morimoto leg.; 1 ♂, Nangawa-rindo, Amami Is.,
Kagoshima Pref., 8. iv. 1991, K. Matsumoto leg.; 1 ♂, Daikuma, Amami Is., Kagoshima Pref., 1.
v. 1977, A. Oda leg.; 1 ♀, Mt. Yui, Amami Is., Kagoshima Pref., 27. iv. 1993, K. Toyoda leg.;1 ♂, Yona River, Okinawa Is., Okinawa Pref., 7. vi. 1997, K. Haga leg.
Distribution. Japan (Nansei Isls.: Yaku Is., Amami Is. Okinawa Is., Iriomote Is.).
Redescription. Male and female: Macropterous; body 3.9–5.2 mm (fore body 2.0–2.3 mm) in
length, moderately shining, with antennae long. Body dark brown to black; labrum reddish
brown to dark brown; antennae and legs clear yellow to yellowish red. Head not concave dorsally, with a pair of shallow, midlateral longitudinal depressions; punctures moderately dense tovery dense, various in size, somewhat irregular. Pronotum with surface almost even; punctures
very dense, various in size, somewhat irregular. Elytra with surface smooth, and similarly punctate as on pronotum but punctures a little larger than those on it. Legs moderately long; tarsi with
2nd and 3th tarsomeres each weakly emarginate, 4th tarsomere strongly bilobed. Abdomen cylindrical; 8th tergum (Fig. 110F) with linear sculptures on posterior part; 9th tergum posteriorly
with a cleaning comb (Figs. 110B, C); 10th tergum posteromedially with a very shallow emargination (Figs. 110B, C); punctures on anterior segments sparse to moderately dense and small,while punctures on posterior segments sparse and very small. Lateroventrites and tergo-ventrite
sutures missing on abdomen.

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Fig. 110. Stenus oshimaensis Naomi (A, Daikuma, Amami Is.; B, Hatsuno, Amami Is.; C, E, Santaro, Amami
Is.; D, F, G, Kosugidani, Yaku Is.). A, aedeagus; B, 9th and 10th terga of male; C, 9th and 10th terga offemale; D, 9th ventrite of male; E, apex of gonocoxite; F, 8th tergum of male; G, 8th ventrite of male. Scale 1:
0.2 mm for A–D, F, G, 0.1 mm for E.

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Male: Fifth to 7th ventrites each posteromedially with an indistinct ﬂat area; 8th ventrite(Fig. 110G) posteromedially with a relatively large emargination; 9th tergum (Fig. 110B) withanterolateral ﬂaps pointed (when seen dorsally), ventral apophyses long; 9th ventrite (Fig. 110D)
relatively short and wide, distinctly serrate posteriorly, with stem subtriangular in shape, pointed,
with apicolateral setae moderately long. Aedeagal median lobe (Fig. 110A) almost violin-shaped,
very acute apically with a very thin apicomedian projection, and with lateral rims very wide; apical sclerotized area apicoventrally with a median longitudinal keel. Endophallic median longitudinal bands (Fig. 110A) with ventral bands long, thin, dorsal bands relatively short, very thin;
expulsion hooks (Fig. 110A) consisting of paired small sclerites; basal tube (Fig. 110A) withbasal room elongate-ovoidal in shape, tube body short and thick, with the other short tube nested
within it; inner sac (Fig. 110A) partly visible at the place where it is densely covered with small
scales. Parameres long, weakly incurved; apical area long, weakly swollen mesially, and furnished mesially with 8 to 13 moderately long setae and 8 to 12 short, thick setae, and also apicomesially with 5 to 6 short setae.
Female: Eighth ventrite rounded posteriorly; gonocoxites (Fig. 110E) each wide, rounded laterally, strongly serrate posteriorly, with apicolateral setae long. Spermatheca not observable.
Biology and Ecology. Stenus oshimaensis is presently known from the plains and mountainous regions of Nansei Islands. The beetles have been often collected by the coleopterists whocollect cerambycids and other beetles by sweeping or beating method. This suggests that the beetles live on the twigs of trees and also on the grasses in Nansei Isls.
Remarks. Stenus oshimaensis is allied to S. dembickyi Puthz, 2013 from North India, but thisspecies is separable from the latter by the aedeagal median lobe with apicolateral part distinctly
wider and moderately rounded laterally (Fig. 110A). This species is also allied to S. bidenticollis
Puthz, 1984a from Taiwan, but it is separable from the latter by the pronotum simple, the aedeagal median lobe with apical sclerotized area smaller and shorter (Fig. 110A), and the parameresshorter (Fig. 110A).
Species group of S. wasmanni Fauvel
S. wasmanni group (＝S. mombassanus group) consists of 1 species in Japan; see Puthz(1971a) regarding a characterization of this group; and see also Puthz (2013) regarding the taxonomic information on it. The diagnostic characters are as follows: Antennae short; pronotum
short (Fig. 135B); legs yellowish in general, tarsus with 4th tarsomere strongly bilobed; lateroventrites and tergo-ventrite sutures missing on abdomen; 9th tergum posteriorly with a cleaning
comb (Fig. 111D); 9th ventrite of male serrate posteriorly, without apicolateral teeth (Fig. 111B);
aedeagal median lobe pointed or subulate apically (Fig. 111A); gonocoxite serrate posteriorly,
without apicolateral tooth (Fig. 111F); spermatheca not observable.
Stenus spurius Benick(Figs. 111A–G, 135B)
Stenus spurius Benick, 1929: 260; Herman, 2001: 2399; Naomi & Puthz, 2013: 140; Puthz,
2013: 1327.
Type material. Holotype: ♀ (FMC), type locality: Luzon, Montalban [examined by Puthz in1973].

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Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

Fig. 111. Stenus spurius Benick (A–E, G, Nishinakama, Iriomote Is.; F, Ohtomi, Iriomote Is.). A, aedeagus; B,
9th ventrite of male; C, endophallic basal tube; D, 9th and 10th terga of male; E, 7th to 8th ventrites of male;F, apex of gonocoxite; G, expulsion hook (?). Scale 1: 0.2 mm for A; scale 2: 0.2 mm for B, D, 0.1 mm for C,
F, G; scale 3: 0.3 mm for E.

Other material examined. [NANSEI ISLS.]: 1 ♂1 ♀, Nishinakama, Iriomote Is., Okinawa
Pref., 28. iii. 2001, K. Emoto leg.; 1 ♀, Shiiminato, Ohtomi, Iriomote Is., Okinawa Pref., 31. xii.
1997, Y. Kurosa leg.; 2 ♀, Takada-rindo, Ishigaki Is., Okinawa Pref., 15. v. 2012, I. Tanaka leg.;4 ♀, Ohtomi, Iriomote Is., Okinawa Pref., 31. xii. 2001, H. Watanabe leg.; 4 ♀, Nakamagawarindo, Iriomote Is., Okinawa Pref., 30. xii. 1997, I. Matoba leg.

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Distribution. Japan (Nansei Isls.: Iriomote Is.); Taiwan, Philippines, Indonesia, Laos.
Redescription. Male and female: Macropterous; body 4.0–4.3 mm (fore body 2.0–2.2 mm) in
length, moderately shining, with antennae short. Body dark brown to black; labrum reddish
brown to dark brown; antennae yellow to yellowish red, with apical segments infuscate; legs yellowish brown to reddish brown, with knees more or less infuscate. Head concave dorsally, with apair of thin, longitudinal furrows which converge anteriorly; punctures round and dense on head,but the small area of central part impunctate. Pronotum with surface almost even; puncturesround, very dense. Elytra with surface smooth, and similarly punctate as on pronotum, but punctures a little larger than those on it. Legs relatively short; tarsi with 4th tarsomere strongly
bilobed. Abdomen cylindrical; 9th tergum posteriorly with a cleaning comb (Figs. 111D); 10th
tergum (Figs. 111D) posteriorly with a shallow, wide emargination; punctures on 3rd to 6th segments round, moderately dense to dense, and small, while punctures on 7th and 8th segments
sparse and very small. Lateroventrites and tergo-ventrite sutures missing on abdomen.
Male: Seventh ventrite (Fig. 111E) posteromedially with a bell-shaped, ﬂat area, which isshallowly emarginate posteriorly; 8th ventrite (Fig. 111E) posteromedially with a relatively wide
emargination; 9th tergum (Fig. 111D) with anterolateral ﬂaps acutely pointed, ventral apophyses
very long; 9th ventrite (Fig. 111B) elongate, weakly constricted near the middle, and minutely
serrate apicolaterally, with stem elongate, rounded anteriorly, apicolateral setae short. Aedeagal
median lobe (Fig. 111A) elongate-ovoidal in basal 2/3, weakly but distinctly twice constricted
near and behind the basal 2/3, with the apex (or apicomedian projection) behind the 2nd constriction simply subulate; apical sclerotized area provided with a line of very small teeth at the mesial
side of lateral rim between the 1st and 2nd constrictions. Endophallic median longitudinal bands(Fig. 111A) with both ventral and dorsal bands short; a rectangular structure (Fig. 111A, G)
existing near the anterior rim of apical sclerotized area, and covered with small tubercles except
for the posterior surface which is covered with small subspatulate knots; basal tube (Fig. 111A,
C) with basal room ovoidal, tube body slender, but curved near the apical 1/3; inner sac covered
partially with small spicules and tubercles as in Fig. 111A. Parameres long, slender and straight;
apical area relatively short, weakly swollen mesially, and furnished mesially with 15 to 18 longsetae.
Female: Eighth ventrite obtusely pointed posteromedially; gonocoxites (Fig. 111F) each distinctly serrate posteriorly, with apicolateral setae relatively long. Spermatheca not observable.
Biology and Ecology. In Japan, Stenus spurius is presently distributed only in the plains andmountainous regions of Nansei Isls. No ecological data of this species are obtained.
Remarks. Stenus spurius was enumerated as a Japanese species by Naomi & Puthz (2013),
without collecting data; and thus this species is virtually here ﬁrst recorded from Japan (Ishigaki
Is. and Iriomote Is.). This species is closely allied to S. wasmanni Fauvel, 1895, which is distributed widely in the Oriental region, but it is separable from the latter by the aedeagal median lobe
weakly but distinctly twice constricted near and behind the basal 2/3, with its apical area behindthe 2nd constriction simply subulate, without any laterally swollen area (Fig. 111A).
Species group of S. pulcher Motschulsky
S. pulcher group consists of 1 species and 1 subspecies in Japan; see Puthz (1988a) regarding
a characterization of this group. This group is a mixed group in that it comprises some varied
species-complexes (Puthz, 2013: 1352). Thus, the following characters be presently used only forrecognizing the members of this group: Antennae long; tarsus with 3rd tarsomere emarginate api-

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cally, 4th tarsomere strongly bilobed; lateroventrites and tergo-ventrite sutures missing on abdomen; 8th tergum widely emarginate posteriorly (Fig. 112G); 9th tergum posteriorly with a cleaning comb (Fig. 112C); 9th ventrite of male without apicolateral teeth (Fig. 112B); endophallic
expulsion hooks fused to be a sclerite (Fig. 112H), without separated parts of posterior plates(which exist in S. cylindricollis group); gonocoxite without apicolateral tooth (Fig. 112F); spermatheca not observable.
Stenus ﬂavidulus Sharp(Figs. 112A–H, 135C)
Stenus ﬂavidulus Sharp, 1889: 334; Herman, 2001: 2178; Naomi & Puthz, 2013: 140.
Type material. Syntypes (NHML), type locality: Honjo, Tokio, collected in late autumn andearly spring.
Other material examined. [HONSHU]: 4 ♂, Kezuka, Higashi-matsuyama City, Saitama Pref.,31. viii. 1997, K. Toyoda leg.; 1 ♀, same locality, 31. viii. 1997, T. Shimada leg.; 2 ♂1 ♀, Doai,Urawa City, Saitama Pref., 21. iii. 1954, H. Kajimura leg.; 2 ♂2 ♀, near-Atsugi, Kanagawa Pref.,7. iv. 1960, Y. Shibata leg.; 1 ♀, Nakanogo, Hachijo Is., Tokyo Metropolis, 1. vi. 1964, Y.
Hirashima leg. [NANSEI ISLS.]: 1 ♂2 ♀, Nagakubo, Yaku-machi, Yaku Is., Kagoshima Pref., 10.
viii. 1998, K. Matsumoto leg.
Distribution. Japan (Honshu, Kyushu?; Hachijyo Is., Yaku Is.).
Redescription. Male and female: Macropterous; body 4.0–5.2 mm (fore body 2.2–2.6 mm) in
length, slender, moderately shining, with antennae very long. Head unicolorous (reddish brown
through dark red to black) or bicolorous (black with median longitudinal area reddish brown);
pronotum, elytra and 3rd to 6th abdominal segments pale yellow to yellowish orange or yellowish brown; 7th and 8th abdominal segments dark red to black, but the basal marginal area of 7th
segment reddish brown; labrum, antennae and legs yellowish brown to reddish brown. Headhardly concave dorsally, with a pair of longitudinal depressions; punctures round and moderately
dense on head but median longitudinal narrow area impunctate. Pronotum with surface almost
even; punctures round and dense but median longitudinal narrow area behind the middle impunctate. Elytra with surface smooth; punctures round, very dense and almost regular. Legs long,
slender; tarsi with 3rd tarsomere emarginate apically, 4th tarsomere strongly bilobed, with eachlobe thick. Abdomen cylindrical, narrowed posteriorly; 8th tergum (Fig. 112G) widely emarginate posteriorly; 9th tergum (Figs. 112C) posteriorly with a cleaning comb; 10th tergum pentagonal in shape, angulate posteromedially (Fig. 112C); punctures on 3rd to 6th segments round,moderately dense and small, while punctures on 7th and 8th segments sparse and very small.
Lateroventrites and tergoventrite sutures missing on abdomen.
Male: Seventh ventrite posteromedially with a bell-shaped, ﬂat area, which is shallowly
emarginate posteriorly; 8th ventrite (Fig. 112E) posteromedially with a deep V-shaped emargination; 9th tergum (Fig. 112C) elongate, with anterolateral ﬂaps relatively small, ventral apophyses
very long; 9th ventrite (Fig. 112B) elongate, ﬁnely serrate and also emarginate posteriorly, withstem rounded anteriorly, apicolateral setae long. Aedeagal median lobe (Fig. 112A) very slender,
uniformly narrowed toward the apex which has a small globe at the apicalmost part, with lateralrims provided mesially with a pair of pointed teeth located a little behind the basal 1/3; apicalsclerotized area very long, with apicomedian subtransparent area rather elongate. Endophallic
median longitudinal bands (Fig. 112A) with ventral bands moderately long, thin, dorsal bands

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281

Fig. 112. Stenus ﬂavidulus Sharp (Kezuka, Saitama). A, aedeagus; B, 9th ventrite of male; C, 9th and 10th tergaof male; D, endophallic basal tube; E, 8th ventrite of male; F, apex of gonocoxite; G, 8th tergum of male; H,
expulsion hook. Scale 1: 0.2 mm for A, B, G, 0.1 mm for D, F, H; scale 2: 0.2 mm for C; scale 3: 0.3 mm for E.

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short; expulsion hooks (Fig. 112A, H) fused to form a Y-shaped sclerite; basal tube (Fig. 112A)
with basal room a little narrower than the base of tube body, and tube body simply widened apically (Fig. 112D); a pair of elongate sclerites located a little behind basal tube (Fig. 112D), andalso a little behind these sclerites, the other transverse, sclerotized sclerite existing, which isemarginate posteromedially (Fig. 112A); inner sac visible near the apex of basal tube (Fig.
112A), where it is covered partially with small, dense spicules. Parameres very long but moderately thick; apical area swollen mesially, and furnished mesially with 26 to 28 setae, and alsowith 2 or 3 setae at the apicalmost part.
Female: Eighth ventrite rounded posteriorly; gonocoxites (Fig. 112F) each distinctly serrate
posteriorly, with apicolateral setae long. Spermatheca not observable.
Biology and ecology. S. ﬂavidulus is a rare Stenus species in Japan; and it is distributed in theplains and low mountainous regions. The beetles inhabit wet litter and grasses in the vicinity ofrivers and marshes. It was observed in Saitama that the beetles occasionally climb the stalk ofPhragmites plants grown at the wetlands located near paddy ﬁelds, and they ramble along theleaves (Toyoda, 1999).
Remarks. Stenus ﬂavidulus is allied to S. delectus Puthz, 1978 from India, Burma and Laos,but this species is separable from the latter by the body bicolorous as described above, the 8th
tergum widely emarginate posteriorly (Fig 112G), and the aedeagal median lobe more slender,
with its paramere shorter (Fig. 112A).
Stenus ﬂavidulus paederinus Champion(Fig. 135D)
Stenus paederinus Champion, 1924: 160.
Stenus ﬂavidulus paederinus Champion: Puthz, 1967: 143; Naomi, 1990c: 197; Herman, 2001:
2178; Naomi & Puthz, 2013: 140.
Type material examined. Syntypes: 1 ♂1 ♀ (NHML), type locality: Haldwani District, banksof the Nala Ronsali [examined by Puthz in 1979].
Other material examined. [NANSEI ISLS.]: 1 ♂, Shinmura, Amami Is., Kagoshima Pref., 9.
xi. 1962, C. Ohkuma leg.; 1 ♀, Asato, Yoron-cho, Yoron Is., Kagoshima Pref., 20. vi. 1998, M.
Kimura leg.; 1 ♀, Mt. Nekumachiji, Ohgimi-son, Okinawa Is., Okinawa Pref., 7. ix. 2003, S. Araileg.; 2 ♀, Genka River, Haneji, Okinawa Is., Okinawa Pref., 22. ii. 1988, K. Morimoto leg.; 1 ♀,Yona, Okinawa Is., Okinawa Pref., 18. iii. 1975, A. Watanabe leg.; 1 ♂, same locality, 20. iv.
1986, M. Yoshida leg.; 2 ♂, Ishigaki Is., Okinawa Pref., Jan. 1998-Dec. 1999, K. Takahashi leg.;11 ♂6 ♀, Nakano, Iriomote Is., Okinawa Pref., 29. iv. 1998, K. Toyoda leg.; 5 ♂5 ♀, same locality, 2. v. 1999, S. Arai leg.
Distribution. Japan (Nansei Isls.: Amami Is., Yoron Is., Toku Is., Okinoerabu Is., Okinawa
Is., Ishigaki Is. and Iriomote Is.); Taiwan, China, India, Oriental region.
Redescription. Stenus ﬂavidulus paederinus is basically the same in morphology as the nominotypical subspecies. It is, however, separable from the latter by the following characters: First,
the body coloration is different in the following style (Fig. 135D): head dark red to black; pronotum reddish brown; elytra dark red to black but the anterior and posterior marginal areas yellowish brown to reddish brown in their full width, and the pale-colored area of posterior margin
extends anteriorly along the suture so that the pale-colored area form a wide-triangular area, sucha triangular pale-colored area also found in the anterior 1/2 of elytra; abdomen with 3rd to 6th

The Steninae of Japan Part 1283

segments reddish brown, but the basimedian parts of 3rd to 5th terga each occasionally with adark red, subtriangular spot; 7th and 8th segments dark red to black, but the basal marginal areaof 7th segment reddish brown. Second, the aedeagal median lobe of S. ﬂavidulus paederinus ison average a little narrower and longer than that of nominotypical subspecies (Puthz, 1967).
Biology and ecology. In Japan, Stenus ﬂavidulus paederinus is distributed in the plains andlow mountainous regions of Nansei Isls. The beetles inhabit wet litter and grasses in the vicinityof marshes. It was observed at the marshes of Iriomote Is. that the beetles live on the leaves andnear the roots of Carex plants (Toyoda, 1999).
Remarks. Stenus paederinus was ﬁrst described from Haldwani by Champion (1924). Puthz(1967) downgraded it as a subspecies of S. ﬂavidulus. Naomi (1990) ﬁrst recorded S. ﬂavidulus
paederinus from Japan (Amami Is. and Oknawa Is.). Given the body coloration of this species
which is similar to that of Paederus species, this subspecies seems to show a Batesian mimicry(Puthz, 1967).
Species group of S. bispinus Motschulsky
S. bispinus group consists of 1 species in Japan; see Puthz (1985) regarding a characterization of, and a key to species of this group. Diagnostic characters are as follows: Head with vertex
only shallow concave, ﬂat or weakly convex dorsally, without distinct longitudinal furrows (Fig.
135E); antennae long; legs yellowish in general, tarsus with 3rd tarsomere emarginate apically,
4th tarsomere strongly bilobed; lateroventrites and tergo-ventrite sutures missing on abdomen;
9th tergum posteriorly with a cleaning comb (Fig. 113B); 9th ventrite of male bispinose, with apair of thin, long, apicolateral teeth (Fig. 113F); endophallus often with fused expulsion hook,
and also with median sclerite and apicolateral plates (Fig. 113C; Puthz, 1985); gonocoxite with athin, long, apicolateral tooth (Fig. 113E); spermatheca (Fig. 113G) sclerotized with RT-duct uniformly pinstriped.
Stenus currax Sharp(Figs. 113A–I, 135E)
Stenus currax Sharp, 1874: 88; Herman, 2001: 2153; Naomi & Puthz, 2013: 140.
Type material examined. Lectotype: ♂ (NHML), type locality: Nagasaki, Japan, Lewis [designated by Puthz in 1985: 84].
Other material examined. [HONSHU]: 1 ♂1 ♀, Kamiyukawa, Arida, Wakayama Pref., 3. v.
1974, I. Matoba leg. [SHIKOKU]: 1 ♂, Fukagi, Nakamura City, Kochi Pref., 24. x. 2001; 1 ♂,Nishikawanaka River, Umaji-mura, Kochi Pref., 3. v. 1988, K. Haga leg. [KYUSHU]: 5 ♂2 ♀,Uchinoura-machi, Kagoshima Pref., 1. v. 2009, M. Saito leg.
Distribution. Japan (Honshu, Kyushu; Hachijyo Is., Yaku Is.); Taiwan, China, Vietnam, Thailand, Myanmar, Indonesia.
Redescription. Male and female: Macropterous; body 4.0–5.5 mm (fore body 2.0–2.6 mm) in
length, moderately shining, with antennae long and thin. Body dark red to black; labrum reddish
brown to dark brown; antennae and legs pale yellowish brown to reddish brown. Head shallowly
concave dorsally, with a pair of indistinct longitudinal depressions; punctures round to elliptical,
dense to very dense. Pronotum with surface almost even; punctures round, very dense, almost
regular. Elytra large, well convex dorsally; surface punctate as on pronotum but punctures a little

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Fig. 113. Stenus currax Sharp (A, B, F, H, Fukagi, Kochi; C–E, G, I, Uchinoura, Kagoshima). A, aedeagal
median lobe; B, 9th and 10th terga of male; C, aedeagus; D, endophallic expulsion hook; E, gonocoxite; F,
9th ventrite of male; G, spermatheca; H, apex of 8th ventrite of male; I, median longitudinal bands. Scale 1:
0.2 mm for A–C, F, I; scale 2: 0.2 mm for E, 0.1 mm for D, G; scale 3: 0.3 mm for H.

The Steninae of Japan Part 1285

larger than those on it. Legs moderately long; tarsi with 3rd tarsomere widely emarginate apically, 4th tarsomere strongly bilobed. Abdomen relatively thick, subparallel-sided; 9th tergum(Fig. 113B) posteriorly with a cleaning comb; punctures on 3rd to 5th segments moderately
dense and small, while punctures on 6th and 8th segments sparse and very small. Lateroventrites
and tergoventrite sutures missing on abdomen.
Male: Seventh ventrite posteromedially with a shallow emargination; 8th ventrite (Fig.
113H) posteromedially with a large, U-shaped emargination; 9th tergum (Fig. 113B) with anterolateral ﬂaps relatively small, ventral apophyses very long; 9th ventrite (Fig. 113F) bispinose witha pair of thin, long, apicolateral teeth, apicolateral setae moderately long; 10th tergum (Fig.
113B) entire. Aedeagal median lobe (Fig. 113A, C) elongate, slender and narrowed apically tothe pointed apex, with a very short apicomedian projection (or protuberance); apical sclerotizedarea subtriangular in shape, with the narrow, median longitudinal area less strongly sclerotized,
and with a pair of denticulate areas at the middle of anterior margin; apicomedian subtransparent
area (Fig. 113C) very large and anteriorly demarcated by the transverse bridge. Endophallic
median longitudinal bands (Fig. 113I) with ventral bands moderately long, thin, dorsal bands
short, each narrowed anteriorly; expulsion hooks (Fig. 113C, D) fused to form a X-shaped sclerite, posterior plate apically set with scratch-like microsculpture; basal tube (Fig. 113C) longate,
pitcher-shaped, distally with an elongate, ﬂagellar duct; median sclerite (Fig. 113C) arrowheadshaped, strongly sclerotized; apicolateral plates (Fig. 113C) almost bowl-shaped, sclerotized.
Parameres very long, slender; stem very thin, and weakly sinuous around the base of apical area;
apical area strongly swollen mesially, pallet-like, and furnished mesially with 14 to 20 thin setae,
and also with 11 to 14 very short, thick and weakly curved setae.
Female: Eighth ventrite rounded posteriorly; gonocoxite (Fig. 113E) distinctly angulate apicomesially, with apicolateral tooth stout, weakly incurved, apicolateral setae short. Spermatheca(Fig. 113G) with capsule missing; RT-duct rather thick, densely pinstriped; spermathecal duct
almost tightly coiled, with 6 turns; basal valve not observable.
Biology and ecology. Stenus currax is distributed in the plains and low mountainous regionsin Japan. No data are obtained on the ecology and habitats of this species.
Remarks. Stenus currax is allied to S. miriventris Puthz, 1985 from Thailand, but this species
is separable from the latter by the body larger and robuster, the head narrower than elytra, theaedeagal median lobe with wider apex (Fig. 113A, C), the endophallic expulsion hook elongate
and pitcher-shaped, distally with an elongate ﬂagellar duct (Fig. 113C), and the apical parameralarea distinctly swollen mesially (Fig. 113C) (Puthz, 1985).
The specimens examined show a variation regarding the shape of aedeagal median lobe. The
apical part of median lobe is basically narrow, but the apical part of median lobe of a specimen
from Fukagi, Shikoku (Fig. 113A) is distinctly narrower than that of Uchinoura, Kyushu (Fig.
113C). The similar variations of aedeagal median lobe shown in the specimens collected fromseveral localities of Southeast Asia were also mentioned by Puthz (1985; ﬁgs. 13–16). However,these local populations share the common unique characters of endophallic structures as
described above; and thus the structural variation of the apex of median lobe that we observed beconsidered infraspeciﬁc one.
Species group of S. alpicola Fauvel
S. alpicola group consists of 2 species in Japan; see Puthz (2003c) regarding a review of thisgroup; and see Ryvkin (2000) regarding a key to some Palaearctic species of this group. Diag-286

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nostic characters are as follows: Head with vertex hardly concave dorsally, with a pair of very
shallow depressions (Fig. 135F); pronotum wider than long, mostly with a median longitudinal
depression; legs with tarsi simple; abdomen with lateroventrites ventromesial in position, relatively wide; 9th ventrite of male with apicolateral teeth pointed (Fig. 114B); aedeagal median
lobe more or less pointed apically (Fig. 114A); endophallic explusion hooks fused to form atransverse, U-shaped or M-shaped sclerite (Fig. 114H; Puthz, 2003c); gonocoxite with apicolateral tooth pointed (Fig. 114E); spermatheca with duct short, not coiled (Fig. 114G) or very long,tightly coiled (Puthz, 2003c, ﬁgs. 9, 10).
Key to the Japanese species of S. alpicola group1(2) Pronotum and elytra less coarsely, more regularly punctate; metaventrite posteromediallywith a longitudinal furrow distinct (especially in male); legs reddish brown to dark red;
meso- and metatibiae each with a preapical spur longer; aedeagal median lobe with apicalsclerotized area longer (Fig. 114A) ........................................................... S. veselovae Ryvkin2(1) Pronotum and elytra more coarsely, more irregularly punctate; metaventrite posteromediallywith a longitudinal furrow indistinct; legs yellowish brown to reddish brown; meso- andmetatibiae each with preapical spur shorter; aedeagal median lobe with apical sclerotizedarea shorter (Fig. 115E) .............................................................................S. sibiricus Sahlberg
Stenus veselovae Ryvkin(Figs. 114A–H, 135F)
Stenus veselovae Ryvkin, 1987b: 273; Herman, 2001: 2431.
Stenus noctivagus Casey, 1884: Naomi, 1997c: 22; Naomi & Puthz, 2013: 140.
Type material. Holotype: ♂ (ZIRAS), S-Jamal, Sr.-Ščučje, eluvium, Russia, 1. viii. 1980, E.
Veselova leg
Other material examined. [HOKKAIDO]: 1 ♂1 ♀, Mt. Yotei, Abuta, 7. vii. 1989, N. Yasudaleg.
Distribution. Japan (Hokkaido); Russia, Europe.
Redescription. Male and female: Brachypterous; body 2.5–3.6 mm (fore body 1.2–1.7 mm) in
length, somewhat ﬂat dorsally, weakly shining, with short antennae. Body and labrum dark chocolate brown to black; antennae dark red to chocolate brown; legs reddish brown to dark red, withknees more or less infuscate. Head hardly concave dorsally, with a pair of very shallow depressions, median longitudinal area convex, a little higher in level than mesial margin of eye; punctures round, dense to very dense, somewhat umbilicate. Pronotum with surface weakly uneven,with median longitudinal depression indistinct; punctures round, very dense. Elytra with surface
weakly uneven; punctures round, very dense, almost regular. Legs relatively short; tarsi simple.
Abdomen relatively wide, weakly convex dorsally; punctures round, very dense and small inanterior segments, while punctures in posterior segments elliptical, very small and regular. Lateroventrites ventromesial in position, relatively wide, punctate.
Male: Metaventrite ﬂat posteromedially, with a short longitudinal furrow (Puthz, 1993, ﬁgs.
1–3, 5); meso- and metatibiae each with a preapical spur; 7th ventrite (Fig. 114C) posteromedially with a large, subovoidal ﬂat area, which is shallowly emarginate posterioly; 8th ventrite (Fig.
114C) posteromedially with a small emargination; 9th tergum (Fig. 114D) with anterolateral

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Fig. 114. Stenus veselovae Ryvkin (Yotei, Hokkaido). A, aedeagus; B, 9th ventrite of male; C, 7th to 8th ventrites of male; D, 9th and 10th terga of male; E, gonocoxite; F, 9th and 10th terga of female; G, spermatheca;
H, endophallic expulsion hook. Scale 1: 0.1 mm for A, B, E, 0.2 mm for G, 0.05 mm for H; scale 2: 0.3 mm for
C; scale 3: 0.1 mm for D, F.

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ﬂaps subtrapezoidal in shape, ventral apophyses short, narrowed apically; 9th ventrite (Fig.
114B) wide, widest at basal 1/3, very ﬁnely serrate posteriorly, gently rounded at apicolateralcorners, with stem small, subtriangular in shape, apicolateral teeth short, pointed, apicolateral
setae short; 10th tergum (Fig. 114D) entire. Aedeagal median lobe (Fig. 114A) elongate, pointed
apically, with apical sclerotized area almost triangular in shape. Endophallic median longitudinalbands (Fig. 114A) with ventral bands partially fused (?), a little shorter than dorsal bands which
distinctly diverge anteriorly; expulsion hooks (Fig. 114A, H) fused to form a transverse sclerite
which has anterolaterally the separated anterior plates; basal tube (Fig. 114A) short, moderately
thick, weakly curved. Parameres (Fig. 114A) slender, weakly incurved; apical area short, weakly
swollen mesially, and furnished mesially with 12 to 16 setae of various length.
Female: Metaventrite with a posteromedian longitudinal furrow shallower; 8th ventrite
obtusely pointed posteromedially; 9th tergum (Fig. 114F) with anterolateral ﬂaps short; gonocoxites (Fig. 114E) each posteriorly serrate, apicomesially with a pointed tooth, apicolateral tooth
pointed, apicolateral setae moderately long; 10th tergum (Fig. 114F) entire. Spermatheca (Fig.
114G) with capsule small, narrowed apically; RT-duct only indistinctly demarcated from the capsule; spermathecal tube very short, thick, with two turns; basal pouch bowl-shaped.
Biology and Ecology. Stenus veselovae is widely distributed in the Palaearctic region; andthe beetles inhabit litter and mosses in larch (Larix) forests and also in other plant communities(Ryvkin, 2000). The beetles were only once collected in Japan from the low mountainous regionof Hokkaido; and no solid information is presently obtained regarding the habitats of this species
in Japan.
Remarks. Stenus veselovae was ﬁrst recorded from Japan (Hokkaido) as S. noctivagus by
Naomi (1997c). This species is allied to S. sibiricus, but it is separable from the latter by the fore
body less coarsely, more regularly punctate, the legs darker in coloration (Ryvkin, 2000), and theaedeagal median lobe with apical sclerotized area narrower and longer (Fig. 114A).
Etymology. This species is named in honour of Ms. E. Veselova (Moscow), who collected thetype specimens of this species.
Stenus sibiricus Sahlberg(Figs. 115A–H, 135G)
Stenus sibiricus Sahlberg, 1880: 79; Herman, 2001: 2388.
Type material examined. Lectotype: ♀ (DEIM), type locality: Imbatsk, Sahlberg [designatedby Ryvkin (1987: 272); and examined by Puthz].
Other material examined. [HONSHU]: 1 ♂, Shirakoma, Mt. Kitayatsu, Nagano Pref., 13–16.
ix. 1996, T. Ito leg.
Distribution. Japan (Honshu); Russia, Kyrgystan, Mongolia, China, Canada, USA.
Redescription. Male and female: Brachypterous; body 2.5–4.1 mm (fore body 1.2–2.0 mm) in
length, somewhat ﬂat dorsally, weakly shining, with short antennae. Body and labrum dark chocolate brown to black; antennae reddish brown, with apical segments infuscate; legs yellowish
brown to reddish brown, with knees more or less infuscate. Head hardly concave dorsally, with apair of very shallow depressions, median longitudinal area convex; punctures dense to very
dense, coarse, somewhat umbilicate. Pronotum with surface uneven, with median longitudinal
depression distinct; punctures round, very dense, coarse. Elytra with surface uneven; puncturesround to elliptical, very dense, coarse. Metaventrite ﬂat posteromedially, with a longitudinal fur-The Steninae of Japan Part 1289

Fig. 115. Stenus sibiricus Sahlberg (A, F, G, Amur, Russia; B–E, H, Kitayatsu, Nagano). A, spermatheca; B, 9th
and 10th terga of male; C, 9th ventrite of male; D, endophallic basal tube; E, aedeagus; F, 7th to 8th ventrites
of male; G, gonocoxite; H, expulsion hook. Scale 1: 0.1 mm for A, G, 0.05 mm for D, H; scale 2: 0.1 mm for
B, C, E; scale 3: 0.3 mm for F.

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row indistinct (Puthz, 1993, ﬁgs. 4, 6). Legs relatively short; tarsi simple. Abdomen relatively
wide, weakly convex dorsally; punctures round to elliptical, very dense and small in anterior segments, while punctures in posterior segments elliptical, very small and regular. Lateroventrites
ventromesial in position, relatively wide, punctate.
Male: Meso- and metatibiae each with a short preapical spur; 7th ventrite (Fig. 115F) posteromedially with a large, subovoidal ﬂat area, which is very shallowly emarginate posterioly;
8th ventrite (Fig. 115F) posteromedially with a small emargination; 9th tergum (Fig. 115B) withanterolateral ﬂaps subtrapezoidal in shape, ventral apophyses relatively long; 9th ventrite (Fig.
115C) wide, widest a little behind the basal 1/3, gently rounded at apicolateral corners, and serrate posteriorly, with stem subtrapezoidal in shape, apicolateral teeth very short, pointed, apicolateral setae short; 10th tergum (Fig. 115B) entire. Aedeagal median lobe (Fig. 115E) wide,
rounded at apicolateral corners, and narrow but rounded at apex. Endophallic median longitudinal bands (Fig. 115E) with ventral bands fused (?), with the apex spatulate, dorsal bands rather
wide, each narrowed anteriorly; expulsion hooks (Fig. 115E, H) fused to form a transverse, pentagonal-shaped sclerite which has anterolaterally the separated anterior plates; basal tube (Fig.
115D, E) short, moderately thick, and weakly curved. Parameres (Fig. 115E) very weakly
incurved; apical area rather short, weakly swollen mesially, and furnished mesially with 8 to 12
setae of various length, and apically with 3 to 4 short setae.
Female: Eighth ventrite obtusely pointed posteromedially; gonocoxites (Fig. 115G) each serrate posteriorly, with apicolateral tooth acutely pointed. Spermatheca (Fig. 115A) consisting simplely of a short duct with two turns (not differentiated into capsule, RT-duct and spermathecalduct), but duct of a very short span near the base sclerotized; basal pouch bowl-shaped.
Biology and Ecology. In Japan, S. sibiricus is a very rare Stenus species; and only one beetle
was collected from the mountainous region of Central Honshu. No solid information is presently
obtained regarding the habitats of this species in Japan.
Remarks. Stenus sibiricus is allied to S. veselovae, but this species is separable from the latterby the fore body more coarsely, more irregularly punctate, the legs lighter in coloration, and theaedeagal median lobe with apical sclerotized area shorter (Fig. 115E). S. sibiricus is here ﬁrst
recorded from Japan.
Species group of S. virgula Fauvel
S. virgula group consists of 1 species in Japan; see Puthz (2013) regarding a review of thisgroup. This may be a mixed group but the following characters can be presently used for recognizing the members of this group: Paraglossae oval; legs with 4th tarsomere strongly bilobed;
abdomen with lateroventrites dorsomesial in position, and narrow; 9th tergum posteriorly with ashort cleaning comb (Fig. 116B); 9th ventrite of male with apicolateral teeth pointed (Fig. 116C)
but sometimes missing (Puthz, 2013); aedeagal median lobe more or less pointed apically (Fig.
116A); gonocoxite with apicolateral tooth pointed (Fig. 116D); paramere often apicomesiallywith a dorsal ﬂap (Fig. 116A; Puthz, 2013); spermatheca with duct short, relatively thick (Fig.
116G).
Stenus rugipennis Sharp(Figs. 116A–G, 135H)
Stenus rugipennis Sharp, 1874: 85; Herman, 2001: 2373; Naomi & Puthz, 2013: 140.

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Fig. 116. Stenus rugipennis Sharp (A–C, Mihara, Hachijo Is.; D, G, Chimachibo, Saga; E, F, Awa, Okinawa Is.).
A, aedeagus; B, 9th and 10th terga of male; C, 9th ventrite of male; D, gonocoxites; E, 7th to 8th ventrites ofmale; F, 8th ventrite of female; G, spermatheca. Scale 1: 0.1 mm for A, 0.2 mm for F; scale 2: 0.2 mm for B,
C, G, 0.1 mm for D; scale 3: 0.3 mm for E.

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Stenus sharpianus Cameron, 1930: 205.
Stenus namazu Hromádka, 1979c: 101.
Type material examined. Syntype: ♂ (NHML), type locality: Copper Temple, Nagasaki[examined by Puthz in 1968].
Other material examined. [HOKKAIDO]: 1 ♂, Higashi-Ohnuma, Nanae, Oshima, 14. vi.
1986, S. Nomura leg.; 1 ♀, same locality, 16. vi. 1986, S. Nomura leg.; 1 ♂, Oketo, 21. viii. 1992,
T. Kato leg. [HONSHU]: 1 ♂, Yumoto, Oku-Nikko, Tochigi Pref., 19. vii. 1977, M. Tao leg.; 2 ♀,Chikura-machi, Chiba Pref., 26. vi. 1994, S. Naomi leg.; 1 ♀, Mihama, Chiba City, Chiba Pref.,3. ii. 1994, Y. Hagino leg.; 1 ♂, Yokohama C., Kanagawa Pref., 1. x. 1983, M. Tao leg.; 1 ♂,same locality, 21. ix. 1986, M. Tao leg.; 1 ♀, Tsurumi-ku, Yokohama C., Kanagawa Pref., 10. vii.
1983, M. Tao leg.; 1 ♂1 ♀, same locality, 16. v. 1987, M. Tao leg.; 1 ♂, Yorizawa, Mt. Tanzawa,
Kanagawa Pref., 10. viii. 1987, M. Tao leg.; 1 ♂1 ♀, Mt. Mihara, Hachijo Is., Izu Isls., Tokyo
Metropolis, 2. iv. 1994, S. Naomi leg.; 1 ♂3 ♀, same locality, 3. iv. 1994, S. Naomi leg.; 1 ♂1 ♀,Mt. Oyama, Mikura Is., Izu Isls., Tokyo Metropolis, 7. vi. 1996, S. Naomi & M. Maruyama leg.;1 ♂1 ♀, Sato-Kawada, Mikura Is., Izu Isls., Tokyo Metropolis, 8. vi. 1996, S. Naomi & M.
Maruyama leg.; 1 ♂, Gifu, 26. iv. 1946, K. Ohbayashi leg.; 1 ♀, Higashi-ku, Nagoya City, Aichi
Pref., 6. x. 1955, Z. Naruse leg.; 2 ♀, Nisshin, Aichi Pref., 18. xii. 1985, T. Kato leg.; 1 ♀, Mt.
Daisen, Tottori Pref., 8. xi. 1977, S. Naomi leg.; 1 ♂, Ukankei, Okayama Pref., 19. iii. 1977, O.
Yamaji leg.; 1 ♀, Makiyama, Okayama City, Okayama Pref., 6. iii. 1977, S. Naomi leg.; 2 ♂2 ♀,Bizenhara, Okayama Pref., 26. ii. 1977, S. Naomi leg. [KYUSHU]: 1 ♀, Mt. Tachibana, Fukuoka
Pref., 1. vi. 1978, K. Yamagishi leg.; 2 ♀, Otomari, Ume-cho, Ohita Pref., 15. iii. 1986, S. Sasaki
leg.; 1 ♀, Chimachibo, Yamauchi-cho, Saga Pref., 23. ix. 1970, Y. Eguchi leg.; 2 ♂, Kazusa,
Nagasaki Pref., 27. iii. 1978, S. Imasaka leg.; 1 ♀, Senbuki, Shimabara, Nagasaki Pref., 28. v.
1977, S. Imasaka leg.; 1 ♀, Sugitani, Shimabara, Nagasaki Pref., 23. viii. 1977, S. Imasaka leg.;1 ♀, Kawachi-son, Kumamoto City, Kumamoto Pref., 14. viii. 1977, S. Naomi leg.; 1 ♂, Kurokami, Kumamoto City, Kumamoto Pref., 30. iii. 1962, H. Aramaki leg. [NANSEI ISLS]: 1 ♂,Funakura, Nakanoshima Is., Tokara Isls., Kagoshima Pref., 13. vii. 1982, Y. Takai leg.; 2 ♂1 ♀,Tete, Toku Is., Kagoshima Pref., 4. v. 1988, S. Nomura leg.; 1 ♀, Mt. Inokawa, Toku Is.,
Kagoshima Pref., 2. v. 1988, S. Nomura leg.; 2 ♂1 ♀, Akaogi, Amami Is., Kagoshima Pref., 23.
iii. 1978, S. Naomi leg.; 1 ♂, Yamatohama, Amami Is., Kagoshima Pref., 24. iii. 1978, S. Naomi
leg.; 1 ♂, Hatsuno, Amami Is., Kagoshima Pref., 27. iii. 1978, S. Naomi leg.; 1 ♀, Shinmura,Amami Is., Kagoshima Pref., 28. iii. 1978, S. Naomi leg.; 1 ♂1 ♀, same locality, 9. xi. 1962, C.
Ohkuma leg.; 1 ♀, Naze City, Amami Is., Kagoshima Pref., H. Makihara leg.; 1 ♀, Mt. Yui,
Amami Is., Kagoshima Pref., 26. iii. 1979, Y. Tsuda leg.; 4 ♂3 ♀, Awa, Motobu Peninsula, Okinawa Is., Okinawa Pref., 13. iii. 1978, S. Naomi leg.; 1 ♀, Mt. Nishime, Kunigami, Okinawa Is.,
Okinawa Pref., 19. x. 1987, M. Sakai leg.; 2 ♂1 ♀, Sueyoshi, Naha City, Okinawa Is., Okinawa
Pref., 20. v. 1990, T. Ueno leg. [TAIWAN]: 1 ♂ (cS), Taiwan, Taichung Hsien, Anmashan,
2225 m, 3. v. 1990, A. Smetana leg.; 1 ♂ (cS), same locality, 11–15. v. 1992, A. Smetana leg.;1 ♀, Taiwan, Taichung Hsien, Anmashan Creek, 2185 m, 12. v. 1992, A. Smetana leg.
Distribution. Japan (Hokkaido, Honshu, Shikoku, Kyushu; Mikura Is., Hachijo Is., Ogasawara Isls., Yaku Is., Tokara-Naka Is., Amami Is., Toku Is., Okinawa Is.); Korea, Taiwan, China,
Russia (Eastern part).
Redescription. Male and female: Macropterous; body 3.2–4.9 mm (fore body 1.8–2.3 mm) in
length, mat, with short antennae. Head black; pronotum, elytra and abdomen dark red; labrum
dark red; antennae and legs yellowish brown to reddish brown, with knees weakly infuscate.

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Head weakly concave dorsally, with a median longitudinal convex area; punctures round, very
dense, small, somewhat umbilicate. Pronotum with surface uneven; punctures round to elliptical,very dense, coarse. Elytra with surface uneven; punctures round to elliptical, very dense andcoarse, sometimes two or more punctures partially connate．
Legs relatively short; tarsi with 4thtarsomere strongly bilobed. Abdomen relatively wide, convex dorsally; 9th tergum posteriorly
with a short cleaning comb (Fig. 116B); punctures basically elliptical and very dense throughout
but they become smaller posteriorly toward 8th segment. Lateroventrites dorsomesial in position,
narrow, punctate.
Male: Seventh ventrite (Fig. 116E) posteromedially with a bell-shaped, ﬂat area, which isvery shallowly emarginate posterioly; 8th ventrite (Fig. 116E) posteromedially with a small,
shallow emargination; 9th tergum (Fig. 116B) elongate, with anterolateral ﬂaps small, ventral
apophyses long; 9th ventrite (Fig. 116C) elongate, indistinctly bi-arcuate at posterior margin,
with stem rounded anteriorly, apicolateral teeth pointed, apicolateral setae moderately long; 10th
tergum (Fig. 116B) entire. Aedeagal median lobe (Fig. 116A) slender and pointed apically, apicalsclerotized area subtriangular, ventrally with a median longitudinal suture. Endophallic medianlongitudinal bands (Fig. 116A) with both ventral and dorsal bands thin, very long and slender,
but ventral bands longer than dorsal ones; expulsion hooks (Fig. 116A) separated but connectedby a transverse rod, with anterior plate demarcated by a curved suture from posterior plate; basal
tube (Fig. 116A) with basal room almost spherical, tube body simple, baculiform, almost
straight. Parameres (Fig. 116A) long, each moderately thick basally, and spatulate (when seen
ventrally) by apically having a large dorsal ﬂap (which is rounded mesially); apical area furnished mesially with 5 to 8 short, moderately thick setae, and also with 9 to 10 setae of same
form along the mesial margin of dorsal ﬂap.
Female: Eighth ventrite (Fig. 116F) weakly protruded and pointed posteromedially; gonocoxites (Fig. 116D) each irregularly serrate posteriorly, with apicolateral tooth acutely pointed,
apicolateral setae very long. Spermatheca (Fig. 116G) with capsule subovoidal, constrictedbasally; RT-duct missing; spermathecal duct short, relatively thick, with two turns; basal valve
long; spermathecal gland with its opening located at the posterior side of the 2nd turn of the duct.
Biology and ecology. S. rugipennis is a common Stenus species in Japan; and it is widely distributed in the plains and mountainous regions there. The beetles inhabit litter in grasslands; andthey also inhabit the relatively dried leaf litter near bushes, groves and plantations. The beetles
were collected under the piles of dead sugar canes leaved at the ﬁelds after the harvest in Amami
Is.
Remarks. Stenus rugipennis is closely allied to S. suspectatus Puthz, 2003a from Taiwan, but
this species is separable from the latter by the body larger (Fig. 135H), the endophallic expulsion
hooks larger, with anterior plate demarcated by a curved suture from posterior plate (Fig. 116A),
and the spermathecal duct longer, with two turns (Fig. 116G; Puthz, 2003a, ﬁg. 23).
Species group of S. abdominalis Fauvel
S. abdominalis group consists of 7 species in Japan; see Puthz (1998) regarding a characterization of this group; and see Puthz (2011b) regarding a taxonomic information of this group.
Diagnostic characters are as follows: Head with vertex wide (Fig. 135I); paraglossae coniform;
legs with 4th tarsomere weakly or strongly bilobed; abdomen with lateroventrites existing or
missing; 9th ventrite of male with apicolateral teeth pointed (Fig. 118H); aedeagal median lobe
various in shape; apical parameral area usually thick (Fig. 118B) or mesially with a ﬂap (Fig.

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121B); gonocoxite with apicolateral tooth pointed (Fig. 118I); spermatheca with duct short (Fig.
118G) to moderately long (Fig. 121F).
Key to the Japanese species of S. abdominalis group1(6) Elytron bicolorous, with a pair of yellowish-orange maculae (Fig. 135I); lateroventrites
existing on abdomen.
2(3) Seventh abdominal ventrite posteromedially with a narrow, parallel-sided depression (Fig.
117G); aedeagal median lobe distinctly wider at apicolateral corners than at base (Fig.
117C) ............................................................................................................... S. bicolon Sharp
3(2) Seventh abdominal ventrite posteromedially with a bell-shaped, ﬂat area or shallow depression; aedeagal median lobe distinctly wider at base than at apicolateral corners.
4(5) Elytra dark brown; aedeagus with apical parameral area larger (Fig. 118B); endophallic expulsion hook with posterolateral margin serrate (Fig. 118E) ..........S. coronatus zipanguensis Puthz
5(4) Elytra reddish brown; aedeagus with apical parameral area smaller (Fig. 119B); endophallic
expulsion hook with posterolateral margin simply arcuate (Fig. 119G) ...S. recurvatus Naomi
6(1) Elytron unicolorous, without maculae (Fig. 135L); lateroventrites missing on abdomen.
7(12) Seventh ventrite of male with a shallower depression (Fig. 120D); aedeagal median lobe
pointed apically (Fig. 120A); paramere pallet-like, with a mesial ﬂap at apex (Fig. 120A).
8(9) Endophallic expulsion hook angulate laterally at about posterior 1/3 (Fig. 120G); spermatheca not coiled, with 4 distinct turns (Fig.120E) ......................................................................
....................................................................... S. kamezawai Naomi, Nomura & Puthz sp. nov.
9(8) Endophallic expulsion hook simply arcuate laterally; spermatheca being more or less coiled
so that no distinct turns exist in the duct.
10(11) Aedeagal median lobe with apical sclerotized area pentagonal in shape, angulate laterally
near the middle (Fig. 121B); endophallic basal tube thicker, with ventral projections near
the middle (Fig. 121H) .............................................................................. S. mysticus Sharp
11(10) Aedeagal median lobe with apical sclerotized area subtriangular in shape, almost straightat lateral margin (Fig. 122B); endophallic basal tube thinner, without ventral projections(Fig. 122E) ................................................ S. mystiformis Naomi, Nomura & Puthz sp. nov.
12(7) Seventh ventrite of male with a deeper depression (Fig. 123A); aedeagal median lobe truncate apically (Fig. 123C); paramere simply thin, apically without mesial ﬂap (Fig. 123C).......................................................................................... S. omogoensis Naomi & Watanabe
Stenus bicolon Sharp(Figs. 117A–H, 135I)
Stenus bicolon Sharp, 1889: 328; Herman, 2001: 2081; Naomi & Puthz, 2013: 140; Puthz,
2011b: 592.
Type material examined. Syntype: ♂ (NHML), type locality: Miyanoshita, Kanagawa [examined by Puthz in 1965].
Other material examined. [HONSHU]: 1 ♂, Sengokubara, Hakone, Kanagawa Pref., 25. x.
1985, S. Nomura leg.; 1 ♀, Mt. Azegamaru, Yamakita-machi, Kanagawa Pref., 31. vii. 1993, K.
Haga leg.; 1 ♂, Hirano, Shizuoka City, Shizuoka Pref., 11. xi. 2007, T. Shimada leg. [KYUSHU]:
1 ♂, Mt. Fukuchi, Nogata City, Fukuoka Pref., 10. iv. 1993, S. Nomura leg.; 1 ♂, Fudo Pond,

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Fig. 117. Stenus bicolon Sharp (A, Hirano, Shizuoka; B, C, E, Hakone, Kanagawa; D, F, H, Sata, Kagoshima; G,
Maebaru, Fukuoka). A, 9th and 10th terga of male; B, 9th ventrite of male; C, aedeagus; D, spermatheca; E,
endophallic expulsion hook; F, gonocoxites; G, 7th to 8th ventrites of male. Scale 1: 0.2 mm for A–D, F, H,
0.1 mm for E; scale 2: 0.3 mm for G.

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Maebaru City, Fukuoka Pref., 24. x. 1994, S. Nomura leg.; 1 ♀, Mt. Shiratori, Kumamoto Pref.,25. v. 1981, T. Goto leg.; 1 ♀, Sata-cho, Kagoshima Pref., 30. Iv. 1992, K. Haga leg.
Distribution. Japan (Honshu, Shikoku, Kyushu); Taiwan, Indonesia, Myanmar, Thailand,
Vietnam, Malaysia.
Redescription. Male and female: Macropterous; body 4.0–6.7 mm (fore body 2.2–2.6 mm) in
length, mat, with long antennae. Head and abdomen black; pronotum and elytra dark brown,each elytron with a yellowish-orange, ovoidal macula behind the middle; labrum dark red; antennae yellowish brown to reddish brown, with apical segments infuscate; legs yellowish brown toreddish brown. Head concave dorsally, with a median longitudinal convex area; punctures round,very dense, sometimes irregular. Pronotum with surface uneven; punctures round, very dense,coarse, sometimes weakly rugose. Elytra with surface uneven; punctures round to elliptical, very
dense, coarse. Legs relatively long, slender; tarsi thin, with 4th tarsomere strongly bilobed.
Abdomen relatively wide, subparallel-sided; 9th tergum posteriorly with a very short cleaning
comb (Fig. 117A); 10th tergum very shallowly emarginate posteriorly (Fig. 117A, H); punctures
basically round to elliptical, very dense and small in 3rd to 7th segments but they become
smaller posteriorly toward the 7th, while punctures in 8th segment sparse and very small. Lateroventrites horizontal to dorsomesial in position, narrow and punctate on abdomen.
Male: Seventh ventrite (Fig. 117G) posteromedially with a rather narrow, parallel-sided
depression which is sharply edged laterally, and centrally with an elongate-ovoidal, shallow
depression, which is contiguous with the posteromedian depression; 8th ventrite (Fig. 117G)
medially with an elongate ﬂat area, and posteromedially with an arc-shaped emargination; 9th
tergum (Fig. 117A) elongate, with anterolateral ﬂaps relatively small, ventral apophyses long;
9th ventrite (Fig. 117B) elongate, irregularly serrate posteriorly, with stem subtrapezoidal inshape, apicolateral teeth long, acutely pointed, apicolateral setae long, and macrosetae paired.
Aedeagal median lobe (Fig. 117C) wide and gently rounded laterally in apical half, and roundedapically, with lateral rim and ventral wall rather wide, moderately sclerotized. Endophallic
median longitudinal bands (Fig. 117C) thin, with ventral bands moderately long, dorsal bands
short; expulsion hooks (Fig. 117C, E) separated but connected by a relatively wide plate, withanterior plate demarcated by an oblique suture from posterior plate; basal tube (Fig. 117C) withbasal room composed of paired thin shafts, tube body slender, attenuate but curved at apex. Parameres (Fig. 117C) weakly incurved at base, each provided mesially with a long, low, subtransparent ventral ﬂap from near the base to the apex of paramere; apical area swollen mesially, andfurnished with 20 to 25 setae (mostly short) along the mesial margin.
Female: Eighth ventrite sharply angulate posteromedially; gonocoxites (Fig. 117F) each distinctly serrate posteriorly, with apicolateral tooth acutely pointed, apicolateral setae long. Spermatheca (Fig. 117D) with capsule elongate, rounded apically; RT-duct longer than capsule; spermathecal duct thick, swollen mesially at the most distal part, with two turns; spermathecal glandsmall, elongate-ovoidal, with its opening located at the posterior side of the 2nd turn of the duct.
Biology and ecology. Stenus bicolon is distributed in the plains and mountainous regions inJapan; and the beetles inhabit leaf litter in natural forests.
Remarks. Among the members of S. abdominalis group, Stenus bicolon is allied to the species of S. coronatus complex, which is characterized by the peculiar structure of endophallic
expulsion hooks (i.e., the posteriorly widened hook with its posterolateral margin serrate; Puthz,
2011b: 587). However, S. bicolon is separable from the latter species by having a general type ofendophallic expulsion hooks (i.e., no serration is found at the posterolatral margin). S. bicolon is
also allied to S. recurvatus in that they share the similar external structure and the general type ofThe Steninae of Japan Part 1

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expulsion hooks, but the aedeagal median lobe is much wider and gently rounded laterally in apical half, (Fig. 117C), and the lateral rim and ventral wall of median lobe is rather wide and distinctly sclerotized (Fig. 117C).
Stenus coronatus zipanguensis Puthz(Figs. 118A–I, 135J)
Stenus coronatus Benick, 1928: 245; Herman, 2001: 2144; Naomi & Puthz, 2013: 140.
Stenus coronatus zipanguensis Puthz, 1984b: 176.
Stenus zipanguensis Puthz, 1968b: 47.
Stenus zipanguensis watanabei Puthz, 1968b: 49.
Type material examined. Holotype of S. zipanguensis: ♂ (ZMH), type locality: Odaira[examined by Puthz].
Other material examined. [HONSHU]: 1 ♀, Mt. Keizuru, Katashina-mura, Gunma Pref., 13.
vii. 1996, K. Ishii et al. leg.; 1 ♀, Ayame-daira, Oze Moor, Gunma Pref., 25. vii. 1999, H. Tamura
leg.; 1 ♀, Karikomi pond, Nikko City, Tochigi Pref., 29. vii. 1999, S. Naomi leg.; 1 ♀, Nikkozawa-Kinunuma, Kuriyama-mura, Tochigi Pref., 3. ix. 1991, S. Naomi leg.; 1 ♀, Renge Spa,
Niigata Pref., 20. viii. 1986, M. Sato leg.; 1 ♂, Nishihotaka-guchi, Gifu Pref., 11. vi. 1980, S.
Naomi leg.; 1 ♀, Jigokudani, Mt. Yatsu, Yamanashi Pref., 8. vii. 1982, S. Naomi leg.; 1 ♂,Hirogawara, Hakuho-dani, Yamanashi Pref., 21. vii. 1987, S. Nomura leg.; 1 ♀, same locality,
9–13. vii. 1982, S. Naomi leg.; 1 ♀, Mt. Houo, Nirasaki City, Yamanashi Pref., 13. vi. 1993, K.
Hosoda leg.; 1 ♂, same locality, 15. vii. 1993, K. Hosoda leg.; 1 ♀, same locality, 1. viii. 2008, K.
Hosoda leg.; 1 ♀, Daibosatsu pass, Yamanashi Pref., 9. vi. 1979, M. Tao leg.; 1 ♂1 ♀, same locality, 23. vi. 1985, M. Tao leg.
Distribution. Japan (Honshu).
Redescription. Male and female: Macropterous; body 5.8–7.0 mm (fore body 2.9–3.6 mm) in
length, mat, with antennae moderately long. Head and abdomen black; pronotum and elytra darkbrown (nearly black), each elytron with a yellowish-orange, ovoidal macula behind the middle
but the elytral macula rarely almost missing; labrum dark red; antennae reddish brown to dark
reddish brown; legs reddish brown, with knees more or less infuscate. Head concave dorsally,
with a pair of longitudinal grooves, median longitudinal area between the grooves well convex;
punctures round and very dense on lateral parts of vertex, while punctures on the median convex
area only moderately dense. Pronotum with surface strongly uneven, often with an indistinct
median longitudinal depression; punctures very dense, strongly coarse. Elytra with surface
strongly uneven; punctures round to elliptical, very dense, strongly coarse. Legs relatively long;tarsi thin, with 4th tarsomere strongly bilobed. Abdomen wide; 9th tergum posteriorly with avery short cleaning comb (Fig. 118C); punctures basically round to elliptical, very dense, small
and regular throughout, but they are sparse and very small in one or two posterior segments. Lateroventrites horizontal to ventromesial in position, narrow and punctate on abdomen.
Male: Seventh ventrite (Fig. 118D) posteromedially with a bell-shaped, shallow depression,
which is very weakly emarginate posteriorly; 8th ventrite (Fig. 118D) posteromedially with ashort but elongate ﬂat area in addition to a medium-sized emargination; 9th tergum (Fig. 118C)
with anterolateral ﬂaps small, ventral apophyses relatively long; 9th ventrite (Fig. 118H) elongate, distinctly serrate posteriorly, with stem subtrapezoidal in shape, apicolateral teeth acutely
pointed, apicolateral setae short. Aedeagal median lobe (Fig. 118B) elongate, rounded apicolater-

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Fig. 118. Stenus coronatus zipanguensis Puthz (A–E, H, Hirogawara, Yamanashi; F, G, I, Keizuru, Gunma). A,
endophallic basal tube; B, aedeagus; C, 9th and 10th terga of male; D, 7th to 8th ventrites of male; E, expulsion hooks; F, G, spermatheca; H, 9th ventrite of male; I, gonocoxite. Scale 1: 0.1 mm for A, E, 0.2 mm for I;
scale 2: 0.2 mm for B, C, F–H; scale 3: 0.3 mm for D.

ally, and narrowed behind the apicolateral corners toward the apex which is still relatively wide
and rounded. Endophallic median longitudinal bands (Fig. 118B) with ventral bands moderately
long, thin, dorsal bands short, wide; expulsion hooks (Fig. 118B, E) contiguous only at the posteromesial margin, each hook (comprising the fused anterior and posterior plates) elongate, with
its posterolateral margin irregularly serrate; basal tube (Fig. 118A, B) with basal room elongate-

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ovoidal in shape, submembranous, and tube body consisting of the thick base and the posterior,thin rod almost entirely enveloped by the membrane which is covered regularly with the longitudinal lines of very ﬁne tubercles. Parameres (Fig. 118B) robust, nearly trumpet-shaped; stem provided mesially with a long but very low ventral ﬂap from near the base to the base of apical area;
apical area furnished with 25 to 26 (mostly short) setae along the mesial margin.
Female: Eighth ventrite pointed posteromedially; gonocoxites (Fig. 118I) each irregularly
serrate posteriorly, with apicolateral tooth incurved, pointed, apicolateral setae long. Spermatheca (Fig. 118F, G) with capsule elongate, rounded apically; RT-duct longer and thicker thancapsule; spermathecal duct short, moderately thick to thick, with two distinct turns.
Biology and ecology. Stenus coronatus is distributed in the high mountainous regions of central Honshu in Japan; and the beetles inhabit leaf litter in natural forests.
Remarks. Among the members of S. abdominalis group, Stenus coronatus is allied to S. bilunatus Puthz, 1984b from Taiwan, but this species is separable from the latter by the elytral macula shorter, the metaventrite less deeply impressed (Puthz, 2011b, ﬁgs. 98, 99), and the endophallic expulsion hook with posterolateral margin less strongly serrate (Fig. 118E). S. coronatus
zipanguensis was ﬁrst described as S. zipanguensis by Puthz (1968b) based on one male specimen from Japan (Honshu: Odaira); and after the original description, S. zipanguensis was treatedas a subspecies of S. coronatus by Puthz (1984b). S. coronatus zipanguensis is separable fromthe nominotypical subspecies by the smaller elytral macula and the larger punctation on metathoracic ventrite (Puthz, 2011b, ﬁg. 99).
When a spermatheca of S. coronatus zipanguensis was illustrated by the method as describedin the introductory part, it had the shape as in Fig. 118G. However, when the spermatheca wasembedded into the Euparal, it was found that the RT-duct was bent by two points by contractionof muscles (i.e., contractors) to form a Z-shape as in Fig. 118F. Such deformation of a spermatheca may occur by muscle contraction with the contractors that suddenly absorb some liquid ofa highly concentrated Euparal. Given this, the contraction of the RT-ductal part of spermatheca
seems to be just the same as in in vivo condition, where, by contracting those muscles, a female
individual squeezes the sperm (stored at some apical part of spermathecal duct) out of the duct
into the genital chamber (in order to fertilize the eggs before oviposition).
Eight contractor muscles observed in the spermatheca of S. coronatus zipanguensis are eachthin, and each comprises several muscle ﬁbers. Those contractors mostly originate on the lateralsurface of the (almost non-striped) proximal part of RT-duct, and insert on the mesial surface ofthe capsule or of the striped distal part of RT-duct. Six contractors almost run parallel one
another, but two contractors only weakly cross. Note here that the mesial side of the relatively
long and regularly striped part of RT-duct in Fig, 118G is strongly folded into a point as in Fig.
118F (just like a movement of accordion) after those muscles were strongly contracted.
Stenus recurvatus Naomi(Fig. 119A–G)
Stenus recurvatus Naomi, 2015a: 218.
Type material examined. Holotype: ♂ (EUMJ), Mt. Yonaha, Okinawa Is., Okinawa Pref., 1.
iv. 1999, T. Kan leg.
Distribution. Japan (Nansei Isls.: Okinawa Is.).
Redescription. Male: Brachypterous; body 4.7 mm (fore body 2.1 mm) in length, moderately

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Fig. 119. Stenus recurvatus Naomi (Yonaha, Okinawa Is.). A, elytra; B, aedeagus; C, 9th ventrite of male; D, 9th
and 10th terga of male; E, apex of 8th ventrite of male; F, endophallic basal tube; G, expulsion hook. Scale 1:
0.3 mm for A; scale 1: 0.2 mm for B–E, 0.1 mm for F, G.

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shining, with paraglossae coniform. Head black; pronotum and abdomen dark red to dark brown;
elytra reddish brown, each with a yellowish ovoidal macula behind the middle (Fig. 119A);
labrum black; antennae reddish brown; legs yellowish brown to reddish brown, with knees moreor less infuscate. Head concave between eyes, with a pair of indistinct, longitudinal depressions,median longitudinal area between the depressions convex but low; punctures round, very dense,
various in size, distinct. Pronotum with surface distinctly uneven, median longitudinal depression
moderately deep but indistinct in outline; punctures very dense, rather rough. Elytra with surface
uneven; punctures round to elliptical, very dense, coarse. Legs moderately long; tarsi with 4thtarsomere strongly bilobed. Abdomen relatively wide and ﬂat above; punctures round to nearlyround, dense, distinct and almost regular in anterior segments, while punctures in posterior segments similar to those in anterior ones but distinctly smaller. Lateroventrites horizontal in position, narrow and punctate on abdomen.
Seventh ventrite posteromedially with a small, bell-shaped ﬂat area; 8th ventrite (Fig. 119E)
posteromedially with a wide, V-shaped emargination; 9th tergum (Fig. 119D) with anterolateral
ﬂaps small, ventral apophyses thin, short; 9th ventrite (Fig. 119C) very ﬁnely serrate posteriorly,
with stem subtrapezoidal in shape, apicolateral teeth long, acutely pointed, apicolateral setae
short; 10th tergum (Fig. 119D) entire. Aedeagal median lobe (Fig. 119B) obtuse at apicolateralcorners, and then strongly narrowed toward the apex which is still wide and rounded. Endophallic median longitudinal bands (Fig. 119B) moderately long; lateral longitudinal bands thin, distinct (Fig. 119B); expulsion hooks (Fig. 119B, G) widely separated but connected by a thin,arched rod, with anterior plate demarcated by an oblique suture from posterior plate; basal tube
(Fig. 119B, F) with basal room elongate-ovoidal in shape, submembranous, tube body baculiform, thick, and almost covered regularly with the longitudinal lines of very ﬁne dots. Parameres(Fig. 119B) each thick, weakly recurved apically; apical area very long and large, and furnishedwith 22 to 23 short, thin setae along the mesial margin.
Female. Unknown.
Biology and ecology. Stenus recurvatus is presently distributed in the mountainous region of
Okinawa Is.; and one male beetle was only once collected from leaf litter in a natural forest.
Remarks. Stenus recurvatus is a species which was only recently discovered from Okinawa(Naomi, 2015). This species is allied to, and also similar in external structure to the members of
S. coronatus complex (Puthz, 2011b), but it is separable from the latter species by the posterolateral margin of endophallic expulsion hook simply arcuate, without serration (Fig. 119B, G). S.
recurvatus is also allied to S. bicolon, but the 7th abdominal ventrite is posteromedially provided
with a small, bell-shaped ﬂat area, and the aedeagal median lobe is narrow and narrowed apicallyin apical half (Fig. 119B).
Stenus kamezawai Naomi, Nomura & Puthz sp. nov.
(Figs. 120A–H, 135K)
Type material examined. Holotype: ♂ (NSMT-I-C-200323 in NMNST), Mt. Kojin, Nara
Pref., 16. viii. 1965, T. Ito leg. Paratype [HONSHU]: 1 ♀ (cP), Mt. Obako, Nara Pref., 23. iii.
2006, T. Lackner leg.
Distribution. Japan (Honshu: Nara Pref.).
Description. Male and female: Macropterous; body 4.0–4.3 mm (fore-body 2.0–2.1 mm) in
length, weakly shining, with antennae short. Body black; labrum black; antennae reddish brownto dark reddish brown; legs yellowish brown to reddish brown, with knees infuscate. Head con-

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Fig. 120. Stenus kamezawai Naomi, Nomura & Puthz sp. nov. (A–D, G, H, Kojin, Nara; E, F, Obako, Nara). A,
aedeagus; B, 9th and 10th terga of male; C, 9th ventrite of male; D, 7th to 8th ventrites of male; E, spermatheca; F, gonocoxite; G, endophallic expulsion hook; H, basal tube. Scale 1: 0.1 mm for A; scale 2: 0.2 mm for
B, C, 0.1 mm for E–H; scale 3: 0.3 mm for D.

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cave dorsally, with a pair of longitudinal depressions, median longitudinal area between the
depressions weakly convex; punctures round, dense to very dense, various in size, somewhat
umbilicate. Pronotum with surface strongly uneven, with median longitudinal depression indistinct in outline; punctures rugose, strongly coarse. Elytra with surface strongly uneven; puncturessubrugose, coarse. Legs with femora thick; tarsi thin, with 4th tarsomere weakly bilobed. Abdomen weakly narrowed posteriorly; punctures round to elliptical, sparse to moderately dense, various in size, and irregular in anterior segments, while punctures in posterior segments sparse, verysmall and irregular. Lateroventrites missing but tergoventrite sutures existing on abdomen.
Male: Seventh ventrite (Fig. 120D) posteromedially with a shallow, elongate-bell-shaped
depression, which is very weakly emarginate posteriorly; 8th ventrite (Fig. 120D) posteromedially with a triangular emargination; 9th tergum (Fig. 120B) with anterolateral ﬂaps wide, ventral
apophyses short; 9th ventrite (Fig. 120C) ﬁnely serrate posteriorly, with stem rounded anteriorly,
apicolateral teeth acutely pointed, apicolateral setae moderately long, and macrosetae paired.
Aedeagal median lobe (Fig. 120A) elongate, acutely pointed apically, with apical sclerotized area
elongate-subtriangular in shape. Endophallic median longitudinal bands (Fig. 120A) with ventral
bands long, dorsal bands moderately long; lateral longitudinal bands short, thin (Fig. 120A);
expulsion hooks (Fig. 120G) separated but connected by a submembranous band, each hookangulate laterally at about posterior 1/3, and acutely pointed posteriorly; basal tube (Fig. 120H)with tube body baculiform, thick proximally, with a pair of asymmetrical projections a little
behind the middle. Parameres (Fig. 120A) well-developed; stem very weakly sinuous, ventrallywith 2 thin setae before apical area; apical area with a ﬂap which is rounded mesially, and furnished ventrally with 2 to 3 thin setae, and also with 15 to 17 moderately thick setae along themesial margin of ﬂap.
Female: Eighth ventrite rounded posteriorly; gonocoxites (Fig. 120F) each serrate posteriorly, with apicolateral tooth thin, acutely pointed, apicolateral setae moderately long. Spermatheca (Fig. 120E) with capsule small; RT-duct short; spermathecal duct moderately long, with 4
turns; basal valve a little shorter than basal sclerotized duct; basal pouch bowl-shaped.
Biology and ecology. Stenus kamezawai is presently distributed only in the mountainous
regions of Kii Peninsula. No solid information is obtained regarding the habitats of this species.
Remarks. Stenus kamezawai is closely allied to S. mysticus and S. mystiformis, but this species is separable from the latter two species by the endophallic expulsion hook angulate laterally
at about posterior 1/3 (Fig. 120G), and the spermatheca not coiled, with 4 distinct turns(Fig.120E).
Etymology. This species is named in honour of our friend and coleopterist, Mr. Hiromu
Kamezawa (Kawagoe).
Stenus mysticus Sharp(Figs. 121A–H, 135L)
Stenus mysticus Sharp, 1889: 330; Herman, 2001: 2294; Naomi & Puthz, 2013: 140.
Type material. Syntypes: 2 ♂ (NHML), 1 ♂ (FMC), type locality; Nikko (Tochigi).
Other material examined. [HOKKAIDO]: 1 ♀, Ishikari, 6. viii. 1962, K. Mizusawa leg.; 1 ♂,Washippu River, Ashoro-machi, 10. vii. 2002, K. Haga leg.; 1 ♀, Ashoro-machi, 15. vii. 1999, K.
Haga leg. [HONSHU]: 2 ♂, Yachi, Mt. Hakkoda, Aomori Pref., 6. viii. 1964, K. Sakai leg.; 1 ♂,Mt. Ohkura, Yamato-cho, Miyagi Pref., 29. xi. 2009, T. Ozaki leg.; 1 ♂, Mt. Asahi, Yamagata

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Fig. 121. Stenus mysticus Sharp (A, B, D, G, H, Teruha, Gunma; C, Abe, Shizuoka; E, Ashoro, Hokkaido; F,
Karuizawa, Nagano). A, 9th ventrite of male; B, aedeagus; C, 7th to 8th ventrites of male; D, endophallic
expulsion hook; E, apex of gonocoxite; F, spermatheca; G, 9th and 10th terga of male; H, basal tube. Scale 1:
0.1 mm for A; scale 2: 0.2 mm for B, G, 0.1 mm for D–F, H; scale 3: 0.3 mm for C.

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Pref., 9. viii. 1969, Y. Kimura leg.; 1 ♂, Yunohara-machi, Showa-mura, Fukushima Pref., 9. vi.
2013, K. Haga leg.; 1 ♂, Onabe, Iwase, Fukushima Pref., 14. viii. 1950, K. Nagayama leg.; 1 ♂,Futamata River, Tenei-mura, Fukushima Pref., 4. vi. 2005, K. Haga leg.; 1 ♂ (cP), Kurigahara,
Japan, 4. viii.-6. viii. 1881, G. Lewis (1910-320); 1 ♂1 ♀, Tanbara Highland, Gunma Pref., 15.
ix. 2004, M. Yasaka leg.; 1 ♂, Teruha Valley, Minakami-cho, Gunma Pref., 2. viii. 2009, S.
Tsuyuki leg.; 1 ♀, Senjyo-gahara, Oku-nikko, Tochigi Pref., 26. vi. 2009, S. Tsuyuki leg.; 1 ♂1 ♀,Ogawadani, Nippara, Okutama-machi, Tokyo Metropolis, 24. iii. 2007, H. Kamezawa leg.; 1 ♀,Daibosatsu Pass, Yamanashi Pref., 20. v. 1961, K. Mizusawa leg.; 1 ♀, Gozaishi Spa, Yamanashi
Pref., 5. vi. 1991, K. Hosoda leg.; 1 ♂, Abe Pass, Shizuoka Pref., 11. xi. 2007, Y. Tahira leg.; 1 ♂,Koike, Ohno, Fukui Pref., 4. vi. 1983, H. Sasaji leg.; 1 ♀, Karuizawa, Nagano Pref., Japan, iv.08; 1 ♂, Kitanomata-Rindo, Kamioka, Gifu Pref., 23. vii. 2000, Y. Takai leg.; 1 ♂, Uradani, Shitara-cho, Aichi Pref., 10. iv. 1994, H. Yoshitomi leg.
Distribution. Japan (Hokkaido, Honshu).
Redescription. Male and female: Macropterous; body 3.9–4.3 mm (fore body 2.0–2.1 mm) in
length, weakly shining, with antennae short. Body black; labrum black; antennae reddish brownto dark reddish brown; legs reddish brown, with knees more or less infuscate. Head moderately
concave dorsally, with a pair of longitudinal grooves, median longitudinal area between thegrooves weakly convex; punctures round, dense to very dense, somewhat umbilicate. Pronotumwith surface strongly uneven, with a median longitudinal depression running in posterior 2/3 ofpronotum and moderatey deep at the central part; punctures very dense, strongly coarse. Elytra
with surface strongly uneven; punctures very dense, subrugose, coarse. Legs with femora thick;tarsi thin, with 4th tarsomere weakly bilobed. Abdomen weakly narrowed posteriorly; 9th tergum
posteriorly with a highly obsolete cleaning comb (Fig. 121G); punctures round to elliptical, moderately dense to dense, various in size, and irregular in anterior segments, while punctures in posterior segments elliptical, sparse to moderately dense, and very small to small. Lateroventrites
missing, but tergoventrite sutures existing on abdomen.
Male: Seventh ventrite (Fig. 121C) posteromedially with a bell-shaped, shallow depression,
which is very weakly emarginate posteriorly; 8th ventrite (Fig. 121C) posteromedially with a triangular emargination; 9th tergum (Fig. 121G) with anterolateral ﬂaps wide, ventral apophyses
long; 9th ventrite (Fig. 121A) irregularly serrate posteriorly, with stem rounded anteriorly, apicolateral teeth acutely pointed, apicolateral setae moderately long, and macrosetae paired. Aedeagal
median lobe (Fig. 121B) subovoidal basally, acutely pointed apically, with apical sclerotized area
almost pentagonal in shape. Endophallic median longitudinal bands (Fig. 121B) with ventral
bands long, each narrowed apically, dorsal bands wider and shorter than ventral bands; expulsion
hooks (Fig. 121B, D) widely separated but connected by a submembranous band, each hookpointed posteriorly; basal tube (Fig. 121B) with tube body baculiform, curved left near the middle where a pair of asymmetrical projections are found ventrally, the right projection larger thanleft one (Fig. 121H). Parameres (Fig. 121B) slender, very weakly incurved; apical area relatively
short, mesially with a dorsal ﬂap, and furnished apically with 6 to 7 moderately long, thin setae,
ventrally with 2 to 3 thin setae, and also with 9 to 12 setae along the mesial margin of dorsal ﬂap.
Female: Eighth ventrite angulate posteromedially; gonocoxites (Fig. 121E) each distinctly
serrate posteriorly, with apicolateral tooth acutely pointed, apicolateral setae moderately long.
Spermatheca (Fig. 121F) with capsule very small; RT-duct short, thick; spermathecal duct moderately long and loosely coiled; basal valve short; basal sclerotized duct about 2 times as long as
basal valve; basal pouch sclerotized, conical in shape.
Biology and ecology. Stenus mysticus is widely distributed in the mountainous regions of306

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Hokkaido and Honshu, but it is not necessarily a common species. The beetles seem to inhabit
leaf litter in natural forests. However, it was observed that the beetles hibernated under the barkof a dead beech tree at Abe Pass, Shizuoka; and they are also collected from the dead standing
trees at Nippara, Tokyo (per. com. with Kamezawa). These observations (in addition to the collecting records described above) may suggest that this and related species (i.e., S. kamezawai, S.
mystiformis and S. omogoensis) inhabit dead (standing and fallen) trees (e.g., under barks).
Remarks. Stenus mysticus is closely allied to S. mystiformis, but this species is separablefrom the latter by the aedeagal median lobe with apical sclerotized area pentagonal in shape, andangulate laterally near the middle (Fig. 121B), the endophallic expulsion hook with anterior partthicker, and more weakly curved laterally (Fig. 121D), and the basal tube thicker, with ventral
projections near the middle (Fig. 121H)
Stenus mystiformis Naomi, Nomura & Puthz sp. nov.
(Figs. 122A–H, 136A)
Type material examined. Holotype: ♂ (NSMT-I-C-200324 in NMNST), Minokoshi, Mt. Tsurugi, Tokushima Pref., 6. iv. 1968, M. Yoshida leg. Paratypes: 1 ♀ (cN), same data as holotype;
1 ♂ (cN), Mt. Odami, Ehime Pref., 10. iv. 1992, E. Yamamoto leg.; 1 ♂ (cN), Shiiba-goe,Fudono, Shiiba, Miyazaki Pref., 25. vii. 2015, T. Watanabe leg.; 1 ♂ (cN), Mt. Ohira, Kuma-gun,
Kumamoto Pref., 30. xii. 1981, I. Ohtsuka leg.
Distribution. Japan (Shikoku, Kyushu).
Description. Male and female: Macropterous / brachypterous; body 4.2–4.5 mm (fore body
1.9–2.1 mm) in length, weakly shining, with antennae short. Head and abdomen black; pronotumand elytra dark reddish brown (nearly black); labrum black; antennae reddish brown to dark reddish brown; legs reddish brown, with knees more or less infuscate. Head shallowly concave dorsally, with a pair of longitudinal depressions; punctures round, very dense and somewhat umbilicate on head, but the central or narrow median longitudinal area impunctate. Pronotum withsurface strongly uneven, median longitudinal depression moderately deep but indistinct in outline; punctures very dense, strongly coarse. Elytra with surface strongly uneven; punctures very
dense, subrugose, coarse. Legs with tarsi thin, 4th tarsomere weakly bilobed. Abdomen weakly
narrowed posteriorly; punctures round to elliptical, moderately dense to dense, various in size
and irregular in anterior segments, while punctures in posterior segments sparse, very small. Lateroventrites missing, but tergoventrite sutures existing on abdomen.
Male: Seventh ventrite (Fig. 122G) posteromedially with a shallow, elongate-bell-shaped
depression, which is very weakly emarginate posteriorly; 8th ventrite (Fig. 122G) posteromedially with a triangular emargination; 9th tergum (Fig. 122D) with anterolateral ﬂaps relatively
wide, ventral apophyses long; 9th ventrite (Fig. 122A) distinctly serrate posteriorly, with stem
rounded anteriorly, apicolateral teeth acutely pointed, apicolateral setae moderately long, andmacrosetae paired. Aedeagal median lobe (Fig. 122B) elongate, pointed apically, with apicalsclerotized area almost triangular in shape. Endophallic median longitudinal bands (Fig. 122B)
with ventral bands long, dorsal bands wider and shorter than ventral bands; expulsion hooks (Fig.
122B, H) separated but connected by a submembranous band, each hook pointed posteriorly;
basal tube (Fig. 122B) with basal room small, subovoidal, tube body long, baculiform, and sometimes weakly curved left apically (Fig. 122E). Parameres (Fig. 122B) with stem very weakly sinuous, ventrally with 2 thin setae a little before apical area; apical area mesially with a ﬂap, andfurnished ventrally with 2 thin setae, and with 15 to 18 moderately thick setae along the mesial

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Fig. 122. Stenus mystiformis Naomi, Nomura & Puthz sp. nov. (A–F, H, Tsurugi, Tokushima; G, Odami, Ehime)
A, 9th ventrite of male; B, aedeagus; C, spermatheca; D, 9th and 10th terga of male; E, endophallic basal
tube; F, apex of gonocoxite; G, 7th to 8th ventrites of male; H, expulsion hook. Scale 1: 0.2 mm for A; scale 2:
0.2 mm for B, D, 0.1 mm for C, E, F, H; scale 3: 0.3 mm for G.

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margin of ﬂap.
Female: Eighth ventrite obtusely angulate posteromedially; gonocoxites (Fig. 122F) eachdistinctly serrate posteriorly, with apicolateral tooth acutely pointed, apicolateral setae long.
Spermatheca (Fig. 122C) with capsule small, narrow; RT-duct long, thick; spermathecal duct
moderately long, loosely coiled; basal valve short; basal sclerotized duct long; basal pouch sclerotized.
Biology and ecology. Stenus mystiformis is presently distributed in the mountainous regionsof Shikoku and eastern part of Kyushu. No solid information is obtained regarding the habitats ofthis species.
Remarks. Stenus mystiformis is allied to S. mysticus, but this species is separable from thelatter by the aedeagal median lobe with apical sclerotized area subtriangular in shape, and almost
straight at lateral margin (Fig. 122B), the endophallic expulsion hook with anterior part thinner,and more strongly curved laterally (Fig. 122H), and the basal tube thinner, without ventral projections (Fig. 122E). Only 3 male specimens were examined in this study, but the endophallic
basal tubes show variations. For example, the tube body is weakly curved left apically (Fig.
122E) in the specimen from Minokoshi, but it is not curved apically in the specimen from
Odami, while in the specimen from Shiiba, the tube body has a little wider apical part, with anarrow and short tube at the apicalmost part. These 3 specimens, however, basically show thesame condition regarding other important taxonomic characters (e.g., shape of aedeagal median
lobe, structure of endophallic expulsion hook); and thus the variations are here considered to be
infraspeciﬁc ones.
Etymology. The speciﬁc epithet of this new species is derived from the combination of a
Latin stem “mysti-” (mysticus) which means “mystic” or “relating to the mysteries” ＋ a Latin participle “-formis” which means “-formed”. This is because the new species has a similar habitus of
S. mysticus Sharp.
Stenus omogoensis Naomi & Watanabe(Fig. 123A–G)
Stenus omogoensis Naomi & Watanabe, 2015: 96.
Type material examined. Holotype: ♂ (TUAA), Omogo-kei, Ehime Pref., 20. iv. 1963, S.
Tachikawa leg. Paratype: 1 ♀ (TUAA), same data as holotype.
Other material examined. 1 ♀ (TUAA), Omogo Valley, Ehime Pref., 20. iv. 1963, S.
Tachikawa leg.; 1 ♀ (cN), Mt. Ishizuchi, Ehime Pref., 1. ix. 1991, I. Okamoto leg.
Distribution. Japan (Shikoku: Ehime Pref.).
Redescription. Male and female: Macropterous; body 3.9–4.0 mm (fore body 2.1–2.2 mm) in
length, elongate, weakly shining. Body black; antennae and legs yellowish brown to reddish
brown. Head with a pair of shallow, longitudinal depressions; punctures dense, distinct, and various in shape and size. Pronotum with surface slightly uneven, median longitudinal depression
shallow, very indistinct in outline; punctures round, very dense, various in size, rough. Elytra
with punctures very dense, rough, partly rugose. Legs with femora relatively thick; tarsi with 4thtarsomere short, weakly bilobed. Abdomen narrowed posteriorly; punctures round to elliptical,
moderately dense, various in size, and distinct in anterior segments, while punctures in posterior
segments ovoidal, sparse to relatively dense, and small. Lateroventrites missing, but tergoventrite
sutures existing on abdomen.

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Fig. 123. Stenus omogoensis Naomi & Watanabe (Omogo, Ehime). A, 6th to 8th ventrites of male; B, apex of
gonocoxite; C, aedeagus; D, 9th and 10th terga of male; E, 9th ventrite of male; F, endophallic expulsion
hook; G, spermatheca. Scale 1: 0.3 mm for A; scale 2: 0.1 mm for B, F, G; scale 3: 0.2 mm for C–E.

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Male: Fifth ventrite posteromedially with a small, semicircular ﬂat area, which is very shallowly emarginate; 6th ventrite (Fig. 123A) with a semicircular depression, which is moderately
emarginate posteriorly; 7th ventrite (Fig. 123A) posteromedially with a large, deep depression,
which is open anteriorly, emarginate posteriorly, and also strongly ridged laterally; 8th ventrite(Fig. 123A) posteromedially with a V-shaped emargination; 9th tergum (Fig. 123D) with apicolateral ﬂaps angulate apically, ventral apophyses moderately thick and long; 9th ventrite (Fig.
123E) very ﬁnely or hardly serrate posteriorly, with stem obtusely pointed anteriorly, apicolateral
teeth acutely pointed, apicolateral setae short, and macrosetae short; 10th tergum (Fig. 123D)
entire. Aedeagal median lobe (Fig. 123C) weakly bi-sinuate behind the middle, distinctly truncate apically, with apical sclerotized area long, narrowed toward the truncate apex. Endophallic
median longitudinal bands (Fig. 123C) with ventral bands very long, dorsal bands short, thin; lateral longitudinal bands (Fig. 123C) thin, incurved; explusion hooks (Fig.123C) fused to form anearly X-shaped sclerite, with anterior plate partially demarcated by a short lateral incision fromposterior plate which is hatchet-shaped (Fig. 123F); basal tube (Fig. 123C) thin, tube body rodlike but with a low ﬂap at the right middle part. Parameres (Fig. 123C) relatively short, each notreaching posteriorly the apex of median lobe, weakly incurved apically, and rounded at the apicalmost part; stem relatively thick basally; apical area short, not swollen mesially, and furnishedmesially with 10 to 11 almost dense setae.
Female: Eighth ventrite rounded posteriorly; gonocoxites (Fig. 123B) each weakly serrate
posteriorly, with apicolateral tooth large, acutely pointed. Spermatheca (Fig. 123G) with capsulethick, rounded apically; RT-duct thick; spermathecal duct moderately coiled, moderately longand thick; basal valve very short; basal sclerotized duct simple; basal pouch conical.
Biology and ecology. S. omogoensis is a very rare Stenus species, which was discovered only
recently (Naomi & Watanabe, 2015). It is presently distributed only in the mountainous region ofwestern part of Shikoku. No solid information is obtained regarding the habitats of this species.
Remarks. Stenus omogoensis is allied to S. mysticus and its related species newly describedabove, but this species is easily separable from the latter 3 species by the aedeagal median lobe
distinctly truncate apically (Fig. 123C).
Species group of S. sharpi Bernhauer & Schubert
S. sharpi group (tentative species group name) consists of 1 species in Japan. Diagnostic
characters are as follows: Labium with paraglossae elongate-oval (Fig. 2bA–D); legs with 4thtarsomere strongly bilobed; lateroventrites dorsomesial or horizontal in position, very thin; 9th
tergum of male posteriorly with an obsolete cleaning comb (Fig. 124A); 9th ventrite of male withapicolateral teeth pointed (Fig. 124B); aedeagal median lobe wide, with wide lateral rims (Fig.
124C); endophallic explusion hooks separated (Fig. 124E); basal tube very slender, long (Fig.
124C); gonocoxite with apicolateral tooth pointed (Fig. 124H); spermatheca with duct very long,coiled (Fig. 124D).
Stenus sharpi Bernhauer & Schubert(Figs. 124A–H, 136B–D)
Stenus sharpi Bernhauer & Schubert, 1911: 185 (as replacement name of S. palpalis Sharp); Herman, 2001: 2388; Puthz, 2008a: 173; Naomi & Puthz, 2013: 140.
Stenus palpalis Sharp, 1889: 329. (A homonym of S. palpalis Erichson, 1840.)

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Fig. 124. Stenus sharpi Bernhauer & Schubert (A, B, F, Nishihotaka-guchi, Gifu; C, E, Daibosatsu, Yamanashi;
D, H, Moto-kiyosumi, Chiba; G, Shiroiwa, Miyazaki). A, 9th and 10th terga of male; B, 9th ventrite of male;C, aedeagus; D, spermatheca; E, endophallic expulsion hook; F, 7th to 8th ventrites of male; G, apex of
aedeagal paramere; H, apices of gonocoxites. Scale 1: 0.2 mm for A–C, H, 0.1 mm for E, G; scale 2: 0.1 mm
for D; scale 3: 0.3 mm for F.

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Type material examined. Syntype of S. palpalis: ♂ (NHML), type locality: Ichiuchi, Lewis[examined by Puthz in 1968].
Other material examined. [HONSHU]: 1 ♀, Towada, Aomori Pref., 4. viii. 1987, S. Nomura
leg.; 1 ♀, Urabandai, Fukushima Pref., 9. vii. 1985, S. Nomura leg.; 2 ♀, Yumoto, Oku-Nikko,
Tochigi Pref., 29. vi. 1982, S. Naomi leg.; 2 ♂, same locality, 10. vii. 1994, S. Naomi leg.;1 ♂1 ♀, Chuzenji, Nikko, Tochigi Pref., 24. vii. 1985, S. Nomura leg.; 3 ♂1 ♀, NikkozawaKinunuma, Kuriyama-mura, Tochigi Pref., 3. ix. 1991, S. Naomi leg.; 1 ♀, Kawaho, Tochigi
Pref., 4. vi. 1980, K. Kawada leg.; 1 ♂, Numappara, Mt. Nasu, Tochigi Pref., 4. vi. 1994, S.
Naomi leg.; 2 ♂5 ♀, Kaminikkawa Pass, Mt. Daibosatsu, Yamanashi Pref., 15-18. vii. 1982, S.
Naomi leg.; 1 ♀, same locality, 9. vi. 1979, M. Tao leg.; 1 ♂, Mt. Daibosatsu, Yamanashi Pref.,22-23. vi. 1985, M. Sato leg.; 3 ♂3 ♀, Hirogawara, Mt. Shirane, Yamanashi Pref., 9-13. vi. 1982,
S. Naomi leg.; 1 ♂, Sasagamine, Mt. Myoko, Niigata Pref., 14-15. vi. 1980, S. Naomi; 2 ♂4 ♀,Nishihotaka-guchi, Gifu Pref., 11. vi. 1980, S. Naomi leg.; 1 ♀, Hirayu, Gifu Pref., 22. vii. 1946,
K. Ohbayashi leg.; 1 ♀, Ohdaigahara, Nara Pref., 29. v. 1985, S. Nomura leg.; 1 ♂, Mt. Sanjyo,
Tenkawa-mura, Nara Pref., 28. vi. 1988, S. Nomura leg. [SHIKOKU]: 1 ♂6 ♀, Mt. Tsurugi,
Tokushima Pref., 15-17. x. 1980, S. Naomi leg.; 1 ♀, Mt. Takashiro, Tokushima Pref., 17. vii.
1988, M. Sakai leg.; 1 ♀, Omogo Valley, Ehime Pref., 15. vi. 1981, S. Naomi leg.; 1 ♀, same
locality, 9. x. 1990, S. Nomura leg.; 1 ♀, Mt. Ishizuchi, Ehime Pref., 16. vi. 1981, S. Naomi leg.
[KYUSHU]: 1 ♀, Mt. Kurodake, Kuju, Ohita Pref., 3. ix. 1982, S. Nomura leg.; 1 ♂, Makinoto
Pass, Ohita Pref., 10. viii. 1979, S. Naomi leg.; 1 ♀, Mt. Kuju, Ohita Pref., 23. ix. 1980, H. Makihara leg.; 1 ♀, Shimoda, Amakusa Is., Kumamoto Pref., 7. vii. 1997, H. Ohishi leg.; 1 ♂1 ♀, Mt.
Shiroiwa, Miyazaki Pref., 6. viii. 1978, S. Imasaka leg.; 1 ♀, Aya-minami, Miyazaki Pref., 9. v.
1985, S. Nomura leg.; 1 ♀, Miike Pond, Mt. Kirishima, Kagoshima Pref., 18. v. 1983, Y. Sawada
leg.
Distribution. Japan (Honshu, Shikoku, Kyushu); Korea, China, Russia.
Redescription. Male and female: Brachypterous; body 5.0–6.5 mm (fore body 2.5–3.1 mm)
in length, strongly shining, with antennae long, thin. Head and abdomen black; pronotum andelytra dark red (nearly black); labrum black; antennae and legs clear reddish brown. Head relatively short, vertex wide, concave, with paired longitudinal grooves, median longitudinal area
between the grooves wide, moderately convex; punctures round, moderately dense to dense, various in size, and somewhat umbilicate on head, but punctures often sparse and small on medianconvex area. Pronotum with surface strongly uneven, median longitudinal depression very indistinct in outline; punctures very dense, coarse. Elytra with surface strongly uneven, punctures
dense, strongly coarse. Legs moderately long; tarsi with 4th tarsomere strongly bilobed. Abdomen subparallel-sided; 9th tergum posteriorly with a cleaning comb composed of very short, relatively sparse setae (Fig. 124A); punctures round, moderately dense, and various in size in anterior segments, while punctures in posterior segments very small and sparse. Lateroventrites
dorsomesial or horizontal in position, very thin on abdomen.
Male: Seventh ventrite (Fig. 124F) posteromedially with a bell-shaped, ﬂat area; 8th ventrite(Fig. 124F) posteromedially with a small emargination; 9th tergum (Fig. 124A) with apicolateral
ﬂaps relatively small, ventral apophyses relatively short, posterolateral projections very short;
9th ventrite (Fig. 124B) ﬁnely serrate posteriorly, with stem triangular, pointed anteriorly, apicolateral teeth large, acutely pointed, apicolateral setae relatively short, macrosetae paired; 10th tergum (Fig. 124A) entire. Aedeagal median lobe (Fig. 124C) wide, widest apicolaterally, with lateral rims very wide, sclerotized, apicomedian projection short, and apical sclerotized area with a
median longitudidinal keel. Endophallic median longitudinal bands (Fig. 124C) with ventral

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bands short, thin, dorsal bands moderately long and wide; lateral longitudinal bands (Fig. 124C)
short, thin; explusion hooks (Fig.124C, E) separated but connected by a thin, curved rod, withanterior plate demarcated by oblique line from posterior plate; basal tube (Fig. 124C) with basal
room short, composed of two short shafts, tube body very long, slender, subulate. Parameres(Fig. 124C) thin, slender; apical area moderately long, with a ventral ﬂap, and furnished with 5
or 6 setae along the mesial margin of ventral ﬂap, dorsally with 3 or 4 setae, and sometimes alsowith 1 or 2 setae at the mesial side of stem just before the apical area (Fig. 124G).
Female: Eighth ventrite rounded posteriorly; gonocoxites (Fig. 124H) each irregularly serrate
posteriorly, with apicolateral tooth long, acutely pointed, apicolateral setae moderately long.
Spermatheca (Fig. 124D) with capsule very small, rounded apically; RT-duct thick, long; spermathecal duct thin, very long, moderately coiled; basal submenbranous duct (valve?) long, about
2 times as long as basal sclerotized duct.
Biology and ecology. S. sharpi is a common Stenus species in Japan. It is widely distributedin the plains and mountainous regions. The beetles inhabit leaf litter in natural forests; they also
live in the relatively dry grass or bamboo litter heaped around the margins of forests.
Remarks. Stenus sharpi is the sister species of S. davidsharpi Puthz, 2008a from Taiwan.
This species is separable from the latter by the vertex of head covered with smaller, less dense
punctures, the elytra with punctures on less rugose, the 8th ventrite of male posteromedially witha smaller emargnation (Fig. 124F), and the aedeagal paramere thinner, with its apical area furnished only with 8 to 10 setae (Fig. 124C). As in S. davidsharpi (Puthz, 2008a, ﬁg. 64), S. sharpi
has a ventral ﬂap at the apical area of aedeagal paramere (Fig. 124G). The ﬂap basically lies
almost dorso-ventrally; in other words it turns toward the mesio-ventral direction. Thus, it may
be overlooked when the aedeagus is observed from ventral aspect (e.g., Fig. 124C).
Since S. sharpi has a cleaning comb (comprising “very short and relatively sparse setae”) in
the 9th tergum (Fig. 124A) although it is brachypterous, we shortly here discuss the matter on it.
S. sharpi is widely distributed in Japan from Honshu, Shikoku and Kyushu, but among the local
populations, no morphological variation is basically found regarding the structure of aedeagus(including endophallus) as well as external structure of body. This is striking, when comparing itwith many brachypterous species of S. cephalotes group and of S. asyura group, because the species of latter two groups had highly speciated in various regions of Japan in many cases, so thatthey each have a relatively or highly limited distributional range (e.g., Naomi, 2006b).
The fact that no signiﬁcant morphological diversiﬁcation had occurred among the isolated
local populations of S. sharpi may suggest a relatively short evolutionary span of S. sharpi-species lineage. Furthermore, it seems also that only relatively short evolutionary times have passed
after S. sharpi had become brachypterous so that it loses its ﬂight function. This may be a reason
why S. sharpi has (or retains) the cleaning comb in the 9th tergum although it is brachypterous.
An obsolete (or non-functional) condition of setae comprising the comb in S. sharpi may support
the afore-mentioned hypothesis on the retention of a cleaning comb in the brachypterous species.
Etymology. This species was named in honour of Dr. David Sharp who is an eminent coleopterist and morphologist in England.
Species group of S. gestroi Fauvel
S. gestroi group consists of 1 species in Japan; see Puthz (2011b) regarding a characterizationof this group. Diagnostic characters are as follows: Head with vertex deeply concave (Fig.
136E); eyes very large; legs with 4th tarsomere strongly bilobed; elytron mostly with a yellow-

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ish-orange spot; lateroventrites very narrow, and existing only at the basal parts of 3rd to 6th segments; 9th ventrite of male with apicolateral teeth pointed (Fig. 125D); aedeagal median lobe
mostly furnished laterally with sparse, short setae (Fig. 125B; Puthz, 2011b, ﬁg. 17); parameral
stem mostly furnished mesially with several, short setae (Fig. 125B); endophallus often with asmall triangular or arrow-headed expulsion hook (Fig. 125B; Puthz, 2011b, ﬁg. 13); gonocoxitewith apicolateral tooth acutely pointed (Fig. 125G); spermatheca composed of distal duct
(C-shaped) and proximal duct (loosely coiled, more or less thin) (Fig. 7B, 125C; Puthz, 2011b,
ﬁgs. 8, 9).
Stenus gestroi Fauvel(Figs. 2aE, F, 125A–H, 136E–J)
Stenus gestroi Fauvel, 1895: 212; Herman, 2001: 2200; Naomi & Puthz, 2013: 140; Puthz, 2011:566b; Puthz, 2013: 1369.
Stenus takara Nakane, 1963a: 21.
Type material examined. Lectotype: ♂ (IRSNB), type locality: Carin Cheba, Myanmar [designated by Puthz in 1969: 36].
Other material examined. [KYUSHU]: 1 ♂, Uchinoura-cho, Kagoshima Pref., 4. v. 1997, K.
Haga leg. [NANSEI ISLS.]: 1 ♂, Shiratani Valley, Yaku Is., Kagoshima Pref., 20. vii. 1975, Y.
Mori leg.; 4 ♂3 ♀, Nakanoshima Is., Tokara, Kagoshima Pref., 28. iv. 1987, S. Nomura leg.; 1 ♂,same locality, 2. v. 1987, S. Nomura leg.; 1 ♂, same locality, 10. viii. 1975, H. Makihara leg.;1 ♀, Takara Is., Tokara, 22. vi. 1973, H. Makihara leg.; 1 ♂4 ♀, Naze City, Amami Is.,
Kagoshima Pref., 25. iii. 1978, S. Naomi leg.; 4 ♀, Hatsuno, Amami Is., Kagoshima Pref., 27. iii.
1978, S. Naomi leg.; 1 ♂, Yamatohama, Amami Is., Kagoshima Pref., 24. iii. 1978, S. Naomi
leg.; 1 ♀, Amami Is., Kagoshima Pref., 19. iv. 1974, H. Makihara leg.; 1 ♀, Koniya, Amami Is.,
Kagoshima Pref., 12. vii. 1978, M. Kaneda leg.; 1 ♀, Sumiyo-son, Amami Is., Kagoshima Pref.,13-19. iii. 2001, K. Takahashi leg.; 1 ♂, Mt. Yuwan, Amami Is., Kagoshima Pref., 8. v. 1987, S.
Nomura leg.; 1 ♀, Materia fall, Amami Is., Kagoshima Pref., 8. v. 1987, S. Nomura leg.; 2 ♂1 ♀,Awa, Motobu Peninsula, Okonawa Is., Okinawa Pref., 13. iii. 1978, S. Naomi leg.; 1 ♂1 ♀, Oku,
Kunigami-son, Okinawa Is., Okinawa Pref., 14. iii. 1978, S. Nomura leg.
Distribution. Japan (Kyushu; Yaku Is., Tokara-Naka Is., Tokara-Takara Is., Amami Is., Okinawa Is.); Taiwan, China, India, Nepal, Oriental region.
Redescription. Male and female: Macropterous; body 5.0–6.0 mm (fore body 2.5–3.1 mm) in
length, matt or weakly shining, with antennae moderately long; paraglossae ovoidal (Fig.2aE, F).
Head and abdomen black; pronotum and elytra dark red (nearly black), each elytron with a yellowish-orange, almost round macula behind the middle, but sometimes indistinct (Fig. 136E) or
immaculate; labrum dark red; antennae and legs reddish brown. Head relatively short, with eyes
large, strongly prominent laterally; vertex deeply concave, with paired longitudinal grooves,median area between the grooves wide, moderately convex; punctures round, dense, small andalmost regular on head, but punctures very sparse and small on the median convex area. Pronotum with surface strongly uneven, median longitudinal depression indistinct in outline; punctures
very dense, strongly coarse. Elytra with surface uneven, punctures very dense, coarse. Legs long,thin; tarsi thin, 4th tarsomere distinctly bilobed but each lobe short. Abdomen subparallel-sided;
punctures sparse to moderately dense, small, and somewhat irregular throughout; 9th tergum(Fig. 125E, H) with posterolateral projections short; 10th tergum (Fig. 125E, H) weakly emargin-

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Fig. 125. Stenus gestroi Fauvel (Tokara-Naka Is., Kagoshima). A, endophallic basal tube; B, aedeagus; C, spermatheca; D, 9th ventrite of male; E, 9th and 10th terga of male; F, 7th to 8th ventrites of male; G, gonocoxite;
H, 9th and 10th terga of female. Scale 1: 0.1 mm for A, C, 0.2 mm for B, G; scale 2: 0.3 mm for F; scale 3: 0.2
mm for D, E, H.

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ate posteriorly. Lateroventrites very narrow, existing only at the bases of 3rd to 6th segments,
each lateroventrite gradually narrowed posteriorly.
Male: Seventh ventrite (Fig. 125F) posteromedially with a bell-shaped, ﬂat area, which isvery shallowly emarginate; 8th ventrite (Fig. 125F) posteromedially with a wide, moderately
deep emargination; 9th tergum (Fig. 125E) with apicolateral ﬂaps long, ventral apophyses moderately long; 9th ventrite (Fig. 125D) hardly serrate posteriorly, with stem trapezoidal in shape,
apicolateral teeth long, acutely pointed, apicolateral setae short, and macrosetae relatively long.
Aedeagal median lobe (Fig. 125B) elongate-ovoidal basally, almost parallel-sided and also furnished laterally with sparse, very short setae in posterior 1/2, with a long apicomedian projection
which is globose at the apicalmost part. Endophallic median longitudinal bands (Fig. 125B) withventral bands fused to form a wide, non-dotted band, dorsal bands thin; lateral longitudinal bands(Fig. 125B) very short; explusion hooks (Fig.125B) atrophied into a very small, arrow-headedsclerite; basal tube (Fig. 125B) with basal duct (room?) submembranous, ﬁnely, obliquely
striped, tube body composed of the proximal rod and distal spatulate plate which is pointed apically (Fig. 125A). Parameres (Fig. 125B) long, slender; stem mesially with 2 to 3 short setae;
apical area long, weakly swollen mesially, furnished mesially with 8 to 9 short to moderately
long setae.
Female: Eighth ventrite obtusely pointed posteromedially; gonocoxites (Fig. 125G) eachwith apicolateral tooth long, acutely pointed, apicolateral setae relatively short. Spermatheca(Fig. 125C) unique in having a guttalis-form (Fig. 7B) without striped RT-duct; distal duct
C-shaped, thick apically, and distinctly demarcated from proximal duct by the bent of acuteangle, where the opening of spermathecal gland is located; proximal duct thin (but relatively
thick basally), basically not coiled; basal pouch bell-shaped, sclerotized; spermathecal glandlarge, almost ovoidal in shape.
Biology and ecology. S. gestroi seems to be a relatively common Stenus species in Nansei
Isls.; and it is distributed in the plains and mountainous regions there. The beetles inhabit glass
litter heaped at the grasslands near natural forests; and they also inhabit leaf litter in natural forests.
Remarks. Stenus gestroi is closely allied to S. lacertosus Benick, 1917 from Indonesia andMalaysia, but this species is separable from the latter by the elytra more densely punctate and theendophallic expulsion hook arrow-headed (Puthz, 2011b: 568). In S. gestroi, the endophallic
basal tube has a basal duct which is ﬁnely, obliquely striped (Fig. 125A). When considering its
relative position in the basal tube, the striped basal tube in S. gestroi may be homologous withthe basal room of basal tube (Fig. 5).
Etymology. This species was named in honour of Dr. Raffaello Gestro, who is an eminententomologist in Italia.
Species group of S. guttalis Fauvel
S. guttalis group consists of 1 species in Japan; see Puthz (2011b) regarding a characterization of this group, and see also Puthz (2013) regarding a review of this group. Diagnostic characters are as follows: Similar in habitus to the species of S. gestroi group (Fig. 136F); head withvertex deeply concave; eyes very large; paraglossae oval; elytron with or without a yellowishorange spot; legs with 4th tarsomere strongly bilobed; metatibia of male with a preapical spur
(Puthz, 2011b); lateroventrites narrow, or both lateroventrites and tergoventrite sutures missing
on abdomen; aedeagal endophallus with a moderately large expulsion hook (Fig. 126H); sperma-

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317

theca composed of distal duct (C-shaped) and proximal duct (loosely coiled, more or less thin)(Fig. 126A).
Stenus guttalis Fauvel(Figs. 2aG, 126A–H, 136K–L)
Stenus guttalis Fauvel, 1895: 212; Herman, 2001: 2207; Naomi & Puthz, 2013: 140; Puthz,
2013: 1376.
Stenus guttalis ishigakiensis Naomi, 1988e: 39; Naomi & Puthz, 1994a: 218 (as synonym of S.
guttalis).
Type material examined. Lectotype: ♂ (IRSNB), type locality: Carin Cheba, Myanmar[examined and designated by Puthz in 1969: 21].
Other material examined. [NANSEI ISLS.]: 1 ♀, Fukuyama, Hirara City, Miyako Is., Okinawa Pref., 21. vii. 2012, T. Nakata leg.; 1 ♀, Ishigaki Is., Okinawa Pref., 15. iv. 1997, K. Takahashi leg.; 1 ♂, Sonai, Iriomote Is., Okinawa Pref., 8. iii. 1976, S. Morita leg.
Distribution. Japan (Nansei Is.: Miyako Is., Ishigaki Is., Iriomote Is.); Taiwan, China, Oriental region.
Redescription. Male and female: Macropterous; body 5.4–6.5 mm (fore body 2.5–2.9 mm) in
length, matt or weakly shining, with antennae long, thin; paraglossae ovoidal (Fig. 2aG). Body
dark red (nearly black) to black; elytra each with a yellowish-orange, round macula, but sometimes immaculate; labrum dark red; antennae and legs yellowish brown to reddish brown, knees
more or less infuscate. Head relatively short, with eyes large, strongly prominent laterally; vertex
deeply concave, with paired longitudinal grooves, median area between the grooves weakly convex; punctures round, dense small. Pronotum with surface strongly uneven, median longitudinal
depression indistinct in outline; punctures very dense, strongly coarse. Elytra with surface
uneven; punctures very dense, strongly coarse. Legs moderately long, thin; tarsi with 4th tarsomere deeply bilobed. Abdomen weakly narrowed posteriorly; punctures basically round to elliptical, moderately dense, small and distinct in anterior segments, while punctures in posterior segments elliptical, very small and regular. Both lateroventrites and tergoventrite sutures almost
missing on abdomen.
Male: Seventh ventrite (Fig. 126E) posteromedially with an elongate-bell-shaped, ﬂat area,
which is very shallowly emarginate; 8th ventrite (Fig. 126E) posteromedially with a wide, moderately deep emargination; 9th tergum (Fig. 126B) with anterolateral ﬂaps long, ventral apophyses pointed, and posterolateral projections long; 9th ventrite (Fig. 126G) elongate, ﬁnely serrate
posteriorly, with stem triangular, submembranous, apicolateral teeth short, pointed, apicolateral
setae short, and macrosetae long; 10th tergum (Fig. 126B) uniformly rounded posteriorly. Aedeagal median lobe (Fig. 126D) nearly violin-shaped, with apicomedian projection short, acutely
pointed, lateral rim very wide. Endophallic median longitudinal bands (Fig. 126D) with ventral
bands partially fused to form a non-dotted band, which is strongly sclerotized laterally, dorsal
bands diverging anteriorly; explusion hook (Fig. 126D, H) relatively large, with the owl-shaped,
posteromedian projection; basal tube (Fig. 126C, D) with basal room small, subglobose, tube
body baculiform, stout, gradually thickening apically. Parameres (Fig. 126D) long, slender,
weakly sinuous; apical area very long, moderately swollen mesially, and furnished with 12 to 13
setae of various length along the ventromesial margin.
Female: Eighth ventrite obtusely angulate posteromedially; gonocoxites (Fig. 126F) each

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Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

Fig. 126. Stenus guttalis Fauvel (A, F, Ishigaki Is., Okinawa; B–E, G, H, Sonai, Iriomote Is.). A, spermatheca;
B, 9th and 10th terga of male; C, endophallic basal tube; D, aedeagus; E, 7th to 8th ventrites of male; F, gonocoxite; G, 9th ventrite of male; H, expulsion hook. Scale 1: 0.1 mm for A, C, H; scale 2: 0.2 mm for B, D, G;
scale 3: 0.3 mm for E; scale 4: 0.2 mm for F.

The Steninae of Japan Part 1319with apicolateral tooth acutely pointed, apicolateral setae short. Spermatheca (Fig. 126A) with
C-shaped distal duct very large, with capsule long, rounded apically, and RT-duct rather thick;proximal duct very thin, very loosely, irregularly coiled; spermathecal gland large, nearly elongate-elliptical in shape, with its opening located just at the base of distal duct.
Biology and Ecology. No solid information is obtained about the habitats of this species inJapan, but one female beetle was collected by car-net trap in Ishigaki Is.
Remarks. Stenus guttalis is very similar to S. subguttalis Puthz, 1969 in external structure
and coloration, but this species is separable from the latter by the elytral macula smaller (Fig.
136L) when present, and the aedeagal median lobe almost violin-shaped, much wider apicolaterally, and with its lateral rim much wider (Fig. 126D).
Acknowledgements
We express our hearty thanks to the following entomologists and their institutions for loaning
us types or other specimens of Steninae which are needed for our monographic study: Giulio
Cuccodoro (Muséum dʼhistoire naturelle, Genève); Lubomir Hromádka (Praha); Toshiya Hirowatari (Kyushu University, Fukuoka); Satoshi Kamitani (Kyushu University, Fukuoka); Masahiro
Ohara (Hokkaido University Museum, Sapporo); Akiko Saito (Natural History Museum andInstitute, Chiba); Yasuaki Watanabe (Tokyo University of Agriculture, Atsugi); and Hiroyuki
Yoshitomi (Ehime University, Matsuyama). We sincerely thank Hiromu Kamezawa (Kawagoe,
Saitama) for taking all habitus photos of Steninae species, and Oliver Betz (University of Tübingen, Tübingen) for his taking several SEM-photos of Figure 2. We sincerely thank Ivan Löbl
(Muséum dʼhistoire naturelle, Genève) for his constructive comments on a near-ﬁnal version of
the manuscript of our monograph.
Our special thanks are due to cooperation in materal examined and also in taxonomic andecological informations of Steninae, given by the following entomologists: Koji Arai (Ranzan,
Saitama), Shiho Arai (Ranzan, Saitama), Kaoru Haga (Saitama C., Saitama), Yasuhiko Hayashi(Kawanishi, Hyogo), Katsuhiko Ito (Memuro, Hokkaido), Koichi Hosoda (Nirasaki Yamanashi),Tateo Ito (Yawata, Kyoto), Toshio Kishimoto (Museum of Natural and Environmental History,
Shizuoka), Isao Matoba (Yuasa, Wakayama), Munetoshi Maruyama (Kyushu University
Museum, Fukuoka), Kiminori Miyashita (Ebetsu, Hokkaido), Takasuke Miyata (Kochi C.,
Kochi), Masaaki Nishikawa (Ebina, Kanagawa), Sadahiro Ohmomo (Ami, Ibaraki), Iwao Okamoto (Kure, Hiroshima), Masahiro Saito (Mikuni, Fukui), Masahiro Sakai (Ehime University,
Matsuyama), Yasutoshi Shibata (Machida, Tokyo), Takashi Shimada (Shizuoka C., Shizuoka),
Keiichi Takahashi (Ushiku, Ibaraki), Yasushi Takai (Seki C., Gifu), Takaaki Takeda (Funabashi,
Chiba), Liang Tang (Shanghai Normal University, Shanghai), Nobuo Tsurusaki (Tottori University, Tottori), Takashi Watanabe (Fujisawa, Kanagawa), Osamu Yamaji (Okayama C., Okayama),
Hideyuki Yokozeki (Yokkaichi, Mie), Masataka Yoshida (Tokushima C., Tokushima).
Nomura gratefully acknowledges the support in part by KAKENHI (No. 24120002, Shûhei
Nomura (PI)) to the present work on Japanese Steninae. Naomi sincerely thanks Alexandr
Ryvkin (Moscow) for his sending me via e-mail a photo of the spermatheca of Stenus ﬁnalis andseveral photos of the aedeagus of S. weisei, and also for his identifying some Stenus species;
Kyoichiro Ueda (Kitakyushu Museum of Natural History and Human History) for his helping meby supplying some material for dissecting Stenus specimens; and Oliver Betz (University of
Tübingen, Tübingen), Dave J. Clarke (Field Museum of Natural History, Chicago), Fülöp Dávid(Szent Istvan University, Budapest), Konrad Dettner (University of Bayreuth, Bayreuth), Lars

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Koerner (Heidelberg), Richard Lyszkowski (National Museum of Scotland, Edinburgh), HongZhang Zhou (Chinese Academy of Sciences, Beijing) for their sending me PDF-papers on Steninae and its allied groups.
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Fig. 127. A, Dianous moritai Naomi (Sumiyo, Amami Is.); B, D. yoshidai Naomi (Kanpira, Iriomote Is.); C, D.
amamiensis Sawada (Naze, Amami Is.); D, D. japonicus Sawada (Kifune, Kyoto); E, D. shibatai Sawada(Ryogami, Saitama); F, Stenus comma LeConte (Piribetsu, Hokkaido); G, S. tenuipes Sharp (Yunotani,
Niigata); H, S. biguttatus (Linnaeus) (Hakken, Hokkaido); I, S. alienus Sharp (Takao, Tokyo); J, S. anthracinus Sharp (Okutama, Tokyo); K, S. kobensis Cameron (Renge, Niigata); L, S. macies Sharp (Ochiai,
Tokushima).

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Fig. 128. A, Stenus juno Paykull (Memanbetsu, Hokkaido); B, S. indagator Eppelsheim (Memanbetsu, Hokkaido); C, S. yamato Naomi (Irihirose, Niigata); D, S. lewisius Sharp (Kawasaki, Kanagawa); E, S. katoi
Naomi & Ito (Shibecha, Hokkaido); F, S. sauteri Bernhauer (Kitami, Hokkaido); G, S. nishikawai Naomi(Ohnuma, Hokkaido); H, S. amurensis Eppelsheim (Ebetsu, Hokkaido); I, S. distans Sharp (Hakui, Ishikawa);
J, S. disterminus Puthz (Kiyosumi, Chiba); K, S. calliceps Bernhauer (Tokara-Takara Is., Kagoshima); L, S.
formosanus Benick (Sonai, Yonaguni Is.).

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Fig. 129. A, Stenus clavicornis (Scopoli) (Kamishunbetsu, Hokkaido); B, S. takedai Naomi (Shonan, Chiba); C,
S. laborator Sharp (Shimousa, Chiba); D, S. japonicus Sharp (Kushiro, Hokkaido); E, S. mammops Casey(Daisetsu, Hokkaido); F, S. hammondi Puthz (Ebetsu, Hokkaido); G, S. expugnator Ryvkin (Kisarazu, Chiba);
H, S. giushin Naomi (Unzen, Nagasaki); I, S. zaishin Naomi (Tsurugi, Tokushima); J, S. kirin Naomi & Ito(Oku-koya); K, S. ohbayashii Naomi (Odami, Ehime); L, S. lanceolatus Naomi (Toyooka, Hyogo).

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Fig. 130. A, Stenus ochiba Naomi & Puthz (Nakatsuya, Hiroshima); B, S. satushin Naomi (Takatsuna, Ehime);
C, S. nipponomontanus Naomi (Kasuga, Nara); D, S. wasamatanus Puthz (Wasamata, Nara); E, S. corrugatus
Naomi & Shimada (Saigo, Oki Isls.); F, S. hagai Naomi (Irihirose, Niigata); G, S. curvaticellus Naomi (Ohno,
Fukui); H, S. intumescens Naomi, Nomura & Puthz sp. nov. (Ina, Nagano); I, S. displicatus Naomi, Nomura& Puthz sp. nov. (Ise, Mie); J, S. toukin Naomi & Puthz (Omonoki, Aichi); K, S. ubusuna Naomi & Ito(Daigo, Kyoto); L, S. kokie Naomi (Daihi, Kyoto).

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Fig. 131. A, Stenus serratimarginatus Naomi (Kiyosumi, Chiba); B, S. zimmermanni Puthz (Ryogami, Saitama);
C, S. yasutoshii Naomi (Akazawa, Yamanashi); D, S. houomontis Naomi & Ito (Houo, Yamanashi); E, S. sexualis Sharp (Shobara, Hiroshima); F, S. riukiuensis Puthz (Hatsuno, Amami Is.); G, S. ruralis Erichson (Ilek,
Kazakhstan); H, S. boops Ljungh (Tanno, Hokkaido); I, S. melanarius Stephens (Kisarazu, Chiba); J, S. raddei Ryvkin (Amur, Russia); K, S. shogun Puthz (Oze, Gunma); L, S. puberulus Sharp (Amagoi, Tokushima).

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Fig. 132. A, Stenus aboblitus Naomi & Nomura (Tazawa, Akita); B, S. nomurai Naomi (Kariba, Hokkaido); C,
S. varicosus Naomi, Nomura & Puthz sp. nov. (Onzui, Hyogo); D, S. mikado Hromádka (Suruga, Shizuoka);
E, S. pudefactus Ryvkin (Monbetsu, Hokkaido); F, S. miyama Naomi (Yuzawa, Niigata); G, S. immarginatus
Mäklin (Daisetsu, Hokkaido); H, S. tomitaorum Naomi (Kamishunbetsu, Hokkaido); I, S. hirtiventris Sharp(Tomiyachi, Aomori); J, S. pilosiventris Bernhauer (Matsuyama, Ehime); K, S. ﬁnalis Ryvkin (Shibetsu, Hokkaido); L, S. strobilus Ryvkin (Ebetsu, Hokkaido).

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Fig. 133. A, Stenus pubescens fraternus Casey (Abashiri, Hokkaido); B, S. aestivus Naomi (Kushiro, Hokkaido); C, S. bifoveolatus Gyllenhal (Shibetsu, Hokkaido); D, S. latitarsis Sharp (Kaneoya, Chiba); E, S.
depressus Puthz (Tadami, Fukushima); F, S. ancyleus Naomi, Nomura & Puthz sp. nov. (Asama, Nagano); G,
S. benefactor Ryvkin (Fujinomiya, Shizuoka); H, S. concinnus Sharp (Wajima, Ishikawa); I, S. oliverbetzi
Naomi, Nomura & Puthz sp. nov. (Sakura, Chiba); J, S. hirtellus Sharp (Tapah, Malaysia); K, S. oblitus Sharp(Yaita, Tochigi); L, S. piliferus Motschulsky (Sonai, Iriomote).

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Fig. 134. A, Stenus confertus Sharp (Zhuji, China); B, S. dissimilis Sharp (Sato, Mikura Is.); C, S. bohemicus
Machulka (Towadako, Aomori); D, S. aquilonalis Naomi & Puthz (Okukinu, Tochigi); E, S. mercator Sharp(Kushiro, Hokkaido); F, S. sedatus Sharp (Saitu, Aomori); G, S. weisei Bernhauer (Daijyu, Hokkaido); H, S.
cicindeloides (Schaller) (Wake, Okayama); I, S. kiesenwetteri Rosenhauer (Chitose, Hokkaido); J, S. velox
Sharp (Sanhoku, Kanagawa); K, S. hanami Hromádka (Ohuchi, Kochi); L, S. plagiocephalus Benick (Aira,
Iriomote Is.).

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Fig. 135. A, Stenus oshimaensis Naomi (Yona, Okinawa Is.); B, S. spurius Benick (Ohtomi, Iriomote); C, S. ﬂavidulus Sharp (Ketsuka, Saitama); D, S. ﬂavidulus paederinus Champion (Nakano, Iriomote Is.); E, S. currax
Sharp (Umaji, Kochi); F, S. veselovae Ryvkin (Yotei, Hokkaido); G, S. sibiricus Sahlberg (Kitayatsu,
Nagano); H, S. rugipennis Sharp (Tete, Toku Is.); I, S. bicolon Sharp (Yamakita, Kanagawa); J, S. coronatus
zipanguensis Puthz (Nishihotaka-guchi, Gifu); K, S. kamezawai Naomi, Nomura & Puthz sp. nov. (Kojin,Nara); L, S. mysticus Sharp (Nippara, Tokyo).

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Fig. 136. A, Stenus mystiformis Naomi, Nomura & Puthz sp. nov. (Odami, Ehime); B–D, S. sharpi Bernhauer &Schubert (B, Towada, Aomori; C, Daibosatsu, Yamanashi; D, Shimoda, Amakusa); E–J, S. gestroi Fauvel (E,Tokara-Naka Is., Kagoshima; F, Hatsuno, Amami Is.; G, Awa, Okinawa Is.; H, Piluchi, Taiwan; I, Nanshanchi, Taiwan; J, Lushan, Taiwan); K–L, S. guttalis Fauvel (K, Sonai, Iriomote Is.; L, Theun-Hinboun, Laos).