National Museum of Nature and Science Monographs No. 53
ISSN 1881-9109

THE SUBFAMILY STENINAE MACLEAY, 1825
(COLEOPTERA: STAPHYLINIDAE) OF JAPANPART 3. STENUS SATSUKI-GROUP AND
S. CEPHALOTES-GROUP

Shun-Ichiro NaomiShûhei Nomura
Volker Puthz

National Museum of Nature and Science Tokyo,
November 2022

National Museum of Nature and Science Monographs
No. 53

ISSN 1881-9109

National Museum of Nature and Science Monographs No. 53

THE SUBFAMILY STENINAE MACLEAY, 1825
(COLEOPTERA: STAPHYLINIDAE) OF JAPANPART 3. STENUS SATSUKI-GROUP AND
S. CEPHALOTES-GROUP
Shun-Ichiro NaomiShûhei Nomura
Volker Puthz

National Museum of Nature and Science
Tokyo, November 2022

Editorial Board
Tsuyoshi Hosoya, Editor-in-Chief, Department of Botany
Atsushi Ebihara, Managing Editor, Department of Botany
Toshihiko Fujita, Department of Zoology
Tatsuya Ide, Department of Zoology
Ritsuro Miyawaki, Department of Geology and Paleontology
Takanobu Tsuihiji, Department of Geology and Paleontology
Kazuhiro Sakaue, Department of Anthropology
Shigekazu Yoneda, Department of Science and Engineering
Takahiko Kutsuna, Department of Science and Engineering
Katsuhisa Sagisaka, Institute for Nature Study
Makoto Manabe, Collection Center

National Museum of Nature and Science
Ueno Park, Tokyo, 110–8718
Japan
Copyright ©2022
National Museum of Nature and Science, Tokyo
Published on 1 November, 2022
Printed by International Academic Publishing Co., Ltd., Tokyo
ISSN 1881-9109
ISBN 978-4-87803-049-9
Cover illustration：Stenus rufescens Sharp

		v

CONTENTS

Abstract......................................................................................................................................... 1
Introduction .................................................................................................................................. 1
Material of the Steninae treated ................................................................................................. 2
Characters used for the Taxonomy of Steninae......................................................................... 2
Descriptions and Drawings ......................................................................................................... 3
1. Methods of descriptions ........................................................................................................ 3
2. Methods of drawings............................................................................................................. 6
Taxonomy and Descriptions ........................................................................................................ 7
Genus Stenus Latreille, 1797 ..................................................................................................... 7
Species group of S. satsuki Naomi ......................................................................................... 7
Japanese fauna of the satsuki-group .................................................................................. 9A list of the Japanese species of the satsuki-group .......................................................... 10
The Satsuki-group ............................................................................................................ 10
Incertae sedis (S. friebi-complex) .................................................................................... 39
Species group of S. cephalotes Sharp .................................................................................. 53
Japanese fauna and species-units of the cephalotes-group .............................................. 56
A list of the Japanese species of the cephalotes-group .................................................... 57
The cephalotes-subgroup ................................................................................................. 59
Incertae sedis (S. daimio and its allied species) ............................................................ 131
The rufescens-subgroup ................................................................................................. 145
Incertae sedis (S. bifurcatus) ......................................................................................... 274
Additions of 8 species to the asyura-group ........................................................................... 275
Concluding Remarks ............................................................................................................... 293
Acknowledgements .................................................................................................................. 296
References ................................................................................................................................. 296
Corrigenda and Addenda to the Steninae of Japan Part 1 and Part 2 ............................... 299
Figures (habitus photos) .......................................................................................................... 300
Index .......................................................................................................................................... 306

The subfamily Steninae Macleay, 1825 (Coleoptera: Staphylinidae) of Japan
Part 3. Stenus satsuki-group and S. cephalotes-group
Shun-Ichiro Naomi1, Shûhei Nomura2 and Volker Puthz3
1

The Kyushu University Museum
Hakozaki 6–10–1, Higashi-ku, Fukuoka 812–8581, 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 ﬁnal, 3rd part of a monographic study of the subfamily Steninae Macleay,
1825 (Coleoptera: Staphylinidae) of Japan. It treats taxonomically the Japanese species of the 2
species groups of genus Stenus Latreille, 1797 (satsuki-group: 21 species; and cephalotes-group: 100
species), together with the addition of 8 species to the asyura-group (kasumi-subgroup). The
following 17 Stenus species are described from Japan as new to science: S. kannoi sp. nov.,
S. tsushimamontis sp. nov., S. ivanloebli sp. nov., S. kyotoensis sp. nov., S. sicyoideus sp. nov.,
S. cohaerens sp. nov., S. subulifer sp. nov., S. gloriﬁcus sp. nov., S. kochiensis sp. nov.,
S. takashiiellus sp. nov., S. fulvidus sp. nov, S. notomontis sp. nov., S. obtusus sp. nov.,
S. yoshidaiellus sp. nov., S. tateoitoi sp. nov., S. asiuensis sp. nov., S. sasajiiellus sp. nov. Six newsynonyms are as follows: S. nemoralis Naomi, 2015 is in synonymy with S. taoi Naomi, 1989a;
S. imadatei Naomi & Puthz, 1996 with S. kazami Naomi, 1988a; S. syugen Naomi, 1989a with
S. himiko Naomi, 1989a; S. olliformis owasenus Naomi, 2006 with S. olliformis Naomi, 2006;
S. ingens ryugatakensis Naomi, 2006 with S. ingens Naomi, 2006; S. ichihashii miunensis Naomi,
2006 with S. ichihashii Naomi, 2006. S. nakanei awajinis (Naomi), 1997b is upgraded to a species,
S. awajinis Naomi, 1997b stat. nov. The lectotype of S. cephalotes Sharp, 1889 is designated.
S. trispinosus Naomi & Nomura, 2015 is transferred from the asyura-group to the satsuki-group.
Keys to all the species of Stenus treated here except for S. bifurcatus and 8 species of asyura-groupare given, together with detailed drawings of the taxonomically important structures of all species,
and also with habitus photos of the Japanese 67 species and the non-Japanese (Palaearctic or
Oriental) 5 species. In addition, a probable endophallic copulatory tube gland is discovered from themale of S. rufescens Sharp and it is described and drawn (Fig. 82G, H).

Introduction
This is the ﬁnal, 3rd part of our monographic studies, in which we aim at clarifying theJapanese fauna of the subfamily Steninae Macleay, 1825 of Staphylinidae (Coleoptera). In the
3rd part (Puthz: Contribution No. 375 on Steninae; Naomi: Contribution No. 62 on Steninae), theJapanese species of 2 species groups of Stenus, namely, the satsuki-group (21 species) and the
cephalotes-group (100 species: cephalotes-subgr. 40 species and rufescens-subgr. 60 species) aretreated taxonomically, together with the addition of 8 species to the asyura-group (kasumi-subgroup). The 17 new species (1 new species of satsuki-group; 9 new species of cephalotes-subgr.;

2

Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

and 7 new species of rufescens-subgr.) are described, and the necessary taxonomic treatments are
given, including synonymizations, a new combination and a lectotype designation. S. trispinosus
Naomi & Nomura, 2015 is transferred from the asyura-group to the satsuki-group. Keys to all
the species except for S. bifurcatus and 8 species of asyura-group are provided. The taxonomically important structures are drawn in detail for all the Stenus species treated in the Part 3, andthe habitus photos are also given for the Japanese 67 species and the non-Japanese (Palaearctic
or Oriental) 5 species. In addition, a probable endophallic copulatory tube gland of S. rufescens
Sharp (male) is also described and drawn (Fig. 82G, H).
Material of the Steninae treated
The holotypes of all the Stenus-species described in the Part 3 are examined by Naomi and/or Puthz. Depositories of the holotype specimens are as follows:
Institutions
AACO: Agriculture and Agrifood Canada, Ottawa
CBM: Natural History Museum and Institute, Chiba
EUMM: Ehime University Museum, Matsuyama
FMC: Field Museum of Natural History, Chicago
KUF: Kyushu University, Fukuoka
KUMF: Kyushu University Museum, Fukuoka
NHML: Natural History Museum, London
NHMG: Natural History Museum, Geneva
NHMV: Natural History Museum, Vienna
NMNST: National Museum of Nature and Science, Tsukuba
NMP: National Museum of Prague — Natural History Museum
OMNHO: Osaka Museum of Natural History, Osaka
SMNHS: State Museum of Natural History, Stuttgart
TUAA: Tokyo University of Agriculture, Atsugi
Private collections
cH: Collection of Yasuhiko Hayashi, HyogocI: Collection of Tateo Ito, Kyoto
cP: Collection of Volker Puthz, Schlitz
When the depositories of specimens (including paratypes) examined are not mentioned in thedescriptions of species, they all are deposited in the Kyushu University Museum, Fukuoka(KUMF).
Characters used for the Taxonomy of Steninae
The characters used in the Part 3 are basically the same as in the Part 1 and Part 2. See
Naomi et al. (2017, p. 5–20 and 2019, p. 2–3) regarding the characters used for the taxonomy ofSteninae in the Part 1 and Part 2, respectively. Two more characters are discussed here for moreeasily understanding the species groups of Stenus treated in the Part 3.

The Steninae of Japan Part 3

3

Head concavity
In the satsuki-group and cephalotes-group, the basic structure of head, namely, a pair of moreor less longitudinal furrows (or depressions) on the interocular area and the median longitudinalswollen area between the furrows are the same as in the other species groups of Stenus. We
observed that 3 diﬀerent forms are found on how the furrows run on the interocular area of head.
The running course of furrows are longitudinal-oblique (e.g., S. kazami, S. oblongulus), longitudinal (e.g., some specimens of S. testaceopiceus, S. asiuensis) and mesially-curved (e.g., S. intermixtus, S. cinanomontis).
Spermatheca of female
In the 4 species of satsuki-group (S. hime, Fig. 6I; S. intermixtus, Fig. 7C; S. kannoi, Fig. 8E;
and S. volkerputhzi, Fig. 9F), a peculiar form of spermatheca is developed. Namely, the capsuleis spherical or elongate-subovoidal in shape. The spermathecal duct is very short in that it is no
more than 2.3 times the diameter of capsule, and it is more or less swollen at its distal portion.
The capsule is connected with the sphermathecal duct by a more or less thin, very short duct inthe satsuki-group. The spermatheca of similar form is found also in the indubius-group(S. tanuki, S. ohishii; Naomi et al., 2019). in the indubius-group the capsule is connected with theapical (swollen) chamber of spermathecal duct by a thin duct called collum.
When considering the above-mentioned structural similarity of spermatheca observed in thesatsuki-group and the indubius-group, the more or less swollen distal portion of duct in the satsuki-group seems to be homologous with the apical chamber of duct in the indubius-group, while
the connecting duct in the former group is homologous with the collum in the latter group (seealso Naomi, 2006, p. 8–11). Furthermore, the basal valve of duct is not formed in the satsukigroup, as in the indubius-group. The peculiar form of spermatheca found in the 4 species ofsatsuki-group is, thus, considered a peculiar subform of the indubius-form of spermatheca.
Descriptions and Drawings
Aiming at the concise descriptions of Stenus-species treated in the Part 3, the descriptions
and drawings are slightly modiﬁed from those in the Part 1 and Part 2, regarding several points
which are here taken up and discussed below. See Naomi et al. (2017, p. 20–21 and 2019, p. 3–5)
regarding the methods of descriptions and drawings in the Part 1 and Part 2, respectively.
First, we take up and discuss the revised methods of making the ʻKeys to speciesʼ and ʻSpecimens examinedʼ in the descriptive parts of Part 3. Second, we discuss the revised methods ofdescribing the punctures on the surface of body and the abdominal modiﬁcations of male,because they are slightly diﬀerent from the methods adopted in the Parts 1 and 2. Third, we add
various annotations on several taxonomic characters for more easily understanding the descriptions of Stenus-species treated in the Part 3.
1. Methods of descriptions(1). Revised methods of describing the species of Stenus
Keys to species
As far as the satsuki-group and the so-called “friebi-complex” (which is placed as incertae
sedis in the satsuki-group) are concerned, a key is made for the species of the group or the com-4

Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

plex because each comprises a small number of species.
The cephalotes-subgr. and rufescens-subgr. of the cephalotes-group are large species subgroups. Thus, we are to make a lengthy key to the species of such species subgroup. However, alengthy key to the large number of species is diﬃcult to make, because the useful characters foradequately making a key to species are highly limited to the internal characters obtained from theaedeagus and endophallic structures in addition to a few other external characters from theabdominal modiﬁcations of male, colors of body, etc. owing to the high similarity of external
structures of body among the species of each subgroup. Such lengthy keys seem to be thus diﬃcult for users to use for species identiﬁcation. Therefore, as far as the cephalotes-subgr. and rufescens-subgr. are concerned, a key is made for each unit of species that is found out from thecephalotes-subgr. or rufescens-subgr. during the course of our present study. (See introductory
part of the cephalotes-group, p. 53 regarding the matter with units of species.)
Specimens examined
When the available beetle specimens of a Stenus-species treated here are small or moderate
in number, they all are enumerated in the ʻSpecimens examinedʼ. However, when they are large
or much larger in number than we need to grasp the distributional range of the Stenus-species
concerned, some extra-specimens are not enumerated in the ʻSpecimens examinedʼ. For example,
when much larger number of Stenus-beetles of a same species are collected from the same locality on the same day, only 3 specimens are enumerated. When the Stenus-beetles of a same species are collected many times from the same locality on the diﬀerent days, only one collecting
sample of Stenus-beetles is enumerated.
(2). Revised methods of describing the taxonomic characters of Stenus
Punctures
There are various ways for describing the punctures on the surface of body in Stenus. In thepresent paper, ﬁrst, the common shapes and average sizes of punctures on the surface of body ofeach Stenus-species are described. The density of punctures are not described owing to an
amount of supposed larger variations than on the shapes and sizes of punctures. The large and thecoarse or subrugose punctures, whose conditions are sometimes useful for the species identiﬁcation of Stenus, are very often found on the pronotum and elytra. Second, these conditions ofpunctures are thus also described in the species where they are found on the pronotum and elytra.
An example on the description of punctures is as follows: Body with punctures round to ovoidal
or elliptical, small to moderately large, and also pronotum partially with coarse punctures andelytra partially with large, coarse to subrugose punctures.
Abdominal modiﬁcations of male
The abdominal ventrites of male are diversely modiﬁed with the ﬂat areas, various size anddepth of depressions, elevation of the lateral sides of a depression, various size and shape ofemarginations, presence of the dense and/or long setae, and also posteroventral protrusion ofwhole abdominal ventrite. A depression is commonly found on the posteromedian part of each of
6th and 7th ventrites. All the 3rd to 8th ventrites are sometimes modiﬁed with ﬂat areas and various depth of depressions, together with other kinds of modiﬁcations (e.g., emarginations). The
anteromedian as well as posteromedian depressions are often developed on the 7th ventrite when
the depression is well-developed (e.g., very deep and large).

The Steninae of Japan Part 3

5

The morphologically modiﬁed ventrites (especially 6th to 8th ventrites) of male are drawn indetail for most of the Stenus-species treated in the Part 3. Thus, descriptions of the abdominal
modiﬁcations of male are restricted to the ﬂat area(s) and depression(s) on the posteromedianparts of ventrites on which they are found, and the emargination at the posteromedian part of 8th
ventrite. When a ﬂat area or a depression is located on the posteromedian part of a ventrite, it issimply described as ʻﬂat areaʼ or ʻdepressionʼ without adding the term ʻposteromedianʼ. On theother hand, when a conspicuous anteromedian depression is developed, together with a posteromedian depression on the 6th and 7th, or on the 7th ventrite, both of them are when necessary
described in terms of ʻanteromedian depressionʼ and ʻposteromedian depressionʼ. An example on
the description of abdominal modiﬁcations of male is as follows: Abdomen modiﬁed with a ﬂatarea on the 5th, a shallow depression on the 6th, a moderately deep anteromedian and a deep
posteromedian depression on the 7th, and an arcuate, shallow emargination on the 8th ventrite.
These descriptions seem to be essential because they all are often clues for identifying the
Stenus-species, especially in cases of the closely allied species where the morphological diﬀerences on the aedeagal median lobe and endophallic components are relatively small. Descriptions of other various kinds of abdominal modiﬁcations of male are omitted in the Part 3. For
knowing how these various modiﬁcations (emarginations, setae, etc.) are actually developed on
the ventrites of male, together with the posteromedian ﬂat areas and depressions, see a series ofﬁgures annexed to the descriptions of Stenus-species treated in the Part 3.
(3). Annotations for describing the taxonomic characters of Stenus
Color
The color of body parts (head, pronotum, elytra and abdomen) and appendages (labrum,
antennae and legs) are described as in the Part 1 and Part 2. However, descriptions of the color ofseveral parts of body and appendages are omitted. The anterior margin of labrum is usually subtransparent and paler in color, and thus its color is not described. Instead, the color of the basal
part of labrum is described as the color of labrum. The apical segments of antennae, the “knees”(namely, distal parts of femora and proximal parts of tibiae) of legs, and the apical segments ofabdomen are very often infuscate (or darker in color). Such infuscations as above are usually notimportant for describing the color of body, nor show remarkable uniqueness for many of the Stenus-species treated here. Thus, these infuscations are not described. The color of abdomen gradates from the base (paler) to apex (darker) in some Stenus-species. Such gradation of color on
the abdomen also is not described except for the cases where it is distinct. The range of colors
that show such color gradation is to be adequately described by commonly describing the rangeof the color of abdomen (e.g., reddish brown to dark brown or almost black).
Ninth tergum of male
The anteroventral extension of the anterior margin of 9th tergum of male in Stenus was once
called “antecostal apophysis” in the Part 2 (Naomi et al., 2019, p. 4). It is here called ventral
apophysis, as in the Part 1 (Naomi et al., 2017, p.10), until it is clariﬁed what the anterior marginof 9th tergum with its anteroventral extension is from the morphological point of view.
SpermathecaIn the spermatheca of Stenus, the subapical part of duct, on which the transverse stripes
densely run, was called “rattlesnakeʼs tail-like duct” (abbreviated as “RT-duct”) in Naomi (2006a,

6

Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

p. 52). Here, it is called striped duct, because such term reﬂects the actual condition of duct for
more adequately describing the spermatheca in Stenus. The most proximal part of spermathecal
duct was called “basal sclerotized duct” in Naomi (e.g., 2006, p. 9). It is certainly strongly sclerotized in the most species of Stenus examined. However, in some cases it is submembranous (e.g.,
S. okiensis), only moderately sclerotized (e.g., S. tsurusakii) or partially sclerotized (e.g., S. satsuki, S. fulvidus). Thus, it is better to call it basal duct in the descriptive studies.
The matter with the drawing and description of spermathecal gland is also here mentioned.
The spermathecal gland is drawn as it is and is also described so, when the original shape of agland can be observed under the microscope. The spermathecal gland sometimes shrinks (e.g.,
Fig. 88C) after it was boiled in the KOH solution. Thus, it is drawn but not described when the
deformed condition of gland only was observed.
Abdominal muscles
In some cases, the running courses of few muscles of postabdomen (e.g., Fig. 3A) andaedeagus (e.g., Figs. 3C, 51F) can be almost completely or partially observed during the courseof our study. They are carefully drawn in cases where their drawings will be considered to be
useful for understanding the running courses of those muscles, but they are not described in thedescriptions of species.
2. Methods of drawings
Adopting in the Part 3 the same methods of drawing the structures as taxonomically important characters as in the Part 1 and Part 2, we add here only a few remarks as to how to use thedotted lines (……) and the arrows (→) in the drawings.
The dotted line is used for drawing the outline of a lost part of a structure as taxonomic character (Fig. 56B) only when the outline of the lost part in question can be traced by observing theunbroken opposite side of the structure, or by observing the same structure (unbroken) of anotherspecimen examined.
Among the structures as taxonomic characters which we draw for species identiﬁcation, there
are several structures with simple, uniform arrangement of very small dots, very small tubercles,
or very thin transverse stripes. They are well-exempliﬁed by the ventromedian bands of endophallus which are uniformly covered with very small, round dots. For saving the times, for example, the dots on the surface of ventromedian band are drawn only for those along the posterior
margin of folded ventromedian band. To show that the non-dotted area of ventromedian band in
the drawing is equally dotted as in the dotted area, an arrow is depicted on the non-dotted area
(Fig. 3A). Here, the depiction of the arrow means that the non-dotted area indicated by the direction of arrow is modiﬁed with the same kind of dots as in the dotted area. The same is also trueof the use of an arrow in cases of the structures with simple, uniform arrangement of very small
tubercles (e.g., Figs. 50A, 54E) or of very thin transverse stripes (e.g., Fig. 118C).

7

Taxonomy and Descriptions
Subfamily Steninae MacLeay, 1825
Genus Stenus Latreille, 1797
Species group of S. satsuki Naomi
It was noticed during the course of present study that the 15 Stenus-species (listed below)
have several similarities to the 2 European species: S. pallipes Gravenhorst, 1802 (Fig. 1A) andS. kolbei Gerhardt, 1893 (Fig. 1B–H), although the diverse conditions of abdomen can beobserved among these Japanese species. Five species have very thin lateroventrites in the 4th to
6th segments (Hemistenus-type); 4 species have only tergoventrite sutures there (Hemistenustype); and 6 species have no lateroventrites nor tergoventrite sutures there (Hypostenus-type).
(See description of S. nemorosus regarding the reclassiﬁcation of S. trispinosus from the asyuragroup to the satsuki-group., p. 31)
Three morphological similarities between the 2 European species and some or most of these15 Japanese species are found, which probably suggest their phylogenetic kinship. First of all,some of the Japanese species is very similar in habitus to the European species. Especially, thehabitus of S. okayamaensis (Fig. 130D), S. satsuki (Fig. 130E), etc. is very similar to that of S.
kolbei (Fig. 130B). In addition, these species share the similar subcylindrical form of abdomen
due to the nearly embedded position of lateroventrites into the abdominal wall. Second, the bodyof the European and also Japanese species is dark or black in color. Namely, the body is black in
the European species (Fig. 130A, B), while it is dark to black in color in all the 15 Japanese (Fig.
130C–L) species. Third, the aedeagal median lobe of the European (e.g., Fig. 1A) and also Japanese (e.g., Fig. 3A) species is moderately broad to broad and even so at the apicolateral corners
except for the 2 Japanese species, S. hotei (Fig. 2B) and S. gracilior. (Fig. 15B).
Furthermore, the peculiar conditions of characters obtained from the aedeagus and endophallus are found in 1 or 2 of the European (abbreviated as ʻEʼ) species and also in some Japanese(abbreviated as ʻJʼ) species, although the conditions are slightly diﬀerent from one species toanother in each of the characters mentioned below. First, the apical sclerotized area of aedeagal
median lobe is narrow, and about 2/5 to 3/5 times as broad as the breadth of median lobe at theapicolateral corners: S. pallipes (E) — S. kajika and S. okayamaensis (J). Second, the small,almost pointed or pointed apicomedian cusp of aedeagal median lobe is developed: S. kolbei (E)— S. nemorosus, S. fujimontis and S. fujiensis (J). Third, the basal (thick) and apical (thin) tubes
are distinctly recognizable from each other by the diﬀerent thickness so that the copulatory tube
forms a unique shape: S. kolbei (E) — S. taoi, S. fujimontis and S. gracilior (J). Fourth, the copulatory tube is more or less bifurcated at the apex: S. pallipes (E) — S. kajika and S. kannoi (J).
Fifth, the hump or hump-like protrusion is developed at the mesial side of endophallic expulsion
hook: S. kolbei (E) — S. hime (J). Sixth, the apical area of aedeagal paramere is short to very
short: S. pallipes and S. kolbei (E) — S. taoi, S. nemorosus, S. trispinosus, S. fujimontis and S.
fujiensis (J). The occurrences of these unique apomorphic conditions seem to, though restrictedly
found as described above, also add some evidences to show their phylogenetic kinship.
These morphological similarities in total seem to certainly show the phylogenetically closed
relationship of the 15 Japanese species to the 2 European species (S. pallipes and S. kolbei).
However, ﬁrst, no distinct synapomorphies can be observed that are shared by all or almost allthese 17 species, and second, these 17 species, when wholly putting together, show a clear dis-8

Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

Fig. 1. A, Stenus pallipes Gravenhorst & B–H, S. kolbei Gerhardt (East Europe). A, B, aedeagus; C, 9th ventriteof male; D, spermatheca; E, 9th and 10th terga of male; F, copulatory tube, G, posterior part of 8th ventrite ofmale; H, posterior part of gonocoxite. Scale 1: 0.1 mm for A; scale 2: 0.2 mm for B, C, E, G; 0.1 mm for D, F,
H.

The Steninae of Japan Part 3

9junct distribution within the Palaearctic Region. Therefore, until their phylogenetic relationshipis clariﬁed, we here newly but tentatively classify the 15 Japanese species in the species group of
S. satsuki, but not in the “pallipes-group” which was established by Benick (1925) and restudied
by Benick (1938). This is because the “pallipes-group” is considered a mixed group, in which asmall number of species of several species groups of Stenus are included (Benick, 1925, 1938).
The satsuki-group seems to be allied to the cephalotes-group (with the Hypostenus-type abdomen), but it is, though only partially, separable from the latter species group by the Hemistenustype abdomen, the particular form of habitus (Fig. 130C–L), etc.
Diagnostic characters of the satsuki-group. Male and female: Legs each with 4th tarsomere strongly bilobed; abdomen marginated by thin to very thin lateroventrites or tergoventrite
sutures (Hemistenus-type), or not marginated (Hypostenus-type). Male: Abdominal ventrites
slightly to moderately modiﬁed with ﬂat areas, shallow depressions, emarginations, etc. (Figs.
3D, E, 10E); 9th ventrite with a pair of more or less pointed apicolateral teeth (Fig. 5B); aedeagal
median lobe usually moderately broad to broad and even so at apicolateral corners (Figs. 1B,
5C), sometimes with an almost pointed or pointed apicomedian cusp (Figs. 1B, 14F). Female:
Gonocoxites each with a pointed apicolateral tooth (Fig. 5F); spermatheca showing commonform in most species (Figs. 1D, 14A) or indubius-form in the 4 Japanese species (Fig. 6I).
S. friebi-complex
The friebi-complex was ﬁrst established in Naomi & Puthz (1996), in which it was brieﬂycharacterized as “small reddish species with distinct paratergites”. The species of friebi-complex
have been several times included in the cephalotes-group (Puthz, 2012, 2013; Naomi & Puthz,
2013, etc.) because they are more or less similar in the external and internal structures of body tothe species of cephalotes-group.
However, it was also noticed during the course of present study that the friebi-complex isvery similar in several points to the satsuki-group newly established above. First, all the speciesof friebi-complex (Fig. 131A–I) are very similar in the general structure of body and habitus tosome species of the satsuki-group with abdominal ventrites (Fig. 130A–E). Additionally, somespecies of friebi-complex are similar or very similar to some species of satsuki-group regarding
the shape of aedeagal median lobe and/or some components of its endophallus. For example, S.
silvaticulus (friebi-complex; Fig. 18D) is very similar in the shape of aedeagal median lobe to S.
hotei (satsuki-group; Fig. 2B). Therefore, until the taxonomic problem as to whether the speciesof friebi-complex belong to the cephalotes-group or the satsuki-group, is ﬁrmly settled, the species of friebi-complex are tentatively classiﬁed in the satsuki-group (as insertae sedis).
Japanese fauna of the satsuki-group
At present, the satsuki-group consists of 21 species from Japan, including the 6 species thatare here classiﬁed in the incertae sedis. They are distributed in Honshu (norther Tohoku-District
to western Chugoku-District), Shikoku and Nansei Islands, but not in Kyushu. They all are brachypterous species, and each is indigenous to the Japanese Archipelago. Recently, many species
are also newly described and thus distributed also from Taiwan (Puthz, 2012, etc.). S. hagoromo
from Nansei Isls., Japan is closely allied to a Taiwanese species, S. perspicabilis Puthz, 2012.

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Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

A list of the Japanese species of the satsuki-grouphotei Naomi, 1998a Distribution: Japan (Shikoku).
kajika Naomi & Puthz, 1994 Distribution: Japan (Honshu).
okayamaensis Naomi, 2021 Distribution: Japan (Honshu).
satsuki Naomi, 1987 Distribution: Japan (Shikoku).
hime Naomi & Puthz, 1994 Distribution: Japan (Honshu).
intermixtus Puthz, 1993 Distribution: Japan (Honshu).
kannoi Naomi, Nomura & Puthz sp. nov. Distribution: Japan (Honshu).
volkerputhzi Naomi, Nomura & Kamezawa, 2015 Distribution: Japan (Honshu, Shikoku).
uneme Naomi, 1989a Distribution: Japan (Honshu).
taoi Naomi 1989a Distribution: Japan (Honshu).
＝nemoralis Naomi syn. nov.
nemorosus Naomi & Y. Watanabe, 2015 Distribution: Japan (Honshu).
trispinosus Naomi & Nomura, 20151) Distribution: Japan (Honshu).
fujimontis Puthz, 2001 Distribution: Japan (Honshu).
fujiensis Puthz, 2001 Distribution: Japan (Honshu).
gracilior Naomi, 2015 Distribution: Japan (Honshu).
Note. 1). This species was ﬁrst classiﬁed into the asyura-group (Naomi et al., 2019, p. 24).
Incertae sedis (S. friebi-complex)
etsukoae Naomi, 1987 Distribution: Japan (Hokkaido).
kazami Naomi, 1988 Distribution: Japan (Honshu).
＝imadatei Naomi & Puthz, 1996 syn. nov.
silvaticulus Naomi, 1997 Distribution: Japan (Honshu).
koinobori Hromádka, 1980 Distribution: Japan (Hokkaido).
puthziellus Naomi, 1997 Distribution: Japan (Honshu).
hagoromo Naomi, 1988 Distribution: Japan (Nansei Isls.).

The satsuki-group
Key to the Japanese species of the satsuki-group1(10) Male and female: Abdomen having lateroventrites in the 4th to 6th segments.
2(9) Male: Endophallic expulsion hook laterally without a hump in the middle. Female: Spermatheca showing the basic form.
3(4) Male: Aedeagal median lobe distinctly narrower at apicolateral corners (Fig. 2B) .............
....................................................................................................................... S. hotei Naomi
4(3) Male: Aedeagal median lobe distinctly broader at apicolateral corners.
5(6) Male: Aedeagus with apical sclerotized area well-developed, with median part strongly
protruding posteriorly (Fig. 3A); copulatory tube more or less robust, short (Fig. 3A) .......
....................................................................................................... S. kajika Naomi & Puthz
6(5) Male: Aedeagus with apical sclerotized area hardly or less developed; copulatory tube
comprising a thin ﬂagellum.
7(8) Male: Aedeagal median lobe with apical sclerotized area developed and rounded at apico-

The Steninae of Japan Part 3

11

median part (Fig. 4A); paramere simply pointed at apex (Fig. 4A) .....................................
.........................................................................................................S. okayamaensis Naomi
8(7) Male: Aedeagal median lobe with apical sclerotized area hardly developed (Fig. 5C);
paramere subulate at apex (Fig. 5C) .......................................................... S. satsuki Naomi
9(2) Male: Endophallic expulsion hook laterally with a hump in the middle (Fig. 6F). Female:
Spermatheca showing the indubius-form (Fig. 6I) ........................ S. hime Naomi & Putnz
10(1) Male and female: Abdomen lacking lateroventrites in the 4th to 6th segments.
11(18) Male and female: Abdomen having tergoventrite sutures in the 4th to 6th segments.
12(17) Male: Aedeagal median lobe broadest at apicolateral corners and obtuse at apex; endophallic expulsion hooks well-developed.
13(16) Male: Paramere without setae at the most apical part. Female: Spermatheca showing theindubius-form.
14(15) Male: Aedeagal median lobe with apical sclerotized area very shallowly emarginate atposterolateral margin (Fig. 7A); copulatory tube with ventrally- turned process thicker
and moderately curved (Fig. 7E) .......................................................... S. intermixtus Puthz
15(14) Male: Aedeagal median lobe with apical sclerotized area very weakly rounded at posterolateral margin (Fig. 8G); copulatory tube with ventrally-turned process thinner andstrongly curved (Fig. 8D).................................S. kannoi Naomi, Nomura & Puthz sp. nov.
16(13) Male: Paramere with setae only at the most apical part (Fig. 10C). Female: Spermatheca
showing the basic form (Fig. 10A, B) ........................................................S. uneme Naomi
17(12) Male: Aedeagal median lobe broadest before the middle and well-rounded apically apex
(Fig. 9A); endophallic expulsion hooks atrophied (Fig. 9G) ................................................
.................................................................... S. volkerputhzi Naomi, Nomura & Kamezawa
18(11) Male and female: Abdomen lacking tergoventrite sutures in the 4th to 6th segments.
19(28) Male: Aedeagal median lobe broader, and narrowly rounded or obtusely angulate at apicolateral corners; paramere with apical area much shorter than the breadth of median lobe
at apicolateral corners.
20(21) Male: Aedeagal median lobe tricuspidate at the apicomedian part (Naomi et al., 2019,
Part 2, p. 25, Fig. 7D)...........................................................................S. trispinosus Naomi
21(20) Male: Aedeagal median lobe obtusely pointed at apex or pointed with an apicomediancusp.
22(23) Male: Aedeagal median lobe obtusely pointed at apex (Fig. 11H) ................. S. taoi Naomi
23(22) Male: Aedeagal median lobe pointed with apicomedian cusp.
24(27) Male: Aedeagal median lobe with apical sclerotized area hardly developed; endophallic
expulsion hook with anterior plate partially fused with posterior plate.
25(26) Male: Copulatory tube with basal tube demarcated by a weak constriction from apicaltube (Fig. 12C); endophallic expulsion hook a little broader, with anterior plate minutely
hooked at anterior tip (Fig. 12G) ............................... S. nemorosus Naomi & Y. Watanabe
26(25) Male: Copulatory tube with basal tube distinctly demarcated by the thickness from apicaltube (Fig. 13D); endophallic expulsion hook a little narrower, with anterior plate almost
rounded at anterior tip (Fig. 13F).......................................................... ..S. fujimontis Puthz
27(24) Male: Aedeagal median lobe with apical sclerotized area developed and broad- subtriangular (Fig. 14F); endophallic expulsion hook with anterior plate demarcated by a suturefrom posterior plate (Fig. 14E) ..................................................................S. fujiensis Puthz
28(19) Male: Aedeagal median lobe narrower, and widely, moderately rounded at apicolateralcorner (Fig. 15B); paramere with apical area a little longer than the breadth of median12

Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

lobe at apicolateral corners (Fig. 15B) .................................................... S. gracilior Naomi
Stenus hotei Naomi(Fig. 2A–F)
Stenus hotei Naomi, 1998a: 391; Herman, 2001: 2217; Naomi & Puthz, 2013: 144.
Type material examined. Holotype: ♂ (CBM), Mt. Ikenoko, Kitô-son, Naka, Tokushima
Pref., 18. viii. 1980, M. Yoshida leg.
Distribution. Japan: Shikoku (Tokushima Pref.).
Redescription. Male: Body 3.7 mm (fore body 1.9 mm) in length. Body moderately shining;head, elytra and abdomen black; pronotum dark red near black; labrum dark reddish brown;
antennae and legs yellowish brown to reddish brown. Body with punctures small to moderately
large, round to ovoidal or elliptical, and also pronotum and elytra partially with coarse to subrugose punctures. Head moderately concave, with a pair of mesially-curved furrows; antennae
moderately long, thin; pronotum with surface uneven, with a median longitudinal furrow very
indistinct; abdomen subcylindrical, slightly thick, subparallel-sided; lateroventrites each very
thin, ﬁnely punctate, tergoventrite sutures distinct.
Abdomen (Fig. 2D) modiﬁed with an arcuate emargination on the 8th ventrite; 9th tergum(Fig. 2A) with ventral apophyses moderately long, thin; 9th ventrite (Fig. 2C) with macrosetae
long, apicolateral teeth small, acute, apicolateral setae moderately long; 10th tergum (Fig. 2A)
entire. Aedeagus (Fig. 2B) with median lobe moderately elongate, gradually narrowing in theapical 1/2 toward the rounded apex with a triangular transparent plate at the apicomedian part;
apical sclerotized area short. Endophallus (Fig. 2B) with copulatory tube having main tube ﬂagellar, moderately long; dorsolateral bands thin; expulsion hooks (Fig. 2E) developed, moderately large, almost X-shaped, fused behind the middle; ventromedian bands moderately long,moderately broad. Parameres (Fig. 2B) long, each slightly sinuous, very acutely pointed at apex;
apical area very long, mesially with 8 to 9 setae along dorsal and ventral margins.
Female: Unknown.
Biology and ecology. S. hotei is a rare species. The beetle of this species inhabits leaf litter in
the natural forest of a mountainous region.
Remarks. S. hotei is characterized in having such primitive conditions widely found in the
Stenus species as the abdomen margined with thin lateroventrites, the aedeagus simply narrowing
apicad, and the endophallus having the developed expulsion hooks (Fig. 2E), suggesting that thisspecies is probably most primitive in the Japanese species of satsuki-group. At present, no species seems to be closely related to S. hotei, which makes this species distinct among the speciesof this group. It is thus easily separable from the other species of this species group by theaedeagus simply narrowing apicad (Fig. 2B) and the endophallic expulsion hooks developed(Fig. 2E).
Etymology. The speciﬁc epithet of this species is derived from the name of one of the Seven
Gods of Good Fortune, Hotei.
Stenus kajika Naomi & Puthz(Figs. 3A–E, 130C)
Stenus kajika Naomi & Puthz, 1994: 261; Herman, 2001: 2243; Naomi & Puthz, 2013: 144.

The Steninae of Japan Part 3

Fig. 2. Stenus hotei Naomi (Tokushima: Mt. Ikenoko). A, 9th and 10th terga of male; B, aedeagus; C, 9th ventriteof male; D, 8th ventrite of male; E, endophallic expulsion hooks; F, 5th abdominal segment (right dorsolateralview). Scale 1: 0.2 mm for A–C; scale 2: 0.2 mm for D, F; scale 3: 0.05 mm for E.

13

14

Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

Fig. 3. Stenus kajika Naomi (Nara: Ohdaigahara). A, aedeagus; B, 9th ventrite of male; C, 9th and 10th terga of
male; D, posterior part of 8th ventrite of male; E, 6th and 7th ventrites of male. Scale 1: 0.1 mm for A, 0.2 mm
for C, D; scale 2: 0.1 mm for B; scale 3: 0.25 mm for E.

Type material examined. Holotype: ♂ (cP), Ohdaigahara (1,600 m), Nara Pref., 23. ix. 1973,
K. Sawada leg.
Distribution. Japan: Honshu (Nara Pref.).
Redescription. Male: Body 3.1 mm (fore body 1.4 mm) in length. Body weakly shining andalmost black to black; labrum dark red; antennae and legs yellowish brown to reddish brown.

The Steninae of Japan Part 3

15

Body with punctures small to moderately large, round to elliptical, and also pronotum and elytra
partially with coarse to subrugose punctures. Head shallowly concave, with a pair of broad
depressions; antennae moderately long, thin; pronotum with surface uneven, with a median longitudinal furrow very indistinct; elytra with surface slightly uneven; abdomen subcylindrical,
thin, subparallel-sided; lateroventrites each very thin, with a line of ﬁne punctures, tergoventrite
sutures distinct.
Abdomen (Fig. 3E) modiﬁed with a shallow depression on the 6th, the 4-partitioned depressions of various size on the 7th, and an arcuate, shallow emargination on the 8th ventrite; 9th tergum (Fig. 3C) with ventral apophyses long; 9th ventrite (Fig. 3B) with macrosetae moderately
long, apicolateral teeth small, acute, apicolateral setae moderately long; 10th tergum (Fig. 3C)
almost rounded posteriorly. Aedeagus (Fig. 3A) well-sclerotized, with median lobe broad, wellrounded at apicolateral corners; apical sclerotized area with its median part protruding posteriorly, about 1/3 times as broad as the apicolateral part of median lobe, obtusely rounded apically.
Endophallus (Fig. 3A) with copulatory tube short, bifurcate apically, with right process longer
and thinner than left one; dorsolateral bands very thin; expulsion hooks broadly separated, almost
crescent-shaped; diverticulum when evaginated, strongly constricted medially so that its anterior
and posterior diverticula are distinctly recognizable; ventromedian bands long, moderately broad.
Parameres (Fig. 3A) very thick, each fulcate at apex; apical area long, mesially with 3 long setae
at base and 3 long setae at apex.
Female: Unknown.
Biology and ecology. S. kajika is a rare species. The beetle of this species inhabits leaf litterin the natural forest of a mountainous region.
Remarks. Among the Japanese species of satsuki-group, it seems that there is no closely
allied species to S. kajika. This species is thus easily separable from the other species of thisgroup by the aedeagal median lobe having the apical sclerotized area with its median partobtusely rounded apically (Fig. 3A). S. kajika may be related to the European species S. pallipes
and S. kolbei, but it is separable from by the latter 2 species by the aedeagal median lobe having
the apical sclerotized area with its median part obtusely rounded apically (Fig. 3A) and the copulatory tube bifurcated into 2 processes of diﬀerent length at the apex (Fig. 3A).
Etymology. The speciﬁc epithet of this species is derived from the Japanese term whichmeans a river ﬂog, kajika.
Stenus okayamaensis Naomi(Figs. 4A–E, 130D)
Stenus okayamaensis Naomi, 2021: 67.
Type material examined. Holotype: ♂ (KUMF), Mt. Gion, Takahashi City, Okayama Pref.,27. iii. 2005, Y. Fujiya leg. Paratype: 1 ♂, Uzando, Niimi City, Okayama Pref., 7. ix. 2009,
O. Yamaji leg.
Distribution. Japan: Honshu (Okayama Pref.).
Redescription. Male: Body 3.9–4.1 mm (fore body 1.5–1.6 mm) in length. Body weakly shining and black; labrum almost black; antennae dark red to reddish brown; legs yellowish brown toreddish brown. Body with punctures small to moderately large, round to elliptical, and elytra also
partially with subrugose punctures. Head moderately concave, with a pair of longitudinal-oblique
to mesially-curved furrows; antennae short to moderately long, thin; pronotum with surface

16

Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

Fig. 4. Stenus okayamaensis Naomi (Okayama: A, C–E, Takahashi, B, Niimi). A, aedeagus; B, 9th ventrite ofmale; C, 9th and 10th terga of male; D, elytra and 3rd tergum; E, 7th and 8th ventrites of male. Scale 1:
0.1 mm for A, B; scale 2: 0.2 mm for C; scale 3: 0.3 mm for D, 0.2 mm for E.

The Steninae of Japan Part 3

17

uneven, with a median longitudinal furrow indistinct; elytra (Fig. 4D) with surface uneven; abdomen subcylindrical, subparallel-sided; lateroventrites each very thin, ﬁnely punctate, tergoventrite sutures distinct.
Abdomen (Fig 4E) modiﬁed with a ﬂat area on the 7th, and a shallow emargination on the
8th ventrite; 9th tergum (Fig. 4C) with ventral apophyses very long, thin; 9th ventrite (Fig. 4B)
with macrosetae, apicolateral teeth moderately long, very acute, apicolateral setae long; 10th tergum (Fig. 4C) entire. Aedeagus (Fig. 4A) with median lobe moderately elongate, expanded laterally at apicolateral parts; apical sclerotized area short, rounded apically, weakly declivous toward
dorsal side when seen ventrally. Endophallus (Fig. 4A) with copulatory tube having basal chamber large, ovoidal, main tube ﬂagellar, very long; dorsolateral bands short, very thin; expulsion
hooks lost; ventromedian bands long, relatively thin, curved. Parameres (Fig. 4A) each almost
straight, acutely pointed at apex; apical area very long, mesially with 3 long and 2 or 3 shortsetae.
Female: Unknown.
Biology and ecology. S. okayamaensis is a rare species. The beetles of this species inhabit
leaf litter in the natural forests of mountainous regions.
Remarks. S. okayamaensis is a sister species of S. satsuki, and it is distinctly separable fromthe latter species by the aedeagal median lobe with its apical sclerotized area slightly developed
and rounded apicomedially (Fig. 4A), the ﬂagellar copulatory tube longer (Fig. 4A), and theparamere simply acutely pointed at the apex, with its apical area with 3 long setae at the base(Fig. 4A).
Stenus satsuki Naomi(Figs. 5A–F, 130E)
Stenus satsuki Naomi, 1987: 1; Herman, 2001: 2378; Naomi & Puthz, 2013: 144.
Type material examined. Holotype: ♂ (KUF), Mt. Ishizuchi, Ehime Pref., 16. vi. 1981, S.
Naomi leg. Paratype: 1 ♂, same data as holotype.
Other material examined. [SHIKOKU]: 1 ♀, Nanokawagoe, Saijyo City, Ehime Pref., 17. vi.
2005, T. Kitano leg.
Distribution. Japan: Shikoku (Ehime Pref.).
Redescription. Male and female: Body 3.5–3.7 mm (fore body 1.5–1.6 mm) in length. Body
weakly shining and black; labrum dark reddish brown; antennae reddish brown to dark brown;legs yellowish brown to reddish brown. Body with punctures small to moderately large, round to
elliptical, and also pronotum partially with coarse punctures and elytra partially with large,coarse punctures. Head shallowly concave, with a pair of longitudinal-oblique furrows; antennae
short to moderately long, thin; pronotum with surface slightly uneven, with a median longitudinal furrow indistinct; elytra with surface uneven; abdomen subcylindrical, slightly tapering posteriorly to subparallel-sided; lateroventrites each very thin, ﬁnely punctate, tergoventrite sutures
distinct.
Male: Abdomen (Fig 5E) modiﬁed with a shallow depression on the 7th, and an arcuate
emargination on the 8th ventrite; 9th tergum (Fig. 5A) with ventral apophyses very long; 9th
ventrite (Fig. 5B) with macrosetae moderately long, apicolateral teeth moderately long, acute,apicolateral setae moderately long; 10th tergum (Fig. 5A) entire. Aedeagus (Fig. 5C) withmedian lobe moderately elongate, almost truncate apically, weakly expanded laterally and angu-

18

Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

Fig. 5. Stenus satsuki Naomi (Ehime: A–C, E, Mt. Ishizuchi, D, F, Saijyo). A, 9th and 10th terga of male; B, 9th
ventrite of male; C, aedeagus; D, spermatheca; E, 7th ventrite and 8th ventrite of male; F, posterior part ofgonocoxite. Scale 1: 0.2 mm for A, C, 0.1 mm for F; scale 2: 0.05 mm for D; scale 3: 0.1 mm for B, 0.2 mm forE.

The Steninae of Japan Part 3

19late at apicolateral parts; apical sclerotized area (Fig. 5C) almost lost or very weakly swollen apicomedially. Endophallus (Fig. 5C) with copulatory tube having main tube ﬂagellar, long; dorsolateral bands short, very thin; expulsion hooks lost; ventromedian bands long, relatively thin.
Parameres (Fig. 5C) each subulate at apex; apical area very long, large, mesially with 6 to 7 shortsetae along dorsal margin of basal 2/3 and 2 short setae along the middle of ventral margin.
Female: Eighth ventrite obtuse posteromedially; gonocoxites (Fig. 5F) each with apicolateral
tooth very acute, apicolateral setae very long. Spermatheca (Fig. 5D) with capsule rounded apically; striped duct moderately long and broad; duct moderately long, thin, coiled with 4 turns;
basal valve very short; basal pouch bowl-shaped, submembranous.
Biology and ecology. S. satsuki is a rare species. The beetles of this species inhabit leaf litterin the natural forests of mountainous regions.
Remarks. S. satsuki is a sister species of S. okayamaensis, and it is distinctly separable fromthe latter species by the aedeagal median lobe with its apical sclerotized area almost lost, i.e.,
truncate apically (Fig. 5C), the ﬂagellar copulatory tube shorter (Fig. 5C), and the paramere with
its apical area falcate and basally with 4 short setae (Fig. 5C).
Etymology. The speciﬁc epithet of this species is derived from the Japanese name of a groupof Rhododendron trees, satsuki.
Stenus hime Naomi & Puthz(Fig. 6A–I)
Stenus hime Naomi & Puthz, 1994: 259; Herman, 2001: 2214; Naomi & Puthz, 2013: 144.
Type material examined. Holotype: ♂ (cP), Mt. Ibuki, Shiga Pref., 1. xi. 1973, K. Sawada
leg. Paratype: 1 ♀ (cP), same data as holotype.
Distribution. Japan: Honshu (Shiga Pref.).
Redescription: Male and female: Body 2.6–3.2 mm (fore body 1.3–1.5 mm) in length. Body
weakly shining; head and abdomen black; pronotum and elytra dark red near black; labrum reddish brown to black; antennae and legs yellowish brown to reddish brown. Body with punctures
small to moderately large, round to elliptical, and also pronotum partially with subrugose punctures and elytra partially with large, subrugose punctures. Head shallowly to moderately concave,with a pair of longitudinal-oblique furrows; antennae very short, thin; pronotum with surface
uneven, with a median longitudinal furrow indistinct; elytra with surface uneven; abdomen subcylindrical, slightly tapering posteriorly to subparallel-sided; lateroventrites thin, sparsely punctate, tergoventrite sutures distinct.
Male: Abdomen (Fig. 6E) modiﬁed with a very shallow depression on the 6th, a narrower,
shallow depression on the 7th, and an arcuate, moderately deep emargination on the 8th ventrite;
9th tergum (Fig. 6B) with ventral apophyses very long; 9th ventrite (Fig. 6C) with apicolateral
teeth short, very acute, apicolateral setae short; 10th tergum (Fig. 6B) shallowly emarginate posteromedially. Aedeagus (Fig. 6A) with median lobe broadest at apicolateral corners, angulate atapex; apical sclerotized area developed only at apicomedian part, by a narrow, apical rim. Endophallus (Fig. 6A) with copulatory tube (Fig. 6G) having basal chamber small, main tube sticklike, strongly bend then turning anteriad at apical portion; expulsion hooks (Fig. 6F) each shoeshaped, laterally with a hump in the middle; dorsolateral bands very thin; ventromedian bands
long, broad. Parameres (Fig. 6A) each thick at base, acutely pointed at apex; apical area very
long, mesially with 9 to 10 short setae.

20

Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

Fig. 6. Stenus hime Naomi & Puthz (Shiga: Mt. Ibuki). A, aedeagus with outthrusted endophallus; B, 9th and10th terga of male; C, 9th ventrite of male; D, posterior part of 8th ventrite of male; E, 6th and 7th ventrites ofmale; F, apical part of aedeagus with outthrusted endophallus; G, copulatory tube; H, posterior part of gonocoxite; I, spermatheca. Scale 1: 0.1 mm for A, H, 0.05 mm for F, G; scale 2: 0.2 mm for B–D; scale 3: 0.2 mm
for E; scale 4, 0.1 mm for I.

The Steninae of Japan Part 3

21

Female: Eighth ventrite (Fig. 6I) obtuse posteromedially; gonocoxites (Fig. 6H) each withapicolateral tooth short, acute, apicolateral setae short. Spermatheca (Fig. 6I) small, with capsulespherical; collum longer than capsule; duct extremely short, once distinctly bent.
Biology and ecology. S. hime is a rare species. The beetles of this species inhabit leaf litter
heaped in the natural forests of a mountainous region.
Remarks. S. hime is allied to S. intermixtus and S. kannoi, but it is separable from the latter 2
species by the aedeagal median lobe with its apical sclerotized area developed only at the apicomedian part (Fig. 6A), the copulatory tube with its main tube thinner, almost attenuate excepting
the apical portion which is turned anteriad (Fig. 6G), and the endophilic expulsion hook shoeshaped, laterally with a hump (Fig. 6F).
Etymology. The speciﬁc epithet of this species is derived from the Japanese name of princess, hime.
Stenus intermixtus Puthz(Figs. 7A–I, 130F)
Stenus intermixtus Puthz, 1993: 164; Herman, 2001: 2234; Naomi & Puthz, 2013: 144.
Type material examined. Holotype: ♀ (NHMG), Jyoshin-Etsu Highland National Park, Shigahighland (1,500 m), Nagano Pref., 23. viii. 1980, I. Löbl leg. Paratype: 1 ♀, same data as holotype.
Other material examined. [HONSHU]: 3 ♂3 ♀, Shirakoma, Mt. Kitayatsu, Nagano Pref.,13–16. ix. 1996, T. Ito leg.; 2 ♂4 ♀, Shirabiso Highland, Ue Vil., Nagano Pref., 16. xi. 1999, S.
Nomura leg.; 1 ♂1 ♀, Shiokawa, Ohshika Vil., Nagano Pref., 8. xi. 1999, S. Nomura leg.; 1 ♂1 ♀,Nomugi Pass, Nagawa Vil., Nagano Pref., 8. viii. 1996, T. Kishimoto leg.; 1 ♂, Mt. Norikura,
Azumi Vil., Nagano Pref., 20. viii. 1996, S. Nomura leg.; 1 ♀, Oohira Pass, Nagiso-cho, Nagano
Pref., 15. xi. 1999, S. Nomura leg.; 1 ♀, Mt. Yatsu, Chino City, Nagano Pref., 19. viii. 1996, S.
Nomura leg.; 1 ♀, Ame Pond, Yachiho Vil., Nagano Pref., 19. viii. 1996, S. Nomura leg.; 1 ♀,Mugikusa, Nagano Pref., 16. ix. 1996, H. Ohira leg.; 1 ♂, Mt. Kurai, Gifu Pref., 28. x. 2017, T.
Ito leg.; 1 ♂, Hirayu, Gifu Pref., 24. viii. 1987, S. Nomura leg.; 1 ♂, Tsukechi Valley, Kakomo
Vil., Gifu Pref., 15. xi. 1999, S. Nomura leg.; 2 ♂, Mikuni Pass, Ohtaki Vil., Saitama Pref., 30. x.
1999, S. Nomura leg.; 1 ♂, Yanagisawa Pass, Enzan City, Yamanashi Pref., 17. xi. 1999, S.
Nomura leg.
Distribution. Japan: Honshu (Kanto and Chubu Districts).
Redescription: Male and female: Body 2.6–3.3 mm (fore body 1.4–1.5 mm) in length. Body
moderately shining; Head and abdomen black; pronotum and elytra dark red; labrum reddish
brown to dark reddish brown; antennae and legs reddish brown. Body with punctures small tomoderately large, round to elliptical, and also pronotum and elytra partially with coarse to subrugose punctures. Head shallowly to moderately concave, with a pair of mesially-curved furrows;
antennae short, thin to slightly thick; pronotum with surface uneven, with a median longitudinalfurrow indistinct; elytra with surface slightly uneven to uneven; abdomen subcylindrical, slightly
tapering posteriorly to subparallel-sided; lateroventrites lost, tergoventrite sutures distinct.
Male: Abdomen (Fig. 7H) modiﬁed with an arcuate, very broad emargination on the 8th ventrite; 9th tergum (Fig. 7B) with ventral apophyses long; 9th ventrite (Fig. 7G) with apicolateral
teeth short, very acute, apicolateral setae slightly short; 10th tergum (Fig. 7B) rounded posteriorly. Aedeagus (Fig. 7A) with median lobe broad, broadest at apicolateral corners, obtuse at

22

Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

Fig. 7. Stenus intermixtus Puthz (Nagano: A, B, E, G, H, Mt. Kitayatsu, C, D, I, Nagawa, F, Mt. Norikura). A,
aedeagus; B, 9th and 10th terga of male; C, spermatheca; D, gonocoxites, proximal part of spermatheca andspermatophore deposited by male during copulation; E, copulatory tube; F, apical process of copulatory tube;
G, 9th ventrite of male; H, posterior part of 8th ventrite of male; I, posterior part of 8th ventrite of female.
Scale 1: 0.1 mm for A, B, D, G–I; scale 2: 0.05 mm for C, E, F.

The Steninae of Japan Part 3

23apex; apical sclerotized area broad-subtriangular, very shallowly emarginate at posterolateralpart. Endophallus (Fig. 7A) with copulatory tube thick, becoming gradually broader apicad, with
an apical process short, thin (Fig. 7E) or attenuate (Fig. 7F), and with a ventrally turned process
thick, moderately curved (Fig. 7E); dorsolateral bands visible only in anterior portions; expulsion
hooks each with anterior plate subtriangular, smaller than posterior plate which is also subtriangular; ventromedian bands long, broad. Parameres (Fig. 7A) each very acutely pointed at apex;
apical area long, weakly swollen mesially at base, mesially also with 6 short setae at base, glabrous in the apical 1/2.
Female: Eighth ventrite obtuse posteromedially (Fig. 7I) or almost rounded posteriorly;
gonocoxites (Fig. 7D) each with apicolateral tooth short, acute, apicolateral setae slightly short.
Spermatheca (Fig. 7C, D) with capsule very large, spherical; collum shorter than capsule, duct
2-segmented; gland moderately large, with opening located on the lateral side of the 2nd segmentof duct.
Biology and ecology. The beetles of S. intermixtus inhabit leaf litter heaped in the natural forests of mountain to high mountainous regions.
Remarks. S. intermixtus is the sister species of S. kannoi, but it is separable from the latter
species by the 6th and 7th abdominal ventrites of male each simple, the aedeagal median lobe
with its apical sclerotized area very shallowly emarginate at the posterolateral part (Fig. 7A), thecopulatory tube with its ventrally turned process thick, moderately curved (Fig. 7E), and thespermatheca with its basal duct much shorter (Fig. 7C).
A spermatophore deposited into a genital chamber of female by a male beetle during copulation was observed at the opening of genital chamber (Fig. 7D).
Stenus kannoi Naomi, Nomura & Puthz sp. nov.
(Figs. 8A–H, 130G)
Type material examined. Holotype: ♂ (KUMF), Tatedani, Fujiwara-cho, Inabe City, Mie
Pref., 3. xii. 2002, K. Kanno leg. Paratype: 1 ♀, same data as holotype.
Distribution. Japan: Honshu (Mie Pref.).
Description: Male and female: Body 2.7–3.3 mm (fore body 1.3–1.5 mm) in length. Body
weakly shining and black; labrum dark brown to black; antennae and legs reddish brown. Body
with punctures small to moderately large, round to ovoidal, and also pronotum and elytra partially with coarse punctures. Head shallowly concave, with a pair of broad, longitudinal-obliqueor mesially-curved depressions; antennae very short to short, thin; pronotum with surface
uneven, with a median longitudinal furrow indistinct; elytra with surface uneven; abdomen subcylindrical, slightly tapering posteriorly to subparallel-sided; lateroventrites lost, tergoventrite
sutures distinct.
Male: Abdomen (Fig. 8B) modiﬁed with a broad ﬂat area on the 6th, an elongate, shallow
depression on the 7th, and a very shallow emargination on the 8th ventrite; 9th tergum (Fig. 8A)
with ventral apophyses long; 9th ventrite (Fig. 8C) with apicolateral teeth short, acute, apicolateral setae short; 10th tergum (Fig. 8A) very slightly emarginate posteriorly. Aedeagus (Fig. 8G)with median lobe moderately broad, broadest at apicolateral corners, obtuse at apex; apical sclerotized area broad-subtriangular in shape, very weakly rounded at posterolateral margin. Endophallus (Fig. 8G) with copulatory tube thick, weakly curved, bifurcated apically, with an apical
process moderately thick (Fig. 8D) and with a ventrally turned process thin, strongly turned (Fig.
8D); dorsolateral bands moderately long, thin; expulsion hooks (Fig. 8H) each elongate-triangu-

24Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

Fig. 8. Stenus kannoi Naomi, Nomura & Puthz sp. nov. (Mie: Inabe). A, 9th and 10th terga of male; B, 6th to 8th
ventrites of male; C, 9th ventrite of male; D, apical part of copulatory tube; E, spermatheca; F, posterior partof gonocoxite; G, aedeagus; H, endophallic expulsion hooks. Scale 1: 0.1 mm for A, C, G, 0.05 mm for E, H;
scale 2: 0.3 mm for B; scale 3: 0.05 mm for D, 0.1 mm for F.

The Steninae of Japan Part 3

25

lar in shape, with anterior plate divided antero-posteriorly into 2 subplates; ventromedian bands
moderately long, moderately broad. Parameres (Fig. 8G) each very acutely pointed at apex; apical area moderately long, weakly swollen mesially at base, mesially also with 2 long and 3 shortsetae, glabrous in the apical 1/2.
Female: Eighth ventrite obtuse posteromedially; gonocoxites (Fig. 8F) each with apicolateral
tooth slightly short, acute, apicolateral setae long. Spermatheca (Fig. 8E) moderately sclerotized,with capsule very large, almost spherical; collum shorter than capsule, duct very short, with 1
turn; gland moderately large, with opening located on the lateral side of the 2nd segment of duct.
Biology and ecology. The beetles of S. kannoi inhabit leaf litter heaped in the natural forestsof a low mountainous region.
Remarks. S. kannoi is the sister species of S. intermixtus, and it is separable from the latter
species by the 6th and 7th ventrites of male each modiﬁed with the posteromedian depression(Fig. 8B), the aedeagal median lobe with its apical sclerotized area very weakly rounded at theposterolateral margin (Fig. 8G), the copulatory tube with its ventrally turned process thin andstrongly turned (Fig. 8D), and the spermatheca with its basal duct much longer (Fig. 8E).
Etymology. This new species is named after Mr. Kenji Kanno (Mie) who collected theStenus-beetle designated as the type specimens.
Stenus volkerputhzi Naomi, Nomura & Kamezawa(Figs. 9A–G, 130H)
Stenus volkerputhzi Naomi, Nomura & Kamezawa, 2015: 324.
Type material examined. Holotype: ♂ (NMNST), Murodo, Mt. Hakusan, Ishikawa Pref.,1. x. 2002, S. Nomura leg. Paratypes: 1 ♂3 ♀ (NMNST), same data as holotype; 3 ♂8 ♀, samedata as above.
Distribution. Japan: Honshu (Ishikawa Pref.).
Redescription: Male and female: Body 3.0–3.6 mm (fore body 1.5–1.6 mm) in length. Body
moderately shining; head black with clypeofrontal area dark red; pronotum and elytra dark red;abdomen black; labrum reddish brown; antennae dark red; legs yellowish brown to reddish
brown. Body with punctures small to moderately large, round to elliptical, and also pronotumand elytra partially with coarse punctures. Head moderately concave, with a pair of longitudinaloblique furrows; antennae very short to short, thin to slightly thick; pronotum with surface
slightly uneven, with a median longitudinal furrow distinct; elytra with surface uneven, eachoften with a basal keel and also with an indistinct, large fovea on each side of basal keel; abdomen subcylindrical, slightly tapering posteriorly to subparallel-sided; lateroventrites lost, tergoventrite sutures distinct.
Male: Abdomen (Fig. 9D) modiﬁed with a very shallow, elongate depression on the 7th, anda shallow, arcuate emargination on the 8th ventrite; 9th tergum (Fig. 9B) with ventral apophyses
relatively short; 9th ventrite (Fig. 9C) with apicolateral teeth short, very acute, apicolateral setae
short; 10th tergum (Fig. 9B) almost rounded posterolaterally. Aedeagus (Fig. 9A) with median
lobe broad, well-rounded apically; apical sclerotized area semicircular, sparsely covered withvery small pores along marginal area. Endophallus (Fig. 9A, G) with copulatory tube havingbasal chamber elongate-spherical in shape, main tube thin, straight in the basal 1/2, weakly
curved in the apical 1/2, pointed at apex; dorsolateral bands visible only in posterior portion;
expulsion hooks missing (Fig. 9A) or highly atrophied to be a pair of very small sclerites (Fig.

26

Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

Fig. 9. Stenus volkerputhzi Naomi, Nomura & Kamezawa (Ishikawa: Mt. Hakusan). A, aedeagus; B, 9th and 10th
terga of male; C, 9th ventrite of male; D, 7th and 8th ventrites of male; E, posterior part of gonocoxite; F,
spermatheca; G, endophallic copulatory tube. Scale 1: 0.1 mm for A, C, E–G; scale 2: 0.1 mm for B; and scale
3: 0.3 mm for D.

The Steninae of Japan Part 3279G); ventromedian bands moderately long, broad. Parameres (Fig. 9A) moderately thick,sparsely covered with very small pores in the middle, rounded apically when seen laterally; apical area very long, not swollen mesially at base, mesially also with 7 to 8 setae of various length.
Female: Eighth ventrite pointed posteromedially; gonocoxites (Fig. 9E) each with apicolateral tooth very short, acute, apicolateral setae long. Spermatheca (Fig. 9F) moderately sclerotized, with capsule elongate-subovoidal in shape; collum thin, much shorter than capsule; ductvery short, distinctly once bent.
Biology and ecology. The beetles of S. volkerputhzi inhabit leaf litter heaped in the naturalforests of a high mountainous region.
Remarks. S. volkerputhzi is allied to S. intermixtus and S. kannoi, but it is separable from thelatter 2 species by the aedeagal median lobe rounded apically (Fig. 9A), the copulatory tube thinner (Fig. 9G), the endophallic expulsion hook atrophied into a small sclerite (Fig. 9G), and thespermatheca with its capsule cucumber-like (Fig. 9F).
Etymology. This species is named after the third author of this paper, Volker Puthz
Stenus uneme Naomi(Figs. 10A–I, 130I)
Stenus uneme Naomi, 1989a: 8; Herman, 2001: 2427; Naomi & Puthz, 2013: 144.
Type material examined. Holotype: ♂ (KUF), Omogokei, Ehime Pref., 15. vi. 1981, S.
Naomi leg. Paratype: 1 ♂2 ♀, same data as holotype.
Other material examined. [HONSHU]: 2 ♂1 ♀, Mt. Koya, Wakayama Pref., 1. v. 1985, T. Itoleg.; 1 ♂1 ♀, Tamagawa Valley, Mt. Koya, Wakayama Pref., 29. iv. 1987, T. Watanabe leg.;2 ♂1 ♀, Mt. Kôjin, Nara Pref., 2. v. 1968, T. Ito leg. [SHIKOKU]: 2 ♂1 ♀, Amagoi Fall, Kamiyama-cho, Tokushima Pref., 3. v. 1999, M. Yoshida leg.; 2 ♂1 ♀, Mt. Takashiro, Kisawa Vil.,
Tokushima Pref., 3. vii. 2004, M. Yoshida leg.; 1 ♂, Tokuen Temple, Saga, Sanagouchi Vil.,
Tokushima Pref., 13. viii. 1968, M. Yoshida leg.; 1 ♂, Mt. Odami (800 m), Ehime Pref., 19. vii.
1993, M. Sakai.; 1 ♂, Mt. Ohkawa, Mannô-cho, Kagawa Pref., 28. vi. 2008, H. Fujimoto leg.;1 ♂, Kaminishi-koide River, Takamatsu City, Kagawa Pref., 24. v. 2008, H. Fujimoto leg.; 1 ♂,Kami City, Kochi Pref., 8. ix. 2007, T. Miyata leg.; 1 ♂, same locality, 23. ix. 2007, T. Miyata
leg.
Distribution. Japan: Honshu (Wakayama and Nara Prefs.) and Shikoku.
Redescription. Male and female: Body 2.7–3.5 mm (fore body 1.4–1.6 mm) in length. Body
weakly shining; head black; pronotum, elytra and abdomen dark red to dark brown; labrum reddish brown to dark brown; antennae and legs yellowish brown to reddish brown. Body with
punctures round to almost round, small to moderately large, and also elytra with large punctures.
Head shallowly concave, with a pair of longitudinal-oblique depressions; antennae short to moderately long, thin; pronotum with surface even to slightly uneven, with a median longitudinal furrow very indistinct; elytra with surface slightly uneven; abdomen almost cylindrical, slightly
tapering posteriorly to subparallel-sided; lateroventrites lost, tergoventral sutures very thin.
Male: Abdomen (Fig. 10E) modiﬁed with a shallow emargination on the 8th ventrite; 9th tergum (Fig. 10G) with ventral apophyses thin, short; 9th ventrite (Fig. 10D) very ﬁnely serrate
posteriorly, with apicolateral setae very acute, apicolateral setae moderately long; 10th tergum(Fig. 10G) entire. Aedeagal median lobe (Fig. 10C) sclerotized, relatively broad, broadest at apicolateral corners, rounded or obtusely pointed at apex; apical sclerotized area hardly developed.

28

Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

Fig. 10. Stenus uneme Naomi (Ehime: A, H, Omogokei; Wakayama: B, I, Mt. Koya; Ehime: C, D, F, G, Mt.
Odami; Kagawa: E, Ohkawa). A, B, spermatheca; C, aedeagus; D, 9th ventrite of male; E, 8th ventrite ofmale; F, endophallic expulsion hooks; G, 9th and 10th terga of male; H, I, posterior part of gonocoxite. Scale
1: 0.05 mm for A, B, 0.1 mm for C; scale 2: 0.2 mm for D, E, G, 0.05 mm for F, 0.1 mm for H, I.

The Steninae of Japan Part 3

29

Endophallus (Fig. 10C) with copulatory tube having basal chamber ovoidal, main tube long,attenuate; dorsolateral bands pigmented only at bases; explusion hooks (Fig. 10F) each withanterior plate well- rounded posteriorly, incompletely demarcated by a transverse, narrow crevice
from posterior plate; ventromedian bands very short, thin, moderately diverging anteriorly. Parameres (Fig. 10C) slender, each gently curved mesially, moderately pointed at apex; apical area
long, thin, mesially with 3 to 4 long setae in the most apical part (Fig. 10C) or in about apical
1/2.
Female: Eighth ventrite (Fig. 10E) pointed posteromedially; gonocoxites (Fig. 10H, I) eachwith apicolateral teeth very acute, apicolateral setae very long. Spermatheca (Fig. 10A, B) with
capsule developed or not; striped duct long to very long, thick; duct relatively short to moderately long, moderately thick, loosely coiled mostly at the most distal turn of duct, with 4 to 6
turns; gland almost spherical, with long or short ciliae, with opening located on the mesial side ofduct between 1st and 2nd turns (Fig. 10B) or 2nd and 3rd turns (Fig. 10A); basal valve very short
to short; basal duct well-sclerotized, moderately long.
Biology and ecology. The beetles of S. uneme inhabit leaf litter heaped in the natural forestsof low mountainous to mountainous regions. In Mt. Koya (Honshu) and Mt. Odami (Shikoku),
the beetles inhabit wet litter heaped along the mountain torrents.
Remarks. Because of the peculiar structures of aedeagus and its endophallic components, it isconsidered that no species is closely related to S. uneme among the Japanese species of satsukigroup. Thus, S. uneme is easily separable from the other species of this group by the aedeagal
paramere with several long setae only at the most apical part (Fig. 10C).
Etymology. The speciﬁc epithet of this species is derived from the Japanese name of domestic servants of the emperor in the ancient periods, uneme.
Stenus taoi Naomi(Figs. 11A–I, 130J)
Stenus taoi Naomi, 1989a: 10; Herman, 2001: 2412; Naomi & Puthz, 2013: 142.
Stenus nemoralis Naomi, 2015: 17. New synonym.
Type material examined. Holotype of S. taoi: ♀ (KUF), Hirogawara, Mt. Shiranekita,
Yamanashi Pref., 9–13. vii. 1982, S. Naomi leg. Paratype of S. taoi: 1 ♂ (cP) 1 ♀, same data as
holotype.
Holotype of S. nemoralis (CBM): ♂, Kami-nikkawa Pass, Enzan, Kôshû City, Yamanashi
Pref., 16. x. 2010, T. Watanabe leg. Paratype of S. nemoralis: 1 ♂, Daibosatsu, Yamanashi Pref.,26. vi. 1991, T. Ito leg.
Other material examined. [HONSHU]: 1 ♂2 ♀, Yanagisawa Pass, Tabayama Vil., Yamanashi
Pref., 5. v. 2002, S. Nomura leg.
Distribution. Japan: Honshu (Yamanashi Pref.).
Redescription. Male and female: Body 3.2–3.5 mm (fore body 1.5–1.7 mm) in length. Body
moderately shining; head and abdomen black; pronotum and elytra dark red to dark brown;
labrum dark red to dark brown; antennae and legs reddish brown. Body with punctures small tomoderately large, round to elliptical, and also pronotum partially with coarse punctures and elytra partially with large punctures. Head shallowly concave, with a pair of longitudinal-obliquefurrows; antennae short, thin; pronotum with surface slightly uneven, with a median longitudinalfurrow indistinct; elytra with surface slightly uneven to uneven; abdomen subcylindrical, slightly

30

Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

Fig. 11. Stenus taoi Naomi (Yamanashi: A, C, Yanagisawa Pass, B, F, Hirogawara, D, E, G–I, Daibosatsu). A, B,
spermatheca; C, F, posterior part of gonocoxite; D, posterior part of 9th tergum and 10th tergum of male; E,
endophallic expulsion hooks; G, posterior part of 8th ventrite of male; H, aedeagus; I, 9th ventrite of male.
Scale 1: 0.1 mm for A, C–F, 0.2 mm for G–I; scale 2: 0.05 mm for B.

The Steninae of Japan Part 3

31

tapering posteriorly to subparallel-sided; lateroventrites and tergoventral sutures lost.
Male: Abdomen (Fig. 11G) modiﬁed with an arcuate emargination on the 8th ventrite; 9th
tergum with ventral apophyses short, thin; 9th ventrite (Fig. 11I) with apicolateral teeth long,acute, apicolateral setae moderately long; 10th tergum (Fig. 11D) almost rounded posteriorly.
Aedeagus (Fig. 11H) with median lobe broad, obtusely angulate at apicolateral corners, obtusely
pointed at apex; apical sclerotized area composed of the narrow, apical rim. Endophallus (Fig.
11H) with copulatory tube long, having basal chamber composed of 2 robust rods, main tube
with basal tube very thick, apical tube very thin, weakly curved at apical part; explusion hooks(Fig. 11E) widely separated, each slightly narrow; ventromedian bands moderately broad, short.
Parameres (Fig. 11H) thin, each acutely pointed at apex; apical area very short, slightly swollen
mesially at base, mesially also with 9 to 10 short setae.
Female: Eighth ventrite minutely pointed posteromedially; gonocoxites (Fig. 11C, F) eachwith apicolateral teeth short to long, very acute, apicolateral setae very long. Spermatheca (Fig.
11A, B) with capsule long (Fig. 11B) or hardly developed (Fig. 11A); striped duct long, moderately thick to thick; duct very long, thin, tightly coiled; basal valve short; basal duct sclerotized,
moderately long and thick; basal pouch large, conical.
Biology and ecology. The beetles of S. taoi inhabit leaf litter heaped in the natural forests ofmountainous to high mountainous regions.
Remarks. Both S. taoi Naomi, 1989a and S. nemoralis Naomi, 2015 were described as new
species based on the specimens of beetles collected from the mountainous regions in Yamanashi
Pref., Chubu District. After our close examination during the present study, it was clariﬁed that S.
nemoralis Naomi, 2015 is newly placed in synonymy with S. taoi Naomi, 1989a.
S. taoi is allied to S. nemorosus, but it is separable from the latter species by the aedeagal
median lobe broader (Fig. 11H), the copulatory tube with its basal tube distinctly demarcated by
the diﬀerence of thickness from apical tube (Fig. 11H), and the endophallic expulsion hooknarrower (Fig. 11E).
Etymology. This species is named after Mr. Minoru Tao who collected the Stenus-beetle
designated as the type specimens
Stenus nemorosus Naomi & Y. Watanabe(Fig. 12A–G)
Stenus nemorosus Naomi & Y. Watanabe, 2015: 99.
Type material examined. Holotype: 1 ♂ (TUAA), Hirogawara at the foot of Mt. Shiranekita,
Yamanashi Pref., 11. vi. 1966, Y. Watanabe leg. Paratypes: 1 ♀ (TUAA), same data as holotype;1 ♂1 ♀, same locality, 6. vi. 1964, Y. Watanabe leg.
Distribution. Japan: Honshu (Yamanashi Pref.).
Redescription. Male and female: Body 3.3–3.5 mm (fore body 1.5–1.6 mm) in length. Body
moderately shining; head and abdomen black; pronotum and elytra dark reddish brown to dark
red near black; labrum dark red to dark brown; antennae and legs reddish brown. Body with
punctures small to moderately large, round to ovoidal, and also pronotum partially with coarse tosubrugose punctures and elytra partially with large, subrugose punctures. Head shallowly tomoderately concave, with a pair of longitudinal-oblique furrows; antennae short, thin to slightly
thick; pronotum with surface slightly uneven, with a median longitudinal furrow indistinct; elytra
with surface slightly uneven to uneven; abdomen subcylindrical, slightly tapering posteriorly to32

Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

Fig. 12. Stenus nemorosus Naomi & Watanabe (Yamanashi: Hirogawara). A, spermatheca; B, 9th and 10th tergaof male; C, aedeagus; D, 8th ventrite of female; E, 9th ventrite of male; F, gonocoxites; G, endophallic expulsion hooks. Scale 1: 0.2 mm for B, C, E, F, 0.1 mm for G, 0.05 mm for A; scale 2: 0.2 mm for D.

The Steninae of Japan Part 3

33

subparallel-sided; lateroventrites and tergoventral sutures almost lost.
Male: Abdomen modiﬁed with an arcuate emargination on the 8th ventrite; 9th tergum withventral apophyses thin, moderately long; 9th ventrite (Fig. 12E) with apicolateral teeth short,acute; 10th tergum (Fig. 12B) rounded posteriorly. Aedeagus (Fig. 12C) with median lobe moderately broad, narrowly rounded at apicolateral corners, with a pointed apicomedian cusp; apicalsclerotized area hardly developed. Endophallus (Fig. 12C) with copulatory tube long, main tube
thick in the basal 1/2, more or less tapering apicad, with basal tube demarcated by a weak constriction from apical tube; dorsolateral bands long, thin; explusion hooks (Fig. 12G) broadly connected by a membrane, each slightly broad, with anterior plate minutely hooked or bi-hooked atanterior tip; ventromedian bands moderately broad, short. Parameres (Fig. 12C) thin, eachacutely pointed at apex; apical area very short, slightly swollen mesially at base, mesially alsowith 9 to 10 short setae.
Female: Eighth ventrite minutely pointed posteromedially; gonocoxites (Fig. 12F) each withapicolateral teeth short, very acute, apicolateral setae long. Spermatheca (Fig. 12A) with capsulevery long; striped duct long, very thick; duct very long, thin to moderately broad, tightly coiled;gland large, ovoidal, with opening located on the lateral side of duct between the last 6th and 7thturns; basal valve short; basal pouch conical.
Biology and ecology. The beetles of S. nemorosus inhabit leaf litter heaped in the natural forests of a mountainous region.
Remarks. Our present study shows that S. nemorosus is also allied to S. trispinosus Naomi &Nomura, 2015, which was previously classiﬁed into the kasumi-subgroup of asyura-group(Naomi et al., 2019, p. 24). This is because these two species possess in common such conditions
as the aedeagal median lobe moderately broad and narrowly rounded at the apicolateral corners(Fig. 12C), the endophallic expulsion hooks broadly connected each other by a membrane (Fig.
12G), the paramere with its apical area very short (Fig. 12C), and the spermatheca with its ductvery long and tightly coiled (Fig. 12A), in addition to their similar habitus and color of body.
Thus, S. trispinosus is here transferred to the satsuki-group.
S. nemorosus is allied to S. taoi, but it is separable from the latter species by the aedeagal
median lobe narrower (Fig. 12C), the copulatory tube with its basal tube hardly demarcated fromapical tube (Fig. 12C), and the endophallic expulsion hook broader (Fig. 12G). S. nemorosus isalso allied to S. trispinosus, but it is separable from the latter species by the aedeagal median
lobe pointed with the apicomedian cusp (Fig. 12C) and the endophallic expulsion hook with its
anterior plate minutely hooked or bi-hooked at the anterior tip (Fig. 12G).
Stenus fujimontis Puthz(Figs. 13A–I, 130 L)
Stenus fujimontis Puthz, 2001: 46; Naomi & Puthz, 2013: 142.
Type material examined. Holotype: ♂ (SMNHS), Azami-line (1,400 m), East side of Mt Fuji,
Shizuoka Pref., 2. viii. 1999, V. Puthz leg. Paratype: 1 ♀, same data as holotype.
Other material examined. [HONSHU]: 2 ♂1 ♀, Subashiriguchi, Mt. Fuji (2-gome), Shizuoka
Pref., 5. xi. 2010, T. Watanabe leg.; 2 ♂1 ♀, Yamabushi Pass, Doshi Vil., Yamanashi Pref., 16. x.
2000, S. Nomura leg.; 1 ♂1 ♀, Mt. Ishihodo, Nishitanzawa, Kanagawa Pref., 5. x. 2002, T. Watanabe leg.; 1 ♂, Teppôgino-atama, Nishitanzawa, Kanagawa Pref., 12. vi. 2002, T. Watanabe leg.
Distribution. Japan: Honshu (Yamanashi, Shizuoka and Kanagawa Prefs.).

34

Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

Fig. 13. Stenus fujimontis Puthz (Shizuoka, Yamanashi and Kanagawa). A, 9th and 10th terga of male; B 9th ventrite of male; C, aedeagus; D, copulatory tube; E, posterior part of 8th ventrite of male; F, endophallic expulsion hooks; G, gonocoxite; H, 8th ventrite of female. Scale 1: 0.2 mm for A–C, I, 0.1 mm for D, F–H; scale 2:
0.2 mm for E.

The Steninae of Japan Part 3

35

Redescription. Male and female: Body 3.3–3.5 mm (fore body 1.6–1.7 mm) in length. Body
moderately shining; head and abdomen black; pronotum and elytra dark red to dark brown;
labrum reddish brown to dark red or almost black; antennae and legs reddish brown. Body with
punctures small to moderately large, round to elliptical, and also pronotum partially with subrugose punctures and elytra partially with coarse, large punctures. Head shallowly to moderately
concave, with a pair of longitudinal-oblique furrows; antennae moderately long, thin; pronotumwith surface uneven, with a median longitudinal furrow indistinct; elytra with surface uneven;abdomen almost cylindrical to subcylindrical, slightly tapering posteriorly to subparallel-sided;
lateroventrites lost, tergoventral sutures usually lost but sometimes very thin, obscure in rudimentary way.
Male: Abdomen (Fig. 13E) modiﬁed with a small triangular emargination on the 8th ventrite;
9th tergum (Fig. 13A) with ventral apophyses thin, long; 9th ventrite (Fig. 13B) with apicolateral
teeth long, acute, apicolateral setae moderately long; 10th tergum (Fig. 13A) entire. Aedeagal
median lobe (Fig. 13C) subparallel-sided, obtusely angulate at apicolateral corners, pointed witha small apicomedian cusp; apical sclerotized area hardly developed. Endophallus (Fig. 13C) withcopulatory tube (Fig. 13D) long, basal chamber large, main tube with basal tube thick, moderately constricted near the middle, apical tube very thin, attenuate; dorsolateral bands very thin;
explusion hooks (Fig. 13F) separated, each relatively thin, with anterior plate almost rounded atanterior tip; ventralmedian bands relatively short, slightly thin. Parameres (Fig. 13C) eachacutely pointed at apex; apical area short, weakly angulate mesially at base, mesially also with 8
to 9 short setae.
Female: Eighth ventrite (Fig. 13I) minutely pointed posteromedially; gonocoxites (Fig. 13G)
each with apicolateral tooth long, acute, apicolateral setae long. Spermatheca (Fig. 13H) with
capsule small; striped duct moderately long, moderately thick; duct slightly short, thin, loosely
coiled with about 10 turns; gland small, with opening on the lateral side of duct between the last
and last 2nd turns; basal valve very short; basal sclerotized duct very short, truncated-conical inshape.
Biology and ecology. The beetles of S. fujimontis inhabit leaf litter heaped in the natural forests of mountainous to high mountainous regions. They were collected from the low shrub
mainly comprising an alder (Alnus ﬁrma), which spread at the timber line of the Azami-line of
Mt. Fuji. They are not rarely found there.
Remarks. S. fujimontis is a sister species of S. fujiensis, and it is separable from the latter species by the abdominal modiﬁcation of male developed only on the 8th ventrite (Fig. 13E), theaedeagal median lobe narrower, without its apical sclerotized area (Fig. 13C), the copulatory tube
with the demarcation between the basal and apical tubes distinct (Fig. 13C), and the endophallic
expulsion hook thinner (Fig. 13F).
Stenus fujiensis Puthz(Figs. 14A–H, 130 L)
Stenus fujiensis Puthz, 2001: 48; Naomi & Puthz, 2013: 142.
Type material examined. Holotype: ♂ (SMNHS), Subaru-line (2200 m), North side of Mt
Fuji, Shizuoka Pref., 1. viii. 1999, V. Puthz leg. Paratypes: 2 ♂2 ♀, same locality as holotype, 1.
viii. 1999, S. Naomi leg.
Other material examined. [HONSHU]: 1 ♂2 ♀, Shin-5-gôme, Fujinomiya, Shizuoka Pref., 5.

36

Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

Fig. 14. Stenus fujiensis Puthz (Shizuoka: A, B, D, Fujinomiya; Yamanashi: C, E–H, Mt. Fuji). A, spermatheca;
B, 9th and 10th terga of male; C, copulatory tube; D, posterior part of gonocoxite; E, endophallic expulsion
hooks; F, aedeagus; G, 9th ventrite of male; H, 6th, 7th and 8th ventrites of male. Scale 1: 0.05 mm for A;
scale 2: 0.2 mm for B, G, 0.1 mm for C–E; scale 3: 0.2 mm for F; scale 4: 0.3 mm for H.

The Steninae of Japan Part 3

37

xi. 2000, S. Nomura leg.
Distribution. Japan: Honshu (Shizuoka Pref.).
Redescription. Male and female: Body 3.4–3.6 mm (fore body 1.6–1.7 mm) in length. Body
moderately shining; head and abdomen black; pronotum and elytra dark red to dark brown;
labrum dark reddish brown to almost black; antennae and legs reddish brown. Body with punctures small to moderately large, round to ovoidal, and also pronotum partially with subrugose
punctures and elytra partially with large, coarse punctures. Head shallow to moderately concave,with a pair of longitudinal-oblique or almost longitudinal furrows (or depressions); antennae
short, thin; pronotum with surface slightly uneven to uneven, with a median longitudinal furrow
indistinct; elytra with surface uneven; abdomen nearly almost cylindrical, slightly tapering posteriorly to subparallel-sided; lateroventrites and tergoventral sutures lost.
Male: Abdomen (Fig. 14H) modiﬁed with a broad, ﬂat area on the 6th, an elongate, shallow
depression on the 7th, and a triangular emargination on the 8th ventrite; 9th tergum (Fig. 14B)
with ventral apophyses thin, long; 9th ventrite (Fig. 14G) with apicolateral teeth short, acute, apicolateral setae slightly short; 10th tergum (Fig. B) entire. Aedeagal median lobe (Fig. 14F) relatively broad, obtusely angulate at apicolateral corners, obtusely pointed with an apicomedian
cusp; apical sclerotized area broad-subtriangular in shape. Endophallus (Fig. 14F) with copulatory tube (Fig. 14C) moderately long, basal chamber small, main tube with basal tube thick, sinuous, apical tube very thin, attenuate, sometimes slightly swollen at the most apical part; dorsolateral bands very thin; explusion hooks (Fig. 14E) separated, each with anterior plate demarcatedby a suture from posterior plate, and also further divided into 2 small subplates; ventromedianbands each with basal band very broad at posterior margin, narrowing toward anterior tip. Parameres (Fig. 14F) each acutely pointed at apex; apical area short, weakly angulate mesially atbase, mesially also with about 8 setae.
Female: Eighth ventrite (Fig. 14I) pointed posteromedially with a very small cusp; gonocoxites (Fig. 14D) each with apicolateral tooth long, acute, apicolateral setae long. Spermatheca(Fig. 14A) with capsule lost; striped duct long, thick; duct moderately long, thin, loosely coiled
with about 8 turns; basal valve very short; basal sclerotized duct very short, truncated-conical inshape.
Biology and ecology. The beetles of S. fujiensis inhabit leaf litter heaped in the natural forestsof mountainous to high mountainous regions. They are collected from the litter in the mixed forests of birch, alder, etc. which spread at the timber line of the Subaru-line of Mt. Fuji. These beetles are not rare there.
Remarks. S. fujimontis is a sister species of S. fujimontis, and it is separable from the latter
species by the abdominal modiﬁcations of male developed on the 6th to 8th ventrites (Fig. 14H),
the aedeagal median lobe broader, with its apical sclerotized area broad-subtriangular in shape(Fig. 14F), the copulatory tube without its distinct demarcation between the basal and apicaltubes (Fig. 14C), and the endophallic expulsion hook thicker (Fig. 14F).
Stenus gracilior Naomi(Fig. 15A–E)
Stenus gracilior Naomi, 2015: 3.
Type material examined. Holotype: ♂ (CBM), Fudakake, Mts. Tanzawa, Kanagawa Pref., 8.
ix. 2011, T. Watanabe leg. Paratype: 1 ♂ (KUMF), Mt. Ooyama, Mts. Tanzawa, Kanagawa Pref.,38

Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

3. vii. 2006, T. Watanabe leg.
Other material examined. [HONSHU]: 1 ♂, Mt. Ooyama, Mts. Tanzawa, Hadano City,
Kanagawa Pref., 19. x. 2000, S. Nomura leg.
Distribution. Japan: Honshu (Kanagawa Pref.).
Redescription. Male: Body 3.5–3.6 mm (fore body 1.5–1.6 mm) in length. Body moderately
shining; head and abdomen black; pronotum and elytra dark red; labrum dark red; antennae andlegs pale reddish brown to reddish brown. Body with punctures small to moderately large, roundFig. 15. Stenus gracilior Naomi (Kanagawa: Mt. Tanzawa). A, 9th and 10th terga of male; B, aedeagus; C, 9th
ventrite; D, elytra; E, 8th ventrite of male. Scale 1: 0.1 mm for A–C, 0.2 mm for E; scale 2: 0.3 mm for D.

The Steninae of Japan Part 3

39

to elliptical, and elytra also partially with large punctures. Head shallowly concave, with a pair ofmesially-curved furrows; antennae short to moderately long, very thin to thin; pronotum withsurface slightly uneven, with a median longitudinal furrow indistinct; elytra (Fig. 15D) with surface uneven; abdomen almost cylindrical, subparallel-sided; lateroventrites and tergoventrite
sutures lost.
Abdomen modiﬁed with a small ﬂat area on the 7th, and a broad, shallow emargination on
the 8th ventrite (Fig. 15E); 9th tergum (Fig. 15A) with ventral apophyses short; 9th ventrite (Fig.
15C) with macrosetae moderately long, apicolateral teeth very long, acute, apicolateral setae
long; 10th tergum (Fig. 15A) obtusely angulate posteromedially. Aedeagal median lobe (Fig.
15B) slender, widely, moderately rounded and broadest at apicolateral corners, narrowly roundedat apicomedian part; apical sclerotized area covered with small pores. Endophallus (Fig. 15B)
with copulatory tube moderately long, with basal chamber (?) and basal tube together forming aloofah-shaped tube, apical tube very thin, attenuate, weakly curved; dorsolateral bands invisible;
expulsion hooks each elongate; ventromedian bands thin, relatively short. Parameres (Fig. 15B)
very long; apical area very long, weakly swollen mesially at base, mesially also with 5 to 6 setae
at base and 4 to 6 setae in the apical 2/3.
Female: Unknown.
Biology and ecology. The beetles of S. gracilior inhabit leaf litter heaped in the natural forests of a mountainous region.
Remarks. S. gracilior is probably allied to S. fujimontis and S. fujiensis, but it is easily separable from the latter 2 species by the 9th tergum of male with its ventral apophyses short (Fig.
15A), the aedeagal median lobe much slender (Fig. 15B), and the paramere with its apical areamuch longer (Fig. 15B).
Incertae sedis (S. friebi-complex)
Key to the Japanese species of S. friebi-complex
This is a key for a unit of Stenus-species (6 species) beginning with S. etsukoae and almost
adequately diagnosed with the combination of following character conditions: Abdomen with lateroventrites, usually moderately broad to broad; aedeagal median lobe usually rounded (Fig.
20C), almost rounded (Fig. 17E) or pointed (Fig. 16G) at apex; copulatory tube with main tube
usually simple in structure, attenuate (Fig.17E), and modiﬁed if present with thickness at base(Fig. 19D), weak constriction on its way (Fig. 16G), etc.; endophallic expulsion hook well-developed, often with anterior plate almost completely (Fig. 21F) or incompletely (Fig. 18G) divided
antero-posteriorly into 2 subplates; spermatheca with duct usually moderately broad to broad(Fig. 18B), short (Fig. 16F) to moderately long (Fig. 17C).
Distribution: Hokkaido, Honshu (Tohoku and Kanto Districts), Nansei Isls.
1(8)
2(7)
3(4)
4(3)

Male and female: Pronotum and elytra usually yellowish brown to reddish brown.
Male: Aedeagus median lobe narrower, with apical sclerotized area almost ﬂat ventrally;
endophallic expulsion hook simple laterally.
Male: Eighth ventrite posteriorly with a deep, V-shaped emargination (Fig. 16A); endophallic expulsion hook thinner (Fig. 16E) .............................................. S. etsukoae Naomi
Male: Eighth ventrite posteriorly with an arcuate, shallow emargination; endophallic
expulsion hook broader.

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Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

5(6)Male: Aedeagal median lobe broader before apicolateral corners, with apical sclerotizedarea almost rounded apically (Fig. 17E). Female: Spermatheca with duct more strongly
bumpy on the surface (Fig. 17C) ...............................................................S. kazami Naomi
6(5) Male: Aaedeagal median lobe narrower before apicolateral corners, with apical sclerotized area minutely incised at apicomedian part (Fig. 18D). Female: Spermatheca withduct almost smooth or less strongly bumpy on the surface (Fig. 18B).................................
............................................................................................................. S. silvaticulus Naomi
7(2) Male: Aedeagus median lobe broader, with apical sclerotized area ventrally with a barb
(Fig. 19G); endophallic expulsion hook ﬂanked with a lateral ﬂap (Fig. 19H) ....................
..........................................................................................................S. koinobori Hromádka
8(1) Male and female: Pronotum and elytra usually dark reddish brown to dark brown.
9(10) Male: Fourth to 7th ventrites without depression (Fig. 20D); aedeagal median lobe
broader, with apical sclerotized area almost rounded apically (Fig. 20C) ............................
...............................................................................................S. puthziellus Naomi & Puthz
10(9) Male: Fourth to 7th ventrites each with depression (Fig. 21A); aedeagal median lobe
narrower, with apical sclerotized area pointed at apex (Fig. 21C) ....... S. hagoromo Naomi

Stenus etsukoae Naomi(Figs. 16A–G, 131B)
Stenus etsukoae Naomi, 1987: 2; Herman, 2001: 2169; Naomi & Puthz, 2013: 142.
Type material examined. Holotype: ♂ (KUF), Itomuka, Kitami City, Hokkaido, 23. vii. 1986,
S. Nomura leg. Paratypes: 4 ♂2 ♀, same data as holotype; 5 ♂5 ♀, Nissyo Pass, Hokkaido, 2. viii.
1986, S. Nomura leg.; 1 ♂1 ♀, Himenuma, Rishiri Is., Hokkaido, 26. vi. 1986, S. Nomura leg.;1 ♀, same locality, 12. vii. 1977, S. Naomi leg.; 1 ♂, Horoka, Hokkaido, 29. vii. 1986, S. Nomura
leg.
Other material examined. [HOKKAIDO]: 1 ♂1 ♀,Wayside pond near Rausunuma, Hokkaido, 21. viii. 1990, M. Sakai leg.; 3 ♀,Tokachi-Mitsumata, Kamishihoro-cho, Hokkaido, 24.
vii. 2000, S. Arai leg.; 2 ♂3 ♀, Mt. Midori in Mt. Daisetsu, Hokkaido, 14. viii. 2001, M.
Maruyama & H. Sugaya leg.; 1 ♂, Upepesanke, Mt. Daisetsu, Hokkaido, 9. vii. 2002, N. Yasudaleg.
Distribution. Japan: Hokkaido.
Redescription. Male and female: Body 3.0–3.3 mm (fore body 1.5–1.6 mm) in length. Body
moderately shining; head dark brown with clypeofrontal area reddish brown; pronotum and elytra yellowish brown to reddish brown; abdomen reddish brown to dark brown; labrum reddish
brown; antennae and legs yellowish brown to reddish brown. Body with punctures small to moderately large, round to elliptical, and also pronotum partially with coarse punctures and elytra
partially with large punctures. Head shallowly concave, with a pair of broad, longitudinaloblique depressions; antennae short, thin to slightly thick; pronotum with surface uneven, with a
median longitudinal furrow distinct; elytra with surface uneven; abdomen slightly expanded laterally, moderately broad to broad, slightly tapering posteriorly to subparallel-sided; lateroventrites horizontal in position, thin, punctate, tergoventrite sutures distinct.
Male: Abdomen (Fig. 16A) modiﬁed with a ﬂat area on the 5th, a shallow depression on the
6th, a moderately deep depression on the 7th, and a deep, V-shaped emargination on the 8th ven-

The Steninae of Japan Part 3

Fig. 16. Stenus etsukoae Naomi (Hokkaido: A, Upepesanke, B–G, Itomuka). A, 4th to 7th ventrites of male; B,
9th ventrite of male; C, 9th and 10th terga of male; D, gonocoxite; E, endophallic expulsion hooks; F, spermatheca; G, aedeagus. Scale 1: 0.3 mm for A; scale 2: 0.1 mm for B, C; scale 3: 0.1 mm for D–F, 0.2 mm for G.

41

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Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

trite; 9th tergum (Fig. 16C) with ventral apophyses long; 9th ventrite (Fig. 16B) with macrosetae
moderately long, apicolateral teeth short, acute, apicolateral setae moderately long; 10th tergum(Fig. 16C) very shallowly emarginate posteriorly. Aedeagus (Fig. 16G) with median lobe elongate; apical sclerotized area subtriangular, pointed at apex. Endophallus (Fig. 16G) with copulatory tube having basal chamber long, main tube with basal tube thick, apical tube thin, attenuate;
dorsolateral bands very thin; expulsion hooks (Fig. 16E) each with anterior plate narrowing anteriod, pointed at anterior tip; ventromedian bands relatively short, thin. Parameres (Fig. 16G) eachpointed at apex; apical area moderately long, weakly swollen mesially at base, mesially also with
2 long and 8 to 9 short setae.
Female: Eighth ventrite rounded posteriorly; gonocoxites (Fig. 16D) each with apicolateral
tooth short, acute, apicolateral setae short. Spermatheca (Fig. 16F) with capsule elongate,rounded apically; striped duct short, about as long as capsule; duct short, broad, coiled with 2
turns.
Biology and ecology. S. etsukoae is a very common species. The beetles of this species
inhabit leaf litter heaped in the natural forests of lowlands through low mountainous to highmountainous regions. They seem to prefer wet leaf litter heaped near the ponds near or among
forests.
Remarks. S. etsukoae is allied to S. kazami and S. silvaticulus, but it is separable from the latter 2 species by the abdominal modiﬁcations of male developed on the 5th to 8th ventrites (Fig.
16A), the 9th tergum of male with its ventral apophysis longer (Fig. 16C), the aedeagus median
lobe simply pointed at apex (Fig. 16G), the endophallic expulsion hook more slender (Fig. E),
and the spermatheca with its duct shorter, with 2 turns (Fig. 16F).
Etymology. This species is named after the late mother of ﬁrst author, Etsuko Naomi.
Stenus kazami Naomi(Figs. 17A–H, 131C)
Stenus kazami Naomi, 1988a: 80; Herman, 2001: 2245; Naomi & Puthz, 2013: 142.
Stenus imadatei Naomi & Puthz, 1996: 158. New synonym.
Type material examined. Holotype of S. kazami: ♀ (KUF), Kawarabo, Mt. Hayachine, Iwate
Pref., 22–24. vi. 1980, S. Naomi leg. Paratype of S. kazami: 1 ♂, same data as holotype of S.
kazami.
Holotype of S. imadatei: ♀ (SMNHS), Mt. Hayachine, Iwate Pref., 18. vi. 1971, G. Imadateleg.
Other material examined. [HONSHU]: 1 ♂, Tsuta Spa, Aomori Pref., 8. viii. 1964, Y. Shibata
leg.; 1 ♂, Cape Tappi, Aomori Pref., 30. ix. 1992, M. Sakai leg.; 1 ♂, Yagen Spa, Ohta-cho,
Aomori Pref., 5–6. viii. 1992, T. Kishimoto leg.; 1 ♀, Yachi Spa, Aomori Pref., 6. viii. 1964, Y.
Shibata leg.; 1 ♂2 ♀, Mt. Iwaki, Aomori Pref., 29. ix. 1992, M. Sakai leg.; 1 ♂2 ♀, Dakedai,
Fujisato-machi, Akita Pref., 28. viii. 1994, O. Nakamura & Y. Hagino leg.; 1 ♂, Appi highland,
Iwate Pref., 1. x. 1992, S. Nirasawa leg.; 1 ♀, Doai Valley, Marumori-machi, Miyagi Pref., 30. xi.
1995, S. Nomura leg.
Distribution. Japan: Honshu (Tohoku District).
Redescription. Male and female: Body 3.0–3.2 mm (fore body 1.5–1.6 mm) in length. Body
moderately shining; head black, sometimes with median area dark red; pronotum and elytra yellowish brown to reddish brown; abdomen reddish brown to dark reddish brown; labrum reddish

The Steninae of Japan Part 3

Fig. 17. Stenus kazami Naomi (Iwate: A, D, E, G, Appi; Akita: B, Fujisato; Aomori: C, H, Yachi-spa; Iwate: F,
Mt. Hayachine). A, 9th and 10th terga of male; B, 9th ventrite of male; C, spermatheca; D, 8th ventrite ofmale; E, aedeagus; F, apical part of paramere; G, endophallic expulsion hooks; H, posterior part of gonocoxite. Scale 1: 0.1 mm for A, B; scale 2: 0.05 mm for C, G, 0.2 mm for D, 0.1 mm for F, H; scale 3: 0.1 mm for E.

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Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

brown; antennae and legs yellowish brown to reddish brown. Body with punctures small to moderately large, round to elliptical, and also pronotum partially with coarse punctures. Head shallowly concave, with a pair of broad, longitudinal-oblique depressions; antennae short, thin toslightly thick; pronotum with surface uneven, with a median longitudinal furrow very indistinct;
elytra with surface slightly uneven; abdomen slightly expanded laterally, moderately broad tobroad, slightly tapering posteriorly to subparallel-sided; lateroventrites ventromesial in position,
thin, punctate, tergoventrite sutures distinct.
Male: Abdomen (Fig. 17A) modiﬁed with an arcuate, shallow emargination on the 8th ventrite; 9th tergum (Fig. 17A) with ventral apophyses relatively short; 9th ventrite (Fig. 17B) withmacrosetae moderately long, apicolateral teeth short, acute, apicolateral setae long; 10th tergum(Fig. 17A) shallowly emarginate posteromedially. Aedeagus (Fig. E) with median lobe elongate,
almost rounded apically; apical sclerotized area crescent, short. Endophallus (Fig. 17E) with copulatory tube having basal chamber ovoidal, main tube very long, straight, subulate; expulsion
hooks (Fig. 17E, G) each with anterior plate acutely pointed (Fig. 17G) or almost rounded (Fig.
17E) at anterior tip; ventromedian bands short, thin. Parameres (Fig. 17E, F) each simply, acutely
pointed (Fig. 17F) or weakly incurved (Fig. 17E) at apex; apical area short, weakly swollen laterally, mesially with 10 setae.
Female: Eighth ventrite obtuse posteromedially; gonocoxites (Fig. 17H) each with apicolateral tooth short, very acute, apicolateral setae moderately long. Spermatheca (Fig. C) with capsule large, rounded apically; striped duct moderately long, moderately broad to broad; duct moderately long, broad, somewhat bumpy with tubercles of various sizes on the surface, coiled with
8 to 9 turns.
Biology and ecology. The beetles of S. kazami inhabit leaf litter in the natural forests of lowlands near seashores to low mountainous or mountainous regions.
Remarks. S. imadatei was described as new species by Naomi & Puthz (1996) only by one
specimen (as holotype) of female beetle which was collected from Mt. Hayachine, Iwate Pref.,the same holotype locality of S. kazami. S. imadatei Naomi & Puthz, 1996 is here newly placedin synonymy with S. kazami Naomi, 1988a.
S. kazami is allied to S. silvaticulus, but it is separable from the latter species by the aedeagal
median lobe broader and more or less gradually narrowing apical in about apical 1/2 (Fig. 17E),
with its apical sclerotized area shorter and simply rounded apicomedially (Fig. 17E), the copulatory tube longer (Fig. 17E), and the spermatheca with its duct somewhat bumpy with tubercles ofvarious sizes on the surface (Fig. 17C).
Etymology. The speciﬁc epithet of this species is derived from the Japanese term whichmeans the weather vane, kazami.
Stenus silvaticulus Naomi(Figs. 18A–G, 131D)
Stenus silvaticulus Naomi, 1997a: 20; Herman, 2001: 2390; Naomi & Puthz, 2013: 142.
Type material examined. Holotype: ♂ (CBM), Iidate Vil., Fukushima Pref., 20. vii. 1985, S.
Nomura leg. Paratypes: 1 ♂8 ♀, same locality, 20–21. vii. 1985, S. Nomura leg.; 3 ♂4 ♀, Numappara, Mt. Nasu, Tochigi Pref., 4. vi. 1994, S. Naomi leg.
Other material examined. [HONSHU]: 1 ♀, Futamata Spa, Shimogo-machi, Fukushima
Pref., 19. x. 2003, S. Arai leg.

The Steninae of Japan Part 3

Fig. 18. Stenus silvaticulus Naomi (Fukushima: A, B, D–G, Iidate; Tochigi: C, Mt. Nasu). A, posterior part ofgonocoxite; B, spermatheca; C, 9th ventrite of male; D, aedeagus; E, 8th ventrite of male; E, 9th and 10th
terga of male; F, 9th and 10th terga of male; G, endophallic expulsion hooks. Scale 1: 0.1 mm for A, 0.05 mm
for B, G, 0.2 mm for E; scale 2: 0.1 mm for C, F; scale 3: 0.1 mm for D.

45

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Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

Distribution. Japan: Honshu (Fukushima and Tochigi Prefs.).
Redescription. Male and female: Body 3.0–3.3 mm (fore body 1.5–1.6 mm) in length. Body
moderately shining; head black, sometimes with median area reddish brown to dark red; pronotum, elytra and abdomen yellowish brown to reddish brown; labrum reddish brown; antennae
and legs yellowish brown to reddish brown. Body with punctures small to moderately large,
round to ovoidal, and also pronotum partially with coarse punctures and elytra partially withlarge, coarse punctures. Head shallowly concave, with a pair of broad, longitudinal-oblique ormesially-curved furrows (or depressions); antennae short, thin; pronotum with surface slightly
uneven, with a median longitudinal furrow very indistinct; elytra with surface slightly uneven to
uneven; abdomen slightly expanded laterally, slightly tapering posteriorly to subparallel-sided;
lateroventrites ventromesial in position, thin, punctate, tergoventrite sutures distinct.
Male: Abdomen (Fig. 18E) modiﬁed with an arcuate, shallow emargination on the 8th ventrite; 9th tergum (Fig. 18F) with ventral apophyses short; 9th ventrite (Fig. 18C) with macrosetae
long, apicolateral teeth short, acute, apicolateral setae moderately long; 10th tergum (Fig. 18F)
very shallowly emarginate posteriorly. Aedeagus (Fig. 18D) with median lobe elongate, moderately constricted a little before the base of apical sclerotized area; apical sclerotized area almost
semicircular, rounded apically, with a minute apicomedian incision. Endophallus (Fig. 18D) withcopulatory tube having basal chamber elongate-ovoidal in shape, main tube long, straight, subulate; expulsion hooks (Fig. 18G) each with anterior plate more or less pointed at anterior tip; ventromedian bands short. Parameres (Fig. 18D) each acutely pointed at apex; apical area short,
weakly swollen laterally, mesially with 10 to 12 setae of various length.
Female: Eighth ventrite obtuse posteromedially; gonocoxites (Fig. 18A) each with apicolateral tooth slightly short, acute, apicolateral setae long. Spermatheca (Fig. 18B) with capsulelarge, rounded apically; striped duct moderately long, very broad; duct moderately long, moderately broad to broad, almost smooth or partially slightly bumpy with tubercles on the surface,coiled with 8 to 9 turns.
Biology and ecology. The beetles of S. silvaticulus inhabit leaf litter in the natural forests ofmountainous regions.
Remarks. S. silvaticulus is allied to S. kazami, but it is separable from the latter species by
the aedeagal median lobe narrower and moderately constricted a little before the base of apicalsclerotized area (Fig. 18D), with its apical sclerotized area longer and minutely incised apicomedially (Fig. 18D), and the copulatory tube shorter (Fig. 18D), and the spermatheca with its duct
almost smooth or partially slightly bumpy with tubercles on the surface (Fig. 18B).
Stenus koinobori Hromádka(Figs. 19A–H, 131E)
Stenus koinobori Hromádka, 1980: 115; Herman, 2001: 2248; Naomi & Puthz, 2013: 142.
Type material examined. Holotype: ♀ (NHMV), Nakayama Pass, Sapporo City, Hokkaido.
Other material examined. [HOKKAIDO]: 5 ♂5 ♀, Mt. Chisenupuri, Hokkaido, 20. vii. 2000,
S. Nomura leg.; 1 ♂1 ♀, Sapporo Lake, Sapporo City, Hokkaido, 5. ix. 1984, T. Kishimoto leg.;1 ♀,Ohsawaguchi, Nopporo, Hokkaido, 4. v. 2000, H. Sugaya leg.; 3 ♂1 ♀, Mt. Yôtei, Hokkaido,
31. viii. 1994, K. Ishii leg.; 4 ♂3 ♀,Mt. Kariba, Shiribeshi, Hokkaido, 13. vi. 1986, S. Nomura
leg.; 1 ♂, Mt. Eniwa, Hokkaido, 20. vii. 1995, H. Hoshina leg.
Distribution. Japan: Hokkaido.

The Steninae of Japan Part 3

Fig. 19. Stenus koinobori Hromádka (Hokkaido: A, G, Eniwa, B, Mt. Chisenupuri, C, D, H, Sapporo, E, F, Mt.
Kariba). A, 9th and 10th terga of male; B, 6th to 8th ventrites of male; C, 9th ventrite of male; D, aedeagus; E,
spermatheca; F, posterior part of gonocoxite; G, apical part of aedeagus; H, endophallic expulsion hooks.
Scale 1: 0.2 mm for A, D, 0.1 mm for E, F, H; scale 2: 0.3 mm for B; scale 3: 0.1 mm for C; scale 4: 0.2 mm for
G.

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Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

Redescription. Male and female: Body 2.7–3.5 mm (fore body 1.3–1.7 mm) in length. Body
moderately shining; head black, with median or clypeofrontal area yellowish brown to reddish
brown; pronotum, elytra and abdomen reddish brown to brown; labrum yellowish brown to reddish brown; antennae and legs yellowish brown to reddish brown. Body with punctures small tomoderately large, round to elliptical, and also pronotum partially with coarse punctures and elytra partially with large, coarse punctures. Head shallowly to moderately concave, with a pair of
longitudinal-oblique or mesially-curved furrows (or depressions), and sometimes also with a pairof large foveae behind antennal tubercles or near the middle on the lateral parts of interoculararea; antennae short, very thin to thin; pronotum with surface uneven, with a median longitudinalfurrow indistinct; elytra with surface uneven; abdomen slightly expanded laterally, slightly tapering posteriorly to subparallel-sided; lateroventrites almost horizontal in position, thin, punctate,tergoventrite sutures distinct.
Male: Abdomen (Fig. 19B) modiﬁed with a shallow depression on the 6th, a moderately
deep, elongate depression on the 7th, and a nearly V-shaped emargination on the 8th ventrite; 9th
tergum (Fig. 19A) with ventral apophyses long; 9th ventrite (Fig. 19C) with macrosetae very
long, apicolateral teeth short, almost acute, apicolateral setae short to moderately long; 10th tergum (Fig. 19A) entire. Aedeagus (Fig. 19D) with median lobe moderately broad, minutely
pointed with a small apicomedian cusp; apical sclerotized area almost semicircular, rounded apicolaterally, with a small barb at the median part of ventral side (Fig. 19G). Endophallus (Fig.
19D) with copulatory tube short, thick, slightly asymmetrical, with main tube strongly narrowing
apicad behind the middle; expulsion hooks each ﬂanked with a lateral ﬂap (Fig. 19H), anterior
plate incurved and pointed at anteromesial part; ventromedian bands with the fused broad
median band becoming narrower anteriod and the dorsally folded bands widely separated. Parameres (Fig. 19D) each weakly incurved at apical area, pointed at apex; apical area short, mesiallywith 4 short setae at base and 6 short setae near apex.
Female: Eighth ventrite well-rounded posteriorly; gonocoxites (Fig. 19F) each with apicolateral tooth long, very acute, apicolateral setae long. Spermatheca (Fig. 19E) with capsule almost
lost or very short, rounded apically; striped duct short to moderately long; duct thin, loosely
coiled with 3 turns; gland with opening located on the lateral surface of duct between the 2nd
and 3rd turns.
Biology and ecology. The beetles of S. koinobori inhabit leaf litter in the natural forests oflowlands to mountainous regions.
Remarks. S. koinobori is probably allied to S. puthziellus, but it is separable from the latter
species by the body paler in color (Fig. 131E), the aedeagal median lobe with its apical sclerotized area having a ventral barb (Fig. 19G), the endophallic expulsion hook with a lateral ﬂap(Fig. 19H), and the spermatheca shorter and thinner (Fig. 19E).
Etymology. The speciﬁc epithet of this species is derived from the Japanese term whichmeans carp-shaped streamer, koinobori.
Stenus puthziellus Naomi(Figs. 20A–H, 131F)
Stenus puthziellus Naomi, 1997a: 2; Herman, 2001: 2364; Naomi & Puthz, 2013: 142.
Type material examined. Holotype: ♀ (CBM), Mt. Hayachine, Iwate Pref., 17. vii. 1985, S.
Nomura leg. Paratype: 1 ♀, same data as holotype.

The Steninae of Japan Part 3

Fig. 20. Stenus puthziellus Naomi (Miyagi: A, B, D, E, Mt. Zao; Iwate: C, F–H, Mt. Hayachine). A, 9th and 10th
terga of male; B, 9th ventrite of male; C, aedeagus; D, 8th ventrite of male; E, F, spermatheca; G, endophallic
expulsion hooks; H, posterior part of gonocoxite. Scale 1: 0.2 mm for A, D, 0.1 mm for E, H, 0.05 mm for F;
scale 2: 0.1 mm for B, C, 0.05 mm for G.

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Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

Other material examined. [HONSHU]: 2 ♂3 ♀,Summit of Mt. Yakushi in Mt. Hayachine, 3.
vii. 2015, H. Yokozeki leg.; 4 ♀, Mt. Hayachine, Iwate Pref., 2. vii. 2015, I. Matoba leg.; 1 ♂1 ♀,Mt. Karita in Mt. Zaô, Zaô-cho, Miyagi Pref., 11. vi. 2014, H. Yokozeki leg.; 4 ♀, Mt. Zaô, Zaôcho, Miyagi Pref., 11. vi. 2014, T. Matoba leg.
Distribution. Japan: Honshu (Iwate and Miyagi Prefs).
Redescription. Male and female: Body 3.2–3.5 mm (fore body 1.6–1.8 mm) in length. Body
moderately shining; head and abdomen black; pronotum and elytra dark reddish brown to darkbrown; labrum dark red to black; antennae and legs reddish brown to dark brown. Body with
punctures small to moderately large, round to almost round, and also pronotum and elytra partially with coarse or subrugose punctures. Head moderately concave, with a pair of narrow to
broad, longitudinal-oblique furrows or depressions; antennae short, thin; pronotum with surface
uneven, with a median longitudinal furrow indistinct or a central hollow distinct; elytra with surface uneven; abdomen slightly expanded laterally, slightly tapering posteriorly to parallel-sided;
lateroventrites horizontal in position, thin, punctate, tergoventrite sutures distinct.
Male: Abdomen (Fig. 20D) modiﬁed with an arcuate, shallow emargination on the 8th ventrite; 9th tergum (Fig. 20A) with ventral apophyses relatively short; 9th ventrite (Fig. 20B) withmacrosetae long, apicolateral teeth short, acute, apicolateral setae moderately long; 10th tergum(Fig. 20A) rounded posteriorly. Aedeagus (Fig. 20C) with median lobe well-sclerotized, elongate, almost rounded apically; apical sclerotized area almost semicircular, basimedially with alarge, U-shaped emargination. Endophallus (Fig. 20C) with copulatory tube having main tube
long, thick; dorsolateral bands thin; expulsion hooks (Fig. 20G) relatively broad, with posterior
plate truncate posteriorly; ventromedian bands relatively short, moderately broad. Parameres(Fig. 20C) moderately broad, each acutely pointed at apex; apical area relatively short, weakly
swollen mesially at base, mesially also with 7 to 9 setae.
Female: Eighth ventrite obtuse posteromedially; gonocoxites (Fig. 20H) each with apicolateral tooth short, acute, apicolateral setae moderately long. Spermatheca (Fig. 20E, F) with capsule short, rounded apically; striped duct moderately long to long; duct moderately long, moderately broad to broad, coiled with 6 to 9 turns.
Biology and ecology. The beetles of S. puthziellus inhabit leaf litter in the natural forests ofmountainous regions.
Remarks. S. puthziellus is similar to S. koinobori, but it is separable from the latter species by
the body darker in color (Fig. 131F), the aedeagal median lobe with its apical sclerotized area
without a ventral barb (Fig. 20C), the endophallic expulsion hook simple laterally (Fig. 20G),
and the spermatheca longer and thicker (Fig. 20E, F).
Etymology. This species is named after the third author of this paper, Volker Puthz.
Stenus hagoromo Naomi(Figs. 21A–H, 131G)
Stenus hagoromo Naomi, 1988: 38; Herman, 2001: 2211; Naomi & Puthz, 2013: 144.
Type material examined. Holotype: ♂ (KUF), Mt. Omoto, Ishigaki Is., Okinawa Pref., 20. iii.
1978, S. Naomi leg. Paratypes: 1 ♂, Mt. Omoto, Ishigaki Is., Okinawa Pref., 20. iii. 1978, S.
Naomi leg.; 1 ♂4 ♀, same locality, 22. iii. 1984, S. Nomura leg.; 2 ♀, same locality, 9. iv. 1986,
S. Nomura leg.; 2 ♂4 ♀, same locality, 20. iii. 1978, S. Nomura leg.; 4 ♀, Kanpira fall, IriomoteIs., Okinawa Pref., 27. iii. 1984, S. Nomura leg.; 1 ♂1 ♀, Mt. Urabu, Yonaguni Is., Okinawa

The Steninae of Japan Part 3

Fig. 21. Stenus hagoromo Naomi (Okinawa: A–C, E–H, Ishigaki Is., Mt. Omoto, D, Iriomote Is., Komi). A, 4th to
7th ventrites of male; B, 9th and 10th terga of male; C, aedeagus; D, 9th ventrite of male; E, spermatheca; F,
endophallic expulsion hooks; G, right elytra; H, posterior part of gonocoxite. Scale 1: 0.3 mm for A; scale 2:
0.1 mm for B–D; scale 3: 0.1 mm for E, F, H; scale 4: 0.3 mm for G.

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Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

Pref., 6. vi. 1983, S. Imasaka leg.
Other material examined. [NANSEI ISLS.]: 1 ♂1 ♀, Mt. Banna, Ishigaki Is., Okinawa Pref.,26. iii. 1993, I. Matoba leg.; 3 ♂6 ♀, Komi, Iriomote Is., Okinawa Pref., 13–16. iii. 2002, H. Sugaya leg.; 1 ♂, Ohtomi, Iriomote Is., Okinawa Pref., 21. iv. 1993, H. Kojima leg.; 1 ♂2 ♀, Mt. Inbi,
Yonaguni Is., Okinawa Pref., 23. iv. 1993, H. Kojima leg.; 1 ♂2 ♀, Mt. Donan, Yonaguni Is., Okinawa Pref., 17. iii. 1993, S. Nomura leg.
Distribution. Japan: Nansei Isls. (Okinawa Pref.: Ishigaki Is., Iriomote Is., Yonaguni Is.).
Redescription. Male and female: Body 2.8–3.3 mm (fore body 1.4–1.8 mm) in length. Body
moderately shining; head black, sometimes with median or clypeofrontal area reddish brown todark red; pronotum, elytra and abdomen reddish brown to dark reddish brown; labrum dark reddish brown; antennae and legs yellowish brown. Body with punctures small to moderately large,
round to almost round or elliptical, and also pronotum and elytra partially with coarse to subrugose punctures. Head shallowly to moderately concave, with a pair of longitudinal-obliquedepressions, and also with a pair of large foveae behind antennal tubercles; antennae short tomoderately long, thin; pronotum with surface slightly uneven to uneven, with a median longitudinal furrow very indistinct or a median hollow moderately distinct; elytra (Fig. 21G) with surface slightly uneven to uneven; abdomen subcylindrical, slightly tapering posteriorly; lateroventrites lost, tergoventrite sutures distinct.
Male: Abdomen (Fig. 21A) modiﬁed with a semicircle ﬂat area on the 4th, a large, semilunar,
broad, deep depression on the 5th, a broad, very shallow anteromedian depression and a large,
very deep posteromedian depression on the 6th, a very large, moderately deep or deep anteromedian depression and a small, semilunar, transverse, shallow posteromedian depression on the 7th
ventrite, and a very deep V-shaped emargination on the 8th ventrite; 9th tergum (Fig. 21B) withventral apophyses long; 9th ventrite (Fig. 21D) with macrosetae moderately long, apicolateral
teeth short, acute, apicolateral setae moderately long; 10th tergum (Fig. 21B) very shallowly
emarginate posteriorly. Aedeagus (Fig. 21C) with median lobe very slender, elongate; apicalsclerotized area (Fig. 21C) triangular, pointed at apex. Endophallus (Fig. 21C) with copulatory
tube having basal chamber ovoidal, main tube thick, long; expulsion hooks (Fig. 21F) fused at
the posterior 2/3, each with anterior plate almost divided antero-posteriorly into 2 subplates, posterior plate a little broader than anterior one; ventromedian bands moderately long, moderately
broad. Parameres (Fig. 21C) each falcate at apical area, very acicular at the most apical part; apical area very long, mesially with 16 to 18 setae.
Female: Eighth ventrite obtuse posteromedially; gonocoxites (Fig. 21H) each with apicolateral tooth short, acute, apicolateral setae long. Spermatheca (Fig. 21E) with capsule broad,rounded apically; striped duct moderately long, broad to very broad; duct broad, coiled with 7
turns.
Biology and ecology. S. hagoromo is a common species. The beetles of this species inhabit
the leaf litter in the subtropical natural forests of low mountainous regions.
Remarks. S. hagoromo is a sister species of S. perspicabilis Puthz, 2012 from Taiwan, but it
is separable from the latter species by the abdominal lateroventrites lost in the 4th to 6th segments, the aedeagal median lobe with its apical sclerotized area larger (Fig. 21C), and the endophallic expulsion hook thinner (Fig. 21C). S. hagoromo is also separable from the Japanese species of friebi-subgroup by the conspicuous deep emargination of the 5th and 6th ventrites of male(Fig. A).
Etymology. The speciﬁc epithet of this species is derived from the Japanese name of a legendary robe of feathers worn by a celestrial nymph, hagoromo.

The Steninae of Japan Part 3

53

Species group of S. cephalotes Sharp
The cephalotes-group is a very large, speciose group of species in Stenus, which at present
consists of 2 subgroups (cephalotes-subgr. and rufescens-subgr.). This species group is at present
widely distributed in the Oriental (India, Indonesia, Sumatra) and Palaearctic (Nepal, China, Taiwan, Korea and Japan) regions (Naomi, 2006, 2012; Puthz, 2012, 2013, 2018; Tang, et al., 2010,2017; etc.). This group seems to be worthy of considering a species group of Stenus, although no
distinct apomorphic conditions are, as discussed later in detail, found enough for adequately
characterizing the cephalotes-group as a monophyletic group.
Subgrouping of the cephalotes-group
On the basis of S. rufescens as the representative species, the rufescens-group was ﬁrst established, without mentioning which species are classiﬁed in it, by Benick (1925) in his key, inwhich it is separated from the similis-gr., latifrons-gr. and fornicatus-gr. Naomi (2006) studied
the Japanese species of rufescens-group in detail, and he characterized this group by using several characters (including length of body, color of body, abdominal modiﬁcations of male) andestablished 7 subgroups within it.
On the other hand, the cephalotes-group was established by Benick (1942), independently ofthe establishment of the rufescens-group (Puthz, 2008), based on 1 species S. lacrimulus,
although he stated that the phylogenetic relationship of this species to S. cephalotes and S. rufescens is loose. After his study, Puthz (2012) brieﬂy characterized this species group by using theabdominal structures (unmarginated, or marginated with paratergites or tergosternal sutures) andthe form of paraglossae (oval). Naomi (2012) characterized this species group in detail by the useof 4 characters (length of body, color of body, abdominal modiﬁcations of male, shape of aedeagal median lobe) in order to separate it from the asyura-group. Since several groups of species
had been each established only for a small number of Japanese species within the cephalotesgroup in his early papers on the studies of Japanese Stenus, Naomi (2012) also synonymized
these species groups with the cephalotes-group, and the rufescens-group was also synonymized
with the cephalotes-group at that time.
The cephalotes-group and rufescens-group have not hitherto been regarded as monophyletic
groups in the previous studies, owing to the absence of phylogenetically important apomorphies
or synapomorphies for them. However, there seems to be 3 important characters (color of body,
abdominal modiﬁcations of male, shape of aedeagal median lobe) in order for realizing how thespecies of these 2 previously established groups can be classiﬁed. This is because the present
study shows that the peculiar distributions of the plesiomorphic and apomorphic conditions of
the 3 characters observed among the species of these 2 groups, as discussed later in detail, may
play a role as clues for discerning that the more advanced rufescens-group is found, relative tothe more basal cephalotes-group. This suggests that both groups can be at least tentatively established taxonomically.
Therefore, we treated the 2 above-mentioned groups of species as subgroups of the cephalotes-group (sensu lato), namely, cephalotes-subgroup and rufescens-subgroup, based on thedetailed analysis of the 3 taxonomic characters as below. It is concluded here that the cephalotesgroup at present consists of 2 subgroups (cephalotes-subgr. and rufescens-subgr.).

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Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

Analysis of the 3 important characters of the cephalotes-subgr. and rufescens-subgr.
As having been pointed out by Naomi (2006, 2012), the color of body, the abdominal modiﬁcations of male, and the shape and structure of adeagal median lobe are seemingly useful forcharacterizing the subgroups of cephalotes-group, because the extremely diverse conditions arefound in almost all of the other characters among the species of cephalotes-group. We are to here
analyse these 3 characters for each of the cephalotes-subgr. and rufescens-subgr., and determine
which character conditions can be used as clues for diagnosing and thus establishing the cephalotes-group as well as its subgroups (cephalotes-subgr. and rufescens-subgr.).
Although various colorations of body are found among the species of cephalotes-group, thehead tends to be more or less similar in color to the abdomen, while the pronotum tends to be
more or less similar in color to the elytra. Furthermore, the color of pronotum and elytra and thecolor of head and abdomen each show considerable amounts of variations among the species of
cephalotes-group, but the more taxonomically important diﬀerence for separating the cephalotessubgr. from the rufescens-subgr. is found among the species of cephalotes-group, regarding thecolor of pronotum and elytra than the color of head and abdomen. Therefore, as far as the colorof body is concerned, we take up only the color of pronotum and elytra and compare these two
subgroups in terms of the color of pronotum and elytra.
(1). The cephalotes-subgroup
Color of pronotum and elytra. The pronotum and elytra are dark red or show darker colors
than dark red (ranging from dark reddish brown to dark brown or almost black) in the 28 out of
the 40 species of cephalotes-subgr. On the other hand, in the other 12 species, the pronotum andelytra similarly show darker colors in some specimens as in the 28 species, while they also show
paler colors (i.e., reddish brown) in other specimens. Here, the presence of paler color on the
pronotum and elytra seems to be apomorphic.
Abdominal modiﬁcations of male. The 6th to 8th, 7th to 8th, or 8th ventrites are modiﬁedwith the ﬂat area and/or shallow depression in addition to the emargination in the 8th ventrite in
the 32 species. On the other hand, only in the other 8 species, the deeper depression(s) (e.g.,moderately deep or very deep depressions) are found in the 1 or more ventrites (5th to 7th, 6th to
7th, or 7th ventrites) in addition to the emargination in the 8th ventrite. Here, the possessions ofdeeper depressions are considered to be apomorphic.
Aedeagal median lobe. In the 18 species of cephalotes-group, although the aedeagal median
lobe is very often more or less bulbous at the base, it is wholly slender, narrow or moderately
broad only at the base. The median lobe becomes more or less narrower mostly from near the
middle toward the apicolateral corners. The apical sclerotized area of median lobe is semicircularand more or less rounded, or it is triangular to subtriangular (including elongate-subtriangular)
and obtusely to acutely pointed at the apex. On the other hand, the median lobe is moderately
broad to broad in the 20 species. Out of these 20 species, 9 species possess the apical emargination of median lobe, while 1 species possesses the apical truncation of median lobe. The other 2
species show other peculiar conditions. Namely, one (S. inexoratus) has the aedeagal median
lobe with a median longitudinal line on the apical sclerotized area, while the other (S. yoshitomii)
has the aedeagal median lobe without its distinct apicolateral corners. The latter, namely, themoderately broad to broad conditions of median lobe seem to be apomorphic.
When considering the above-mentioned diverse conditions of the 3 characters, no useful apomorphic conditions of characters are found for certain to consider the cephalotes-subgr. to bemonophyletic. However, in order to separate the cephalotes-subgr. from the rufescens-subgr., theThe Steninae of Japan Part 3

55

cephalotes-subgr. may be, though incompletely but eﬀectively, diagnosed by the combination of
apomorphic and plesiomorphic conditions of characters described at the beginning of the cephalotes-subgr. (p. 59).
(2). The rufescens-subgroup
Color of pronotum and elytra. In the 32 species out of the 60 species of rufescens-subgr.,
the pronotum and elytra show more or less dark colors ranging from reddish brown through dark
reddish brown to dark red near black or almost black. On the other hand, in the 27 species, thepronotum and elytra are pale yellowish brown through yellowish brown to reddish orange insome specimens, while they also show darker colors than reddish orange (ranging from reddish
brown through dark reddish brown and dark red to almost black) in other specimens. (Note that
we have no data regarding the color of one species S. maiko, because only one teneral male specimen was able to be examined for this species.) Here, the presence of paler color on the pronotum and elytra seems to be apomorphic.
Abdominal modiﬁcations of male. The 6th to 8th, 7th to 8th, or 8th ventrites are modiﬁedwith the ﬂat area and/or (very) shallow depression in addition to the emargination in the 8th ventrite in the 30 species. On the other hand, various modiﬁcations such as depressions, emarginations, protrusions, etc. are developed on the 3rd to 8th, 4th to 8th, 5th to 8th or 6th to 8th in theother 30 species. Furthermore, the slightly deep depression and also deeper depression(s) than
the former (e.g., moderately deep, very deep depressions) are found on the 6th or 6th to 7th in the
29 species. Here, the possessions of deeper depressions are considered to be apomorphic.
Aedeagal median lobe. In the 13 species of rufescens-subgr., the aedeagal median lobe issimilarly formed as in the cephalotes-subgr. regarding the shape and structure of basal to medianpart, but the apical sclerotized area is triangular to subtriangular (including elongate- or broadsubtriangular, subpentagonal) and acutely to very acutely pointed at the apex, always with a
median longitudinal line on it. On the contrary, the median lobe is moderately broad to broad,and also more or less broad even at the apicolateral corners in other 16 species. And in the other31 species, the median lobes are various in shape and structure as follows: Median lobe very narrow in about apical 1/2 (S. miroku), extremely narrow and awl-shaped in about apical 1/3 (S.
akojagai), lacking its apical sclerotized area (S. tateoitoi), almost rounded at the apex (S. matobai), having a pair of large apicolateral protrusions (S. bifurcatus). The possession of a medianlongitudinal line on the apical sclerotized area of median lobe, and also the moderately broad tobroad conditions of median lobe seem to be apomorphic.
When considering the above-mentioned highly diverse conditions of 3 characters, no usefulapomorphic conditions of characters are also found for certain to consider the rufescens-subgr. to
be monophyletic. However, in order to separate the rufescens-subgr. from the cephalotes-subgr.,
the rufescens-subgr. may be, though more or less incompletely but eﬀectively, diagnosed by the
combination of apomorphic conditions of characters described at the beginning of the rufescenssubgr. (p. 145).
Characterization and diagnosis of the cephalotes-group
During the course of this study, we examined in detail and analyzed a lot of external as wellas internal (i.e., aedeagal and endophallic) characters in addition to the 3 taxonomically important characters as treated above. However, we failed to discover distinct apomorphic conditions
for regarding the whole cephalotes-group as a monophyletic group. However, almost all speciesof this group are more or less easily distinguishable from all of the other species groups of East

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Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

Asia, only by the habitus and color of body (Figs. 131J–L, 132–134, 135A–J) and the structureof Hypostenus-abdomen. Thus, the cephalotes-group, which comprises the cephalotes-subgr. andrufescens-subgr., is tentatively treated taxonomically as a group of species in this paper, whosetaxonomic position must be however rigorously studied in the future by using the modern methods of molecular phylogeny, etc. This group is, though only partially, separable from the presumably most allied species group (satsuki-group, many species of which have Hemistenus-typeabdomen) by the habitus and color of body, the Hypostenus-type abdomen, etc.
Diagnostic characters of the cephalotes-group. Male and female: Legs each with 4th tarsomere strongly bilobed; abdomen almost always not having laterotergites nor tergoventrite sutures(Hypostenus-type). Male: Abdominal ventrites slightly to strongly modiﬁed with the ﬂat areas,
depressions of various depth (shallow to very deep), emarginations, etc. (Figs. 23A, D, 82E, I,
100F, H); 9th ventrite with a pair of more or less pointed apicolateral teeth (Fig. 23H); aedeagal
median lobe various in shape and structure, not having the tricuspidate apex (Figs. 23F, 82B).
Female: Gonocoxite with a more or less pointed apicolateral tooth (Figs. 23H, 82D); spermatheca having basic form (Figs. 23G, 82C).
Japanese fauna and species-units of the cephalotes-group
The cephalotes-group consists of 2 subgroups cephalotes-subgroup (40 species) and rufescens-subgroup (60 species), and thus 100 species in total from Japan. Since no species is distributed in Hokkaido and Nansei Islands, and their distributional range is at present strictly restricted
to Honshu (central Chubu- and Kanto-Districts and western Kinki- and Chugoku-Districts inaddition to Fukushima Pref. located at the southern part of Tohoku District), Shikoku andKyushu. They all are brachypterous species, and each is indigenous to the Japanese Archipelago.
In the present study, the following 3 units of species are treated taxonomically in the cephalotes-subgroup, as units mainly for the purpose of species identiﬁcation: (1) unit of 14 species
beginning from S. alter, (2) unit of 11 species beginning from S. kyotoensis, and (3) unit of 8
species beginning from S. kyotoensis. The other 3 units of species also are treated as the similartaxonomic units in the rufescens-subgroup as follows: (1) unit of 12 species beginning from S.
yoshidai, (2) unit of 28 species beginning from S. matobai, and (3) unit of 19 species beginningfrom S. testaceopiceus.
Since these units of species are more or less adequately diagnosed as done the beginning of
the units by using several characters, they are no doubt supposed not to be polyphyletic. Some of
the units of species seem to be actually considered to be geographical as well as more or lessmorphologically characterized (and thus presumably monophyletic) units. However, several
other units of species seem to be basal (or paraphyletic?), relative to the units of species which
are diagnosed (and also characterized) by a set or a combination of apomorphic conditions ofcharacters. Thus, further studies are anyway needed to rigorously solve the problem as towhether these taxonomic units are monophyletic or not. We recommend that the readers here
notice the limited value of such keys as for the species of the basal species-units.
The species having an aedeagus with the more or less bifurcated or emarginate apex, arefound both in the cephalotes-subgr. (7 species) and in the rufescens-subgr. (1 species). In thepresent study, they are each classiﬁed as incertae sedis in their respective subgroups. The former
7 species is arranged at the end of the descriptive section of cephalotes-subgr., while the latter 1
species is so at the end of the descriptive section of rufescens-subgr.

The Steninae of Japan Part 3

A list of the Japanese species of the cephalotes-group
The cephalotes-subgroup
Unit of species 1
alter Puthz, 2003 Distribution: Japan (Kyushu).
cephalotes Sharp, 1889 Distribution: Japan (Kyushu).
oblongulus Naomi, 1998 Distribution: Japan (Kyushu).
inexoratus Puthz, 1993 Distribution: Japan (Honshu, Shikoku).
yoshitomii Naomi, 2015a Distribution: Japan (Shikoku).
coﬀeatus Naomi, 2012 Distribution: Japan (Shikoku).
ryugu Naomi, 1989b Distribution: Japan (Kyushu).
tsushimamontis Naomi, Nomura & Puthz sp. nov. Distribution: Japan (Kyushu).
akikoae Naomi, 2021 Distribution: Japan (Kyushu).
kaguyahime Naomi, 1990 Distribution: Japan (Kyushu).
otohime Naomi, 1990 Distribution: Japan (Kyushu).
dainichi Puthz, 2001 Distribution: Japan (Honshu).
amagasui Naomi, 2007 Distribution: Japan (Honshu, Shikoku).
ivanloebli Naomi, Nomura & Puthz sp. nov. Distribution: Japan (Honshu).
Unit of species 2
kyotoensis Naomi, Nomura & Puthz sp. nov. Distribution: Japan (Honshu).
jamesashei Naomi, 2012 Distribution: Japan (Honshu).
cinanomontis Naomi & Nomura, 2015 Distribution: Japan (Honshu).
brevispinis Naomi, 2015a Distribution: Japan (Honshu).
incalcaratus Naomi, 2015 Distribution: Japan (Honshu).
inamatus Puthz, 1993 Distribution: Japan (Honshu).
inaestimatus Puthz, 1993 Distribution: Japan (Honshu).
sicyoideus Naomi, Nomura & Puthz sp. nov. Distribution: Japan (Honshu).
keman Naomi, 1990 Distribution: Japan (Honshu).
＝haniwa Hromádka, 1990.
hoshinai Naomi, 2012 Distribution: Japan (Honshu).
regularis Naomi & Y. Watanabe, 2015 Distribution: Japan (Honshu).
Unit of species 3
cohaerens Naomi, Nomura & Puthz sp. nov. Distribution: Japan (Honshu).
warabi Naomi & Nomura, 1990 Distribution: Japan (Honshu).
himiko Naomi, 1989a Distribution: Japan (Honshu).
＝syugen Naomi, 1989 syn. nov.
subulifer Naomi, Nomura & Puthz sp. nov. Distribution: Japan (Honshu).
aoi Naomi & Puthz, 1993 Distribution: Japan (Honshu).
intrarius Naomi & Ito, 2018 Distribution: Japan (Honshu).
shojiroi Naomi, 2021 Distribution: Japan (Honshu).
gloriﬁcus Naomi, Nomura & Puthz sp. nov. Distribution: Japan (Honshu).

57

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Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

Incertae sedis
inaspectus Puthz, 1993 Distribution: Japan (Shikoku).
kochiensis Naomi, Nomura & Puthz sp. nov. Distribution: Japan (Shikoku).
imasakai Naomi, 1989 Distribution: Japan (Kyushu).
cosiciensis Naomi & Hayashi, 2017 Distribution: Japan (Kyushu).
inassuetus Puthz, 1993 Distribution: Japan (Shikoku).
daimio Naomi, 1989 Distribution: Japan (Kyushu).
takashiiellus Naomi, Nomura & Puthz sp. nov. Distribution: Japan (Kyushu).
The rufescens-subgroup
Unit of species 1
yoshidai Naomi, 1997 Distribution: Japan (Shikoku).
hirashimai Naomi, 1989 Distribution: Japan (Kyushu).
yamajii Naomi & Puthz, 1994a Distribution: Japan (Honshu).
gion Naomi & Ito, 2018 Distribution: Japan (Honshu).
inclarescens Puthz, 1993 Distribution: Japan (Honshu).
fulvidus Naomi, Nomura & Puthz sp. nov. Distribution: Japan (Honshu).
notomontis Naomi, Nomura & Puthz sp. nov. Distribution: Japan (Honshu).
obtusus Naomi, Nomura & Puthz sp. nov. Distribution: Japan (Honshu).
snodgrassi Naomi, 2021 Distribution: Japan (Honshu).
coiﬀaitiellus Naomi & Puthz, 1993 Distribution: Japan (Honshu).
productus Naomi, 2007 Distribution: Japan (Honshu).
maiko Naomi & Puthz, 1993 Distribution: Japan (Honshu).
Unit of species 2
matobai Naomi, 2012 Distribution: Japan (Honshu).
kagura Naomi & Puthz, 1993 Distribution: Japan (Honshu).
toshiharui Naomi, 1990 Distribution: Japan (Kyushu).
akome Naomi, 1989 Distribution: Japan (Honshu, Kyushu).
incumbens Naomi & Y. Watanabe, 2015 Distribution: Japan (Honshu).
amida Naomi, 1989 Distribution: Japan (Shikoku).
pediculifer Naomi & Nomura, 2015 Distribution: Japan (Shikoku).
yoshidaiellus Naomi, Nomura & Puthz sp. nov. Distribution: Japan (Shikoku).
rufescens Sharp, 1874 Distribution: Japan (Honshu).
acutatus Naomi, 2012 Distribution: Japan (Honshu).
ichikawai Naomi, 2006 Distribution: Japan (Honshu).
jukata Hromádka, 1982 Distribution: Japan (Honshu).
ferus Naomi, 2012 Distribution: Japan (Honshu).
deltoides Naomi, Nomura & Kamezawa, 2015 Distribution: Japan (Honshu).
ohtoensis Naomi, 2006 Distribution: Japan (Honshu).
cygnipenis Puthz, 2001 Distribution: Japan (Honshu).
agrestis Naomi, 2006 Distribution: Japan (Honshu).
olliformis Naomi, 2006 Distribution: Japan (Honshu).
＝olliformis owasenus Naomi, 2006 syn. nov.
ebisu Naomi, 2006 Distribution: Japan (Honshu).

The Steninae of Japan Part 359

wasabi Hromádka, 1982 Distribution: Japan (Honshu).
daigonis Naomi & Puthz, 1993 Distribution: Japan (Honshu).
ingens Naomi, 2006 Distribution: Japan (Honshu).
＝ingens ryugatakensis Naomi, 2006 syn. nov.
lubomiri Naomi, 2006 Distribution: Japan (Honshu).
ichihashii Naomi Distribution: Japan (Honshu).
＝ichihashii miunensis Naomi, 2006 syn. nov.
mikawanis Naomi, 1997b Distribution: Japan (Honshu).
gyrosus Naomi, 2006 Distribution: Japan (Honshu).
nakanei Hromádka, 1982 Distribution: Japan (Honshu).
＝ignolabilis Naomi, 1997b.
awajinis Naomi stat. nov. Distribution: Japan (Honshu).
Unit of species 3
testaceopiceus Bernhauer, 1938 Distribution: Japan (Honshu).
pubicornis Naomi, 1998a Distribution: Japan (Honshu).
volkeri Naomi, 1998a Distribution: Japan (Honshu).
okiensis Naomi & Shimada, 2008 Distribution: Japan (Honshu).
tsurusakii Naomi, 1998 Distribution: Japan (Honshu).
akojagai Hromádka, 1982 Distribution: Japan (Honshu).
miroku Naomi, 2006 Distribution: Japan (Honshu).
masatakai Naomi & Nomura, 1990 Distribution: Japan (Honshu).
gagyumontis Naomi, 1990a Distribution: Japan (Honshu).
incurvatus Naomi & Nomura, 2015 Distribution: Japan (Honshu, Shikoku).
okamotoi Naomi, 1989a Distribution: Japan (Honshu, Shikoku).
amma Naomi & Nomura, 1990 Distribution: Japan (Honshu, Shikoku).
enma Naomi, 1990a Distribution: Japan (Honshu).
uenoi Naomi & Nomura, 1990 Distribution: Japan (Honshu, Shikoku).
expansus Naomi & Ito, 2018 Distribution: Japan (Honshu).
masaakii Naomi & Nomura, 2015 Distribution: Japan (Honshu).
bosatsu Naomi, 1989 Distribution: Japan (Honshu).
usitatus Naomi & Nomura, 2015 Distribution: Japan (Honshu).
tateoitoi Naomi, Nomura & Puthz sp. nov. Distribution: Japan (Honshu).
Incertae sedis
bifurcatus Naomi, 2011 Distribution: Japan (Honshu).
The cephalotes-subgroup
Diagnostic characters of the cephalotes-subgroup: Male and female: Pronotum and elytra
often dark red through dark reddish brown to dark brown or almost black (Fig. 131J); abdominal
ventrites of male usually modiﬁed only with ﬂat area and/or shallow depressions (Fig. 23A, D).
Male: Aedeagal median lobe wholly slender (Fig. 28D), narrow (Fig. 23F) or moderately broad
only at base (Fig. 38A), and becoming more or less narrower mostly from near the middle
toward apicolateral corners (Fig. 23F), with apical sclerotized area almost rounded (Fig. 27J), triangular or subtriangular without a median longitudinal line (Fig. 23F), otherwise median lobe

60

Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

moderately broad to broad (Fig. 48A), often with an apical emargination (Figs. 48A, 60C) or anapical truncation (Fig. 54D).

Species unit 1 of the cephalotes-subgroup
Key to the Japanese species of the cephalotes-subgroup (1)This is a key for a unit of Stenus-species (14 species) beginning with S. alter and almost adequately diagnosed with the combination of following character conditions: Abdominal ventrites
of male slightly modiﬁed mainly with the ﬂat area (Fig. 23A), shallower depression (Fig. 25A),
shallower emargination (Fig. 23D); aedeagal median lobe becoming more or less narrower
apicad almost behind the middle, with apical sclerotized area nearly triangular to triangular (Fig.
23F); copulatory tube with main tube almost straight, more or less thick at base, and attenuate,
and not modiﬁed or only slightly modiﬁed into a curved tube (Fig. 35C), a subrhombic tube (Fig.
23B), etc.
Distribution: Honshu (Kinki and Chugoku Districts), Shikoku and Kyushu.
1(24) Male: Aedeagal median lobe less slender, especially in the posterior 1/2. Female: Spermatheca with duct not having apical chamber.
2(21) Male: Aedeagal median lobe narrower at apicolateral corners, with apical sclerotized area
developed, more or less triangular or almost semicircular.
3(20) Male: Aedeagal median lobe with apicolateral corners more or less developed.
4(7) Male: Copulatory tube with main tube elongate-subrhombic in shape.
5(6) Male: Aedeagal median lobe with apical sclerotized area almost semicircular or broad-triangular in shape (Fig. 22F). Female: Spermatheca with basal duct moderately thick, andbecoming thicker proximad (Fig. 22D) .......................................................... S. alter Puthz
6(5) Male: Aedeagal median lobe with apical sclerotized area subtriangular (Fig. 23F).
Female: Spermatheca with basal duct thin, and not becoming thicker proximad (Fig. 23G)................................................................................................................S. cephalotes Sharp
7(4) Male: Copulatory tube with main tube not rhombic nor subrhombic.
8(11) Male: Aedeagal median lobe more slender.
9(10) Male: Copulatory tube with basal tube (fused with basal chamber?) elongate-rectangularin shape (Fig. 28E); endophallic expulsion hook broader, with posterior plate fan-shaped
posteriorly (Fig. 28F, I, J) ............................................................................S. ryugu Naomi
10(9) Male: Copulatory tube with basal tube subrhombic in shape (Fig. 30A); endophallic
expulsion hook narrower, with posterior plate rod-like (Fig. 30F, I, J) ...S. akikoae Naomi
11(8) Male: Aedeagal median lobe less slender.
12(15) Male: Endophallic expulsion hook with posterior plate slightly hollowed mesially.
Female: Spermatheca with duct having a fusiform or nearly fusiform apical chamber.
13(14) Male: Aedeagal median lobe with apical sclerotized area broader than long, and lacking a
median longitudinal line (Fig. 24F); endophallic expulsion hook with lateral surface
smooth (Fig. 24H) ............................................................................... S. oblongulus Naomi
14(13) Male: Aedeagal median lobe with apical sclerotized area longer than broad, and having a
median longitudinal line (Fig. 25J); endophallic expulsion hook laterally covered withvery minute, pointed tubercles (Fig. 25E) ............................................. S. inexoratus Puthz

The Steninae of Japan Part 3

61

15(12) Male: Endophallic expulsion hook with posterior plate solid mesially. Female: Spermatheca with duct lacking apical chamber.
16(17) Male: Ninth tergum with ventral apophysis thicker (Fig. 34A); endophallic expulsion
hook with posterior plate atrophied into a much narrower plate (Fig. 34G) ........................
................................................................................................................S. amagasui Naomi
17(16) Male: Ninth tergum with ventral apophysis thinner; endophallic expulsion hook with posterior plate well-developed to be a much broader plate.
18(19) Male: Copulatory tube with main tube straight (Fig. 29D); endophallic expulsion hookwith posterior plate narrower (Fig. 29F, G, I) .......................................................................
...........................................................S. tsushimamontis Naomi, Nomura & Puthz sp. nov.
19(18) Male: Copulatory tube with main tube slightly (Fig. 33F) or moderately (Fig. 33C)
curved behind the middle; endophallic expulsion hook with posterior plate broader (Fig.
33H) ...........................................................................................................S. dainichi Puthz
20(3) Male: Aedeagal median lobe without apicolateral corners (Fig. 26D) .................................
..............................................................................................................S. yoshitomii Naomi21(2) Male: Aedeagal median lobe broader at apicolateral corners, with apical sclerotized area
hardly developed.
22(23) Male: Aedeagal median lobe rounded at apicolateral corners (Fig. 27J, K); copulatory
with main tube straight (Fig. 27J, K) ......................................................S. coﬀeatus Naomi
23(22) Male: Aedeagal median lobe obtusely angulate at apicolateral corners (Fig. 35C); copulatory with main tube moderately curved behind the middle (Fig. 35C) .................................
....................................................................S. ivanloebli Naomi, Nomura & Puthz sp. nov.
24(1) Male: Aedeagal median lobe more slender, especially in the posterior 1/2. Female: Spermatheca with duct having a large apical chamber.
25(26) Male: Aedeagal median lobe less slender, and very slightly rounded laterally (Fig. 31H).
Female: Spermatheca with duct having a mesially swollen apical chamber (Fig. 31G) .....
............................................................................................................S. kaguyahime Naomi
26(25) Male: Aedeagal median lobe more slender, and almost straight laterally (Fig. 32D).
Female: Spermatheca with duct having a subfusiform apical chamber (Fig. 32C) ..............
................................................................................................................. S. otohime Naomi
Stenus alter Puthz(Fig. 22A–H)
Stenus micuba Hromádka, 1982: 134 (in part).
Stenus alter Puthz, 2003: 15; Naomi & Puthz, 2013: 143.
Type material examined. Holotype: ♂ (paratype of S. micuba; NHMG), Shimabara, Unzen,
Nagasaki Pref., 2. ix. 1934, Suenson leg.
Other material examined. [KYUSHU]: 2 ♂, Mt. Tara, Nagasaki Pref., 13. iv. 1982, S. Imasaka
leg.; 2 ♂, Mt. Iwaya, Nagasaki Pref., 29. v. 1987, S. Nomura leg.; 1 ♂2 ♀, Mt. Inasa, Nagasaki City,
Nagasaki Pref., 26. xi 1990, S. Nomura leg.; 1 ♂1 ♀, Todoroki Valley, Nagasaki Pref., 1. vi. 1987,
S. Nomura leg.; 2 ♂, Tanoo, Oomura City, Nagasaki Pref., 15. iii. 1994, S. Imasaka leg.; 1 ♂1 ♀,Mt. Unzen, Nagasaki Pref., 17. v. 1986, T. Ito leg.; 2 ♂3 ♀, Sanohara, Nakadoori Is., Nagasaki
Pref., 29. iv. 1972, S. Kinoshita leg.; 5 ♂3 ♀, Mt. Tanna, Nakadoori Is., Nagasaki Pref., 16. viii.
1977, M. Ohishi leg.; 2 ♂1 ♀, Kashibaru, Saga Pref., 10. x. 1976, H. Ohishi leg.; 2 ♂, Mt. Tara,62

Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

Fig. 22. Stenus alter Puthz (Nagasaki: A–B, E–H, Mt. Unzen, C, D, Todoroki Valley). A, 6th to 8th ventrites ofmale; B, endophallic expulsion hooks; C, gonocoxite; D, spermatheca; E, 9th and 10th terga of male; F,aedeagus; G, copulatory tube; H, 9th ventrite of male. Scale 1: 0.25 mm for A; scale 2: 0.1 mm for B–D, G,
0.2 mm for F, H; scale 3: 0.1 mm for E.

The Steninae of Japan Part 3

63

Saga Pref., 14. iv. 1985, S. Nomura leg.; 1 ♂1 ♀, Mt. Kyogatake, Saga Pref., 6. vi. 1983, S.
Nomura leg.; 4 ♂11 ♀, Mt. Kokuzô, Ureshino-machi, Saga Pref., 1. x. 1997, S. Nomura leg.
Distribution. Japan: Kyushu (Nagasaki and Saga Prefs.).
Redescription. Male and female: Body 2.8–3.2 mm (fore body 1.5–1.9 mm) in length. Body
moderately to strongly shining; head black, sometimes with median area dark red; pronotum,
elytra and abdomen reddish brown to dark red or dark reddish brown; labrum reddish brown todark reddish brown; antennae and legs yellowish brown to reddish brown. Body with puncturesround to ovoidal, small to moderately large, and also promotum partially with coarse puncturesand elytra partially with large punctures. Head shallowly to moderately concave, with a pair of
longitudinal-oblique furrows; antennae short to moderately long, very thin; pronotum with surface slightly uneven, with a median longitudinal furrow indistinct; elytra with surface even toslightly uneven; abdomen subcylindrical, thin to moderately thick, slightly tapering posteriorly to
subparallel-sided; lateroventrites and tergoventrite sutures lost.
Male: Abdomen (Fig. 22A) modiﬁed with an almost ﬂat area on the 7th, and a very shallow
emargination on the 8th ventrite; 9th tergum (Fig. 22E) with ventral apophyses moderately long;
9th ventrite (Fig. 22H) with macrosetae long, apicolateral teeth short, very acute, apicolateral
setae moderately long; 10th tergum (Fig. 22E) very shallowly emarginate posteriorly. Aedeagus(Fig. 22F) with median lobe slender, well-rounded at apicolateral corners, minutely pointed or
obtuse at apex; apical sclerotized area almost semicircular or broad-subtriangular in shape,
basally with an arcuate notch. Endophallus with copulatory tube (Fig. 22G) with basal chambercomprising 2 rods of equal length, main tube almost elongate-subrhombic in shape, acutely
pointed at apex; expulsion hooks (Fig. 22B) each with anterior plate minutely incurved atanteromesial corner; ventromedian bands short, moderately broad. Parameres (Fig. 22F) eachacutely pointed at apex; apical area long, moderately broad, mesially with 8 to 9 setae.
Female: Eighth ventrite obtuse posteromedially; gonocoxites (Fig. 22C) each with apicolateral tooth very long, very acute, apicolateral setae very long. Spermatheca (Fig. 22D) with capsule moderately large, rounded apically; striped duct long, thick; duct very long, thin to moderately thick, strongly coiled; basal valve very short; basal duct moderately long, moderately thick,becoming thicker proximad.
Biology and ecology. S. alter is a common species. The beetles of this species inhabit leaf litter heaped in the natural forests of lowlands to mountainous regions.
Remarks. S. micuba was ﬁrst newly described by Hromádka (1982), based on the specimensof Stenus-beetles collected from Japan (Shimabara, Nagasaki Pref.) and China (Chinkiang). After
that, Puthz (2003) described S. alter as new, based on several specimens from Kyushu, and hedesignated a male paratype (Shimabara) of S. micuba, as the holotype of S. alter. S. alter and S.
micuba are thus distributed in Japan (Kyushu) and China (Chinkiang), respectively, resulting inmaking S. ater be indigenous in Japan.
S. alter is very closely allied to S. cephalotes, but it is separable from the latter species by theaedeagal median lobe with its apical sclerotized area shorter, and almost semicircular or broadsubtriangular in shape (Fig. 22F). There are certainly variations regarding the structures of endophallic expulsion hooks and aedeagal parameres among these two species, but in S. alter the
expulsion hook is usually shorter (Fig. 22B), and the apical area of paramere also seems to be
shorter (Fig. 22F). S. alter is also allied to S. micuba from China, but it is separable from the latter by the expulsion hook with its apical plate much larger (Fig. 22F).

64

Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

Stenus cephalotes Sharp(Figs. 23A–J, 130J)
Stenus cephalotes Sharp, 1889: 331; Herman, 2001: 2118; Naomi & Puthz, 2013: 143.
Stenus nagasakianus Bernhauer, 1936: 239.
Type material examined. The lectotype of S. cephalotes Sharp (♂, NHML) is herein designated with the labels written as follows: Stenus cephalotes Japan Lewis. Labels: Syntype; Japan
Lewis; Sharp coll.; BM loan No. 8319; male-LEKTOTYPUS Puthz; Stenus cephalotes Sharp
vid. Puthz 1968. (Note that the specimen designated as the lectotype lacks the left antenna.) Paralectotypes of S. cephalotes Sharp: 2 ♀, Nagasaki; 1 ex., with the abdomen missing; 4 ♂ 6 ♀ (several specimens are placed together on the same plate), Nagasaki 26. 3. 81; 1 ♂, Nagasaki 13. II.–
21. IV. 81 (cP).
Holotype of S. nagasakianus: Holotype of S. nagasakianus is deposited in NHML (Puthz,1967) and FMC.
Other material examined. [KYUSHU]: 1 ♂2 ♀, Mt. Yasuman, Hirado Is., Nagasaki Pref., 15.
xi. 1986, S. Nomura leg.; 1 ♂, Mt. Shishiki, Hirado Is., Nagasaki Pref., 7. x. 1997, S. Nomura
leg.; 1 ♂1 ♀, Nomozaki, Nagasaki Pref., 18. xii. 1977, S. Imasaka leg.
Distribution. Japan: Kyushu (Nagasaki Pref.).
Redescription. Male and female: Body 3.0–3.3 mm (fore body 1.5–1.7 mm) in length. Body
moderately shining; head black, sometimes with median area dark reddish brown; pronotum, elytra and abdomen dark red; labrum reddish brown; antennae and legs yellowish brown to pale reddish brown. Body with punctures round to ovoidal, small to moderately large, and also pronotum
partially with coarse punctures and elytra partially with large, subrugose punctures. Head moderately concave, with a pair of longitudinal-oblique or longitudinal furrows; antennae short to moderately long, very thin; pronotum with surface slightly uneven to uneven, with a median longitudinal furrow very indistinct to indistinct; elytra with surface slightly uneven to uneven; abdomensubcylindrical, thin to moderately thick, slightly tapering posteriorly to subparallel-sided; lateroventrites and tergoventral sutures lost.
Male: Abdomen modiﬁed with an elongate, ﬂat area on the 7th (Fig. 23A), and a very shallow, arcuate emargination on the 8th ventrite (Fig. 23D); 9th tergum (Fig. 23J) with ventral
apophyses moderately long; 9th ventrite (Fig. 23E) with macrosetae long, apicolateral teeth
slightly short, acute, apicolateral setae long; 10th tergum (Fig. 23J) very shallowly emarginate
posteriorly. Aedeagus (Fig. 23F) with median lobe elongate, weakly angulate (Fig. 23F) or
rounded at apicolateral corners, obtusely pointed at apex; apical sclerotized area elongate-subtriangular in shape, basally with a shallow notch. Endophallus (Fig. 23F) with copulatory tube (Fig.
23B) with basal chamber long, comprising 2 thin rods of diﬀerent length, main tube elongatesubrhombic in shape, acutely pointed at apex; expulsion hooks (Fig. 23I) elongate, each withanterior plate pointed or minutely incurved at anterior tip; ventromedian bands short, narrow.
Parameres (Fig. 23F) long, moderately thick, each pointed at apex; apical area very long, weakly
curved, mesially with 9 setae of various length.
Female: Eighth ventrite (Fig. 23C) almost rounded posteriorly or obtuse posteromedially;
gonocoxites (Fig. 23H) each with apicolateral tooth long, acute, apicolateral setae very long.
Spermatheca (Fig. 23G) with capsule large, moderately long; striped duct moderately long, thick;duct very long, thin to moderately thick, strongly coiled; basal valve short; basal duct short, withan arrowhead-like structure at proximal part.

The Steninae of Japan Part 3

Fig. 23. Stenus cephalotes Sharp (Nagasaki: Nomozaki). A, 7th ventrite; B, copulatory tube; C, posterior part of
8th ventrite of female; D, posterior part of 8th ventrite of male; E, 9th ventrite of male; F, aedeagus; G, spermatheca; H, gonocoxite; I, endophallic expulsion hooks; J, 9th and 10th terga of male. Scale 1: 0.25 mm for A;
scale 2: 0.1 mm for B, G–I, 0.2 mm for E, F; scale 3: 0.25 mm for C, D; scale 4: 0.2 mm for J.

65

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Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

Biology and ecology. The beetles of S. cephalotes inhabit leaf litter heaped in the natural forests of lowlands to low mountainous regions.
Remarks. S. cephalotes is the representative species of the cephalotes-group. S. cephalotes isclosely allied to S. alter, but it is separable from the latter species by the aedeagal median lobe
with its apical sclerotized area longer and elongate-subtriangular in shape (Fig. 23F), the endophallic expulsion hook usually longer (Fig. 23I), and the paramere with its apical area longer(Fig. 23F).
Stenus oblongulus Naomi(Figs. 24A–H, 131K)
Stenus oblongulus Naomi, 1998: 99; Herman, 2001: 2309; Naomi & Puthz, 2013: 143.
Type material examined. Holotype, ♂ (CBM), Miike, Mt. Kirishima, Kagoshima Pref., 8. v.
1985, S. Nomura leg. Paratypes: 2 ♂2 ♀, same data as holotype.
Other material examined. [KYUSHU]: 1 ♂, Koike, Miyazaki Pref., 15. viii. 1984, K. Andoleg.; 3 ♂3 ♀, Mt. Wanizuka, Tano-cho, Miyazaki Pref., 6. ix. 1993, S. Nomura leg.; 3 ♂3 ♀, Inohae Valley, Hokugô-cho, Miyazaki Pref., 27. iv. 1993, S. Nomura leg.; 4 ♂7 ♀, Asajinno, Tano,
Miyazaki Pref., 7. v. 2017, T. Watanabe leg.; 1 ♂, Kawanaka Shrine, Aya, Miyazaki Pref., 8. v.
2017, T. Watanabe leg.
Distribution. Japan: Kyushu (Miyazaki and Kagoshima Prefs.).
Redescription. Male and female: Body 3.2–4.3 mm (1.6–2.0 mm) in length. Body moderately
shining; head and abdomen dark red to black; pronotum and elytra dark red to dark red near
black; body sometimes almost entirely reddish brown; labrum reddish brown to dark brown;
antennae and legs yellowish brown to reddish brown. Body with punctures round to ovoidal or
elliptical, small to moderately large, and also pronotum partially with coarse punctures and elytra
partially with large, coarse to subrugose punctures. Head moderately concave, with a pair of longitudinal-oblique furrows; antennae short to moderately long, very thin; pronotum with surface
slightly uneven, with a median longitudinal furrow or a hollow indistinct; elytra with surface
slightly uneven to uneven; abdomen subcylindrical, slightly tapering posteriorly to subparallelsided; lateroventrites and tergoventrite sutures lost.
Male: Abdomen (Fig. 24C) modiﬁed with a semicircular ﬂat area on the 7th, and a moderately deep emargination on the 8th ventrite (Fig. 24C); 9th tergum (Fig. 24A) with ventral apophyses moderately long; 9th ventrite (Fig. 24B) with macrosetae long to very long, apicolateral
teeth long, very acute, apicolateral setae very long; 10th tergum (Fig. 24A) entire. Aedeagus (Fig.
24F) with median lobe elongate, obtuse at apicolateral corners, obtusely pointed at apex; apicalsclerotized area subtriangular, basally with an arcuate notch. Endophallus (Fig. 24D) with copulatory tube having basal chamber elongate-ovoidal in shape (Fig. 24D), main tube simple, attenuate; dorsolateral bands thin; expulsion hooks (Fig. 24H) moderately large, each with anterior
plate fused with posterior plate, narrowing anteriod, acutely pointed at anterior tip, posterior
plate well-rounded laterally, slightly hollowed mesially; ventromedian bands relatively short,thin. Parameres (Fig. 24F) slender, thin, each pointed at apex; apical area hardly or weakly swollen laterally, mesially with 11 to 14 setae.
Female: Eighth ventrite obtuse or minutely pointed posteromedially; gonocoxites (Fig. 24G)
each with apicolateral tooth moderately long, very acute, apicolateral setae very long. Spermatheca (Fig. 24E) with capsule subovoidal, moderately large; striped duct very short; duct moder-

The Steninae of Japan Part 3

Fig. 24. Stenus oblongulus Naomi (Kagoshima: A–B, D–H, Mt. Kirishima; Miyazaki: C, Mt. Wanizuka). A, 9th
and 10th terga of male; B, 9th ventrite of male; C, 7th to 8th ventrites of male; D, copulatory tube; E, spermatheca; F, aedeagus; G, gonocoxite; H, endophallic expulsion hooks. Scale 1: 0.1 mm for A, B, F; scale 2:0.25 mm for C; scale 3: 0.1 mm for D, E, G, H.

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Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

ately long, moderately thick, loosely coiled with 6 turns, and also with a large, fusiform apicalchamber; gland spherical, small, with opening situated on the lateral side of duct between the 1st
and 2nd turns; basal valve very short; basal duct sclerotized, moderately thick.
Biology and ecology. The beetles of S. oblongulus inhabit leaf litter heaped in the natural forests of mountainous regions.
Remarks. S. oblongulus is allied to S. inexoratus, but it is separable from the latter species by
the 7th ventrite of male posteromedially with a semicircular ﬂat area (Fig. 24C), the aedeagal
median lobe a little broader, with its apical sclerotized area shorter and broader (Fig. 24F), andthe endophallic expulsion hook broader, with its posterior plate well-rounded laterally andsmooth (Fig. 24H).
S. oblongulus shows variations regarding the structures of aedeagus and its endophallus.
First, the apical sclerotized area of median lobe is varied in shape as follows: Broad-subtriangular to narrow-triangular, and gently rounded to acutely pointed at apex. Second, the endophallic
expulsion hook is varied in structure, especially in length. In some cases it is similar in shape tothe expulsion hook of S. inexoratus to some extent. However, since these two species are usually
distinct regarding some important characters as described above, these variations are here considered to be infraspeciﬁc.
Stenus inexoratus Puthz(Figs. 25A–J, 131 L)
Stenus inexoratus Puthz, 1993: 155; Herman, 2001: 2231; Naomi & Puthz, 2013: 143.
Type material examined. Holotype: ♂ (NHMG), Mt. Ishizuchi (1,400 m), Ehime Pref.,13–14. viii. 1980, Cl. Besuchet leg.
Other material examined. [HONSHU]: 1 ♂, Nikyûkyo, Hiroshima Pref., 5. iv. 1986, I. Okamoto leg.; 1 ♂, Mukobara-cho, Hiroshima Pref., 18. ix. 1986, I. Okamoto leg.; 1 ♂2 ♀, Hoei-cho,
Hiroshima Pref., 4. vii. 1986, I. Okamoto leg.; 2 ♂, Haigamine, Kure City, Hiroshima Pref., 12.
iv. 1986, I. Okamoto leg.; 1 ♂3 ♀, Yasaka Valley, Miwa-cho, Yamaguchi Pref., 11. xi. 1998, S.
Nomura leg.; 2 ♂2 ♀, Gomandô Valley, Kano-cho, Yamaguchi Pref., 12. xi. 1998, S. Nomura leg.
[SHIKOKU]: 2 ♂2 ♀, Mt. Saragamine, Ehime Pref., 29. v. 1993, Lizhen Li leg.; 2 ♂1 ♀, Ryujindaira, Mt. Saragamine, Ehime Pref., 20. xi. 1993, M. Sakai leg.; 1 ♂, Sugitate, Matsuyama City,
Ehime Pref., 26. xi. 1968, M. Sakai leg.; 4 ♂, Mt. Takanawa, Hokujyo City, Ehime Pref., 8. v.
1993, N. Tsurusaki leg.
Distribution. Japan: Honshu (Hiroshima and Yamaguchi Prefs.) and Shikoku (Ehime Pref.).
Redescription. Male and female: Body 2.8–4.0 mm (Fore body 1.5–1.9 mm) in length. Body
moderately shining; head black, sometimes with clypeofrontal area dark red, pronotum and elytra
dark red, abdomen dark red to almost black; and also body sometimes almost entirely reddish
brown; labrum reddish brown to dark brown; antennae and legs yellowish brown to reddish
brown. Body with punctures round to ovoidal, small to moderately large, and also pronotum partially with coarse punctures and elytra partially with large, coarse punctures. Head moderately
concave, with a pair of longitudinal-oblique furrows; antennae short to long, very thin; pronotumwith surface slightly uneven to uneven, with a median longitudinal furrow indistinct; elytra withsurface slightly uneven to uneven; abdomen subcylindrical, slightly tapering posteriorly to subparallel-sided; lateroventrites lost, tergoventral sutures lost but often running very superﬁciallyor indistinctly.

The Steninae of Japan Part 3

Fig. 25. Stenus inexoratus Puthz (Ehime: A, Saragamine; Hiroshima: B, C, E–G, I, J, Hoei, D, H, Nikyukyo). A,
7th ventrite of male; B, 9th and 10th terga of male; C, gonocoxite; D, 8th ventrite of male; E, endophallic
expulsion hooks; F, 9th ventrite of male; G, H, copulatory tube; I, spermatheca; J, aedeagus. Scale 1: 0.25 mm
for A; scale 2: 0.2 mm for B, D, F, J, 0.1 mm for C, E, G–I.

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Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

Male: Abdomen modiﬁed with or without a semicircular ﬂat area on the 6th, always with alarge, bell-shaped, shallow depression and also a very broad, arcuate posterior emargination(which is broader than the depression) on the 7th (Fig. 25A), and an arcuate emargination on the
8th ventrite (Fig. 25D); 9th tergum (Fig. 25B) with ventral apophyses relatively short; 9th ventrite (Fig. 25F) with macrosetae long, apicolateral teeth long, acute, apicolateral setae moderately
long; 10th tergum (Fig. 25B) very shallowly emarginate posteriorly. Aedeagus (Fig. 25J) withmedian lobe slender, elongate; apical sclerotized area elongate-triangular in shape, with a thin,
median longitudinal suture. Endophallus (Fig. 25J) with copulatory tube (Fig. 25G, H) havingbasal chamber large, ovoidal, main tube attenuate, broad at base, simply pointed at apex; dorsolateral bands thin; expulsion hooks (Fig. 25E) elongate, each with anterior plate pointed at anterior tip, posterior plate slightly hollowed mesially, covered laterally with very minute, pointed
tubercles; ventromedian bands long, relatively thin. Parameres (Fig. 25J) thin, each very acutely
pointed at apex; apical area moderately long to long, weakly to moderately swollen mesially atbase, mesially also with 7 to 12 setae of various length.
Female: Eighth ventrite obtuse or pointed posteromedially; gonocoxites (Fig. 25C) each withapicolateral tooth long, acute, apicolateral setae very long. Spermatheca (Fig. 25I) with capsulelarge, subovoidal; striped duct short, thick; duct long, moderately thick to very thick, coiled, witha large, nearly fusiform apical chamber; gland spherical, small, with opening situated on the lateral side of duct between the 1st and 2nd turns; basal valve very short; basal duct short.
Biology and ecology. S. inexoratus is a common species. The beetles of this species inhabit
leaf litter heaped in the natural forests of lowlands to mountainous regions.
Remarks. S. inexoratus is allied to S. oblongulus, but it is separable from the latter species by
the 7th ventrite of male posteromedially with a large, shallow depression (Fig. 25A), the aedeagal median lobe a little narrower, with its apical sclerotized area longer and narrower (Fig. 25J),
and the endophallic expulsion hook narrower, with its posterior plate simple (or not swollen) laterally, and densely covered laterally with very minute, pointed tubercles (Fig. 25E).
Stenus yoshitomii Naomi(Fig. 26A–G)
Stenus yoshitomii Naomi, 2015a: 222.
Type material examined. Holotype: ♂ (EUMM), Yokono, Nishidani, Yanadani Vil., Ehime
Pref., 16. x. 1993, M. Sakai leg. Paratypes: 1 ♀ (EUMM), same data as holotype; 1 ♂, Yokono(670 m), Yanadani Vil., Ehime Pref., 1–2. x. 1994, M. Sakai leg.; 1 ♀, same data as holotype, M.
Sakai leg.
Distribution. Japan: Shikoku (Ehime Pref.).
Redescription. Male and female: Body 2.9–3.8 mm (fore body 1.5–1.8 mm) in length. Body
moderately shining; head black; pronotum, elytra and abdomen dark red to dark reddish brown;
labrum reddish brown to dark reddish brown; antennae and legs yellowish brown to reddish
brown. Body with punctures round to ovoidal or elliptical, small to moderately large, and also
pronotum partially with coarse to subrugose punctures and elytra partially with large, coarse tosubrugose punctures. Head moderately concave, with a pair of longitudinal-oblique furrows;
antennae short to moderately long, thin; pronotum with surface slightly uneven to uneven, with a
median longitudinal furrow indistinct; elytra with surface slightly uneven to uneven; abdomensubcylindrical, slightly tapering posteriorly to subparallel-sided; lateroventrites and tergoventral

The Steninae of Japan Part 3

Fig. 26. Stenus yoshitomii Naomi (Ehime: Yanadani). A, 9th and 10th terga of male; B, 9th ventrite of male; C,
6th to 8th ventrites of male; D, aedeagus; E, endophallic expulsion hooks; F, spermatheca; G, posterior part ofgonocoxite. Scale 1: 0.2 mm for A–B, D, 0.1 mm for E–G; scale 2: 0.3 mm for C.

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Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

sutures almost lost.
Male: Legs with femora moderately thick; abdomen (Fig. 26C) modiﬁed with a large, semicircular, shallow depression on the 6th, a moderately deep depression on the 7th, and a subtriangular emargination on the 8th ventrite; 9th tergum (Fig. 26A) with ventral apophyses long; 9th
ventrite (Fig. 26B) with macrosetae moderately long, apicolateral teeth moderately long, very
acute, apicolateral setae moderately long; 10th tergum (Fig. 26A) almost rounded posteriorly.
Aedeagus (Fig. 26D) with median lobe elongate, gently rounded and broadest at apicolateral corners, acutely pointed at apex; apical sclerotized area small, subtriangular, basally with a subtrapezoidal projection. Endophallus (Fig. 26D) with copulatory tube having basal chamber elongateovoidal in shape, main tube short, attenuate, acicular at apical part; dorsolateral bands very thin;
expulsion hooks (Fig. 26E) moderately large, each with anterior plate weakly turning anterolaterally, posterior plate well-sclerotized laterally, broadly hollowed mesially; ventromedian bands
moderately long, relatively thin. Parameres (Fig. 26D) each acutely pointed at apex; apical area
long, strongly narrowed apicad, mesially with 8 to 9 setae of various length.
Female: Eighth ventrite obtuse posteromedially; gonocoxites (Fig. 26G) each with apicolateral tooth long, very acute, apicolateral setae very long. Spermatheca (Fig. 26F) with capsule
moderately large; striped ductal area very thick but indistinct; duct moderately long, thick, tightly
coiled with 6 turns, and with the distal-most part of duct forming a large, laterally slightly swollen, apical chamber which is crossed with 2 transverse lines; gland large, spherical, with opening
located on the mesial side of duct a little distal from the 1st turn; basal valve short; basal ductsclerotized, with thick wall. Basal structure (Fig. 26F) truncated-conical in shape, membranous.
Biology and ecology. The beetles of S. yoshitomii inhabit leaf litter heaped in the natural forests of mountainous regions.
Remarks. S. yoshitomii is closely allied to S. coﬀeatus, but it is separale from the latter species by the aedeagal median lobe broadest at the apicolateral corners (Fig. 26D), with its apicalsclerotized area small but developed (Fig. 26D), the endophallic explusion hook larger andbroader (Fig. 26E), and the spermatheca with its tube less strongly coiled, distally with the apicalchamber (Fig. 26F).
Etymology. This species is named after Dr. Hiroyuki Yoshitomi (Ehime University) who
studies the taxonomy of some Coleopterous families and also the biology and descriptions ofColeopterous larvae.
Stenus coﬀeatus Naomi(Figs. 27A–M, 132A)
Stenus coﬀeatus Naomi, 2012: 291; Naomi & Puthz, 2013: 143.
Type material examined. Holotype: ♂ (CBM), Cape Ashizuri, Kochi Pref., 5. v. 1988, T. Itoleg. Paratypes: 7 ♂9 ♀, same data as holotype; 11 ♂10 ♀, same locality, 6. v. 1988, T. Ito leg.;2 ♂, same locality, 7. v. 1988, T. Ito leg.; 5 ♂6 ♀, same locality, 1–3. v. 1997, T. Ito leg.; 1 ♂4 ♀,Nametoko Valley, Uwajima City, Ehime Pref., 13. xi. 1998, S. Nomura leg.
Distribution. Japan: Shikoku (Kochi and Ehime Prefs.).
Redescription. Male and female: Body 3.5–4.3 mm (fore body 1.6–2.1 mm) in length. Body
weakly or moderately shining; head and abdomen almost black to black; pronotum and elytra
dark red; labrum reddish brown to dark brown; antennae and legs reddish brown. Body with
punctures round to ovoidal, small to moderately large, and also pronotum partially with coarse

The Steninae of Japan Part 3

Fig. 27. Stenus coﬀeatus Naomi (Kochi: Cape Ashizuri). A, 6th and 7th ventrites of male; B, 8th ventrite of male;C, gonocoxite; D, 9th ventrite of male; E, I, copulatory tube; F, spermatheca; G, H, L, M, endophallic expulsion hooks; J, K, aedeagus. Scale 1: 0.25 mm for A; scale 2: 0.25 mm for B; scale 3: 0.2 mm for D, J, K,
0.1 mm for C, E, F–I, L, M.

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Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

punctures and elytra partially with large, coarse punctures. Head shallowly to moderately concave, with a pair of longitudinal-oblique furrows or depressions; antennae short to moderately
long, very thin to thin; pronotum with surface slightly uneven to uneven, with a median longitudinal furrow indistinct; elytra with surface slightly uneven to uneven; abdomen subcylindrical,
slightly tapering posteriorly to subparallel-sided; lateroventrites lost, tergoventral sutures runningvery superﬁcially or indistinctly.
Male: Abdomen (Fig. 27) modiﬁed with a ﬂat area on the 7th, and an arcuate, relatively
broad emargination on the 8th ventrite (Fig. 27); 9th tergum with ventral apophyses moderately
long; 9th ventrite (Fig. 27) with macrosetae slightly short, apicolateral teeth short, very acute,apicolateral setae short; 10th tergum almost rounded posteriorly. Aedeagus (Fig. 27J, K) withmedian lobe elongate, rounded at apicolateral corners, almost rounded apically; apical sclerotized hardly developed. Endophallus (Fig. 27J, K) with copulatory tube having basal chambersubovoidal, medium-sized (Fig. 27I) or large (Fig. 27E), main tube moderately long, attenuate;
dorsolateral bands thin; expulsion hooks usually located in parallel, each hollowed mesially (Fig.
27M) or with posterior plate hollowed mesially (Fig. 27G, H), and also each hook slender,
straight (Fig. 27G, H) or each with anterior plate more or less turning anterolaterally (Fig. 27 L,M); ventromedian bands moderately long, very thin. Parameres (Fig. 27J, K) slender, very thin tothin, each very acutely pointed at apex; apical area short, moderately swollen mesially at base,mesially also with 8 to 10 setae.
Female: Eighth ventrite obtuse or almost rounded posteromedially; gonocoxites (Fig. 27C)
each with apicolateral tooth very long, very acute, apicolateral setae very long. Spermatheca(Fig. 27F) with capsule very small, rounded apically; striped duct moderately long, thick; duct
long, moderately thick to thick, very tightly coiled; gland moderately large; basal valve short;basal duct sclerotized, short.
Biology and ecology. The beetles of S. coﬀeatus inhabit leaf litter heaped in the natural forests of plains and mountainous regions.
Remarks. S. coﬀeatus is closely allied to S. yoshitomii, but it is separable from the latter species by the aedeagal median lobe broadest before the middle (Fig. 27J, K), with its apical sclerotized area hardly developed (Fig. 27J, K), the endophallic expulsion hook smaller and narrower(Fig. 27G, H, L, M), and the spermatheca with its tube more strongly coiled, without apicalchamber (Fig. 27F).
Stenus ryugu Naomi(Figs. 28A–J, 132B)
Stenus ryugu Naomi, 1989b: 51 (in part); Herman, 2001: 2375; Naomi & Puthz, 2013: 143.
Type material examined. Holotype: ♂ (KUF), Mt. Shiratake, Tsushima Is., Nagasaki Pref.,17. x. 1983, S. Nomura leg. Paratypes: 2 ♂1 ♀, same data as holotype.
Other material examined. [KYUSHU]: 1 ♂1 ♀, Kamizaka, Tsushima Is., Nagasaki Pref., 21.
iii. 1979, S. Tanaka leg.; 1 ♂2 ♀, Mt. Mitake, Tsushima Is., Nagasaki Pref., 16. vii. 1999, H.
Hoshina leg.; 1 ♂2 ♀, Mt. Tatera, Tsushima Is., Nagasaki Pref., 18. x. 1983, S. Nomura leg.
Distribution. Japan: Kyushu (Nagasaki Pref.: Tsushima Is.).
Redescription: Male and female: Body 3.6–4.2 mm (fore body 1.6–1.9 mm) in length. Body
weakly shining; head black, sometimes with clypeofrontal area dark brown near black; pronotumand elytra reddish brown to dark brown; abdomen reddish brown to dark brown near black or

The Steninae of Japan Part 3

Fig. 28. Stenus ryugu Naomi (Nagasaka, Tsushima Is.: A, G, Himi, B, C, Mt. Mitake, D, F, J, Mt. Shiratake, E, I,
Kamizaka, H, Tatera). A, 9th and 10th terga of male; B, spermatheca; C, 6th and 7th ventrites of male; D,aedeagus; E, copulatory tube; F, I, J, endophallic expulsion hooks; G, 9th ventrite of male; H, posterior part ofgonocoxite. Scale 1: 0.2 mm for A, D, G, 0.1 mm for B, E, F, H–J; scale 2: 0.3 mm for C.

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Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

black; labrum dark red to almost black; antennae and legs reddish brown. Body with punctures
small to moderately large, round to ovoidal, and also pronotum and elytra partially with coarse
punctures. Head moderately concave, with a pair of longitudinal-oblique furrows; antennae short
to moderately long, very thin to thin; pronotum with surface slightly uneven, with a median longitudinal furrow very indistinct; elytra with surface slightly uneven to uneven; abdomen subcylindrical, slightly tapering posteriorly to subparallel-sided; lateroventrites and tergoventrite
sutures lost.
Male: Abdomen (Fig. 28C) modiﬁed with a ﬂat area on the 7th, and an arcuate, broad emargination on the 8th ventrite; 9th tergum (Fig. 28A) with ventral apophyses long; 9th ventrite (Fig.
28G) with macrosetae long, apicolateral teeth moderately long, very acute, apicolateral setaevery long; 10th tergum (Fig. 28A) very shallowly emarginate posteriorly. Aedeagus (Fig. 28D)
with median lobe very slender, pointed at apex; apical sclerotized area subtriangular. Endophallus (Fig. 28D) with copulatory tube (Fig. 28E) having main tube comprising basal tube (fusedwith basal chamber?) elongate-rectangular in shape, apical tube short, attenuate, thin (Fig. 28D),
sometimes curved (Fig. 28E); dorsolateral bands very thin; expulsion hooks (Fig. 28F, G, H)
moderately broad to broad, each with posterior plate strongly arcuately emarginate laterally, fanshaped in the posterior part; ventromedian bands moderately long, moderately broad. Parameres(Fig. 28D) slender, each pointed at apex; apical area rather long, weakly swollen mesially atbase, mesially also with a setal tuft at base and 4 to 5 setae of various length in the apical 1/2.
Female: Eighth ventrite obtuse posteromedially; gonocoxites (Fig. 28H) each with apicolateral tooth moderately long, very acute, apicolateral setae very long. Spermatheca (Fig. 28B) with
capsule absent; striped duct moderately long, very thick, covered with very dense transverse
stripes; duct short, moderately thick, with 2 turns; gland small, spherical, with opening locatedon the mesial side of duct near the 2nd turn; basal valve relatively short, basal duct fused withbasal pouch which is strongly sclerotized and subconical.
Biology and ecology. The beetles of S. ryugu inhabit leaf litter heaped in the natural forestsof lowlands to low mountainous regions.
Remarks. S. ryugu is closely allied to S. tsushimamontis, but it is separable from the latter
species by the abdominal modiﬁcations of male developed on the 7th and 8th ventrites (Fig.
28C), the aedeagal median lobe more slender (Fig. 28D), the endophallic expulsion hookbroader, with its posterior plate more strongly expanded laterally at the posterolateral corner(Fig. 28F, I, J), and the spermatheca with its duct thinner (Fig. 28B). S. ryugu is also allied to S.
akikoae, but it is easily separable from the latter species by the copulatory tube with its basal
chamber elongate-rectangular in shape (Fig. 28E) and the aedeagal paramere shorter (Fig. 28D).
Etymology. The speciﬁc epithet of this species is derived from the Japanese term whichmeans the imaginary palace appeared in an ancient Japanese folk tale, ryugu.
Stenus tsushimamontis Naomi, Nomura & Puthz sp. nov.
(Fig. 29A–J)
Stenus ryugu Naomi, 1989b: 51 (in part).
Type material examined. Holotype: ♂(KUMF), Izuhara, Tsushima Is., Nagasaki Pref., 20. x.
1983, S. Nomura leg. Paratypes: 1 ♂6 ♀, same data as holotype; 3 ♂2 ♀, Kamizaka, Tsushima Is.,
Nagasaki Pref., 27. iv. 1982, S. Nomura leg.; 2 ♂2 ♀ (paratypes of S. ryugu), Mehoro, TsushimaIs., Nagasaki Pref., 20. x. 1983, S. Nomura leg.; 2 ♂ (paratypes of S. ryugu), Tsushima Is., Naga-

The Steninae of Japan Part 3

77saki Pref., 27. v. 1990, H. Makihara leg.
Other material examined. [KYUSHU]: 2 ♂1 ♀, Mt. Senpyomaki, Tsushima Is., Nagasaki
Pref., 28. Iv. 1992, S. Nomura leg.
Distribution. Japan: Kyushu (Nagasaki Pref.: Tsushima Is.).
Description: Male and female: Body 3.4–4.3 mm (fore body 1.6–2.0 mm) in length. Body
moderately shining; head black; pronotum dark reddish brown to dark brown; elytra reddish
brown to dark reddish brown; abdomen dark brown to black; labrum dark red; antennae and legs
yellowish brown to reddish brown. Body with punctures small to moderately large, round to
ovoidal, and also elytra partially with large, coarse to subrugose punctures. Head moderately
concave, with a pair of longitudinal-oblique furrows; antennae short to moderately long, verythin to thin; pronotum with surface slightly uneven, with a median longitudinal furrow very
indistinct; elytra with surface slightly uneven to uneven; abdomen subcylindrical, slightly tapering posteriorly to subparallel-sided; lateroventrites and tergoventrite sutures lost.
Male: Abdomen (Fig. 29J) modiﬁed with an arcuate emargination on the 8th ventrite; 9th tergum (Fig. 29A) with ventral apophyses very long; 9th ventrite (Fig. 29B) with macrosetae very
long, apicolateral teeth short, acute, apicolateral setae long; 10th tergum (Fig. 29A) very shallowly emarginate posteriorly. Aedeagus (Fig. 29C) with median lobe slender, obtusely pointed atapex; apical sclerotized area subtriangular. Endophallus (Fig. 29C) with copulatory tube (Fig.
29D) having main tube consisting of thick basal tube and stick-like apical tube; expulsion hooks(Fig. 29F, G, H) elongate, thin, each with anterior plate more or less curved laterally; ventromedian bands long, relatively thin. Parameres (Fig. 29C) each acutely pointed at apex; apical arearather long, weakly swollen mesially at base, mesially also with a setal tuft at base and 5 setae ofvarious length in the apical 1/2 or 2/3.
Female: Eighth ventrite obtuse posteromedially; gonocoxites (Fig. 29H) each with apicolateral tooth moderately long, very acute, apicolateral setae very long. Spermatheca (Fig. 29E) with
capsule hardly developed; striped duct long, very thick, covered with very dense transverse
stripes; duct very short, very thick, with 2 turns; gland small, ovoidal, with opening located on
the lateral side of duct near the 2nd turn; basal valve very short, basal duct very short; basal
pouch almost conical.
Biology and ecology. The beetles of S. tsushimamontis inhabit leaf litter heaped in the naturalforests of lowlands to low mountainous regions.
Remarks. S. ryugu was ﬁrst newly described from Tsushima Is. in Naomi (1989b). In thecourse of this study, a lot of Stenus specimens of the cephalotes-group from Tsushima Is. were
examined. We noticed that two diﬀerent species are included in the paratypes of S. ryugu, (S.
ryugu and the other species), and the latter is here newly described as S. tsushimamontis, basedon the material including some paratype specimens of S. ryugu.
S. tsushimamontis is closely allied to S. ryugu, but it is separable from the latter species by
the abdominal modiﬁcation of male developed only on the 8th ventrite (Fig. 29J), the aedeagal
median lobe less slender (Fig. 29C), the endophallic expulsion hook narrower, with its posterior
plate less strongly expanded laterally at the posterolateral corner (Fig. 29F, G, I), and the spermatheca with its duct thicker (Fig. 29E). S. tsushimamontis is also allied to S. akikoae, but it is easily separable from the latter species by the aedeagal median lobe less slender and the paramere
shorter (Fig. 29C).
Etymology. The speciﬁc epithet of this species is derived from the name of type locality, Tsushima and the Latin suﬃx -montis which means ʻmountainousʼ.

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Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

Fig. 29. Stenus tsushimamontis Naomi, Nomura & Puthz sp. nov. (Nagasaki, Tsushima Is.: A, Kamizaka, B, D, G,
Izuhara, E, I, H, Mt. Senpyomaki, F, J, Mehoro). A, 9th and 10th terga of male; B, 9th ventrite of male; C,aedeagus; D, copulatory tube; E, spermatheca; F, G, I, endophallic expulsion hooks; H, posterior part of gonocoxite; J, posterior part of 8th ventrite of male. Scale 1: 0.2 mm for A–C, 0.1 mm for D–I; scale 2: 0.3 mm for
J.

The Steninae of Japan Part 3

79

Stenus akikoae Naomi(Fig. 30A–F)
Stenus akikoae Naomi, 2021a: 73.
Type material examined. Holotype: ♂ (KUMF), Tatera, Tsushima Is., Nagasaki Pref., 28. iv.
1967, H. Konishi.
Distribution. Japan: Kyushu (Nagasaki Pref.: Tsushima Is.).
Redescription: Male: Body 3.3 mm (fore body 1.6 mm) in length. Body moderately shining;head black; pronotum and abdomen dark reddish brown; elytra reddish brown; labrum dark red;antennae and legs reddish brown. Body with punctures small to moderately large, round to ovoidal, and also elytra (Fig. E) partially with large, subrugose punctures. Head moderately concave,with a pair of almost longitudinal furrows; antennae short, thin; pronotum with surface slightly
uneven, with a median longitudinal furrow very indistinct; elytra with surface uneven; abdomensubcylindrical, slightly tapering posteriorly; lateroventrites and tergoventrite sutures almost lost.
Abdomen (Fig. 30D) modiﬁed with an arcuate, shallow, broad emargination on the 8th ventrite; 9th tergum (Fig. 30C) with ventral apophyses long; 9th ventrite (Fig. 30B) with macrosetaevery long, apicolateral teeth long, very acute, apicolateral setae very long; 10th tergum (Fig.
30C) very shallowly emarginate posteromedially. Aedeagus (Fig. 30A) with median lobe very
slender, pointed at apex; apical sclerotized area almost triangular. Endophallus (Fig. 30A) withcopulatory tube having main tube moderately long, thick at base, attenuate; expulsion hooks(Fig. 30F) very elongate, thin; ventromedian bands long, moderately broad. Parameres (Fig.
30A) very long, moderately thick, each acutely pointed at apex; apical area extremely long,mesially with a setal tuft at base and 5 setae of various length in the apical 1/2 or 2/3.
Female: Unknown.
Biology and ecology. The beetle of S. akikoae inhabits leaf litter heaped in the natural forestof a low mountainous region.
Remarks. S. akikoae is allied to S. ryugu and S. tsushimamontis, but it is easily separablefrom the latter 2 species by the aedeagal median lobe more slender, the endophallic expulsion
hook more slender and thinner (Fig. 30F), and the paramere longer (Fig. 30A).
Etymology. This species is named after the late wife of ﬁrst author, Akiko Naomi.
Stenus kaguyahime Naomi(Figs. 31A–H, 132C)
Stenus kaguyahime Naomi, 1990: 50; Herman, 2001: 2243; Naomi & Puthz, 2013: 143.
Type material examined. Holotype: ♂ (KUF), Mt. Seburi, Saga Pref., 18. ix. 1977, H. Ohishi
leg. Paratypes: 4 ♂2 ♀, same data as holotype.
Distribution. Japan: Kyushu (Saga Pref.).
Redescription. Male and female: Body 3.5–3.7 mm (fore body 1.7–1.9 mm) in length. Body
moderately shining; head black with clypeofrontal area reddish brown; pronotum, elytra andabdomen reddish brown to dark brown; labrum reddish brown to dark reddish brown; antennae
and legs yellowish brown to reddish brown. Body with punctures small to moderately large,
round to ovoidal, and also pronotum partially coarse to subrugose punctures and elytra partiallywith large, coarse to subrugose punctures. Head shallowly to moderately concave, with a pair of80

Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

Fig. 30. Stenus akikoae Naomi (Nagasaki: Tsushima Is., Tatera). A, aedeagus; B, 9th ventrite of male; C, 9th and10th terga of male; D, posterior part of 8th ventrite of male; E, right elytron; F, endophallic expulsion hooks.
Scale 1: 0.1 mm for A, F; scale 2: 0.1 mm for B, C; scale 3: 0.3 mm for D, E.

The Steninae of Japan Part 3

Fig. 31. Stenus kaguyahime Naomi (Saga: Mt. Seburi). A, 9th and 10th terga of male; B, 6th to 8th ventrites ofmale; C, 9th ventrite of male; D, endophallic expulsion hooks; E, copulatory tube; F, gonocoxite; G, spermatheca; H, aedeagus. Scale 1: 0.1 mm for A; scale 2: 0.25 mm for B; scale 3: 0.2 mm for C, H, 0.1 mm for E–G,
0.05 mm for D.

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longitudinal-oblique furrows; antennae short to moderately long, very thin to thin; pronotumwith surface slightly uneven to uneven, with a median longitudinal furrow very indistinct; elytra
with surface almost even to slightly uneven or uneven; abdomen subcylindrical, subparallelsided; teroventrites and tergoventrites sutures almost lost.
Male: Abdomen (Fig. 31B) modiﬁed with a very shallow depression on the 7th, and an arcuate emargination on the 8th ventrite; 9th tergum (Fig. 31A) with ventral apophyses long; 9th ventrite (Fig. 31C) with macrosetae moderately long, apicolateral teeth short, acute, apicolateral
setae relatively short; 10th tergum very shallowly emarginate posteromedially. Aedeagus (Fig.
31H) with median lobe very slender, very slightly, uniformly rounded laterally, pointed at apex;
apical sclerotized area small, almost elongate-triangular in shape. Endophallus (Fig. 31H) withcopulatory tube (Fig. 31E) with main tube attenuate but twice slightly curved on its way; expulsion hooks (Fig. 31D) atrophied, connected to form a very small, V-shaped sclerite; ventromedian bands each very short, very narrow. Parameres (Fig. 31H) very long; apical area very long,mesially with a setal tuft at base and 5 setae of various length in about apical 1/2.
Female: Eighth ventrite almost rounded posteriorly; gonocoxites (Fig. 31F) each with apicolateral tooth very long, very acute, apicolateral setae long. Spermatheca (Fig. 31G) with capsulelong, moderately thick, weakly narrowing apicad; striped ductal area short, thick, entirely membranous; duct moderately thick to thick, short with 2 turns, with a large, mesially swollen apicalchamber; gland with opening located on the lateral side of duct between the 1st and 2nd turns;
basal valve moderately long; basal duct short, weakly sclerotized.
Biology and ecology. The beetles of S. kaguyahime inhabit leaf litter heaped in the naturalforests of a mountainous region.
Remarks. S. kaguyahime is allied to S. otohime, but it is separable from the latter species by
the aedeagal median lobe broader, less strongly pointed at the apex, the spermatheca with a large,
mesially swollen, apical chamber (Fig. 31G), and the paramere sparsely setose mesially (Fig.
31H).
Etymology. The speciﬁc epithet of this species is derived from the Japanese name of a Princess appeared in an ancient Japanese folk tale, Kaguyahime.
Stenus otohime Naomi(Fig. 32A–F)
Stenus kaguyahime Naomi, 1990: 48; Herman, 2001: 2317; Naomi & Puthz, 2013: 143.
Type material examined. Holotype: ♂ (KUF), Mt. Seira, Imari City, Saga Pref., 28. v. 1984,
S. Nomura leg. Paratypes: 1 ♂1 ♀, same data as holotype; 1 ♀, Imari City, Saga Pref., 29. vii.
1976, H. Ohishi leg.
Other material examined. [KYUSHU]: 1 ♂2 ♀, Mt. Seira, Imari City, Saga Pref., 5. iv. 1983,
S. Nomura leg.
Distribution. Japan: Kyushu (Saga Pref.).
Redescription. Male and female: Body 3.4–4.5 mm (fore body 1.6–2.1 mm) in length. Body
moderately shining; head and abdomen dark brown near black to black; pronotum and elytra
dark reddish brown to dark brown; labrum reddish brown to dark red; antennae and legs yellowish brown to reddish brown. Body with punctures small to moderately large, round to ovoidal,
and also pronotum partially coarse punctures and elytra partially with large, coarse to subrugose
punctures. Head shallowly to moderately concave, with a pair of longitudinal-oblique furrows orThe Steninae of Japan Part 3

Fig. 32. Stenus otohime Naomi (Saga: Imari). A, 9th ventrite of male; B, 9th and 10th terga of male; C, spermatheca; D, aedeagus; E, 7th and 8th ventrites of male; F, posterior part of gonocoxite. Scale 1: 0.1 mm for A, B;
scale 2: 0.1 mm for C, F, 0.2 mm for D; scale 3: 0.3 mm for E.

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depressions; antennae short to moderately long, very thin to thin; pronotum with surface slightly
uneven to uneven, with a median longitudinal furrow hardly developed or very indistinct; elytra
with surface slightly uneven to uneven; abdomen subcylindrical, slightly tapering posteriorly;
teroventrites and tergoventrites sutures lost.
Male: Abdomen (Fig. 32E) modiﬁed with a shallow depression on the 7th, and an arcuate,
broad emargination on the 8th ventrite; 9th tergum (Fig. 32B) with ventral apophyses long; 9th
ventrite (Fig. 32A) with macrosetae veryy long, apicolateral teeth moderately long, acute, apicolateral setae very long; 10th tergum shallowly emarginate posteriorly. Aedeagus (Fig. 32D) withmedian lobe very slender, attenuate, very acutely pointed at apex; apical sclerotized area small,almost elongate-triangular in shape. Parameres (Fig. 32A) very long, each curved mesially atbase, with thick, robust pedicel; apical area very long, mesially with about 28 setae of various
length.
Female: Eighth ventrite obtuse posteromedially; gonocoxites (Fig. 32F) each with apicolateral tooth long, very acute, apicolateral setae very long. Spermatheca (Fig. 32C) with capsulesmall, well-rounded apically; striped duct very thick, including 2 membranous parts; duct moderately thick, short with 4 turns, with a very large, subfusiform apical chamber; basal valve short;basal duct very short, sclerotized.
Biology and ecology. The beetles of S. otohime inhabit leaf litter heaped in the natural forestsof a mountainous region.
Remarks. S. otohime is allied to S. kaguyahime, but it is separable from the latter species by
the aedeagal median lobe narrower, and more strongly pointed at the apex, the paramere very
densely setose mesially (Fig. 32D) and the spermatheca with a very large, subfusiform apicalchamber (Fig. 32C).
Etymology. The speciﬁc epithet of this species is derived from the Japanese name of a Princess appeared in an ancient Japanese folk tale, Otohime.
Stenus dainichi Puthz(Figs. 33A–H, 132D)
Stenus dainichi Puthz, 2001: 50; Naomi & Puthz, 2013: 144.
Type material examined. Holotype: ♂ (SMNHS), Mt. Nachi (350 m), Wakayama Pref., 13.
vii. 1999, V. Puthz leg.
Other material examined. [HONSHU]: 4 ♂1 ♀, Mt. Nachi, Wakayama Pref., 21. vii. 1984, T.
Ito leg.
Distribution. Japan: Honshu (Wakayama Pref.).
Redescription. Male and female: Body 3.2–3.9 mm (fore body 1.4–1.9 mm) in length. Body
moderately shining; head black, sometimes with clypeofrontal area reddish brown; pronotum,
elytra and abdomen reddish brown to dark reddish brown; labrum reddish orange; antennae andlegs clear yellow brown to reddish brown. Body with punctures round to almost round, small tomoderately large, and also pronotum and elytra partially with coarse punctures. Head shallowly
to moderately concave, with a pair of longitudinal-oblique or almost longitudinal furrows; antennae short to moderately long, very thin to thin; pronotum with surface slightly uneven, with a
median longitudinal furrow indistinct; elytra with surface slightly uneven to uneven; abdomensubcylindrical, subparallel-sided; lateroventrites and tergoventral sutures lost.
Male: Abdomen (Fig. 33E) modiﬁed with a very shallow or shallow depression on the 7th,

The Steninae of Japan Part 3

Fig. 33. Stenus dainichi Puthz (Wakayama: Mt. Nachi). A, 9th ventrite of male; B, 9th and 10th terga of male; C,aedeagus; D, spermatheca; E, 7th and 8th ventrites of male; F, copulatory tube; G, posterior part of gonocoxite; H, endophallic expulsion hooks. Scale 1: 0.1 mm for A; scale 2: 0.2 mm for B, 0.1 mm for D, F–H; scale 3:
0.1 mm for C; scale 4: 0.3 mm for E.

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and an arcuate emargination on the 8th ventrite; 9th tergum (Fig. 33B) with ventral apophyses
moderately long; 9th ventrite (Fig. 33A) with apicolateral teeth very long, very acute, apicolateral setae very long; 10th tergum (Fig. 33B) very shallowly emarginate posteriorly. Aedeagus(Fig. 33C) with median lobe narrowly rounded at apicolateral corners, obtusely pointed at apex;
apical sclerotized area nearly crescent, slightly protruding posteriorly at median part. Endophallus (Fig. 33C) with copulatory tube with main tube long, attenuate, slightly (Fig. 33F) or moderately (Fig. 33C) curved behind the middle; dorsolateral bands very thin; expulsion hooks (Fig.
33H) moderately broad, each with anterior plate obtusely pointed at anterior tip; ventromedianbands broad, slightly short. Parameres (Fig. 33C) long, moderately thick, each pointed at apex;
apical area long, mesially with 10 setae of various length.
Female: Eighth ventrite obtuse posteomedially; gonocoxites (Fig. 33G) each with apicolateral tooth very long, very acute, apicolateral setae very long. Spermatheca (Fig. 33D) with capsule moderately long, thick; striped duct moderately long, thick; duct slightly short, moderately
thick to thick, coiled with 4 turns; gland small, ovoidal, with opening located on the lateral sideof duct between the 3rd and 4th turns; basal valve very short; basal duct sclerotized, long, thick;basal pouch conical, membranous.
Biology and ecology. The beetles of S. dainichi inhabit leaf litter heaped in the deciduous
natural forests of a low mountainous region.
Remarks. S. dainichi seems to be allied to S. amagasui, but it is separable from the latter species by the aedeagal median lobe with its apical sclerotized area less strongly developed (Fig.
33C), the endophallic copulatory tube with its main tube longer and curved (Fig. 33C, F), theexpulsion hook with its posterior plate developed, about as large as anterior plate (Fig. 33H).
Etymology. The speciﬁc epithet of this species is derived from a Japanese name of Buddha,
Dainichi.
Stenus amagasui Naomi(Fig. 34A–G)
Stenus amagasui Naomi, 2007: 73; Naomi & Puthz, 2013: 144.
Type material examined. Holotype, 1 ♂ (CBM), Ohuchiyama Vil., Watarai-gun, Mie Pref.,11. iv. 1996, H. Ichihashi leg. Paratypes: 1 ♂1 ♀, Fujikawa, Ohmiya-cho, Watarai-gun, Mie Pref.,14. iii. 1996, H. Yokozeki leg; 1 ♂, Nako, Kisei-cho, Watarai-gun, 18. xii. 1998, A. Amagasu
leg.; 4 ♂9 ♀, Nishiki, Kisei-cho, Watarai-gun, Mie Pref., 1. ii. 1997, A. Amagasu leg.; 3 ♂2 ♀,Minamimata, Ohuchiyama Vil., Mie Pref., 4. xi. 1996, K. Kanno leg.
Other material examined. [SHIKOKU]: 1 ♂1 ♀, Mt. Mayu, Tokushima City, Tokushima
Pref., 20. iv. 2003, M. Inagaki leg.
Distribution. Japan: Honshu (Mie Pref.) and Shikoku (Tokushima Pref.).
Redescription. Male and female: Body 2.9–3.5 mm (fore body 1.3–1.8 mm) in length. Body
moderately shining; head black, sometimes with median or clypeofrontal area reddish brown;
pronotum and elytra reddish brown to dark reddish brown; abdomen reddish brown to darkbrown or almost black; labrum reddish brown; antennae and legs reddish brown. Body with
punctures small to moderately large, round to elliptical, and pronotum partially with coarse tosubrugose punctures and elytra also partially large, coarse punctures. Head moderately concave,with a pair of longitudinal-oblique furrows; antennae short to moderately long, very thin to thin;pronotum with surface slightly uneven to uneven, with a median longitudinal furrow indistinct;

The Steninae of Japan Part 3

Fig. 34. Stenus amagasui Naomi (Mie: Nishiki). A, 9th and 10th terga of male; B, 9th ventrite of male; C,aedeagus; D, spermatheca; E, 7th and 8th ventrites of male; F, posterior part of gonocoxite; G, endophallic
expulsion hooks. Scale 1: 0.1 mm for A–C; scale 2: 0.1 mm for D, F, 0.05 mm for G; scale 3: 0.3 mm for E.

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elytra with surface slightly uneven to uneven; abdomen subcylindrical, subparallel-sided; lateroventrites and tergoventrites sutures lost.
Male: Abdomen (Fig. 34E) modiﬁed with a slightly deep depression on the 7th, and a shallow, broad emargination on the 8th ventrite; 9th tergum (Fig. 34A) with ventral apophyses
slightly short, very broad; 9th ventrite (Fig. 34B) with apicolateral teeth short, very acute, apicolateral setae moderately long; 10th tergum shallowly emarginate posteromedially. Aedeagus (Fig.
34C) with median lobe almost rounded at apicolateral corners, pointed at apex; apical sclerotizedarea triangular, basally with an arcuate, broad notch. Endophallus (Fig. 34C) with copulatory
tube with basal chamber large, ovoidal at base, main tube short, slightly thick, attenuate behindthe middle; dorsolateral bands each thick at base; expulsion hooks (Fig. 34C, G) small, each withanterior plate broad-subtriangular in shape, posterior plate reduced to an oblique, very thin plate
which is broadly connected with anterior plate; ventromedian bands each slightly short, broad at
the posterior rim. Parameres (Fig. 34C) slender, each acutely pointed at apex; apical area very
long, thin, mesially with 8 to 9 moderately long to long setae.
Female: Eighth ventrite obtuse posteromedially or almost rounded posteriorly; gonocoxites(Fig. 34F) each with apicolateral teeth long, almost acute, apicolateral setae very long. Spermatheca (Fig. 34D) with capsule very small, subconical; striped duct very long, moderately thick tothick, narrowing apicad in the apical 1/4; duct thick, short with 2 turns; gland small, almost ovoidal, with opening located on the duct near the 2nd turn; basal valve very short; basal duct moderately long and thick.
Biology and ecology. The beetles of S. amagasui inhabit leaf litter heaped in the natural forests of lowlands to low mountainous regions.
Remarks. S. amagasui seems to be allied to S. dainichi, but it is separable from the latter species by the aedeagal median lobe with its apical sclerotized area more strongly developed (Fig.
34C), the copulatory tube with its main tube shorter and straight (Fig. 34C, F), the endophallic
expulsion hook with its posterior plate reduced to an oblique, thin plate which is broadly connected with anterior plate (Fig. 34G).
Etymology. This species is named after Mr. A. Amagasu (Mie) who collected lots of Stenusbeetles which are designated as the paratype specimens.
Stenus ivanloebli Naomi, Nomura & Puthz sp. nov.
(Figs. 35A–G, 132E)
Type material examined. Holotype: ♂ (KUMF), Nunobiki Fall, Kiwa-cho, Kumano City, Mie
Pref., 1. vi. 1996, K. Kanno leg. Paratypes: 1 ♂3 ♀, same locality, 26. v. 1996, K. Akita leg.
Distribution. Japan: Honshu (Mie Pref.).
Description. Male and female: Body 3.3–3.9 mm (fore body 1.6–1.9 mm) in length. Body
weakly shining; head black; pronotum, elytra and abdomen dark brown to dark red near black;labrum reddish brown to dark red; antennae and legs clear yellow brown to reddish brown. Body
with punctures round to ovoidal, small to moderately large, and also pronotum and elytra partially with subrugose punctures. Head shallowly to moderately concave, with a pair of longitudinal-oblique furrows; antennae short to moderately long, very thin to thin; pronotum with surface
slightly uneven, with a median longitudinal furrow indistinct; elytra with surface slightly unevento uneven; abdomen subcylindrical, subparallel-sided; lateroventrites and tergoventral sutures
lost.
Male: Abdomen (Fig. 35E) modiﬁed with an elongate, ﬂat area on the 7th, and a very shal-

The Steninae of Japan Part 3

Fig. 35. Stenus ivanloeblii Naomi, Nomura & Puthz sp. nov. (Mie: Kiwa). A, 9th ventrite of male; B, 9th and10th terga of male; C, aedeagus; D, spermatheca; E, 7th and 8th ventrites of male; F, endophallic expulsion
hooks; G, posterior part of gonocoxite. Scale 1: 0.1 mm for A, C; scale 2: 0.2 mm for B, 0.1 mm for D, F, G;
scale 3: 0.3 mm for E.

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low, broad emargination on the 8th ventrite; 9th tergum (Fig. 35B) with ventral apophyses moderately long; 9th ventrite (Fig. 35A) with apicolateral teeth very long, very acute, apicolateral
setae very long; 10th tergum (Fig. 35B) almost entire. Aedeagus (Fig. 35C) with median lobe
elongate, obtusely angulate at apicolateral corners, subtruncate posteriorly, with a very minute,crescent apicomedian cusp; apical sclerotized area hardly developed, comprising a relatively
thick posterior rim. Endophallus (Fig. 35C) with copulatory tube very long, with basal chamberlarge, elongate-ovoidal in shape, main tube attenuate, moderately curved behind the middle; dorsolateral bands very thin; expulsion hooks (Fig. 35H) moderately broad, each with anterior plate
pointed at anterior tip, divided into 2 subplates; ventromedian bands broad, moderately long.
Parameres (Fig. 35C) very long, moderately thick, each acutely pointed at apex; apical area very
long, mesially with 11 to 14 setae of various length.
Female: Eighth ventrite pointed posteomedially; gonocoxites (Fig. 35G) each with apicolateral tooth long, acute, apicolateral setae very long. Spermatheca (Fig. 35D) with capsule moderately long, thick; striped duct slightly short, thick; duct short, moderately thick to thick, coiled
with 2 turns; gland very small, ovoidal, with opening located on the mesial side of duct near the
2nd turn; basal valve very short; basal duct sclerotized, moderately long, becoming thicker proximad; basal pouch bowl-shaped, membranous.
Biology and ecology. The beetles of S. ivanloebli inhabit leaf litter heaped in the deciduous
natural forests of a low mountainous region.
Remarks. S. ivanloebli seems to be allied to S. dainichi and S. amagasui, but it is separablefrom the latter 2 species by the aedeagal median lobe subtruncate posteriorly (Fig. 35C), the copulatory tube longer (Fig. 35C), and the endophallic expulsion hook with its anterior plate divided
into 2 subplates (Fig. 35F).
Etymology. This species is named after Dr. Ivan Löbl (Natural History Museum, Geneva)
who studies the Scaphidiinae and Pselaphinae (Staphylinidae) and some other Coleopterous families.
Sepcies unit 2 of the cephalotes-subgroup
Key to the Japanese species of the cephalotes-subgroup (2)This is a key for a unit of Stenus-species (11 species) beginning with S. kyotoensis andalmost adequately diagnosed with the combination of following character conditions: Aedeagal
median lobe moderately broad to broad and also more or less broad even at apicolateral corners(Fig. 40A), or strongly narrowing apicad at least in the posterior 1/2 (Fig. 38A); copulatory tube
very often variously modiﬁed into a tube with beak-shaped apex (Fig. 36F), a very short tube
(Fig. 39E), an elongate-rhombic tube (Fig. 40H), a curved tube (Fig. 41E), a gourd-shaped tube
(Fig. 43A), an elongate-conical tube (Fig. 45F), a thick, baculiform tube (Fig. 46C), etc.
Distribution: Honshu (Tohoku, Kanto, Chubu and Kinki Districts).
1(16)
2(13)
3(6)
4(5)

Male: Aedeagal paramere with apical area shorter than pedicel.
Male: Endophallic expulsions hooks more or less developed.
Male: Copulatory tube beak-shaped at apex; aedeagal paramere acicular at apex.
Male: Sixth ventrite without depression and 8th ventrite with a smaller emargination (Fig.
36D); endophallic expulsion hook with posterior plate angulate laterally (Fig. 36A) .........
.................................................................... S. kyotoensis Naomi, Nomura & Puthz sp. nov.

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91

5(4)

Male: Sixth ventrite with a deep depression (Fig. 37G) and 8th ventrite with a larger
emargination (Fig. 37E); endophallic expulsion hook with posterior plate moderately
rounded laterally (Fig. 37F) ................................................................ S. jamesashei Naomi
6(3) Male: Copulatory tube not beak-shaped at apex; aedeagal paramere obtusely pointed or
narrowly rounded apically.
7(10) Male: Aedeagal median lobe pointed with an apicomedian cusp.
8(9) Male: Aedeagal median lobe with apical sclerotized area much narrower (Fig. 38A);
endophallic expulsion hook with anterior plate slightly turning anterolaterally (Fig. 38A)....................................................................................... S. cinanomontis Naomi & Nomura
9(8) Male: Aedeagal median lobe with apical sclerotized area much broader, (Fig. 39A); endophallic expulsion hook with anterior plate distinctly turning almost laterally (Fig. 39F) ....
..............................................................................................................S. brevispinis Naomi
10(7) Male: Aedeagal median lobe obtuse or rounded apically.
11(12) Male: Aedeagal median lobe obtuse at apex (Fig. 40A); Copulatory tube elongate-rhombic in shape (Fig. 40H)...................................................................... S. incalcaratus Naomi
12(11) Male: Aedeagal median lobe rounded apically (Fig. 41E); Copulatory tube baculiform,
moderately curved (Fig. 41G) .................................................................. S. inamatus Puthz
13(2) Male: Endophallic expulsions hooks atrophied into a pair of small or very small pieces.
14(15) Male: Aedeagal median lobe broader in the posterior 1/2 (Fig. 45B); copulatory tube
elongate-conical in shape (Fig. 45F)....................................................... S. hoshinai Naomi
15(14) Male: Aedeagal median lobe narrower in the posterior 1/2 (Fig. 46D); copulatory tube
baculiform (Fig. 46C) ........................................................ S. regularis Naomi & Watanabe
16(1) Male: Aedeagal paramere with apical area almost as long as or longer than pedicel.
17(20) Male: Aedeagal median lobe broadest near or before the middle, and becoming narrower
toward apicolateral corners.
18(19) Male: Copulatory tube attenuate (Fig. 42E); endophallic expulsion hook lost (Fig. 42H) ..
.............................................................................................................S. inaestimatus Puthz
19(18) Male: Copulatory tube gourd-shaped (Fig. 43A); endophallic expulsion hook almost
developed and membranous (Fig. 43D) .... S. sicyoideus Naomi, Nomura & Puthz sp. nov.
20(17) Male: Aedeagal median lobe becoming slightly broader from near the middle to apicolateral corners, and broadest at apicolateral corners (Fig. 44B). ...................S. keman Naomi

Stenus kyotoensis Naomi, Nomura & Puthz sp. nov.
(Figs. 36A–H, 132F)
Type material examined. Holotype: ♂ (KUMF), Mt. Ooe, Ooe-cho, Kyoto Pref., 4. ix. 2004,
K. Mizuno leg. Paratypes: 9 ♂3 ♀, same data as holotype.
Distribution. Japan: Honshu (Kyoto Pref.).
Description. Male and female: Body 3.5–3.6 mm (fore body 1.5–1.6 mm) in length. Body
moderately shining; head black; pronotum and abdomen dark reddish brown to dark brown; elytra reddish brown; labrum reddish brown to dark red; antennae and legs clear yellow brown toreddish brown. Body with punctures round to elliptical, small to moderately large, and also pronotum partially with coarse punctures and elytra partially with large, subrugose punctures. Head

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Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

Fig. 36. Stenus kyotoensis Naomi, Nomura & Puthz sp. nov. (Kyoto: Ooe). A, endophallic expulsion hooks; B,
9th and 10th terga of male; C, 9th ventrite of male; D, 7th and 8th ventrites of male; E, aedeagus; F, copulatory tube; G, spermatheca; H, posterior part of gonocoxite. Scale 1: 0.1 mm for A, F–H, 0.2 mm for B, C, E;
scale 2: 0.3 mm for D.

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93

moderately concave, with a pair of longitudinal-oblique furrows; antennae short to moderately
long, very thin to thin; pronotum with surface almost even to slightly uneven, with a median longitudinal furrow very indistinct; elytra with surface slightly uneven; abdomen subcylindrical,
thin to moderately thick, subparallel-sided; lateroventrites and tergoventral sutures lost.
Male: Abdomen (Fig. 36D) modiﬁed with a ﬂat area on the 7th, and a subtriangular emargination on the 8th ventrite; 9th tergum (Fig. 36B) with ventral apophyses very long; 9th ventrite(Fig. 36C) with apicolateral teeth long, very acute, apicolateral setae slightly long; 10th tergum(Fig. 36B) entire. Aedeagus (Fig. 36E) with median lobe elongate-ovoidal in shape, almost
rounded apically; apical sclerotized area hardly developed. Endophallus (Fig. 36E) with copulatory tube (Fig. 36F) moderately long, with basal chamber large, elongate-ovoidal in shape, maintube with basal tube baculiform, apical tube atrophied into a very small, beak-shaped tube; dorsolateral bands very thin; expulsion hooks (Fig. 36A) each with anterior plate almost pointed atanterior tip, posterior plate angulate at the middle of lateral part; ventromedian bands each moderately long, thin. Parameres (Fig. 36C) long, each acicular at apex; apical area long, mesiallywith 11 to 12 setae.
Female: Eighth ventrite obtuse posteomedially; gonocoxites (Fig. 36H) each with apicolateral tooth long, very acute, apicolateral setae very long. Spermatheca (Fig. 36G) with capsulenarrowly rounded apically; striped duct very long, thick; duct moderately long, thin to moderately thick, coiled with 6 turns; gland small, spherical, with opening located on the middle ofduct between the last and last 2nd turns; basal valve short; basal duct sclerotized, seamlessly connected with the dish-like, basal pouch.
Biology and ecology. The beetles of S. kyotoensis inhabit leaf litter heaped in the natural forests of a low mountainous region.
Remarks. S. kyotoensis seems to be allied to S. jamesashei, but it is separable from the latter
species by the 8th ventrite of male with its posteromedian emargination much smaller (Fig. 36D),
the aedeagal median lobe almost rounded apically (Fig. 36E), the endophallic expulsion hookwith its posterior plate angulate at the middle of lateral part (Fig. 36A), and the spermatheca withits basal duct shorter (Fig. 36G).
Etymology. The speciﬁc epithet of this new species is derived from the name of type locality,
Kyoto.
Stenus jamesashei Naomi(Fig. 37A–I)
Stenus jamesashei Naomi, 2012: 312; Naomi & Puthz, 2013: 145.
Type material examined. Holotype: ♂ (CBM), Mt. Hira, Shiga Pref., 7. viii. 1987, T. Ito leg.
Paratypes: 5 ♂4 ♀, same data as holotype; 1 ♂6 ♀, same locality, 17. viii. 1986, T. Ito leg.; 1 ♂,same locality, 2. vi. 1957, T. Shibata leg.
Distribution. Japan: Honshu (Shiga Pref.).
Redescription. Male and female: Body 3.4–3.9 mm (fore body 1.6–1.8 mm) in length. Body
weakly shining; head black; pronotum and elytra dark red; abdomen dark red near black toalmost black; labrum reddish brown; antennae and legs yellowish brown to pale reddish brown.
Body with punctures round to ovoidal, small to moderately large, and also pronotum partiallywith coarse punctures and elytra partially with large, subrugose punctures. Head moderately concave, with a pair of longitudinal-oblique furrows; antennae short to moderately long, very thin to94

Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

Fig. 37. Stenus jamesashei Naomi (Shiga: Mt. Hira). A, 9th and 10th terga of male; B, copulatory tube; C, spermatheca; D, aedeagus; E, posterior part of 8th ventrite of male; F, endophallic expulsion hooks, G, 6th and 7th
ventrites of male; H, 9th ventrite of male; I, posterior part of gonocoxite. Scale 1: 0.2 mm for A, D, H, 0.1 mm
for B, C, F, I; scale 2: 0.25 mm for G; scale 3: 0.25 mm for E.

The Steninae of Japan Part 3

95thin; pronotum with surface slightly uneven, with a median longitudinal furrow very indistinct toindistinct; elytra with surface uneven; abdomen subcylindrical, thin to moderately broad, slightly
tapering posteriorly to subparallel-sided; lateroventrites and tergoventral sutures almost lost.
Male: Abdomen (Fig. 37G) modiﬁed with a very shallow depression on the 5th, a deep
depression on the 6th, a deep anteromedian and a moderately deep depressions on the 7th, and avery large, very broad, deep emargination on the 8th ventrite (Fig. 37E); 9th tergum (Fig. 37A)
with ventral apophyses very long; 9th ventrite (Fig. 37H) with macrosetae short, apicolateral
teeth short, acute, apicolateral setae moderately long; 10th tergum (Fig. 37A) almost rounded
posteriorly. Aedeagus (Fig. 37D) with median lobe elongate, almost semicircular, narrow, very
acutely pointed at apex with a moderately long, acicular apicomedian cusp. Endophallus (Fig.
37D) with copulatory tube (Fig. 37B) having basal chamber moderately large, comprising 2
curved rods of diﬀerent length, main tube with basal tube baculiform, moderately thick, apicaltube reduced into a short, triangular one; explusion hooks (Fig. 37F) elongate, each with posterior plate moderately rounded laterally, narrowly pointed at posterior tip; ventromedian bands
long, very narrow. Parameres (Fig. 37D) each acicular and mesially curved at apex; apical area
long, moderately swollen mesially at base, with a membranous protuberance at base, on which
the 15 to 19 setae of various length occur.
Female: Eighth ventrite obtuse posteromedially; gonocoxites (Fig. 37I) each with apicolateral tooth long, acute, apicolateral setae very long. Spermatheca (Fig. 37C) with capsule verysmall, narrowly rounded apically; striped duct very long, thick; duct short, very thin to moderately thick, loosely coiled; gland with opening located on the duct a little proximal from theproximal part of striped duct; basal valve very short; basal duct very long, strongly sclerotized,
becoming broader proximad.
Biology and ecology. The beetles of S. jamesashei inhabit leaf litter heaped in the natural forests of a mountainous region.
Remarks. When considering the common possession of such peculiar conditions as the verybroad emargination of 8th ventrite of male, the spermatheca with its striped duct long or very
long, etc. observed among S. jamesashei, S. cinanomontis and S. brevispinis, these 3 species
seem to be closely allied one another, but S. jamesashei is easily separable from the latter 2 species by the aedeagal paramere with its apical area mesially having a conspicuous membranous
protuberance at base (Fig. 37C), and the endophallic copulatory tube developed and much longer(Fig. 37B).
Etymology. The speciﬁc epithet of this species is named after the late Dr. James S. Ashe
(Kansas University) who studied the Aleocharinae and some other staphylinid subfamilies.
Stenus cinanomontis Naomi & Nomura(Figs. 38A–F, 132G)
Stenus cinanomontis Naomi & Nomura, 2015: 196.
Type material examined. Holotype: ♂ (NMNST), Hyôgoe Pass, Minami-shinano, Nagano
Pref., 16. xi. 1999, S. Nomura leg. Paratypes: 1 ♂2 ♀ (NMNST), same data as holotype; 5 ♂3 ♀,same data as above.
Other material examined. [HONSHU]: 3 ♂1 ♀, Shirabiso Highland, Ue-mura, Nagano Pref.,16. xi. 1999, S. Nomura leg.; 2 ♂3 ♀, Jizo Pass, Ue-mura, Nagano Pref., 16. xi. 1999, S. Nomura
leg.

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Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

Fig. 38. Stenus cinanomontis Naomi & Nomura (Nagano: Hyôgoe Pass). A, aedeagus; B, spermatheca; C, 9th
and 10th terga of male; D, 8th ventrite of male; E, 9th ventrite of male; F, posterior part of gonocoxite. Scale
1: 0.1 mm for A; scale 2: 0.1 mm for B, F, 0.2 mm for C–E.

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97

Distribution. Japan: Honshu (Nagano Pref.).
Redescription. Male and female: Body 3.4–4.0 mm (fore body 1.6–1.9 mm) in length. Body
weakly shining; head black; pronotum and elytra dark red; abdomen dark reddish brown to darkbrown; labrum reddish brown; antennae and legs yellowish brown to pale reddish brown. Body
with punctures round to elliptical, small to moderately large, and also pronotum partially withcoarse punctures and elytra partially with large, subrugose punctures. Head shallowly concave,with a pair of mesially-curved furrows; antennae moderately long, very thin; pronotum with surface slightly uneven to uneven, with a median longitudinal furrow very indistinct to indistinct;
elytra with surface uneven; abdomen subcylindrical, subparallel-sided; lateroventrites and tergoventral sutures lost.
Male: Abdomen modiﬁed with a ﬂat area or a very shallow depression on the 6th, a moderately deep depression on the 7th, and a very broad, subtriangular emargination on the 8th ventrite(Fig. 38D); 9th tergum (Fig. 38C) with ventral apophyses long; 9th ventrite (Fig. 38E) with macrosetae long, apicolateral teeth long, very thin, very acute, apicolateral setae long; 10th tergum(Fig. 38C) entire. Aedeagus (Fig. 38A) with median lobe elongate, becoming almost uniformly
narrower apicad, subtriangular, narrow and strongly pointed with a thin, very long, subulate apicomedian cusp. Endophallus (Fig. 38A) with copulatory tube short, with main tube thick at base,narrowing apicad; dorsolateral bands thin; explusion hooks each with anterior plate slightly turning apicolaterally, posterior plate pointed at posteromesial corner; ventromedian bands very long,thin. Parameres (Fig. 38A) slender, each narrowly rounded apically; apical area long, moderately
swollen mesially, mesially also with 11 to 12 moderately long setae.
Female: Eighth ventrite obtuse posteromedially; gonocoxites (Fig. 38F) each with apicolateral tooth very long, very acute, apicolateral setae very long. Spermatheca (Fig. 38B) with capsule long, well-rounded apically; striped duct long, thick; duct very long, thin, almost tightly
coiled; basal valve short; basal pouch very large, conical.
Biology and ecology. The beetles of S. cinanomontis inhabit leaf litter heaped in the naturalforests of mountainous regions.
Remarks. S. cinanomontis is probably allied to S. brevispinis, but it is separable from the latter species by the aedeagal median lobe much narrower at the apicolateral corners (Fig. 38A),
with its apical sclerotized area having a longer apicomedian cusp (Fig. 38A), the copulatory tube
longer (Fig. 38A), and the endophallic expulsion hook narrower, with its anterior plate slightly
turning apicolaterally (Fig. 38A).
Stenus brevispinus Naomi(Fig. 39A–G)
Stenus brevispinus Naomi, 2015a: 221.
Type material examined. Holotype: ♂ (KUMF), Mt. Sobatsubu, Nakakawane-cho, Shizuoka
Pref., 9. ix. 2004, T. Watanabe leg. Paratypes: 2 ♂5 ♀, same data as holotype; 2 ♂3 ♀, Mt.
Ohfuda, Nakakawane-cho, Shizuoka Pref., 12. x. 2008, S. Naomi leg.; 1 ♀, same locality anddate, T. Shimada leg.; 1 ♀, same locality, 13. x. 2008, T. Sakai leg.
Distribution. Japan: Honshu (Shizuoka Pref.).
Redescription. Male and female: Body 3.2–3.9 mm (fore body 1.6–1.8 mm) in length. Body
weakly shining; head black; pronotum, elytra and abdomen dark red to dark brown; labrum reddish orange to dark reddish brown; antennae and legs yellowish brown to pale reddish brown.

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Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

Fig. 39. Stenus brevispinus Naomi (Shizuoka: Mt. Sobatsubu). A, 6th to 8th ventrites of male; B, 9th and 10th
terga of male; C, spermatheca; D, 9th ventrite of male; E, aedeagus; F, endophallic expulsion hooks, G. posterior part of gonocoxite. Scale 1: 0.2 mm for B, D, E, 0.1 mm for C, F, G; scale 2: 0.3 mm for A.

Body with punctures round to elliptical, small to moderately large, and also pronotum partiallywith coarse to subrugose punctures and elytra partially with large, coarse to subrugose punctures.
Head moderately concave, with a pair of longitudinal-oblique furrows; antennae short, very thin;pronotum with surface slightly uneven, with a median longitudinal furrow very indistinct toindistinct; elytra with surface uneven; abdomen subcylindrical, subparallel-sided; lateroventrites
and tergoventral sutures lost.

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99

Male: Abdomen (Fig. 39A) modiﬁed with a ﬂat area on the 5th or on each of the 4th and 5th,a shallow depression on the 6th, a large, shallow or moderately deep depression on the 7th, andan almost arcuate, very broad, moderately deep emargination on the 8th ventrite; 9th tergum(Fig. 39B) with ventral apophyses moderately long; 9th ventrite (Fig. 39D) with macrosetae
long, apicolateral teeth very long, thin, very acute, apicolateral setae moderately long; 10th tergum (Fig. 39B) rouneded posteriorly. Aedeagus (Fig. 39E) with median lobe elongate, weakly
constricted around the apical 2/5, then becoming broader apicad to apicolateral corners, with ashort apicomedian cusp; apical sclerotized area nearly triangular, weakly bisinuate laterally.
Endophallus (Fig. 39E) with copulatory tube very short, main tube broad at base, very thin at
apex; dorsolateral bands very thin; expulsion hooks (Fig. 39F) slightly small, each with anterior
plate distinctly turning almost laterally; ventromedian bands each long, moderately broad. Parameres (Fig. 39E) each obtusely pointed at apex; apical area hardly swollen at base, mesially with
11 to 12 setae.
Female: Eighth ventrite almost rounded posteriorly or obtuse posteromedially; gonocoxites(Fig. 39G) each with apicolateral tooth long, acute, apicolateral setae long. Spermatheca (Fig.
39C) with capsule very small, almost rounded apically; striped duct very long, moderately thickto thick; duct very long, thin to moderately thick, very loosely coiled for the most part; glandsmall, with opening located on the lateral side of duct a little proximal from the last 3rd turn;basal valve very thin, short; basal pouch very large, subconical.
Biology and ecology. The beetles of S. brevispinus inhabit leaf litter heaped in the naturalforests of mountainous regions.
Remarks. S. brevispinus is probably allied to S. cinanomontis, but it is separable from the latter species by the aedeagal median lobe much broader at the apicolateral corners (Fig. 39E), with
its apical sclerotized area having a shorter apicomedian cusp (Fig. 39E), the copulatory tube
shorter (Fig. 39E), and the endophallic expulsion hook broader, with its anterior plate distinctly
turning almost laterally (Fig. 39F).
Stenus incalcaratus Naomi(Figs. 40A–I, 132H)
Stenus toshiharui Naomi, 1990: 46 (in part).
Stenus incalcaratus Naomi, 2015: 19.
Type material examined. Holotype: ♂ (CBM), Amagi Pass, Yugashima, Shizuoka Pref., 12.
xi. 2000, T. Watanabe leg. Paratypes: 1 ♂1 ♀ (paratypes of S. toshiharui), Amagi Pass, Izu Peninsula, Shizuoka Pref., 23. vii. 1982, S. Naomi leg.
Distribution. Japan: Honshu (Shizuoka Pref.).
Redescription. Male and female: Body 3.8–3.7 mm (fore body 1.5–1.9 mm) in length. Body
weakly to moderately shining; head black, sometimes with median area dark red to dark brown;
pronotum and elytra reddish brown; abdomen reddish brown to brown or dark red; labrum reddish orange; antennae and legs yellowish brown to reddish brown. Body with punctures round to
elliptical, small to moderately large, and also pronotum partially with subrugose punctures andelytra partially with large, subrugose punctures. Head moderately concave, with a pair of longitudinal-oblique furrows; antennae moderately long, very thin; pronotum with surface strongly
uneven, with a median longitudinal furrow distinct; elytra with surface uneven; abdomen subcylindrical, subparallel-sided; lateroventrites and tergoventral sutures lost.

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Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

Fig. 40. Stenus incalcaratus Naomi (Shizuoka: Mt. Amagi). A, aedeagus; B, 9th ventrite of male; C, 9th and 10th
terga of male; D, posterior part of gonocoxite; E, 8th ventrite of male; F, spermatheca; G, endophallic expulsion hooks; H, copulatory tube; I, ventromedian bands (outthrusted condition). Scale 1: 0.1 mm for A; scale 2:
0.2 mm for B, E, 0.1 mm for F–I; scale 2: 0.2 mm for C, 0.05 mm for D.

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101

Male: Abdomen modiﬁed with a very shallow depression on the 7th, and an arcuate, broad,shallow emargination on the 8th ventrite (Fig. 40E); 9th tergum (Fig. 40C) with ventral apophyses short; 9th ventrite (Fig. 40B) elongate, with apicolateral teeth very long, very acute, apicolateral setae moderately long; 10th tergum (Fig. 40C) entire. Aedeagus (Fig. 40A) with median lobe
obtusely angulate at apicolateral corner, obtuse at apex; apical sclerotized area hardly developed.
Endophallus with copulatory tube (Fig. 40H) with basal chamber large, ovoidal, main tube elongate-rhombic in shape, apically with a very thin needle; expulsion hooks (Fig. 40G) very small,each with anterior plate acutely pointed at anterior tip, posterior plate minutely pointed at posterolateral part; ventromedian bands (Fig. 40I) slender. Parameres (Fig. 40A) very long, eachnarrowly rounded apically; apical area very long, slightly swollen laterally, mesially with 10 to
13 setae.
Female: Eighth ventrite acutely pointed posteromedially with a very short cusp; gonocoxites
each with apicolateral tooth very long, very acute, apicolateral setae very long. Spermatheca(Fig. 40F) with capsule elongate; striped duct short, moderately thick; duct very long, very thin,with distal part moderately broad, tightly coiled; basal duct elongate-conical in shape, strongly
sclerotized.
Biology and ecology. The beetles of S. incalcaratus inhabit leaf litter heaped in the naturalforests of a mountainous region.
Remarks. S. incalcaratus is allied to S. inamatus, but it is separable from the latter by theaedeagal median lobe obtusely angulate at the apicolateral corners, with its apical sclerotizedarea very thin (Fig. 40A), the copulatory tube elongate-rhombic in shape (Fig. 40H), and theendophallic expulsion hook much smaller, with its posterior plate (Fig. 40G) much shorter.
Stenus inamatus Puthz(Figs. 41A–H, 132I)
Stenus inamatus Puthz, 1993: 149; Herman, 2001: 2227; Naomi & Puthz, 2013: 142.
Type material examined. Holotype: ♂ (NHMG), Shiga Highland (1,500 m), Jyoshin-etsu
National Park, Nagano Pref., 23. vii. 1980, I. Löbl leg. Paratype: 1 ♀, same data as holotype.
Other material examined. [HONSHU]: 2 ♂, Kaikake, Yuzawa-machi, Niigata Pref., 23. vi.
1996, K. Haga leg.; 1 ♂, Okutadami, Fukushima Pref., 23. vii. 1987, S. Nomura leg.; 2 ♂, Yagizawa, Yuzawa-machi, Niigata Pref., 20. v. 1995, K. Haga leg.
Distribution. Japan: Honshu (Niigata and Nagano Prefs.).
Redescription. Male and female: Body 3.3–3.8 mm (fore body 1.7–1.9 mm) in length. Body
weakly shining; head black; pronotum and elytra dark red; abdomen reddish brown to brown or
black; labrum reddish brown to dark reddish brown; antennae and legs yellowish brown. Body
with punctures round to ovoidal, small to moderately large, and also pronotum partially withcoarse punctures and elytra partially with large, subrugose punctures. Head shallowly to moderately concave, with a pair of longitudinal-oblique or mesially-curved furrows; antennae short,thin; pronotum with surface uneven, with a median longitudinal furrow hardly developed to very
indistinct; elytra with surface slightly uneven to uneven; abdomen subcylindrical, slightly tapering posteriorly; lateroventrites lost, tergoventral sutures sometimes present, very thin.
Male: Abdomen (Fig. 41D) modiﬁed with an arcuate, moderately deep emargination on the
8th ventrite; 9th tergum (Fig. 41A) with ventral apophyses slightly short; 9th ventrite (Fig. 41B)
with apicolateral teeth moderately long, acute, apicolateral setae slightly short; 10th tergum (Fig.

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Fig. 41. Stenus inamatus Puthz (Niigata: A, G, H, Kaikake; Nagano: B–F, Shiga Highland). A, 9th and 10th tergaof male; B, 9th ventrite of male; C, posterior part of gonocoxite; D, 8th ventrite of male; E, aedeagus; F, spermatheca; G, copulatory tube; H, endophallic expulsion hooks. Scale 1: 0.1 mm for A, 0.05 mm for G; scale 2:
0.2 mm for B, E; scale 3: 0.1 mm for C, 0.2 mm for F, 0.05 mm for H; scale 4: 0.3 mm for D.

The Steninae of Japan Part 3

10341A) very shallowly emarginate posteromedially. Aedeagus (Fig. 41E) with median lobe elongate, well-rounded apically; apical sclerotized area not developed. Endophallus (Fig. 41E) withcopulatory tube (Fig. 41G) moderately long, attenuate, moderately curved; dorsolateral bands
thin; expulsion hooks (Fig. 41E, H) thin, each with anterior plate almost triangular, much smaller
than posterior plate; ventromedian bands short, thin. Parameres (Fig. 41E) long, thick, each narrowly rounded apically; apical area very long, mesially with 16 setae of various length.
Female: Eighth ventrite minutely pointed posteromedially; gonocoxites (Fig. 41C) each withapicolateral tooth long, acute, apicolateral setae very long. Spermatheca (Fig. 41F) with capsulerounded apically; striped duct moderately long, thick; duct slightly short, thick, loosely coiled
with 6 turns; basal valve short; basal duct moderately long.
Biology and ecology. The beetles of S. inamatus inhabit leaf litter heaped in the natural forests of mountainous regions.
Remarks. S. inamatus is allied to S. inaestimatus, but it is separable from the latter species by
the aedeagal median lobe broader at the apical part, with its apical sclerotized area lost (Fig.
41E), the endophallic expulsion hook present (Fig. 41H), the paramere thicker, with its apicalarea shorter (Fig. 41E), and the spermatheca with its duct thicker (Fig. 41F).
Stenus inaestimatus Puthz(Fig. 42A–H)
Stenus inaestimatus Puthz, 1993: 154; Herman, 2001: 2227; Naomi & Puthz, 2013: 143.
Type material examined. Holotype: ♂ (NHMG), Arimine (1,150 m), Kamini(i)kawa, Toyama
Pref., 29. vii. 1980, I. Löbl leg. Paratype: 1 ♀, same data as holotype.
Other material examined. [HONSHU]: 1 ♂, Nakao, Mt. Yakedake, Takayama City, Gifu
Pref., 2. vi. 2008, K. Mizuno leg.; 1 ♂, Nomugi Pass, Nagawa Vil., Nagano Pref., 8. viii. 1996, T.
Kishimoto leg.; 1 ♂, Shimajima Val., Nagano Pref., 10. vii. 1966, Y. Watanabe leg.
Distribution. Japan: Honshu (Nagano, Gifu and Toyama Prefs.).
Redescription. Male and female: Body 2.9–3.6 mm (fore body 1.6–1.7 mm) in length. Body
weakly shining; head black; pronotum and elytra dark red; abdomen dark reddish brown toalmost black; labrum reddish brown; antennae and legs yellowish brown to reddish brown. Body
with punctures round to ovoidal, small to moderately large, and also pronotum partially withcoarse punctures and elytra partially with large, subrugose punctures. Head moderately concave,with a pair of longitudinal-oblique furrows; antennae short to moderately long, very thin to thin;pronotum with surface slightly uneven to uneven, with a median longitudinal furrow indistinct;
elytra with surface even to uneven; abdomen subcylindrical, subparallel-sided; lateroventrites
and tergoventral sutures lost.
Male: Abdomen (Fig. 42C) modiﬁed with a ﬂat area or a very shallow or shallow depression
on the 7th, and an arcuate emargination on the 8th ventrite; 9th tergum (Fig. 42A) with ventral
apophyses moderately long; 9th ventrite (Fig. 42B) with macrosetae long, apicolateral teeth moderately long, very acute, apicolateral setae short; 10th tergum (Fig. 42A) shallow emarginate posteromedially. Aedeagus (Fig. 42H) with median lobe slender, narrowly rounded apically; apicalsclerotized area subtriangular, basally with an arcuate notch. Endophallus (Fig. 42H) with copulatory tube (Fig. 42E) straight, attenuate; expulsion hooks lost; ventromedian bands moderately
long, thin. Parameres (Fig. 42H) long, each weakly incurved, narrowly rounded apically; apicalarea extremely long, almost as long as pedicel, mesially with 11 to 12 setae.

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Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

Fig. 42. Stenus inaestimatus Puthz (Nagano: A, E, Nomugi Pass; Toyama: B, D, F–H, Arimine; Nagano: C,
Shimajima). A, 9th and 10th terga of male; B, 9th ventrite of male; C, 7th and 8th ventrites of male; D, spermatheca; E, copulatory tube; F, posterior part of 8th ventrite of female; G, posterior part of gonocoxite; H,aedeagus. Scale 1: 0.1 mm for A; scale 2: 0.1 mm for B, H; scale 3: 0.3 mm for C; scale 4: 0.1 mm for D; scale
5: 0.05 mm for E, 0.2 mm for F, 0.1 mm for G.

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105

Female: Eighth ventrite (Fig. 42F) obtuse posteromedially; gonocoxites (Fig. 42G) each withapicolateral tooth moderately long, acute, apicolateral setae very long. Spermatheca (Fig. 42D)
with capsule very small; striped duct moderately long, thick; duct short, moderately thick tothick, tightly coiled; basal valve short; basal duct long.
Biology and ecology. The beetles of S. inaestimatus inhabit leaf litter heaped in the naturalforests of mountainous regions.
Remarks. S. inaestimatus is allied to S. inamatus, but it is separable from the latter species by
the aedeagal median lobe narrower at the apical part, with its apical sclerotized area subtriangular (Fig. 42H), the endophallic expulsion hook absent (Fig. 42H), the paramere thinner, with its
apical area longer (Fig. 42H), and the spermatheca with its duct thinner (Fig. 42D).
Stenus sicyoideus Naomi, Nomura & Puthz sp. nov.
(Fig. 43A–F)
Type material examined. Holotype: ♂ (KUMF), Mt. Kisokomagadake (1,550 m), Nagano
Pref., 21. ix. 1996, T. Kishimoto leg.
Distribution. Japan: Honshu (Nagano Pref.).
Description. Male: Body 4.3 mm (fore body 1.9 mm) in length. Body moderately shining;head black; pronotum and elytra reddish brown; abdomen dark reddish brown; labrum reddish
brown; antennae and legs reddish brown. Body with punctures round to elliptical, small to moderately large, and also pronotum partially with coarse punctures and elytra (Fig. 43E) partiallywith large, coarse punctures. Head moderately concave, with a pair of longitudinal-oblique furrows; antennae moderately long, very thin; pronotum with surface slightly uneven, with a
median longitudinal furrow indistinct; elytra with surface slightly uneven; abdomen subcylindrical, subparallel-sided; lateroventrites lost, tergoventral sutures each very thin, running in a superﬁcial way.
Abdomen (Fig. 43F) modiﬁed with an arcuate emargination on the 8th ventrite; 9th tergum(Fig. 43B) with ventral apophyses long; 9th ventrite (Fig. 43C) with macrosetae long, apicolateral teeth long, very acute, apicolateral setae moderately long; 10th tergum (Fig. 43A) almost
rounded posteriorly. Aedeagus (Fig. 43A) with median lobe elongate, rounded apically; apicalsclerotized area narrow, almost bell-shaped, apically with several, very short setae, basimediallywith an arcuate notch. Endophallus (Fig. 43A) with copulatory tube large, gourd-shaped; expulsion hooks (Fig. 43D) moderately large, degenerated into a pair of submembranous plates, eachhook with anterior plate divided into 2 subplates by a transverse suture; ventromedian bands
probably fused into a slightly short, broad band. Parameres (Fig. 43A) long, each pointed atapex; apical area extremely long, broad almost dorsoventrally, about as long as pedicel, mesiallywith 14 to 16 setae of various length.
Female: Unknown.
Biology and ecology. The beetle of S. sicyoideus inhabits leaf litter heaped in the natural forest of a high mountainous region.
Remarks. S. sicyoideus is allied to S. keman, but it is separable from the latter species by theaedeagal median lobe narrower at the apical part (Fig. 43A) and the endophallic expulsion hookwith its anterior plate distinct in outline (Fig. 43D), and the paramere shorter, with its apical area
broader dorsoventrally (Fig. 43A).
Etymology. The speciﬁc epithet of this new species is derived from the Latin adjective sicyoideus, which means ʻgourd-shapedʼ. The beetle of this species has the gourd-shaped copulatory

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Fig. 43. Stenus sicyoideus Naomi, Nomura & Puthz sp. nov. (Nagano: Mt. Kisokomagadake). A, aedeagus; B, 9th
and 10th terga of male; C, 9th ventrite of male; D, endophallic expulsion hooks; E, left elytron; F, 8th ventriteof male. Scale 1: 0.1 mm for A, 0.2 mm for F; scale 2: 0.2 mm for B, C, 0.05 mm for D; scale 3: 0.3 mm for E.

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tube of endophallus.
Stenus keman Naomi(Figs. 44A–G, 132J)
Stenus keman Naomi, 1990: 45; Herman, 2001: 2245; Naomi & Puthz, 2013: 142.
Stenus haniwa Hromádka, 1990: 55.
Type material examined. Holotype of S. keman: ♂ (KUF), Nishihotakaguchi, Gifu Pref., 11.
vi. 1980, S. Naomi leg. Paratypes of S. keman: 4 ♂1 ♀, same data as holotype; 1 ♂, Shinhotaka
Spa, Gifu Pref., 10–12. vi. 1980, S. Naomi leg.
Holotype of S. haniwa: ♂ (AACO), Shiga (Highland) (1,500 m), Nagano Pr., Japan, 23. vii.
1980, A. Z. Smetana leg.
Other material examined. [HONSHU]: 1 ♂1 ♀, Shaka-shindo, Mt. Hakusan-shakadake, Mts.
Hakusan, Ishikawa Pref., 12. vii. 2002, H. Hoshina leg.; 1 ♂, Nabetani, Tatunokuchi-cho,Ishikawa Pref., 29. iv. 1995, Y. Sugie leg.; 1 ♂1 ♀, Mt. Yatsu, Chino City, Nagano Pref., 19. viii.
1996, S. Nomura leg.; 1 ♂1 ♀, Utukushinomori, Kiyosato, Yamanashi Pref., 3. v. 2002, S.
Nomura leg.; 1 ♂1 ♀, Mikuni Pass, Ohtaki Vil., Saitama Pref., 30. x. 1999, S. Nomura leg.
Distribution. Japan: Honshu (Chubu and Kanto Districts).
Redescription. Male and female: Body 3.7–4.3 mm (fore body 1.7–2.0 mm) in length. Body
moderately shining; head black; pronotum and elytra reddish brown; abdomen dark reddish
brown; labrum reddish brown; antennae and legs yellowish brown to reddish brown. Body with
punctures round to ovoidal, small to moderately large, and also pronotum partially with coarse tosubrugose punctures and elytra partially with large, coarse to subrugose punctures. Head moderately concave, with a pair of longitudinal-oblique furrows; antennae moderately long, very thin
to thin; pronotum with surface slightly uneven to uneven, with a median longitudinal furrow distinct; elytra with surface uneven; abdomen subcylindrical, subparallel-sided; lateroventrites andtergoventral sutures lost.
Male: Abdomen (Fig. 44E) modiﬁed with a very shallow depression on the 7th, and a moderately broad, subtriangular emargination on the 8th ventrite; 9th tergum (Fig. 44A) with ventral
apophyses moderately long; 9th ventrite (Fig. 44C) with macrosetae long, apicolateral teeth long,very acute, apicolateral setae long; 10th tergum (Fig. 44A) almost rounded posteriorly. Aedeagus(Fig. 44B, F) with median lobe elongate, broadest at apicolateral corners, well-rounded apically;
apical sclerotized area nearly semicircular, very broad, ventrally swollen, basimedially with amore or less narrow, arcuate, U-shaped or pentagonal notch. Endophallus (Fig. 44B) with copulatory tube gourd-shaped, slightly short to long, main tube ovoidal at base, attenuate apically;
expulsion hooks with anterior plates indistinct in outline, posterior plates well-sclerotized, connected anteromesially, with the hook of each side gingko-leaf-like (Fig. 44B), elongate-triangularin shape, etc.; visible ventromedian bands moderately long and broad in stored condition, or very
long (Fig. 44B) when they are pulled out while the copulatory tube is completely outthrusted.
Parameres (Fig. 44F) very long, each acutely pointed at apex; apical area extremely long, very
thin, longer than pedicel, more or less serrate along ventral rim, mesially with 12 setae of various
length.
Female: Eighth ventrite obtuse posteromedially; gonocoxites (Fig. 44G) each with apicolateral tooth very long, very acute, apicolateral setae very long. Spermatheca (Fig. 44D) with capsule long, rounded apically; striped duct moderately long, thick; duct short, moderately thick to108

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Fig. 44. Stenus keman Naomi (Nagano: A, Mt. Yatsu; Saitama: B, Mikuni Pass; Gifu: C–G, Nishihotakaguchi).
A, 9th and 10th terga of male; B, apical part of aedeagus and outthrusted endophallus; C, 9th ventrite of male;D, spermatheca; E, 7th and 8th ventrites of male; F, aedeagus; G, posterior part of gonocoxite. Scale 1: 0.2 mm
for A, C, F, 0.1 mm for B, D, G; scale 2: 0.3 mm for E.

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thick, with 4 turns; basal valve short; basal duct moderately long.
Biology and ecology. The beetles of S. keman inhabit leaf litter heaped in the natural forestsof mountainous to high mountainous regions.
Remarks. S. keman is widely distributed in the Chubu District, Honshu, and we found that
there are considerable variations regarding the shape of aedeagal median lobe, the structure ofendophallic expulsion hooks, etc. First, the apical sclerotized area of median lobe has basimedially a more or less narrow, arcuate or U-shaped notch in the males (e.g., Nishihotakaguchi, Gifu
Pref.; Mt. Yatsu, Nagano Pref.), while it has a pentagonal notch in a male (Mt. Hakusan, Fukui
Pref.). The shape of expulsion hook is diﬃcult to grasp, because the anterior plate is submembranous so that the outline of expulsion hook cannot be depicted and thus described (see also thesubmembranous expulsion hook of S. sicyoideus; Fig. 43D). However, what we can regard as theposterior plate of expulsion hook is certainly diﬀerent in shape among the males observed in thepresent study. Thus, the variations are secondly recognized as follows: The posterior plate is agingko-leaf-like in the male (e.g., Mikuni Pass, Saitama Pref.; Kiyosato, Yamanashi Pref.), while
it is elongate-triangular in shape in the male (Mt. Hakusan, Fukui Pref.). There are also othersuch variations as the length of copulatory tube and the degree of serration at the ventral rim of
the apical area of paramere among the males collected from various localities.
Most of these variations seem to be obviously infraspeciﬁc among the local populations of S.
keman because they are not distinctive so that they will not be considered to be the key characters of independent species. However, the male from Mt. Hakusan, Fukui shows certainly several
unique conditions of taxonomically important characters as described above. This suggests that
the Stenus local populations of Mt. Hakusan will be recognized as a diﬀerent species from S.
keman when performing the further detailed studies. However, we are not to here describe themas new to science because the specimens examined in the present study are not enough for doingit.
S. keman is allied to S. sicyoideus, but it is separable from the latter species by the aedeagal
median lobe broader at the apical part (Fig. 44B) and the endophallic expulsion hook with its
anterior plate indistinct in outline (Fig. 44B), and the paramere longer, with its apical area narrower dorsoventrally (Fig. 44F).
Etymology. The speciﬁc epithet of this species is derived from the Japanese name of theﬂowing plant genus Lamprocapnos, keman-sou.
Stenus hoshinai Naomi(Fig. 45A–I)
Stenus hoshinai Naomi, 2012: 299; Naomi & Puthz, 2013: 144.
Type material examined. Holotype: ♂ (CBM), Chiburi-oné, Mt. Hakusan, Ishikawa Pref., 29.
vi. 2002, H. Hoshina leg. Paratypes: 8 ♂3 ♀, same data as holotye; 1 ♂, same locality, 1. viii.
2002, H. Hoshina leg.
Distribution. Japan: Honshu (Ishikawa Pref.).
Redescription. Male and female: Body 3.6–4.0 mm (fore body 1.6–1.9 mm) in length. Headweakly shining; head black; pronotum and elytra dark red; abdomen dark reddish brown to darkbrown; labrum reddish brown to dark red; antennae yellowish brown to reddish brown, sometimes with 1st and 2nd segments brown; legs reddish brown. Body with punctures round to ovoidal, small to moderately large, and also pronotum partially with coarse punctures and elytra par-

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Fig. 45. Stenus hoshinai Naomi sp. nov. (Ishikawa: Mt. Hakusan). A, posterior part of 7th and 8th ventrites ofmale; B, aedeagus; C, 9th ventrite of male; D, 9th and 10th terga of male; E, gonocoxite; F, copulatory tube;
G, endophallic expulsion hooks; H, spermatheca. Scale 1: 0.25 mm for A; scale 2: 0.2 mm for B–D, 0.1 mm for
E–H; scale 3: 0.2 mm for I.

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111

tially with large, subrugose punctures. Head shallowly to moderately concave, with a pair of
longitudinal-oblique furrows or depressions; antennae short to moderately long, very thin; pronotum with surface weakly uneven to uneven, with a median longitudinal furrow hardly developed
to very indistinct; elytra with surface almost even to slightly uneven or uneven; abdomen subcylindrical, slightly tapering posteriorly to subparallel-sided; lateroventrites lost, tergoventrite
sutures obsolete.
Male: Abdomen (Fig. 45A) modiﬁed with a ﬂat area on the 6th, a shallow depression on the
7th, and an arcuate emargination on the 8th ventrite; 9th tergum (Fig. 45D) with ventral apophyses long; 9th ventrite (Fig. 45C) with apicolateral teeth short, very acute, apicolateral setae short;
10th tergum (Fig. 45D) almost rounded posteriorly. Aedeagus (Fig. 45B) with median lobe
broad, well-rounded at apicolateral corners, sparsely covered with very small pores on the margin of posterior part, with a moderately long, pointed apicomedian cusp; apical sclerotized area
only weakly developed. Endophallus (Fig. 45B) with copulatory tube (Fig. 45F) having basal
chamber large, ovoidal, main tube short, elongate-conical in shape; expulsion hooks (Fig. 45G)
atrophied into a pair of very small sclerites; ventromedian bands slightly short, each moderately
broad at the posterior rim. Parameres (Fig. 45B) each acutely pointed at apex, with pedicel
sparsely covered with very small pores at the middle; apical area moderately long, distinctly
swollen mesially at base, mesially also with 9 to 11 setae.
Female: Eighth ventrite (Fig. 45I) obtuse posteromedially; gonocoxites (Fig. 45E) each withapicolateral tooth very long, very acute, apicolateral setae very long. Spermatheca (Fig. 45H)with capsule long, rounded apically; striped duct very short, moderately thick; duct moderately
long, moderately thick to thick, almost loosely coiled; basal valve moderately long; basal duct
long, thin.
Biology and ecology. The beetles of S. hoshinai inhabit leaf litter heaped in the natural forests of a high mountainous region.
Remarks. S. hoshinai is allied to S. regularis, but it is clearly separable from the latter species
by the aedeagal median lobe broader, with its posterior part becoming narrower apicad to the apicolateral corners (Fig. 45B), the copulatory tube with its main tube elongate-conical in shape(Fig. F), the parameres shorter (Fig. 45B), and the spermatheca with its capsule and stripe ductthinnr (Fig. 45H).
Etymology. This species is named after Dr. Hideto Hoshina (Fukui University) who studies
the Staphylinidae (Scydmaeninae) and some other Staphylinoid groups.
Stenus regularis Naomi & Y. Watanabe(Fig. 46A–G)
Stenus regularis Naomi & Watanabe, 2015: 108.
Type material examined. Holotype: ♂ (TUAA), Shirakawa Vil, Gifu Pref., 28. vii. 1986, K.
Suzuki leg. Paratype: 1 ♀ (TUAA), same data as holotype.
Distribution. Japan: Honshu (Gifu Pref.).
Redescription. Male and female: Body 3.5–4.1 mm (fore body 1.7–1.9 mm) in length. Body
weakly shining; head black; pronotum and abdomen dark brown; elytra reddish brown; labrum
reddish brown to dark red; antennae and legs reddish brown. Body with punctures round to elliptical, small to moderately large, and also pronotum partially with coarse to subrugose puncturesand elytra partially with large, subrugose punctures. Head moderately concave, with a pair of

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Fig. 46. Stenus regularis Naomi & Y. Watanabe (Gifu: Shirakawa). A, spermatheca; B, 9th and 10th terga of
male; C, endophallus; D, aedeagus; E, 9th ventrite of male; F, gonocoxites; G, posterior part of 8th ventrite of
male. Scale 1: 0.2 mm for B, D–F and 0.1 mm for A, C; scale 2: 0.2 mm for G.

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longitudinal-oblique furrows; pronotum slightly uneven, with a median longitudinal depression
indistinct; elytra with surface uneven; Abdomen subcylindrical, subparallel-sided; lateroventrites
and tergoventrite sutures lost.
Male: Abdomen modiﬁed with a very shallow depression on the 7th, and a broad, moderately
deep emargination on the 8th ventrite (Fig. 46G); 9th tergum (Fig. 46B) with ventral apophyses
slightly short; 9th ventrite (Fig. 46E) with apicolateral teeth each long, very acute; 10th tergum(Fig. 46B) almost rounded posteriorly. Aedeagus (Fig. 46D) with median lobe well-rounded atapicolateral corners, acutely pointed at apex; apical sclerotized area almost broad-triangular inshape. Endophallus (Fig. 46C) with copulatory tube having main tube thick, baculiform, pointed
at apex; expulsion hooks atrophied into a pair of small, thin, crescent rods which are connectedeach other; ventromedian bands each slightly short, moderately thick. Parameres (Fig. 46D) long,acutely pointed at apex; apical part long, moderately thick at base, mesially with 11 to 13 setae ofvarious length.
Female: Eighth ventrite obtuse posteromedially; gonocoxites (Fig. 46F) each with apicolateral tooth moderately long, acute, apicolateral setae very long. Spermatheca (Fig. 46A) with capsule very large; striped duct short, thick to very thick; duct short, moderately thick to thick, with
5 turns; gland spherical, located on the lateral side of duct between the 4th and 5th turns; basal
valve moderately long; basal duct long; basal pouch low cone-shaped, membranous.
Biology and ecology. The beetles of S. regularis inhabit leaf litter heaped in the natural forests of a mountainous region.
Remarks. S. regularis is allied to S. hoshinai, but it is clearly separable from the latter species
by the aedeagal median lobe narrower, with its posterior part subparallel-sided except for the apical part (Fig. 46D), the copulatory tube with its main tube subparallel-sided except for the apicalpart (Fig. 46C), the parameres longer (Fig. 46D), and the spermatheca with its capsule and stripe
duct thicker (Fig. 46A).
Species unit 3 of the cephalotes-subgroup
Key to the Japanese species of the cephalotes-subgroup (3)This is a key for a unit of Stenus-species (8 species) beginning with S. cohaereus and almost
adequately diagnosed with the combination of following character conditions: Aedeagal median
lobe usually broad, broad even at apicolateral corners (Fig. 48A), and often subtruncate at apex
(Fig. 48A); endophallic expulsion hook with anterior plate always narrower than posterior plate(Fig. 51H); paramere with pedicel often thin (Fig. 51F) to very thin (Fig. 50B).
Distribution. Japan: Honshu (Chubu, Kinki and Chugoku Districts).
1(4)
2(3)

3(2)

4(1)
5(8)

Male: Aedeagal paramere with apical area falcate or slightly falcate.
Male: Aedeagal median lobe with an elongate-triangular, ﬂat apical sclerotized area (Fig.
47D); endophallic expulsion hooks separated each other (Fig. 47F)....................................
................................................................... S. cohaerens Naomi, Nomura & Puthz sp. nov.
Male: Aedeagal median lobe apically with an arcuate, very broad emargination (Fig.
48A); endophallic expulsion hooks broadly fused each other (Fig. 48F) .............................
.................................................................................................S. warabi Naomi & Nomura
Male: Aedeagal paramere with apical area not falcate.
Male: Aedeagal paramere with apical area mesially having a larger number of setae only

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in the basal 2/3 or in the apical part.
Male: Endophallic expulsion hook with posterior plate almost rounded or obtuse at apex
(Fig. 49D, N); aedeagal paramere rounded apically (Fig. 49D) ............... S. himiko Naomi
7(6) Male: Endophallic expulsion hook with posterior plate strongly protruding posterolaterally (Fig. 51H); parameres (Fig. 51F) each very acutely pointed at apex ............................
............................................................................................................S. aoi Naomi & Puthz
8(5) Male: Aedeagal paramere with apical area mesially having a smaller number of setae
only at the middle.
9(12) Male: Aedeagal median lobe subtruncate apically; endophallic expulsion hook with posterior plate obliquely truncate or subtruncate posteriorly.
10(11) Male: Aedeagal median lobe with a very small (Fig. 50C) or small (Fig. 50B), subtriangular apicomedian protrusion; endophallic expulsion hook with posterior plate obliquely
truncate ((Fig. 50K) .................................... S. subulifer Naomi, Nomura & Puthz sp. nov.
11(10) Male: Aedeagal median lobe with 4 very small, equidistantly located teeth along posterior
margin (Fig. 54D); endophallic expulsion hook with posterior plate subtruncate posteriorly (Fig. 54E)..............................................S. gloriﬁcus Naomi, Nomura & Puthz sp. nov.
12(9) Male: Aedeagal median lobe broad-subtriangular in shape at apical part; endophallic
expulsion hook with posterior plate rounded posteriorly.
13(14) Male: Aedeagal median lobe with apical sclerotized area comprising narrow rim, shortly
separated at the middle (Fig. 52A); copulatory tube with main tube thick at base and thenattenuate and not curved apicad (Fig. 52A) ..................................S. intrarius Naomi & Ito
14(3) Male: Aedeagal median lobe with apical sclerotized area subrhombic, solid (Fig. 53C);
copulatory tube with main tube almost attenuate, slightly bent near the apical 1/3 (Fig.
53G) .......................................................................................................... S. shojiroi Naomi
6(7)Stenus cohaerens Naomi, Nomura & Puthz sp. nov.
(Fig. 47A–G)
Stenus shuheii Naomi, 1990a: 2 (in part).
Type material examined. Holotype: ♂ (paratype of S. shuheii; KUMF), Onzui Valley, Hyogo
Pref., 6. vi. 1984, S. Nomura leg. Paratypes: 1 ♂2 ♀, near Ningyôsen, Kagamino-cho, Okayama
Pref., 26. vi. 2005, O. Yamaji leg.
Other material examined. [HONSHU]: 1 ♀, Kizetsu Valley, Tanabe City, Wakayama Pref.,15. vii. 1999, V. Puthz leg.
Distribution. Japan: Honshu (Wakayama, Hyogo and Okayama Prefs.).
Description. Male and female: Body 3.6–3.9 mm (fore body 1.7–1.8 mm) in length. Body
moderately shining; head black; pronotum and elytra reddish brown to dark reddish brown;
abdomen reddish brown to dark reddish brown or almost black; labrum reddish brown to dark
reddish brown; antennae and legs yellow brown to reddish brown. Body with punctures round to
elliptical, small to moderately large, and also pronotum partially with coarse to subrugose punctures and elytra partially with large, subrugose punctures. Head moderately concave, with a pairof longitudinal-oblique furrows; antennae short to moderately long, very thin; pronotum withsurface slightly uneven, with a median longitudinal furrow indistinct; elytra with surface almost
even to slightly uneven; abdomen subcylindrical, thin to moderately thick, slightly tapering pos-

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Fig. 47. Stenus cohaerens Naomi, Nomura & Puthz sp. nov. (Okayama: Kagamino). A, spermatheca; B, 9th and10th terga of male; C, 6th to 8th ventrites of male; D, aedeagus; E, posterior part of gonocoxite; F, apical partof aedeagal median lobe with its outthrusted endophallus, G, 9th ventrite of male. Scale 1: 0.1 mm for A, E, F,
0.2 mm for B, D; scale 2: 0.3 mm for C; scale 3: 0.1 mm for G.

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Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

teriorly; lateroventrites and tergoventral sutures lost.
Male: Abdomen (Fig. 47C) modiﬁed with a moderately deep depression on the 6th, a deep
depression (whose posterior protruded part is almost transverse-trapezoidal in shape) on the 7th,
and a very deep, V-shaped emargination on the 8th ventrite; 9th tergum (Fig. 47B) with ventral
apophyses short; 9th ventrite (Fig. 47G) with macrosetae short, apicolateral teeth slightly short,very acute, apicolateral setae moderately long; 10th tergum (Fig. 47B) very shallowly emarginate
posteromedially. Aedeagus (Fig. 47D) with median lobe moderately broad; apical sclerotizedarea ﬂat, elongate-triangular in shape. Endophallus (Fig. 47F) with copulatory tube long, lanceolate at apex; dorsolateral bands thin; expulsion hooks strongly sclerotized, elongate-subtriangularin shape, each deeply emarginate posteriorly; ventromedian bands separated near the posteriorrims, each broad, but their anterior parts fused to form a very broad band?; a pair of small sclerites located dorsally from the expulsion hooks. Parameres (Fig. 47D) each very acutely pointed
at apex; apical area moderately long, slightly falcate, mesially with 8 to 10 setae.
Female: Eighth ventrite almost rounded posteriorly or obtuse posteromedially; gonocoxites(Fig. 47E) each with apicolateral tooth moderately long, acute, apicolateral setae very long. Spermatheca (Fig. 47A) with capsule absent; striped duct long, thick; duct slightly short, moderately
thick to thick, loosely coiled in the middle, with 6 turns; gland almost spherical, moderately
large, covered densely with very thin ciliae, with opening located on the anterior side of duct
near the 3rd turn; basal valve very short; basal duct short, a little broader than basal valve.
Biology and ecology. The beetles of S. cohaerens inhabit leaf litter heaped in the natural forests of mountainous regions.
Remarks. When S. shuheii was newly described by Naomi (1990a), 3 Stenus-beetles were
there designated as the holotype and paratype specimens. After that, it was clariﬁed in Naomi(2015) that two diﬀerent species are included in those type specimens, namely S. shuheii andanother species. The latter species is here described as new to science, by designating a paratypeof S. shuheii as its holotype.
S. cohaerens is allied to S. warabi, but it is separable from the latter species by the 6th and7th ventrites of male strongly modiﬁed with a moderately deep and deep depressions respectively (Fig. 47C), the aedeagal median lobe with its apical sclerotized area ﬂat and elongate-triangular in shape (Fig. 47D), the endophallic expulsion hooks separated (Fig. 47F), the paramere
much shorter (Fig. 47D), and the spermatheca with its duct much shorter (Fig. 47A).
Etymology. The speciﬁc epithet of this new species is derived from the Latin participle
cohaerens which means ʻcoheredʼ. The beetles of this species have the endophallic ventromedianbands with their anterior parts cohered or fused to form a broad band.
Stenus warabi Naomi & Nomura(Fig. 48A–G, 132K)
Stenus warabi Naomi & Nomura, 1990: 48; Herman, 2001: 2436; Naomi & Puthz, 2013: 144.
Type material examined. Holotype: ♀ (KUF), Mt. Hyonosen, Hyogo Pref., 5. vi. 1984, S.
Nomura leg. Paratype: ♂, same data as holotype.
Other material examined. [HONSHU]: 1 ♂, Mt. Hyonosen, Hyogo Pref., 5. vi. 1996, H.
Hoshina leg.; 1 ♀, Mt. Mimuro, Hyogo Pref., 7. vi. 1997, H. Hoshina leg.; 2 ♂1 ♀, Mt. Ushiro,
Hyogo Pref., 10. v. 1997, H. Hoshina leg.
Distribution. Japan: Honshu (Hyogo Pref.).

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Fig. 48. Stenus warabi Naomi & Nomura (Hyogo: A, E, F, Mt. Hyonosen, B, G, Mt. Mimuro, C, D, Mt. Ushiro).
A, aedeagus; B spermatheca; C, 9th and 10th terga of male; D, 9th ventrite of male; E, posterior part of 8th
ventrite of male; F, endophallic expulsion hook (fused); G, posterior part of gonocoxite. Scale 1: 0.2 mm for
A, C, D, 0.1 mm for F, G; scale 2: 0.1 mm for B; scale 3: 0.2 mm for E.

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Redescription. Male and female: Body 3.2–3.8 mm (fore body 1.5–1.8 mm) in length. Body
moderately shining; head black; pronotum, elytra and abdomen dark red to dark red near black;labrum reddish brown to dark reddish brown; antennae and legs yellow brown to reddish brown.
Body with punctures round to elliptical, small to moderately large, and also pronotum partiallywith coarse punctures and elytra partially with large, subrugose punctures. Head moderately concave, with a pair of longitudinal-oblique furrows; antennae short, very thin; pronotum with surface slightly uneven to uneven, with a median longitudinal furrow indistinct; elytra with surface
uneven; abdomen subcylindrical, thin to moderately thick, slightly tapering posteriorly to subparallel-sided; lateroventrites and tergoventral sutures lost.
Male: Abdomen (Fig. 48E) modiﬁed with an elongate, very shallow depression sometimes
on the 7th, and an arcuate, moderately deep emargination on the 8th ventrite; 9th tergum (Fig.
48C) with ventral apophyses long; 9th ventrite (Fig. 48D) with macrosetae very long, apicolateral teeth slightly short, thin, very acute, apicolateral setae moderately long; 10th tergum (Fig.
48C) entire. Aedeagus (Fig. 48A) with median lobe broad, apically with an arcuate, very broad
emargination; apical sclerotized area not developed. Endophallus (Fig. 48A) with copulatory
tube moderately long, with main tube very thick, broadest at about apical 1/3, obtusely pointed atapex; expulsion hooks (Fig. 48F) broadly fused each other, with a pair of thin anterior plates andalso posteriorly with a very large, broad emargination, the lateral edge of which slightly protrudes posteriorly; ventromedian bands very long, broad. Parameres (Fig. 48A) very long, eachvery acutely pointed at apex; apical area very long, very thin, falcate, mesially with 8 to 10 setae.
Female: Eighth ventrite almost rounded posteriorly or obtuse posteromedially; gonocoxites(Fig. 48G) each with apicolateral tooth short, falcate, acute, apicolateral setae very long. Spermatheca (Fig. 48B) with capsule short; striped duct moderately long, moderately thick; duct very
long, thin to moderately thick, strongly coiled; basal valve moderately long; basal duct short,basal pouch low-conical in shape.
Biology and ecology. The beetles of S. warabi inhabit leaf litter heaped in the natural forestsof mountainous regions.
Remarks. S. warabi is allied to S. cohaerens, but it is separable from the latter species by the
6th and 7th ventrites of male not or only weakly modiﬁed with a very shallow depression, theaedeagal median lobe posteriorly with an emargination (Fig. 48A), the endophallic expulsion
hooks fused (Fig. 48F), the paramere much longer (Fig. 48A), and the spermatheca with its ductmuch longer (Fig. 48B).
Etymology. The speciﬁc epithet of this species is derived from the Japanese name of a fern
genus Pteridium, warabi.
Stenus himiko Naomi(Figs. 49A–N, 132 L)
Stenus himiko Naomi, 1989a: 4; Herman, 2001: 2214; Naomi & Puthz, 2013: 144.
Stenus syugen Naomi, 1989a: 6. New synonym.
Type material examined. Holotype of S. himiko: ♀ (KUF), Ohdaigahara, Nara Pref., 25–26.
vi. 1981, S. Naomi leg. Paratype of S. himiko: 1 ♂, same data as holotype.
Holotype of S. syugen: ♂ (KUF), Mt. Gomanodan, Wakayama Pref., 22–23. vi. 1981, S.
Naomi leg. Paratypes of S. syugen: 1 ♂3 ♀, same data as holotype.
Other material examined. [HONSHU]: 2 ♂1 ♀, Mt. Sanjo, Tenkawa Vil., Nara Pref., 28. vi.

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Fig. 49. Stenus himiko Naomi (Nara: A, B, D, G–J, Ohdaigahara, C, Mt. Wasamata, E, Mt. Oomine, K, Mt. Sanjyo, M, Mt. Miune; Wakayama: F, L, N, Mt. Gomanodan). A, 9th ventrite of male; B, 9th and 10th terga of
male; C, I, H, spermatheca; D, aedeagus; E, F, copulatory tube; G, posterior part of gonocoxite; J, posterior
part of 8th ventrite of male; K–M, apical part of f aedeagal median lobe; N, endophallic expulsion hooks.
Scale 1: 0.2 mm for A, B, 0.1 mm for E–G, N; scale 2: 0.05 mm for C; scale 3: 0.1 mm for D, K–M, 0.05 mm
for H, I; scale 4: 0.2 mm for J.

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Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

1998, S. Nomura leg.; 1 ♂2 ♀, Mt. Oomine, Nara Pref., 1. vi. 1985, T. Ito leg.; 3 ♂, Mt. Wasamata, Kamikitayama, Nara Pref., 14–15. vi. 1997, T. Ito leg.; 3 ♂, Mt. Miune, Nara Pref., 28. v.
1994, K. Mizuno leg.; 2 ♂1 ♀, Mt. Misen, Nara Pref., 19. x. 1996, Y. Okuda leg.; 2 ♂1 ♀, Mt.
Minamimata, Ouchiyama, Mie Pref., 4. xi. 1996, K. Kanno leg.;1 ♂1 ♀, Mt. Senchiyogamine, Miyagawa Vil., Mie Pref., 2. ix. 1995, H. Yokozeki leg.; 1 ♂,Mt. Ryugadake, Daian-cho, Inabe-gun, Mie Pref., 4. xi. 1995, H. Yokozeki leg.
Distribution. Japan: Honshu (Mie, Nara and Wakayama Prefs.).
Redescription. Male and female: Body 3.1–3.5 mm (fore body 1.5–1.6 mm) in length. Body
weakly shining; head black; pronotum and elytra dark red to dark brown; abdomen dark red todark brown or almost black; labrum reddish brown; antennae and legs reddish brown. Body with
punctures round to almost round, small to moderately large, and also pronotum partially with
subrugose punctures and elytra with large, subrugose punctures. Head shallowly to moderately
concave, with a pair of narrow or broad, longitudinal-oblique furrows (or depressions); antennae
short to moderately long, thin; pronotum with surface slightly uneven to uneven, with a medianlongitudinal furrow distinct; elytra with surface uneven; hind tarsi each with 4th tarsomere
strongly bilobed; abdomen subcylindrical, subparallel-sided; lateroventrites and tergoventral
sutures lost.
Male: Abdomen (Fig. 49J) modiﬁed with a shallow emargination on the 8th ventrite; 9th tergum (Fig. 49B) with ventral apophyses thin, moderately long; 9th ventrite (Fig. 49A) with apicolateral setae very acute, apicolateral setae moderately long; 10th tergum (Fig. 49B) entire. Aedeagal median lobe (Fig. 49D) moderately broad, moderately broad and rounded even at apicolateralcorners, apicomedially with a narrow, obtuse, subtriangular apical sclerotized area. Endophallus(Fig. 49D) with copulatory tube (Fig. 49E, F) having main tube moderately long to long, curved,
with or without a small swell at apex; dorsolateral bands long, thin; explusion hooks (Fig. 49N)
each with anterior plate almost rounded anteriorly, much longer than posterior plate, posterior
plate almost rounded or obtuse at posterior tip; ventromedian bands long, very thin. Parameres(Fig. 49D) each rounded apically; apical area moderately long, elongate-spatulate in shape, mesially with 8 setae in the apical 1/2.
Female: Eighth ventrite obtuse or pointed posteromedially; gonocoxites (Fig. 49G) each withapicolateral teeth very acute, apicolateral setae very long. Spermatheca (Fig. 49C, H) with capsule developed or not; striped duct moderately long, moderately thick; duct very long, very thinbut moderately thick at the most distal and proximal parts, strongly coiled; gland almost spherical, covered with long ciliae, with opening located on the duct near the last 6th or 7th turns (Fig.
49H).
Biology and ecology. The beetles of S. himiko inhabit leaf litter heaped in the natural forestsof low mountainous to mountainous regions.
Remarks. Both S. himiko and S. syugen were described in Naomi (1989a) from the mountainous regions of Kii Peninsula, Kinki District of Honshu. They were ﬁrst classiﬁed based mainlyon the diﬀerent shape of aedeagal median lobe (Naomi, 1989a, Fig. 49D, F). However, anamount of variations are observed as follows: The shape of median lobe is varied (Fig. 49K, L,
M). The shape, length and thickness of copulatory tube are varied (Fig. 49E, G). The posterior
margin of expulsion hook is also varied from the serrate, obliquely truncate condition to the simply rounded condition. Thus, it is inadequate to consider a particular form of median lobe to be
the key character in order for separating S. himiko from S. syugen. Thus, S. syugen Naomi, 1989ais here newly placed in synonymy with S. himiko Naomi, 1989a.
S. himiko is allied to S. subulifer, but it is separable from the latter species by the aedeagal

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121

median lobe apicomedially with a subtriangular apical sclerotized area (Fig. 49D), the endophallic expulsion hook with its anterior plate shorter and almost rounded at the anterior part (Fig.
49N), and the spermatheca with its duct much longer and thinner (Fig. 49C).
Etymology. The speciﬁc epithet of this species is named after a princess of Yamataikoku,
Himiko who supposedly existed during the 3rd century in the ancient Japan.
Stenus subulifer Naomi, Nomura & Puthz sp. nov.
(Fig. 50A–K)
Type material examined. Holotype: ♂ (KUMF), Onyu Pass, Fukui Pref., 16. vi. 2018, T. Itoleg. Paratypes: 1 ♂, same data as holotype; 1 ♂2 ♀, Mt. Hira, Shiga Pref., 17. viii. 1986, T. Itoleg.
Distribution. Japan: Honshu (Fukui Pref.).
Description. Male and female: Body 2.9–3.1 mm (fore body 1.4–1.5 mm) in length. Body
moderately shining; head black; pronotum and abdomen reddish brown to dark red or almost
black; elytra yellowish brown to reddish brown; labrum reddish brown to dark reddish brown;
antennae and legs yellowish brown to reddish brown. Body with punctures round to elliptical,
small to moderately large, and also pronotum partially with coarse to subrugose punctures andelytra partially with large, coarse to subrugose punctures. Head shallowly to moderately concave,with a pair of longitudinal-oblique furrows or depressions; antennae very short to short, thin;pronotum with surface slightly uneven, with a median longitudinal depression hardly developed;
elytra with surface slightly uneven or uneven; abdomen subcylindrical, subparallel-sided; lateroventrites and tergoventrite sutures lost.
Male: Abdomen (Fig. 50J) modiﬁed with a crescent emargination on the 8th ventrite; 9th tergum (Fig. 50E) with ventral apophyses moderately long; 9th ventrite (Fig. 50D) with macrosetaevery short, apicolateral teeth short, acute, apicolateral setae short; 10th tergum (Fig. 50B) entire.
Aedeagus (Fig. 50B, C) with median lobe broad, well-rounded at apicolateral corners, subtruncate apically, with a very small (Fig. 50C) or small (Fig. 50B) subtriangular apicomedian protrusion; apical sclerotized area hardly developed. Endophallus (Fig. 50A) with copulatory tube (Fig.
50H, I) having basal chamber ovoidal, main tube moderately long, almost attenuate, with basal
tube demarcated by a line from apical tube; dorsal membrance covered densely with very small,round tubercles; expulsion hooks (Fig. 50A, K) connected by membrane along the broad range ofmesial margins of hooks, each with posterior plate obliquely truncate, with (Fig. 50A) or without(Fig. 50K) serrate posterior margin; ventromedian bands long, moderately broad. Parameres (Fig.
50F) very thin, each acutely pointed at apex; apical area short, mesially with 4 short setae at
base.
Female: Eighth ventrite obtuse posteromedially; gonocoxites (Fig. 50F) each with apicolateral tooth long, very acute, apicolateral setae long. Spermatheca (Fig. 50G) with capsule short;
striped duct moderately long, thick; duct moderately long, moderately thick, with 8 turns; glandslightly small, ovoidal, with opening located on the lateral side of duct between the 5th and 6thturns; basal valve very short; basal duct hardly developed.
Biology and ecology. The beetles of S. subulifer inhabit leaf litter heaped in the natural forests of mountainous regions.
Remarks. S. subulifer is allied to S. himiko, but it is separable from the latter species by theaedeagal median lobe subtruncate at the apex, apicomedially with a small or very small protrusion (Fig. 50D), the endophallic expulsion hook with its anterior plate longer and narrowly122

Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

Fig. 50. Stenus subulifer Naomi, Nomura & Puthz sp. nov. (Shiga: A, B, E–H, J, Mt. Hira; Fukui: C, D, I, K,
Onyu Pass). A, apical part of aedeagal median lobe with its outthrusted endophallus; B, C, aedeagus; D, 9th
ventrite of male; E, 9th and 10th terga of male; F, posterior part of gonocoxite; G, spermatheca; H, I, copulatory tube; J, posterior part of 8th ventrite of male; K, endophallic expulsion hooks. Scale 1: 0.1 mm for A, F,
H, I, K, 0.2 mm for B–E; scale 2: 0.05 mm for G; scale 3: 0.2 mm for J.

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123rounded at the anterior part (Fig. 50K), and the spermatheca with its duct much shorter andthicker (Fig. 50G). S. subulifer is also allied to S. aoi, but it is separable from the latter species by
the 7th ventrite of male without modiﬁcation, the aedeagal median lobe with its apical sclerotized area hardly developed (Fig. 50B, C), the endophallic expulsion hook with its posterior plate
obliquely truncate (Fig. 50A, K), and the spermatheca with its duct longer and thinner (Fig.
50G).
Etymology. The speciﬁc epithet of this new species is derived from the Latin noun subula(awl) and the Latin particle -fer which means ʻbearingʼ or ʻhavingʼ.
Stenus aoi Naomi & Puthz(Figs. 51A–H, 133A)
Stenus aoi Naomi & Puthz, 1993: 305; Herman, 2001: 2059; Naomi & Puthz, 2013: 144.
Type material examined. Holotype: ♂ (CBM), Masudani, Imajyo, Fukui Pref., 28. xi. 1982,
H. Sasaji leg.
Other material examined. [HONSHU]: 1 ♂2 ♀, Otake, Ohno City, Fukui Pref., 16. v. 1961,
Y. Hayashi leg.; 2 ♀ (cH), same data as above; 1 ♂2 ♀, Mt. Kyogatake, Hota, Katsuyama City,
Fukui Pref., 5. xi. 2007, T. Watanabe leg.
Distribution. Japan: Honshu (Fukui Pref.).
Redescription. Male and female: Body 3.0–3.6 mm (fore body 1.5–1.7 mm) in length. Body
moderately shining; head black; pronotum and abdomen reddish brown to dark red; elytra yellowish brown to reddish brown; labrum reddish brown; antennae and legs yellowish brown toreddish brown. Body with punctures round to elliptical, small to moderately large, and also pronotum partially with coarse punctures and elytra partially with large, coarse punctures. Headshallowly to moderately concave, with a pair of narrow or broad, longitudinal-oblique furrows(or depressions); antennae short, thin; pronotum with surface almost even to slightly uneven,with a median longitudinal depression or central hollow very indistinct or indistinct; elytra withsurface almost smooth or slightly uneven or uneven; hind tarsi each short, with 4th tarsomere
distinctly bilobed, about 1/2 times as long as the 5th, each lobe sometimes thick; abdomen subcylindrical, slightly tapering posteriorly to parallel-sided; lateroventrites and tergoventrite sutures
lost.
Male: Abdomen (Fig. 51A) modiﬁed with a ﬂat area on the 6th, a very shallow depression on
the 7th, and a broad-subtriangular emargination on the 8th ventrite; 9th tergum (Fig. 51B) withventral apophyses moderately long; 9th ventrite (Fig. 51G) with macrosetae short, apicolateral
teeth moderately long, very acute, apicolateral setae moderately long; 10th tergum (Fig. 51B)
shallowly emarginate posteromedially. Aedeagus (Fig. 51F) with median lobe broad, wellrounded at apicolateral corners, subtruncate and very weakly bisinuate apically or with a verysmall apicomedian protrusion; apical sclerotized area narrow, anteriorly with a pair of small
teeth. Endophallus (Fig. 51F) with copulatory tube (Fig. 51D) having basal chamber very large,
main tube very broad at base, subulate in the apical 1/2; expulsion hooks (Fig. 51H) each withposterior plate strongly protruding posterolaterally; ventromedian bands long, each moderately
broad near posterior margin. Parameres (Fig. 51F) each very acutely pointed at apex; apical area
long, mesially with 12 almost short setae.
Female: Eighth ventrite obtuse or pointed posteromedially; gonocoxites (Fig. 51E) each withapicolateral tooth long, acute, apicolateral setae very long. Spermatheca (Fig. 51C) with capsule124

Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

Fig. 51. Stenus aoi Naomi & Puthz (Fukui: Otake). A, 6th to 8th ventrites of male; B, 9th and 10th terga of male;C, spermatheca; D, copulatory tube; E, posterior part of gonocoxite; F, aedeagus; G, 9th ventrite of male; H,
endophallic expulsion hooks. Scale 1: 0.3 mm for A; scale 2: 0.1 mm for B, F, G and 0.05 mm for C, E; scale
3: 0.05 mm for D, H.

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125

short, rounded apically; striped duct moderately long, very thick; duct short, thick to very thick,with 2 distinct turns; gland with opening located on the lateral side of duct a little distal from the
1st turn; basal valve moderately long; basal duct very long; basal pouch very large, bowl-shaped.
Biology and ecology. The beetles of S. aoi inhabit leaf litter heaped in the natural forests oflow mountainous regions.
Remarks. S. aoi is allied to S. subulifer, but it is separable from the latter species by the 7th
ventrite of male with a deeper depression (Fig. 51A), the aedeagal median lobe hardly swollen at
the apicomedian part (Fig. 51F), the endophallic expulsion hook with its posterior plate strongly
protruding posterolaterally (Fig. 51H), and the spermatheca with its duct shorter and thicker (Fig.
51C).
When Naomi & Puthz (1993) described S. aoi as new species, they erroneously reported that
Naomi (1989a) misidentiﬁed S. aoi for S. rufescens Sharp, 1874. It was however true that Naomi
misidentiﬁed S. coiﬀaitiellus Naomi & Puthz, 1993 for S. rufescens. This is obvious when theillustration of aedeagus (Fig. 1A) in Naomi (1989a) is the aedeagus of S. coiﬀaitiellus.
Etymology. The speciﬁc epithet of this species is derived from the Japanese name of theﬂowing plant family Malvaceae, aoi.
Stenus intrarius Naomi & Ito(Figs. 52A–G, 133B)
Stenus intrarius Naomi & Ito, 2018: 91.
Type material examined. Holotype: ♂ (OMNHO), Oisugi Forest, Kutsuki, Shiga Pref., 19. vi.
2007, T. Ito leg. Paratypes: 2 ♂3 ♀, same data as holotype; 1 ♂1 ♀, same locality, 1. iv. 2002, K.
Mizuno leg.; 4 ♂3 ♀, same locality, 28. x. 2008, T. Ito leg.; 1 ♂4 ♀, same locality, 25. ix. 2011, T.
Ito leg.; 2 ♂5 ♀, same locality, 5. v. 2016, T. Ito leg.; 1 ♂, Ashiu, Miyama-cho, Kyoto Pref., 15.
viii. 1992, T. Ito leg.; 1 ♀, same locality, 22. vii. 2000, K. Mizuno leg.; 3 ♂1 ♀, same locality, 14.
vi. 2009, T. Ito leg.; 4 ♂, same locality, 22. ix. 2015, T. Ito leg.
Distribution. Japan: Honshu (Shiga and Kyoto Prefs.).
Redescription. Male and female: Body 2.8–3.2 mm (fore body 1.4–1.5 mm) in length. Body
weakly shining or dull; head black; pronotum, elytra and abdomen dark red to brown or black;labrum dark red to black; antennae reddish brown to dark red; legs yellowish brown to reddish
brown. Body with punctures small to moderately large, round to elliptical, and also pronotum
partially with coarse punctures and elytra partially with coarse to subrugose punctures. Headshallowly concave, with a pair of longitudinal-oblique furrows or depressions; antennae short,thin; pronotum with surface slight uneven to uneven, with a median longitudinal furrow very
indistinct; elytra with surface even to slightly uneven or uneven; hind tarsi each short, 4th tarsomere distinctly bilobed; abdomen almost cylindrical to subcylindrical, slightly tapering posteriorly to subparallel-sided; lateroventrites and tergoventral sutures lost.
Male: Abdomen (Fig. 52E) modiﬁed with an elongate, shallow depression on the 7th, and abroad emargination on the 8th ventrite; 9th tergum (Fig. 52D) with ventral apophyses thin, relatively short; 9th ventrite (Fig. 52C) with macrosetae short, apicolateral teeth acute, apicolateral
setae short; 10th tergum shallowly emarginate posteriorly. Aedeagus (Fig. 52A) with median lobe
elongate, moderately broad, weakly constricted near the middle, broad and obtusely angulate atapicolateral corners, broad-subtriangular in shape at the apical part, obtuse at apex; apical sclerotized area very short, shortly separated at the middle, covered with very small, pointed tubercles.

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Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

Fig. 52. Stenus intrarius Naomi & Ito (Shiga, Oisugi: A, C, G; Kyoto: B, D–F, Asiu). A, aedeagus; B, spermatheca; C, 9th ventrite of male; D, 9th and 10th terga of male; E, 7th and 8th ventrites of male; F, posterior partof gonocoxite; G, posterior part of 8th ventrite of female. Scale 1: 0.1 mm for A, G, 0.05 mm for B, 0.2 mm for
D, F; scale 2: 0.1 mm for C; scale 3: 0.2 mm for E.

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127

Endophallus (Fig. 52A) with copulatory tube having basal chamber thick, main tube thick atbase, attenuate toward apex; dorsolateral bands moderately long, broad, each with a line of small
dots along mesial margin; expulsion hooks each tadpole-shaped, weakly sclerotized mesially,
with anterior plate thin, attenuate, posterior plate subcircular, gently rounded posteriorly; ventromedian bands with basal bands very long, broad, and dorsally folded bands short, broad, divergent anteriorly. Parameres (Fig. 52A) rather thin, slender, each acutely pointed at apex; apicalarea short, only weakly swollen mesially at base, mesially also with 4 to 5 moderately long setae,
glabrous at the most apical part.
Female: Eighth ventrite obtuse or pointed posteromedially (Fig. 52G); gonocoxites (Fig.
52F) each with apicolateral tooth moderately long, acute, apicolateral setae very long. Spermatheca (Fig. 52B) with capsule short, thick, rounded apically; striped duct very long, thick; ductvery long, relatively thin to moderately thick, loosely or moderately coiled except for straightduct from base to 1st bent; basal valve very long; basal sclerotized duct very short.
Biology and ecology. The beetles of S. intrarius inhabit leaf litter heaped in the natural forests of low mountainous regions.
Remarks. S. intrarius is allied to S. shojiroi and S. gloriﬁcus, but it is separable from the latter 2 species by the aedeagal median lobe with its apical sclerotized area hardly developed andshortly separated at the middle (Fig. 52A), and the copulatory tube with its main tube thicker atbase (Fig. 52A), and the endophallic expulsion hook with its anterior plate slightly turning
anterolaterally (Fig. 52A).
Stenus shojiroi Naomi(Fig. 53A–G)
Stenus shojiroi Naomi, 2021: 68.
Type material examined. Holotype: ♂ (KUMF), Ashiu, Kyoto Pref., 5. ix. 1992, T. Ito leg.
Distribution. Japan: Honshu (Kyoto Pref.).
Redescription. Male: Body 3.2 mm (fore body 1.5 mm) in length. Body moderately shining;head black; pronotum, elytra and abdomen dark red; labrum dark red; antennae and legs yellowish brown to reddish brown. Body with punctures round to elliptical, small to moderately large,
and also pronotum and elytra partially with coarse to subrugose punctures. Head moderately concave, with a pair of longitudinal-oblique furrows or depressions; antennae short, thin; pronotumwith surface slightly uneven, with a median longitudinal depression indistinct; elytra with surface uneven; hind tarsi each short, with 4th tarsomere distinctly bilobed, each lobe thick; abdomen subcylindrical, slightly tapering posteriorly; lateroventrites and tergoventrite sutures lost.
Abdomen (Fig. 53E) modiﬁed with a subtriangular emargination on the 8th ventrite; 9th tergum (Fig. 53B) with ventral apophyses long; 9th ventrite (Fig. 53A) with macrosetae very short,apicolateral teeth slightly short, acute, apicolateral setae slightly short; 10th tergum (Fig. 53B)
entire. Aedeagus (Fig. 53C) with median lobe broad in about apical 1/2, broadest a little before
apicolateral corners, broad-subtriangular at the apical part, obtuse at apex; apical sclerotized area
(Fig. 53D) transverse, subrhombic, declivous apicad when seen from ventral side, slightly
uneven, covered sporadically with a very small, pointed tubercles, submembranous at the narrow,most apical part. Endophallus (Fig. 53C) with copulatory tube (Fig. 53G) having basal chamber
ovoidal, main tube short, almost attenuate, slightly bent near the apical 1/3; dorsolateral bands
moderately broad; dorsal membrance densely covered with extremely small tubercles; expulsion

128

Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

Fig. 53. Stenus shojiroi Naomi. (Kyoto: Asiu). A, 9th ventrite of male; B, 9th and 10th terga of male; C,aedeagus; D, apical part of aedeagal median lobe; E, posterior part of 8th ventrite of female; F, endophallic
expulsion hooks; G, copulatory tube. Scale 1: 0.2 mm for A–C, 0.1 mm for D, F, G; scale 2: 0.25 mm for E.

hooks (Fig. 53F) each tadpole-shaped, with anterior plate elongate, almost pointed or obtuse atanterior tip, clearly demarcated from posterior plate, posterior plat subcircular; ventromedianbands very long, very broad. Parameres (Fig. 53C) very thin, each moderately curved mesially,
acutely pointed at apex; apical area moderately long, mesially with 2 short setae near base.
Female: Unknown.

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129

Biology and ecology. The beetle of S. shojiroi inhabits leaf litter heaped in the natural forestof a mountainous region.
Remarks. S. shojiroi is closely allied to S. gloriﬁcus, but it is separable from the latter species
by the aedeagal median lobe very weakly protruding posteriorly to form the transverse, subrhombic apical sclerotized area (Fig. 53D), the endophallic dorsal membrance covered with smaller
tubercles (Fig. 53C), and the endophallic expulsion hook with its posterior plate rounded posteriorly (Fig. 53F).
Etymology. This species is named after younger brother of ﬁrst author, Dr. Shojiro Naomi(Kumamoto) who contributed to the clariﬁcation of the beetle fauna of Kumamoto Pref., Kyushu.
Stenus gloriﬁcus Naomi, Nomura & Puthz sp. nov.
(Fig. 54A–F)
Type material examined. Holotype: ♂ (KUMF), Ashiu, Kyoto Pref., 5. ix. 1992, T. Ito leg.
Distribution. Japan: Honshu (Kyoto Pref.).
Description. Male: Body 3.2 mm (fore body 1.5 mm) in length. Body moderately shining;head black; pronotum, elytra and abdomen dark red; labrum reddish brown; antennae and legs
reddish brown. Body with punctures round to elliptical, small to moderately large, and also pronotum partially with subrugose punctures and elytra partially with large, subrugose punctures.
Head shallowly concave, with a pair of longitudinal-oblique depressions; antennae short, thin;pronotum with surface slightly uneven, with a median longitudinal depression hardly developed;
elytra with surface uneven; abdomen subcylindrical, slightly tapering posteriorly; lateroventrites
and tergoventrite sutures lost.
Abdomen (Fig. 54C) modiﬁed with a very shallow depression on the 7th, and a moderately
deep emargination on the 8th ventrite; 9th tergum (Fig. 54A) with ventral apophyses long; 9th
ventrite (Fig. 54B) with macrosetae very short, apicolateral teeth short, acute, apicolateral setae
short; 10th tergum (Fig. 54A) very shallowly emarginate posteromedially. Aedeagus (Fig. 54D)
with median lobe broad, subtruncate at apex, with 4 very small, equidistantly located teeth alongposterior margin; apical sclerotized area much transverse, with surface slightly uneven, very sporadically covered with a very small, pointed tubercles. Endophallus (Fig. 54E) with copulatory
tube (Fig. 54F) having main tube almost attenuate, very slightly curved near the apical 1/3; dorsolateral bands extremely long; dorsal membrane covered densely with small, elongate tubercles;
expulsion hooks each with anterior plate elongate, slightly narrowing anteriad, posterior plate
subtruncate posteriorly, minutely serrate along posterior margin; ventromedian bands very long,very broad. Parameres (Fig. 54D) very thin, each slightly curved mesially before the base of apical area, very acutely pointed at apex; apical area moderately long, mesially with 2 short setae
before the middle.
Female: Unknown.
Biology and ecology. The beetle of S. gloriﬁcus inhabits leaf litter heaped in the natural forest of a mountainous region.
Remarks. S. gloriﬁcus is closely allied to S. shojiroi, but it is separable from the latter species
by the aedeagal median lobe subtruncate, with 4 very small, equidistantly located teeth along theposterior margin (Fig. 54D), the endophallic dorsal membrance covered with larger tubercles(Fig. 54E), and the endophallic expulsion hook with its posterior plate almost truncate posteriorly (Fig. 54E).
Etymology. The speciﬁc epithet of this new species is derived from the Latin adjective glori-

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Fig. 54. Stenus gloriﬁcus Naomi, Nomura & Puthz sp. nov. (Kyoto: Asiu). A, 9th and 10th terga of male; B, 9th
ventrite of male; C, 7th and 8th ventrites of male; D, aedeagus; E, apical part of aedeagal median lobe with its
outthrusted endophallus; F, copulatory tube. Scale 1: 0.2 mm for A, B, D, 0.1 mm for E, F; scale 2: 0.3 mm forC.

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ﬁcus which means ʻglorious.ʼ
Incertae sedis
Key to the Japanese species of the cephalotes-subgroup (4)This is a key for a unit of Stenus-species (7 species) beginning with S. inaspectus and adequately diagnosed with the combination of following character conditions: Body dark (dark red
to dark red near black or dark reddish brown near black) to black in color (Fig. 133C–F); aedeagal median lobe moderately broad to broad, broad even at apicolateral corners (Fig. 55C), andalways with an apical or apicomedian emargination of various size and shape (Fig. 57D); copulatory tube usually simple in structure, attenuate and weakly curved (Fig. 55C).
Distribution. Japan: Shikoku and Kyushu.
1(10) Male: Abdominal modiﬁcations slightly developed in the 6th to 8th or the 7th to 8th segments.
2(9) Male: Copulatory tube not bent apically; aedeagal paramere with apical area not spatulate.
3(6) Male: Aedeagal median lobe with apicomedian emargination about 1/3 times as broad as
the breadth of median lobe at apicolateral corners.
4(5) Male: Aedeagal median lobe with apicomedian emargination semicircular (Fig. 55C);
copulatory tube with anterior plate turning anteriorly (Fig. 55G) ......... S. inaspectus Puthz
5(4) Male: Aedeagal median lobe with apicomedian emargination subtriangular (Fig. 56D);
copulatory tube with anterior plate turning anterolaterally (Fig. 56C) .................................
. .................................................................. S. kochiensis Naomi, Nomura & Puthz sp. nov.
6(3) Male: Aedeagal median lobe with apical emargination broader than half the breadth ofmedian lobe at apicolateral corners.
7(8) Male: Aedeagal median lobe with apical emargination semicircular (Fig. 57D); endophallic expulsion hook with posterior plate strongly protruding laterally (Fig. 57F)..................
.................................................................................................................S. imasakai Naomi
8(7) Male: Aedeagal median lobe with apical emargination subtriangular (Fig. 59D); endophallic expulsion hook with posterior plate not protruding laterally (Fig. 59F)...................
................................................................................................................ S. inassuetus Puthz
9(2) Male: Copulatory tube distinctly bent apically (Fig. 58E); aedeagal paramere with apicalarea slightly spatulate (Fig. 58D) .......................................S. cosiciensis Naomi & Hayashi
10(1) Male: Abdominal modiﬁcations well-developed in the 4th to 8th segments.
11(12) Male: Aedeagal median lobe with apically-located emargination much broader (Fig.
60C); endophallic expulsion hook with anterior plate turning apicolaterally (Fig. 60C) .....
.................................................................................................................... S. daimio Naomi
12(11) Male: Aedeagal median lobe with apically-located emargination much narrower (Fig.
61A); endophallic expulsion hook with anterior plate slightly turning apicomesially (Fig.
61A) ....................................................... S. takashiiellus Naomi, Nomura & Puthz sp. nov.

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Fig. 55. Stenus inaspectus Puthz (Kochi: A, G, Mt. Irazu; Ehime: B, C, Mt. Ishizuchi, D, F, Shirasa Pass, E, Mt.
Odami). A, 9th and 10th terga of male; B, 9th ventrite of male; C, aedeagus; D, spermatheca; E, 7th and 8th
ventrites of male; F, posterior part of gonocoxite; G, endophallic expulsion hooks. Scale 1: 0.2 mm for A,
0.1 mm for D, F; scale 2: 0.1 mm for B, C; scale 3: 0.3 mm for E; scale 4: 0.05 mm for G.

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Stenus inaspectus Puthz(Figs. 55A–G, 133D)
Stenus inaspectus Puthz, 1993: 159; Herman, 2001: 2227; Naomi & Puthz, 2013: 144.
Type material examined. Holotype: ♂ (NHMG), via Mt. Ishizuchi (1,000 m), Ehime Pref.,14. viii. 1980, I. Löbl leg.
Other material examined. [SHIKOKU]: 1 ♂1 ♀, Shirasa Pass, Saijyo City, Ehime Pref., 9. vi.
2013, H. Yokozeki leg.; 1 ♂, Mt. Odami, Ehime Pref., 2. ix. 1993, M. Yamamoto leg.; 2 ♂1 ♀,Mt. Irazu, Higashitsuno Vil., Kochi Pref., 24. v. 2005, T. Watanabe leg.
Distribution. Japan: Shikoku (Ehime and Kochi Prefs.).
Redescription. Male and female: Body 4.0–4.4 mm (fore body 1.8–2.0 mm) in length. Body
moderately shining; head and abdomen black; pronotum and elytra dark red near black to black;labrum dark reddish brown; antennae and legs yellowish brown to reddish brown. Body with
punctures round to ovoidal, small to moderately large, and also pronotum partially with coarse tosubrugose punctures and elytra partially with large, subrugose punctures. Head shallowly tomoderately concave, with a pair of longitudinal-oblique or medially-curved furrows; antennae
short, very thin to thin; pronotum with surface slightly uneven to uneven, with a median longitudinal furrow very indistinct to indistinct; elytra with surface uneven; abdomen subcylindrical,
moderately thick to thick, subparallel-sided; lateroventrites and tergoventrite sutures lost.
Male: Abdomen (Fig. 55E) modiﬁed with a very shallow depression on the 7th, and analmost arcuate, shallow emargination on the 8th ventrite; 9th tergum (Fig. 55A) with ventral
apophyses moderately long; 9th ventrite (Fig. 55B) with macrosetae very long, apicolateral teeth
long, almost acute, apicolateral setae short; 10th tergum (Fig. 55B) very shallowly emarginate
posterolaterally. Aedeagus (Fig. 55C) with median lobe moderately broad, rounded at apicolateral corners, with a semicircular, apicomedian emargination. Endophallus (Fig. 55C) with copulatory tube without basal constriction, main tube long, attenuate; dorsolateral bands each broad atposterior rim; expulsion hooks each with anterior plate thin, turning anteriorly, slightly incurved
at anterior tip, much narrower than posterior plate; ventromedian bands short. Parameres (Fig.
55C) each very acute at apex; apical area slightly short, thin, mesially with 8 setae.
Female: Eighth ventrite obtuse posterolaterally; gonocoxites (Fig. 55F) each with apicolateral tooth long, almost acute, apicolateral setae very long. Spermatheca (Fig. 55D) with capsule
hardly developed; striped duct very long, thick to very thick, extending proximally to the last 2nd
turn; duct moderately long, moderately thick, loosely coiled with 8 turns; gland large, spherical,
covered densely with long, very thin ciliae, with opening located on the posterior side of duct
between the last 2nd and 3rd turns; basal valve short, about as long as sclerotized basal duct.
Biology and ecology. The beetles of S. inaspectus inhabit leaf litter heaped in the natural forests of mountainous regions.
Remarks. S. inaspectus is probably allied to S. kochiensis, but it is separable from the latter
species by the aedeagal median lobe with its apically-located emargination semicircular (Fig.
55C) and the endophallic expulsion hooks almost positioned in parallel with each other (Fig.
55G).

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Fig. 56. Stenus kochiensis Naomi, Nomura & Puthz sp. nov. (Kochi: Oki Is.). A, 9th and 10th terga of male; B,
9th ventrite of male; C, endophallic expulsion hooks, ventromedian bands and diverticulum; D, aedeagus; E,
6th to 8th ventrites of male; F, copulatory tube. Scale 1: 0.2 mm for A, 0.05 mm for C, 0.1 mm for F; scale 2:
0.1 mm for B, D; scale 3: 0.3 mm for E.

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Stenus kochiensis Naomi, Nomura & Puthz sp. nov.
(Fig. 56A–F)
leg.

Type material examined. Holotype: ♂ (KUMF), Oki Is., Tosa (Kochi Pref.), 5. v. 1988, T. Ito

Distribution. Japan: Shikoku (Kochi Pref.: Oki Is.).
Description. Male: Body 3.3 mm (fore body 1.7 mm) in length. Body moderately shining;head black; pronotum, elytra and abdomen dark red; labrum reddish brown; antennae and legs
yellowish brown to reddish brown. Body with punctures round to ovoidal, small to moderately
large, and also pronotum partially with coarse punctures and elytra partially with large, coarse
punctures. Head moderately concave, with a pair of longitudinal-oblique furrows; antennae moderately long, thin; pronotum with surface slightly uneven, with a median longitudinal furrow
very indistinct; elytra with surface uneven; abdomen subcylindrical, thin, subparallel-sided; lateroventrites and tergoventrite sutures lost.
Abdomen (Fig. 56E) modiﬁed with a ﬂat area on the 6th, a very shallow depression on the
7th, and a subtriangular emargination on the 8th ventrite; 9th tergum (Fig. 56A) with ventral
apophyses long; 9th ventrite (Fig. 56B) with macrosetae long, apicolateral teeth long, apicolateral setae long; 10th tergum (Fig. 56B) entire. Aedeagus (Fig. 56D) with median lobe moderately
broad, rounded at apicolateral corners, with a subtriangular apicomedian emargination, the lateralside of which protrudes posterioarly and is obtuse. Endophallus with copulatory tube (Fig. F56)
having main tube attenuate; expulsion hooks (Fig. 56C) almost X-shaped, asymmetrically sclerotized, with anterior plate turning anterolaterally, posterior plate minutely serrate posteriorly; ventromedian bands (Fig. 56C) broad. Parameres (Fig. 56D) short, each very acute at apex; apicalarea very short, thin, mesially with 7 to 9 setae.
Female: Unknown.
Biology and ecology. S. kochiensis is insular and thus may be endemic to Oki Island, oﬀ
Kochi Pref. The beetle of this species inhabits leaf litter heaped in the natural forest of Oki Is.
Remarks. S. kochiensis is allied to S. inaspectus, but it is separable from the latter species by
the aedeagal median lobe with its apically-located emargination subtriangular (Fig. 56D) and theendophallic expulsion hooks almost X-shaped (Fig. 56C).
Etymology. The speciﬁc epithet of this new species is derived from the name of type locality,
Kochi.
Stenus imasakai Naomi(Figs. 57A–G, 133D)
Stenus imasakai Naomi, 1989: 163; Herman, 2001: 2223; Naomi & Puthz, 2013: 144.
Type material examined. Holotype: ♂ (KUF), Nishisonogi-gun, Nagasaki Pref., 23. iv. 1978,
S. Imasaka leg. Paratypes: 2 ♂1 ♀, same data as holotype.
Other material examined. [KYUSHU]: 1 ♂2 ♀, Shirakashi, Ohseto-cho, Nagasaki Pref., 18.
v. 1997, S. Nomura leg.; 2 ♂1 ♀, Iwaseto Valley, Sotome-cho, Nagasaki Pref., 18. v. 1997, S.
Nomura leg.; 2 ♂1 ♀, Tsugane-otoshi Waterfall, Ooseto-machi, Nagasaki Pref., 5. vii. 1996, S.
Nomura leg.
Distribution. Japan: Kyushu (Nagasaki Pref.).
Redescription. Male and female: Body 3.5–4.0 mm (fore body 1.6–1.9 mm) in length. Body

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Fig. 57. Stenus imasakai Naomi (Nagasaki: A, B, D, F, Ooseto, C, Shirakashi, E, G, Iwaseto). A, 9th and 10th
terga of male, with a pair of longitudinal, ligament-like membranous bands; B, 9th ventrite of male; C, 6th to
8th ventrites of male; D, aedeagus; E, spermatheca; F, endophallic expulsion hooks; G, posterior part of gonocoxite. Scale 1: 0.2 mm for A, 0.1 mm for E, G; scale 2: 0.1 mm for B, D, 0.05 mm for F; scale 3: 0.3 mm forC.

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moderately to strongly shining; head black; pronotum and elytra dark red; abdomen dark red near
black to black; labrum reddish brown to dark red; antennae and legs yellowish brown to pale reddish brown. Body with punctures round to ovoidal, small to moderately large, and also pronotum
partially with coarse to subrugose punctures and elytra partially with large, coarse to subrugose
punctures. Head moderately concave, with a pair of longitudinal-oblique or mesially-curved furrows; antennae short to moderately long, very thin; pronotum with surface slightly uneven to
uneven, with a median longitudinal furrow indistinct; elytra with surface slightly uneven to
uneven; abdomen subcylindrical, subparallel-sided; lateroventrites lost, tergoventral sutures very
thin, present only in the 3rd to 4th segments.
Male: Abdomen (Fig. 57C) modiﬁed with a very shallow depression on the 6th, a shallow
depression on the 7th, and a subriangular emargination on the 8th ventrite; 9th tergum (Fig. 57A)
with ventral apophyses long; 9th ventrite (Fig. 57B) with macrosetae long, apicolateral teeth
obtusely pointed, apicolateral setae short; 10th tergum (Fig. 57B) entire. Aedeagus with median
lobe (Fig. 57D) broad, rounded at apicolateral corners, with a very broad, semicircular apicalemargination. Endophallus (Fig. 57D) with copulatory tube having basal chamber ovoidal, maintube subfusiform at base, attenuate; dorsolateral bands each very thick at base; expulsion hooks(Fig. 57F) moderately large, each broad, with lateral rim almost uniquely sclerotized, posterior
plate strongly protruding laterally; ventromedian bands moderately long, thin. Parameres (Fig.
57D) short, each acutely pointed at apex; apical area moderately long, slightly swollen laterally,
mesially with 7 setae.
Female: Eighth ventrite obtuse posteromedially; gonocoxites (Fig. 57G) each with apicolateral tooth slightly short, obtusely pointed, apicolateral setae moderately long. Spermatheca (Fig.
57E) with capsule very thick, well-rounded apically; striped duct moderately long, very thickdistally, strongly narrowing proximad; duct short, thin to moderately thick with 4 turns; basal
valve slightly long, basal duct very short; basal pouch almost subconical, submembranous.
Biology and ecology. The beetles of S. imasakai inhabit leaf litter heaped in the natural forests of lowlands to low mountainous regions.
Remarks. S. imasakai is allied to S. inaspectus and S. kochiensis, but it is separable from thelatter 2 species by the aedeagal median lobe with its apically-located emargination much broader(Fig. 57D), the copulatory tube with its basal constriction distinct, and the endophallic expulsion
hook with its posterior plate strongly protruding laterally (Fig. 57F).
Etymology. This species is named after Mr. Shoichi Imasaka (Kurume) who collected theStenus-beetles designated as the type specimens.
Stenus cosiciensis Naomi & Hayashi(Figs. 58A–H, 133E)
Stenus cosiciensis Naomi & Hayashi, 2017: 249.
Type material examined. Holotype: ♂ (KUMF), Mt. Odake (310 m), Shimo-koshiki Is.,
Koshiki Isls., Kagoshima Pref., 24. v. 2014, M. Yoshida leg. Paratypes: 3 ♂3 ♀, same locality as
holotype, 23–24. v. 2014, M. Yoshida leg.; 1 ♂4 ♀ (OMNHO, cH), same locality, 23–24. v. 2014,
Y. Hayashi leg.; 1 ♂, same locality, 23–24. v. 1994, T. Ueno leg.
Distribution. Japan: Kyushu (Kagoshima Pref.: Koshiki Isls.).
Redescription. Male and female: Body 3.7–4.1 mm (fore body 1.7–1.8 mm) in length. Body
moderately to strongly shining; head and abdomen almost black to black; pronotum and elytra

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Fig. 58. Stenus cosiciensis Naomi & Hayashi (Kagoshima: Shimokoshiki Is., Mt. Odake). A, Sixth to 8th ventrites of male; B, 9th and 10th terga of male; C, 9th ventrite of male; D, aedeagus (ventral view); E, copulatorytube; F, endophallic expulsion hooks; G, spermatheca; H, apical part of gonocoxite. Scale 1: 0.3 mm for A;
scale 2: 0.2 mm for B; scale 3: 0.1 mm for C, D and 0.05 mm for E–H.

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dark red near black; labrum reddish brown to dark brown; antennae and legs yellowish brown toreddish brown. Body with punctures round to ovoidal, small to moderately large, and also pronotum partially with coarse to subrugose punctures and elytra partially with large, coarse punctures.
Head moderately concave, with a pair of longitudinal-oblique furrows; antennae short to moderately long, very thin; pronotum with surface slightly uneven to uneven, with a median longitudinal furrow indistinct; elytra with surface slightly uneven to uneven; abdomen subcylindrical,
subparallel-sided; lateroventrites and tergoventrite sutures lost.
Male: Abdomen (Fig. 58A) modiﬁed with a ﬂat area or a very shallow depression on the 6th,
a longitudinal, shallow depression on the 7th, and a subtriangular emargination on the 8th ventrite; 9th tergum (Fig. 58B) with ventral apophyses moderately long; 9th ventrite (Fig. 58C) withapicolateral teeth slightly short, very acute, apicolateral setae moderately long; 10th tergum (Fig.
58B) rounded posteriorly. Aedeagus (Fig. 58D) with median lobe moderately broad, almost
angulate at apicolateral corners, with a slightly narrow, V-shaped apicomedian emargination, thelateral side of which protrudes posteriorly and is very acute. Endophallus (Fig. 58D) with copulatory tube (Fig. 58E) having basal chamber almost elliptical, large to very large, main tube attenuate, distinctly bent apically; dorsolateral bands thin; expulsion hooks (Fig. 58F) slightly asymmetrical, each with anterior plate a little smaller than posterior plate, posterior plate moderately
rounded laterally; ventromedian bands long, very broad. Parameres (Fig. 58D) short, each almost
rounded apically; apical area slightly spatulate, mesially with 6 to 7 setae.
Female: Eighth ventrite obtuse posteromedially or almost rounded posteriorly; gonocoxites(Fig. 58H) each with apicolateral tooth long, very acute, apicolateral setae very long. Spermatheca (Fig. 58G) with capsule short, rounded apically; striped duct short, thick; duct short, thick,with 3 turns; basal valve slightly short, about as long as sclerotized basal duct; basal pouch bowlshaped, membranous.
Biology and ecology. S. cosiciensis is insular and thus may be endemic to Koshiki Islands oﬀ
Kagoshima Pref. The beetles of this species inhabit leaf litter heaped in the natural forests of alow mountainous region.
Remarks. S. cosiciensis is allied to S. inassuetus, but it is separable from the latter species by
the aedeagal median lobe with its apically-located emargination narrower (Fig. 58D), the copulatory tube beak-shaped at the apical part (Fig. 58E), the endophallic expulsion hook with its posterior plate rounded posteriorly (Fig. 58F), and the spermatheca with its duct shorter and movable (Fig. 58G).
Stenus inassuetus Puthz(Fig. 59A–H)
Stenus inassuetus Puthz, 1993: 157; Herman, 2001: 2227; Naomi & Puthz, 2013: 144.
Stenus uneme Naomi,1989a: 8 (in part).
Type material examined. Holotype: ♂ (NHMG), Omogo (900 m), Mt. Ishizuchi, Ehime Pref.,I. Löbl & Cl. Besuchet leg. Paratype (paratype of S. uneme): ♂, Omogo, Ehime Pref., 15. vi.
1981, S. Naomi leg.
Other material examined. [SHIKOKU]: 1 ♂1 ♀, Mt. Tsurugi, Tokushima Pref., 17. vii. 1971,
M. Yoshida leg.; 1 ♂, Omogo, Mt. Ishizuchi, Ehime Pref., 23. vii. 1989, M. Sakai leg.; 1 ♂1 ♀,same locality, 29. iv. 1989, T. Ito leg.; 1 ♂, Mt. Odami, Ehime Pref., 2. ix. 1993, Yamamoto leg.;1 ♂, same locality, 21. vii. 1993, M. Sakai leg.

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Fig. 59. Stenus inassuetus Puthz (Tokushima, A, B, Mt. Tsurugi; Ehime, C, D, F–H, Omogo, E, Mt. Odami). A,
9th and 10th terga of male; B, 9th ventrite of male; C, spermatheca; D, aedeagus; E, 6th to 8th ventrites ofmale; F, endophallic expulsion hooks; G, 10th tergum of female; H, posterior part of gonocoxite. Scale 1:
0.1 mm for A, B, D, 0.05 mm for F; scale 2: 0.1 mm for C, 0.2 mm for G; scale 3: 0.3 mm for E.

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Distribution. Japan: Shikoku (Tokushima and Ehime Prefs.).
Redescription. Male and female: Body 3.1–3.6 mm (fore body 1.5–1.7 mm) in length. Body
moderately shining; head black; pronotum, elytra and abdomen dark red to dark reddish brown;
labrum dark reddish brown; antennae and legs yellowish brown to reddish brown. Body with
punctures round to ovoidal, small to moderately large, and also pronotum partially with subrugose punctures and elytra partially with large, coarse punctures. Head moderately concave, witha pair of longitudinal-oblique or mesially- curved furrows; antennae short to moderately long,very thin to thin; pronotum with surface slightly uneven to uneven, with a median longitudinalfurrow distinct; elytra with surface uneven; abdomen subcylindrical, slightly tapering posteriorly
to subparallel-sided; lateroventrites and tergoventrite sutures lost.
Male: Abdomen (Fig. 59E) modiﬁed with a ﬂat area on the 6th, an elongate, very shallow orshallow depression on the 7th, and a broad, subtriangular emargination on the 8th ventrite; 9th
tergum (Fig. 59A) with ventral apophyses long; 9th ventrite (Fig. 59A) with apicolateral teeth
long, very acute, apicolateral setae moderately long; 10th tergum (Fig. 59A) almost rounded posteriorly. Aedeagus (Fig. 59D) elongate, with median lobe elongate, becoming broader from the
middle to the broadest apicolateral corners, with a broad, subtriangular apical emargination (orwith a pair of very acute, broadly separated, apicolateral protrusions). Endophallus (Fig. 59D)
with copulatory tube with basal chamber elongate, main tube thick at base, attenuate; dorsolateral bands thin; expulsion hooks (Fig. 59F) each broad, with anterior plate pointed at anterior tip,with or without a very small cusp, posterior plate almost truncate posteriorly; ventromedianbands moderately long, moderately broad. Parameres (Fig. 59D) each acutely pointed at apex;
apical area moderately long, slightly swollen laterally, mesially with 8 to 10 setae.
Female: Eighth ventrite almost rounded posteriorly; gonocoxites (Fig. 59H) each with apicolateral tooth very long, very acute, apicolateral setae very long; 10th tergum (Fig. 59G) distinctly
pointed apicomedially, almost triangular at apical part. Spermatheca (Fig. 59C) with capsule
moderately long; striped duct slightly short, moderately thick; duct moderately long, moderately
thick, tightly coiled, presumably ﬁxed in position and thus immovable by the unusual sclerotization developed between the running ducts; basal pouch conical, membranous.
Biology and ecology. The beetles of S. inassuetus inhabit leaf litter heaped in the natural forests of a mountainous region.
Remarks. S. inassuetus is allied to S. cosiciensis, but it is separable from the latter species by
the aedeagal median lobe with its apically-located emargination broader (Fig. 59D), the copulatory tube simply attenuate (Fig. 59D), the endophallic expulsion hook with its posterior platealmost truncate posteriorly (Fig. 59F), and the spermatheca with its duct longer and immovable(Fig. 59C).
Stenus daimio Naomi(Figs. 60A–F, 133F)
Stenus daimio Naomi, 1989: 162; Herman, 2001: 2155; Naomi & Puthz, 2013: 144.
Type material examined. Holotype: ♂ (KUMF), Nagasaki City, Nagasaki Pref., 6. xi. 1977,
H. Ohishi leg. Paratypes: 3 ♀, same data as holotype.
Distribution. Japan: Kyushu (Nagasaki Pref.).
Redescription. Male and female: Body 4.0–4.3 mm (fore body 1.9–2.1 mm) in length. Body
moderately shining; head black; pronotum, elytra and abdomen dark reddish brown near black;142

Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

Fig. 60. Stenus daimio Naomi (Nagasaki: Nagasaki City). A, 4th to 7th ventrites of male; B, 9th and 10th terga of
male; C, aedeagus; D, spermatheca; E, 9th ventrite of male; F, posterior part of gonocoxite. Scale 1: 0.3 mm
for A; scale 2: 0.2 mm for B, E, 0.1 mm for D, F; scale 3: 0.1 mm for C.

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labrum reddish brown to dark reddish brown; antennae and legs yellowish brown to reddish
brown. Body with punctures round to ovoidal, small to moderately large, and also pronotum partially with subrugose punctures and elytra partially with large, subrugose punctures. Head moderately concave, with a pair of longitudinal-oblique furrows; antennae moderately long to long,very thin; pronotum with surface uneven, with a median longitudinal furrow indistinct; elytra
with surface uneven; abdomen subcylindrical, subparallel-sided; lateroventrites and tergoventrite
sutures lost.
Male: Abdomen (Fig. 60A) modiﬁed with a transverse, slightly deep depression on the 4th, alarge, moderately deep depression on the 5th, a very large, very deep depression on the each of
6th and 7th, and a small, subtriangular emargination on the 8th ventrite; 9th tergum (Fig. 60B)
with ventral apophyses long; 9th ventrite (Fig. 60E) with apicolateral teeth long, thin, very acute,apicolateral setae short; 10th tergum (Fig. 60B) rounded posteriorly. Aedeagus (Fig. 60C) withmedian lobe broad, with a very broad, apical emargination (or a pair of almost acute, very widely
separated, apicolateral protrusions). Endophallus (Fig. 60C) with copulatory tube having maintube slightly short, attenuate, weakly curved behind the middle; dorsolateral bands thin; expulsion hooks (Fig. F) moderately large, each with anterior plate turning apicolaterally, posterior
plate well-rounded laterally; ventromedian bands long, very broad. Parameres (Fig. 60C) short,each acutely pointed at apex; apical area slightly short, moderately swollen laterally, mesiallywith 8 setae.
Female: Eighth ventrite obtuse or minutely pointed posteromedially; gonocoxites (Fig. 60F)
each with apicolateral tooth very long, very acute, apicolateral setae very long. Spermatheca(Fig. 60D) with capsule very short, rounded apically; striped duct moderately long, thick; duct
short, thick, with 2 turns; gland slightly small, spherical, with opening located on the lateral sideof duct between the 2nd and 3rd turns; basal valve short, basal duct very short, almost embedded
into the distal part of basal pouch which is low-conical in shape.
Biology and ecology. The beetles of S. daimio inhabit leaf litter heaped in the natural forestsof lowlands.
Remarks. S. daimio is allied to S. takashiiellus, but it is separable from the latter species by
the aedeagal median lobe with its apically-located emargination much broader (Fig. 60C), theendophallic expulsion hook with its anterior plate broader and rounded or angulate at the anteriortip (Fig. 60C), and the spermatheca with its duct much shorter and thinner (Fig. 60D).
In S. daimio the 8th ventrite of female is the same in shape as in the other congeners, but in
one female examined, the apical part is triangular, which is unusual in the females of the speciesof cephalotes-group. At least in the same female, furthermore, the 10th tergum has a triangular
apex, as in the 8th ventrite.
Etymology. The speciﬁc epithet of this species is derived from the Japanese lord of medieval
period, daimio.
Stenus takashiiellus Naomi, Nomura & Puthz sp. nov.
(Fig. 61A–G)
Type material examined. Holotype: ♂ (KUMF), Mt. Morotsuka, Morotsuka, Miyazaki Pref.,30. vii. 2016, T. Watanabe leg. Paratypes: 6 ♂1 ♀, Mt. Mukôzaka, Gokase, Miyazaki Pref., 13. v.
2017, T. Watanabe leg.
Distribution. Japan: Kyushu (Miyazaki Pref.).
Description. Male and female: Body 3.6–4.2 mm (fore body 1.9–2.1 mm) in length. Body

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Fig. 61. Stenus takashiiellus Naomi, Nomura & Puthz sp. nov. (Miyazaki: A, B, E, Mt. Morotsuka, C, D, F, G,
Mt. Mukôzaka). A, aedeagus; B, 9th and 10th terga of male; C, 4th to 8th ventrites of male; D, spermatheca;
E, 9th ventrite of male; F, copulatory tube; G, posterior part of gonocoxite. Scale 1: 0.2 mm for A, B, E,
0.1 mm for D, F, G; scale 2: 0.3 mm for C.

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moderately shining; head and abdomen almost black to black; pronotum almost black; elytra
dark red; labrum reddish brown to dark reddish brown; antennae and legs yellowish brown toreddish brown. Body with punctures round to ovoidal, small to moderately large, and also pronotum partially with subrugose punctures and elytra partially with large, subrugose punctures. Headmoderately concave, with a pair of longitudinal-oblique furrows; antennae short to moderately
long, very thin; pronotum with surface uneven, with a median longitudinal furrow very indistinct
to indistinct; elytra with surface slightly uneven to uneven; abdomen subcylindrical, slightly
tapering posteriorly; lateroventrites and tergoventrite sutures lost.
Male: Abdomen (Fig. 61C) modiﬁed with a semilunar ﬂat area on the 3rd, a slightly deep
depression on the 4th, a, moderately deep depression on the 5th, a very large, very deep depression on the each of 6th and 7th, and a subtriangular emargination on the 8th ventrite; 9th tergum(Fig. 61B) with ventral apophyses very long; 9th ventrite (Fig. 61E) with macrosetae very short,apicolateral teeth short, thin, very acute, apicolateral setae short; 10th tergum (Fig. 61B) rounded
posteriorly. Aedeagus (Fig. 61A) with median lobe moderately broad, with a very narrow, apicomedian emargination (or a pair of very narrowly separated, thin apicomedian projections). Endophallus (Fig. 61A) with copulatory tube (Fig. 61F) having main tube moderately long, attenuate;
dorsolateral bands moderately broad; expulsion hooks each with anterior plate almost pointed atanterior tip, narrower than posterior plate; ventromedian bands moderately long, moderately
broad at posterior rim in stored condition. Parameres (Fig. 61A) each almost rounded apically;
apical area short, moderately swollen, mesially with a setal tuft at base and 6 setae in the apical
2/3.
Female: Eighth ventrite almost rounded posteriorly; gonocoxites (Fig. 61F) each slightly falcate, with apicolateral tooth long, acute, apicolateral setae very long. Spermatheca (Fig. 61D)
with capsule half-spherical; striped duct moderately long, thick to very thick; duct moderately
long, thick to very thick, tightly coiled with 6 or 7 turns; gland moderately large, spherical,
densely covered with short, very thin ciliae, with opening located on the lateral side of duct
between the last 3rd and 4th turns; basal valve very short, very narrow; basal duct moderately
long, becoming thicker proximad.
Biology and ecology. The beetles of S. takashiiellus inhabit leaf litter heaped in the naturalforests of mountainous regions.
Remarks. S. takashiiellus is allied to S. daimio, but it is separable from the latter species by
the aedeagal median lobe with its apically-located emargination much narrower (Fig. 61A), theendophallic expulsion hook with its anterior plate thinner and almost pointed at the anterior tip(Fig. 61A), and the spermatheca with its duct much longer and thicker (Fig. 61D). The 10th tergum has a triangular apex at least in one female examined.
Etymology. This species is named after Mr. Takashi Watanabe (Kanagawa) who collected theStenus-beetles designated as the type specimens.
The rufescens-subgroup
Diagnostic characters of the rufescens-subgroup. Male and female: Pronotum and elytra
often pale (pale yellowish brown through yellowish brown to reddish orange) (Fig. 134E) to dark
in color (i.e., darker color than reddish orange) (Fig. 135G); abdominal ventrites of male very
often strongly modiﬁed with the moderately deep, deep and/or very deep depressions, emarginations, etc. (Figs. 82E, I, 100F, H, 02F, G). Male: Aedeagal median lobe similarly formed as in the
cephalotes-subgr. but apical sclerotized area often triangular (Fig. 87G) to subtriangular (includ-146

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ing elongate- or broad-subtriangular, subpentagonal) (Figs. 83A, 90A, 102A) and acutely (Fig.
102A) to very acutely (Fig. 94E) pointed at apex, with a median longitudinal line on it (Fig.
94E), otherwise, median lobe often moderately broad to broad and more or less broad even at
apicolateral corners (Figs. 64A, 112B), or showing some other various forms (Figs. 107C, 108B,
121C).
Species unit 1 of the rufescens-subgroup
Key to the Japanese species of the rufescens-subgroup (1)This is a key for a unit of Stenus-species (12 species) beginning with S. yoshidai and probably diagnosed with the combination of following character conditions: Body sometimes tricolor(Fig. 133J) or pronotum and elytra often with yellowish tinge; aedeagal median lobe often moderately broad to broad, and also more or less broad even at apicolateral corners (Fig. 63C); endophallic expulsion hook often with posterior plate protruding posterolaterally (Fig. 66F).
Distribution. Japan: Honshu (Chubu, Kinki and Chugoku Districts), Shikoku and Kyushu.
1(22) Male and female: Body no less than 2.8 mm in length. Male: Aedeagal median lobe withapical sclerotized area entirely glabrous.
2(15) Male: Aedeagus median lobe with apical sclerotized area not having apicomedian protrusion.
3(12) Male: Aedeagal paramere more or less thicker and not curved mesially.
4(11) Male: Aedeagal paramere extending posteriorly beyond apex of median lobe.
5(8) Male: Endophallic expulsion hook not turning anterolaterally.
6(7) Male: Aedeagal median lobe not expanded laterally at apicolateral corners, with apicalsclerotized area having a median longitudinal suture (Fig. 62E); endophallic expulsion
hook slightly turning anteromesially (Fig. 62E) ......................................S. yoshidai Naomi
7(6) Male: Aedeagal median lobe distinctly expanded laterally at apicolateral corners, withapical sclerotized area not having a median longitudinal suture (Fig. 63C); endophallic
expulsion hook turning anteriorly (Fig. 63E) ......................................S. hirashimai Naomi
8(5) Male: Endophallic expulsion hook turning anterolaterally.
9(10) Male: Copulatory tube with main tube swollen laterally at base, and thick and obtuse atapex (Fig. 64A); expulsion hook with posterior plate acute at posterior tip (Fig. 64A) .......
..................................................................................................... S. yamajii Naomi & Puthz
10(9) Male: Endophallic copulatory tube with main tube thick at base, and subulate at apex
(Fig. 65B); expulsion hook with posterior plate usually obtuse at posterior tip (Fig. 65F,
G) ..........................................................................................................S. gion Naomi & Ito
11(4) Male: Aedeagal paramere not extending posteriorly beyond apex of median lobe (Fig.
66D) .................................................................................................... S. inclarescens Puthz
12(3) Male: Aedeagal paramere thinner, and slightly curved mesially.
13(14) Male: Aedeagal median lobe very minutely pointed at apicomedian part (Fig. 71D); copulatory tube with main tube attenuate (Fig. 71G) ................ S. coiﬀaitiellus Naomi & Puthz
14(13) Male: Aedeagal median lobe obtuse and submembranous at apicomedian part (Fig. 72B);
copulatory tube with main tube spatulate apically (Fig. 72F) ............. S. productus Naomi
15(2) Male: Aedeagus median lobe with apical sclerotized area having an apicomedian protrusion.

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16(21) Male: Copulatory tube with main tube not swollen medially; endophallic expulsion hookwith posterior plate not broadened posteriad.
17(20) Male: Copulatory tube with main tube not curved apically; endophallic expulsion hookwith anterior plate not rounded laterally.
18(19) Male: Aedeagal median lobe with a short, rounded apicomedian protrusion (Fig. 67C);
paramere with apical area mesially with thick setae at base (Fig. 67C)....................................................................... S. fulvidus Naomi, Nomura & Puthz sp. nov.
19(18) Male: Aedeagal median lobe with a short, truncate apicomedian protrusion (Fig. 68A);
paramere with apical area mesially glabrous at base (Fig. 68A) ..........................................
..................................................................S. notomontis Naomi, Nomura & Puthz sp. nov.
20(17) Male: Copulatory tube with main tube moderately curved apically (Fig. 69F); Endophallic expulsion hook with anterior plate moderately rounded laterally (Fig. 69G)..................
....................................................................... S. obtusus Naomi, Nomura & Puthz sp. nov.
21(16) Male: Copulatory tube with main tube strongly swollen laterally near the middle (Fig.
70E); Endophallic expulsion hook with posterior plate distinctly broadened posteriad(Fig. 70F) .............................................................................................S. snodgrassi Naomi
22(1) Male and female: Body 2.5 mm in length. Male: Aedeagal median lobe with apical sclerotized area having apicomedian subtriangular portion very sparsely setose along posterior
margin (Fig. 73B).......................................................................... S. maiko Naomi & Puthz
Stenus yoshidai Naomi(Figs. 62A–F, 133G)
Stenus yoshidai Naomi, 1997: 757; Herman, 2001: 2438; Naomi & Puthz, 2013: 144.
Type material examined. Holotype: ♂ (CBM), Nakatani, Shishikui, Kaifu, Tokushima Pref.,24. ix. 1973, M. Yoshida leg. Paratypes: 1 ♂1 ♀, same data as holotype.
Distribution. Japan: Shikoku (Tokushima Pref.).
Redscription. Male and female: Body 3.4–3.8 mm (fore body 1.7–1.8 mm) in length. Body
moderately shining; head black with median area dark red; pronotum and elytra dark red tobrown; abdomen reddish brown to dark reddish brown; labrum reddish brown to dark red; antennae and legs yellowish brown to reddish brown. Body with punctures round to ovoidal, small tomoderately large, and also pronotum partially with subrugose punctures and elytra partially withlarge, coarse to subrugose punctures. Head moderately concave, with a pair of longitudinaloblique furrows; antennae moderately long, very thin; pronotum with surface uneven, with a
median longitudinal furrow very indistinct; elytra with surface slightly uneven to uneven; abdomen subcylindrical, moderately thick to thick, subparallel-sided; lateroventrites and tergoventral
sutures lost.
Male: Abdomen (Fig. 62D) modiﬁed with a ﬂat area or a very shallow depression on the 7th,
and an arcuate, shallow emargination on the 8th ventrite; 9th tergum (Fig. 62B) with ventral
apophyses moderately long; 9th ventrite (Fig. 62C) with macrosetae long, apicolateral teeth moderately long, very acute, apicolateral setae very long; 10th tergum (Fig. 62B) very shallowly
emarginate posteromedially. Aedeagus (Fig. 62E) with median lobe obtusely angulate at apicolateral corners, obtusely pointed at apex; apical sclerotized area almost broad-subpentagonal inshape, with a median longitudinal suture. Endophallus (Fig. 62E) with copulatory tube moderately long, with basal chamber ovoidal, main tube thick, obtusely pointed at apex; dorsolateral

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Fig. 62. Stenus yoshidai Naomi (Tokushima: Nakatani). A, spermatheca; B, 9th and 10th terga of male; C, 9th
ventrite of male; D, 7th and 8th ventrites of male; E, aedeagus; F, gonocoxite. Scale 1: 0.05 mm for A, 0.1 mm
for B, C, E; scale 2: 0.2 mm for D; scale 3: 0.1 mm for F.

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bands broad at base; expulsion hooks connected each other at the mesial corners of posterior
plate, each slightly turning anteromesially, with anterior plate very small, posterior plate hornlike, anteromesially with a large, nearly semicircular emargination; ventromedian bands slightly
short, each becoming slightly broader anteriad. Parameres (Fig. 62E) each acutely pointed atapex; apical area moderately long, mesially with 9 setae of various length.
Female: Eighth ventrite slightly obtuse posteromedially; gonocoxites (Fig. 62F) each withapicolateral tooth very long, very acute, apicolateral setae very long. Spermatheca (Fig. 62A)
with capsule very small, narrowing apicad; striped duct long, thick; duct extremely short, thick,with 1 turn; gland elongate-ovoidal in shape, with opening located on the lateral side of duct near
the 1st turn; basal valve very short; basal duct moderately long, becoming slightly thicker distad.
Biology and ecology. The beetles of S. yoshidai inhabit leaf litter heaped in the natural forests of a mountainous region.
Remarks. S. yoshidai is probably allied to S. hirashimai, but it is separable from the latter
species by the aedeagal median lobe broadest near the middle (Fig. 62E), the copulatory tube
with its main tube thicker (Fig. 62E), the endophallic expulsion hook with its anterior plate much
shorter (Fig. 62E), the paramere shorter (Fig. 62E), and the spermatheca with its duct shorter(Fig. 62A).
In the endophallic expulsion hook of S. yoshidai, it is diﬃcult to grasp where the anterior andposterior plates are in the Fig. 62E because of the very small size of anterior plate. The anterior
plate is a very small plate located at the anterior tip of expulsion hook, and the dorsolateral bandis inserted at the basilateral side of anterior plate (Fig. 62E).
In a male beetle of S. yoshidai that we examined, it was certainly observed that a spermatophore is stored in the basal chamber of copulatory tube (Fig. 62E). It is ovoidal and sparsely covered with thin, peg-like setae. It also has a pair of black teeth at the apical end, which are basically equal in structure and location to those of S. aestivus (Naomi, 2018). Furthermore, in the
genital chamber of a female beetle, an ovoidal structure was also found (Fig. 62A). This seems
no doubt to be also a spermatophore which was supposedly deposited by a male during the copulation, when considering its size and structure covered with thin, peg-like setae. It was observedthat an elongate duct extends anteriorly from the apical end of spermatophore between the blackteeth (Fig. 62A). Since we do not make sure of the previous condition of the duct stored within
the spermatophore during the pre-copulatory stage, further studies will be needed to conﬁrm
whether or not it is a spermatophore extension tube Gack and Peschke, 1994).
Etymology. This species is named after Mr. Masataka Yoshida (Tokushima) who collected
the Stenus-beetles designated as the type specimens.
Stenus hirashimai Naomi(Figs. 63A–G, 133H)
Stenus hirashimai Naomi, 1989: 49; Herman, 2001: 2214; Naomi & Puthz, 2013: 143.
Type material examined. Holotype: ♂ (KUF), Mt. Hiko, Fukuoka Pref., 4. ix. 1977, H.
Ohishi leg. Paratypes: 4 ♀, same data as holotype.
Other material examined. [KYUSHU]: 1 ♂1 ♀, Mt. Hiko, Fukuoka Pref., 21. v. 1986, S.
Nomura leg.; 1 ♂, Mt. Fukuchi, Nogata City, Fukuoka Pref., 21. iv. 1985, S. Nomura leg.
Distribution. Japan: Kyushu (Fukuoka Pref.).
Redescription. Male and female: Body 3.5–4.1 mm (fore body 1.7–2.0 mm) in length. Body

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Fig. 63. Stenus hirashimai Naomi (Fukuoka: Mt. Hiko). A, spermatheca; B, 9th and 10th terga of male; C,aedeagus; D, 9th ventrite of male; E, endophallic expulsion hooks; F, posterior part of gonocoxite; G, 7th and8th ventrites of male. Scale 1: 0.1 mm for A, F; scale 2: 0.1 mm for B–D, 0.05 mm for E; scale 3: 0.3 mm for
G.

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moderately shining; head black; pronotum and elytra reddish brown to dark red or dark brown;
abdomen dark red to dark brown or almost black; labrum reddish brown to dark brown; antennae
and legs yellowish brown to reddish brown. Body with punctures round to ovoidal, small tomoderately large, and also pronotum partially with coarse to subrugose punctures and elytra partially with large, coarse to subrugose punctures. Head shallowly to moderately concave, with apair of longitudinal-oblique or longitudinal furrows (or depressions); antennae moderately long,very thin; pronotum with surface slightly uneven to uneven, with a median longitudinal furrow
indistinct; elytra with surface slightly uneven to uneven or strongly uneven, each sometimes witha mediolateral keel at base and also with a longitudinal depression on each side of basal keel;
abdomen subcylindrical, thin to moderately thick or thick, slightly tapering posteriorly to subparallel-sided; lateroventrites and tergoventral sutures lost.
Male: Abdomen (Fig. 63G) modiﬁed with a shallow depression on the 7th, and an arcuate
emargination on the 8th ventrite; 9th tergum with ventral apophyses long; 9th ventrite (Fig. 63D)
with macrosetae very long, apicolateral teeth long, very acute, apicolateral setae long; 10th tergum very shallowly emarginate posteriorly. Aedeagus (Fig. 63C) with median lobe elongate, distinctly expanded laterally and obtusely angulate at apicolateral corners, obtusely pointed at apex;
apical sclerotized area large, subtriangular, basally with a broad, arcuate emargination. Endophallus (Fig. 63C) with copulatory tube having basal chamber elongate-ovoidal in shape, main tube
relatively short, almost needle-shaped; dorsolateral bands broad; expulsion hooks (Fig. 63E)
each with anterior plate turning anteriorly; ventromedian bands moderately long, moderately
broad. Parameres (Fig. 63C) long, each acutely pointed at apex; apical area very long, hardly
swollen mesially at base, mesially also with 3 short setae at base and 6 to 7 setae in the apical
2/3.
Female: Eighth ventrite obtuse posteromedially; gonocoxites (Fig. 63F) each with apicolateral tooth long, very acute, apicolateral setae very long. Spermatheca (Fig. 63A) with capsulelost; striped duct very long, thick to very thick; a unique, large, elongate sack located between
the striped duct and spermathecal duct, the basilateral part of which has a small, ovoidal gland;
duct short, moderately thick to very thick with 3 turns; basal valve very short; basal duct sclerotized, moderately long.
Biology and ecology. The beetles of S. hirashimai inhabit leaf litter heaped in the natural forests of mountainous regions.
Remarks. S. hirashimai is very unique in having the spermatheca with a large, elongate sacklocated between the striped duct and spermathecal duct (Fig. 133A). It is also noteworthy topoint out that such a large sack is found only in the spermatheca of S. hirashimai among the species of Japanese Stenus.
S. hirashimai is probably allied to S. yoshidai, but it is separable from the latter species by
the aedeagal median lobe broadest at the apicolateral corners (Fig. 63C), the copulatory tube withits main tube thinner (Fig. 63C), the endophallic expulsion hook with its anterior plate much longer (Fig. 63E), the paramere longer (Fig. 63C), and the spermatheca with its duct longer (Fig.
63A).
Etymology. This species is named after Dr. Yoshihiro Hirashima (Kyushu University,
Fukuoka) who studied the taxonomy of Hymenoptera.

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Fig. 64. Stenus yamajii Naomi & Puthz (Okayama: Niimi). A, aedeagus; B, 9th and 10th terga of male; C, 9th
ventrite of male; D, spermatheca and bursa copulatrix; E, 7th and 8th ventrites of male; F, posterior part ofgonocoxite; G, posterior part of 8th ventrite of female. Scale 1: 0.1 mm for A–C; scale 2: 0.1 mm for D, F,
0.2 mm for G; scale 3: 0.3 mm for E.

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Stenus yamajii Naomi & Puthz(Fig. 64A–G)
Stenus yamajii Naomi & Puthz, 1994a: 305; Herman, 2001: 2438; Naomi & Puthz, 2013: 144.
Type material examined. Holotype: ♂ (CBM), Mt. Kenashigasen, Shinsho Vil., Okayama
Pref., 4. v. 1989, O. Yamaji leg.
Other material examined. [HONSHU]: 1 ♀, Mt. Kenashi, Tottori City, Tottori Pref., 23. v.
1989, N. Tsurusaki leg. 2 ♂2 ♀, Hisaka, Niimi City, Okayama Pref., 8. v. 2004, O. Yamaji leg.
Distribution. Japan: Honshu (Tottori and Okayama Prefs.).
Redescription. Male and female: Body 3.0–3.8 mm (fore body 1.6–1.8 mm) in length. Body
weakly shining; head black, usually with median area reddish brown to dark red; pronotum andelytra reddish brown; abdomen dark red to dark brown; labrum reddish brown; antennae and legs
yellowish brown to reddish brown. Body with punctures round toovoidal, small to moderately
large, and also pronotum partially with subrugose punctures and elytra partially with large, subrugose punctures. Head moderately concave, with a pair of longitudinal-oblique furrows; antennae short to moderately long, very thin to thin; pronotum with surface uneven, with a medianlongitudinal furrow or a hollow indistinct; elytra with surface slightly uneven to uneven; abdomen subcylindrical, slightly tapering posteriorly to subparallel-sided; lateroventrites lost, tergoventrite sutures obsolete, extremely thin.
Male: Abdomen (Fig. 64E) modiﬁed with a shallow depression on the 7th, and a moderately
deep emarginatiom on the 8th ventrite; 9th tergum (Fig. 64B) with ventral apophyses long; 9th
ventrite (Fig. 64C) with apicolateral teeth short, very acute, apicolateral setae long; 10th tergum(Fig. 64B) entire. Aedeagus (Fig. 64A) with median lobe broad, moderately rounded at apicolateral corners, obtuse at apex; apical sclerotized area broad-subriangular in shape. Endophallus(Fig. 64A) with copulatory tube moderately long, with basal chamber well-developed, a little
shorter than main tube, main tube baculiform, swollen laterally at base, thick and obtuse at apex;
dorsolateral bands very thin; expulsion hooks each moderately broad, with posterior plate angulate or pointed at the middle of mesial part, acute at posterior tip; ventromedian bands very long,very broad. Parameres (Fig. 64A) slender, each very acutely pointed at apex; apical area long,mesially with 9 setae.
Female: Eighth ventrite (Fig. 64G) almost rounded posteriorly; gonocoxites (Fig. 64F) eachwith apicolateral tooth long, very acute, apicolateral setae long. Spermatheca (Fig. 64D) with
capsule very short, well-rounded apically; striped duct long, moderately thick; duct long, thin tomoderately thick, loosely coiled; gland elongate-spherical in shape, with opening located on thelateral side of duct between the last and last 2nd turns.
Biology and ecology. The beetles of S. yamajii inhabit leaf litter heaped in the natural forestsof mountainous regions.
Remarks. S. yamajii is allied to S. gion, but it is separable from the latter species by theaedeagal median lobe shorter, with its apical sclerotized area more developed (Fig. 64A), theendophallic expulsion hook broader (Fig. 64F), and the spermatheca with its duct much thinner(Fig. 64D).
Etymology. This species is named after Mr. Osamu Yamaji (Okayama) who collected theStenus-beetles designated as the type specimens.

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Fig. 65. Stenus gion Naomi & Ito (Kyoto: A, E, H, Asiu, B–D, F, Mt. Yuragadake, G, Maizuru). A, spermatheca;
B, aedeagus; C, 9th and 10th terga of male; D, posterior part of 8th ventrite of male; E, 9th ventrite of male; F,G, endophallic expulsion hooks; H, posterior part of gonocoxite. Scale 1: 0.05 mm for A, 0.1 mm for C, E;
scale 2: 0.1 mm for B, H, 0.2 mm for D, 0.05 mm for F, G.

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Stenus gion Naomi & Ito(Figs. 65A–H, 133I)
Stenus gion Naomi & Ito, 2018: 93.
Type material examined. Holotype: ♂ (OMNHO), Ashiu, Kyoto Pref., 5. ix. 1992, T. Ito leg.
Paratype: 1 ♀, same data as holotype.
Other material examined. [HONSHU]: 1 ♂, Mihama Pass, Maizuru City, Kyoto Pref., 15. vi.
2013, T. Ito leg.; 1 ♂, Mt. Yuragadake, Maizuru City, Kyoto Pref., 7. vi. 2010, K. Mizuno leg.
Distribution. Japan: Honshu (Kyoto Pref.).
Redescription. Male and female: Body 3.3–3.5 mm (fore body 1.5–1.7 mm) in length. Body
moderately shining; head black; pronotum and elytra reddish brown to dark red or almost black;abdomen dark red to dark brown or almost black; labrum reddish brown to dark red near black;antennae and legs yellowish brown to reddish brown. Body with punctures round to elliptical,
small to moderately large, and also pronotum partially with coarse to subrugose punctures andelytra partially with large, coarse to subrugose punctures. Head shallowly concave, with a pair of
longitudinal-oblique furrows; antennae very short to short, very thin; pronotum with surface
slightly uneven, with a median longitudinal depression hardly developed or very indistinct; elytra
a with surface slightly uneven to uneven; abdomen subcylindrical, slightly tapering posteriorly to
subparallel-sided; lateroventrites and tergoventral sutures lost.
Male: Abdomen (Fig. 65D) modiﬁed with an arcuate, very shallow emargination on the 8th
ventrite; 9th tergum (Fig. 65C) with ventral apophyses moderately long; 9th ventrite (Fig. 65E)
with apicolateral teeth long, thin, very acute, apicolateral setae moderately long; 10th tergum(Fig. 65C) very shallowly emarginate posteromedially. Aedeagus (Fig. 65B) with median lobe
elongate, subparallel-sided, obtusely angulate at apicolateral corners, obtusely pointed at apex;
apical sclerotized area weakly developed, anteriorly with an arcuate, very broad emargination.
Endophallus (Fig. 65B) with copulatory tube having basal chamber very large, elongate-ovoidal
in shape, main tube thick at base, attenuate, slightly curved and subulate at apex; dorsolateralbands thin, each without dots on the surface; expulsion hooks (Fig. 65F, G) connected each otherat the mesial corners of posterior plates (Fig. 65F), with anterior plate very small, almost triangular, posterior plate elongate, usually obtuse at posterior end; ventromedian bands long, moderately broad. Parameres (Fig. 65B) each very acutely pointed at apex; apical area very long, moderately broad dorsoventrally, mesially with 5 short setae.
Female: Eighth ventrite obtuse posteromedially; gonocoxites (Fig. 65H) each with apicolateral tooth short, thick, almost acute, apicolateral setae very long. Spermatheca (Fig. 65A) with
capsule short, well-rounded apically; striped duct long, very thick; duct long, thin to moderately
thick or thick, loosely coiled, sparsely tuberculate on the surface of the distal part of duct nearstriped duct; gland large, sparsely covered with very thin, moderately long ciliae, with opening
located on the lateral side of duct between the last 5th and 6th turns; basal valve long; basal duct
moderately long.
Biology and ecology. The beetles of S. gion inhabit leaf litter heaped in the natural forests oflow mountainous regions.
Remarks. S. gion is allied to S. yamajii, but it is separable from the latter species by theaedeagal median lobe longer, with its apical sclerotized area less developed (Fig. 65B), the endophallic expulsion hook thinner (Fig. 65F, G), and the spermatheca with its duct much thicker(Fig. 65D).

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Fig. 66. Stenus inclarescens Puthz (Ishikawa: A, B, F, G, Fukamizu; Toyama: C–E, H, I, Fukusawa). A, 9th and10th terga of male; B, 7th and 8th ventrites of male; C, 9th ventrite of male; D, aedeagus; E, spermatheca; F,
endophallic expulsion hooks; G, copulatory tube; H, posterior part of 8th ventrite of female; I, posterior partof gonocoxite. Scale 1: 0.2 mm for A, H, 0.1 mm for F, G, I; scale 2: 0.3 mm for B; scale 3: 0.1 mm for C, D;
scale 4: 0.1 mm for E.

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Etymology. The speciﬁc epithet of this species is derived from the name of a summer festival
in Kyoto, Gion.
Stenus inclarescens Puthz(Figs. 66A–I, 133J)
Stenus inclarescens Puthz, 1993: 151; Herman, 2001: 2228; Naomi & Puthz, 2013: 144.
Type material examined. Holotype: ♂ (NHMG), Fukusawa (200 m), Kamini(i)kawa, Toyama
Pref., 29. vii. 1980, I. Löbl leg. Paratype: 1 ♀, same data as holotype.
Other material examined. [HONSHU]: 4 ♂4 ♀, Fukumizu, Hakui City, Ishikawa Pref., 11. v.
1995, T. Kishimoto leg.
Distribution. Japan: Honshu (Toyama and Ishikawa Prefs.).
Redescription. Male and female: Body 3.3–3.6 mm (fore body 1.7–1.8 mm) in length. Body
moderately shining; head black with median area reddish brown; pronotum and abdomen reddish
brown to dark reddish brown; elytra pale yellowish brown to yellowish brown; labrum reddish
brown; antennae and legs yellowish brown. Body with punctures round to ovoidal, small to moderately large, and also pronotum partially with coarse to subrugose punctures and elytra partiallywith large, coarse to subrugose punctures. Head shallowly to moderately concave, with a pair of
longitudinal-oblique furrows or depressions; antennae short, very thin; pronotum with surface
slightly uneven, with a median longitudinal depression hardly developed; elytra a with surface
slightly uneven to uneven; abdomen subcylindrical, slightly tapering posteriorly or subparallelsided; lateroventrites and tergoventral sutures lost.
Male: Abdomen (Fig. 66B) modiﬁed with a very shallow depression on the 7th, and an arcuate, very shallow emargination on the 8th ventrite; 9th tergum (Fig. 66A) with ventral apophyses
very long; 9th ventrite (Fig. 66C) with macrosetae very long, apicolateral teeth short, almost
acute, apicolateral setae moderately long; 10th tergum (Fig. 66A) very shallowly emarginate posteromedially. Aedeagus (Fig. 66D) with median lobe moderately broad, well-rounded at apicolateral corners, narrowly rounded apically; apical sclerotized area broad-subtriangular in shape.
Endophallus (Fig. 66D) with copulatory tube (Fig. 66G) having main tube baculiform but
slightly sinuous; expulsion hooks (Fig. 66D, F) each distinctly curved laterally, with anterior
plate obtusely pointed or pointed at anterior tip; ventromedian bands slightly short, moderately
broad. Parameres (Fig. 66D) short, moderately thick, each acutely pointed at apex; apical area
short, becoming distinctly thinner apicad, mesially with 8 setae.
Female: Eighth ventrite obtuse or distinctly pointed (Fig. 66H) posteromedially; gonocoxites(Fig. 66I) each with apicolateral tooth long, very acute, apicolateral setae long. Spermatheca(Fig. 66E) with capsule half-spherical; striped duct short; duct slightly short, moderately thick,coiled with 4 turns.
Biology and ecology. The beetles of S. inclarescens inhabit leaf litter heaped in the naturalforests of lowlands.
Remarks. S. inclarescens is allied to S. fulidus, S. notomontis and S. obtusus, but it is separable from the latter 3 species by the aedeagal median lobe not protruding posteriorly at the apicomedian part (Fig. 66D), and the paramere shorter and not reaching the apex of median lobe (Fig.
66D).

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Fig. 67. Stenus fulvidus Naomi, Nomura & Puthz sp. nov. (Ishikawa: Nabetani). A, 9th ventrite of male; B, 9th
and 10th terga of male; C, aedeagus; D, endophallic expulsion hooks; E, 7th and 8th ventrites of male; F, spermatheca; G, copulatory tube; H, posterior part of gonocoxite. Scale 1: 0.1 mm for A, B; scale 2: 0.1 mm for C,
F–H, 0.05 mm for D; scale 3: 0.5 mm for E.

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Stenus fulvidus Naomi, Nomura & Puthz sp. nov.
(Fig. 67A–H)
Type material examined. Holotype: ♂ (KUMF), Nabetani, Tatsunokuchi-cho, Ishikawa Pref.,28. v. 1995, Y. Sugie leg. Paratypes: 2 ♂1 ♀, same data as holotype; 1 ♂, same locality, 7. vi.
1995, Y. Sugie leg.; 1 ♂, Shijyutani-cho, Fukui City, Fukui Pref., 9. vii. 2001, H. Hoshina leg.
Distribution. Japan: Honshu (Ishikawa and Fukui Prefs.).
Description. Male and female: Body 3.2–3.5 mm (fore body 1.5–1.7 mm) in length. Body
moderately shining; head black; pronotum and abdomen dark red; elytra almost yellowish brown
to reddish brown; labrum reddish brown; antennae and legs reddish brown. Body with puncturesround to elliptical, small to moderately large, and also pronotum partially with coarse to subrugose punctures and elytra partially with large, coarse to subrugose punctures. Head moderately
concave, with a pair of longitudinal-oblique furrows; antennae short to moderately long, very
thin; pronotum with surface slightly uneven, with a median longitudinal depression hardly developed to very indistinct or indistinct; elytra a with surface almost even to slightly uneven or
uneven, and also sometimes centrally with a pair of vague, infuscate, round maculae; abdomensubcylindrical, slightly tapering posteriorly; lateroventrites and tergoventral sutures lost.
Male: Abdomen (Fig. 67E) modiﬁed with a ﬂat area on the 7th, and an arcuate, broad, very
shallow emargination on the 8th ventrite; 9th tergum (Fig. 67B) with ventral apophyses slightly
short, broad when seen laterally; 9th ventrite (Fig. 67A) with macrosetae long, apicolateral teeth
moderately long, thin, very acute, apicolateral setae long; 10th tergum (Fig. 67C) very shallowly
emarginate posteriorly. Aedeagus (Fig. 67C) with median lobe almost rounded at apicolateralcorners, with a short, rounded apicomedian protrusion; apical sclerotized area very shallowly,
arcuately emarginate apicolaterally. Endophallus with copulatory tube (Fig. 67G) having basal
chamber elongate, main tube slender, very slightly attenuate; expulsion hooks (Fig. 67D) eachwith anterior plate divided anteroposteriorly into two subplates, much smaller than posterior
plate, posterior plate obtusely angulate at posterior tip. Parameres (Fig. 67C) each acutely
pointed at apex; apical area very long, mesially with 4 or 5 thick setae at base and 5 thin setae ofvarious length in the apical 1/2 or 2/3.
Female: gonocoxites (Fig. 67H) each with apicolateral tooth moderately long, thin, very
acute, apicolateral setae very long. Spermatheca (Fig. 67F) with capsule large, almost roundedapically; striped duct very short, thick; duct short, slightly thin to thick, coiled with 7 turns; basal
valve moderately long; basal duct moderately long.
Biology and ecology. The beetles of S. fulvidus inhabit leaf litter heaped in the natural forestsof lowlands to low mountainous regions.
Remarks. S. fulvidus is allied to S. notomontus, but it is separable from the latter species by
the aedeagal median lobe with the rounded apicomedian protrusion (Fig. 67C), the paramerewith its apical area mesially with 4 or 5 thick setae at base (Fig. 67C), and the endophallic expulsion hook with its anterior plate divided into two subplates (Fig. 67D).
Etymology. The speciﬁc epithet of this new species is derived from the Latin adjective fulvidus which means ʻsomewhat tawnyʼ. The elytra of this species are sometimes tawny in color,which is unusual in the Japanese species of cephalotes-group.

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Fig. 68. Stenus notomontis Naomi, Nomura & Puthz sp. nov. (Ishikawa: Mt. Horyu). A, aedeagus; B, 9th ventriteof male; C, 9th and 10th terga of male; D, 8th ventrite of male; E, 7th ventrite of male; F, endophallic expulsion hooks. Scale 1: 0.1 mm for A, B; scale 2: 0.2 mm for C, D, 0.1 mm for F; scale 3: 0.25 mm for E.

Stenus notomontis Naomi, Nomura & Puthz sp. nov.
(Fig. 68A–F)
Type material examined. Holotype: ♂ (KUMF), Mt. Horyu, Noto Peninsula, Ishikawa Pref.,The Steninae of Japan Part 3

161

6. v. 1961, Y. Hayashi leg.
Distribution. Japan: Honshu (Ishikawa Pref.).
Description. Male: Body 3.6 mm (fore body 1.7 mm) in length. Body moderately shining;head black; pronotum and abdomen dark red to dark brown; elytra reddish brown; labrum reddish brown to dark red near black; antennae and legs yellowish brown to reddish brown. Body
with punctures round to elliptical, small to moderately large, and also pronotum partially with
subrugose punctures and elytra partially with large, subrugose punctures. Head shallowly concave, with a pair of longitudinal-oblique depressions; antennae moderately long, thin; pronotumwith surface slightly uneven, with a median longitudinal depression indistinct; elytra a with surface uneven; abdomen subcylindrical, slightly tapering posteriorly; lateroventrites and tergoventral sutures lost.
Abdomen (Fig. 68E, D) modiﬁed with a ﬂat area on the 7th (Fig. 68E), and an arcuate, very
shallow emargination on the 8th ventrite (Fig. 68D); 9th tergum (Fig. 68C) with ventral apophyses long; 9th ventrite (Fig. 68B) with macrosetae very long, apicolateral teeth short, thin, acute,apicolateral setae long; 10th tergum (Fig. 68C) entire. Aedeagus (Fig. 68A) with median lobe
moderately broad, well-rounded at apicolateral corners, with a short, truncate apicomedian protrusion; apical sclerotized area with a median longitudinal line. Endophallus (Fig. 68A) with copulatory tube having main tube slender, almost baculiform, with basal tube demarcated a little
before the middle by a weak constriction from apical tube; dorsolateral bands very thin; expulsion hooks (Fig. 68F) each with anterior plate minutely incurved mesially at anterior tip, posterior plate angulate at the middle of mesial part, turning posterolaterally behind the angulation;
ventromedian bands moderately long, broad. Parameres (Fig. 68A) each very acutely pointed atapex; apical area long, thin, mesially with 6 to 9 setae.
Female: Unknown.
Biology and ecology. The beetle of S. notomontis inhabits leaf litter heaped in the natural forest of a low mountainous region.
Remarks. S. notomontis is allied to S. fulvidus, but it is separable from the latter species by
the aedeagal median lobe with the truncate apicomedian protrusion (Fig. 68A), the endophallic
expulsion hook with its anterior plate entirely solid (Fig. 68F), and the paramere with its apicalarea glabrous at base (Fig. 68A).
Etymology. The speciﬁc epithet of this new species is derived from the name of type locality,
Noto and the genitivus of Latin noun mons (masculine), montis which means ʻof mountainʼ.
Stenus obtusus Naomi, Nomura & Puthz sp. nov.
(Fig. 69A–H)
Type material examined. Holotype: ♂ (KUMF), Nabetani, Tatsunokuchi-cho, Ishikawa Pref.,7. vi. 1995, Y. Sugie leg. Paratypes: 1 ♂2 ♀, same data as holotype.
Distribution. Japan: Honshu (Ishikawa Pref.).
Description. Male and female: Body 3.3–3.5 mm (fore body 1.6–1.7 mm) in length. Body
moderately shining; head black; pronotum and abdomen dark red to almost black; elytra yellowish brown to reddish brown; labrum reddish brown; antennae and legs yellowish brown to reddish brown. Body with punctures round to elliptical, small to moderately large, and also pronotum partially with coarse to subrugose punctures and elytra partially with large, coarse tosubrugose punctures. Head shallowly to moderately concave, with a pair of longitudinal-obliquefurrows; antennae short to moderately long, very thin; pronotum with surface slightly uneven to162

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Fig. 69. Stenus obtusus Naomi, Nomura & Puthz sp. nov. (Ishikawa: Nabetani). A, 9th and 10th terga of male; B,
6th to 8th ventrites of male; C, 9th ventrite of male; D, aedeagus; E, spermatheca; F, copulatory tube; G, endophallic expulsion hooks; H, posterior part of gonocoxite. Scale 1: 0.2 mm for A, C, 0.1 mm for E–H; scale 2:0.25 mm for B scale 3: 0.1 mm for D.

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uneven, with a median longitudinal depression very indistinct or indistinct; elytra a with surface
slightly uneven or uneven; abdomen subcylindrical, slightly tapering posteriorly; lateroventrites
and tergoventral sutures lost.
Male: Abdomen (Fig. 69B) modiﬁed with a ﬂat area on the 6th, a very shallow depression on
the 7th, and an arcuate, shallow emargination on the 8th ventrite; 9th tergum (Fig. 69A) withventral apophyses long; 9th ventrite (Fig. 69C) with macrosetae long, apicolateral teeth short,very acute, apicolateral setae slightly short; 10th tergum (Fig. 69C) almost rounded posteriorly.
Aedeagus (Fig. 69D) with median lobe rounded at apicolateral corners, with a moderately long,almost rounded apicomedian protrusion; apical sclerotized area shallowly, arcuately emarginate
apicolaterally. Endophallus (Fig. 69D) with copulatory tube (Fig. 69F) having main tube very
long, moderately curved apically; expulsion hooks (Fig. 69G) each somewhat hollow mesially,
with anterior and posterior plates each moderately rounded laterally. Parameres (Fig. 69D) eachcovered sporadically with very small pores on the surface of pedicel, acutely pointed at apex;
apical area short, mesially with 8 to 9 setae.
Female: Eighth ventrite obtuse posteromedially; gonocoxites (Fig. 69H) each with apicolateral tooth short, acute, apicolateral setae slightly short. Spermatheca (Fig. 69E) with capsulelarge; striped duct very short, thick; duct moderately long, moderately thick to thick, tightly
coiled; basal valve short; basal duct very long; basal pouch large, conical, membranous.
Biology and ecology. The beetles of S. obtusus inhabit leaf litter heaped in the natural forestsof a lowland (or a low mountainous region?).
Remarks. S. obtusus is allied to S. fulvidus and S. notomontus, but it is separable from the latter 2 species by the aedeagal median lobe with the moderately long apicomedian protrusion (Fig.
69D), the endophallic expulsion hook somewhat hollow mesially (Fig. 69G), and the paramerewith its apical area short (Fig. 69D).
Etymology. The speciﬁc epithet of this new species is derived from the Latin adjective obtusus which means ʻobtuse.ʼ The 8th ventrite of female abdomen is obtuse posteromedially.
Stenus snodgrassi Naomi(Fig. 70A–G)
Stenus snodgrassi Naomi, 2021: 65.
Type material examined. Holotype: ♂ (KUMF), Sengodani, Takefu, Fukui Pref., Y. Oyama leg.
Distribution. Japan: Honshu (Fukui Pref.).
Description. Male: Body 3.3 mm (fore body 1.6 mm) in length. Body moderately shining;head black; pronotum almost black; elytra yellowish brown; abdomen reddish brown to darkbrown; labrum reddish brown; antennae with basal segments yellowish brown, apical segment
dark red; legs yellowish brown. Body with punctures round to elliptical, small to moderately
large, and also pronotum partially with subrugose punctures and elytra partially with large,coarse punctures. Head moderately concave, with a pair of longitudinal-oblique furrows; antennae moderately long, very thin; pronotum with surface uneven, with a median longitudinal
depression very indistinct; elytra (Fig. C) with surface almost even; abdomen subcylindrical,
slightly tapering posteriorly; lateroventrites and tergoventral sutures lost.
Abdomen (Fig. 70B) modiﬁed with a slightly deep depression area on the 6th, a large, moderately deep median depression (which unusually becomes deeper and broader anteriad) on the
7th, and an arcuate, shallow emargination on the 8th ventrite; 9th tergum as in Fig. 70A; 9th ven-

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Fig. 70. Stenus snodgrassi Naomi (Fukui: Takefu). A, 9th and 10th terga of male; B, 6th to 8th ventrites of male;C, mesoscutellum and right elytron; D, 9th ventrite of male; E, aedeagus; F, endophallic expulsion hooks; G,basal foramen of aedeagal median lobe. Scale 1: 0.1 mm for A, D, E; scale 2: 0.25 mm for B, C; scale 3:0.05 mm for F, 0.1 mm for G.

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trite (Fig. 70D) with apicolateral teeth very short, very acute, apicolateral setae moderately long;
10th tergum (Fig. 70A) very shallowly emarginate posteriorly. Aedeagus (Fig. 70E) with median
lobe slender, rounded at apicolateral corners, with a moderately long, subtruncate apicomedian
protrusion; apical sclerotized area shallowly, arcuately emarginate apicolaterally; basal foramen(Fig. 70G) with its posterior sclerotized rim anteromedially having a small notch and extending
anteriorly to form an almost C-shaped additional frame. Endophallus (Fig. 70D) with copulatory
tube long, having basal chamber almost ovoidal, main tube strongly swollen laterally near the
middle, and then thin and moderately curved apically; expulsion hooks (Fig. 70F) each moderately constricted at the middle, with posterior plate distinctly broadened posteriad, strongly protruding almost posterolaterally. Parameres (Fig. 70E, G) each with pedicel moderately thick.
Female: Unknown.
Biology and ecology. The beetle of S. snodgrassi inhabits leaf litter heaped in the natural forest of a lowland.
Remarks. S. snodgrassi is a distinct species due to the impressive coloration of body by thetawny elytra and the 7th ventrite of male with its median depression unusually becoming deeper
anteriad. This species is allied to S. fulvidus, S. notomontus and S. obtusus, but it is separablefrom the latter 3 species by the aedeagal median lobe more slender (Fig. 70E), the copulatory
tube with its main tube strongly swollen in a subfusiform shape in the middle (Fig. 70E), and theendophallic expulsion hook more strongly constricted at the middle (Fig. 70F), in addition to theafore-mentioned impressive character conditions of this species.
Etymology. This new species is named after an American morphologist, the late Dr. Robert
E. Snodgrass (United States Department of Agriculture) who made important contributions to thedevelopment of the principles of insect morphology.
Stenus coiﬀaitiellus Naomi & Puthz(Figs. 71A–J, 133K)
Stenus coiﬀaitiellus Naomi & Puthz, 1993: 303; Herman, 2001: 2132; Naomi & Puthz, 2013:
144.
Stenus rufescens Hromádka, 1982: 131 (in part).
Type material examined. Holotype: ♂ (SMNHS), Shimajiyama, Ise City, Mie Pref., 27. vii.
1957, H. Coiﬀait leg. Paratype: 1 ♂ (cP), same data as holotype.
Other material examined. [HONSHU]: 3 ♂2 ♀, Mt. Aomine, Toba, Mie Pref., 17. viii. 1988,
T. Ito leg.; 3 ♂3 ♀, Koraibiro, Ise City, Mie Pref., 10. i. 1998, M. Yokozeki leg.; 1 ♂, Mt. Kuragatake, Ishikawa Pref., 4. v. 1964, Y. Hayashi leg.; 4 ♂5 ♀, Minami-rokuroshi, Oono City, Fukui
Pref., 3. vii. 2001, H. Hoshina leg.
Distribution. Japan: Honshu (Ishikawa, Fukui and Mie Prefs.).
Redescription. Male and female: Body 3.2–3.5 mm (fore body 1.5–1.7 mm) in length. Body
moderately shining; head black, usually with median area dark red; pronotum reddish orange to
reddish brown or dark red; elytra reddish orange through yellowish or reddish brown to dark red;abdomen reddish brown to dark brown, with apical segments almost black, or dark red near
black; labrum reddish brown to dark red; antennae and legs yellowish brown to reddish brown.
Body with punctures round to elliptical, small to moderately large, and also pronotum partiallywith coarse puncture and elytra partially with large, subrugose punctures. Head shallowly tomoderately concave, with a pair of longitudinal-oblique or longitudinal furrows (or depressions);

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Fig. 71. Stenus coiﬀaitiellus Naomi & Puthz (Mie: A–C, Aomine, D, E, G, H, Koraibiro, Toba, F, I, J). A, gonocoxite; B, 9th ventrite of male; C, spermatheca; D, aedeagus; E, 6th and 7th ventrites of male; F, 9th and 10th
terga of male; G, copulatory tube; H, endophallic expulsion hooks; I, posterior part of 8th ventrite of female;J, posterior part of 8th ventrite of male. Scale 1: 0.1 mm for A, C, G, H, 0.2 mm for B, D, F, I, J; scale 2:0.25 mm for E.

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antennae short to moderately long, very thin; pronotum with surface slightly uneven, with a
median longitudinal furrow very indistinct to indistinct; elytra with surface slightly uneven to
uneven; abdomen subcylindrical, weakly tapering posteriorly; lateroventrites and tergoventrite
sutures lost.
Male: Abdomen modiﬁed with a ﬂat area on the 7th (Fig. 71E) and a broad, shallow emargination on the 8th (Fig. 71J) ventrites; 9th tergum (Fig. F) with ventral apophyses slightly short;
9th ventrite (Fig. 71B) with apicolateral teeth short, very acute, apicolateral setae short; 10th tergum (Fig. 71F) shallowly emarginate posteromedially. Aedeagus (Fig. 71D) with median lobe
broadest, much rounded and also more or less expanding laterally at anterolateral corners, very
minutely pointed at apicomedian part; apical sclerotized area only weakly developed. Endophallus (Fig. 71D) with copulatory tube (Fig. 71G) having rods of basal chamber very long, eachthin, main tube slightly short, thin, attenuate; expulsion hooks (Fig. 71H) each protruding both atanterolateral and posterolateral corners; ventromedian bands very short, thin. Parameres (Fig.
71D) slender, long, each very acutely pointed at apex; apical area long, mesially with 8 setae.
Female: Eighth ventrite (Fig. 71I) obtuse posteromedially; gonocoxites (Fig. 71A) each withapicolateral teeth very long, acutely pointed, apicolateral setae very long. Spermatheca (Fig.
71C) with capsule elongate; striped duct moderately long, thick; duct long, thin to moderately
thick or thick, coiled with 10 turns; gland very large, spherical, with opening located on the duct
between the 7th and 8th turns; basal valve very short; basal duct well-developed, strongly sclerotized, moderately thick.
Biology and ecology. The beetles of S. coiﬀatiellus inhabit leaf litter heaped in the naturalforests of low mountainous to mountainous regions.
Remarks. S. coiﬀatiellus is allied to S. productus, but it is separable from the latter species by
the aedeagal median lobe very minutely pointed and solid at the apicomedian part (Fig. 71D), thecopulatory tube with its main tube attenuate (Fig. 71G), and the spermatheca with its proximal
part of duct and basal duct much thinner (Fig. 71C).
In S. coiﬀaitiellus, there are 3 forms of variations regarding the coloration of body as follows: (1) Head black, with clypeofrontal area and median longitudinal swollen area dark red,pronotum and elytra reddish orange to reddish brown, abdomen dark red to dark red near black,or reddish brown with apical segments dark red near black; (2) head black, pronotum and abdomen dark red near black, elytra yellowish brown to reddish brown; (3) head black, pronotum,
elytra and abdomen dark red to dark red near black. The 1st form tends to be found in the specimens from Mie Pref., while the 2nd and 3rd forms tend to be found in the specimens from Fukui
Pref.
Etymology. This species is named after a French staphylinist, the late Dr. Henri Coiﬀait (Faculty of Science, Toulouse) who contributed to the Staphylinid taxonomy of Europe. He collected
the Stenus-beetles designated as the type specimens of this species.
Stenus productus Naomi(Figs. 72A–J, 133 L)
Stenus productus Naomi, 2007: 71; Naomi & Puthz, 2013: 144.
Type material examined. Holotype: ♂ (CBM), Kawakami, Omiya, Watarai-gun, Mie Pref.,11. ii. 1997, F. Ichikawa leg. Paratypes: 1 ♂, Sazaraura, Nansei-cho, Watarai-gun, Mie Pref., 3.
iii. 1998, A. Amagasu leg.; 2 ♂4 ♀, Kajiya Pass, Yokowa, Ise City, Mie Pref., 23. ii. 1997, F.

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Fig. 72. Stenus productus Naomi (Mie: A, Sazaraura, B, D, F, H, J, Tsurugi Pass, C, E, G, Watarai, I, Fujisaka
Pass). A, 9th and 10th terga of male; B, aedeagus; C, spermatheca; D, 6th and 7th ventrites of male; E, 9th
ventrite of male; F, copulatory tube; G, gonocoxite; H, posterior part of 8th ventrite of male; I, posterior partof 8th ventrite of female; J, endophallic expulsion hooks. Scale 1: 0.2 mm for A, B, E, I, 0.1 mm for C, F, G, J;
scale 2: 0.25 mm for D; scale 3: 0.25 mm for H.

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Ichikawa leg.; 1 ♂, Oshibuchi, Nansei City, Mie Pref., 13. iii. 1994, H. Yokozeki leg.; 1 ♂6 ♀,Tsurugi Pass, Ise City, Mie Pref., 31. i. 1998, A. Amagasu leg.; 2 ♂1 ♀, Sengyu Shrine, Nanto,
Watarai-gun, Mie Pref., 11. ii. 1997, F. Ichikawa leg.; 1 ♂5 ♀, Fujisaka Pass, Nanto-cho, Wataraigun, Mie Pref., 14. iii. 1996, H. Yokozeki leg.
Distribution. Japan: Honshu (Mie Pref.).
Redescription. Male and female: Body 2.8–3.7 mm (fore body 1.4–1.7 mm) in length. Body
weakly or moderately shining; head black, sometimes with median area dark red; pronotum andelytra reddish orange to reddish brown or dark red; abdomen dark red to almost black; labrum
reddish brown; antennae and legs yellowish brown to reddish brown. Body with punctures roundto ovoidal, small (as on the 6th abdominal segment; Fig. 72D) to moderately large, and also pronotum partially with coarse punctures and elytra partially with large, coarse to subrugose punctures. Head shallowly to moderately concave, with a pair of longitudinal-oblique furrows or
depressions; antennae short to moderately long, very thin to thin; pronotum with surface slightly
uneven, with a median longitudinal furrow indistinct to almost distinct; elytra with surface
slightly uneven to uneven; abdomen subcylindrical, slightly tapering posteriorly; lateroventrites
and tergoventrite sutures lost.
Abdomen (Fig. 72D) modiﬁed with a ﬂat area on the 7th, and a broad, very shallow emargination on the 8th (Fig. 72H) ventrite; 9th tergum (Fig. 72A) with ventral apophyses slightly
short; 9th ventrite (Fig. 72E) with apicolateral teeth very short, acute, apicolateral setae short;
10th tergum (Fig. 72A) very shallowly emarginate posteromedially. Aedeagus (Fig. 72B) withmedian lobe broadest, angulate and also moderately expanding laterally at anterolateral corners,
very minutely pointed at apicomedian part, obtuse and submembranous at the apicomedian part;
apical sclerotized area subtriangular, basally with a large, arcuate emargination. Endophallus(Fig. 72B) with copulatory tube (Fig. 72F) having basal chamber very long, main tube spatulate,asymmetrical, acute at apex; expulsion hooks (Fig. 72J) each with posterior plate strongly protruding at posterolateral corners; ventromedian bands very short, moderately broad. Parameresvery long, very thin, each moderately curved mesially, strongly pointed at apex; apical area long,mesially with 3 setae.
Female: Eighth ventrite (Fig. 72I) obtuse posteromedially; gonocoxites (Fig. 72G) each withapicolateral teeth long, almost acute, apicolateral setae long. Spermatheca (Fig. 72C) with capsule hardly developed; striped duct moderately long, very thick; duct long, thin to moderately
thick in most length of duct, extremely thick at base, loosely coiled; gland very small, almost
fusiform, with opening located on the duct between the last 5th and 6th turns; basal valve
extremely short; basal duct robust, extremely thick.
Biology and ecology. The beetles of S. productus inhabit leaf litter heaped in the natural forests of lowlands to low mountainous regions.
Remarks. S. productus is allied to S. coiﬀatiellus, but it is separable from the latter species by
the aedeagal median lobe obtuse and submembranous at the apicomedian part (Fig. 72B), thecopulatory tube with its main tube spatulate (Fig. 72F), and the spermatheca with its proximal
part of duct and basal duct much thicker (Fig. 72C).
Stenus maiko Naomi & Puthz(Fig. 73A–F)
Stenus maiko Naomi & Puthz, 1993: 306; Herman, 2001: 2271; Naomi & Puthz, 2013: 144.

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Fig. 73. Stenus maiko Naomi & Puthz (Shiga: Mt. Ibuki). A, 9th and 10th terga of male; B, aedeagus; C, 6th and7th ventrites of male; D, 8th tergum of male; E, 8th ventrite of male; F, right elytron. Scale 1: 0.1 mm for A, B;
scale 2: 0.2 mm for C, F; scale 3: 0.2 mm for D, E.

leg.

Type material examined. Holotype: ♂ (cP), Mt. Ibuki, Shiga Pref., 1. xi. 1973, K. Sawada

Distribution. Japan: Honshu (Shiga Pref.).
Redescription. Male: Body 2.5 mm (fore body 1.3 mm) in length. Body weakly shining; headdark brown, with median area reddish brown to brown; pronotum and elytra pale yellowish
brown; abdomen yellowish brown to pale brown, becoming paler in color posteriod; labrum pale

The Steninae of Japan Part 3

171yellowish brown; antennae and legs yellowish brown to dark brown. Body with punctures roundto elliptical, small to moderately large, and also pronotum partially with coarse punctures andelytra partially with large (Fig. 73F), subrugose punctures. Head moderately concave, with a pairof longitudinal-oblique furrows; antennae moderately long, very thin; pronotum with surface
slightly uneven, with a median longitudinal furrow very indistinct; elytra with surface uneven;abdomen subcylindrical, subparallel-sided; lateroventrites and tergoventrite sutures lost.
Abdomen (Fig. 73C) modiﬁed with a ﬂat area on the 6th, an elongate, shallow depression on
the 7th, and a very broad, very shallow emargination on the 8th (Fig. 73E) ventrite; 9th tergum(Fig. 73A) with ventral apophyses long; 10th tergum (Fig. 73A) shallowly, arcuately emarginate
posteromedially. Aedeagus (Fig. 73B) with median lobe broadest, well-angulate and moderately
expanding laterally at anterolateral corners, acute at apex; apical sclerotized area with its apicomedian subtriangular portion narrower than the breadth of median lobe at apicolateral corners,
basally with an arcuate, broad emargination, medially with an incomplete longitudinal line, andalso with very sparse, very short, thin setae along posterior margin. Endophallus (Fig. 73B) withcopulatory tube having main tube very thick, strongly tapering apicad behind the middle; dorsolateral bands thick at base; expulsion hooks each subtriangular, with anterior plate narrowed
anteriad, almost acute at anterior tip, much smaller and narrower than posterior plate; ventromedian bands moderately long, moderately broad. Parameres (Fig. 73B) each acutely pointed atapex; apical area long, slightly swollen mesially, mesially also with 13 setae.
Female: Unknown.
Biology and ecology. S. maiko is a rare species which is known only by the teneral adult beetle designated as the holotype specimen. The beetle of this species inhabits leaf litter heaped in
the natural forest of a mountainous region.
Remarks. S. maiko is allied to S. coiﬀatiellus and S. productus, but it is separable from thelatter two species by the aedeagal median lobe acute at the apex (Fig. 73B) and the copulatory
tube with its main tube very thick (Fig. 73B). The description of this species is based on a teneral
specimen of male.
Etymology. The speciﬁc epithet of this species is derived from the Japanese name of apprentice dancer, maiko.
Species unit 2 of the rufescens-subgroup
Key to the Japanese species of the rufescens-subgroup (2)This is a key for a unit of Stenus-species (28 species) beginning with S. matobai and probably diagnosed with the combination of following character conditions: Third, 4th or 5th to 8th
ventrites often variously modiﬁed with depressions, emarginations, ridges, etc. (Fig. 77C); 6th
and 7th ventrites often developed with moderately deep and/or deeper depressions (Fig. 94E);
aedeagal median lobe slender (Fig. 75G) to slightly or moderately broad (Fig. 92B), or rarely
moderately broad at base and also moderately broad even at apicolateral corners (Fig. 80A), usually with apical sclerotized area triangular (Fig. 87G) to subtriangular (Fig. 77F), very often having a thin, apicomedian cusp and also a median longitudinal line (Fig. 100B); paramere with apical area usually long, slender and very acutely pointed at apex (Fig. 88B).
Distribution. Japan: Honshu (Chubu, Kinki and Chugoku Districts), Shikoku and Kyushu.
1(38) Male: Aedeagal median lobe with apical sclerotized area not having a median longitudi-

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nal line or having a median longitudinal line running at most in about apical 2/3; endophallic expulsion hooks various in shape.
2(33) Male: Endophallic expulsion hook dorsally without any process. Female: Spermathecawith basal duct usually thin to moderately thick, and about as broad as proximal part ofspermathecal duct (as far as the spermatheca is known.)
3(4) Male: Aedeagal median lobe almost rounded apically (Fig. 74F) ........... S. matobai Naomi
4(3) Male: Aedeagal median lobe not rounded apically.
5(16) Male: Copulatory tube not or hardly modiﬁed, namely, attenuate, almost straight or only
slightly curved.
6(7) Male: Aedeagal median lobe with apical sclerotized area hardly developed (Fig. 76C);
endophallic expulsion hook with anterior plate antero-posteriorly divided into 2 subplates(Fig. 76E) ..............................................................................................S. toshiharui Naomi
7(6) Male: Aedeagal median lobe with apical sclerotized area more or less developed; endophallic expulsion hook with anterior plate not divided into 2 subplates.
8(9) Male: Endophallic expulsion hook with posterior plate strongly curved laterally, pointed
at apex (Fig. 75E).........................................................................S. kagura Naomi & Puthz
9(8) Male: Endophallic expulsion hook with posterior plate not curved laterally, rounded or
obtusely angulate at posterolateral part.
10(15) Male: Eighth ventrite more deeply emarginate posteriorly or posteromedially; endophallic
expulsion hook with posterior plate rounded at posterolateral part.
11(12) Male: Endophallic expulsion hook with posterior plate covered with very minute tubercles at posterolateral part (Fig. 77J); aedeagal paramere less strongly pointed at apex (Fig.
77C).............................................................................................................S. akome Naomi
12(11) Male: Endophallic expulsion hook with posterior plate smooth at posterolateral part;aedeagal paramere more strongly pointed at apex.
13(14) Male: Aedeagal median lobe narrower at apicolateral corners (Fig. 85E); endophallic
expulsion hook narrower (Fig. 85A) ..................................................... S. jukata Hromádka
14(13) Male: Aedeagal median lobe broader at apicolateral corners (Fig. 86A); endophallic
expulsion hook broader (Fig. 86G) ............................................................... S. ferus Naomi
15(10) Male: Eighth ventrite more shallowly emarginate posteriorly (Fig. 88F); endophallic
expulsion hook with posterior plate obtusely angulate at posterolateral part (Fig. 88G) .....
................................................................................................................ S. ohtoensis Naomi
16(5) Male: Copulatory tube variously modiﬁed with distinct curvature, thickening, etc.
17(28) Male: Copulatory tube with apical tube normally, smoothly jointed with basal tube,
almost always without a distinct joint or demarcation line between the basal and apicaltubes.
18(23) Male: Copulatory tube not or only slightly curved on its way.
19(22) Male: Aedeagal median lobe with apical sclerotized area covered at least partially withthe parallel or apically converging, longitudinal lines.
20(21) Male: Aedeagal median lobe rounded at apicolateral corners, with apical sclerotized area
almost triangular (Fig. 78A); copulatory tube extremely aciculate at apex (Fig. 78B) ........
..................................................................................... S. incumbens Naomi & Y. Watanabe
21(20) Male: Aedeagal median lobe obtusely angulate at apicolateral corners, with apical sclerotized area subpentagonal (Fig. 83A); copulatory tube obtusely pointed at apex (Fig. 83C)..................................................................................................................S. acutatus Naomi
22(19) Male: Aedeagal median lobe with apical sclerotized area having a median longitudinal

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173

line in the apical 3/4 (Fig. 82B) ...............................................................S. rufescens Sharp
23(18) Male: Copulatory tube once or twice strongly curved or bent on its way.
24(27) Male: Copulatory tube once strongly curved or bent on its way.
25(26) Male: Aedeagal median lobe with apical sclerotized area elongate-subtriangular in shape,with a median longitudinal line in about apical 2/3 (Fig. 84C); endophallic expulsion
hook not protruding mesially (Fig. 84G) ..............................................S. ichikawai Naomi
26(25) Male: Aedeagal median lobe with apical sclerotized area triangular, without a medianlongitudinal line (Fig. 87G); endophallic expulsion hook mesially protruding at the middle of mesial part (Fig. 87G) ............................S. deltoides Naomi, Nomura & Kamezawa
27(24) Male: Copulatory tube twice strongly curved on its way (Fig. 89B) ....S. cygnipenis Puthz
28(17) Male: Copulatory tube with apical tube arising from the dorsal surface near or a little
proximal from the apex of basal tube
29(30) Male: Copulatory tube hardy constricted between basal chamber and main tube (Fig.
90C)...........................................................................................................S. agrestis Naomi
30(29) Male: Copulatory tube distinctly constricted between basal chamber and main tube.
31(32) Male Copulatory tube having basal tube baculiform, slightly thickening apicad (Fig.
91C); endophallic expulsion hook with posterior plate not tadpole-shaped (Fig. 91 F, G) ..
................................................................................................................S. olliformis Naomi
32(31) Male: Copulatory tube with basal tube fusiform (Fig. 92C); endophallic expulsion hookwith posterior plate tadpole-shaped (Fig. 92F) .............................................S. ebisu Naomi
33(2) Male: Endophallic expulsion hook dorsally with a thin, almost Y-shaped process. Female:
Spermatheca with basal duct extremely thick, and much broader than proximal part ofspermathecal duct.
34(35) Male: Aedeagal median lobe with apical sclerotized area subtriangular, very acutely
pointed at apex with a long apicomedian cusp (Fig. 79C); endophallic expulsion hookwith anterior plate about as broad as posterior plate (Fig. 79I) ................. S. amida Naomi
35(34) Male: Aedeagal median lobe with apical sclerotized area not subtriangular, pointed atapex with an extremely minute apicomedian cusp; endophallic expulsion hook with anterior plate diﬀerent in breadth from posterior plate.
36(37) Male: Aedeagal median lobe with apical sclerotized area much broader (Fig. 80A); endophallic expulsion hook with anterior plate narrower than posterior plate (Fig. 80A)...........
............................................................................................S. pediculifer Naomi & Nomura
37(36) Male: Aedeagal median lobe with apical sclerotized area much narrower (Fig. 81C);
endophallic expulsion hook with anterior plate broader than posterior plate (Fig. 81G) .....
................................................................S. yoshidaiellus Naomi, Nomura & Puthz sp. nov.
38(1) Male: Aedeagal median lobe with apical sclerotized area having a median longitudinalline completely or almost completely running from the base to apex; and also endophallic
expulsion hooks usually with anterior plates more or less diverging anteriad and posterior
plates more or less converging posteriad, and also almost always with anterior plate
demarcated by suture from posterior plate.
39(44) Male: Copulatory tube moderately or strongly twice curved or bent on its way.
40(41) Male: Endophallic expulsion hooks connected each other at mesial angulate corners a little behind the middle of posterior plates (Fig. 93D) ...........................S. wasabi Hromádka
41(40) Male: Endophallic expulsion hooks if connected each other, connected at mesial angulate
corners before the middle of posterior plates.
42(43) Male: Endophallic expulsion hooks connected each other at the mesial angulate corners a174

Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

little before the middle of posterior plates (Fig. 94I, J); each hook with posterior platenearly tetragonal and broader at base (Fig. 94I, J) ................... S. daigonis Naomi & Puthz
43(42) Male: Endophallic expulsion hooks if connected each other, connected at or near the basimesial corners of posterior plates (Fig. 95H–I); each hook with posterior plate elongatesubtriangular in shape and narrower at base (Fig. 95E–G) ........................S. ingens Naomi
44(39) Male: Copulatory tube not or very weakly curved on its way.
45(48) Male: Copulatory tube with main tube thinner, and not swollen at subapical part.
46(47) Male: Copulatory tube thinner (Fig. 96D); endophallic expulsion hook with anterior plateslightly curved mesially at anterior tip (Fig. 96H) ................................. S. lubomiri Naomi
47(46) Male: Copulatory tube thicker (Fig. 97E); endophallic expulsion hooks with anterior plate
not curved mesially at anterior tip (Fig. 97H)....................................... S. ichihashii Naomi
48(45) Male: Copulatory tube with main tube thicker, and more or less swollen at subapical part.
49(52) Male: Copulatory tube with a straight apicomedian process.
50(51) Male: Copulatory tube submembranous at subapical portion, with a shorter apicomedianprocess (Fig. 98C); endophallic expulsion hook with posterior plate moderately broad,and shorter than anterior plate (Fig. 98E) ............................................ S. mikawanis Naomi
51(50) Male: Copulatory tube solid at subapical portion, with a longer apicomedian process (Fig.
99C); endophallic expulsion hook with posterior plate slender, and longer than anterior
plate (Fig. 99H) ......................................................................................... S. gyrosus Naomi
52(49) Male: Copulatory tube with an almost or nearly beak-shaped process at apex.
53(54) Male: Seventh ventrite posteromedially modiﬁed with a shallower depression which ismore shallowly emarginate posteriorly (Fig. 100F); aedeagal median lobe with apicalsclerotized area elongate-subtriangular in shape (Fig. 100B) ............S. nakanei Hromádka
54(53) Male: Seventh ventrite posteromedially modiﬁed with a deeper depression which is moredeeply emarginate posteriorly (Fig. 101F); aedeagal median lobe with apical sclerotizedarea subpentagonal (Fig. 101B) ...............................................................S. awajinis Naomi
Stenus matobai Naomi(Fig. 74A–H)
Stenus matobai Naomi, 2012: 279; Naomi & Puthz, 2013: 143.
Type material examined. Holotype: ♂ (CMB), Kotonotaki, Susami City, Wakayama Pref., 20.
ii. 1997, I. Matoba leg. Paratypes: 1 ♀, same data as holotype; 1 ♂, same locality, 26. x. 1992, I.
Matoba leg.; 1 ♀, Hirai, Kozagawa-cho, Wakayama Pref., 30. iii. 1990, I. Matoba leg.; 1 ♀, same
locality, 16. vii. 1999, M. Maruyama leg.; 1 ♀, same locality, 14. vii. 1999, V. Puthz leg.
Distribution. Japan: Honshu (Wakayama Pref.).
Redescription. Male and female: Body 2.5–3.3 mm (fore body 1.6–1.9 mm) in length. Body
moderately shining; head black; pronotum, elytra and abdomen dark red to dark reddish brown;
labrum reddish brown to dark red; antennae and legs yellowish brown to reddish brown. Body
with punctures small to moderately large, round to elliptical, and also pronotum partially withcoarse punctures and elytra partially with large, coarse punctures. Head moderately concave,with a pair of longitudinal-oblique furrows or depressions; antennae short to moderately long,very thin; pronotum with surface slightly uneven, with a median longitudinal furrow indistinct todistinct; elytra with surface even to slightly uneven; abdomen subcylindrical, moderately thick tothick, slightly tapering posteriorly to subparallel-sided; lateroventrites and tergoventrites sutures

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175

Fig. 74. Stenus matobai Naomi (Wakayama: A–D, F, H, Kotonotaki, E, G, Hirai). A, 9th ventrite of male; B, 9th
and 10th terga of male; C, 6th to 8th ventrites of male; D, endophallic expulsion hooks; E, spermatheca; F,
aedeagus; G, gonocoxite; H, copulatory tube. Scale 1: 0.2 mm for A, B, F, 0.1 mm for D, E, G, H; scale 2:0.25 mm for C.

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Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

lost.
Male: Abdomen (Fig. 74C) modiﬁed with a very shallow depression on the 7th, and a shallow, arcuate emargination on the 8th ventrite; 9th tergum (Fig. 74B) with ventral apophyses moderately long; 9th ventrite (Fig. 74A) with apicolateral teeth short, very acute, apicolateral setae
short; 10th tergum (Fig. 74B) very shallowly emarginate posteromedially. Aedeagus (Fig. 74F)
with median lobe slender, thin, well-rounded at apicolateral corners, almost rounded apically;
apical sclerotized area almost crescent, basimedially with a broad, subtriangular emargination.
Endophallus (Fig. 74F) with copulatory tube (Fig. 74H) with basal chamber ovoidal, main tube
moderately long, attenuate; expulsion hooks (Fig. 74D) thin, each with anterior plate acutely
pointed at anterior tip; ventromedian bands moderately long, very thin. Parameres (Fig. 74F)
long, each weakly incurved and very acutely pointed at apex, with pedicel very thin, moderately
curved mesially; apical area very long, mesially with 9 to 10 setae of various length.
Female: Eighth ventrite obtuse posteromedially; gonocoxites (Fig. 74G) each with apicolateral setae very long, very acute, apicolateral setae very long. Spermatheca (Fig. 74E) with capsule small; striped duct moderately long, very thick; duct very long, thin, tightly coiled; basal
valve short; basal duct sclerotized, weakly twisted before the middle.
Biology and ecology. The beetles of S. kagura inhabit leaf litter heaped in the natural forestsof lowlands to low mountainous regions.
Remarks. S. matobai are allied to S. kagura, but it is separable from the latter species by theelytra darker in coloration (dark red to dark reddish brown), the aedeagal median lobe broader at
the apical part, with its apical sclerotized area almost rounded apically (Fig. 74F), the endophallic expulsion hook with its posterior plate protruding posterolaterally at the posterolateral corner(Fig. 74D), and the spermatheca with its duct thinner (Fig. 74E).
Etymology. This species is named after Mr. Isao Matoba (Wakayama) who collected theStenus-beetles designated as the type specimens.
Stenus kagura Naomi & Puthz(Figs. 75A–I, 134A)
Stenus kagura Naomi & Puthz, 1993: 308; Herman, 2001: 2243; Naomi & Puthz, 2013: 143.
Type material examined. Holotype: 1 ♂ (SMNHS), Mituishi, Okayama Pref., 21. v. 1973, K.
Sawada leg. Paratypes: 2 ♀ (cP), same data as holotype.
Other material examined. [HONSHU]: 5 ♂4 ♀, Mt. Kuma, Bizen City, Okayama Pref., 9. xi.
1988, S. Nomura leg.
Distribution. Japan: Honshu (Okayama Pref.).
Redescription. Male and female: Body 3.2–3.6 mm (fore body 1.4–1.6 mm) in length. Body
weakly or moderately shining; head black, with median area dark red near black to almost black;pronotum and elytra reddish brown to dark reddish brown; abdomen dark reddish brown to darkbrown; labrum reddish brown; antennae and legs yellowish brown to reddish brown. Body with
punctures small to moderately large, round to ovoidal, and also pronotum and elytra partiallycoarse punctures. Head moderately concave, with a pair of longitudinal-oblique furrows or
depressions; antennae short to moderately long, very thin; pronotum with surface slightly
uneven, with a median longitudinal furrow very indistinct or indistinct; elytra with surface
slightly uneven to uneven; abdomen subcylindrical, moderately thick to thick, slightly tapering
posteriorly to subparallel-sided; lateroventrites and tergoventrites sutures lost.

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177

Fig. 75. Stenus kagura Naomi & Puthz (Okamaya: A, C–I, Mitsuishi; B, Bezen). A, 6th and 7th ventrites; B, 9th
and 10th terga of male; C, 9th ventrite of male; D, posterior part of 8th ventrite of male; E, endophallic expulsion hooks; F, spermatheca; G, aedeagus; H, copulatory tube and ventromedian bands; I, gonocoxite. Scale 1:0.25 mm for A; scale 2: 0.1 mm for B, G; scale 3: 0.2 mm for C, 0.1 mm for E, F, H, I; scale 4: 0.25 mm for D.

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Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

Male: Abdomen (Fig. 75A) modiﬁed with a ﬂat area on the 7th, and a shallow, broad emargination on the 8th ventrite (Fig. 75D); 9th tergum (Fig. 75B) with ventral apophyses long; 9th
ventrite (Fig. 75C) with macrosetae short, apicolateral teeth very short, acute, apicolateral setae
short; 10th tergum (Fig. 75B) very shallowly emarginate posteromedially. Aedeagus (Fig. 75G)
with median lobe slender, almost pointed at apex; apical sclerotized area almost triangular, basimedially with an arcuate emargination. Endophallus (Fig. 75G) with copulatory tube (Fig. 75H)
long, with basal chamber large, ovoidal, main tube attenuate; expulsion hooks (Fig. 75E) eachthin, with anterior plate pointed at anterior tip, posterior plate strongly curved laterally, pointed atapex; ventromedian bands (Fig. 75G, H) long, thin. Parameres (Fig. 75G) slender, each pointed
at apex; apical area long, slightly swollen mesially at base, mesially also with 8 setae.
Female: Eighth ventrite obtuse or pointed posteromedially; gonocoxites (Fig. 75I) each withapicolateral teeth long, acute, apicolateral setae moderately long. Spermatheca (Fig. 75F) with
capsule well-rounded apically; striped duct long, moderately thick to thick; duct long, moderately thick, tightly coiled; basal duct sclerotized, long.
Biology and ecology. The beetles of S. kagura inhabit leaf litter heaped in the natural forestsof low mountainous regions.
Remarks. S. kagura is allied to S. matobai, but it is separable from the latter species by theelytra paler in coloration (reddish brown to dark reddish brown), the aedeagal median lobe narrower at the apical part, with its apical sclerotized area almost triangular (Fig. 75G), the endophallic expulsion hook with its posterior plate strongly curved laterally (Fig. 75E), and the spermatheca with its duct thicker (Fig. 75F).
Etymology. The speciﬁc epithet of this species is derived from the name of a sacred Shintoistic dance accompanied with the music originated in the ancient period of Japan, Kagura.
Stenus toshiharui Naomi(Figs. 76A–G, 134B)
Stenus toshiharui Naomi, 1990: 46; Herman, 2001: 2419; Naomi & Puthz, 2013: 143.
Type material examined. Holotype: ♂ (KUF), Tsubakiyama, Saga Pref., 2. x. 1977, H. Ohishi
leg. Paratypes: 5 ♂3 ♀, same data as holotype; 2 ♂1 ♀, Ikenohara Marsh, Saga Pref., 9. ix. 1976,
H. Ohishi leg.; 1 ♂, Mt. Mifune, Takeo City, Saga Pref., 27. v. 1984, S. Nomura leg.
Other material examined. [KYUSHU]: 3 ♂1 ♀, Oonohara, Higashisonogi, Nagasaki Pref., 1.
xii. 2002, M. Nishida leg.; 2 ♂2 ♀, Mt. Kuradake, Kumamoto Pref., 7. v. 1987, S. Nomura leg.
Distribution. Japan: Kyushu (Saga, Nagasaki and Kumamoto Prefs.).
Redescription. Male and female: Body 2.6–3.7 mm (fore body 1.4–1.8 mm) in length. Body
moderately shining; head almost black to black, with lateral parts of interocular area reddish
brown to dark red; pronotum and elytra reddish brown; abdomen reddish brown to dark brown oralmost black, sometimes with apical segments more or less infuscate; labrum reddish orange to
reddish brown; antennae and legs yellowish brown to reddish brown. Body with punctures roundto ovoidal, small to moderately large, and also pronotum partially with coarse to subrugose punctures and elytra partially with large, subrugose punctures. Head moderately concave, with a pairof longitudinal-oblique furrows; antennae moderately long, very thin; pronotum with surface
slightly uneven, with a median longitudinal furrow very indistinct; elytra with surface uneven;abdomen subcylindrical, slightly tapering posteriorly to subparallel-sided; lateroventrites and tergoventral sutures lost.

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179

Fig. 76. Stenus toshiharui Naomi (Saga: A, B, Ikenohara Marsh, C–G, Mt. Tsubaki). A, 9th ventrite of male; B,
9th and 10th terga of male; C, aedeagus; D, spermatheca; E, endophallic expulsion hooks; F, posterior part of
8th ventrite of male; G, copulatory tube. Scale 1: 0.1 mm for A, C; scale 2: 0.2 mm for B, 0.1 mm for D, G,
0.05 mm for E; scale 3: 0.2 mm for F.

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Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

Male: Abdomen modiﬁed with a very shallow depression on the 7th, and an arcuate, broad,shallow emargination on the 8th ventrite (Fig. 76F); 9th tergum (Fig. 76B) with ventral apophyses moderately long; 9th ventrite (Fig. 76A) with macrosetae very long, apicolateral teeth long,very acute, apicolateral setae very long; 10th tergum (Fig. 76B) very shallowly emarginate posteriorly. Aedeagus (Fig. 76C) with median lobe elongate, well-rounded at apicolateral corners,
acutely pointed at apex with a moderately long apicomedian cusp; apical sclerotized area hardly
developed. Endophallus (Fig. 76C) with copulatory tube (Fig. 76G) with main tube baculiform,
slightly attenuate; expulsion hooks (Fig. 76E) elongate, each with anterior plate almost pointed,
antero-posteriorly divided into 2 subplates; ventromedian bands moderately long, narrow. Parameres (Fig. 76C) very long, each pointed at apex; apical area very long, mesially with 19 to 25
setae of various length.
Female: Eighth ventrite obtuse posteromedially; gonocoxites each with apicolateral toothlong, very acute, apicolateral setae very long. Spermatheca (Fig. 76D) with capsule small; striped
duct moderately long, thick; duct short, moderately thick, loosely coiled; basal valve very short;basal duct short; basal pouch broad-conical in shape.
Biology and ecology. The beetles of S. toshiharui inhabit leaf litter heaped in the natural forests of low mountainous to mountainous regions.
Remarks. S. toshiharui is probably allied to S. akome, but it is separable from the latter species by the abdominal modiﬁcations of male less developed (Fig. 76F), the aedeagal median lobe
broader, with its apical sclerotized area shorter (Fig. 76C), the endophallic expulsion hook with
its apical plate divided into 2 subplates (Fig. 76E), and the paramere with its apical area thinner(Fig. 76C).
Etymology. This species is named after the late Dr. Toshiharu Yoshida (Okayama University)
who studied the population ecology of stored grain insect pests.
Stenus akome Naomi(Figs. 77A–H, 134C)
Stenus akome Naomi, 1989: 166; Herman, 2001: 2049; Naomi & Puthz, 2013: 143.
Type material examined. Holotype: ♂ (KUM), Mt. Hiko, Fukuoka Pref., 4. ix. 1977, H. Ohishi leg. Paratypes: 2 ♂5 ♀, same data as holotype; 1 ♂1 ♀, Shin-yabakei, Ohita Pref., 30. iii.
1985, S. Nomura leg.; 1 ♀, Makinoto Pass, Ohita Pref., 10. viii. 1979, S. Naomi leg.; 1 ♀, Kikuchi Valley, Kumamoto Pref., 11. iv. 1981, S. Naomi leg.; 1 ♂, Mt. Hakucho, Gokanosho, Kumamoto Pref., 27. v. 1978, T. Ogata leg.
Other material examined. [HONSHU]: 1 ♂, Tengehata, Yamaguchi Pref., 1. iv. 1995, T.
Watanabe leg.; 1 ♂1 ♀, Chomonkyo, Yamaguchi Pref., 25. iv. 1988, S. Nomura leg. [KYUSHU]:
1 ♀, Mt. Fukuchi, Kitakyushu City, Fukuoka Pref., 3. xi. 1997, H. Hoshina leg.; 3 ♂, Hirotani,
Hiraodai, Fukuoka Pref., 25. iv. 1989, S. Nomura leg.; 4 ♂4 ♀, Mt. Sobo, Ohita Pref., 17. v.
1986, S. Nomura leg.; 2 ♂, Kamino, Takachiho, Miyazaki Pref., 17. iv. 2014, T. Watanabe leg.;1 ♂, Mt. Ohkue, Kitagawa-cho, Miyazaki Pref., 5. vi. 1994, T. Kinoda leg.; 3 ♂3 ♀, Mt. Hoyoshi,
Kôyama-machi, Kagoshima Pref., 19. iii. 1994, S. Nomura leg.
Distribution. Japan: Honshu (Yamaguchi Pref.) and Kyushu.
Redescription. Male and female: Body 3.0–4.0 mm (fore body 1.6–2.1 mm) in length. Body
moderately shining; head dark red to almost black, with clypeofrontal or median area reddish
brown; pronotum and elytra reddish brown; abdomen dark red to almost black; labrum reddish

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Fig. 77. Stenus akome Naomi (Yamaguchi and Kyushu). A, 9th ventrite of male; B, 9th and 10th terga of male; C,
5th to 8th ventrites of male; D, spermatheca; E, endophallic expulsion hooks; F, aedeagus; G, copulatory tube;
H, posterior part of gonocoxite. Scale 1: 0.2 mm for A, B, 0.1 mm for D, G, H; scale 2: 0.3 mm for C; scale 3:0.05 mm for E, 0.1 mm for F.

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brown; antennae and legs clear yellowish brown to reddish brown. Body with punctures round to
ovoidal, small to moderately large, and also pronotum partially with coarse to subrugose punctures and elytra partially with large, coarse to subrugose punctures. Head shallowly to moderately concave, with a pair of longitudinal-oblique furrows or depressions; antennae short to moderately long, very thin; pronotum with surface slightly uneven to uneven, with a medianlongitudinal furrow indistinct; elytra with surface slightly uneven to uneven; abdomen subcylindrical, slightly tapering posteriorly; lateroventrites and tergoventrite sutures lost.
Male: Abdomen (Fig. 77C) modiﬁed with a broad, semicircular ﬂat area on the 5th, a large,
semicircular, slightly shallow (Fig. 77C) or moderately deep depression on the 6th, a very large,
moderately deep or deep, posteromedian depression (which is continuous with a small anteromedian depression) on the 7th, and an arcuate emargination on the 8th ventrite; 9th tergum (Fig.
77B) with ventral apophyses relatively short; 9th ventrite (Fig. 77A) with macrosetae relatively
short, apicolateral teeth short, acute, apicolateral setae long; 10th tergum (Fig. 77B) rounded posteriorly. Aedeagus (Fig. 77F) with median lobe slender, pointed or acutely pointed at apex; apicalsclerotized area subtriangular, with (Fig. 77F) or without an apicomedian cusp. Endophallus(Fig. 77F) with copulatory tube (Fig. 77G) relatively short (Fig. 77F) or moderately long, withbasal chamber almost bulbous, main tube thick at base, attenuate, almost straight (Fig. 77G) or
weakly curved at apical part; dorsolateral bands thin; expulsion hooks (Fig. 77E) moderately
large, elongate, each with anterior plate minutely incurved at anteromesial corner, posterior plate
posterolaterally well-rounded, covered with very minute tubercles; ventromedian bands moderately long, relatively thin. Parameres (Fig. 77F) each almost pointed at apex; apical area long tovery long, more or less broad dorsoventrally, moderately swollen laterally at base, mesially with
7 to 11 setae of various length.
Female: Eighth ventrite obtuse or pointed posteromedially; gonocoxites (Fig. 77H) with apicolateral tooth moderately long, very acute, apicolateral setae very long. Spermatheca (Fig. 77D)
with capsule moderately large; striped duct short, thick; duct relatively short with 5 to 8 (Fig.
77D) turns, thin to thick; basal valve short; basal duct well-sclerotized, thick.
Biology and ecology. The beetles of S. akome inhabit leaf litter heaped in the natural forestsof low mountainous to mountainous regions.
Remarks. S. akome is allied to S. toshiharui, but it is separable from the latter species by theabdominal modiﬁcations of male more developed (Fig. 77C), the aedeagal median lobe narrower,with its apical sclerotized area longer (Fig. 77F), the endophallic expulsion hook with its apicalplate solid (Fig. 77E), and the paramere with its apical area thicker (Fig. 77C). It is characteristic
in S. akome that the depressions on the 6th and 7th ventrites of male are very diﬀerent in depth
and size from one beetle to another, as described in Naomi (2012, p. 295, Fig. 10A, D, H).
Etymology. The speciﬁc epithet of this species is derived from the Japanese term whichmeans a kind of folding fan of early modern times in Japan, akome-ougi.
Stenus incumbens Naomi & Y. Watanabe(Fig. 78A–G)
Stenus incumbens Naomi & Watanabe, 2015: 106.
Type material examined. Holotype: ♂ (TUAA), Mt. Yokoo, Oki Is., Shimane Pref., 28. ix.
1969, Y. Watanabe leg. Paratype: 1 ♂, same data as holotype.
Other material examined. [HONSHU]: 1 ♀, Mt. Daimanji (450 m), Fuse Vil., Dogo Is., Oki

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Fig. 78. Stenus incumbens Naomi & Watanabe (Shimane: Oki Isls.). A, apical 2/3 of aedeagus; B, copulatorytube; C, 9th and 10th terga of male; D, aedeagus; E, 9th ventrite of male; F, posterior part of 8th ventrite ofmale; G, endophallic expulsion hooks. Scale 1: 0.2 mm for C–E, 0.1 mm for A, B, G; scale 2: 0.2 mm for F.

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Isls., Shimane Pref., 16. ix. 2003, T. Shimada leg.
Distribution. Japan: Honshu (Shimane Pref.: Dogo Is.).
Redescription. Male: Body 3.0–3.4 mm (fore body 1.4–1.6 mm) in length. Body weakly shining; head dark red to black; pronotum and elytra reddish brown; abdomen dark red to dark reddish brown; labrum, antennae and legs yellowish brown to reddish brown. Body with puncturesround to ovoidal, small to moderately large, and also pronotum partially with subrugose punctures and elytra partially with large, subrugose punctures. Head moderately concave, with a pairof longitudinal-oblique furrows; antennae short, very thin; pronotum with surface slightly unevento uneven, with a median longitudinal furrow indistinct or almost distinct; elytra with surface
uneven; abdomen subcylindrical, subparallel-sided; lateroventrites and tergoventral sutures lost.
Abdomen modiﬁed with a slightly elongate, shallow or moderately deep depression on the
7th, and a moderately deep emargination on the 8th ventrite (Fig. 78F); 9th tergum (Fig. 78C)
with ventral apophyses long; 9th ventrite (Fig. 78E) with apicolateral teeth short, acute, apicolateral setae short; 10th tergum (Fig. 78C) almost rounded posteriorly. Aedeagus (Fig. 78A, D) withmedian lobe slender, rounded at apicolateral corners, very acutely pointed at apex; apical sclerotized area narrow, almost triangular, covered with thin, parallel, longitudinal lines. Endophallus(Fig. 78D) with copulatory tube (Fig. 78B) very long, main tube with basal tube thick to very
thick, apical tube attenuate, extremely aciculate at apex; dorsolateral bands thin; expulsion hooks
H-shaped (Fig. 78D) or M-shaped (Fig. 78G), each weakly protruded anteromesially at the middle of mesial side, with a longitudinal line along the middle of posterior portion; ventromedianbands moderately long, moderately broad. Parameres (Fig. 78A, D) each very acutely pointed atapex; apical area long, slightly swollen mesially at base, mesially also with 10 to 11 setae.
Female: Eighth ventrite almost acute posteromedially; gonocoxites each with apicolateral
teeth long, acute, apicolateral setae very long. Spermatheca with capsule moderately large,slightly narrowed apically, connected with spermathecal duct only by one short, transverse,
membranous ring due to the absence of distinct striped duct; duct moderately long, distally witha long, thick tube; basal duct very large, very thick; basal pouch elongate-conical in shape, membranous.
Biology and ecology. S. incumbens is insular and may be endemic to Oki Islands oﬀ Shimane
Pref. The beetles of this species inhabit leaf litter heaped in the natural forests of low mountainous regions.
Remarks. S. incumbens is allied to S. toshiharui and S. akome, but it is separable from the latter 2 species by the aedeagal median lobe with its apical sclerotized area covered with thin, parallel, longitudinal lines (Fig. 78A), the copulatory tube with its basal tube much thicker (Fig.
78B), the paramere with its apical area mesially with longer setae (Fig. 78D), and the spermatheca with its basal duct thicker.
Stenus amida Naomi(Figs. 79A–I, 134D)
Stenus amida Naomi, 1989: 164; Herman, 2001: 2053; Naomi & Puthz, 2013: 145.
Type material examined. Holotype: ♂ (KUF), Mt. Tsurugi, Tokushima Pref., 15–17. x. 1980,
S. Naomi leg. Paratypes: 1 ♂5 ♀, same data as holotype; 2 ♂, same locality, 19–20. vi. 1981, S.
Naomi leg.
Other material examined. [HONSHU]: 5 ♂1 ♀, Mt. Tsurugi, Tokushima Pref., 27. ix. 1999,

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Fig. 79. Stenus amida Naomi (Tokushima: Mt. Tsurugi). A, 9th ventrite of male; B, 9th and 10th terga of male; C,aedeagus; D, 6th and 7th ventrites of male; E, copulatory tube; F, posterior part of gonocoxite; G, posterior
part of 8th ventrite of male; H, spermatheca; I, endophallic expulsion hooks. Scale 1: 0.2 mm for A, C, 0.1 mm
for E, F, H, I; scale 2: 0.25 mm for D; scale 3: 0.25 mm for G; scale 4: 0.2 mm for B.

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S. Nomura leg.; 1 ♂1 ♀, same locality, 13. viii. 1995, H. Hoshina leg.; 1 ♂, Nishijima Shrine, Mt.
Tsurugi (1800 m), 11. vii. 1993, M. Sakai leg.
Distribution. Japan: Shikoku (Tokushima Pref.).
Redescription. Male and female: Body 3.3–3.6 mm (fore body 1.6–1.8 mm) in length. Body
moderately shining; head black, with clypeofrontal or median area reddish brown to dark red;pronotum and elytra reddish orange to reddish brown; abdomen dark red to dark reddish brown;
labrum reddish orange; antennae and legs yellowish brown to reddish brown. Body with punctures round to ovoidal, small to moderately large, and also pronotum and elytra partially with
subrugose punctures. Head moderately concave, with a pair of longitudinal-oblique or mesiallycurved furrows (or depressions); antennae short to moderately long, very thin; pronotum withsurface uneven, with a median longitudinal furrow indistinct or almost distinct; elytra with surface uneven; abdomen subcylindrical, subparallel-sided; lateroventrites and tergoventral sutures
lost.
Male: Abdomen (Fig. 79D) modiﬁed sometimes with a ﬂat area on the 5th, and always with a
ﬂat area or a shallow depression on the 6th, an elongate, moderately deep depression on the 7th,
and a relatively small emargination on the 8th ventrite (Fig. 79G); 9th tergum (Fig. 79B) withventral apophyses very long; 9th ventrite (Fig. 79A) with macrosetae short to moderately long,apicolateral teeth moderately long, very acute, apicolateral setae moderately long; 10th tergum(Fig. 79B) very shallowly emarginate posteromedially. Aedeagus (Fig. 79C) with median lobe
narrowing posteriad behind the middle, obtusely angulate at apicolateral corners, very acutely
pointed at apex with a long apicomedian cusp; apical sclerotized area subtriangular. Endophallus(Fig. 79C) with copulatory tube (Fig. 79E) having basal chamber comprising a pair of thin rods,
main tube slightly small, beak-shaped at apex, dorsally with a very thin, almost Y-shaped process; dorsolateral bands very thin; expulsion hooks (Fig. 79I) elongate, each laterally with two
arcuate, shallow emarginations, with anterior plate about as broad as posterior plate; ventromedian bands long, moderately broad. Parameres (Fig. 79C) moderately thick, each obliquely truncate apically; apical area very long, mesially with 4 short setae at base and 2 shorter setae near
apex.
Female: Eighth ventrite almost rounded posteriorly; gonocoxites (Fig. 79F) each with apicolateral tooth long, very acute, apicolateral setae long. Spermatheca (Fig. 79H) with capsule elongate, rounded apically; striped duct moderately long, thick; duct short, moderately thick, with 2
distinct turns; basal duct very large, subovoidal, strongly sclerotized.
Biology and ecology. The beetles of S. amida inhabit leaf litter heaped in the natural forestsof a mountainous region. At present this species is known only from Mt. Tsurugi, Tokushima
Pref., although it seems to be common from there when judging from the collecting records ofthis species enumerated in the specimens examined.
Remarks. S. amida is allied to S. pediculifer, but it is separable from the latter species by theaedeagal median lobe narrower in the posterior 1/2, with its apical sclerorized area elongate-subtriangular in shape and very acutely pointed with a long apicomedian cusp; (Fig. 79C), and theendophallic expulsion hook laterally with two arcuate emarginations (Fig. 79I).
Three species S. amida, S. pediculifer and S. yoshidaiellus, all of which are at present known
only from the mountainous regions of eastern Shikoku, seem to form a closely allied group on
account of their common possession of the following peculiar conditions: Aedeagal median lobe
with an apicomedian cusp, the endophallic expulsion hook with its main tube having a Y-shaped
process, the paramere with its apical area becoming more or less thicker apicad, and the spermatheca with its basal tube extremely large and strongly sclerotized.

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Etymology. The speciﬁc epithet of this species is derived from a traditionally recognized titleof Buddha, Amida.
Stenus pediculifer Naomi & Nomura(Fig. 80A–F)
Stenus pediculifer Naomi & Nomura, 2015: 194.
Type material examined. Holotype: ♂ (NMNST), Mt. Takashiro, Koyadaira Vil., Tokushima
Pref., 27. ix. 1999. Paratypes: 1 ♂2 ♀ & 1 ♀ (NMNST), same data as holotype.
Distribution. Japan: Shikoku (Tokushima Pref.).
Redescription. Male and female: Body 3.1–3.8 mm (fore body 1.5–1.8 mm) in length. Body
moderately shining; head black, with clypeofrontal or median area reddish brown to dark red;pronotum and elytra yellowish or reddish brown to dark red; abdomen dark reddish brown;
labrum reddish orange; antennae and legs yellowish brown to reddish brown. Body with punctures round to elliptical, small to moderately large, and also pronotum partially with subrugose
punctures and elytra partially with large, subrugose punctures. Head moderately concave, with apair of longitudinal-oblique or mesially- curved furrows; antennae short to moderately long, very
thin; pronotum with surface uneven, with a median longitudinal furrow indistinct or almost distinct; elytra with surface uneven; abdomen subcylindrical, subparallel-sided; lateroventrites andtergoventral sutures lost.
Male: Abdomen modiﬁed with a ﬂat area on the 6th, an elongate, very shallow depression on
the 7th, and a narrow, shallow emargination on the 8th ventrite (Fig. 80D); 9th tergum (Fig. 80C)
with ventral apophyses long; 9th ventrite (Fig. 80B) with macrosetae very long, apicolateral teeth
long, thin, very acute, apicolateral setae very long; 10th tergum (Fig. 80C) entire. Aedeagus (Fig.
80A) with median lobe obtusely angulate at apicolateral corners, pointed at apex with anextremely minute apicomedian cusp; apical sclerotized area transverse, very short. Endophallus(Fig. 80A) with copulatory tube having basal chamber small, main tube comprising 2 thin rods atbase and a U-shaped structure at apex, dorsally with a very thin, Y-shaped process; dorsolateralbands very thin; explusion hooks each boot-shaped, laterally with arcuate emargination; ventromedian bands very long, very broad, each covered with very small dots only on mesial side.
Parameres (Fig. 80A) very long, each acicular at apex; apical area extremely long, thick, mesially with 6 setae.
Female: Eighth ventrite almost rounded posteriorly; gonocoxites (Fig. 80F) each with apicolateral tooth long, acute, apicolateral setae moderately long. Spermatheca (Fig. 80E) with capsulesmall, rounded apically; striped duct slightly short, moderately broad; duct short, moderately
thick, with 5 turns; basal valve extremely short; basal duct extremely large, strongly sclerotized.
Biology and ecology. The beetles of S. pediculifer inhabit leaf litter heaped in the natural forests of a mountainous region.
Remarks. S. pediculifer is allied to S. amida, but it is separable from the latter species by theaedeagal median lobe broader in the posterior 1/2, with its apical sclerorized area transverse andpointed with a minute apicomedian cusp (Fig. 80A), and the endophallic expulsion hook laterallywith an arcuate emargination (Fig. 80A).

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Fig. 80. Stenus pediculifer Naomi & Nomura (Tokushima: Mt. Takashiro). A, aedeagus; B, 9th ventrite of male;C, 9th and 10th terga of male; D, 8th ventrite of male; E, spermatheca; F, posterior part of gonocoxite. Scale 1:
0.1 mm for A, B; scale 2: 0.2 mm for C, D, 0.1 mm for E, F.

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Fig. 81. Stenus yoshidaiellus Naomi, Nomura & Puthz sp. nov. (Tokushima: Mt. Takashiro). A, 9th and 10th tergaof male; B, posterior part of gonocoxite; C, aedeagus; D, spermatheca; E, 9th ventrite of male; F, 7th and 8th
ventrites of male; G, endophallic expulsion hooks. Scale 1: 0.2 mm for A, C, E, 0.1 mm for B, D, 0.05 mm for
G; scale 2: 0.3 mm for F.

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Stenus yoshidaiellus Naomi, Nomura & Puthz sp. nov.
(Fig. 81A–G)
Type material examined. Holotype: ♂ (KUMF), Mt. Takashiro, Koyadaira Vil., Tokushima
Pref., 17–18. vii. 2010, T. Ito leg. Paratypes: 2 ♂2 ♀ (KUMF), same data as holotype.
Distribution. Japan: Shikoku (Tokushima Pref.).
Description. Male and female: Body 3.2–3.5 mm (fore body 1.5–1.7 mm) in length. Body
weakly shining; head black, with clypeofrontal area reddish brown to dark red; pronotum andelytra reddish orange to reddish brown; abdomen dark reddish brown; labrum reddish orange;
antennae and legs yellowish brown to reddish brown. Body with punctures round to ovoidal,
small to moderately large, and also pronotum partially with subrugose punctures and elytra partially with large, subrugose punctures. Head moderately concave, with a pair of longitudinaloblique or mesially-curved furrows; antennae moderately long, very thin; pronotum with surface
uneven, with a median longitudinal furrow indistinct or almost distinct; elytra with surface
uneven to strongly uneven; abdomen subcylindrical, subparallel-sided; lateroventrites and tergoventral sutures lost.
Male: Abdomen (Fig. 81F) modiﬁed with a ﬂat area or a very shallow depression on the 6th,
a deep depression on the 7th, and a narrow, slightly deep emargination on the 8th ventrite; 9th
tergum (Fig. 81A) with ventral apophyses very long; 9th ventrite (Fig. 81E) with macrosetaevery short, apicolateral teeth short, very acute, apicolateral setae moderately long; 10th tergum(Fig. 81A) shallowly emarginate posteromedially. Aedeagus (Fig. 81C) with median lobe bulbous at base, strongly narrowing apicad in the posterior 2/5, pointed at apex with an extremely
minute apicomedian cusp; apical sclerotized area extremely narrow, very short. Endophallus(Fig. 81A) with copulatory tube having basal chamber large ovoidal, main tube comprising 2 thinrods at base, dorsally with a very thin, narrow, Y-shaped process; explusion hooks (Fig. 81G)
each with anterior plate subtriangular, broader than posterior plate; ventromedian bands moderately long, very narrow. Parameres (Fig. 81C) each minutely pointed at apicolateral corner, withpedicel thin; apical area long, becoming thicker apicad, mesially with 7 short setae.
Female: Eighth ventrite almost rounded posteriorly; gonocoxites (Fig. 81F) each with apicolateral tooth very long, acute, apicolateral setae very long. Spermatheca (Fig. 81E) with capsulevery small; striped duct long, moderately broad; duct short, thin to moderately thick, with 3 ormore distinct turns, and its proximal part of duct slightly sunk into the distal hollow of large
basal duct; basal duct extremely large, strongly sclerotized.
Biology and ecology. The beetles of S. yoshidaiellus inhabit leaf litter heaped in the naturalforests of a mountainous region.
Remarks. S. yoshidaiellus is allied to S. amida and S. pediculifer, but it is separable from thelatter 2 species by the aedeagal median lobe with its apical part more strongly narrowing apicad
and its apical sclerorized area smaller and narrower (Fig. 81C), the endophallic expulsion hookwith its posterior plate narrower (Fig. 81G), and the paramere thinner (Fig. 81C).
Etymology. This new species is named after Mr. Masataka Yoshida (Tokushima) who collected the Stenus-beetles designated as the type specimens.
Stenus rufescens Sharp（Figs. 82A–J, 134E)
Stenus rufescens Sharp, 1874: 88; Herman, 2001: 2372; Naomi & Puthz, 2013: 145.

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Fig. 82. Stenus rufescens Sharp (Hyogo: Mt. Maya). A, 9th ventrite of male; B, aedeagus; C, spermatheca; D,
gonocoxite; E, 8th ventrite of male; F, 9th and 10th terga of male; G, copulatory tube; H, copulatory tube
gland?; I, 6th and 7th ventrites of male; J, endophallic expulsion hooks. Scale 1: 0.2 mm for A, B, F, 0.1 mm
for C, D, G, J, 0.05 mm for H; scale 2: 0.25 mm for E; scale 3: 0.25 mm for I.

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Type material examined. Syntypes: 1 ♂1 ♀ (NHML), Maiyasama.
Other material examined. [HONSHU]: 5 ♂6 ♀, Mt. Maya, Kobe, Hyogo Pref., 12. v. 1997,
H. Hoshina leg.; 6 ♂8 ♀, same locality, 19. vii. 2001, H. Hoshina leg.;1 ♂1 ♀, same locality, 5. v.
1993, T. Kishimoto leg.; 1 ♀, same locality, 11. iii. 1941, K. Taniguchi leg.; 2 ♂1 ♀, same locality, 4. xi. 1983, T. Ito leg.
Distribution. Japan: Honshu (Hyogo Pref.).
Redescription. Male and female: Body 3.2–3.6 mm (fore body 1.6–1.8 mm) in length. Body
moderately shining and entirely yellowish brown to reddish brown, but lateral parts of interocular area and apical segments of abdomen more or less infuscate; labrum reddish orange to dark
red; antennae and legs yellowish brown to reddish brown. Body with punctures round to elliptical, small to moderately large, and also pronotum partially with subrugose punctures and elytra
partially with large, coarse to subrugose punctures. Head moderately concave, with a pair of longitudinal-oblique or mesially-curved furrows; antennae moderately long, very thin; pronotumwith surface uneven, with a median longitudinal furrow very indistinct to indistinct; elytra withsurface slightly uneven to uneven; abdomen subcylindrical, slightly tapering posteriorly; lateroventrites and tergoventral sutures lost.
Male: Abdomen (Fig. 82I) modiﬁed with a ﬂat area on the 5th, a shallow depression on the
6th, a moderately deep depression on the 7th, and an arcuate, broad, moderately deep emargination on the 8th ventrite (Fig. 82E); 9th tergum (Fig. 82F) with ventral apophyses long; 9th ventrite (Fig. 82A) with apicolateral teeth short, acute, apicolateral setae short; 10th tergum (Fig.
82F) shallowly, distinctly emarginate posteromedially. Aedeagus (Fig. 82B) with median lobe
elongate, narrowing apicad in about apical 3/5, almost pointed at apex; apical sclerotized area
elongate-trianguler in shape, with a median longitudinal line in the apical 3/4. Endophallus (Fig.
B) with copulatory tube (Fig. 82G) baculiform, thick, laterally with a small glandular apparatus?
(Fig. 82H); explusion hooks (Fig. 82J) almost X-shaped, each rounded and also narrowly membranous at anterior tip, posterolaterally with an almost arcuate emargination; dorsolateral bands
thin; ventromedian bands very long, narrow. Parameres (Fig. 82B) moderately thick, eachacutely pointed at apex; apical area moderately long, moderately swollen mesially at base, mesially also with 11 to 13 setae.
Female: Eighth ventrite obtuse posteromedially; gonocoxites (Fig. 82D) each with apicolateral tooth very long, very acute, apicolateral setae slightly short. Spermatheca (Fig. 82C) with
capsule narrowing apicad, narrowly rounded apically; striped duct short, thick, with indistinct,
transverse stripes; duct thin at base, mostly moderately thick to thick, regularly coiled 3 times;
gland almost ovoidal, with opening located on the lateral side of the duct a little proximal fromthe base of striped duct; basal valve short; basal pouch subconical.
Biology and ecology. The beetles of S. rufescens inhabit leaf litter heaped in the natural forests of a low mountainous region. Recently, this species is known only from Mt. Maya, Hyogo
Pref., although it seems to be common from there when judging from the collecting records ofthis species enumerated in the specimens examined.
Remarks. S. rufescens is allied to S. acutatus, but it is separable from the latter species by theaedeagal median lobe with its apical sclerotized area elongate-triangular in shape (Fig. 82B), thecopulatory tube thicker at the apical part (Fig. 82G), the endophallic expulsion hook with its
anterior plate rounded at the anterior tip (Fig. J), and the spermatheca with its duct regularly
coiled (Fig. 82C).
In every species of the cephalotes-group, the females have each a more or less chitinized
spermatheca, but in the female of S. rufescens, the spermathecal tube is more membranous (Fig.

The Steninae of Japan Part 3

19382C) than in the other species, so that the tube easily melts away when it is boiled in the KOH
solution. Furthermore, in the male of S. rufescens, the copulatory tube has a gland-like structure
at its lateral side (Fig. 82G, H). This gland-like structure is recognized in 3 males in our study,
but further studies are needed to conﬁrm whether it is certainly a gland of copulatory tube.
Stenus acutatus Naomi(Fig. 83A–H)
Stenus acutatus Naomi, 2012: 310; Naomi & Puthz, 2013: 145.
Type material examined. Holotype: ♂ (CBM), Kizuro, Kiwa, Mie Pref., 12. v. 1996, H.
Yokozeki leg. Paratypes: 1 ♂2 ♀, same data as holotype.
Distribution. Japan: Honshu (Mie Pref.).
Redescription. Male and female: Body 3.7–4.0 mm (fore body 1.8–2.0 mm) in length. Body
weakly shining; head black; pronotum, elytra and abdomen dark red to dark brown or almost
black; labrum dark red to dark brown; antennae and legs yellowish brown to reddish brown.
Body with punctures round to almost round, small to moderately large, and also pronotum partially with coarse punctures and elytra partially with large, coarse to subrugose punctures. Headshallowly to moderately concave, with a pair of longitudinal-oblique furrows; antennae short,very thin; pronotum with surface slightly uneven to uneven, with a median longitudinal furrow
indistinct to almost distinct; elytra with surface uneven; abdomen subcylindrical, subparallelsided; lateroventrites and tergoventral sutures lost.
Male: Abdomen (Fig. 83E) with a ﬂat area on the 6th, an elongate, deep depression on the
7th, and an arcuate, moderately deep emargination on the 8th ventrite (Fig. 83F); 9th tergum withventral apophyses moderately long; 9th ventrite (Fig. 83G) with apicolateral teeth moderately
long, acute, apicolateral setae long; 10th tergum very shallowly emarginate posteromedially.
Aedeagus (Fig. 83A) with median lobe elongate, obtusely angulate at apicolateral corners,
pointed at apex; apical sclerotized area subpentagonal, covered in about apical 1/2 with very thin,longitudinal lines which converge toward apex to some extent. Endophallus (Fig. 83A) with copulatory tube (Fig. 83C) having basal chamber comprising 2 short, thick rods, main tube thick,somewhat fusiform, slightly curved and obtusely pointed at apex; explusion hooks (Fig. 83H)
elongate, each with anterior plate curved mesially and acutely pointed at anterior tip; ventromedian bands long, moderately broad. Parameres (Fig. 83A) each very acutely pointed at apex, withpedical mesially with 4 short setae just before apical area; apical area moderately long, strongly
swollen mesially at base, mesially also with 7 to 8 setae of diﬀerent length.
Female: Eighth ventrite obtuse posteromedially; gonocoxites (Fig. 83B) each with apicolateral tooth very long, very acute, apicolateral setae long to very long. Spermatheca (Fig. 83D)
with capsule obtusely pointed at apex; striped duct slightly short, thick; duct moderately long,moderately thick, with 6 turns; basal valve short; basal duct moderately long.
Biology and ecology. The beetles of S. acutatus inhabit leaf litter heaped in the natural forests of a low mountainous region.
Remarks. S. acutatus is allied to S. rufescens, but it is separable from the latter species by theaedeagal median lobe with its apical sclerotized area elongate-pentagonal in shape (Fig. 83A),
the copulatory tube thinner at the apical part (Fig. 83C), the endophallic expulsion hook with its
anterior plate acutely pointed at the anterior tip (Fig. 83J), and the spermatheca with its duct
almost distinctly bent anteroposteriorly (Fig. 83C).

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Fig. 83. Stenus acutatus Naomi (Mie: Kiwa). A, aedeagus; B, gonocoxite; C, copulatory tube; D, spermartheca;
E, 6th and 7th ventrites of male; F, posterior part of 8th ventrite of male; G, 9th ventrite of male; H, endophallic expulsion hooks. Scale 1: 0.2 mm for A, G, 0.1 mm for B–D, H; scale 2: 0.25 mm for E; scale 3: 0.25 mm
for F.

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Stenus ichikawai Naomi(Fig. 84A–H)
Stenus ichikawai Naomi, 2006: 49; Naomi & Puthz, 2013: 145.
Type material examined. Holotype: ♂ (CBM), Mikizaki, Mie Pref., 1. iv. 1995, N. Narukawa
leg. Paratypes: 2 ♀, same data as holotype; 1 ♂3 ♀, Kukizaki, Kuki-cho, Owase City, Mie Pref.,28. i. 1996, K. Akita leg.; 1 ♂, same locality, 1. vi. 1996, H. Yokozeki leg.; 4 ♂2 ♀, same locality,
12. ii. 1996, H. Yokozeki leg.; 1 ♂, same locality, 11. iii. 1995, H. Yokozeki leg.; 3 ♂1 ♀,Nasazaki, Owase City, Mie Pref., 3. xi. 1997, F. Ichikawa leg.; 1 ♂, same locality, 11. iv. 1998, H.
Yokozeki leg.; 1 ♀ (CBM), same locality, 7. x. 1995, H. Yokozeki leg.
Distribution. Japan: Honshu (Mie Pref.).
Redescription. Male and female: Body 3.8–4.0 mm (fore body 1.9–2.0 mm) in length. Body
weakly shining; head and abdomen almost black to black; pronotum and elytra dark red near
black; labrum dark red; antennae and legs yellowish brown to reddish brown. Body with punctures round to ovoidal, small to moderately large, and also pronotum and elytra partially withcoarse to subrugose punctures. Head shallowly concave, with a pair of longitudinal-obliquedepressions; antennae moderately long, very thin; pronotum with surface slightly uneven to
uneven, with a median longitudinal furrow indistinct to almost distinct; elytra with surface
slightly uneven to uneven; abdomen subcylindrical, slightly tapering posteriorly to subparallelsided; lateroventrites and tergoventral sutures lost.
Male: Abdomen (Fig. 84F) modiﬁed with a ﬂat area on the 5th, a very large, moderately deep
depression on the 6th, a large, very deep depression on the 7th, and an arcuate, very shallow
emargination on the 8th ventrite (Fig. 84H); 9th tergum (Fig. 84A) with ventral apophyses long;
9th ventrite (Fig. B) with apicolateral teeth very long, very acute, apicolateral setae very long;
10th tergum (Fig. 84A) very shallowly emarginate posteromedially. Aedeagus with median lobe
(Fig. 84C) slender, becoming almost throughout narrower apicad, rounded at apicolateral corners, very acutely pointed at apex with a moderately long apicomedian cusp; apical sclerotizedarea narrow, elongate-subtriangular in shape, with a median longitudinal line in about apical 2/3.
Endophallus (Fig. 84C) with copulatory tube having basal chamber comprising a pair of thin,long rods, main tube thick at base, strongly curved; explusion hooks (Fig. 84G) elongate, eachwith anterior plate obtusely pointed at anterior tip; ventromedian bands moderately long, moderately broad. Parameres (Fig. 84C) moderately thick, each very acutely pointed at apex; apicalarea long, weakly swollen laterally, mesially with 11–14 setae of various length.
Female: Eighth ventrite obtuse posteromedially; gonocoxites (Fig. 84E) each with apicolateral tooth very long, very acute, apicolateral setae very long. Spermatheca (Fig. 84D) with capsule hardly developed; striped duct long, thick; duct very long, moderately thick to thick, tightly
coiled; basal valve very short; basal duct moderately long.
Biology and ecology. The beetles of S. ichikawai inhabit leaf litter heaped in the natural forests of lowlands to low mountainous regions.
Remarks. S. ichikawai is allied to S. jukata, but it is separable from the latter species by theaedeagal median lobe with its apical part broader (Fig. 84C), the copulatory tube with its maintube strongly curved (Fig. 84C), the endophallic expulsion hook with its anterior plate obtusely
pointed at the anterior tip (Fig. 84G), the paramere shorter, with its apical area shorter (Fig. 84C),
and the spermatheca with its duct thinner (Fig. 84D).
Etymology. This species is named after Mr. Futoshi Ichikawa (Mie) who collected some of196

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Fig. 84. Stenus ichikawai Naomi (Mie: A, Owase, B–E, G, H, Mikizaki, F, Nasazaki). A, 9th and 10th tergaof male; B, 9th ventrite of male; C, aedeagus; D, spermatheca; E, gonocoxite; F, 6th and 7th ventrites of male;G, endophallic expulsion hooks; H, posterior part of 8th ventrite of male. Scale 1: 0.2 mm for A–C, 0.1 mm for
D, E, G; scale 2: 0.25 mm for F; scale 3: 0.25 mm for H.

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the Stenus-beetles designated as the paratype specimens.
Stenus jukata Hromádka(Figs. 85A–H, 134F)
Stenus jukata Hromádka, 1982: 135; Herman, 2001: 2239; Naomi & Puthz, 2013: 145.
Type material examined. Holotype: ♂ (cP), Mt. Koya, Wakayama Pref., Japan, 24. iv. 1954,
K. Sawada leg.
Other material examined. [HONSHU]: 3 ♂1 ♀, Mt. Inamura, Ohmine, Nara Pref., 12. vi.
1993, T. Ito leg.; 4 ♂7 ♀, Dorogawa, Yamato, 2. vi. 1985, T. Ito leg.; 3 ♂2 ♀, Mt. Oomine, Yamato, 1. vi. 1985, T. Ito leg.; 1 ♂, Zenki Val. (700 m alt.), Shimokitayama Vil., Nara Pref., 29. vi.
1998, S. Nomura leg.; 1 ♂, Mt. Kohjin, Tateri, Nara Pref., 7. viii, 1966, T. Ito leg.; 2 ♂3 ♀, Mt.
Wasamata, Yamato, 14–15. vi. 1997, T. Ito leg.; 1 ♂1 ♀, Shinohara, Ohto Vil., Wakayama Pref.,26. vi. 1998, T. Kishimoto leg.; 1 ♂1 ♀, Mt. Koya, Wakayama Pref., 31. vii. 1995, I. Matoba leg.
Distribution. Japan: Honshu (Nara and Wakayama Prefs.).
Redescription. Male and female: Body 3.2–3.7 mm (fore body 1.6–1.9 mm) in length. Headweakly to moderately shining; head black, with clypeofrontal area and sometimes also medianpart of interocular area dark red; pronotum and elytra reddish orange to dark red; abdomen reddish brown to dark red, sometimes with apical segments infuscate; labrum reddish orange to reddish brown; antennae and legs yellowish brown to reddish brown. Body with punctures round to
ovoidal, small to moderately large, and also pronotum partially with subrugose punctures andelytra partially with large, subrugose punctures. Head moderately concave, with a pair of longitudinal-oblique furrows; antennae short, very thin; pronotum with surface slightly uneven to
uneven, with a median longitudinal furrow indistinct or almost distinct; elytra with surface
slightly uneven to uneven; abdomen subcylindrical, subparallel-sided; lateroventrites and tergoventral sutures lost.
Male: Abdomen (Fig. 85C) modiﬁed with a ﬂat area on each of the 4th and 5th, a very shallow, shallow or moderately deep depression on the 6th, a large, moderately deep or deep depression on the 7th, and an arcuate, broad, shallow emargination on the 8th ventrite (Fig. 85D); 9th
tergum (Fig. 85G) with ventral apophyses moderately long; 9th ventrite (Fig. 85F) with apicolateral teeth very long, very acute, apicolateral setae moderately long; 10th tergum (Fig. 85G) shallowly emarginate posteromedially. Aedeagus (Fig. 85E) with median lobe very slender, acutely
pointed at apex with a slightly long apicomedian cusp; apical sclerotized area elongate-subpentagonal in shape, very narrow. Endophallus (Fig. 85E) with copulatory tube moderately long,with basal chamber large, ovoidal, main tube attenuate, slightly bisinuous behind the middle;
explusion hooks (Fig. 85A) very elongate, each very acutely pointed at anterior tip, well-roundedat posterior tip; ventromedian bands moderately long, moderately broad. Parameres (Fig. 85E)
each very acutely pointed at apex; apical area very long, broadened dorsoventrally, mesially with
16–17 setae.
Female: Eighth ventrite obtuse posteromedially; gonocoxites (Fig. 85H) each with apicolateral tooth very long, very acute, apicolateral setae very long. Spermatheca (Fig. 85B) with capsule hardly developed; striped duct long, thick to very thick; duct very long, moderately thick tothick, tightly coiled; basal valve short; basal duct short.
Biology and ecology. The beetles of S. jukata inhabit leaf litter heaped in the natural forestsof mountainous regions.

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Fig. 85. Stenus jukata Hromádka (Nara: A, D–F, Zenki Valley, B, C, H, Mt. Inamura, G. Mt. Oomine). A, endophallic expulsion hooks; B, spermatheca, C, 6th and 7th ventrites of male; D, posterior part of 8th ventrite ofmale; E, aedeagus; F, 9th ventrite of male; G, 9th and 10th terga of male; H, posterior part of gonocoxite.
Scale 1: 0.1 mm for A, B, H, 0.2 mm for E, F; scale 2: 0.25 mm for C; scale 3: 0.25 mm for D; scale 4: 0.2 mm
for G.

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199

Remarks. S. jukata is allied to S. ferus, but it is separable from the latter species by the aedeagal median lobe with its apical part narrower (Fig. 85E), the copulatory tube with its basal chamber shorter (Fig. 85E), the endophallic expulsion hook narrower (Fig. 85A), and the spermathecawith its duct longer (Fig. B85).
Etymology. The speciﬁc epithet of this species is derived from a summer casual kimono-wear
in Japan, yukata.
Stenus ferus Naomi(Fig. 86A–G)
Stenus ferus Naomi, 2012: 305; Naomi & Puthz, 2013: 145.
Type material examined. Holotype: ♂ (CBM), Sugari-cho, Owase City, Mie Pref., 19. i.
1997, A. Amagasu leg. Paratypes: 2 ♂2 ♀, same locality as holotype; 3 ♂5 ♀, Nako, Kisei-cho,
Watarai-gun, Mie Pref., 19. i. 1997, A. Amagasu leg.; 1 ♂2 ♀, Sugari, Owase City, Mie Pref., 13.
i. 1996, H. Yokozeki leg.
Distribution. Japan: Honshu (Mie Pref.).
Redescription. Male and female: Body 3.0–3.8 mm (fore body 1.6–1.9 mm) in length. Body
moderately shining; head black, sometimes with clypeofrontal or median area reddish brown todark red; pronotum and elytra reddish brown to brown or dark reddish brown; abdomen dark red
at basal segments, becoming darker toward apical segments which are almost black; labrum reddish brown to brown; antennae and legs yellowish brown to reddish brown. Body with puncturesround to ovoidal, small to moderately large, and also pronotum partially with subrugose punctures and elytra partially with large, coarse punctures. Head shallowly to moderately concave,with a pair of almost mesially- curved furrows; antennae moderately long, very thin; pronotumwith surface slightly uneven to uneven, with a median longitudinal furrow very indistinct orindistinct; elytra with surface slightly uneven to uneven; abdomen subcylindrical, slightly tapering posteriorly to subparallel-sided; lateroventrites lost, tergoventral sutures very thin in the 4th,
lost in 5th and 6th segments.
Male: Abdomen modiﬁed with a ﬂat area on the 5th, a very shallow depression on the 6th, amoderately deep or deep depression on the 7th, and an arcuate, broad, shallow emargination on
the 8th ventrite (Fig. 86D); 9th tergum (Fig. 86C) with ventral apophyses slightly short; 9th ventrite (Fig. 86B) with apicolateral teeth long, obtusely pointed, apicolateral setae moderately long;
10th tergum (Fig. 86C) shallowly emarginate posteromedially. Aedeagus with median lobe (Fig.
86A) very slender, well-rounded at apicolateral corners, very acutely pointed at apex with a moderately long apicomedian cusp; apical sclerotized area nearly triangular, bisinuate basally. Endophallus (Fig. 86A) with copulatory tube with basal chamber very long, main tube moderately
long, attenuate, slightly curved (Fig. 86A); dorsolateral bands (Fig. 86A) thin; expulsion hooks(Fig. 86G) elongate, each with anterior plate acutely pointed at anterior tip, posterior plateobtusely angulate at posteromesial corner; ventromedian bands slightly short, moderately broad.
Parameres (Fig. 96A) moderately thick to thick, each very acutely pointed at apex; apical area
very long, moderately swollen laterally, mesially with 10 setae.
Female: Eighth ventrite obtuse posteromedially; gonocoxites (Fig. 86E) each with apicolateral tooth long, very acute, apicolateral setae short. Spermatheca (Fig. 86F) with capsule very
long, nearly fusiform, almost pointed at apex; striped duct short, moderately thick, somewhat
indistinct; duct slightly short, moderately thick, with 4 turns; gland small, spherical, with open-

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Fig. 86. Stenus ferus Naomi (Mie: A–D, F, Owase, E, G, Kisei). A, aedeagus; B, 9th ventrite of male; C, 9th and10th terga of male; D, 8th ventrite of male; E, gonocoxite; F, spermatheca; G, endophallic expulsion hooks.
Scale: 0.1 mm for A, B, F, 0.2 mm for C–E, 0.05 mm for G.

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201

ing located on the 3rd turn of duct; basal valve short; basal duct long.
Biology and ecology. The beetles of S. ferus inhabit leaf litter heaped in the natural forests oflowlands to low mountainous regions.
Remarks. S. ferus is allied to S. jukata, but it is separable from the latter species by the aedeagal median lobe with its apical part broader (Fig. 86A), the copulatory tube with its basal chamber longer (Fig. 86A), the endophallic expulsion hook broader (Fig. G), and the spermathecawith its duct shorter (Fig. 86F).
Stenus deltoides Naomi, Nomura & Kamezawa(Figs. 87A–G, 134G)
Stenus deltoides Naomi, Nomura & Kamezawa, 2015: 326.
Type material examined. Holotype: ♂ (NMNST), Karikomi Pond, Ohno City, Fukui Pref.,17. vi. 2001, H. Hoshina leg. Paratypes: 2 ♂1 ♀, same data as holotype; 1 ♂1 ♀, Roppon-hinoki,
Mt. Hakusan, Ishikawa Pref., 3. x. 2002, S. Nomura leg.
Distribution. Japan: Honshu (Ishikawa and Fukui Prefs.).
Redescription. Male and female: Body 3.5–3.7 mm (fore body 1.6–1.8 mm) in length. Body
moderately shining; head black; pronotum and elytra dark red; abdomen reddish brown throughdark red to black; labrum reddish brown; antennae and legs yellowish brown. Body with punctures round to elliptical, small to moderately large, and also pronotum partially with coarse punctures and elytra partially with large, coarse to subrugose punctures. Head moderately concave,with a pair of longitudinal-oblique furrows; antennae short to moderately long, thin; pronotumwith surface uneven, with a median longitudinal furrow very indistinct; elytra with surface
slightly uneven to uneven; abdomen subcylindrical, subparallel-sided; tergoventral sutures completely lost but lateroventrites each thin, running in a superﬁcial way.
Male: Abdomen (Fig. 87A) modiﬁed with a semicircular, ﬂat area on the 6th, an elongate,
shallow depression on the 7th, and an arcuate, moderately deep emargination on the 8th ventrite(Fig. 87D); 9th tergum (Fig. 87B) with ventral apophyses long; 9th ventrite (Fig. 87C) with macrosetae moderately long, apicolateral teeth short, very acute, apicolateral setae moderately long;
10th tergum (Fig. 87B) entire. Aedeagus (Fig. 87G) with median lobe moderately broad at base,almost parallel-sided before apicolateral corners, acutely pointed at apex; apical sclerotized area
triangular, small. Endophallus (Fig. 87G) with copulatory tube short, with basal chamber small,
main tube thick at base, strongly bent at the part a little distal from the thick basal part; dorsolateral bands very thin; expulsion hooks each with anterior plate completely fused with posterior
plate, each hook elongate-subtriangular in shape, mesially protruding at the middle of mesial
part; ventromedian bands long, thin. Parameres (Fig. 87G) each very acutely pointed at apex;
apical area very long, slightly broad when seen laterally, mesially with 12 to 13 setae.
Female: Eighth ventrite obtuse posteromedially; gonocoxites (Fig. 87E) each with apicolateral tooth long, very acute, apicolateral setae very long. Spermatheca (Fig. 87F) with capsulelarge, well-rounded apically; striped duct long, thick to very thick; duct moderately long, thin tomoderately broad, loosely coiled with 6 to 7 turns; gland with opening located on the lateral sideof duct a little proximal from the base of striped duct; basal valve short; basal duct sclerotized,
moderately long, thin; basal pouch conical. Basal structure (Fig. 87F) very large, truncated-conical in shape.
Biology and ecology. The beetles of S. deltoides inhabit leaf litter heaped in the natural for-

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Fig. 87. Stenus deltoides Naomi, Nomura & Kamezawa (Fukui: A, Karikomi Pond; Ishikawa, B–G: Mt. Hakusan). A, 6th and 7th ventrites of male; B, 9th and 10th terga of male; C, 9th ventrite of male; D, 8th ventrite ofmale; E, posterior parts of gonocoxites; F, spermatheca; G, aedeagus. Scale 1: 0.3 mm for A; scale 2: 0.2 mm
for B–D, G, 0.1 mm for E, F.

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203

ests of low mountainous to high mountainous regions.
Remarks. S. deltoides is allied to S. ohtoensis and S. cygnipenis, but it is separable from thelatter 2 species by the aedeagal median lobe almost parallel-sided before the apicolateral corners(Fig. 87G), the endophallic expulsion hook elongate-subtriangular in shape (Fig. 87G), the ventromedian band much thinner (Fig. 87G), and the paramere with its apical area longer (Fig. 87G).
Stenus ohtoensis Naomi(Fig. 88A–H)
Stenus ohtoensis Naomi, 2006: 38; Naomi & Puthz, 2013: 145.
Type material examined. Holotype: ♂ (CBM), Mt. Ohto, Wakayama Pref., 28–29. vi. 1981,
S. Naomi leg. Paratypes: 1 ♀ (CBM), same data as holotype; 9 ♂9 ♀, same data as holotype.
Distribution. Japan: Honshu (Wakayama Pref.).
Redescription. Male and female: Body 3.5–3.8 mm (fore body 1.7–1.9 mm) in length. Body
moderately to strongly shining; head black, sometimes with median or clypeofrontal area dark
red; pronotum and elytra reddish brown to dark reddish brown; abdomen dark reddish brown todark red or dark red near black; labrum reddish brown; antennae yellowish brown to reddish
brown. Body with punctures round to elliptical, small to moderately large, and also pronotum
partially with coarse to subrugose punctures and elytra partially with large, subrugose punctures.
Head moderately concave, with a pair of mesially-curved furrows; antennae moderately long,very thin; pronotum with surface slightly uneven to uneven, with a median longitudinal furrow
indistinct to almost distinct; elytra with surface uneven; abdomen subcylindrical, subparallelsided; lateroventrites and tergoventrite sutures lost.
Male: Abdomen (Fig. 88F) modiﬁed with a ﬂat area on the 5th, and a shallow depression on
the 6th, a very deep depression on the 7th, and a very shallow emargination on the 8th ventrite(Fig. 88H); 9th tergum with ventral apophyses moderately long; 9th ventrite (Fig. 88E) with apicolateral teeth moderately long, acute, apicolateral setae moderately long; 10th tergum entire.
Aedeagus (Fig. 88B) with median lobe strongly narrowing apicad, weakly bi-sinuate laterally inthe apical 1/2, narrowly rounded at apicolateral corners, acutely pointed at apex; apical sclerotized area subtriangular, with a median longitudinal line. Endophallus (Fig. 88B) with copulatory
tube (Fig. 88C) with basal chamber comprising a broad plate and a rod, main tube baculiform,
attenuate, weakly curved on its way; expulsion hooks (Fig. 88G) located almost parallel to eachother, each elongate, subparallel-sided, with posterior plate obtusely angulate at posterolateralcorner; ventromedian bands long, moderately broad. Parameres (Fig. 88B) each very acutely
pointed at apex; apical area long, mesially with 11 long to very long setae.
Female: Eighth ventrite obtuse posteromedially; gonocoxites (Fig. 88I) each with apicolateral tooth very long, very acute, apicolateral setae very long. Spermatheca (Fig. 88A) with capsule very small, almost rounded apically; striped duct long, moderately thick to thick; duct short,moderately thick to thick, coiled with 4 turns; gland with opening located on the lateral side ofduct between the 3rd and 4th turns; basal valve very short; basal duct long; basal pouch broadsubconical in shape, membranous.
Biology and ecology. The beetles of S. ohtoensis inhabit leaf litter heaped in the natural forests of a mountainous region.
Remarks. S. ohtoensis is allied to S. cygnipenis, but it is separable from the latter species by
the 8th ventrite of male very shallowly emarginate posteriorly (Fig. 88F), the copulatory tube

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Fig. 88. Stenus ohtoensis Naomi (Wakayama: Mt. Ohto). A, spermatheca; B, aedeagus; C, copulatory tube; D, 9th
ventrite of male; E, 6th and 7th ventrites of male; F, posterior part of 8th ventrite of male; G, endophallic
expulsion hooks; H, gonocoxite. Scale 1: 0.1 mm for A, C, G, H, 0.2 mm for B, D; scale 2: 0.25 mm for E;
scale 3: 0.25 mm for F.

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205with its main tube once weakly curved on its way, without any modiﬁcation at base (Fig. 88C),
the endophallic expulsion hook with its anterior plate broader and almost rounded anterolaterally; (Fig. 88G), and the spermatheca with its duct thicker (Fig. 88A).
Stenus cygnipenis Puthz(Fig. 89A–G)
Stenus cygnipenis Puthz, 2001: 52; Naomi & Puthz, 2013: 145.
Type material examined. Holotype: ♂ (SMNHS), near Hirai (ca 300 m), Wakayama Pref., 14.
vii. 1999, V. Puthz leg. Paratypes: 1 ♂1 ♀, same data as holotype.
Distribution. Japan: Honshu (Wakayama Pref.).
Redescription. Male and female: Body 3.7–4.3 mm (fore body 1.9–2.1 mm) in length. Body
moderately to strongly shining; head black or with anterior marginal area reddish brown to dark
red; pronotum and elytra yellowish brown to reddish brown; abdomen dark reddish brown todark brown; labrum reddish brown to dark brown; antennae and legs yellow brown to pale reddish brown. Body with punctures round to ovoidal, small to moderately large, and also pronotumand elytra partially with subrugose punctures. Head moderately concave, with a pair of longitudinal-oblique furrows; antennae moderately long, very thin; pronotum with surface slightly unevento uneven, with a median longitudinal furrow indistinct to almost distinct; elytra with surface
uneven; abdomen subcylindrical, subparallel-sided; lateroventrites and tergoventrite sutures lost.
Male: Abdomen (Fig. 89F) modiﬁed with a ﬂat area on the 4th, a very large, almost ﬂat areaon the 5th, a moderately deep depression on the 6th, and a very deep depression on the 7th, and aposterior truncation on the 8th ventrite (Fig. 89G); 9th tergum with ventral apophyses moderately
long; 9th ventrite (Fig. 89E) with apicolateral teeth slightly short, very acute, apicolateral setae
slightly short; 10th tergum very shallowly emarginate posteromedially. Aedeagus (Fig. 89B) withmedian lobe strongly narrowing apicad in the apical 1/2, narrowly rounded at apicolateral corners, acutely pointed at apex; apical sclerotized area subtriangular. Endophallus (Fig. 89B) withcopulatory tube with basal chamber small, dorsally with a triangular emargination, main tube
strongly expanding ventrally to form a pair of angulate ﬂaps near the basal 1/3, twice strongly
curved behind the angulate ﬂaps; expulsion hooks elongate, each with anterior plate attenuate,
moderately curved mesially at anterior tip; ventromedian bands slightly short, moderately broad.
Parameres (Fig. 89A) each very acutely pointed at apex; apical area long, mesially with 12 to 13
moderately long setae.
Female: Eighth ventrite obtuse posteromedially; gonocoxites (Fig. 89I) each with apicolateral tooth long, very acute, apicolateral setae very long. Spermatheca (Fig. 89E) with capsulevery long, rounded apically; striped duct slightly short, thick; duct short, moderately thick, coiled
with 4 turns; basal valve very short; basal duct moderately long; basal pouch broad-subconical inshape, membranous.
Biology and ecology. The beetles of S. cygnipenis inhabit leaf litter heaped in the natural forests of a mountainous region.
Remarks. S. cygnipenis is allied to S. ohtoensis, but it is separable from the latter species by
the 8th ventrite of male truncate posteriorly (Fig. 89G), the copulatory tube with its main tube
twice weakly curved on its way, ventrally with a pair of angulate ﬂaps near the basal 1/3 (Fig.
89B), the endophallic expulsion hook with its anterior plate narrower, attenuate anteriod, andmoderately curved mesially at the anterior tip (Fig. 89B), and the spermatheca with its duct thin-206

Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

Fig. 89. Stenus cygnipenis Puthz (Wakayama: Hirai). A, aedeagus; B, endophallic copulatory tube, expulsion
hooks and ventromedian bands; C, gonocoxite; D, 9th ventrite of male; E, spermatheca; F, 6th and 7th ventrites of male; G, posterior part of 8th ventrite of male. Scale 1: 0.2 mm for A, D, 0.1 mm for B, C, E; scale 2:0.25 mm for F; scale 3: 0.25 mm for G.

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Fig. 90. Stenus agrestis Naomi (Mie: Nanto). A, aedeagus; B, 9th ventrite of male; C, copulatory tube; D, endophallic expulsion hooks; E, posterior part of 8th ventrite of male; F, 6th and 7th ventrites of male. Scale 1:
0.2 mm for A, B, 0.1 mm for C, D; scale 2: 0.25 mm for E; scale 3: 0.25 mm for F.

ner (Fig. 89E).
Stenus agrestis Naomi(Fig. 90A–F)
Stenus agrestis Naomi, 2006: 42; Naomi & Puthz, 2013: 145.

leg.

Type material examined. Holotype: ♂ (CBM), Nanto, Mie Pref., 26. ii. 1987, A. Amagasu

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Distribution. Japan: Honshu (Mie Pref.).
Redescription. Male: Body 4.5 mm (fore body 2.1 mm) in length. Body moderately shining.
Head black, with clypeofrontal area dark red; pronotum and elytra dark red; abdomen dark reddish brown, with apical segments almost black; labrum, antennae and legs reddish brown. Body
with punctures round to almost round, small to moderately large, and also pronotum and elytra
partially with subrugose punctures. Head moderately concave, with a pair of longitudinal-obliquefurrows; antennae moderately long, very thin; pronotum with surface slightly uneven, with a
median longitudinal furrow very indistinct; elytra with surface uneven; abdomen subcylindrical,
subparallel-sided; lateroventrites and tergoventrite sutures lost.
Abdomen (Fig. 90F) modiﬁed with a ﬂat area on each of the 4th and 5th, a deep depression
on the 6th, a deep anteromedian and a deep posteromedian depression on the 7th, and an arcuate,
large, moderately deep emargination on the 8th ventrite (Fig. 90E); 9th tergum with ventral
apophyses long; 9th ventrite (Fig. 90B) with apicolateral teeth moderately long, very acute, apicolateral setae slightly short; 10th tergum very shallowly emarginate posteromedially. Aedeagus(Fig. 90A) with median lobe strongly narrowing apicad in the apical 1/2, almost acutely pointed
at apex; apical sclerotized area almost triangular. Endophallus (Fig. 90A) with copulatory tube
(Fig. 90C) having basal chamber large, ovoidal, main tube baculiform, bifurcate at apex so that
apical tube arising from the dorsal surface a little proximal from the apex of basal tube (or basal
tube having a horn-like process at apicoventral part), apical tube attenuate, weakly curved; dorsolateral bands very thin; expulsion hooks (Fig. 90D) each with anterior plate membranous,
pointed at anterior tip, posterior plate broad, angulate at posterolateral corner; ventromedianbands moderately long, moderately broad. Parameres (Fig. 90A) each very acutely pointed atapex; apical area long, mesially with 8 to 10 long to very long setae.
Female: Unknown.
Biology and ecology. The beetle of S. agrestis inhabits leaf litter heaped in the natural forestof a low mountainous region.
Remarks. S. agrestis is allied to S. olliforms, but it is separable from the latter species by the
6th ventrite of male with a larger depression (Fig. 90F), the aedeagal median lobe broader (Fig.
90A), the copulatory tube with its basal tube having a horn-like process at the apicoventral part(Fig. 90C), the endophallic expulsion hook with its posterior plate broader and angulate at theposterolateral corner (Fig. 90D).
Stenus olliformis Naomi(Figs. 91A–I, 134H)
Stenus olliformis Naomi, 2006: 44.
Stenus olliformis owasenus Naomi, 2006: 46. New synonym.
Type material examined. Holotype of S. olliformis: ♂ (CBM), Mt. Inamura, Oomine, Nara
Pref., 16. vi. 1995, T. Ito leg. Paratypes of S. olliformis: 1 ♀(CBM), same data as holotype;2 ♂1 ♀, same locality, 23. vii. 1994, T. Ito leg.; 1 ♂, same locality, 22. vii. 1994, T. Ito leg.; 1 ♂,same locality, 11. vi. 1993, T. Ito leg.; 2 ♀, same locality, 17. vi. 1995, T. Ito leg.
Holotype of S. olliformis owasenus: ♂ (CBM), Sugari, Owase City, Mie Pref., 13. i. 1996, H.
Yokozeki leg.
Other material examined. [HONSHU]: 2 ♂, Kiinagashima-cho, Mie Pref., 9. ii. 1992, H.
Yokozeki leg.

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Fig. 91. Stenus olliformis Naomi. (Nara: A–F, H, I, Mt. Inamura, G, Owase). A, spermatheca; B, aedeagus; C,
copulatory tube; D, 9th ventrite of male; E, gonocoxite; F, G, endophallic expulsion hooks; H, 6th and 7th
ventrites of male; I, posterior part of 8th ventrite of male. Scale 1: 0.1 mm for A, C, E–G, 0.2 mm for B, D;
scale 2: 0.25 mm for H; scale 3: 0.2 mm for I.

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Distribution. Japan: Honshu (Nara and Mie Prefs.).
Redescription. Male and female: Body 4.3–5.2 mm (fore body 2.1–2.5 mm) in length. Body
moderately shining; head black or with anterior marginal area dark red near black; pronotum,
elytra and abdomen reddish brown to dark red; labrum reddish brown; antennae and legs yellowish brown to reddish brown. Body with punctures round to ovoidal, small to moderately large,
and also pronotum and elytra partially with subrugose punctures. Head moderately concave, witha pair of mesially-curved furrows; antennae short to moderately long, very thin; pronotum withsurface slightly uneven, with a median longitudinal furrow indistinct to almost distinct; elytra
with surface uneven; abdomen subcylindrical, subparallel-sided; lateroventrites and tergoventrite
sutures lost.
Male: Abdomen (Fig. 91H) modiﬁed with a small ﬂat area on the 5th, a moderately deep
depression on the 6th, a moderately deep anteromedian and a deep posteromedian depressions on
the 7th, and a large, subtriangular, deep emargination on the 8th ventrite (Fig. 91I); 9th tergum
with ventral apophyses moderately long; 9th ventrite (Fig. 91D) with macrosetae very short, apicolateral teeth short, very acute, apicolateral setae moderately long; 10th tergum entire. Aedeagus(Fig. 91B) with median lobe narrowly rounded at apicolateral corners, almost acutely pointed atapex; apical sclerotized area small, subtriangular. Endophallus (Fig. 91B) with copulatory tube
(Fig. 91C) having basal tube baculiform, thick, slightly thickening apicad, almost rounded apically, apical tube arising from the dorsal surface near the apex of basal tube, thin, slightly attenuate, weakly curved; dorsolateral bands thin; expulsion hooks (Fig. 91F, G) with apical plates
diverging anteriorly, each obtusely pointed at anterior tip, posterior plate almost rounded (Fig.
91F) or almost truncate (Fig. 91G) at posterior tip; ventromedian bands slightly short, very thin.
Parameres (Fig. 91B) each very acutely pointed at apex; apical area moderately long, mesiallywith 9 setae.
Female: Eighth ventrite obtuse posteromedially; gonocoxites (Fig. 91F) each with apicolateral tooth slightly short, very acute, apicolateral setae long. Spermatheca (Fig. 91A) with capsulevery thick, well-rounded apically; striped duct very long, moderately thick to thick; duct moderately long, slightly thin to moderately thick; gland with opening located on the lateral side ofduct between the last and last 2nd turns.
Biology and ecology. The beetles of S. olliformis inhabit leaf litter heaped in the natural forests of low mountainous to mountainous regions.
Remarks. S. olliformis owasenis was newly described as the subspecies of S. olliformis,
based on one specimen (holotype) of male beetle collected from the same locality (Mie Pref.) asthat of nominotypical subspecies in Naomi (2006). This is mainly based on the small, morphological diﬀerences between them regarding the shape of the anterior and posterior plates of endophallic expulsion hooks, etc. We compared again the expulsion hooks of S. olliformis (Fig. 91F)
with those of S. olliformis owasenis (Fig. 91G) in the present study. However, since these diﬀerences can be regarded as infraspeciﬁc variations, S. olliformis owasenis Naomi, 2006 is newly
placed in synonym with S. olliformis Naomi.
S. olliformis is allied to S. agrestis, but it is separable from the latter species by the 6th ventrite of male with a smaller depression (Fig. 91H), the aedeagal median lobe narrower (Fig.
91A), the copulatory tube with its basal tube slightly protruding posteriorly beyond the base of
apical tube (Fig. 91C), the endophallic expulsion hook with its posterior plate narrower and usually more or less rounded posterolaterally (Fig. 91F, G).

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Stenus ebisu Naomi(Figs. 92A–H, 134I)
Stenus ebisu Naomi, 2006: 47; Naomi & Puthz, 2013: 145.
Type material examined. Holotype: ♂ (CBM), Ohdaigahara, Nara Pref., 29. v. 1985, S.
Nomura leg. Paratypes: 1 ♀ (CBM) & 6 ♀, same data as holotype; 1 ♂2 ♀, same locality, 25–26.
vi. 1981, S. Naomi leg.
Other material examined. [HONSHU]: 5 ♂1 ♀, Tategasaki, Kumano City, Mie Pref., 28. ii.
1998, H. Yokozeki leg.
Distribution. Japan: Honshu (Nara and Mie Prefs.).
Redescription. Male and female: Body 3.8–4.7 mm (fore body 1.9–2.3 mm) in length. Body
moderately to strongly shining; head black, with anterior marginal or clypeofrontal area reddish
brown; pronotum and elytra reddish brown to dark reddish brown; abdomen reddish brown withapical segments infuscate, or entirely dark brown near black; labrum reddish brown; antennae
and legs yellowish brown to reddish brown. Body with punctures round to ovoidal, small tomoderately large, and also pronotum partially with subrugose punctures and elytra partially withlarge, subrugose punctures. Head moderately concave, with a pair of longitudinal-oblique furrows; antennae short to moderately long, very thin; pronotum with surface slightly uneven to
uneven, with a median longitudinal furrow indistinct to almost distinct; elytra with surface
uneven; abdomen subcylindrical, subparallel-sided; lateroventrites and tergoventrite sutures lost.
Male: Abdomen (Fig. 92G) modiﬁed with a ﬂat area on the 4th, a very shallow depression on
the 5th, a shallow depression on the 6th, a deep depression on the 7th, and a very large, nearly
semicircular, deep emargination on the 8th ventrite (Fig. 92H); 9th tergum with ventral apophyses slightly short; 9th ventrite (Fig. 92D) with macrosetae long, apicolateral teeth short, acute,apicolateral setae moderately long; 10th tergum entire. Aedeagus (Fig. 92B) with median lobe
strongly narrowing apicad in about apical 1/3, narrowly rounded at apicolateral corners, obtusely
pointed at apex; apical sclerotized area subtriangular. Endophallus (Fig. 92B) with copulatory
tube (Fig. 92C) having basal chamber and basal tube together gourd-shaped, basal tube fusiform,
apical tube arising from the dorsal surface near the apex of basal tube, thin, baculiform, with apair of minute denticles at the middle of ventral rims; dorsolateral bands thin; expulsion hooks(Fig. 92F) each tadpole-shaped, very acutely pointed at anterior tip, with posterior plate nearly
ovoidal, much shorter than anterior plate; ventromedian bands moderately long, each narrow atbase, becoming broader anteriod. Parameres (Fig. 92B) each acutely pointed at apex; apical area
long, mesially with 8 setae of various length.
Female: Eighth ventrite obtuse posteromedially; gonocoxites (Fig. 92F) each with apicolateral tooth slightly short, very acute, apicolateral setae long. Spermatheca (Fig. 92A) with capsulevery thick, well-rounded apically; striped duct very long, moderately thick to very thick; duct
moderately long, slightly thin to moderately thick; gland small, spherical, with opening locatedon the duct between the last and last 2nd turns.
Biology and ecology. The beetles of S. ebisu inhabit leaf litter heaped in the natural forests oflowlands to mountainous regions.
Remarks. S. ebisu is allied to S. olliformis and S. agrestis, but it is easily separable from thelatter 2 species by the copulatory tube with its basal chamber and basal tube together gourdshaped (Fig. 92C) and the endophallic expulsion hook tadpole-shaped (Fig. 92F).
Etymology. The speciﬁc epithet of this species is derived from the name of one of the Seven

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Fig. 92. Stenus ebisu Naomi (Nara: Ohdaigahara). A, spermatheca; B, aedeagus; C, copulatory tube; D, 9th ventrite of male; E, gonocoxite; F, endophallic expulsion hooks; G, 6th and 7th ventrites of male; H, posterior partof 8th ventrite of male. Scale 1: 0.1 mm for A, C, E, F, 0.2 mm for B, D; scale 2: 0.25 mm for G; scale 3:0.25 mm for H.

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Gods of Good Fortune, Ebisu.
Stenus wasabi Hromádka(Fig. 93A–H)
Stenus wasabi Hromádka, 1982: 133; Herman, 2001: 2436; Naomi & Puthz, 2013: 145.
Type material examined. Holotype: ♂ (NHMG), Mt. Daimonji, Kyoto Pref., 20. ix. 1966, K.
Sawada leg.
Other material examined. [HONSHU]: 7 ♂11 ♀, Kurama, Kyoto, 9. viii. 1985, T. Ito leg.;1 ♂1 ♀, Daimonji, Kyoto, 18. vi. 1989, T. Ito leg.; 1 ♂, Kibune, Kyoto, 31. viii. 1992, T. Ito leg.;3 ♂3 ♀, Kitayama, Kamiohkubu, Mizuho T., Kyoto, 1. v. 1999, Y. Hayashi leg.; 2 ♂, Iwakura,
Kyoto, 11. iv. 1981, T. Ogata leg.; 1 ♂3 ♀, Tentaki, Ooya-cho, Hyogo Pref., 8. vi. 1996, H.
Hoshina leg.; 1 ♂, Shinomi, Sasayama T., Hyogo, 24. v. 1986, Y. Hayashi leg.; 1 ♀, Kagobou,
Sasayama T., Hyogo, 10. x. 1985, Y. Hayashi leg.; 1 ♂, Mt. Amaishi, Sasayama T., Hyogo, 1. vii.
1982, Y. Hayashi leg.; 8 ♂7 ♀, Takara Temple, Yamazaki, Hyogo Pref., 30. ix. 1989, T. Ito leg.
Distribution. Japan: Honshu (Kyoto and Hyogo Prefs.).
Redescription. Male and female: Body 3.6–3.9 mm in length (fore body 1.8–2.0 mm). Body
moderately shining; head reddish orange to reddish brown, with lateral parts of interocular area
more or less infuscate; pronotum and elytra reddish orange; abdomen reddish brown to dark reddish brown with apical segments more or less infuscate; labrum reddish orange; antennae andlegs yellowish brown to reddish brown. Body with punctures round to elliptical, small to moderately large, and also pronotum partially with coarse to subrugose punctures and elytra partiallywith large, coarse to subrugose punctures. Head moderately concave, with a pair of longitudinaloblique or almost mesially-curved furrows; antennae short to moderately long, very thin; pronotum with surface slightly uneven, with a median longitudinal furrow indistinct; elytra with surface uneven; abdomen subcylindrical, slightly tapering posteriorly to subparallel-sided;
lateroventrites and tergoventrite sutures lost.
Male: Abdomen (Fig. 93E) modiﬁed with a ﬂat area on the 4th, a shallow depression on the
5th, a moderately deep depression on the 6th, a deep depression on the 7th, and an arcuate,
slightly broad emargination on the 8th ventrite (Fig. 93H); 9th tergum (Fig. 93B) with ventral
apophyses very long; 9th ventrite (Fig. 93F) with apicolateral teeth very short, very acute, apicolateral setae slightly short; 10th tergum shallowly emarginate posteriorly (Fig. 93B). Aedeagus(Fig. 93C) with median lobe strongly narrowing apicad and very shallowly bisinuate laterally inthe apical 1/2, very acutely pointed at apex; apical sclerotized area small, elongate-subtriangularin shape. Endophallus (Fig. 93C) with copulatory tube having basal chamber large, subconical,
main tube twice moderately curved or bent on its way, beak-shaped at apex; expulsion hooks(Fig. 93D) connected each other at the mesial angulate corners a little behind the middle of posterior plates, each with anterior plate anterolaterally curved, acute at anterior tip, posterior plate
moderately broad at base, narrowly rounded at posterior tip; ventromedian bands short, very thin.
Parameres (Fig. 93C) each very acutely pointed at apex; apical area long, mesially with 15 to 16
setae of various length.
Female: Eighth ventrite obtuse posteromedially; gonocoxites (Fig. 93G) each with apicolateral tooth long, acute, apicolateral setae long. Spermatheca (Fig. 93A) with capsule short; striped
duct moderately long, very thick; duct extremely long, thin, with its anterior mass tightly coiled;basal valve short; basal duct moderately long.

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Fig. 93. Stenus wasabi Hromádka (Kyoto: A, E, G, H, Kurama, B, D, Mizuho. C, F, Mt. Daimonji). A, spermatheca; B, 9th and 10th terga of male; C, aedeagus; D, endophallic expulsion hooks; E, 6th and 7th ventrites ofmale; F, 9th ventrite of male; G, gonocoxite; H, posterior part of 8th ventrite of male. Scale 1: 0.1 mm for A,
D, G, 0.2 mm for B, C, F; scale 2: 0.25 mm for E; scale 3: 0.25 mm for H.

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215

Biology and ecology. The beetles of S. wasabi inhabit leaf litter heaped in the natural forestsof low mountainous to mountainous regions.
Remarks. S. wasabi is allied to S. daigonis and S. ingens, but it is separable from the latter 2
species by the endophallic expulsion hooks connected each other behind the middle of posterior
plates, and each hook with its posterior plate narrowly rounded at the apex (Fig. 93D).
Etymology. The speciﬁc epithet of this species is derived from the Japanese name of horseradish genus Armoracia, wasabi.
Stenus daigonis Naomi & Puthz(Figs. 94A–K, 134J)
Stenus daigonis Naomi & Puthz, 1993: 310; Herman, 2001: 2155; Naomi & Puthz, 2013: 145.
Type material examined. Holotype: ♂ (SMNHS), Daigo, Kyoto Pref., 21. v. 1973, K. Sawada
leg. Paratype: 1 ♀ (cP), same data as holotype.
Other material examined. [HONSHU]: 1 ♂4 ♀, Uji, Kyoto, 30. xii. 1992, K. Mizuno leg.;1 ♂3 ♀, Amagase, Uji, Kyoto, 26. iv. 1997, S. Takahashi leg.; 3 ♂1 ♀, Gounho, Uji, Kyoto, 16.
xii. 1995, S. Takahashi leg.; 2 ♂1 ♀, Higashikasatori, Uji, Kyoto, 3. iv. 1994, K. Mizuno leg.;1 ♂2 ♀, Sumiyama, Uji, Kyoto, 13. ii. 1993, K. Mizuno leg.; 2 ♂3 ♀, Mt. Jubusen, Kyoto, 15. ix.
1989, T. Ito leg.; 3 ♂1 ♀, Nonodo, Kyoto, 17. iv. 1994, T. Ito leg.; 1 ♂1 ♀, Daimonji, Kyoto, 7. x.
1989, T. Ito leg.; 5 ♂5 ♀, Mt. Daigo, Kyoto, 17. iv. 1994, T. Ito leg.; 1 ♂1 ♀, Suwa, Ueno City,
Mie Pref., 24. x. 1996, H. Yokozeki leg.; 1 ♂4 ♀, Okumura, Shimagahara, Ayama-gun, Mie Pref.,19. xi. 1995, H. Yokozeki leg.; 1 ♂, Sakura Pass, Ayama-cho, Ayama-gun, Mie Pref., 7. xii. 1996,
H. Yokozeki leg.
Distribution. Japan: Honshu (Kyoto and Mie Prefs.).
Redescription. Male and female: Body 3.3–4.0 mm (fore body 1.7–2.0 mm) in length. Body
moderately shining; head yellowish brown to reddish brown or dark red, with lateral parts ofinterocular area more or less infuscate; pronotum and elytra yellowish brown to reddish brown;
abdomen yellowish brown to reddish brown or dark red, with apical segments infuscate; labrum
reddish brown; antennae and legs yellow brown to reddish brown. Body with punctures round to
ovoidal, small to moderately large, and also pronotum partially with coarse to subrugose punctures and elytra partially with large, coarse to subrugose punctures. Head moderately concave,with a pair of longitudinal-oblique or almost mesially-curved furrows (or depressions); antennae
short to moderately long, very thin; pronotum with surface slightly uneven to uneven, with a
median longitudinal furrow very indistinct; elytra with surface slightly uneven to uneven; abdomen subcylindrical, slightly tapering posteriorly to subparallel-sided; lateroventrites and tergoventrite sutures lost.
Male: Abdomen (Fig. 94B) modiﬁed with a ﬂat area on each of the 3rd and 4th, a very shallow depression on the 5th, a moderately deep depression on the 6th, a deep depression on the 7th,
and a nearly semicircular emargination on the 8th ventrite (Fig. 94H); 9th tergum with ventral
apophyses moderately long; 9th ventrite (Fig. 94F) with apicolateral teeth short, acute, apicolateral setae slightly short; 10th tergum very shallowly emarginate posteromedially or entire (Fig.
94K). Aedeagus (Fig. 94E) with median lobe strongly narrowing apicad and very shallowly
bisinuate laterally in the apical 1/2, narrowly rounded at apicolateral corners, very acutely
pointed at apex; apical sclerotized area small, elongate-subtriangular in shape. Endophallus (Fig.
94E) with copulatory tube having basal chamber large, main tube twice moderately curved or

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Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

Fig. 94. Stenus daigonis Naomi & Puthz (Kyoto and Mie). A, spermatheca; B, 6th and 7th ventrites of male; C,
posterior part of 8th ventrite of female; D, gonocoxite; E, aedeagus; F, 9th ventrite of male; G, 9th and 10th
terga of female; H, posterior part of 8th ventrite of male; I, J, endophallic expulsion hooks; K, 10th tergum of
male. Scale 1: 0.1 mm for A, D, I, J, 0.2 mm for E–G, K; scale 2: 0.25 mm for B; scale 3: 0.25 mm for C, H.

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bent on its way, beak-shaped at apex; expulsion hooks (Fig. 94I, J) connected each other at themesial angulate corners a little before the middle of posterior plates, each with anterior plate
acutely pointed at anterior tip, posterior plate nearly tetragonal, broad at base, acute or very
acutely pointed at posterior tip, larger than (Fig. 94J) or about as large as (Fig. 94I) anterior
plate; ventromedian bands short, very thin. Parameres (Fig. 94E) each very acutely pointed atapex; apical area long, mesially with 14 to 15 setae of various length.
Female: Eighth ventrite rounded posteriorly; gonocoxites (Fig. 94D) each with apicolateral
tooth long, very acute, apicolateral setae very long. Spermatheca (Fig. 94A) with capsuleextremely short; striped duct very long, moderately thick to thick; duct moderately long, moderately thick; gland small, with opening located on the duct between the last 3rd and 4th turns;
basal valve very short; basal duct moderately long.
Biology and ecology. The beetles of S. daigonis inhabit leaf litter heaped in the natural forests of lowlands to low mountainous regions.
Remarks. S. daigonis is closely allied to S. ingens, but it is separable from the latter species
by the endophallic expulsion hooks connected each other at the mesial angulate corners a little
before the middle of posterior plates, and each hook with its posterior plate almost tetragonal,
usually broader at the base, and larger than (Fig. 94J) or about as large as (Fig. 94I) anterior
plate. In S. daigonis, the body are darker in color in the specimens of Mie Pref. examined than inthose of Kyoto Pref.
Stenus ingens Naomi（Fig. 95A–K)
Stenus ingens Naomi, 2006: 62; Naomi & Puthz, 2013: 145.
Stenus ingens ryugadakensis Naomi, 2006: 64; Naomi & Puthz, 2013: 145. New synonym.
Type material examined. Holotype of S. ingens: ♂ (CBM), Yunoyama, Komono-cho, Mie
Pref., 26. x. 1996, H. Yokozeki leg. Paratypes of S. ingens: 2 ♂, same locality, 5. i. 1997, H.
Yokozeki leg.
Holotype of S. ingens ryugadakensis: ♂ (CBM), Mt. Ryugadake, Daian-cho, Mie Pref., 23.
x. 1993, H. Yokozeki leg. Paratype: 1 ♂, Kirihata, Komono-cho, Mie Pref., 1. v. 1998, F.
Ichikawa leg
Distribution. Japan: Honshu (Mie Pref.).
Redescription. Male: Body 3.4–3.6 mm (fore body 1.7–1.8 mm) in length. Body moderately
shining; head dark red to dark reddish brown, with lateral parts of interocular area dark red near
black to black; pronotum and elytra reddish orange to reddish brown; abdomen dark red, withapical segments more or less infuscate; labrum reddish brown; antennae and legs yellow brown
to reddish brown. Body with punctures round to ovoidal, small to moderately large, and also pronotum and elytra partially with coarse to subrugose punctures. Head moderately concave, with apair of longitudinal-oblique furrows; antennae moderately long, very thin; pronotum with surface
slightly uneven to uneven, with a median longitudinal furrow very indistinct to indistinct; elytra
with surface slightly uneven; abdomen subcylindrical, slightly tapering posteriorly to subparallel-sided; lateroventrites and tergoventrite sutures lost.
Abdomen (Fig. 95A, G) modiﬁed with a ﬂat area on each of the 3rd and 4th or on the 4th, a
ﬂat area or a very shallow depression on the 5th, a shallow (Fig. 95J) or moderately deep (Fig.
95A) depression on the 6th, a moderately deep (Fig. 95J) or deep (Fig. 95A) depression on the218

Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

Fig. 95. Stenus ingens Naomi (Mie, A–G, K, Yunoyama, H–J, Mt. Ryugatake). A, J, 6th and 7th ventrites of male;B, posterior part of 8th ventrite of male; C, aedeagus; D, 9th ventrite of male; E–I, endophallic expulsion
hooks; K, copulatory tube. Scale 1: 0.25 mm for A, J; scale 2: 0.25 mm for B; scale 3: 0.2 mm for C, D,
0.1 mm for E–I, K.

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7th, and a moderately large, subtriangular emargination on the 8th ventrite; 9th tergum with ventral apophyses slightly short; 9th ventrite (Fig. 95D) with apicolateral teeth short, acute, apicolateral setae moderately long; 10th tergum entire. Aedeagus (Fig. 95C) with median lobe moderately narrowing apicad and very shallowly bisinuate laterally in the apical 1/2, very acutely
pointed at apex; apical sclerotized area elongate-subpentagonal to elongate-subtriangular inshape. Endophallus (Fig. 95C) with copulatory tube (Fig. 95K) having basal chamber very large,
main tube twice strongly curved or bend on its way, beak-shaped at apex; dorsolateral bands very
thin; expulsion hooks (Fig. 95E–I) if connected each other, connected at or near the basimesial
corners of posterior plates, each with anterior plate elongate-subtriangular in shape, usuallyslightly curved mesially and acute or very acute at anterior tip, posterior plate elongate-subtriangular in shape, acute or very acute at posterior tip, distinctly (Fig. 95E–G) or slightly smaller
than anterior plate (Fig. 95H–I); ventromedian bands slightly short, thin. Parameres (Fig. 95C)
each very acutely pointed at apex; apical area long, mesially with 18 setae of various length.
Female: Unknown.
Biology and ecology. The beetles of S. ingens inhabit leaf litter heaped in the natural forestsof lowlands to mountainous regions.
Remarks. S. ingens ryugatakensis was newly described as the subspecies of S. ingens, basedon two specimens of male beetles collected from the same locality (Mie Pref.) as that of nominotypical subspecies in Naomi (2006). This is mainly based on the small, morphological diﬀerences
between them regarding the abdominal modiﬁcations of male (depth of depressions, etc.) and theendophallic expulsion hooks (shapes of anterior and posterior plates, etc.). We compared theexpulsion hooks of S. ingens (Fig. 95A, E–G) with those of S. ingens ryugatakensis (Fig. 95J,
H–I) in the present study. However, since these diﬀerences can be regarded as infraspeciﬁc variations, S. ingens ryugatakensis Naomi, 2006 is newly placed in synonym with S. ingens Naomi,
2006.
S. ingens is closely allied to S. daigonis, but it is separable from the latter species by theendophallic expulsion hooks if connected each other, connected at or near the basimesial cornersof posterior plates, and each hook with its posterior plate almost elongate-subtriangular in shape,
usually narrower at the base and distinctly (Fig. 95E–G) or slightly smaller than anterior plate(Fig. 95H–I).
Stenus lubomiri Naomi(Fig. 96A–H)
Stenus nakanei Hromádka: Naomi, 1997b: 606 (misidentiﬁcation).
Stenus lubomiri Naomi, 2006: 64; Naomi & Puthz, 2013: 145.
Type material examined. Holotype: ♂ (CBM), Mt. Kasagi, Kyoto Pref., 2. iv. 1988, T. Ito leg.
Paratypes: 4 ♂11 ♀, same data as holotype, T. Ito leg.; 2 ♂3 ♀, same locality as holotype, 3. xi.
1984, T. Ito leg.; 3 ♂2 ♀, Kabusanji, Takatsuki, Osaka Pref., 13. ix. 1985, T. Ito leg.; 1 ♂1 ♀, Mt.
Kasuga, Nara Pref., 20. viii. 1980, P. M. Hammond leg.; 1 ♂, same locality, 20. iv. 1985, T. Itoleg.; 1 ♂, same locality, 31. x. 1992, T. Ito leg.; 1 ♀, same locality, 16. viii. 1994, T. Ito leg.; 1 ♀,same locality, 3. v. 1996, T. Ito leg.; 4 ♂10 ♀, Mt. Ikoma, Nara Pref., 6. v. 1985, T. Ito leg.;2 ♂5 ♀, Mt. Kamiji, Ise City, Mie Pref., 10. xii. 1967, Y. Hayashi leg.; 2 ♂2 ♀, Koraibiro, Ise
City, Mie Pref., 10. i. 1998, H. Ichihashi leg.; 1 ♀, same locality, 10. i. 1998, H. Yokozeki leg.;1 ♂, Kouchi, Anou-cho, Ayama-gun, Mie Pref., 23. xii. 1995, H. Yokozeki leg.

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Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

Fig. 96. Stenus lubomiri Naomi (Nara: A, D, F–H, Mt. Kasuga; B, C, E, Mt. Ikoma). A, 6th and 7th ventrites ofmale; B, 9th ventrite of male; C, spermatheca; D, aedeagus; E, gonocoxite; F, posterior part of 8th ventrite ofmale; G, 10th tergum of male; H, endophallic expulsion hooks. Scale 1: 0.25 mm for A; scale 2: 0.2 mm for B,
D, G, 0.1 mm for C, E, H; scale 3: 0.2 mm for F.

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Distribution. Japan: Honshu (Kinki District).
Redescription. Male and female: Body 3.6–3.9 mm (fore body 1.6–1.9 mm) in length. Body
moderately shining; head reddish orange to reddish brown, with lateral parts of interocular area
more or less infuscate; pronotum and elytra reddish orange; abdomen reddish brown to almost
brown, with apical segments more or less infuscate; labrum reddish orange; antennae and legs
yellow brown to reddish brown. Body with punctures round to elliptical, small to moderately
large, and also pronotum partially with coarse to subrugose punctures and elytra partially with
subrugose punctures. Head moderately concave, with a pair of longitudinal-oblique furrows;
antennae moderately long, very thin; pronotum with surface slightly uneven to uneven, with a
median longitudinal furrow indistinct; elytra with surface slightly uneven to uneven; abdomensubcylindrical, slightly tapering posteriorly; lateroventrites and tergoventrite sutures lost.
Male: Abdomen modiﬁed with a ﬂat area on each of the 3rd and 4th or on the 4th, a ﬂat area
or a shallow depression on the 5th, a shallow or a deep (Fig. 96A) depression on the 6th, a moderately deep or a very deep (Fig. 96A) depression on the 7th, and an arcuate, broad emarginationon the 8th ventrite (Fig. 96F); 9th tergum with ventral apophyses moderately long to long; 9th
ventrite (Fig. 96B) with apicolateral teeth short, acute, apicolateral setae short; 10th tergum
entire or shallowly emarginate posteromedially (Fig. 96G). Aedeagus (Fig. 96C) with median
lobe moderately or strongly narrowing apicad and very shallowly bisinuate laterally in the apical
1/2, very acutely pointed at apex; apical sclerotized area elongate-subtriangular in shape. Endophallus (Fig. 96D) with copulatory tube having basal chamber comprising 2 long rods, main tube
baculiform, long, thin, very weakly curved, with a short, very thin apicomedian process; expulsion hooks (Fig. 96H) each with anterior plate elongate, strongly protruding laterally or posterolaterally at posterolateral corner, narrowing apicad, slightly curved mesially at anterior tip, posterior plate elongate, narrow at base, almost pointed at posterior tip; ventromedian bands slightly
short, thin. Parameres (Fig. 96C) each very acutely pointed at apex; apical area long, slightly
swollen mesially at base, mesially also with 18 to 19 setae of various length.
Female: Eighth ventrite obtuse posteromedially; gonocoxites (Fig. 96D) each with apicolateral tooth long, acute, apicolateral setae long. Spermatheca (Fig. 96C) with capsule extremely
short; striped duct moderately long, thick to very thick; duct extremely long, very thin to moderately thick for the most part, with its anterior mass almost tightly coiled; gland moderate in size,with opening located on the duct between the last 2nd and 3rd turns; basal valve short; basal duct
long, with a pair of basal processes; basal pouch broad-subconical in shape.
Biology and ecology. The beetles of S. lubomiri inhabit leaf litter heaped in the natural forests of lowlands to low mountainous regions.
Remarks. S. lubomiri is allied to S. ichihashii, but it is separable from the latter species by
the copulatory tube narrower (Fig. 96D), and the endophallic expulsion hook with its anterior
plate narrower at the anterior part and strongly protruding laterally or posterolaterally at the posterolateral corner and its posterior plate narrower at base.
Etymology. This species is named after the late Mr. Lubomír Hromádka (Praha) who contributed to the clariﬁcation of Stenus fauna of Japan.
Stenus ichihashii Naomi(Fig. 97A–I)
Stenus ichihashii Naomi, 2006: 67; Naomi & Puthz, 2013: 145.
Stenus ichihashii miunensis Naomi, 2006: 70. New synonym.

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Fig. 97. Stenus ichihashii Naomi (Mie: A, B, D–I, Mt. Kuroso, C, Hirakura). A, spermatheca; B, 6th and 7th ventrites of male; C, 9th ventrite of male; D, apical part of of copulatory tube; E, aedeagus; F, gonocoxite; G, posterior part of 8th ventrite of female; H, endophallic expulsion hooks; I, posterior part of 9th tergum and 10th
tergum of male. Scale 1: 0.1 mm for A, D, F, 0.2 mm for C, E, I, 0.05 mm for H; scale 2: 0.25 mm for B; scale
3: 0.25 mm for G.

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223

Type material examined. Holotype of S. ichihashii: ♂ (CBM), Hirakura, Mie Pref., 20. xi.
1994, T. Ito leg. Paratypes of S. ichihashii: 1 ♀ (CBM), 1 ♂1 ♀, same data as holotype; 1 ♂,Asake-keikoku, Komono-cho, Mie Pref., 21. iii. 1995, H. Yokozeki leg.; 1 ♂1 ♀, Sekisuikei,
Kameyama City, Mie Pref., 23. ii. 1998, A. Amagasu leg.; 2 ♂2 ♀, Mt. Kuroso, Mie Pref., 2. x.
1993, T. Ito leg.
Holotype of S. ichihashii miunensis: ♂ (CBM), Mt. Miune, Nara Pref., 28. v. 1994, K.
Mizuno leg.
Distribution. Japan: Honshu (Nara and Mie Prefs.).
Redescription. Male and female: Body 3.6–4.1 mm (fore body 1.8–2.0 mm) in length.
Body moderately shining; head reddish orange to reddish brown or dark red, with lateralparts of interocular area more or less infuscate; pronotum and elytra reddish orange to reddish
brown; abdomen dark red to dark brown, with apical segments more or less infuscate; labrum,
antennae and legs yellow brown to reddish brown. Body with punctures round to ovoidal, small
to moderately large, and also pronotum partially with coarse to subrugose punctures and elytra
partially with large, subrugose punctures. Head moderately concave, with a pair of longitudinaloblique or almost mesially-curved furrows; antennae moderately long, very thin; pronotum withsurface almost smooth to uneven, with a median longitudinal furrow indistinct to almost indistinct; elytra with surface slightly uneven to uneven; abdomen subcylindrical, slightly tapering
posteriorly; lateroventrites and tergoventrite sutures lost.
Male: Abdomen modiﬁed sometimes with a ﬂat area on each of the 3rd to 5th, always with ashallow or a moderately deep (Fig. 97B) depression on the 6th, a deep or a very deep (Fig. 97B)
depression on the 7th, and an arcuate, moderately deep emargination on the 8th ventrite (Fig.
97G); 9th tergum (Fig. 97I) with ventral apophyses slightly short; 9th ventrite (Fig. 97C) withapicolateral tooth very short, very acute; 10th tergum (Fig. 97I) shallowly emarginate posteromedially. Aedeagus (Fig. 97E) with median lobe moderately narrowing apicad and very shallowly
bisinuate laterally in about apical 1/2, very acutely pointed at apex; apical sclerotized area subtriangular. Endophallus (Fig. 97E) with copulatory tube having basal chamber almost ovoidal, maintube baculiform, long, moderately thick, with a short, thin apicomedian process (Fig. 97D);
expulsion hooks (Fig. 97H) broadly connected each other by a submembrane before the middleof the mesial margins of posterior plates, each hook with anterior plate incompletely separated
from posterior plate, subtriangular, broad at base, pointed at anterior tip, posterior plate broad atbase, almost pointed at posterior tip; ventromedian bands slightly short, very thin. Parameres(Fig. 97E) each very acutely pointed at apex; apical area very long, mesially with 11 setae of various length.
Female: Eighth ventrite almost rounded posteriorly; gonocoxites (Fig. 97F) each with apicolateral tooth very long, acute, apicolateral setae very long. Spermatheca (Fig. 97A) with capsule
moderately long; striped duct moderately long, thick; duct extremely long, very thin to thin forthe most part, with its anterior mass very tightly coiled; basal valve moderately long, thin; basal
duct long; basal pouch broad-subconical in shape.
Biology and ecology. The beetles of S. ichihashii inhabit leaf litter heaped in the natural forests of lowlands to mountainous regions.
Remarks. S. ichihashii miunensis was newly described as the subspecies of S. ichihashii,
based on one specimen of male beetle collected from the same locality (Mie Pref.) as that ofnominotypical subspecies in Naomi (2006). This is mainly based on the small, morphologicaldiﬀerences between them regarding the shapes of the anterior and posterior plates of endophallic
expulsion hooks, etc. However, since it was clariﬁed that these diﬀerences can be regarded as

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Fig. 98. Stenus mikawanis Naomi (Aichi: Mennoki). A, 6th and 7th ventrites of male; B, part of 9th ventrite ofmale; C, copulatory tube; D, aedeagus; E, endophallic expulsion hooks; F, posterior part of 8th ventrite of
male. Scale 1: 0.25 mm for A; scale 2: 0.05 mm for B, 0.2 mm for D, 0.1 mm for C, E; scale 3: 0.25 mm for F.

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225

infraspeciﬁc variations in the present study, S. ichihashii miunensis Naomi, 2006 is newly placedin synonym with S. ichihashii Naomi, 2006.
S. ichihashii is allied to S. lubomiri, but it is separable from the latter species by the copulatory tube thicker (Fig. 97D), and the endophallic expulsion hook with its anterior plate broader at
the anterior part and hardly protruding laterally or posterolaterally at the posterolateral corner
and its posterior plate broader at base (Fig. 97H).
Etymology. This species is named after the late Mr. Hajimu Ichihashi (Mie) who contributed
to the clariﬁcation of Stenus fauna of Mie Pref., Honshu.
Stenus mikawanis Naomi(Figs. 98A–F, 134K)
Stenus nakanei mikawanis Naomi, 1997b: 606; Herman, 2001: 2295.
Stenus mikawanis Naomi, 2006: 70; Naomi & Puthz, 2013: 145.
Type material examined. Holotype: ♂ (CBM), Mennoki Pass, Aichi Pref., 13. viii. 1990, S.
Nomura leg.
Other material examined. [HONSHU]: 1 ♂, Ena Shrine, Gifu Pref., 18. vi. 2014, T. Ito leg.
Distribution. Japan: Honshu (Aichi and Gifu Prefs.).
Redescription. Male: Body 3.8 mm (fore body 1.9 mm) in length. Body moderately shining;head dark reddish brown, with lateral parts of interocular area infuscate; pronotum and elytra
reddish brown; abdomen dark reddish brown, with apical segments infuscate; labrum reddish
orange; antennae and legs yellow brown to reddish brown. Body with punctures round to ovoidal, small to moderately large, and also pronotum partially with coarse punctures and elytra partially with large, coarse punctures. Head moderately concave, with a pair of longitudinal-obliquefurrows; antennae moderately long, very thin; pronotum with surface almost smooth, with a
median longitudinal furrow hardly developed; elytra with surface slightly uneven; abdomen subcylindrical, slightly tapering posteriorly; lateroventrites and tergoventrite sutures lost.
Abdomen (Fig. 98A) modiﬁed with a ﬂat area on the 5th, a very shallow depression on the
6th, a moderately deep depression on the 7th, and a semicircular, moderately deep emarginationon the 8th ventrite (Fig. 98F); 9th tergum with ventral apophyses slightly short; 9th ventrite (Fig.
98B) with apicolateral teeth short, very acute; 10th tergum almost entire. Aedeagus (Fig. 98E)
with median lobe moderately narrowing apicad and very shallowly bisinuate laterally in the apical 1/2, very acutely pointed at apex; apical sclerotized area subpentagonal. Endophallus (Fig.
98D) with copulatory tube (Fig. 98C) long, very thick, submembranous and moderately swollen
laterally at the subapical portion, with a very short, apicomedian process which becomes slightly
broader apicad; expulsion hooks (Fig. 98E) broadly contiguous behind the middle of the mesial
margins of posterior plates, each hook with anterior plate subtriangular, broad at base, minutely
hooked at anterior tip, posterior plate elongate, narrowly rounded at posterior tip; ventromedianbands moderately long, moderately broad. Parameres (Fig. 98D) each very acutely pointed atapex; apical area long, mesially with 14 to 15 setae of various length.
Female: Unknown.
Biology and ecology. The beetles of S. mikawanis inhabit leaf litter heaped in the natural forests of mountainous regions.
Remarks. S. mikawanis was ﬁrst described as a subspecies of S. nakanei in Naomi (1997b).
S. mikawanis is treated as a species in Naomi & Puthz (2013) and the present study because it is226

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Fig. 99. Stenus gyrosus Naomi (Aichi: Kaijyo). A, spermatheca; B, aedeagus; C, copulatory tube; D, 9th ventriteof male; E, gonocoxite; F, 6th and 7th ventrites of male; G, posterior part of 8th ventrite of male; H, endophallic expulsion hooks. Scale 1: 0.1 mm for A, C, E, H, 0.2 mm for B, D; scale 2: 0.25 mm for F; scale 3: 0.25 mm
for G.

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227

distinctly diﬀerent from S. nakanei in the very large endophallic copulatory tube with its swollen
submembranous subapical portion (Fig. 98C), etc.
S. mikawanis is allied to S. ichihashii, but it is separable from the latter species by the copulatory tube much thicker, with its subapical portion moderately swollen laterally and submembranous (Fig. 98C), and the endophallic expulsion hook with its anterior plate minutely hooked at
the anterior tip and its posterior plate elongate and narrowly rounded at the posterior tip (Fig.
98E).
Stenus gyrosus Naomi(Fig. 99A–H)
Stenus wasabi Hromádka: Naomi, 1997b: 603 (in part).
Stenus gyrosus Naomi, 2006: 72.
Type material examined. Holotype: ♂ (CBM), Kaijyo, Seto City, Aichi Pref., 8. xi. 1992, T.
Hozumi leg. Paratype: 1 ♀, same data as holotype.
Other material examined. [HONSHU]: 1 ♂, Mt. Sanage, Aichi Pref., 14. ii. 1999, T. Kanleg.; 1 ♂1 ♀, Okazaki, Aichi Pref., 26. xii. 2007, K. Ito leg.
Distribution. Japan: Honshu (Aichi Pref.).
Redescription. Male and female: Body 3.8–4.1 mm (fore body 1.8–2.0 mm) in length. Body
weakly to moderately shining and almost entirely reddish brown except for the infuscate lateralparts of interocular area; labrum reddish orange; antennae and legs yellow brown to reddish
brown. Body with punctures round to elliptical, small to moderately large, and also pronotum
partially with subrugose punctures and elytra partially with large, coarse punctures. Head moderately concave, with a pair of almost longitudinal depressions; antennae short to moderately long,very thin; pronotum with surface slightly uneven to uneven, with a median longitudinal furrow
very indistinct to indistinct; elytra with surface slightly uneven to uneven; abdomen subcylindrical, slightly tapering posteriorly to subparallel-sided; lateroventrites and tergoventrite sutures
lost.
Male: Abdomen (Fig. 99F) modiﬁed with a ﬂat area on the 5th, a shallow depression on the
6th, a moderately deep depression on the 7th, and a semicircular, moderately deep emarginationon the 8th ventrite (Fig. 99G); 9th tergum with ventral apophyses slightly short; 9th ventrite (Fig.
99B) with macrosetae very short, apicolateral teeth very short, acute; 10th tergum very shallowly
emarginate posteromedially. Aedeagus (Fig. 99B) with median lobe moderately narrowing
apicad and very shallowly bisinuate laterally in the apical 1/2, very acutely pointed at apex; apical sclerotized area subtriangular. Endophallus (Fig. 99B) with copulatory tube (Fig. 99C) moderately long, moderately thick, moderately swollen laterally at the subapical portion, with a moderately long, very thin apicomedian process; expulsion hooks (Figs. 99H) each with anterior
plate elongate-subtriangular in shape, moderately broad at base, minutely hooked at anterior tip,
posterior plate slender, very thin, moderately curved in the middle; ventromedian bands moderately long, moderately broad. Parameres (Fig. 99B) each very acutely pointed at apex; apicalarea long, mesially with 13 to 14 moderately long setae.
Female: Eighth ventrite almost rounded posteriorly or obtuse posteromedially; gonocoxites(Fig. 99F) each with apicolateral tooth long, acute, apicolateral setae long. Spermatheca (Fig.
99A) with capsule moderately long, very thick, much rounded apically; striped duct slightly
short, thick; duct long, moderately thick to thick, with its anterior mass moderately coiled; basal

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valve short; basal duct short.
Biology and ecology. The beetles of S. gyrosus inhabit leaf litter heaped in the natural forestsof lowlands to low mountainous regions.
Remarks. S. gyrosus is allied to S. nakanei and S. awajinis, but it is separable from the latter2 species by the 7th ventrite of male with its posteromedian depression smaller (Fig. 99F), theaedeagal median lobe thinner (Fig. 99B), the copulatory tube thinner (Fig. 99C), the endophallic
expultion hook with its posterior plate thinner at the base (Fig. 99H), and the spermatheca withits basal duct shorter (Fig. 99A).
Stenus nakanei Hromádka(Figs. 100A–H, 134 L)
Stenus nakanei Hromádka, 1982: 132; Herman, 2001: 2295; Naomi & Puthz, 2013: 145.
Stenus ignorabilis Naomi, 1997b: 607; Naomi, 2006: 75 (synonym of S. nakanei).
Type material examined. Holotype of S. nakanei: ♂ (NMP), Asuka, Nara Pref., 1. ix. 1963,
K. Sawada leg.
Holotype of S. ignorabilis: ♂ (CBM), Mt. Kôtsu, Tokushima Pref., 30. iv. 1972, M. Yoshidaleg. Paratypes of S. ignorabilis: 1 ♀, Mt. Shibakoya, Kamiyama-cho, Tokushima Pref., 2. x.
1977, M. Yoshida leg.; 1 ♀, same locality, 6. iv. 1976, M. Yoshida leg.; 1 ♂1 ♀, same locality, 6.
iv. 1975, M. Yoshida leg.; 1 ♂, Mt. Kumoso (1150 m), Tokushima Pref., 18. vii. 1988, M. Sakai
leg.; 2 ♂, Okuohno, Ichiu-son, Mima, Tokushima Pref., 1. viii. 1967, M. Yoshida leg.; 1 ♂, Mt.
Nakatsu, Nishiiyayama-son, Tokushima Pref., 23. viii. 1971, M. Yoshida leg.; 1 ♂, Mt. Kurotaki,
Yamashiro-cho, Tokushima Pref., 3. viii. 1977, M. Yoshida leg.; 2 ♂, Harunokio, Nishiiyayamason, Tokushima Pref., 24. viii. 1971, M. Yoshida leg.; 1 ♂2 ♀, Yusuhara-cho, Takaoka-gun, Kochi
Pref., 30. iv. 1977, M. Yoshida leg.; 1 ♂1 ♀, Izumi, Niyodo-mura, Kochi Pref., 20. iii. 1976, M.
Yoshida leg.; 1 ♂, Mt. Zôzu, Kagawa Pref., 24. i. 1971, T. Kinoshita leg.
Other material examined. [HONSHU]: 2 ♂1 ♀, Mt. Makio, Osaka Pref., 17. iv. 1960, Y.
Kimura leg.; 1 ♂, Mt. Kongô, Osaka Pref., 10. viii. 1986, T. Ito leg.; 2 ♂2 ♀, Mt. Inunaki, Osaka
Pref., 27. vii. 1985, T. Ito leg.; 1 ♂, Mt. Iwawaki, Osaka Pref., 5. vi. 1960, T. Ito leg.; 3 ♂, Mt.
Iwawaki, Osaka Pref., 24. iv. 1966, Y. Hayashi leg.; 5 ♂5 ♀, Kimi Pass, Wakayama Pref., 17. iv.
1988, T. Ito leg.; 7 ♂6 ♀, Tamagawa-kyo, Wakayama Pref., 24. viii. 1985, T. Ito leg.; 1 ♂, Hase,
Yamato, 14. iv. 1959, T. Shibata leg.; 2 ♂, Murooji, Nara Pref., 10. x. 1984, T. Ito leg.; 1 ♂,Imoyama, Yamato, 15. ix. 1984, T. Ito leg.; 2 ♂7 ♀, Mt. Toonomine, Yamato, 13. viii. 1984, T. Itoleg. [SHIKOKU]: 1 ♂1 ♀, Okuyashiki (600 m), Awa (Tokushima Pref.), 6. i. 1960, T. Shibata
leg.; 2 ♂3 ♀, Tonyo, Tomisato, Iyomishima City, Ehime Pref., 16. xi. 1999, S. Nomura leg.
Distribution. Japan: Honshu (Nara, Osaka and Wakayama Prefs.) and Shikoku.
Redescription. Male and female: Body 3.8–4.0 mm (fore body 1.9–2.1 mm) in length, moderately shining; head dark red near black to black, with clypeofrontal area reddish brown to dark
red; pronotum and elytra reddish brown to almost brown; abdomen dark reddish brown to darkbrown, with apical segments more or less infuscate; labrum yellowish brown to reddish brown;
antennae and legs yellowish brown to reddish brown. Body with punctures round to elliptical,
small to moderately large, and also pronotum partially with subrugose punctures and elytra partially with large, subrugose punctures. Head moderately concave, with a pair of longitudinaloblique furrows; antennae short, very thin; pronotum with surface uneven, with a median longitudinal furrow indistinct; elytra with surface uneven; abdomen subcylindrical, slightly tapering

The Steninae of Japan Part 3229

Fig. 100. Stenus nakanei Naomi (Tokushima, A, G, Shibakoya; Nara, B, C, E, H, Mt. Toonomine; Wakayama, D,
Tamagawa-kyo; Kochi, F, Yusuhara, Kochi). A, spermatheca; B, aedeagus; C, copulatory tube; D, 9th ventriteof male; E, endophallic expulsion hooks; F, 6th and 7th ventrites of male; G, gonocoxite; H, posterior part of
8th ventrite of male. Scale 1: 0.1 mm for A, C, E, G, 0.2 mm for B, D; scale 2: 0.25 mm for F; scale 3: 0.25 mm
for H.

posteriorly to subparallel-sided; lateroventrites and tergoventrite sutures lost.
Male: Abdomen (Fig. 100F) modiﬁed with a ﬂat area on the 4th, a very shallow or a shallow
depression on the 5th, a shallow or a moderately deep depression on the 6th, a very broad, very
shallow anteromedian depression and with a deep or a very deep posteromedian depression on

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the 7th, a subtriangular, deep emargination on the 8th ventrite (Fig. 100H); 9th tergum with ventral apophyses long; 9th ventrite (Fig. 100D) with macrosetae short, apicolateral teeth very short,acute, apicolateral setae moderately long; 10th tergum very shallowly emarginate posteromedially. Aedeagus (Fig. 100B) with median lobe strongly narrowing apicad and very shallowly
bisinuate laterally in the apical 1/2, very acutely pointed at apex; apical sclerotized area elongatesubtriangular in shape. Endophallus (Fig. 100B) with copulatory tube (Fig. 100C) moderately
long, very thick, moderately swollen laterally at the subapical portion, with an almost beakshaped process at apex; expulsion hooks (Fig. 100E) each with anterior plate small, almost triangular, posterior plate moderately broad at base, thin behind the basal 1/3, moderately curved in
the middle; ventromedian bands slightly short, moderately broad. Parameres (Fig. 100B) eachvery acutely pointed at apex; apical area very long, ventromesially with a medium-sized, broadtriangular ﬂap at base, mesially with 21 to 22 moderately long setae.
Female: Eighth ventrite obtuse posteromedially; gonocoxites (Fig. 100G) each with apicolateral tooth long, very acute, apicolateral setae very long. Spermatheca (Fig. 100A) with capsule
moderately long, much rounded apically; striped duct moderately long, very thick; duct moderately long, becoming broader distad from thin through moderately thick to thick; basal valve
moderately long; basal duct extremely large, well-sclerotized, swollen laterally at base.
Biology and ecology. S. nakanei is distributed in Honshu (Kinki District) and Shikoku. Thisshows that S. nakanei is one of the species whose distributional range is very wide among thespecies of cephalotes-group. The beetles of S. nakanei inhabit leaf litter heaped in the natural forests of lowlands to mountainous regions.
Remarks. S. nakanei is closely allied to S. awajinis, but it is separable from the latter species
by the 7th ventrite of male with its depression shallower (Fig. 100F), the aedeagal median lobe
with its apical sclerotized area elongate-subtriangular in shape (Fig. 100B), the endophallic
expulsion hook with its anterior plate larger (Fig. 100E), and the spermatheca with its basal tube
much thicker (Fig. 100A).
Etymology. The speciﬁc epithet of this species is named after the late Dr. Takehiko Nakane(National Science Museum, Tokyo) who contributed to the development of the taxonomy of Japanese Coleoptera.
Stenus awajinis Naomi stat. nov.
(Fig. 101A–I)
Stenus ignorabilis awajinis Naomi, 1997b: 609.
Stenus nakanei awajinis (Naomi), 2006: 77.
Type material examined. Holotype: ♂ (CBM), Mt. Senzan, Sumoto, Awaji Is., Hyogo Pref.,15. iv. 1971, M. Tomokuni leg.
Other material examined. [HONSHU]: 2 ♂1 ♀, Mt. Sakiyama, Awaji Is., Hyogo Pref., 21. ii.
2010, K. Mizuno leg.; 1 ♂1 ♀, Mt. Jyoryuji, Awaji Is., Hyogo Pref., 21. vii. 2017, T. Ito leg.
Distribution. Japan: Honshu (Hyogo Pref.: Awaji Is.).
Redescription. Male and female: Body 3.7–3.9 mm (fore body 1.8–2.0 mm) in length. Body
moderately shining; head reddish orange to reddish brown, with lateral parts of interocular area
infuscate; pronotum and elytra reddish orange to reddish brown; abdomen reddish brown toalmost brown, with apical segments more or less infuscate; labrum yellowish brown to reddish
brown; antennae and legs yellowish brown to reddish brown. Body with punctures round to ovoi-

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Fig. 101. Stenus awajinis Naomi (Hyogo, Awaji Is.: A–D, F, H, I, Sumoto; E, Mt. Sakiyama; G, Mt. Jyoryuji). A,
9th and 10th terga of male; B, aedeagus; C, 9th ventrite of male; D, copulatory tube; E, spermatheca; F, 6th
and 7th ventrites of male; G, posterior part of gonocoxite; H, posterior part of 8th ventrite of male; I, endophallic expulsion hooks. Scale 1: 0.2 mm for A–C, H, 0.1 mm for D, E, G, I; scale 2: 0.25 mm for F.

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dal, small to moderately large, and also pronotum and elytra partially with coarse to subrugose
punctures. Head shallowly to moderately concave, with a pair of longitudinal-oblique or mesially-curved furrows (or depressions); antennae short to moderately long, very thin; pronotumwith surface slightly uneven to uneven, with a median longitudinal furrow indistinct; elytra withsurface uneven; abdomen subcylindrical, slightly tapering posteriorly; lateroventrites and tergoventrite sutures lost.
Male: Abdomen (Fig. 101F) modiﬁed with an almost ﬂat area on the 4th, a shallow depression on the 5th, a deep depression on the 6th, and a very deep depression on the 7th, and a subtriangular, very deep emargination on the 8th ventrite (Fig. 101H); 9th tergum (Fig. 101A) withventral apophyses long; 9th ventrite (Fig. 101C) with apicolateral teeth very short, very acute,apicolateral setae moderately long; 10th tergum (Fig. 101A) shallowly emarginate posteromedially. Aedeagus (Fig. 101B) with median lobe moderately narrowing apicad and moderately bisinuate laterally in the apical 3/5, very acutely pointed at apex; apical sclerotized area subpentagonal. Endophallus (Fig. 101B) with copulatory tube (Fig. 101D) moderately long, having basal
chamber very long, moderately narrowing apically, with its apical portion located inside the baseof main tube, main tube very thick, moderately swollen laterally at the subapical portion, with anearly beak-shaped process at apex; expulsion hooks (Figs. 101I) each with anterior plate small,almost triangular, posterior plate moderately broad at base, thin behind the base; ventromedianbands short, narrow. Parameres (Fig. 101B) each very acutely pointed at apex; apical area long,ventromesially with a small, broad-triangular ﬂap at base, mesially with 16 moderately longsetae.
Female: Eighth ventrite obtuse posteromedially; gonocoxites (Fig. 101G) each with apicolateral tooth moderately long, very acute, apicolateral setae very long. Spermatheca (Fig. 101E)
with capsule short, narrowly rounded apically; striped duct very long, thin to moderately thick;duct moderately long, thin, very loosely coiled; basal valve very short; basal duct extremely
long, very thin.
Biology and ecology. The beetles of S. awajinis inhabit leaf litter heaped in the natural forests of low mountainous to mountainous regions.
Remarks. Based on one specimen of male beetle collected from Mt. Senza, Awaji Is., Naomi(1997b) ﬁrst newly described S. ignorabilis awajinis as a subspecies of S. ignorabilis Naomi,
1997. After that, S. ignorabilis was treated as a junior synonym of S. nakanei Hromádka, 1982 in
Naomi (2006), and thus he changed its name to S. nakanei awajinis (Naomi). When reconsidering here again the diﬀerences between this subspecies (S. nakanei awajinis) and the nominotypical subspecies (S. nakanei nakanei) mentioned below, S. nakanei awajinis is upgraded to a species, and S. awajinis Naomi stat. nov. is here proposed.
S. awajinis is closely allied to S. nakanei, but it is separable from the latter species by the 7th
ventrite of male with its depression deeper (Fig. 101F), the aedeagal median lobe with its apicalsclerotized area subpentagonal (Fig. 101B), the endophallic expulsion hook with its anterior platesmaller (Fig. 101I), and the spermatheca with its basal tube much thinner (Fig. 101E).
Species unit 3 of the rufescens-subgroup
Key to the Japanese species of the rufescens-subgroup (3)This is a key for a unit of Stenus-species (19 species) beginning with S. testaceopiceus andprobably diagnosed with the combination of following character conditions: Aedeagal median

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lobe often more or less narrowed near or behind the middle so that the basal part and apical partare distinguished from each other by their diﬀerent thickness (Fig. 115C); endophallic expulsion
hooks very often strongly atrophied into such various conditions as a small fused hook (Fig.
117B), a pair of very small, very thin sclerites (Fig. 119B), etc., or completely lost (Fig. 120C);
ventromedian bands often atrophied to some degree (Fig. 108F); paramere with apical area very
often more or less turning posterolaterally, moderately thick to thick, and more or less swollen
mesially at base (Fig. 112B).
Distribution. Japan: Honshu (Kanto, Chubu, Kinki and Chugoku Districts) and Shikoku.
1(12)
2(7)
3(6)
4(5)

Male: Endophallic expulsion hooks and ventromedian bands both well-developed.
Male: Aedeagal paramere with ventral margin of apical area not bisinuous.
Male: Aedeagal median lobe broader; paramere not mesially curved apically.
Male: Seventh ventrite with posteromedian depression more deeply emarginate posteriorly (Fig. 102F); aedeagal median lobe with apical sclerotized area almost triangular,
without apicomedian cusp (Fig. 102A).................................... S. testaceopiceus Bernhauer
5(4) Male: Seventh ventrite with posteromedian depression more shallowly emarginate posteriorly (Fig. 103A); aedeagal median lobe with apical sclerotized area subpentagonal or
broad-subtriangular in shape, with an apicomedian cusp (Fig. 103G) .................................
.............................................................................................................. S. pubicornis Naomi
6(3) Male: Aedeagal median lobe narrower (Fig. 104C); paramere mesially curved at the mostapical part (Fig. 104C) ............................................................................... S. volkeri Naomi
7(2) Male: Aedeagal paramere with ventral margin of apical area more or less bisinuous.
8(11) Male: Seventh ventrite with posteromedian depression more or less emarginate posteriorly; aedeagal median lobe becoming narrower from near the middle toward apicolateralcorners.
9(10) Male: Seventh ventrite with posteromedian depression shallower (Fig. 105C); endophallic expulsion hook with anterior plate turning anteriorly (Fig. 105G) ..................................
.............................................................................................. S. okiensis Naomi & Shimada
10(9) Male: Seventh ventrite with posteromedian depression deeper (Fig. 106E); endophallic
expulsion hook with anterior plate turning anterolaterally (Fig. 106H) ...............................
............................................................................................................... S. tsurusakii Naomi
11(8) Male: Seventh ventrite with posteromedian depression weakly arcuately rounded posteriorly (Fig. 107C); aedeagal median lobe awl-shaped in the apical 1/3 (Fig. 107C) ..............
........................................................................................................... S. akojagai Hromádka
12(1) Male: Endophallic expulsion hooks and/or ventromedian bands more or less atrophied orcompletely lost.
13(14) Male: Aedeagal expulsion hook well-developed, broad-bean-shaped (Fig. 108F); copulatory tube with main tube needle-shaped (Fig. 108F) ............................... ..S. miroku Naomi
14(13) Male: Aedeagal expulsion hook more or less atrophied; copulatory tube with main tube
not needle-shaped.
15(32) Male: Copulatory tube with main tube not having a pair of lateral processes at the base of
apical tube.
16(27) Male: Aedeagal median lobe narrower in posterior part; copulatory tube shorter than 7/10
times as long as median lobe.
17(26) Male: Copulatory tube with main tube well-developed. Female: Spermatheca with duct
thicker.

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18(25) Male: Aedeagal paramere with apical area shorter than pedicel.
19(24) Male: Fourth to 6th ventrites less strongly modiﬁed with ﬂat area and/or shallower
depression, or not modiﬁed with them.
20(23) Male: Copulatory with main tube slightly thick at or near base, and more or less attenuate
apicad.
21(22) Male: Aedeagal median lobe with apical sclerotized area broader, and pointed at apex
(Fig. 109A); paramere very acutely pointed at apex (Fig. 109A) .........................................
............................................................................................S. masatakai Naomi & Nomura
22(21) Male: Aedeagal median lobe with apical sclerotized area narrower, and narrowly roundedapically (Fig. 110A); paramere narrowly rounded apically (Fig. 110A) ..............................
...........................................................................................................S. gagyumontis Naomi
23(20) Male: Copulatory tube with main tube subfusiform or nearly willow-leaf-shaped (Fig.
115G) ......................................................................................... S. uenoi Naomi & Nomura
24(19) Male: Fourth to 6th ventrites more strongly modiﬁed with deeper depressions (Fig. 114A)........................................................................................................................S enma Naomi
25(18) Male: Aedeagal paramere with apical area longer than pedicel (Fig. 117D) ........................
..............................................................................................S. masaakii Naomi & Nomura
26(17) Male: Copulatory tube with main tube strongly atrophied into a small, spine-like sclerite(Fig. 116E). Female: Spermatheca with duct thinner (Fig. 116C) ........................................
...................................................................................................... S. expansus Naomi & Ito
27(16) Male: Aedeagal median lobe broader in posterior part; copulatory tube longer than 4/5
times as long as the median lobe.
28(31) Male: Aedeagal median lobe moderately broad, and not incised at apicomedian part; copulatory tube with main tube not swollen laterally near the middle.
29(30) Male: Aedeagal median lobe obtusely angulate at apicolateral corners, with apical triangular part behind apicolateral corners not forming an obtuse triangular and hardly emarginate apicolaterally (Fig. 111D); endophallic ventromedian band narrower (Fig. 111C) ...
............................................................................................ S. incurvatus Naomi & Nomura
30(29) Male: Aedeagal median lobe almost rectangularly angulate at apicolateral corners, withapical triangular part behind apicolateral corners forming an obtuse broad-subtriangularand arcuately emarginate apicolaterally (Fig. 112B); endophallic ventromedian bandbroader (Fig. 112B) ................................................................................ S. okamotoi Naomi
31(28) Male: Aedeagal median lobe moderately broad, and very minutely incised at apicomedianpart (Fig. 113B); copulatory tube with main tube moderately swollen laterally near the
middle (Fig. 113B) .................................................................... S. amma Naomi & Nomura
32(15) Male: Copulatory tube with main tube having a pair of lateral processes at the base of
apical tube.
33(36) Male: Aedeagal median lobe with apical sclerotized area extremely small or lost.
34(35) Male: Aedeagal median lobe narrower, and becoming almost constantly broader frombase to about apical 1/3 (Fig. 118B); copulatory tube with apical tube having a pair ofvery thin, slightly curved lateral processes (Fig. 118E) ............................ S. bosatsu Naomi
35(34) Male: Aedeagal median lobe broader, and bulbous in about basal 2/3 (Fig. 120C); copulatory tube with apical tube having a pair of thin, strongly curved lateral processes (Fig.
120C)............................................................. S. tateoitoi Naomi, Nomura & Puthz sp. nov.
36(33) Male: Aedeagal median lobe with apical sclerotized area well-developed (elongate-triangular in shape) (Fig. 119B) .....................................................S. usitatus Naomi & Nomura

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Stenus testaceopiceus Bernhauer(Figs. 102A–G, 135A)
Stenus testaceopiceus Bernhauer, 1938: 31; Herman, 2001: 2417; Naomi & Puthz, 2013: 145.
Type material examined. Holotype: ♂ (FMC), Chinkiang, Northwestern China, Col. Reitter;S. testaceopiceus Bernh. Typus unic.; Chicago NHMus. M. Bernhauer Collection.
Other material examined. [HONSHU]: 8 ♂4 ♀, Mizuho, Kyoto, 23. xi. 1989, T. Ito leg.;3 ♂3 ♀, same locality, 2. vii. 1989, T. Ito leg.; 1 ♂, same locality, 26. viii. 1989, Y. Hayashi leg.;1 ♂, same locality, 23. xi. 1989, Y. Hayashi leg.; 1 ♂, same locality, 23. iv. 1994, Y. Hayashi leg.;2 ♀, same locality, 18. iv. 1987, Y. Hayashi leg.; 2 ♂1 ♀, same locality, 14. v. 1994, Y. Hayashi
leg.; 1 ♂, same locality, 12. v. 1984, Y. Hayashi leg.; 1 ♂1 ♀, Todoromi; 1 ♂4 ♀, Mt. Myôken,Nose, Ohsaka Pref., 25. ix. 1994, T. Ito leg.; 6 ♂8 ♀, same locality, 30. viii. 1986, T. Ito leg.; 1 ♀,same locality, 13. viii. 1985, T. Ito leg.; 2 ♂2 ♀, same locality, 16. v. 1987, T. Ito leg.; 2 ♂4 ♀, Mt.
Mikusa, Osaka Pref., 19. iii. 1993, Y. Sawada leg.; 1 ♂4 ♀, Mt. Shosha, Hyogo Pref., 19. iii.
1988, T. Ito leg.; 1 ♂3 ♀, Mt. Amaishi, Sasayama, Hyogo Pref., 19. iv. 1997, Y. Hayashi leg.;2 ♂1 ♀, Higashi-Rokko, Hyogo Pref., 4. iv. 1987, T. Ito leg.
Distribution. Japan: Honshu (Kyoto, Osaka and Hyogo Prefs.) and China?
Redescription. Male and female: Body 3.2–3.8 mm (fore body 1.6–1.9 mm) in length. Body
weakly shining; head dark brown to black, with median area reddish brown to dark red; pronotum and elytra reddish brown; abdomen reddish brown to dark reddish brown; labrum, antennae
and legs yellowish brown to reddish brown. Body with punctures round to ovoidal, small tomoderately large, and also pronotum partially with subrugose punctures and elytra partially withlarge, subrugose punctures. Head moderately concave, with a pair of longitudinal-oblique or longitudinal furrows; antennae short to moderately long, very thin; pronotum with surface slightly
uneven to uneven, with a median longitudinal furrow indistinct; elytra with surface uneven;abdomen subcylindrical, moderately thick to thick, subparallel-sided; lateroventrites and tergoventral sutures lost.
Male: Abdomen (Fig. 102F) modiﬁed with a bell-shaped ﬂat area on the 5th, an almost semicircular, moderately deep posteromedian depression on the 6th, a shallow or moderately deep
anteromedian depression and a short, very deep posteromedian depression on the 7th, and a subtriangular, deep emargination on the 8th ventrite (Fig. 102G); 9th tergum with ventral apophyses
long to very long; 9th ventrite (Fig. 102C) with macrosetae short, apicolateral teeth short, acute,apicolateral setae moderately long; 10th tergum very shallowly emarginate posteromedially.
Aedeagus (Fig. 102A) with median lobe almost elongate-ovoidal in shape, minutely angulate atapicolateral corners, acutely pointed at apex; apical sclerotized area almost triangular. Endophallus (Fig. 102A) with copulatory tube with basal chamber elongate-ovoidal in shape, main tube
baculiform, attenuate, once moderately curved near the middle; dorsolateral bands very thin;
expulsion hooks (Fig. 102E) connected broadly by a membrane, each hook minutely curved
mesially at anterior tip and very acutely pointed there, distinctly emarginate at posterolateralpart; ventromedian bands each moderately long, very broad. Parameres (Fig. 102A) each acutely
pointed at apex; apical area long, mesially with 11 to 12 moderately long setae.
Female: Eighth ventrite obtuse posteromedially; gonocoxites (Fig. 102D) each with apicolateral tooth moderately long, acute, apicolateral setae very long. Spermatheca (Fig. 102B) with
capsule very small, rounded apically; striped duct moderately long, thick; duct very short, moderately thick to thick, with 2 turns; gland ovoidal, with opening located on the middle of duct

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Fig. 102. Stenus testaceopiceus Bernhauer (Osaka: Mt. Myôken). A, aedeagus; B, spermatheca; C, 9th ventrite ofmale; D, gonocoxite; E, endophallic expulstion hooks; F, 6th and 7th ventrites of male; G, posterior part of 8th
ventrite of male. Scale 1: 0.25 mm for F; scale 2: 0.25 mm for G; scale 3: 0.2 mm for A, C, 0.1 mm for B, D, E.

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between the 1st and 2nd turns; basal valve short; basal duct long. Bursa copulatrix (Fig. 102B)
large, subconical.
Biology and ecology. The beetles of S. testaceopiceus inhabit leaf litter heaped in the naturalforests of plains to low mountainous regions.
Remarks. S. testaceopiceus is allied to S. pubicornis, but it is separable from the latter species by the aedeagal median lobe minutely angulate at the apicolateral corners, almost acutely
pointed at the apex (Fig. 102A), the endophallic expulsion hook broader, with its anterior tip
mesially curved and very acutely pointed (Fig. 102E), and the spermatheca with its duct much
shorter with 2 turns (Fig. 102B).
S. testaceopiceus was ﬁrst described by Bernhauer (1938), based only on the 1 specimen of
male beetle collected from the Northwestern part of China. Although Puthz (1968) synonymized
this species with S. rufescens, Hromádka (1982) revalidated it as a good species. Naomi examined the holotype of S. testaceopiceus deposited in the Field Meseum, Chicago, and he concluded that the holotype of S. testaceopiceus is exactly the same both in external and aedeagal
structures as the specimens from Japan (Naomi, 2006). Thus, if taken it literally, the distributional range of S. rufescens extends from the Japanese Archipelago to the China Mainland. Sincesuch a distributional range is too wide for a ﬂightless species in Stenus, we here discuss the distribution of this species.
During the present study we examined 71 specimens of S. testaceopiceus from Japan. All ofthese Stenus-beetles were collected strictly from the western part of Kansai District, Honshu.
Thus, as far as the distributional range of this species within Japan is taken into account, it must
be a common size of distributional range as in most of the other brachypterous and thus ﬂightless
species of the cephalotes-group. The northwestern China, the type locality of S. testaceopiceus,
is at least 2,000 km distant from the Kinki District, Honshu. When considering the ﬂightless condition of this species, such a disjunct distribution of a species does not seem to be natural.
Although we do not deny a possibility that the Northwestern part of China is a part of original
distributional range of S. testaceopiceus, the inclusion of the Northwestern part of China in the
distributional range of S. testaceopiceus should be suspended in this paper until further beetles ofS. testaceopiceus are collected from there.
Stenus pubicornis Naomi(Fig. 103A–H)
Stenus pubicornis Naomi, 1998a: 387; Herman, 2001: 2357; Naomi & Puthz, 2013: 145.
Type material examined. Holotype: ♂ (CBM), Reiganji, Hirogawa-cho, Wakayama Pref., 11.
xii. 1985, I. Matoba leg. Paratypes: 1 ♂2 ♀, same data as holotype.
Distribution. Japan: Honshu (Wakayama Pref.).
Redescription. Male and female: Body 3.4–3.9 mm (fore body 1.7–2.0 mm) in length. Body
moderately shining; head dark red near black to almost black, with median area reddish brown todark red; pronotum and elytra reddish orange to reddish brown; abdomen reddish brown; labrum,
antennae and legs yellowish brown to reddish brown. Body with punctures round to almost
round, small to moderately large, and also pronotum partially with subrugose punctures and elytra partially with large, subrugose punctures. Head moderately concave, with a pair of almost
longitudinal-oblique or mesially-curved furrows (or depressions); antennae moderately long,very thin; pronotum with surface slightly uneven to uneven, with a median longitudinal furrow

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Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

Fig. 103. Stenus pubicornis Naomi (Wakayama: Reiganji). A, 6th and 7th ventrites of male; B, gonocoxite; C, 9th
ventrite of male; D, posterior part of 8th ventrite of male; E, endophallic expulsion hooks; F, 9th and 10th
terga of male; G, aedeagus; H, spermatheca. Scale 1: 0.25 mm for A; scale 2: 0.25 mm for D; scale 3: 0.1 mm
for B, E, H, 0.2 mm for C, F, G.

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239

distinct; elytra with surface slightly uneven to uneven; abdomen subcylindrical, moderately
thick, subparallel-sided; lateroventrites and tergoventral sutures lost.
Male: Abdomen (Fig. 103A) modiﬁed with a ﬂat area on each of the 3rd, 4th and 5th, a large,
deep depression on the 6th, a very large, very deep depression on the 7th ventrite (Fig. 103D);
9th tergum (Fig. 103F) with ventral apophyses very long; 9th ventrite (Fig. 103C) with apicolateral teeth short, acute, apicolateral setae moderately long; 10th tergum (Fig. 103F) shallowly
emarginate posteromedially. Aedeagus (Fig. 103G) with median lobe obtusely angulate at apicolateral corners, very acutely pointed at apex, with a long apicomedian cusp; apical sclerotizedarea subpentagonal or broad-subtriangular in shape. Endophallus (Fig. 103G) with copulatory
tube long, baculiform, stout, with basal chamber narrow, comprising 2 thick rods of equal length,
main tube thick, weakly, partially sinuous, pointed at apex; expulsion hooks (Fig. 103E) eacharcuately emarginate at posterolateral part, obtusely pointed at anterior tip; ventromedian bands
slightly short, moderately broad. Parameres (Fig. 103G) each very acutely pointed at apex; apicalarea long, moderately swollen mesially in the basal 2/3, then strongly narrowing toward aciculate
apex, mesially also with 15 to 16 setae.
Female: Eighth ventrite obtusely angulate or pointed posteromedially; gonocoxites (Fig.
103B) each with apicolateral tooth long, acute, apicolateral setae long. Spermatheca (Fig. 103H)
with capsule thick; striped duct moderately long, thick; duct long, irregularly coiled; basal valve
very short thin; basal duct short, well-sclerotized.
Biology and ecology. The beetles of S. pubicornis inhabit leaf litter heaped in the natural forests of a lowland.
Remarks. S. pubicornis is allied to S. testaceopiceus, but it is separable from the latter species by the aedeagal median lobe obtusely angulate at the apicolateral corners, acutely pointed at
the apex with the long apicomedian cusp (Fig. 103G), the endophallic median hook narrower,with its anterior tip almost obtusely pointed (Fig. 103E), and the spermatheca with its duct much
longer and irregularly coiled many times (Fig. 103H).
S. pubicornis is diﬀerent at a glance in coloration from S. gonggashanus Tang & Puthz, 2010
from Sichuan Province, China, but when considering their common posession of the similar
structures of the aedeagal median lobe as well as the endophallic copulatory tube and expulsion
hooks, they are also considered to be closely allied species. S. pubicornis is separable from thelatter species by the pronotum and elytra paler in color, the aedeagal median lobe with a longer
apicomedian cusp (Fig. 103G), and the spermatheca with its duct much longer (Fig. 103H).
Stenus volkeri Naomi(Fig. 104A–G)
Stenus volkeri Naomi, 1998a: 385; Herman, 2001: 2435; Puthz & Naomi, 2013: 145.
Type material examined. Holotype: ♂ (CBM), Mt. Mikusa, Osaka Pref., 2. viii. 1989. Paratype: 1 ♀, same data as holotype.
Distribution. Japan: Honshu (Osaka Pref.).
Redescription. Male and female: Body 3.8–4.0 mm (fore body 1.8–1.9 mm) in length. Body
weakly shining; head almost black, with median area reddish brown to dark red near black; pronotum, elytra and abdomen reddish brown; labrum reddish orange; antennae and legs yellowish
brown to reddish brown. Body with punctures round to elliptical, small to moderately large, andalso pronotum partially with coarse to subrugose punctures and elytra partially with large, subru-

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Fig. 104. Stenus volkeri Naomi (Osaka: Mt. Mikusa). A, 9th ventrite of male; B, spermatheca; C, aedeagus; D,
6th and 7th ventrites of male; E, posterior part of 8th ventrite of male; F, gonocoxite; G, endophallic expulsion
hooks. Scale 1: 0.25 mm for D; scale 2: 0.25 mm for E; scale 3: 0.2 mm for A, C, 0.1 mm for B, F, G.

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241gose punctures. Head moderately concave, with a pair of longitudinal-oblique furrows; antennae
moderately long, very thin; pronotum with surface slightly uneven to uneven, with a medianlonigitudinal depression very indistinct; elytra with surface uneven; abdomen subcylindrical,
slightly tapering posteriorly; lateroventrites and tergoventral sutures lost.
Male: Abdomen (Fig. 104D) modiﬁed with a ﬂat area on each of the 3rd and 4th, a very shallow depression on the 5th, a deep depression on the 6th, a very deep depression on the 7th, andan almost triangular emargination on the 8th ventrite (Fig. 104E); 9th tergum with ventral apophyses very long; 9th ventrite (Fig. 104A) with macrosetae short, apicolateral teeth short, acute,apicolateral setae short; 10th tergum very shallowly emarginate posteromedially. Aedeagus (Fig.
104C) with median lobe very elongate, slightly narrowed a little before the middle, hardly angulate at apicolateral corners, acutely pointed at apex; apical sclerotized area elongate-triangular inshape. Endophallus (Fig. 104C) with copulatory tube long, robust, basal chamber ovoidal, maintube attenuate, distinctly bent near the middle; dorsolateral bands very thick; expulsion hooks(Fig. 104G) slightly small, each shoe-shaped; ventromedian bands moderately long, very broad.
Parameres each incurved and pointed at the most apical part; apical area long, moderately swollen mesially at base, mesially also with 8 to 9 short setae.
Female: Eighth ventrite almost rounded posteriorly; gonocoxites (Fig. 104F) each with apicolateral teeth long, very acute, apicolateral setae long to very long. Spermatheca (Fig. 104B)
with capsule small; striped duct moderately long, very thick; duct very short, thick with 2 turns;
gland with opening located on the middle of duct between the 1st and 2nd turns; basal valve very
short; basal duct robust, long, becoming broader proximad.
Biology and ecology. The beetles of S. volkeri inhabit leaf litter heaped in the natural forestsof a low mountainous region.
Remarks. S. volkeri is allied to S. testaceopiceus and S. pubicornis, but it is separable fromthe latter 2 species by the aedeagal median lobe much more elongate and slightly narrowed a little before the middle (Fig. 104C) and the endophallic expulsion hook shorter and strongly protruding laterally at the anterolateral part (Fig. 104G).
Etymology. This species is named after the third author of this paper, Volker Puthz
Stenus okiensis Naomi & Shimada(Figs. 105A–I, 135B)
Stenus okiensis Naomi & Shimada, 2008: 55; Naomi & Puthz, 2013: 144.
Type material examined. Holotype: ♂ (CBM), Washigamine (550 m), Fuse Vil., Dôgo Is.,
Shimane Pref., 25. iii. 2004, T. Shimada leg. Paratypes: 5 ♂5 ♀, same data as holotype; 2 ♂1 ♀,Saigo-cho, Ooku, Dôgo Is., Shimane Pref., 31. x. 2003, T. Shimada leg.; 1 ♀, Fuse-mura, Mt.
Daimanji (450 m), 1 Shimane Pref., 8. ix. 2003, T. Shimada leg.; 1 ♂1 ♀, Mt. Koshikibara(500 m), Saigô-cho, 10. v. 2003, T. Shimada leg.
Other material examined. [HONSHU]: 1 ♂1 ♀, Nakadani forest-road, Dôgo Is., Oki Isls.,
Shimane Pref., 9. xi. 2004, T. Watanabe leg.
Distribution. Japan: Honshu (Shimane Pref.: Dôgo Is.).
Redescription. Male and female: Body 3.9–4.1 mm (fore body 1.9–2.0 mm) in length. Headweakly shining; head black; pronotum and elytra dark red to dark brown; abdomen dark red todark brown or almost black; labrum dark red to almost black; antennae and legs reddish brown.
Body with punctures round to ovoidal, small to moderately large, and also pronotum partially242

Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

Fig. 105. Stenus okiensis Naomi & Shimada (Shimane, Oki Isls., Dôgo Is.: A–E, G, I, Nakadani Forest road; F,H, Mt. Koshikibara). A, 9th and 10th terga of male; B, 9th ventrite of male; C, 5th to 7th ventrites of male; D,posterior part of 8th ventrite of male; E, aedeagus; F, spermatheca; G, endophallic expulsion hooks; H, posterior part of gonocoxite; I, copulatory tube. Scale 1: 0.2 mm for A, B, D, E; 0.1 mm for F–I; scale 2: 0.25 mm
for C.

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with coarse to subrugose punctures and elytra partially with large, subrugose punctures. Headmoderately concave, with a pair of longitudinal-oblique or almost mesially-curved furrows;
antennae short to moderately long, very thin; pronotum with surface slightly uneven to uneven,with a median longitudinal furrow very indistinct to indistinct; elytra with surface uneven; abdomen subcylindrical, subparallel-sided; lateroventrites and tergoventral sutures lost.
Male: Abdomen (Fig. 105C) modiﬁed with a ﬂat area on the 5th, a shallow depression on the
6th, an elongate, shallow depression on the 7th, and a broad-subtriangular or almost semicircularemargination on the 8th ventrite (Fig. 105D); 9th tergum (Fig. 105A) with ventral apophyses
very long; 9th ventrite (Fig. 105B) with macrosetae very short, apicolateral teeth long, acute, apicolateral setae slightly short; 10th tergum (Fig. 105A) very shallowly emarginate posteriorly.
Aedeagus (Fig. 105E) with median lobe becoming distinctly narrower apicad, obtusely angulate
at apicolateral corners, acutely pointed at apex; apical sclerotized area small, triangular. Endophallus (Fig. 105E) with copulatory tube (Fig. 105I) moderately long, with basal chamber bulbous, main tube with apical tube occurring from the dorsal side near the apex of basal tube;
expulsion hooks (Fig. 105G) large, each with anterior plate acutely pointed at anterior tip; ventromedian bands moderately long, moderately broad. Parameres (Fig. 105E) stout, each very
acutely pointed at apex; apical area very large, very long, moderately swollen mesially at base,with an arcuate ventral ﬂap and with ventral margin bisinuate, mesially also with 2 long and 6
to11 short setae.
Female: Eighth ventrite obtusely pointed posteromedially; gonocoxites (Fig. 105H) eachwith apicolateral tooth long, broad at base, acute, apicolateral setae moderately long. Spermatheca (Fig. 105F) with capsule moderately long, rounded apically; striped duct short, slightly
thick; duct short, thin to moderately thick, with 2 turns, and also with a short sclerotized part alittle distal from basal valve; gland with opening located on the duct between the 1st and 2ndturns; basal valve very short; basal duct short, membranous.
Biology and ecology. S. okiensis is insular and may be endemic to Oki Islands oﬀ Shimane
Pref. The beetles of this species inhabit leaf litter heaped in the natural forests of low mountainous regions.
Remarks. Although S. okiensis is utterly diﬀerent in habitus and coloration from S. tsurusakii,
their very similar conditions of the structures of the endophallic copulatory tube as well as theaedeagal median lobe and parameres seem to ascertain their close relationship. S. okiensis isallied to S. tsurusakii, but it is separable from the latter species by the 6th and 7th ventrites ofmale each with a longer and shallower depression (Fig. 105C), the aedeagal paramere shorter,with its apex very acutely pointed (Fig. 105E), the copulatory tube shorter, with its apical tube
baculiform (Fig. 105I), and the endophallic expulsion hook with its anterior plate turning anteriorly (Fig. 105G).
Stenus tsurusakii Naomi(Fig. 106A–I)
Stenus tsurusakii Naomi, 1998: 100; Herman, 2001: 2423; Naomi & Puthz, 2013: 144.
Type material examined. Holotype: ♂ (CBM), Kano-cho, Kedaka-gun, Tottori Pref., 6. i.
1994, N. Tsurusaki leg. Paratypes: 1 ♂1 ♀, same data as holotype.
Distribution. Japan: Honshu (Tottori Pref.).
Redescription. Male and female: Body 3.6–3.8 mm (fore body 1.8–1.9 mm) in length. Body

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Fig. 106. Stenus tsurusakii Naomi (Tottori: Kano). A, 9th and 10th terga of male; B, aedeagus; C, copulatorytube; D, 9th ventrite of male; E, 6th and 7th ventrites of male; F, gonocoxite; G, posterior part of 8th ventriteof male; H, endophallic expulsion hooks; I, proximal part of spermatheca. Scale 1: 0.2 mm for A, B, D,
0.1 mm for C, F, H, I; scale 2: 0.25 mm for E; scale 3: 0.25 mm for G.

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moderately shining; head black, with clypeofronatal area dark red; pronotum and elytra reddish
brown; abdomen dark red; labrum reddish brown; antennae and legs yellowish brown to reddish
brown. Body with punctures round to ovoidal, small to moderately large, and also pronotum partially with coarse to subrugose punctures and elytra partially with large (and rarely very large),
subrugose punctures. Head moderately concave, with a pair of longitudinal-oblique furrows;
antennae moderately long, very thin; pronotum with surface slightly uneven to uneven, with a
median longitudinal furrow very indistinct; elytra with surface uneven; abdomen subcylindrical,
slightly tapering posteriorly; lateroventrites lost, tergoventral sutures very obsolete.
Male: Legs with femora thick; abdomen (Fig. 106E) modiﬁed with a ﬂat area on the 4th, ashallow, transverse depression on the 5th, a very large, very deep depression on the 6th, a large,
very deep depression on the 7th, and an almost triangular, moderately deep emargination on the
8th ventrite (Fig. 106G); 9th tergum with ventral apophyses long; 9th ventrite (Fig. 106D) withmacrosetae very short, apicolateral teeth short, acute, apicolateral setae moderately long; 10th
tergum moderately emarginate posteromedially. Aedeagus (Fig. 106B) with median lobe elongate, obtusely angulate at apicolateral corner, acutely pointed at apex with a moderately long apicomedian cusp; apical sclerotized area small, subtriangular. Endophallus (Fig. 106B) with copulatory tube (Fig. 106C) having basal club (into which the basal chamber and basal tube arefused?) very thick, apical tube thin, attenuate, occurring from the dorsal side near the apex ofbasal club; dorsolateral bands thin; expulsion hooks (Fig. 106H) slightly large, each with anterior
plate turning anterolaterally, nearly crescent in shape, very acutely pointed at anterior tip, posterior plate narrow; ventromedian bands long, slightly thin. Parameres (Fig. 106B) much extending
posteriorly beyond the apex of median lobe, each subulate and extremely thin at apex; apical area
very large, thick, very long, with a subtriangular ventral ﬂap at base and with ventral marginbisinuate, mesially also with 9 short setae before the middle and 1 long seta at about apical 2/3.
Female: Eighth ventrite almost acute posteromedially; gonocoxites (Fig. 106F) each withapicolateral tooth long, acute, apicolateral setae moderately long. Spermatheca (Fig. 106I) withbasal valve very short; basal tube very short; basal pouch subconical.
Biology and ecology. The beetles of S. tsurusakii inhabit leaf litter heaped in the natural forests of a lowland.
Remarks. S. tsurusakii is allied to S. okiensis, but it is separable from the latter species by the
6th and 7th ventrites of male each with a broader and deeper depression (Fig. 106E), the aedeagal paramere longer, with its apex aciculate (Fig. 106B), the copulatory tube longer, with its apical tube attenuate (Fig. 106C), and the endophallic expulsion hook with its anterior plate turning
anterolaterally (Fig. 106H).
Etymology. This species is named after Dr. Nobuo Tsurusaki (Tottori University) who studies
the chromosomal evolution and speciation of Opiliones hervestman in Japan.
Stenus akojagai Hromádka(Figs. 107A–H, 135C)
Stenus akojagai Hromádka, 1982: 132; Herman, 2001: 2048; Naomi & Puthz, 2013: 144.
Type material examined. Holotype: ♂ (NHMG), Mt. Daisen, Tottori Pref., 5. vi. 1965.
Other material examined. [HONSHU]: 3 ♂4 ♀, Misasa Spa, Tottori Pref., 28. ix. 1986, T. Itoleg.; 1 ♂1 ♀, Mt. Daisen, Tottori Pref., 26. iv. 1998, T. Kishimoto leg.; 1 ♂2 ♀, Sawada, Okayama
C., Okayama Pref., 18. i. 2004, Nakano & Fujitani leg.; 1 ♂, Midou Valley, Oosa-cho, Okayama

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Fig. 107. Stenus akojagai Naomi (Okayama: A, C, D, Sawada, B, Midou Valley; Tottori: E–H, Misasa). A, 9th
and 10th terga of male; B, 9th ventrite of male; C, aedeagus; D, endophallic copulatory tube and expulsion
hooks; E, gonocoxite; F, 6th and 7th ventrites of male; G, spermatheca; H, posterior part of 8th ventrite of
male. Scale 1: 0.2 mm for A–C, 0.1 mm for D, E, G; scale 2: 0.25 mm for F; scale 3: 0.25 mm for H.

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247

Pref., 2. xi. 2003, O. Yamaji leg.
Distribution. Japan: Honshu (Tottori and Okayama Prefs.).
Redescription. Male and female: Body 3.3–3.7 mm (fore body 1.6–1.9 mm) in length. Body
moderately shining; head reddish orange to reddish brown, with lateral parts of interocular area
infuscate; pronotum and elytra yellowish brown to reddish orange or reddish brown; abdomen
reddish brown with apical segments more or less infuscate; labrum reddish orange to reddish
brown; antennae and legs yellowish brown to reddish brown. Body with punctures round to elliptical, small to moderately large, and also pronotum partially with coarse to subrugose puncturesand elytra partially with large, coarse to subrugose punctures. Head moderately concave, with apair of longitudinal-oblique furrows or depressions; pronotum with surface slightly uneven to
uneven, with a median longitudinal depression hardly developed to very indistinct or indistinct;
elytra with surface uneven; abdomen subcylindrical, slightly tapering posteriorly to subparallelsided; lateroventrites lost, tergoventral sutures very obsolete or lost.
Male: Abdomen (Fig. 107F) modiﬁed with a very shallow depression on the 4th, a shallow
depression on the 5th, a moderately deep or deep depression on the 6th, a moderately deep ordeep depression (whose posterior part is weakly arcuately rounded posteriorly) on the 7th, and avery deep, V- or U-shaped emargination on the 8th ventrite (Fig. 107H); 9th tergum (Fig. 107A)
with ventral apophyses long; 9th ventrite (Fig. 107B) with apicolateral teeth moderately long,acute; 10th tergum (Fig. 107A) almost rounded posteriorly. Aedeagus (Fig. 107C) with median
lobe strongly bulbous in the basal 2/3, awl-shaped in the apical 1/3; basal foramen with its anterior sclerotization comprising a pair of small, almost tadpole-shaped plates. Endophallus (Fig.
107C) with copulatory tube (Fig. 107D) pot-shaped, with basal chamber and basal tube together
forming a cylindrical club, apical tube very thin, moderately curved; expulsion hooks (Fig.
107D) each almost Y-shaped, with membranous area developed between 2 anterior rods; ventromedian bands long, thin. Parameres (Fig. 107C) moderately thick, each very acutely pointed atapex; apical part long, moderately swollen mesially at base, and with ventral margin hardly or
weakly bisinuate, mesially with 6 to 8 setae of various length.
Female: Eighth ventrite obtuse posteromedially; gonocoxites (Fig. 107E) each with apicolateral tooth long, very acute, apicolateral setae very long. Spermatheca (Fig. 107G) with capsulesmall, well-rounded apically; striped duct very long, thick to very thick; duct moderately thick,short, tuberculate, tightly coiled; basal duct and basal porch fused to form a funnel-like, sclerotized structure.
Biology and ecology. The beetles of S. akojagai inhabit leaf litter heaped in the natural forests of lowlands to mountainous regions.
Remarks. When considering their common possessions of the similar forms of the aedeagal
parameres and copulatory tubes in S. okiensis, S. tsurusakii and S. akojagai, they are closely
allied one another, but S. akojagai is easily separable from the other 2 species by the awl-likeapical part of aedeagal median lobe (Fig. 107C).
Etymology. The speciﬁc epithet of this species is derived from the Japanese name of a Pteriid
seashell species, akojagai.

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Fig. 108. Stenus miroku Naomi (Shimane: Mt. Sanbe). A, 9th and 10th terga of male; B, aedeagus; C, 9th ventriteof male; D, spermatheca; E, 7th and 8th ventrites of male; F, endophallic copulatory tube, expulsion hooks
and ventromedian bands; G, posterior part of gonocoxite. Scale 1: 0.1 mm for A–C; scale 2: 0.1 mm for D, F,
G; scale 3: 0.3 mm for E.

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Stenus miroku Naomi(Fig. 108A–G)
Stenus miroku Naomi, 2006: 30; Naomi & Puthz, 2013: 144.
Type material examined. Holotype: ♂ (CBM), Takano City, Hiroshima Pref., 22. viii. 1982,
S. Tanaka leg.
Other material examined. [HONSHU]: 1 ♂1 ♀, Mt. Sanbe (NW-slope), Shimane Pref., 4. iii.
1998, K. Ishii leg.
Distribution. Japan: Honshu (Hiroshima and Shimane Prefs.).
Redescription. Male and female: Body 3.2–3.6 mm (fore body 1.5–1.7 mm) in length. Headmoderately shining; head almost black, with clypeofrontal or median area reddish brown to dark
red or dark red near black; pronotum and elytra yellowish orange to reddish brown; abdomen
reddish brown to dark reddish brown; labrum reddish brown; antennae and legs yellowish brown.
Body with punctures round to elliptical, small to moderately large, and also pronotum partiallywith subrugose punctures and elytra partially with large, subrugose punctures. Head shallowly
concave, with a pair of mesially-curved depressions; antennae moderately long, very thin; pronotum with surface uneven, with a median longitudinal furrow very indistinct; elytra with surface
strongly uneven, with a pair of large basimesial foveae and a pair of longitudinal anterolateralfurrows; abdomen subcylindrical, slightly tapering posteriorly; lateroventrites and tergoventral
sutures lost.
Male: Abdomen (Fig. 108E) modiﬁed with an elongate, ﬂat area on the 7th, and an arcuate,shallow emargination on the 8th ventrite; 9th tergum (Fig. 108A) with ventral apophyses long;
9th ventrite (Fig. 108C) with macrosetae moderately long, apicolateral teeth very acute, apicolateral setae long; 10th tergum (Fig. 108A) almost rounded posteriorly. Aedeagus (Fig. 108B) withmedian lobe bulbous at base, very narrow in about apical 1/2, pointed at apex; apical sclerotizedarea elongate-subtriangular in shape, very weakly rounded laterally. Endophallus with copulatory
tube (Fig. 108F) with basal chamber elongate-ovoidal in shape, main tube very long, needleshaped; expulsion hooks (Fig. 108F) broad-bean-shaped, weakly sclerotized; ventromedianbands atrophied into a pair of very thin, short bands. Parameres (Fig. 108B) robust, each verybroad at base, very acutely pointed at apex; apical area very long, mesially with 5 to 11 setae.
Female: Eighth ventrite obtuse posteromedially; gonocoxites (Fig. 108G) each with apicolateral tooth long, very acute, apicolateral setae very long; 10th tergum slightly protruding posteriorly to be the triangular apical part, pointed posteromedially. Spermatheca (Fig. 108D) with capsule moderately large, well-rounded apically; striped duct moderately long, slightly thin; ductvery short, moderately thick, with 2 turns; basal valve very short; basal duct moderately long;
basal pouch conical, membranous.
Biology and ecology. The beetles of S. miroku inhabit leaf litter heaped in the natural forestsof low mountainous to mountainous regions.
Remarks. S. miroku is allied to S. gagyumontis, but it is separable from the latter species by
the aedeagal median lobe thinner in the apical part, with its apical sclerotized area longer (Fig.
108B), the copulatory tube with its main tube needle-shaped and much thinner (Fig. 108F), theendophallic expulsion hooks developed and broad-bean-shaped (Fig. 108F).
Etymology. The speciﬁc epithet of this species is derived from the name of an enlighteneddeity, Miroku.

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Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

Fig. 109. Stenus masatakai Naomi & Nomura (Shimane: B, E, F, Urahikimi; Hiroshima: A, C, D, G, Yoshiwa).
A, aedeagus; B, 9th ventrite of male; C, 9th and 10th terga of male; D, 7th and 8th ventrites of male.; E, spermatheca; F, posterior part of gonocoxite; G, endophallic expulsion hooks and ventromedian bands. Scale 1:
0.1 mm for A, E, F, 0.05 mm for G; scale 2: 0.1 mm for B, C; scale 3: 0.2 mm for D.

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Stenus masatakai Naomi & Nomura(Fig. 109A–G)
Stenus masatakai Naomi & Nomura, 1990: 47; Herman, 2001: 2274; Naomi & Puthz, 2013: 144.
Type material examined. Holotype: ♂ (KUMF), Urahikimi, Shimane Pref., 24. viii. 1988, K.
Ogata leg. Paratypes: 1 ♂2 ♀, same data as holotype; 1 ♂2 ♀, Nakatsuya Val., Yoshiwa Vil., Hiroshima Pref., 8. vi. 1987, S. Nomura leg.
Other material examined. [HONSHU]: 1 ♂2 ♀, Kano, Shûnan, Yamaguchi Pref., 10–13. x.
2012, S. Tanaka leg.
Distribution. Japan: Honshu (Shimane, Hiroshima and Yamaguchi Prefs.)
Redescription. Male and female: Body 2.7–3.7 mm (fore body 1.3–1.7 mm) in length. Body
moderately shining; head black, with clypeofrontal or median area dark red to dark red near
black; pronotum and elytra reddish brown; abdomen reddish brown to dark reddish brown;
labrum reddish brown; antennae and legs yellowish brown to reddish brown. Body with punctures round to ovoidal, small to moderately large, and also pronotum partially with coarse to subrugose punctures and elytra partially with large, coarse to subrugose punctures. Head moderately
concave, with a pair of longitudinal-oblique furrows; antennae short, very thin; pronotum withsurface almost smooth to slightly uneven, with a median longitudinal furrow very indistinct; elytra with surface uneven; abdomen subcylindrical, subparallel-sided; lateroventrites and tergoventral sutures lost.
Male: Abdomen (Fig. 109D) modiﬁed with a ﬂat area on the 7th, and an arcuate, shallow
emargination on the 8th ventrite; 9th tergum (Fig. 109C) with ventral apophyses slightly short;
9th ventrite (Fig. 109B) with macrosetae very long, apicolateral teeth long, very acute, apicolateral setae moderately long; 10th tergum (Fig. 109C) entire. Aedeagus (Fig. 109A) with median
lobe subrhombic in about basal 1/2, narrow in about apical 1/2, pointed at apex; apical sclerotized area subtriangular. Endophallus (Fig. 109A) with copulatory tube with basal chamber comprising a pair of long, thin rods, main tube stick-like, attenuate, slightly curved in apical part;
dorsolateral bands moderately long, thin; expulsion hooks (Fig. 109G) atrophied into a pair ofsmall sclerites, each with posterior plate membranous or weakly sclerotized; ventromedian bands(Fig. 109G) atrophied, very short, very thin. Parameres (Fig. 109A) slender, each very acutely
pointed at apex; apical area very long, hardly swollen at base, mesially with 8 to 9 setae.
Female: Eighth ventrite obtuse posteromedially; gonocoxites (Fig. 109F) each with apicolateral tooth long, very acute, apicolateral setae very long. Spermatheca (Fig. 109E) with capsule
hardly developed; striped duct moderately long, thick; duct very short, strongly swollen anteriorly; gland elongate-ovoidal in shape, with opening located on the duct a little proximal from thebase of striped duct; basal valve very short; basal duct long, extending into the basal pouch
which is elongate-conical in shape and membranous.
Biology and ecology. The beetles of S. masatakai inhabit leaf litter heaped in the natural forests of low mountainous regions.
Remarks. S. masatakai is allied to S. gagyumontis, but it is separable from the latter species
by the 8th ventrite of male with a shallower emargination at the apex (Fig. 109D), the aedeagal
median lobe broader and pointed at the apex (Fig. 109A) and the spermatheca with its duct having a swollen chamber just proximal from the striped duct (Fig. 109E)
Etymology. This species is named after the late Dr. Masataka Sato who studied the aquaticand some other groups of Coleoptera in Japan.

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Fig. 110. Stenus gagyumontis Naomi (Okayama: Mt. Gagyu). A, aedeagus; B, 9th ventrite of male; C, 9th and10th terga of male; D, gonocoxite; E, endophallic copulatory tube, expulsion hooks and ventromedian bands;
F, spermatheca; G, 6th and 7th ventrites of male; H, posterior part of 8th ventrite of male. Scale 1: 0.2 mm for
A, B, 0.1 mm for D–F; scale 2: 0.2 mm for C; scale 3: 0.25 mm for G; scale 4: 0.25 mm for H.

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Stenus gagyumontis Naomi(Figs. 110A–H, 135D)
Stenus gagyumontis Naomi, 1990a: 4; Herman, 2001: 2194; Naomi & Puthz, 2013: 144.
Type material examined. Holotype: ♂ (KUF), Mt. Gagyu, Takahashi City, Okayama Pref.,28. viii. 1977, H. Ohishi leg. Paratypes: 4 ♂9 ♀, same data as holotype.
Other material examined. [HONSHU]: 1 ♂2 ♀, Gohkei, Okayama Pref., 16. v. 1993, T. Itoleg.
Distribution. Japan: Honshu (Okayama Pref.).
Redescription. Male and female: Body 3.2–3.6 mm (fore body 1.5–1.7 mm) in length. Body
moderately shining; head reddish orange to reddish brown, with lateral parts of interocular area
sometimes infuscate; pronotum and elytra reddish orange to reddish brown; abdomen reddish
brown to dark red, with posterior segments more or less infuscate; labrum reddish orange; antennae and legs yellowish brown to reddish brown. Body with punctures round to ovoidal, small tomoderately large, and also pronotum partially with coarse punctures and elytra partially withlarge, coarse to subrugose punctures. Head shallowly to moderately concave, with a pair of longitudinal-oblique furrows or depressions; antennae moderately long, very thin; pronotum withsurface almost even to slightly uneven, with a median longitudinal furrow hardly developed tovery indistinct; elytra with surface uneven; abdomen subcylindrical, slightly tapering posteriorly;
lateroventrites and tergoventral sutures lost.
Male: Abdomen (Fig. 110G) modiﬁed with a ﬂat area on the 4th; a large ﬂat area on the 5th,a very shallow depression on the 6th, an elongate, shallow depression on the 7th, and an arcuate,
moderated deep emargination on the 8th ventrite (Fig. 110H); 9th tergum (Fig. 110C) with ventral apophyses moderately long; 9th ventrite (Fig. 110B) with macrosetae very short, apicolateral
teeth very short, acute, apicolateral setae moderately long; 10th tergum (Fig. 110C) almost
rounded posteriorly. Aedeagus (Fig. 110A) with median lobe elongate, very slightly bisinuate laterally in about apical 2/3, narrowly rounded apically; apical sclerotized area narrow, roundedbasally. Endophallus (Fig. 110E) with copulatory tube having basal chamber elongate, main tube
long, attenuate, slightly curved behind the middle; expulsion hooks each atrophied into a very
thin, string-like plate; ventromedian bands short, very thin. Parameres (Fig. 110A) slightly
diverging posterolaterally in about apical 1/2, each narrowly rounded apically; apical area very
long, thick, mesially with 8 to 10 setae.
Female: Eighth ventrite obtuse posteromedially; gonocoxites (Fig. 110D) each with apicolateral tooth long, acute, apicolateral setae very long. Spermatheca (Fig. 110F) with capsule moderately large, well-rounded apically; striped duct short, moderately thick; duct very short, moderately thick, with 2 turns; basal valve very short; basal duct very long, thin.
Biology and ecology. The beetles of S. gagyumontis inhabit leaf litter heaped in the naturalforests of lowlands to low mountainous regions.
Remarks. S. gagyumontis is allied to S. masatakai, but it is separable from the latter species
by the 8th ventrite of male with a deeper emargination at the apicomedian part (Fig. 110H), theaedeagal median lobe narrower and narrowly rounded apically (Fig. 110A) and the spermathecawith its duct not having any swollen chamber (Fig. 110F).

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Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

Fig. 111. Stenus incurvatus Naomi & Nomura (Kagawa: Ayauta). A, 9th and 10th terga of male; B, 6th to 8th
ventrites of male; C, endophallus; D, aedeagus; E, 9th ventrite of male; F, posterior part of gonocoxite; G,
spermatheca. Scale 1: 0.2 mm for A, C–E, and 0.1 mm for F, G; scale 2: 0.3 mm for B.

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Stenus incurvatus Naomi & Nomura(Fig. 111A–G)
Stenus incurvatus Naomi & Nomura, 2015: 198.
Type material examined. Holotype: ♂ (NMNST), Sogisho-higashi (440 m), Ayakawa-cho,
Ayauta-gun, Kagawa Pref., 25. vi. 2011, M. Yoshida leg. Paratype: 1 ♀, same data as holotype.
Other material examined. [HONSHU]: 3 ♂2 ♀, Mt. Yuka, Kurashiki City, Okayama Pref., 6.
ii. 2005, O. Yamaji leg. [SHIKOKU]: 1 ♂1 ♀, Enoura, Marugame City, Kagawa Pref., 30. iv.
2011, H. Fujimoto leg.; 1 ♂1 ♀, Hachiman Shrine, Mannou-cho, Kagawa Pref., 7. iii. 2009, H.
Fujimoto leg.
Distribution. Japan: Honshu (Okayama Pref.) and Shikoku (Kagawa Pref.).
Redescription. Male and female: Body 3.3–3.4 mm (fore body 1.4–1.6 mm) in length. Body
moderately shining; head reddish orange to reddish brown, with lateral parts of interocular area
infuscate; pronotum and elytra reddish orange to reddish brown; abdomen entirely reddish
orange to reddish brown or dark reddish brown, or reddish orange with apical segments infuscate; labrum, antennae and legs yellowish brown to reddish brown. Body with punctures round to
elliptical, small to moderately large, and also pronotum partially with coarse punctures and elytra
partially with large, coarse to subrugose punctures. Head shallowly to moderately concave, witha pair of longitudinal-oblique furrows or depressions; antennae short to moderately long, verythin to thin; pronotum with surface almost even to slightly uneven, with a median longitudinalfurrow hardly developed to very indistinct; elytra with surface slightly uneven to uneven; abdomen subcylindrical, subparallel-sided; lateroventrites and tergoventral sutures lost.
Male: Abdomen (Fig. 111B) modiﬁed with a ﬂat area on the each of 4th and 5th, a shallow
depression on the 6th, a very large, deep depression on the 7th, and a moderately deep emargination on the 8th ventrite; 9th tergum (Fig. 111A) with ventral apophyses long; 9th ventrite (Fig.
111E) with macrosetae long, apicolateral teeth very short, acute, apicolateral setae moderately
long; 10th tergum (Fig. 111A) entire. Aedeagus (Fig. 111D) with median lobe moderately broad,obtusely angulate at apicolateral corners, almost pointed at apex; apical sclerotized area hardly
developed. Endophallus (Fig. 111C) with copulatory tube having basal chamber narrow, maintube very long, thin, attenuate; explusion hooks each atrophied into a very small, C-shaped sclerite; ventromedian bands short, moderately broad; lateral diverticula slightly thin, membranous
Parameres (Fig. 111D) moderately diverging posterolaterally in apical part, rounded apically;
apical area slightly thick, slightly swollen mesially at base, mesially also with 8 to 9 short setae.
Female: Eighth ventrite almost rounded posteriorly or obtuse posteromedially; gonocoxites(Fig. 111F) each with apicolateral tooth long, almost acute, apicolateral setae moderately long.
Spermatheca (Fig. 111G) with capsule small, rounded apically; striped duct very long, moderately thick; duct short, very thin to moderately thick, with 2 turns; gland very small, located on
the duct between the 1st and 2nd turns; basal valve invisible; basal duct very long, very thin in
the distal 2/3, becoming thicker proximad in the proximal 1/3.
Biology and ecology. The beetles of S. incurvatus inhabit leaf litter heaped in the natural forests of low mountainous regions.
Remarks. S. incurvatus is allied to S. okamotoi, but it is separable from the latter species by
the aedeagal median lobe widely angulate at the apicolateral corner, with its apical triangular part
longer and hardly emarginate apicolaterally (Fig. 111D), and the endophallic ventromedian bands
usually narrower (Fig. 111C).

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Fig. 112. Stenus okamotoi Naomi (Hiroshima: A, B, D, Higashi-hiroshima, E, G, H, Kawauchi; Ehime: C, Mt.
Shiogamori, F, Tateiwa). A, 9th and 10th terga of male; B, aedeagus; C, 6th to 8th ventrites of male; D, apicalpart of aedeagal median lobe with endophallic dorsolateral bands and expulsion hooks; E, posterior part ofgonocoxite; F, 9th ventrite of male; G, spermathecal; H, posterior part of 8th ventrite of female. Scale 1:
0.2 mm for A, B, F, H, 0.1 mm for E, G, 0.05 mm for D; scale 2: 0.3 mm for C.

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Stenus okamotoi Naomi(Figs. 112A–H, 135E)
Stenus okamotoi Naomi, 1989a: 2; Herman, 2001: 2313; Naomi & Puthz, 2013: 143.
Type material examined. Holotype: ♂ (KUF), Shichitsukahara, Shôbaru City, Hiroshima
Pref., 1. v. 1987, I. Okamoto leg. Paratypes: 1 ♀, Yoshiwa Vil., Hiroshima Pref., 18. v. 1986, I.
Okamoto leg.; 1 ♀, Hôei-cho, Hiroshima Pref., 4. vii. 1986, I. Okamoto leg.; 1 ♀, same locality,
8. vi. 1986, I. Okamoto leg.; 1 ♀, Kawachi-cho, Kamo-gun, Hiroshima Pref., 9. v. 1987, I. Okamoto leg.; 1 ♂, Higashi-hiroshima, Hiroshima Pref., 3. viii. 1985, I. Okamoto leg.
Other material examined. [SHIKOKU]: 1 ♂1 ♀, Mt. Shiogamori, Kawauchi-cho, Ehime
Pref., 19. ix. 1993, M. Sakai leg.; 1 ♂, Tateiwa, Hôjyô City, Ehime Pref., 27. vii. 1991, I. Okamoto leg.
Distribution. Japan: Honshu (Hiroshima Pref.) and Shikoku (Ehime Pref.).
Redescription. Male and female: Body 3.2–3.8 mm (fore body 1.5–1.8 mm) in length. Body
moderately shining; head reddish orange to dark red or dark brown, with lateral parts of interocular area more or less infuscate; pronotum and elytra reddish orange to reddish brown; abdomen
reddish orange to reddish brown, sometimes with apical segments infuscate; labrum, antennae
and legs yellowish brown to reddish brown. Body with punctures round to elliptical, small tomoderately large, and also pronotum partially with coarse or subrugose punctures and elytra partially with large, coarse to subrugose punctures. Head shallowly to moderately concave, with apair of longitudinal-oblique or mesially-curved furrows (or depressions); antennae short to moderately long, very thin; pronotum with surface almost even to slightly uneven or uneven, with a
median longitudinal furrow hardly developed to very indistinct or indistinct; elytra with surface
slightly uneven to uneven; abdomen subcylindrical, subparallel-sided; lateroventrites and tergoventral sutures lost.
Male: Abdomen (Fig. 112C) modiﬁed with a ﬂat area on the 6th, an elongate, very shallow
depression on the 7th, and a moderately deep, subtriangular emargination on the 8th ventrite; 9th
tergum (Fig. 112A) with ventral apophyses very long; 9th ventrite (Fig. 112F) with apicolateral
teeth short, very acute, apicolateral setae moderately long; 10th tergum (Fig. 112A) very slightly
emarginate posteromedially. Aedeagus (Fig. 112B) with median lobe moderately broad, almost
rectangularly angulate at apicolateral corners, pointed at apex, arcuately emarginate apicolaterally; apical sclerotized area hardly developed. Endophallus (Fig. 112B) with copulatory tube
very long, with basal chamber elongate-ovoidal in shape, main tube almost baculiform, attenuate
behind the middle; dorsolateral bands (Fig. 112D) each atrophied into a very small, almost rectangular band; expulsion hooks (Fig. 112D) each atrophied into a very small, L-shaped sclerite;
ventromedian bands (Fig. 112B) each short, broad at posterior rim (Fig. 112B). Parameres (Fig.
112B) slightly diverging posterolaterally in apical part, each rounded apically; apical area moderate thick, moderately swollen mesially at base, mesially also with 7 to 8 setae of diﬀerent length.
Female: Eighth ventrite almost obtuse posteromedially (Fig. 112H); gonocoxites (Fig. 112E)
each with apicolateral tooth long, acute, apicolateral setae very long. Spermatheca (Fig. 112G)
with capsule very small; striped duct long, moderately thick; duct short, thin to moderately thick,with 2 turns; basal valve short, very thin; basal duct very long, thin, becoming slightly thicker
proximad at proximal part; basal pouch conical, broader than long.
Biology and ecology. The beetles of S. okamotoi inhabit leaf litter heaped in the natural forests of lowlands to low mountainous regions. The beetles of this species were once collected258

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Fig. 113. S. amma Naomi (Hyogo: A–C, F, G, Taga; Nara: D, E, Dorogawa). A, 9th and 10th terga of male; B,
aedeagus; C, spermatheca; D, 9th ventrite of male; E, 8th ventrite of male; F, posterior part of gonocoxite; G,
endophallic expulsion hooks and ventromedian bands. Scale 1: 0.1 mm for A, B, 0.05 mm for C, 0.2 mm for D;
scale 2: 0.2 mm for E, 0.1 mm for F, G.

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from the haystack at Mt. Shiogamori, Ehime Pref.
Remarks. S. okamotoi is allied to S. incurvatus, but it is separable from the latter species by
the aedeagal median lobe almost rectangularly angulate at the apicolateral corners, with its apicaltriangular part shorter and arcuately emarginate apicolaterally (Fig. 112B) and the endophallic
ventromedian bands usually broader (Fig. 112B).
Etymology. This species is named after Mr. Iwao Okamoto (Hiroshima) who collected all the
Stenus-beetles designated as the type specimens.
Stenus amma Naomi & Nomura(Figs. 113A–G, 135F)
Stenus amma Naomi & Nomura, 1990: 45; Herman, 2001: 2054; Naomi & Puthz, 2013: 144.
Type material examined. Holotype: ♂ (KUF), Ikeda City, Osaka Pref., 25. v. 1985, S.
Nomura leg.
Other material examined. [HONSHU]: 1 ♂1 ♀, Dorogawa, Nara Pref., 2. v. 1985, T. Ito leg.;1 ♂2 ♀, Taga, Sayô-cho, Hyogo Pref., 4. ix. 2017, T. Ito leg. [SHIKOKU]: 2 ♂2 ♀, Uchimi-cho,
Shôdo Is., Kagawa Pref., 3. xi. 2004, F. Sasaki leg.
Distribution. Japan: Honshu (Nara, Osaka and Hyogo Prefs.) and Shikoku (Kagawa Pref.:Shodo Is.).
Redescription. Male and female: Body 3.0–3.6 mm (fore body 1.5–1.7 mm) in length. Body
moderately shining and entirely reddish orange to reddish brown except for the infuscate lateralparts of interocular area and apical segments of abdomen; labrum, antennae and legs yellowish
brown to reddish brown or brown. Body with punctures round to elliptical, small to moderately
large, and also pronotum partially with coarse to subrugose punctures and elytra partially withlarge, coarse or subrugose punctures. Head shallowly concave, with a pair of longitudinaloblique depressions; antennae moderately long, very thin; pronotum with surface slightly unevento uneven, with a median longitudinal furrow very indistinct or indistinct; elytra with surface
uneven; abdomen subcylindrical, subparallel-sided; lateroventrites and tergoventral sutures lost.
Male: Body modiﬁed with a small, semicircular, very shallow depression on the 6th, an elongate, very shallow depression on the 7th, and a moderately large, subtriangular emargination on
the 8th ventrite (Fig. 113E); 9th tergum (Fig. 113A) with ventral apophyses very long; 9th ventrite (Fig. 113D) with apicolateral teeth long, acute, apicolateral setae moderately long; 10th tergum (Fig. 113A) weakly emarginate posteriorly. Aedeagus (Fig. 113B) with median lobe broad,obtusely angulate at apicolateral corners, very minutely incised at apicomedian part; apical sclerotized area hardly developed. Endophallus (Fig. 113B) with copulatory tube with basal chambersubfusiform, main tube very long, moderately swollen laterally near the middle; expulsion hooks(Fig. 113G) each atrophied into a very thin, almost L-shaped sclerite; ventromedian bands (Fig.
113G) short, slightly narrow. Parameres (Fig. 113B) moderately diversing posterolaterally in apical part; apical area thick, strongly swollen mesially at base, mesially also with 7 small setae.
Female: Eighth ventrite obtuse posteromedially; gonocoxites (Fig. 113F) each with apicolateral tooth long, very acute, apicolateral setae long. Spermatheca (Fig. 113C) with capsule small,rounded apically; duct short, moderately thick to thick, densely striped in full length; basal valve
short, thin; basal duct extremely long, with an elongate-subconical base.
Biology and ecology. The beetles of S. amma inhabit leaf litter heaped in the natural forestsof lowlands to mountainous regions.

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Fig. 114. Stenus enma Naomi (Hiroshima: A–D, F, G, Shôbara,E, H, Mukaibara). A, 4rd to 7th ventrites of male;B, 9th and 10th terga of male; C, aedeagus; D, 9th ventrite of male; E, spermatheca; F, 8th ventrite of male; G,
endophallic expulsion hooks; H, gonocoxite. Scale 1: 0.25 mm for A; scale 2: 0.25 mm for F; scale 3: 0.2 mm
for B–D, 0.1 mm for E, H; scale 4: 0.05 mm for G.

The Steninae of Japan Part 3261

Remarks. S. amma is allied to S. enma, but it is separable from the latter species by theabdominal modiﬁcations of male much less developed, the aedeagal median lobe with its apicomedian part very minutely incised (Fig. 113B), the copulatory tube with its main tube much longer, and moderately swollen laterally only near the middle (Fig. 113B), and the paramere with its
apical area much shorter (Fig. 113B).
Etymology. The speciﬁc epithet of this species is derived from an anagram of a Japaneseword ʻmamaʼ that suggests ʻkeepʼ or ʻremainʼ, namely, ʻammaʼ, hoping that the biological diversityof beetle fauna in Japan remains high in the future.
Stenus enma Naomi(Fig. 114A–H)
Stenus enma Naomi, 1990a: 6; Herman, 2001: 2168; Naomi & Puthz, 2013: 144.
Type material examined. Holotype: ♂ (KUF), Mukaibara-cho, Hiroshima Pref., 29. ix. 1985,
I. Okamoto leg. Paratype: 1 ♀, same data as holotype.
Other specimens examined. [HONSHU]: 2 ♂, Nanatsukahara, Shôbara, Hiroshima Pref., 28.
iv. 1990, I. Okamoto leg.
Distribution. Japan: Honshu (Hiroshima Pref.).
Redescription. Male and female: Body 2.9–3.5 mm (fore body 1.7–1.8 mm) in length. Body
moderately shining; head reddish orange, with lateral parts of interocular area more or less infuscate; pronotum and elytra reddish orange; abdomen reddish brown with apical segments infuscate; labrum, antennae and legs yellowish brown to reddish orange. Body with punctures roundto ovoidal, small to moderately large, and also pronotum partially with coarse punctures and elytra partially with coarse to subrugose punctures. Head moderately concave, with a pair of longitudinal-oblique furrows; antennae short, very thin; pronotum with surface slightly uneven to
uneven, with a median longitudinal furrow very indistinct to indistinct; elytra with surface
slightly uneven to uneven, with a pair of small, indistinct depressions at anteromesial parts;
abdomen subcylindrical, slightly tapering posteriorly; lateroventrites and tergoventral sutures
lost.
Male: Legs with femora thick; hind tibiae each moderately curved mesially before the middle; abdomen (Fig. 114A) modiﬁed with a slightly small, shallow depression on the 3rd, a verylarge, deep depression on each of the 4th to 6th, a large, very deep depression on the 7th, and a
deep, almost triangular emargination on the 8th ventrite (Fig. 114F); 9th tergum (Fig. 114B) withventral apophyses very long; 9th ventrite (Fig. 114D) with apicolateral teeth short, almost acute,apicolateral setae moderately long; 10th tergum (Fig. 114B) very weakly emarginate posteromedially. Aedeagus (Fig. 114C) with median lobe moderately franked ventrolaterally with ventral
walls, angulate at apicolateral corners, triangular at apical part; apical sclerotized area lost. Endophallus (Fig. 114C) with copulatory tube moderately long, with basal chamber having a pair ofthin rods, main tube almost elongate-fusiform in shape; expulsion hooks (Fig. 114G) each atrophied into a very small sclerite; ventromedian bands short, narrow. Parameres (Fig. 114C) thick;apical area very long, almost ﬂat, broad dorsoventrally, mesially with 10 to 12 short setae.
Female: Eighth ventrite obtuse posteromedially; gonocoxites (Fig. 114H) each with apicolateral tooth long, very acute, apicolateral setae moderately long. Spermatheca (Fig. 114E) with
capsule large, much rounded apically, a little broader than striped duct; striped duct moderately
long, moderately thick, only with a few transverse stripes; duct short, thin to moderately thick,262

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with 2 turns; basal valve very short; basal duct long, becoming slightly thicker proximad at base.
Biology and ecology. The beetles of S. enma inhabit leaf litter heaped in the natural forests oflow mountainous regions.
Remarks. S. enma is allied to S. amma, but it is separable from the latter species by theabdominal modiﬁcations of male much more developed with various forms of depressions andemarginations (Fig. 114A), the aedeagal median lobe pointed at the apicomedian part (Fig.
114C), the copulatory tube with its main tube much shorter and almost elongate-fusiform inshape (Fig. 114C), and the paramere with its apical area much longer (Fig. 114C).
Etymology. The speciﬁc epithet of this species is derived from the title name of a chant or
Noh song for the traditional performing arts in Japan, Enma.
Stenus uenoi Naomi & Nomura(Fig. 115A–G)
Stenus bosatsu Naomi, 1989: 159 (in part).
Stenus uenoi Naomi & Nomura, 1990: 46; Herman, 2001: 2424; Naomi & Puthz, 2013: 144.
Stenus expansus Naomi & Ito, 2018: 92 (in part).
Type material examined. Holotype: ♂ (KUF), Odona, Neba Vil., Nagano Pref., 28. x. 1985,
S. Nomura leg. Paratypes: 3 ♂5 ♀, same data as holotype; 1 ♂1 ♀, Mt. Togakushi, Nagano Pref.,26. viii. 1983, S. Nomura leg.; 3 ♂4 ♀, Goushima, Haruno-cho, Shizuoka Pref., 23. x. 1985, S.
Nomura leg.; 1 ♂, Mt. Sanage, Aichi Pref., 24. x. 1970, K. Yamagishi leg.; 2 ♂5 ♀ (paratypes of
S. bosatus), Sasagamine, Mt. Myôkô, Niigata Pref., 14–15. vi. 1980, S. Naomi leg.; 1 ♂ (paratype of S. expansus), Mennoki Pass, Aichi Pref., 13. viii. 1990, S. Nomura leg.
Other material examined. [HONSHU]: 1 ♂, Nozumi, Teradomari-cho, Niigata Pref., 22. v.
1996, M. Maruyama leg.; 1 ♂1 ♀, Togakushi Highland, Nagano Pref., 5–6. vii. 2008, T. Ito leg.;2 ♂4 ♀, Hinatami Riv., Shima Spa., Gunma Pref., 15–16. ix. 1996, S. Naomi & M. Maruyama
leg.; 1 ♂1 ♀, Yuya Spa, Gero, Gifu Pref., 26. vi. 2008, T. Ito; 1 ♂, Mennoki Pass, Aichi Pref., 13.
viii. 1990, S. Nomura leg.; 6 ♂1 ♀, Jyôkô-ji, Aichi Pref., 11. viii. 1993, T. Ito leg.; 3 ♂1 ♀,Dando-Uradani, Shitara-cho, Aichi Pref., 5. x. 1998, S. Nomura leg.; 2 ♂1 ♀, Suwa, Ueno City,
Mie Pref., 24. x. 1996, H. Yokozeki leg. [SHIKOKU]: 1 ♂, Miyanotani Pond, Shikokuchuô City,
Ehime Pref., 30. x. 2005, Y. Katayama leg.
Distribution. Japan: Honshu (Kanto, Chubu and Kinki Districts) and Shikoku (Ehime Pref.)Redescription. Male and female: Body 3.2–4.0 mm (fore body 1.5–2.0 mm) in length. Body
weakly to moderately shining; head black; pronotum, elytra and abdomen reddish brown to dark
reddish brown or almost black; labrum reddish brown; antennae and legs yellowish brown to reddish brown. Body with punctures round to elliptical, small to moderately large, and also pronotum partially with coarse to subrugose punctures and elytra partially with large, subrugose punctures. Head shallowly concave, with a pair of longitudinal-oblique or mesially-curved furrows(or depressions); antennae short to moderately long, very thin to thin; pronotum with surface
slightly uneven to uneven, with a median longitudinal furrow very indistinct to indistinct; elytra
with surface uneven; abdomen subcylindrical, subparallel-sided; lateroventrites lost, tergoventrite sutures almost lost.
Male: Abdomen (Fig. 115F) modiﬁed with a broad-subtriangular or semicircular emargination on the 8th ventrite; 9th tergum (Fig. 115E) with ventral apophyses very long; 9th ventrite(Fig. 115A) with apicolateral teeth very acute, apicolateral setae long; 10th tergum (Fig. 115E)

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Fig. 115. Stenus uenoi Naomi & Nomura (Nagano: A, C, E, F, Mt. Togakushi, B, D, G, Neba). A, 9th ventrite ofmale; B, posterior part of gonocoxite; C, aedeagus; D, spermatheca; E, 9th and 10th terga of male; F, posterior
part of 8th ventrite; G, copulatory tube. Scale 1: 0.1 mm for A, C; scale 2: 0.1 mm for B, D; scale 3: 0.2 mm
for E, F; 0.1 mm for G.

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Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

very shallowly emarginate posteromedially. Aedeagus (Fig. 115C) with median lobe bulbous atbase, very narrow in about apical 1/3, almost truncate at apex or with a very small, pointed apicomedian cusp (Fig. 115C); apical sclerotized area hardly or slightly developed. Endophallus(Fig. 115C) with copulatory tube usually subfusiform (Fig. 115C) or nearly willow-leaf-shaped(Fig. 115G) but often varied in shape; dorsolateral bands (Fig. 115C) long, moderately broad;
expulsion hooks atrophied into a pair of small sclerites; ventromedian bands very long, very narrow. Parameres (Fig. 115C) long, thick, each almost rounded apically; apical area long to very
long, distinctly thicker than pedicel, mesially with 8 to 9 short setae and apically with a moderately long seta.
Female: Eighth ventrite almost rounded posteromedially; gonocoxites (Fig. 115B) each withapicolateral tooth very long, thin, acute, apicolateral setae very long. Spermatheca (Fig. 115D)with capsule small; striped duct moderately long, moderately thick; duct very long, thin to moderately thick, coiled.
Biology and ecology. S. uenoi is widely distributed from Honshu (Chubu and Kinki Districts)
to Shikoku in Japan, and thus S. uenoi is the species whose distributional range is widest among
the species of cephalotes-group. The beetles of S. uenoi inhabit leaf litter heaped in the naturalforests of lowlands through low mountainous to high mountainous regions.
Remarks. S. uenoi was ﬁrst identiﬁed and included as a part of paratypes of S. bosatsu when
Naomi (1989) described S. bosatsu as new species. Naomi & Nomura (1990) newly described S.
uenoi, based on the holotype specimen (Odona, Nagano) and other paratype specimens (Nagano,Shizuoka and Aichi). After that, when Naomi (2012) redescribed S. uenoi, he erroneously
included some specimens of S. expansus as well as those of S. uenoi in the specimens of S. uenoi
examined. He also drew varied forms of the aedeagal median lobes and parameres of S. uenoi
and S. expansus as those of S. uenoi because these variations were considered to be infraspeciﬁc
at that time. Furthermore, when Naomi & Ito (2018) newly described S. expansus, they included
1 male specimen of S. uenoi as the paratype of S. expansus.
S. uenoi is allied to S. expansus, but it is separable from the latter species by the aedeagal
median lobe with its posterior part broader and its apical sclerotized area less developed (Fig.
115C), the endophallic copulatory tube developed (Fig. 115C, G), the paramere with its apicalarea less strongly expanded almost dorsoventrally (Fig. 115C), and the spermatheca with its duct
thicker (Fig. 115D).
Probably closely related to the very wide distributional range of this species, S. uenoi shows
considerable variations regarding the structures of aedeagus and copulatory tube. First, the apicalsclerotized area of median lobe is slightly developed and almost rounded apically, hardly developed and almost truncate apically, or hardly or slightly developed and almost rounded apically,and furthermore, it is apicomedially with or without a very small, pointed cusp (Fig. 115C) (seealso Naomi, 2012, p. 304). Second, the copulatory tube is usually willow-leaf-shaped as in Fig.
115C or G, but it is varied by the posterior extension of its thin posterior portion, the more strong
curvature of main tube, the addition of paired subtransparent ﬂaps to the main tube, etc.
Etymology. This species is named after the late Dr. Shun-Ichi Ueno (National Museum of
Nature and Science, Tokyo) who studies the Carabidae and other cave-dwelling beetles in Japanand also in the various areas of Asia.

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Stenus expansus Naomi & Ito(Figs. 116A–G, 135G)
Stenus uenoi Naomi & Nomura: Naomi, 2012: 301 (in part).
Stenus expansus Naomi & Ito, 2018: 92 (in part).
Type material examined. Holotype: ♂ (KUMF), Araidashi Forest, Kamiyahagi, Ena, Gifu
Pref., 18. x. 2015, T. Watanabe leg. Paratypes: 1 ♂2 ♀, same data as holotype; 1 ♂, Mt. Kurai,
Gifu Pref., 28. x. 2017, T. Ito leg.; 1 ♂1 ♀, Mennoki Pass, Aichi Pref., 13. viii. 1990, S. Nomura
leg.
Distribution. Japan: Honshu (Gifu and Aichi Prefs.).
Description. Male and female: Body 3.2–3.8 mm (fore body 1.6–1.8 mm) in length. Body
weakly shining; head black; pronotum brown to dark red near black; elytra reddish brown to dark
red; abdomen reddish brown to dark reddish brown or almost black; labrum reddish brown todark red; antennae and legs yellowish brown to reddish brown. Body with punctures round to
elliptical, small to moderately large, and also pronotum partially with subrugose punctures andelytra partially with large, subrugose punctures. Head moderately concave, with a pair of longitudinal-oblique furrows; antennae short to moderately long, very thin; pronotum with surface
uneven, with a median longitudinal furrow indistinct; elytra with surface uneven; abdomen subcylindrical, subparallel-sided; lateroventrites lost, tergoventrite sutures almost lost.
Male: Abdomen (Fig. 116D) modiﬁed with an elongate, very shallow depression on the 7th
and a subtriangular or broad-subtriangular (Fig. 116D) emargination on the 8th ventrite; 9th tergum (Fig. 116A) with ventral apophyses long; 9th ventrite (Fig. 116B) with apicolateral teeth
long, very acute, apicolateral setae slightly short; 10th tergum (Fig. 116A) entire. Aedeagus (Fig.
116E) with median lobe moderately broad at base, very narrow in about apical 1/3, narrowly
rounded apically; apical sclerotized area small, subtriangular. Endophallus (Fig. 116E) with copulatory tube with basal chamber spherical, main tube strongly atrophied into a small, spine-likesclerite; dorsolateral bands long, very thin; expulsion hooks atrophied into a very small, wide
V-shaped sclerite (Fig. 116G) or a pair of very thin sclerites; ventromedian bands long, very narrow. Parameres (Fig. 116E) moderately diverging posteriorly, each rounded apically; apical area
very long, expanded almost dorsoventrally, mesially with 1 to 8 setae and apically with a moderately long seta.
Female: Eighth ventrite almost rounded posteriorly or obtuse posteromedially; gonocoxites(Fig. 116F) each with apicolateral tooth very long, very acute, apicolateral setae very long. Spermatheca (Fig. 116C) with capsule short, very thin; striped duct moderately long, thin; duct
extremely long, extremely thin but very thin to thin in the distal part, with its anterior massstrongly coiled; gland densely covered with very thin ciliae, with its opening located on the lateral side of duct a little proximal from the last 9th turn; basal duct long, very thin.
Biology and ecology. The beetles of S. expansus inhabit leaf litter heaped in the natural forests of mountainous regions.
Remarks. S. expansus is allied to S. uenoi, but it is separable from the latter species by theaedeagal median lobe with its posterior part narrower and its apical sclerotized area more developed to be subtriangular (Fig. 116E), the copulatory tube strongly atrophied (Fig. 116E), theparamere with its apical area more strongly expanded almost dorsoventrally (Fig. 116E), and thespermatheca with its duct thinner (Fig. 116C).

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Fig. 116. Stenus expansus Naomi & Ito (Gifu: A, Araidashi, D, Mt. Kurai; Aichi: B, C, E–G, Mennoki Pass). A,
9th and 10th tergites of male; B, 9th ventrite of male; C, spermatheca; D, 7th and 8th ventrites of male; E,
aedeagus; F, posterior part of gonocoxite; G, endophallic expulsion hook. Scale 1: 0.1 mm for A; scale 2:
0.2 mm for B, E, 0.05 mm for G; scale 3: 0.1 mm for C, F; scale 4: 0.3 mm for D.

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267

Stenus masaakii Naomi & Nomura(Fig. 117A–E)
Stenus masaakii Naomi & Nomura, 2015: 190.
Type material examined. Holotype: ♂ (NMNST), Seinaiji Pass, Nagiso-cho, Nagano Pref.,15. xi. 1999, S. Nomura leg.
Distribution. Japan: Honshu (Nagano Pref.).
Redescription. Male: Body 4.0 mm (fore body 1.9 mm) in length. Body moderately shining;head black; pronotum and elytra dark red; abdomen dark reddish brown; labrum reddish orange;
antennae and legs yellowish brown to reddish brown. Body with punctures round to ovoidal,
small to moderately large, and also pronotum partially with subrugose punctures and elytra partially with large, subrugose punctures. Head moderately concave, with a pair of longitudinaloblique furrows; antennae moderately long, very thin; pronotum with surface uneven, with a
median longitudinal furrow very indistinct; elytra with surface uneven; abdomen subcylindrical,
subparallel-sided; lateroventrites and tergoventrite sutures lost.
Abdomen modiﬁed with a very shallow depression on the 7th, and an arcuate, moderately
deep emargination on the 8th ventrite (Fig. 117E); 9th tergum (Fig. 117C) with ventral apophyses
moderately long; 9th ventrite (Fig. 117A) with macrosetae very long, apicolateral teeth very
long, acute, apicolateral setae moderately long; 10th tergum (Fig. 117C) entire. Aedeagus (Fig.
117D) with median lobe elongate-ovoidal in shape at base, moderately narrowed in about apical
1/3, apicoventrally with a pair of low ﬂaps, obtusely angulate at apex; apical sclerotized area
broad-subtriangular in shape, anteromedially with an arcuate emargination. Endophallus (Fig.
117B) with copulatory tube with main tube moderately thick, attenuate; explusion hooks atrophied and fused into a relatively small, sclerite which has a U-shaped emargination; ventromedian bands very broad; lateral diverticula in pair very broad, membranous. Parameres (Fig.
117D) moderately diverging posteriorly, each thick, acute at apex; apical area extremely long,with 8 to 9 short setae along dorsomesial margin and 7 to 9 long setae along ventromesial margin.
Female. Unknown.
Biology and ecology. The beetle of S. masaakii inhabits leaf litter heaped in the natural forestof a mountainous region.
Remarks. S. masaakii is allied to S. uenoi and S. expansus, but it is separable from the latter2 species by the aedeagal median lobe broader in the apical part (Fig. 117D), the copulatory tube
baculiform and attenuate (Fig. 117B), the endophallic expulsion hooks fused into a relatively
small, sclerite which has a U-shaped emargination (Fig. 117B), and the paramere more acutely
pointed at apex, with its apical area much longer (Fig. 117D).
Etymology. This species is named after Mr. Masaaki Nishikawa (Kanagawa) who studies theSilphidae in Japan.
Stenus bosatsu Naomi(Figs. 118A–G, 135H)
Stenus bosatsu Naomi, 1989: 159; Herman, 2001: 2097; Naomi & Puthz, 2013: 144.
Type material examined. Holotype: ♂ (KUF), Kaminikkawa Pass, Daibosatsu, Yamanashi

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Fig. 117. Stenus masaaki Naomi & Nomura (Nagano: Nagiso-cho). A, 9th ventrite of male; B, apical part ofaedeagus and outthrusted endophallus; C, 9th and 10th terga of male; D, aedeagus; E, posterior part of 8th
ventrite of male. Scale 1: 0.2 mm for A, C–E, 0.1 mm for B.

The Steninae of Japan Part 3269

Fig. 118. Stenus bosatsu Naomi (Tokyo: A, B, D, E, Mt. Mitake; Yamanashi: C, F, G, Daibosatsu). A, 9th and10th terga of male; B, aedeagus; C, spermatheca; D, 9th ventrite of male; E, copulatory tube; F, 7th and 8th
ventrites of male; G, posterior part of gonocoxite. Scale 1: 0.2 mm for A, B, D, 0.1 mm for C, E, G; scale 2:
0.3 mm for F.

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Pref., 15–18. vii. 1982, S. Naomi leg. Paratypes: 1 ♂3 ♀, same data as holotype.
Other material examined. [HONSHU]: 1 ♂, Daibosatsu, Yamanashi Pref., 26. vi. 1988, T. Itoleg.; 2 ♂5 ♀, Sanjyo-sawa, Tabayama Vil., Yamanashi Pref., 15. ix. 2000, S. Arai leg.; 2 ♂4 ♀,Nishizawa Valley, Mitomi Vil., Yamanashi Pref., 17. xi. 1999, S. Nomura leg.; 1 ♂, Mt. Mitake,
Oume City, Tokyo Metro., 12. viii. 1990, T. Ito leg.; 1 ♂, Mizunezawa, Okutama, Tokyo Metro.,
6. v. 1990, T. Kishimoto leg.
Distribution. Japan: Honshu (Yamanashi Pref. and Tokyo Metro.).
Redescription. Male and female: Body 3.2–4.0 mm (fore body 1.4–1.9 mm) in length. Body
moderately shining; head black; pronotum and elytra reddish brown to dark red; abdomen dark
red to dark brown; labrum reddish brown; antennae and legs yellowish brown to reddish brown.
Body with punctures round to elliptical, small to moderately large, and also pronotum partiallywith subrugose punctures and elytra partially with large, subrugose punctures. Head moderately
concave, with a pair of almost longitudinal-oblique furrows; antennae moderately long, very
thin; pronotum with surface uneven, with a median longitudinal furrow very indistinct to indistinct; elytra with surface uneven; abdomen subcylindrical, subparallel-sided; lateroventrites lost,
tergoventrite sutures very thin.
Male: Abdomen (Fig. 118F) modiﬁed with a ﬂat area on the 6th, a very shallow or shallow
depression on the 7th, and a basal depression and also a broad-subtriangular emargination on the
8th ventrite; 9th tergum (Fig. 118A) with ventral apophyses very long; 9th ventrite (Fig. 118D)
with macrosetae short, apicolateral teeth very long, thin, very acute, apicolateral setae long; 10th
tergum (Fig. 118A) shallowly emarginate posteromedially. Aedeagus (Fig. 118B) with median
lobe distinctly narrowed behind the middle, obtusely pointed at apex; apical sclerotized area
extremely small, broad-subtriangular in shape. Endophallus (Fig. 118B) with copulatory tube
(Fig. 118E) having basal chamber small, consisting of 2 thin, short rods, main tube baculiformwith a pair of very thin, slightly curved lateral processes at the base of apical tube; dorsolateralbands (Fig. 118B) very long, very thin; explusion hooks lost; ventromedian bands (Fig. 118B)
long, very thin. Parameres (Fig. 118B) moderately diverging posterolaterally at apical part, thick,each rounded apically; apical area very long, mesially with 7 to 8 short setae and apically with ashort seta.
Female: Eighth ventrite almost rounded posteriorly; gonocoxites (Fig. 118G) each with apicolateral tooth very long, very acute, apicolateral setae very long. Spermatheca (Fig. 118C) with
capsule very small, rounded apically; striped duct very long, extending proximad over the last
3rd turns, moderately thick to thick; duct very long, thin, with its anterior mass moderately
coiled; basal valve long, thin; basal duct short.
Biology and ecology. The beetles of S. bosatsu inhabit leaf litter heaped in the natural forestsof low mountainous to mountainous regions.
Remarks. Three species S. bosatsu, S. usitatus and S. tateoitoi seem to be allied on account of
their common possession of the peculiar endophallic copulatory tube with a pair of long, curved
lateral processes developed at the base of apical tube. Out of these three species, S. bosatsu is thesister species of S. usitatus, and it is separable from the latter species by the aedeagal median
lobe obtusely pointed at the apex, with its apical sclerotized area almost lost (Fig. 118B) and thespermatheca with its striped duct longer (Fig. 118C).
Etymology. The speciﬁc epithet of this species is named after the name of enlightened deity
who has vowed to remain in the world, Bosatsu.

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271

Stenus usitatus Naomi & Nomura(Figs. 119A–F, 135I)
Stenus usitatus Naomi & Nomura, 2015: 192.
Type material examined. Holotype: ♂(NMNST): Mizugatsuka, Susono City, Shizuoka Pref.,5. xi. 2000, S. Nomura leg. Paratypes: 1 ♂2 ♀ (NMNST), same data as holotype; 1 ♂, Mizugatsuka, Susono City., Shizuoka Pref., 26. iv. 2010, T. Watanabe leg.; 2 ♂2 ♀, same locality, 7. ix.
2010, T. Watanabe leg.; 2 ♂1 ♀, same locality, 24. xi. 2010, T. Watanabe leg.; 3 ♂7 ♀, same locality, 25. iv. 2011, T. Watanabe leg.; 1 ♂, same locality, 15. v. 2011, T. Watanabe leg.; 2 ♂1 ♀, same
locality, 27. x. 2011, T. Watanabe leg.; 1 ♂, same locality, 5. ix. 2012, T. Watanabe leg.; 1 ♀,same locality, 24. x. 2012, T. Watanabe leg.; 1 ♂, Susono City., Shizuoka Pref., 12. xi. 2003, I.
Ohshio leg.; 1 ♂, Gotenba, Shizuoka Pref., 1. xi. 2003, I. Ohshio leg.; 1 ♂1 ♀, Nishi-usuzuka,
Fujinomiya City., Shizuoka Pref., 7. x. 2007, T. Watanabe leg.
Distribution. Japan: Honshu (Shizuoka Pref.).
Redescription. Male and female: Body 3.5–3.9 mm (fore body 1.6–1.9 mm) in length. Body
moderately shining; head black; pronotum dark red to dark red near black; elytra reddish brownto dark brown or dark red near black; abdomen reddish brown to dark reddish brown or almost
black; labrum reddish brown; antennae and legs yellowish brown to reddish brown. Body with
punctures round to elliptical, small to moderately large, and also pronotum partially with subrugose punctures and elytra partially with large, subrugose punctures. Head moderately concave,with a pair of longitudinal-oblique furrows; antennae moderately long, very thin; pronotum withsurface slightly uneven to uneven, with a median longitudinal furrow indistinct or distinct; elytra
with surface uneven; abdomen subcylindrical, subparallel-sided; lateroventrites lost, tergoventrite sutures thin or very thin.
Male: Abdomen (Fig. 119E) modiﬁed with a ﬂat area or a very shallow depression on the
6th, a very shallow or shallow depression on the 7th, and a basal depression and also a moderately deep, subtriangular emargination on the 8th ventrite; 9th tergum (Fig. 119A) with ventral
apophyses very long; 9th ventrite (Fig. 119C) elongate, macrosetae usually very long, apicolateral teeth acutely pointed, apicolateral setae moderately long; 10th tergum (Fig. 119A) very shallowly emarginate posteriorly. Aedeagus (Fig. 119B) with median lobe distinctly narrowed behindthe middle, acutely pointed at apex; apical sclerotized area elongate-triangular in shape. Endophallus (Fig. 119B) with copulatory tube having basal chamber consisting of 2 very thin rods,
main tube with a pair of lateral processes at the base of apical tube, each lateral process distinctly
bent posteriorly near the base; dorsolateral bands very long, very thin; explusion hooks atrophied
into a pair of very small, very thin sclerites; ventromedian bands very long, very thin. Parameres(Fig. 119B) thick, each rounded apically, slightly curved posterolaterally at apical part; apicalarea very long, with a ventral ﬂap at base, mesially with 8 setae and apically with a seta.
Female: Eighth ventrite obtuse or acutely pointed posteromedially; gonocoxites (Fig. 119F)
each with apicomesial tooth developed, triangular, apicolateral tooth very long, acute, apicolateral setae moderately long. Spermatheca (Fig. 119D) with capsule very small, rounded apically;
striped duct moderately long, thick; duct very long, thin to thick, with its anterior mass strongly
coiled; basal valve moderately long, thin; basal sclerotized duct moderately long.
Biology and ecology. The beetles of S. usitatus inhabit leaf litter heaped in the natural forestsof low mountainous to mountainous regions.
Remarks. S. usitatus is the sister species of S. bosatsu, and it is separable from the latter spe-

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Fig. 119. Stenus usitatus Naomi & Nomura (Shizuoka). A, 9th and 10th terga of male; B, aedeagus; C, 9th ventrite of male; D, spermatheca; E, 7th and 8th ventrites of male; F, posterior part of gonocoxite. Scale 1: 0.2 mm
for A–C; 0.1 mm for D, F; scale 2: 0.2 mm for E.

The Steninae of Japan Part 3273

cies by the aedeagal median lobe acutely pointed at the apex, with its apical sclerotized area
elongate-triangular in shape (Fig. 119B) and the spermatheca with its striped duct shorter (Fig.
119D).
Stenus tateoitoi Naomi, Nomura & Puthz sp. nov.
(Fig. 120A–F)
Type material examined. Holotype: ♂ (KUMF), Gozaishi Spa, Yamanashi Pref., 16. viii.
1989, T. Ito leg. Paratypes: 1 ♂, same locality, 13. viii. 1989, T. Ito leg.; 2 ♀, same locality, 17.
viii. 1996, T. Ito leg.
Distribution. Japan: Honshu (Yamanashi Pref.).
Description. Male and female: Body 3.4–3.7 mm (fore body 1.7–1.8 mm) in length. Body
weakly shining; head black; pronotum and elytra dark red; abdomen dark reddish brown to darkbrown; labrum reddish brown; antennae and legs yellowish brown to reddish brown. Body with
punctures round to elliptical, small to moderately large, and also pronotum partially with coarse
to subrugose punctures and elytra partially with large, subrugose punctures. Head shallowly tomoderately concave, with a pair of longitudinal-oblique or longitudinal furrows (or depressions);
antennae short to moderately long, very thin; pronotum with surface slightly uneven to uneven,with a median longitudinal furrow very indistinct to indistinct; elytra with surface uneven; abdomen subcylindrical, subparallel-sided; lateroventrites lost, tergoventrite sutures very thin or obsolete.
Male: Abdomen (Fig. 120E) modiﬁed sometimes with a ﬂat area on the 6th, and usually witha ﬂat area or a very shallow depression on the 7th, and an arcuate broad emargination on the 8th
ventrite; 9th tergum (Fig. 120B) with ventral apophyses very long; 9th ventrite (Fig. 120D) withmacrosetae long, apicolateral teeth long, thin, very acute, apicolateral setae moderately long;
10th tergum (Fig. 120A) shallowly emarginate posteriorly. Aedeagus (Fig. 120C) with median
lobe bulbous in about basal 2/3, becoming strongly narrower apicad in about apical 1/3, narrowly
rounded apically; apical sclerotized area lost. Endophallus (Fig. 120C) with copulatory tube
large, main tube with apical tube attenuate, moderately curved, with a pair of thin, strongly
curved lateral processes at base; expulsion hooks lost; ventromedian bands moderately long,moderately broad, with their basal bands almost fused. Parameres (Fig. 120C) moderately
diverging posteriorly in apical part, each obtusely pointed at apex; apical area long, mesially with
7 to 8 setae and apically with a moderately long seta.
Female: Eighth ventrite obtuse posteromedially; gonocoxites (Fig. 120F) each with apicolateral tooth very long, acute. Spermatheca (Fig. 120A) with capsule short, obtuse at apex; striped
duct very long, thin to moderately broad; duct very long, thin, with its anterior mass strongly,
regularly coiled; gland small, fusiform, with opening located on the duct a little proximal fromthe last 4th turn; basal valve short; basal duct very short; basal pouch conical.
Biology and ecology. The beetles of S. tateoitoi inhabit leaf litter heaped in the natural forestsof a mountainous region.
Remarks. S. tateoitoi is allied to S. bosatsu and S. usitatus, but it is separable from the latter2 species by the aedeagal median lobe broader, with its apical sclerotized area lost (Fig. 120C),
the copulatory tube with a pair of longer, strongly curved, lateral processes (Fig. 120C), and theparamere with its apical area shorter (Fig. 120C).
Etymology. This new species is named after Mr. Tateo Ito (Kyoto) who studies the Staphylinidae in Japan.

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Fig. 120. Stenus tateoitoi Naomi, Nomura & Puthz sp. nov. (Yamanashi: Gozaishi Spa). A, spermatheca; B, 9th
and 10th terga of male; C, aedeagus; D, 9th ventrite of male; E, 7th and 8th ventrites of male; F, posterior partof gonocoxite. Scale 1: 0.1 mm for A, F, 0.2 mm for B–D; scale 2: 0.3 mm for E.

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275

Incertae sedis
Stenus bifurcatus Naomi(Figs. 121A–G, 135J)
Stenus bifurcatus Naomi, 2011: 47; Naomi & Puthz, 2013: 144.
Type material examined. Holotype: ♂ (CBM), Shinodachi, Fujiwara, Inabe-gun, Mie Pref.,12. xi. 1998, H. Ichihashi leg. Paratypes, 1 ♂, Miyazuma-kyo, Yokkaichi City, Mie Pref., 23. ix.
1987, A. Amagasu leg.; 3 ♂6 ♀, Gonyu-dani, Hokusei-cho, Mie Pref., 29. xii. 1977, A. Amagasu
leg.; 1 ♂1 ♀, Sakamoto-dani, Fujiwara-cho, Mie Pref., 3. ix. 1994, H. Yokozeki leg.
Distribution. Japan: Honshu (Mie Pref.).
Redescription. Male and female: Body 2.6–3.7 mm (fore body 1.3–1.8 mm) in length. Body
moderately shining; head dark red to black, with clypeal or clypeofrontal area reddish brown;
pronotum and elytra reddish orange to reddish brown or dark red; abdomen reddish brown todark red or dark red near black; labrum reddish brown to dark red; antennae and legs yellowish
brown to reddish brown. Body with punctures round to elliptical, small to moderately large, andalso pronotum partially with coarse punctures and elytra partially with large, subrugose punctures. Head shallowly to moderately concave, with a pair of longitudinal-oblique furrows or
depressions; antennae short, very thin; pronotum with surface slightly uneven to uneven, with a
median longitudinal furrow hardly developed to very indistinct or indistinct; elytra with surface
slightly uneven to uneven; abdomen subcylindrical, slightly tapering posteriorly to subparallelsided; lateroventrites and tergoventrite sutures lost.
Male: Abdomen modiﬁed with a bell- (Fig. 121G) or an elongate-bell-shaped, almost ﬂatarea on the 7th, and a broad, arcuate, shallow emargination on the 8th ventrite; 9th tergum (Fig.
121A) with ventral apophyses moderately long; 9th ventrite (Fig. 121A) with apicolateral teeth
moderately long, acute, apicolateral setae long; 10th tergum (Fig. 121A) very shallowly emarginate posteromedially. Aedeagus (Fig. 121C) with median lobe moderately broad, bifurcate apically with a pair of large, bluntly pointed protrusions which weakly diverge posteriorly. Endophallus (Fig. 121C) with copulatory tube having basal chamber ovoidal, main tube moderately
thick, slightly (Fig. 121D) or strongly (Fig. 121C) curved, pointed at apex; dorsolateral bands
thin; expulsion hooks slightly asymmetrical, each with anterior plate acutely pointed at anterior
tip, posterior plate turning posterolaterally behind the middle; ventromedian bands moderately
long, extremely broad. Parameres (Fig. 121C) slender, very thin, each very acutely pointed atapex; apical area moderately long, mesially with 6 setae.
Female: Eighth ventrite obtuse posteromedially; gonocoxites (Fig. 121F) each with apicolateral tooth long, pointed, apicolateral setae very long. Spermatheca (Fig. 121E) with capsule wellrounded apically; striped duct moderately long, moderately thick; duct moderately long, moderately broad, almost loosely coiled; basal valve short; basal duct moderately long; basal pouch
conical, membranous.
Biology and ecology. The beetles of S. bifurcatus inhabit leaf litter heaped in the natural forests of lowlands to low mountainous regions.
Remarks. S. bifurcates is a very peculiar species due to the possession of the unique aedeagal
median lobe with a strongly bifurcate apex (Fig. 121C). Thus, at present there seems to be no
species which is closely allied to S. bifurcates in the rufescens-subgr. S. bifurcates is thus easily
separable from the other species of the rufescens-subgr. by the aedeagal median lobe with a276

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Fig. 121. Stenus bifurcatus Naomi (Mie: A–C, Miyazuma, D–F, Gonyudani, G, Fujiwara). A, 9th and 10th tergaof male; B, 9th ventrite of male; C, aedeagus; D, copulatory tube; E, spermatheca; F, gonocoxite; G, 7th to 8th
ventrites of male. Scale 1: 0.2 mm for A, 0.1 mm for E, F; scale 2: 0.1 mm for B, C; scale 3: 0.1 mm for D;
scale 4: 0.2 mm for G.

The Steninae of Japan Part 3277

strongly bifurcate apex.
Addition of 8 species to the asyura-group
The following 8 species are added to the kasumi-subgroup of asyura-group, which is treatedin the Part 2 (Naomi et al., 2019).
syaca Naomi, 1989b Distribution: Japan (Honshu).
shuheii Naomi, 1990a Distribution: Japan (Honshu).
＝ambiguellus Naomi, 1998.
asiuensis Naomi, Nomura & Puthz sp. nov. Distribution: Japan (Honshu).
fukuimontium Puthz, 1993a Distribution: Japan (Honshu).
sasajiiellus Naomi, Nomura & Puthz sp. nov. Distribution: Japan (Honshu).
tumifactus Naomi, 2015 Distribution: Japan (Honshu).
leehermani Naomi, 2015a Distribution: Japan (Honshu).
utan Naomi, 1998a Distribution: Japan (Honshu).
Stenus syaca Naomi(Figs. 122A–H, 135K)
Stenus syaca Naomi, 1989b: 46; Herman: 2001: 2410; Naomi & Puthz, 2013: 144.
Type material examined. Holotype: ♂ (KUF), Rokuroshi, Ohno City, Fukui Pref., 20–23. vii.
1980, H. Sasaji leg.
Other material examined. [HONSHU]: 1 ♂1 ♀, Senami, Ishikawa Pref., 17. v. 1964, Y.
Hayashi leg.
Distribution. Japan: Honshu (Ishikawa and Fukui Prefs.).
Redescription. Male and female: Body 3.8–4.0 mm (fore body 1.7–1.8 mm) in length. Body
weakly or moderately shining; head black; pronotum and elytra dark red; abdomen dark red todark brown; labrum reddish brown to dark red; antennae and legs reddish brown. Body with
punctures round to elliptical, small to moderately large, and also pronotum partially with coarse
to subrugose punctures and elytra partially with large, subrugose punctures. Head moderately
concave, with a pair of longitudinal-oblique furrows; antennae moderately long, thin; pronotumwith surface slightly uneven to uneven, with a median longitudinal furrow very indistinct; elytra
with surface uneven; abdomen subcylindrical, subparallel-sided; lateroventrites lost, tergoventral
sutures very thin, indistinct.
Male: Abdomen (Fig. 122G) modiﬁed with an arcuate emargination on the 8th ventrite; 9th
tergum (Fig. 122B) with ventral apophyses moderately long; 9th ventrite (Fig. 122D) with apicolateral teeth long, thin, very acute, apicolateral setae slightly long; 10th tergum (Fig. 122B)
entire. Aedeagus (Fig. 122A) with median lobe elongate, broad and pentagonal at apex. Endophallus (Fig. 122A) with copulatory tube (Fig. 122E) with basal chamber comprising paired rodsof diﬀerent length, main tube moderately long, attenuate; dorsolateral bands very long, thin;
expulsion hooks (Fig. 122H) each tadpole-shaped, with an oblique, thin muscle attachment at theanterolateral part of posterior plate; ventromedian bands moderately long, moderately broad.
Parameres (Fig. 122A) each acutely pointed at apex; apical area long, thick at base, narrowing
apicad, mesially with a setal tuft at base and 6 setae of various length in about apical 3/4.

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Fig. 122. Stenus syaca Naomi (Fukui: Ohno). A, aedeagus; B, 9th and 10th terga of male; C, spermatheca; D, 9th
ventrite of male; E, copulatory tube; F, posterior part of gonocoxite; G, posterior part of 8th ventrite of male;H, endophallic expulsion hooks. Scale 1: 0.1 mm for A, 0.05 mm for H; scale 2: 0.2 mm for B, D, G, 0.1 mm
for C, E, F.

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279

Female: Eighth ventrite obtuse posteomedially; gonocoxites (Fig. 122F) each with apicolateral tooth long, very acute, apicolateral setae very long. Spermatheca (Fig. 122C) with capsulehalf-ovoidal; striped duct short, thick; duct slightly short, thick, coiled with 4 turns; gland moderately large, spherical, with opening located on the lateral side of the 3rd turn; basal valve short;basal duct sclerotized, moderately long and thick; basal pouch almost bowl-shaped.
Biology and ecology. The beetles of S. syaca inhabit leaf litter heaped in the natural forestsof low mountainous regions.
Remarks. S. syaca is allied to S. hayashii Puthz, 2003, but it is separable from the latter species by the aedeagal median lobe with its apical sclerotized area lost (Fig. 122A), the copulatory
tube with its main tube thinner and attenuate (Fig. 122E), the endophallic expulsion hook almost
tadpole-shaped (Fig. 122H), and the paramere with its apical area longer and thicker at base.
Etymology. The speciﬁc epithet of this species is derived from the Japanese name of Buddha,
Syaca.
Stenus shuheii Naomi(Fig. 123A–H)
Stenus shuheii Naomi, 1990a: 2; Herman, 2001: 2388; Naomi & Puthz, 2013: 143.
Stenus ambiguellus Naomi, 1998: 101; Herman, 2001: 2053; Naomi & Puthz, 2013: 142; Naomi,
2015: 8 (synonym of S. shuheii).
Type material examined. Holotype of S. shuheii: ♂ (KUF), Onzui Valley, Hyogo Pref., 6. vi.
1984. S. Nomura leg.
Holotype of S. ambiguellus: ♂ (CBM), Onzui Valley, Hyogo Pref., 6. vi. 1984. S. Nomura
leg.
Other material examined. [HONSHU]: 1 ♀, Onzui, Hyogo Pref., 15. ix. 1992, T. Ito leg.; 1 ♂,Hanase, Kyoto Pref., 4. ix. 1987, T. Ito leg.
Distribution. Japan: Honshu (Kyoto and Hyogo Prefs.).
Redescription. Male and female: Body 4.3–4.8 mm (fore body 2.1–2.3 mm) in length. Body
moderately to strongly shining; head black; pronotum and elytra dark red; abdomen dark reddish
brown to dark brown; labrum reddish brown; antennae and legs yellowish brown to reddish
brown. Body with punctures round to elliptical, small to moderately large, and also pronotum
partially with coarse to subrugose punctures and elytra partially with large, subrugose punctures.
Head moderately concave, with a pair of longitudinal-oblique or mesially-curved furrows; antennae short, very thin; pronotum with surface almost even to uneven, with a median longitudinalfurrow very indistinct to almost distinct; elytra with surface uneven; abdomen subcylindrical,
slightly tapering posteriorly; lateroventrites lost, tergoventral sutures very thin or almost lost.
Male: Abdomen (Fig. 123B) modiﬁed with a ﬂat area on the 5th, a shallow depression on the
6th, a moderately deep depression on the 7th, and a subtriangular, moderately deep emarginationon the 8th ventrite; 9th tergum (Fig. 123A) with ventral apophyses moderately long; 9th ventrite(Fig. 123C) with apicolateral teeth long, almost acute, apicolateral setae moderately long; 10th
tergum (Fig. 123A) very shallowly emarginate posteriorly. Aedeagus (Fig. 123D) with median
lobe well-rounded at apicolateral corners, acutely pointed at apex; apical sclerotized area small,narrow, subtriangular. Endophallus (Fig. 123D) with copulatory tube having main tube baculiform, once distinctly bent left behind the middle, with 2 subtransparent ﬂaps (Fig. 123G); dorsolateral bands very thin; expulsion hooks elongate, each with posterior plate angulate at postero-280

Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

Fig. 123. Stenus shuheii Naomi (Kyoto, A, B, Hanase; Hyogo, C–H, Onzui). A, 9th and 10th terga of male; B, 6th
to 8th ventrites of male; C, 9th ventrite of male; D, aedeagus; E, spermatheca; F, posterior part of 10th tergumof female; G, copulatory tube; H, posterior part of gonocoxite. Scale 1: 0.2 mm for A, C, D, F, 0.1 mm for E,
G, H; scale 2: 0.3 mm for B.

The Steninae of Japan Part 3281

lateral corner; ventromedian bands long, broad. Parameres (Fig. 123D) each pointed at apex;
apical area moderately long, distinctly swollen and angulate mesially at base, mesially also with17 to 19 setae of diﬀerent length.
Female: Eighth ventrite obtusely pointed posteromedially; 10th tergum (Fig. 123F) almost
acute posteromedially; gonocoxites (Fig. H) each with apicolateral tooth very long, very acute,apicolateral setae long. Spermatheca (Fig. 123E) with capsule almost rounded apically; striped
duct short, thick; duct moderately long, moderately thick to thick, almost regularly coiled; basal
valve very short; basal duct moderately long.
Biology and ecology. The beetles of S. shuheii inhabit leaf litter heaped in the natural forestsof mountainous regions.
Remarks. S. shuheii is allied to S. asiuensis and S. fukuimontium, but it is separable fromthe latter 2 species by the aedeagal median lobe much more rounded apicolaterally (Fig. 123D),
the copulatory tube with its main tube once distinctly bent behind the middle (Fig. 123G), andthe endophallic expulsion hook with its posterior plate angulate at the posterolateral corner (Fig.
123D). S. shuheii is also allied to S. hayashii, but it is separable from the latter species by theaedeagal median lobe with its apical sclerotized area narrower (Fig. 123D), the copulatory tube
with its main tube once distinctly bent left behind the middle (Fig. 123G), and the endophallic
expulsion hook with its anterior plate narrower (Fig. 123D).
Etymology. This species is named after the second author of this paper, Shûhei Nomura.
Stenus asiuensis Naomi, Nomura & Puthz sp. nov.
(Figs. 124A–G, 135 L)
Type material. Holotype: ♂ (NSMT-I-C-200325 in NMNST), Ashiu, Kyoto Pref., 12. vi.
1999, T. Ito leg. Paratypes: 8 ♂2 ♀ (KUMF, cP), same data as holotype.
Distribution. Japan: Honshu (Kyoto Pref.).
Description. Male and female: Body 4.5–4.8 mm (fore body 2.0–2.3 mm) in length. Body
moderately shining; head black; pronotum and elytra pale reddish brown to reddish brown; abdomen dark reddish brown to dark brown; labrum reddish brown; antennae and legs pale reddish
brown. Body with punctures round to ovoidal, small to moderately large, and also pronotum partially with coarse to subrugose punctures and elytra partially with large, subrugose punctures.
Head moderately concave, with a pair of longitudinal-oblique or almost longitudinal furrows;
antennae short to moderately long, very thin; pronotum with surface slightly uneven to uneven,with a median longitudinal furrow indistinct; elytra with surface uneven; hind tarsi each with 4thtarsomere strongly bilobed, about 0.7 to a little more times as long as the 5th; abdomen subcylindrical, subparallel-sided; lateroventrites lost, tergoventral sutures very thin, superﬁcial or almost
lost.
Male: Abdomen (Fig. 124G) modiﬁed with a very shallow depression on the 6th, a moderately deep depression on the 7th, and a slightly small emargination on the 8th ventrite; 9th tergum (Fig. 124A) with ventral apophyses long; 9th ventrite (Fig. 124B) with macrosetae long,apicolateral teeth long, thin, acute, apicolateral setae moderately long; 10th tergum (Fig. 124A)
shallowly emarginate posteriorly. Aedeagus (Fig. 124D) with median lobe moderately broad,narrowly rounded at apicolateral corners, acutely pointed at apex; apical sclerotized area slightly
narrow, almost triangular. Endophallus (Fig. 124D) with copulatory tube long, with basal chamber almost ovoidal, main tube elongate-S-shaped, laterally with a moderately long projection (orﬂap) which is rounded apically; expulsion hooks (Fig. 124F) robust, moderately broad to broad,282

Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

Fig. 124. Stenus asiuensis Naomi, Nomura & Puthz sp. nov. (Kyoto: Ashiu). A, 9th and 10th terga of male; B, 9th
ventrite of male; C, 6th to 8th ventrites of male; D, aedeagus; E, spermatheca; F, endophallic expulsion hooks;
G, posterior part of gonocoxite. Scale 1: 0.2 mm for A, B, D, 0.1 mm for E–G; scale 2: 0.3 mm for C.

The Steninae of Japan Part 3283

each with posterior plate arcuately twice emarginate laterally; ventromedian bands moderately
long, moderately broad. Parameres (Fig. 124D) robust, each very acutely pointed at apex; apicalarea long, mesially swollen and angulate at base, mesially also with a tuft of 4 to 5 long setae atbase and 7 shorter setae behind the basal tuft of setae.
Female: Eighth ventrite almost obtusely pointed posteromedially; gonocoxites (Fig. 124G)
each with apicolateral tooth very long, acute, apicolateral setae very long. Spermatheca (Fig.
124E) with capsule not developed; striped duct very long, thick, wholly covered regularly withvery thin, dense transverse stripes; duct moderately long, moderately thick; gland subovoidal,
with opening located on the duct near the last 2nd turn; basal valve short; basal duct long.
Biology and ecology. The beetles of S. asiuensis inhabit leaf litter heaped in the natural forests of a mountainous region.
Remarks. S. asiuensis is allied to S. fukuimontium, but it is separable from the latter species
by the aedeagal median lobe broader in the posterior part (Fig. 124D), the copulatory tube withits main tube elongate-S-shaped (Fig. 124D), the endophallic expulsion hook broader, with its
posterior plate arcuately twice emarginate laterally (Fig. 124F), and the paramere with its apicalarea shorter (Fig. 124D).
Etymology. The speciﬁc epithet of this new species is derived from the name of type locality,
Ashiu in Kyoto.
Stenus fukuimontium Puthz(Fig. 125A–G)
Stenus fukuimontium Puthz, 1993a: 183; Herman, 2001: 2189; Naomi & Puthz, 2013: 142.
Type material examined. Holotype: ♀ (CBM), Arashi, Fukui Pref., 16. v. 1965, H. Sasaji leg.
Other material examined. [HONSHU]: 5 ♂5 ♀, Kengaiwa, Mt. Hakusan, Ishikawa Pref., 3.
x. 2002, S. Nomura leg.
Distribution. Japan: Honshu (Ishikawa and Fukui Prefs.).
Redescription. Male and female: Body 4.6–5.5 mm (fore body 2.0–2.5 mm) in length. Body
moderately shining; head black, with clypeofrontal area dark red to dark reddish brown; pronotum and elytra yellowish brown to reddish brown or dark reddish brown; abdomen dark brown toalmost black; labrum reddish brown; antennae and legs yellowish brown to pale reddish brown.
Body with punctures round to ovoidal, small to moderately large, and also pronotum partiallywith subrugose punctures and elytra partially with large, subrugose punctures. Head moderately
concave, with a pair of almost longitudinal furrows; antennae short to moderately long, very thin;pronotum with surface almost even to uneven, with a median longitudinal furrow very indistinct
to indistinct; elytra with surface uneven; abdomen subcylindrical, subparallel-sided; lateroventrites and tergoventrite sutures lost.
Male: Abdomen (Fig. 125E) modiﬁed with a ﬂat area on the 5th, a moderately deep depression on the 6th, a moderately deep, anteromedian and a deep posteromedian depresssions on the
7th, and a small, subtriangular emargination on the 8th ventrite; 9th tergum (Fig. 125A) withventral apophyses long; 9th ventrite (Fig. 125D) with macrosetae long, apicolateral teeth long,thin, very acute, apicolateral setae slightly short; 10th tergum (Fig. 125A) almost rounded posteriorly. Aedeagus (Fig. 125C) with median lobe strongly narrowing apicad in the apical 1/2,
acutely pointed at apex; apical sclerotized area small, narrow, almost triangular. Endophallus(Fig. 125C) with copulatory tube with basal chamber subovoidal, main tube nearly Z-shaped,

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Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

Fig. 125. Stenus fukuimontium Puthz (Ishikawa). A, 9th and 10th terga of male; B, spermatheca; C, aedeagus; D,
9th ventrite of male; E, 6th to 8th ventrites of male; F, posterior part of gonocoxite; G, endophallic expulsion
hooks. Scale 1: 0.2 mm for A, C, D, 0.1 mm for B, F, G; scale 2: 0.3 mm for E.

The Steninae of Japan Part 3285

having a pointed projection (or ﬂap) near the 1st turn, distinctly angulate at the 2nd turn; expulsion hooks (Fig. 125G) each with anterior plate almost rounded at anterior tip, posterior plate
weakly bisinuate laterally; ventromedian bands (Fig. 125C) moderately long, moderately broad.
Parameres (Fig. 125C) robust, each very acutely pointed at apex; apical area very long, mesiallyswollen and angulate at base, mesially with a tuft of 5 to 6 setae at base and 8 to 10 setae of various length behind the basal tuft of setae.
Female: Eighth ventrite obtuse posteromedially; gonocoxites (Fig. 125F) each with apicolateral tooth very long, thin, very acute, apicolateral setae very long. Spermatheca (Fig. 125B) with
capsule almost rounded apically; striped duct moderately long, thick; duct moderately long,thick; basal valve short; basal duct moderately long.
Biology and ecology. The beetles of S. fukuimontium inhabit leaf litter heaped in the naturalforests of mountainous to high mountainous regions.
Remarks. S. fukuimontium is allied to S. asiuensis, but it is separable from the latter species
by the aedeagal median lobe narrower in the apical part (Fig. 125C), the copulatory tube with its
main tube nearly Z-shaped (Fig. 125C), the endophallic expulsion hook narrower, with its posterior plate weakly bisinuate laterally (Fig. 125G), and the paramere with its apical area longer(Fig. 125C),
Stenus sasajiiellus Naomi, Nomura & Puthz sp. nov.
(Fig. 126A–F)
Type material examined. Holotype: ♂ (NSMT-I-C-200326 in NMNST), Ibigawa-cho, Gifu
Pref., 16. v. 2010, K. Toyoshima leg.
Distribution. Japan: Honshu (Gifu Pref.).
Description. Male: Body 4.5 mm (fore body 2.1 mm) in length. Body moderately shining;head black; pronotum and elytra reddish brown to dark red; abdomen dark reddish brown;
labrum reddish brown; antennae and legs reddish brown. Body with punctures round to almost
round, small to moderately large, and also pronotum partially with subrugose punctures and elytra partially with large, subrugose punctures. Head moderately concave, with a pair of longitudinal-oblique furrows; antennae moderately long, very thin; pronotum with surface uneven, with a
median longitudinal furrow indistinct; elytra with surface uneven; abdomen subcylindrical, subparallel-sided; lateroventrites and tergoventrite sutures lost.
Abdomen (Fig. 126F) modiﬁed with a shallow depression on the 6th, a moderately deep
depression on the 7th, and a slightly small, subtriangular emargination on the 8th ventrite; 9th
tergum (Fig. 126A) with ventral apophyses very long; 9th ventrite (Fig. 126E) with apicolateral
teeth moderately long, thin, very acute, apicolateral setae long; 10th tergum (Fig. 126A) entire.
Aedeagus (Fig. 126B) with median lobe obtusely angulate at apicolateral corners, obtuse at apex;
apical sclerotized area subtriangular. Endophallus with copulatory tube (Fig. 126C) long, withbasal chamber large, main tube once distinctly curved a little anteriorly from the basal 1/3, withapical tube moderately curved, and also laterally with a moderately long projection which isrounded apically; expulsion hooks (Fig. 126D) robust, broad, each with anterior plate divided
antero-posteriorly into 2 subplates, almost truncate at anterior tip, posterior plate moderately
expanding and minutely serrate laterally behind the middle. Parameres (Fig. 126B) each weakly
turning laterally behind the base of apical area, obtusely pointed at apex; apical area long, mesially swollen and angulate at base, mesially also with a tuft of 3 to 4 long setae at base and 9 to 11
setae of diﬀerent length behind the basal tuft of setae.

286

Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

Fig. 126. Stenus sasajiiellus Naomi, Nomura & Puthz sp. nov. (Gifu: Ibigawa). A, 9th and 10th terga of male; B,
aedeagus; C, copulatory tube; D, endophallic expulsion hooks; E, 9th ventrite of male; F, 6th to 8th ventrites
of male. Scale 1: 0.2 mm for A, B, E, 0.1 mm for C, D; scale 2: 0.3 mm for F.

The Steninae of Japan Part 3

287

Female: Unknown.
Biology and ecology. The beetle of S. fukuimontium inhabits leaf litter heaped in the naturalforest of a low mountainous region.
Remarks. S. sasajiiellus is allied to S. tumifactus, but it is separable from the latter species by
the copulatory tube longer and thinner, with its basal portion thinner (Fig. 126C) and the endophallic expulsion hook with its posterior plate moderately expanding and minutely serrate laterally behind the middle (Fig. 126D).
Etymology. This new species is named after the late Dr. Hiroyuki Sasaji (Fukui University)
who studied the Coccinellidae and some other Coleopteran families in Japan.
Stenus tumifactus Naomi(Fig. 127A–I)
Stenus tumifactus Naomi, 2015: 8.
Type material examined. Holotype: ♂ (CBM), Samegai Valley, Samegai-cho, Shiga Pref., 5.
vi. 1997, S. Nomura leg. Paratypes: 2 ♀, same data as holotype.
Other material examined. [HONSHU]: 6 ♀5 ♀, Shinodate, Fujiwara-cho, Inabe City, Mie
Pref., 20. xii. 1998, H. Yokozeki leg.
Distribution. Japan: Honshu (Shiga and Mie Prefs.).
Redescription. Male and female: Body 4.0–4.5 mm (fore body 1.9–2.1 mm) in length. Body
moderately shining; head black; pronotum and elytra reddish brown to dark red; abdomen dark
reddish brown to dark brown; labrum reddish brown; antennae and legs yellowish brown to reddish brown. Body with punctures round to ovoidal, small to moderately large, and also pronotum
partially with subrugose punctures and elytra partially with large, subrugose punctures. Headmoderately concave, with a pair of longitudinal-oblique or almost longitudinal furrows; antennae
short to moderately long, very thin; pronotum with surface slightly uneven, with a median longitudinal furrow very indistinct; elytra with surface uneven; abdomen subcylindrical, subparallelsided; lateroventrites and tergoventrite sutures lost.
Male: Abdomen (Fig. 127C) modiﬁed with a ﬂat area on the 6th, a shallow depression on the
7th, and a small, nearly triangular emargination on the 8th ventrite; 9th tergum (Fig. 127A) withventral apophyses long; 9th ventrite (Fig. 127B) with macrosetae long, apicolateral teeth long,thin, very acute, apicolateral setae moderately long; 10th tergum (Fig. 127A) very weakly emarginate posteromedially. Aedeagus (Fig. 127F) with median lobe elongate (Fig. 127F) or almost
elongate-ovoidal in shape, well-rounded at apicolateral corners, almost acutely pointed at apex;
apical sclerotized area (Fig. 127F) subtriangular. Endophallus with copulatory tube (Fig. 127D)
having the basal chamber and the basal tube of main tube fused to be elongate-subovoidal inshape, without basal constriction, main tube very thick at base, beak-shaped at apex, laterallywith a moderately large projection which is almost rounded ; expulsion hooks (Fig. 127I) large,
with anterior plate divided antero-posteriorly into 2 subplates, posterior plates almost contiguous
mesially, subparallel-sided behind the base; ventromedian bands (Fig. 127E) each broad at posterior rim, becoming narrower anteriad; parameres (Fig. 127F) each pointed at apex; apical area
long to very long, hardly or weakly swollen at base, mesially with a tuft of 3 to 4 setae at baseand 4 to 8 setae behind the basal tuft of setae.
Female: Eighth ventrite obtusely pointed posteromedially; gonocoxites (Fig. 127H) eachwith apicolateral tooth very long, very acute, apicolateral setae very long. Spermatheca (Fig.

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Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

Fig. 127. Stenus tumifactus Naomi (Shiga: Samegai). A, 9th and 10th terga of male; B, 9th ventrite of male; C,
7th and 8th ventrites of male; D, copulatory tube; E, endophallic ventromedian bands; F, aedeagus; G, spermatheca; H, posterior part of gonocoxite; I, endophallic expulsion hooks. Scale 1: 0.2 mm for A, B, F, 0.1 mm for
D, E, G–I; scale 2: 0.3 mm for C.

The Steninae of Japan Part 3289127G) with capsule very long, rounded apically; striped duct slightly short, thick; duct moderately long, moderately thick to thick, coiled with 6 or 7 turns; basal valve short; basal duct moderately long; basal pouch conical, membranous.
Biology and ecology. The beetles of S. tumifactus inhabit leaf litter heaped in the natural forests of low mountainous regions.
Remarks. S. tumifactus is allied to S. sasajiiellus, but it is separable from the latter species by
the copulatory tube shorter, with its basal portion thicker (Fig. 127D) and the endophallic expulsion hooks with their posterior plates almost contiguous mesially and subparallel-sided behindthe base (Fig. 127I).
Stenus leehermani Naomi(Fig. 128A–I)
Stenus leehermani Naomi, 2015a: 220.
Type material examined. Holotype: ♂ (EUMM), Kanmuri Pass, Gifu Pref., 27. vii. 1995, M.
Sato leg. Paratypes: 4 ♀ (EUMM), same data as holotype; 1 ♂2 ♀, same data as holotype.
Distribution. Japan: Honshu (Gifu Pref.).
Redescription. Male and female: Body 4.5–4.8 mm (fore body 2.2–2.3 mm) in length. Headweakly shining; head black, with clypeofrontal area dark red near black; pronotum and elytra
reddish brown to dark red; abdomen dark red to dark reddish brown; labrum reddish orange to
reddish brown; antennae and legs yellowish brown to reddish brown. Body with punctures roundto elliptical, small to moderately large, and also pronotum partially with subrugose punctures andelytra partially with large, subrugose punctures. Head moderately concave, with a pair of longitudinal-oblique furrows; antennae moderately long, very thin; pronotum with surface slightly
uneven to uneven, with a median longitudinal furrow very indistinct to indistinct; elytra with surface uneven; abdomen subcylindrical, subparallel-sided; lateroventrites and tergoventrite sutures
lost.
Male: Abdomen (Fig. 128F) modiﬁed with a very shallow depression on the 6th, a shallow
depression on the 7th, an arcuate, moderately broad, moderately deep emargination on the 8th
ventrite (Fig. 128H); 9th tergum (Fig. 128D) with ventral apophyses long; 9th ventrite (Fig.
128E) with macrosetae moderately long, apicolateral teeth long, very acute, apicolateral setae
short; 10th tergum (Fig. 128D) almost rounded posteriorly. Aedeagus (Fig. 128B) with median
lobe broadly rounded at apicolateral corners, almost acutely pointed at apex; apical sclerotizedarea small, narrow, subtriangular. Endophallus with copulatory tube (Fig. 128A) robust, withbasal chamber very large, indistinctly constricted at base, main tube very thick, strongly narrowing apicad behind the middle but twice weakly constricted on its way, beak-shaped at apex;
expulsion hooks (Fig. 128G) broad, each with anterior plate almost acutely pointed at anterior
tip, posterior plate slightly projecting laterally at posterolateral corner, subtruncate posteriorly;
ventromedian bands moderately long, broad. Parameres (Fig. 128B) each almost obtusely
pointed apically; apical area long, distinctly swollen and angulate mesially at base, mesially alsowith a tuft of 5 to 6 setae at base and 5 to 6 setae behind the middle.
Female: Eighth ventrite almost rounded posteriorly; gonocoxites (Fig. 128I) each with apicolateral tooth long, very acute, apicolateral setae very long. Spermatheca (Fig. 128C) with capsulevery small, rounded at apex; striped duct slightly short, moderately thick; duct moderately long,moderately thick to thick, coiled with 5 turns; basal valve very short; basal duct moderately long.

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Fig. 128. Stenus leehermani Naomi (Gifu: Kanmuri Pass). A, copulatory tube; B, aedeagus; C, spermatheca; D,
9th and 10th terga of male; E, 9th ventrite of male; F, 6th and 7th ventrites of male; G, endophallic expulsion
hooks; H, posterior part of 8th ventrite of male; I, posterior part of gonocoxite. Scale 1: 0.1 mm for A, C, G, I,
0.2 mm for B, E, H; scale 2: 0.2 mm for D; scale 3: 0.3 mm for F.

The Steninae of Japan Part 3291

Biology and ecology. The beetles of S. leehermani inhabit leaf litter heaped in the natural forests of a mountainous region.
Remarks. S. leehermani is allied to S. sasajiiellus and S. tumifactus, but it is separable fromthe latter 2 species by the aedeagal median lobe with its apical sclerotized area narrower andsmaller (Fig. 128B), the copulatory tube thicker, without any lateral projection (Fig. 128A), andthe endophallic expulsion hook shorter, with its anterior plate almost acutely pointed at anteriortip (Fig. 128G).
Etymology. This species is named after Dr. Lee Herman (American Museum of Natural History) who studies some subfamilies of the Staphylinidae world-wide and also compiled the Catalog of Staphylinidae in 2001.
Stenus utan Naomi(Fig. 129A–G)
Stenus utan Naomi, 1998a: 388; Herman, 2001: 2427; Naomi & Puthz, 2013: 142.
Type material examined. Holotype: ♂ (CBM), Kamiyama, Hakone, Kanagawa Pref., 25. v.
1974, Y. Shibata leg. Paratypes: 1 ♂1 ♀, same data as holotype.
Other material examined. [HONSHU]: 1 ♂, Mt. Byobu, Hakone, Kanagawa Pref., 14. iv.
2003, T. Watanabe leg.; 1 ♂, Mt. Amagi-Manjiro, Naha-Izu-cho, Shizuoka Pref., 2. xi. 2003, I.
Ohshio leg.; 4 ♂6 ♀, Mt. Amagi-Manzaburo, Izu-Peninsula, Shizuoka Pref., 12. xi. 2000, S.
Nomura leg.; 5 ♂5 ♀, Ikadaba, Izu City, Shizuoka Pref., 3. ix. 2006, Y. Kaneko leg.
Distribution. Japan: Honshu (Kanagawa and Shizuoka Prefs.).
Redescription. Male and female: Body 3.4–4.1 mm (fore body 1.5–2.0 mm) in length. Body
moderately shining; head and abdomen black; pronotum and elytra dark red; labrum dark red;antennae and legs reddish brown to brown. Body with punctures round to almost round, small tomoderately large, and also pronotum partially with subrugose punctures and elytra partially withlarge, subrugose punctures. Head shallowly to moderately concave, with a pair of longitudinaloblique furrows; antennae short to moderately long, very thin to thin; pronotum with surface
slightly uneven, with a median longitudinal furrow indistinct; elytra with surface uneven tostrongly uneven, each with a basal keel and also with an indistinct, large fovea on each side ofbasal keel; abdomen subcylindrical, subparallel-sided; lateroventrites and tergoventrite sutures
lost.
Male: Abdomen (Fig. 129E) modiﬁed with a nearly semicircular ﬂat area on the 7th, and abroad, shallow emarginatiom on the 8th ventrite; 9th tergum (Fig. 129C) with ventral apophyses
moderately long; 9th ventrite (Fig. 129B) with macrosetae long, apicolateral teeth long, acute,apicolateral setae long; 10th tergum (Fig. 129C) very shallowly emarginate posteriorly. Aedeagus(Fig. 129A) with median lobe becoming broader apicad, and then gently rounded and broadest at
apicolateral corners, pointed at apicomedian part, ventrally covered sparsely with small pores;
apical sclerotized area subriangular, basally with a pentagonal notch. Endophallus (Fig. 129A)
with copulatory tube moderately long, moderately curved; expulsion hooks (Fig. 129F) moderately broad; dorsolateral bands long, thin; ventromedian bands moderately long, moderately
broad. Parameres (Fig. 129A) long, each pointed at apex, with pedicel covered sparsely withsmall pores at the middle; apical area long, weakly swollen mesially at base, mesially also with 9
to 11 setae.
Female: Eighth ventrite obtuse posteromedially; gonocoxites (Fig. 129B) each with apicolat-

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Fig. 129. Stenus utan Naomi (Shizuoka: A, G, Mt. Manzaburo; Kanagawa: B–F, Hakone). A, aedeagus; B, 9th
ventrite of male; C, 9th and 10th terga of male; D, spermatheca; E, 7th and 8th ventrites of male; F, endophallic expulsion hooks; G, posterior part of gonocoxite. Scale 1: 0.1 mm for A–D; scale 2: 0.3 mm for E; scale 3:
0.1 mm for F, G.

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293

eral tooth long, almost acute, apicolateral setae very long. Spermatheca (Fig. 129D) with capsule
moderately long, thick; striped duct long, moderately thick to thick; duct very long, thin, tightly
coiled.
Biology and ecology. The beetles of S. utan inhabit leaf litter heaped in the natural forests oflow mountainous to mountainous regions. One male beetle was collected also under the moss at
Mt. Amagi, Shizuoka Pref.
Remarks. S. utan is allied to S. nyorai Naomi, but it is separable from the latter species by theaedeagal median lobe broadest a little before the apicolateral corners (Fig. 129A), the copulatory
tube moderately curved (Fig. 129A), the endophallic expulsion hook much shorter, with its posterior plate broader (Fig. 129F).
Etymology. The speciﬁc epithet of this species is derived from the special clothes of theancient Chinese play, utan.

Concluding Remarks
This is our taxonomic study of Japanese Steninae, in which only the adult morphologicalcharacters and their various conditions are adopted for the sake of the identiﬁcation and taxonomy of species. During the course of our study it was clariﬁed that the Japanese Steninae consists of 2 genera (Dianous and Stenus), 39 species groups (3 species groups in Dianous and 36
species groups in Stenus) and 346 species (6 species in Dianous and 340 species in Stenus)(Naomi et al., 2017 [Part 1], 2019 [Part 2] and present study [Part 3]). At present, the Japanese
species of Steninae (346 species) thus become approximately 7 times the number of species(about 50 species) counted at the beginning of our study in the 1980s.
Only 6 species are known from Japan in the Dianous. As described above, however, a verymuch larger number of species have been discovered, and newly recorded or described, and thenat present known from Japan in the Stenus. Out of the Japanese 340 species of Stenus, 117 species belong to the species groups whose distributional ranges are more or less wide or very wide,and some of the species of such species groups are very widely distributed in the Palaearctic
Region from Europe to Japan (S. ruralis, S. bifoveolatus, S. cicindeloides) or in the Holarctic(S. comma; S. juno, S. melanarius). On the other hand, a very large number of Japanese species(229 species) belong to the species groups whose distributional ranges are mainly East Asia: 61
species (asyura-group), 29 species (indubius-group), 3 species (ﬂammeus-group), 15 species(cirrus-group), 21 species (satsuki-group) and 100 species (cephalotes-group). All the Japanese
species of these species groups are brachypterous and indigenous to the Japanese Archipelago. In
each species group, the species show allopatric distributions there in many cases, and eachspecies is for example distributed in a speciﬁc mountainous area, but 2 or more species are sometimes distributed in the same mountainous area (e.g., S. hirashimai and S. akome in Mt. Hiko,
Kyushu).
Since the Stenus is a very large, megadiverse genus which comprises at present more than
3,000 species world-wide, it is very diﬃcult to do the identiﬁcation of species in the Stenus. Thiswas especially so at the beginning stage on the studies of the Japanese Steninae. Thus, in theearly papers of Japanese Steninae (Naomi, 1987, 1989a, etc.; see also Naomi, 2012, p. 271), theremarks on the allied species have been very often inadequate or beside the point. During thecourse of present study, continuously using the taxonomic results brought by a series of studies
on the Palaearctic, Oriental and Ethiopian species of Stenus mainly by the 3rd author, we studied

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in detail all the Japanese species of Stenus. Therefore, the taxonomic arrangement of species aswell as the remarks on their allied species are much better in the present study than in the previous papers.
Species of Stenus and their classiﬁcation by lumping
As is clear in the summary of our study described above, we treated taxonomically the species of a very large genus Stenus in Japan, and in several major species groups, many brachypterous species are, broadly speaking, allopatrically distributed there. We here pose an essential
question: How can we classify the species in such a very large genus as Stenus?
In our study, the following structures are regarded as taxonomically important characters:
Habitus, ventrites of pregenital abdominal segments (male), genital segments (male and female),aedeagus and endophallic components (male), spermatheca (female), etc. The species are classiﬁed
based on the morphologically diﬀerent conditions of these characters. What we consider to bewell-acceptable or good species in the Stenus is distinct species at base in the arena of taxonomy,
that is, species that is well-recognized on account of a lot of unique conditions of some of thesecharacters, in other words, species that is well-distinguished from its allied species by a lot of theunique conditions of some of taxonomic characters. And then, we hypothesize that such taxonomically acceptable species form independently evolving population-level lineages (species) innature. The reverse is also true. We also think that the species should not in principle be distinguished from their allied species only by the slight diﬀerences of aedeagal and/or endophallic
character conditions, and that the species should not be accepted as taxonomically adequate insuch cases. It does not seem to us that such species do not form independently evolving population-level lineages in nature. It naturally leads to a conclusion that our way of classifying the species of Stenus is not a splitting but a lumping.
In the Stenus-taxonomy, the classiﬁcation of species by lumping is actually practiced mainlyby 2 taxonomic treatments: (1) recognizing (or describing) only the distinct species and (2)synonymizing both the species and subspecies (as small local populations lineages) which arerecognized only by a small amount of morphological diﬀerences of aedeagus and its related
structures. To make taxonomists understand more easily that our approach to species classiﬁcation in the Stenus is a lumping, we here point out 2 taxonomic treatments (synonymizing species
and subspecies) with several concrete examples.
First, taxonomists often encounter the cases where a species in Stenus is morphologicallypoly-formed in that the aedeagus and its endophallic components of the Stenus-beetles collectedfrom one locality are only slightly diﬀerent in structure from those from another locality. In suchcases, we should not consider every small local population (lineage) to be species, and we should
not describe many new species based on many small local populations (recognized by a small
amount of morphological diﬀerences). When the known species have been described as new,based on a slight amount of diﬀerent conditions of aedeagus and/or its endophallic components
observed only in the Stenus-beetles of particular, very narrow local areas, then they should besynonymized each other (e.g., S. santira, Part 2, p. 83). A lumping way of species classiﬁcation is
also concerned with another poly-formed Oriental species, S. pilicornis, which taxonomicallyresulted in making many synonyms (Puthz, 2013). (Note also that the same lumping method is
also practiced in the classiﬁcation of the Dianous; e.g., D. japonicus, Part 1, p. 37.)
The second is on the matter with how we synonymize subspecies (as small local populations in
Kinki District) with their nominotypical subspecies. The examples are as follows: S. olliformis
owasenus ＝ S. olliformis, Part 3, p. 208 and S. ingens ryugatakensis ＝ S. ingens, Part 3, p. 217.

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Since these subspecies can be separated in one way or another from the nominotypical subspecies
only by the slightly diﬀerent conditions of endophallic expulsion hooks, they should be synonymized with their nominotypical subspecies. It seems that each local population (constituting a taxonomically described subspecies) does not form independent subspecies lineages nor species lineages in nature. Such subspecies may be perhaps accepted taxonomically as species in the future,but such taxonomic treatment by splitting should be based on the convincing information including
molecular-phylogenetical and speciational data obtained from a series of detailed studies.
Species groups of Stenus and the size of species groups suitable for the good Stenus-taxonomy
Traditionally the genus Stenus has been classiﬁed into 6 subgenera (Hypostenus, Hemistenus,etc.). The subgenera of Stenus were replaced with species groups in order for adequately classifying the species of Stenus by several taxonomists (Puthz, 2008; Naomi, 2012; Tang et al., 2018,
etc.). The taxonomists have been at present faced with the problem on what the taxonomicallyadequate size of species groups are. In some previous taxonomic studies, the taxonomists haveregarded some various sizes of groups of species as species groups in Stenus. For example, one
treats a more or less large number of species as belonging to one species group (Puthz, 2013,etc.), while other treats a relatively small number of species or only one species as belonging to
one species group (Naomi, 1988a, etc.).
The questions we here pose are as follows: What kinds of species groups are there in thepresent phylogenetic systems of species groups names in the Stenus? And, which species groups
are taxonomically acceptable? In the Stenus, there are certainly many taxonomically good (ormonophyletic) species groups (pilicornis-group, Puthz, 2013, p. 1402; bispinus-group, Puthz,
1985, p. 75; indubius-group, Part 2, p. 130; cirrus-group, Part 2, p. 206; etc.). They are wellcharacterized by stringent autapomorphic character conditions. For example, the cirrus-group is
well-characterized by the occurrence of sparse, suberect setae of abdomen, etc., while thepilicornis-group is by the sileniform paraglossae. Thus, one can promptly identify the Stenusbeetles as those of a species of a particular species group if these beetles belong to the species ofsuch a well-characterized species group.
In addition to these well-established, good species groups, there are also many other species
groups of Stenus which seem to be monophyletic but are only incompletely characterized by the
incomplete (or underlying) apomorphic conditions of characters, or by the particular conditions
which are only tentatively regarded as apomorphic. They are here called tentatively-monophyletic groups of species. This is concerned with the asyura-group (Part 2, p. 5) and cephalotesgroup (Part 3, p. 53). At ﬁrst sight, it seems to us that such groups are not adequate for regarding
as species groups in the formal taxonomic studies. However, these groups seem to be substantially discernable during the actual taxonomic studies of Stenus when the studies are carefully
done for example in such a way as in this paper. Taxonomists may positively understand thatsome such indistinctly discernible species groups should be at least temporarily considered to be
candidates of monophyletic groups for understanding the regional fauna of Stenus.
Furthermore, some other species groups of Stenus seem to be presumably paraphyletic (e.g.,clavicornis-group, Part 1, p. 68). At the present stage, these paraphyletic groups may remain
more or less stable in the classiﬁcation, or they may still now be unchanged taxonomically, inorder to avoid the confusion about the names of species groups in the tasks of species identiﬁcation and then in the various biodiversity studies until the taxonomy of Stenus is completed in the
future.
The genus Stenus is even now neither suﬃciently nor fully studied taxonomically because it296

Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

is extremely diﬃcult to identify the species owing to the very large number of species. Whentaking this into consideration, it may be possible in some cases that more easily noticeable (i.e.,paraphyletic) groups of species are only tentatively introduced into a classiﬁcation of species in
the Stenus because of the reasons mentioned above. However, this is decidedly not good nor
useful for further studies of other ﬁelds including phylogenetics, biogeography, etc., becausesuch species groups do not form solid discussion bases in any way. Thus, out of the abovementioned, 3 qualitatively diﬀerent kinds of species groups, the tentatively-monophyletic as well
as monophyletic groups of species will be acceptable taxonomically.
Then, we here pose the other question: Which size of species groups are adequate for understanding the phylogeny and biodiversity of whole species of Stenus? Generally speaking, whatever the Coleopterous taxa are for the taxonomic studies, it has been and is still the best to do thetaxonomy under the global way, where the species of wider distributional ranges (hopefully, Biogeographical Regions or world-wide) are taken into consideration, with the careful morphological studies of taxonomically important characters. Therefore, it will be here recommended thatfor a better establishment of a series of the species groups in the Stenus, the larger sizes of species groups are hopefully accepted taxonomically. This is just so when considering that small
species groups of narrow local areas which comprise small number of species, even if they are
well-recognized by a series of good apomorphies, will never bring to us an array of rich and thus
heuristic morphological and phylogenetic information, by which to then positively promote further studies of Stenus from a more or less global point of view.
Therefore, in conclusion, the tentatively-monophyletic as well as monophyletic groups ofspecies which probably each comprise for example 50, 100 or more species, will be the good
examples suitable and also adequate for the Stenus-taxonomy, and such species groups will be
truly useful as bases for further various studies of biodiversity.

Acknowledgements
We express our hearty thanks to Dr. Alfred F. Newton (Field Museum, Chicago) for hiskindly informing the holotype depository of S. cephalotes Sharp and also for loaning the holotype of S. testaceopiceus Bernhauer to the ﬁrst author for this study. We sincerely thank Dr.
Toshiya Hirowatari and Dr. Toshiharu Mita (Kyushu University, Fukuoka), Dr. Hiroaki Kojima(Tokyo University of Agriculture, Atsugi), and Dr. Akiko Saito (Natural History Museum andInstitute, Chiba) for loaning the holotype specimens of Stenus-species to the ﬁrst author for thisstudy. We also sincerely thank Dr. Kwang-Sik Oh (Hannam University, Daejeon) for his sending
several papers to the ﬁrst author on the Korean fauna of Steninae. Our sincere thanks are also due
to all the entomologists who kindly gift or loan us the valuable Stenus specimens used for thepresent study.
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Corrigenda and Addenda to the Steninae of Japan Parts 1 and 2
Corrigendum to the Steninae of Japan Part 1
Page 1, line 16. For “(30 species groups and 117 species), read “(30 species groups and 111 species and 1
subspecies)”
Corrigenda to the Steninae of Japan Part 2
Page v, line 4. For “Materials and Methods”, read “Materals of the Steninae treated”
Page 1, line 33. For “Materials and Methods”, read “Materals of the Steninae treated”
Addenda to the Steninae of Japan Part 1
Page 177, line 32. Add the following sentence: “Note that the data of the holotype of S. hiroyukii Puthz was
ﬁst added in Puthz (2001e)”.
Page 178. Add the following data below the line 26: “Type material. Type locality: Far East, Inland in
Sungari River IX.”
Page 327. Add the following paper after the paper of Puthz (2001d): “Puthz, V., 2001e. Note on Stenus
hiroyukii Puthz (Coleoptera, Staphylinidae). Entomological Review of Japan, 56: 73.
Addendum to the Steninae of Japan Part 2
Page iv. Add the following note on the cover illustration below the last line: “Cover Illustration: Stenus
kiyosumiensis Naomi & Takeda.”

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Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

Fig. 130. A, S. pallipes Gravenhorst (East Europe); B, S. kolbei Gerhardt (East Europe); C, S. kajika Naomi &Puthz (Nara: Mt. Odaigahara); D, S. okayamaensis Naomi (Okayama: Niimi); E, S. satsuki Naomi (Ehime:
Mt. Ishizuchi); F, S. intermixtus Puthz (Nagano: Nomugi-tôge); G, S. kannoi Naomi, Nomura & Puthz sp. nov.
(Mie: Inabe); H, S. volkerputhzi Naomi, Nomura & Puthz (Ishikawa: Mt. Hakusan); I, S. uneme Naomi(Tokushima: Mt. Takashiro); J, S. taoi Naomi (Yamanashi: Yanagisawa Pass); K, S. fujimontis Puthz (Shizuoka: Mt. Fuji); L, S. fujiensis Puthz (Shizuoka: Mt. Fuji). Scale: 0.5 mm.

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Fig. 131. A, S. friebi Benick (Far East: Khabarovsk Territory: Odyr cordon); B, S. etsukoae Naomi (Hokkaido:
Nissho Pass); C, S. kazami Naomi (Akita: Shirakami Mts.); D, S. silvaticulus Naomi (Fukushima: Iitate-mura); E, S. koinobori Hromádka (Hokkaido: Mt. Kariba); F, S. puthziellus Naomi (Iwate: Mt. Hayachine);
G, S. hagoromo Naomi (Okinawa : Ishigaki Is.) ; H, S. perspicabilis Puthz (Taiwan: Kaohshun); I, S. sugayai
Puthz (Taiwan: Mt. Amma-shan); J, S. cephalotes Sharp (Nagasaki: Hirado Is.); K, S. oblongulus Naomi(Miyazaki: Tano-cho); L, S. inexoratus Puthz (Hiroshima: Toyosaka-machi)．
Scale: 0.5 mm.

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Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

Fig. 132. A, S. coﬀeatus Naomi (Kochi: Ashizuri); B, S. ryugu Naomi (Nagasaki: Tsushima Is.); C, S. kaguyahime
Naomi (Saga: Mt. Seburi); D, S. dainichi Puthz (Wakayama: Mt. Nachi); E, S. subtruncatus Naomi, Nomura& Puthz sp. nov. (Mie: Kiwa-cho); F, S. kyotoensis Naomi, Nomura & Puthz sp. nov. (Kyoto: Mt. Ooe); G,
S. cinanomontis Naomi & Nomura (Nagano: Hyogoe Pass); H, S. incalcaratus Naomi (Shizuoke: Amagi
Pass); I, S. inamatus Puthz (Niigata: Yagizawa); J, S. keman Naomi (Gifu: Nishihotakaguchi); K, S. warabi
Naomi & Nomura (Hyogo: Ushiroyama); L, S. himiko Naomi (Nara: Ohdaigahara). Scale: 0.5 mm.

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Fig. 133. A, S. aoi Naomi & Puthz (Fukui: Mt. Ohtake); B, S. intrarius Naomi & Ito (Shiga: Oisugi Forest); C, S.
inaspectus Puthz (Ehime: Omogokei); D, S. imasakai Naomi (Nagasaki: Ohseto-cho); E, S. cosiciensis Naomi& Hayashi (Kagoshima: Shimokoshiki Is.); F, S. daimio Naomi (Nagasaki: Nagasaki City); G, S. yoshidai
Naomi (Tokushima, Shishikui-cho); H, S. hirashimai Naomi (Fukuoka: Mt. Hiko); I, S. gion Naomi & Ito(Kyoto: Ashiu); J. S. inclarescens Puthz (Ishikawa: Hakui); K, S. coiﬀaitiellus Naomi & Puthz (Mie: Ise); L,
S. productus Naomi (Mie: Ise). Scale: 0.5 mm.

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Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

Fig. 134. A, S. kagura Naomi & Puthz (Okayama: Mt. Kuma); B, S. toshiharui Naomi (Nagasaki: Oonohara); C,
S. akome Naomi (Miyazaki: Mt. Morotsuka); D, S. amida Naomi (Tokushima: Mt. Tsurugi); E, S. rufescens
Sharp (Hyogo: Mt. Mayasan); F, S. jukata Hromádka (Wakayama: Mt. Kôyasan); G, S. deltoides Naomi,
Nomura & Kamezawa (Fukui: Karikomi Pond); H, S. olliformis Naomi (Nara: Oomine Mts.); I, S. ebisu
Naomi (Nara: Ohdaigahara); J. S. daigonis Naomi & Puthz (Kyoto: Uji City); K, S. mikawanis Naomi (Gifu:
Ena-jinja); L, S. nakanei Hromádka (Kôchi: Niyodo-mura). Scale: 0.5 mm.

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305

Fig. 135. A, S. testaceopiceus Bernhauer (Osaka: Nose); B, S. okiensis Naomi & Shimada (Shimane: Oki Isls.);
C, S. akojagai Hromádka (Tottori: Misasa Spa); D, S. gagyumontis Naomi (Okayama: Mt. Gagyusan); E,
S. okamotoi Naomi (Hiroshima: Toyosaka-machi); F, S. amma Naomi & Nomura (Nara: Dorogawa); G,
S. expansus Naomi & Ito (Gifu: Araidashi Forest); H, S. bosatsu Naomi (Yamanashi: Kaminikkawa Pass); I,
S. usitatus Naomi & Nomura (Shizuoka: Mt. Fuji); J, S. bifurcatus Naomi (Mie: Hokusei); K, S. syaca Naomi(Ishikawa: Senami); L, S. asiuensis Naomi, Nomura & Puthz sp. nov. (Shizuoka: Izu City). Scale: 0.5 mm.

306

Index
In this index, for each of the Dianous and Stenus, the speciﬁc and subspeciﬁc epithets (in the valid
names of species or subspecies described, redescribed or taxonomically treated in various ways in the Parts
1, 2 and 3), together with the names of authors, and also the names of the groups, subgroup and complex of
species are arranged alphabetically. The synonymic names of species and subspecies are also added andprinted in italics. Part 1 means the paper of Naomi et al. (2017), Part 2 means the paper of Naomi et al.
(2019), and Part 3 means the present paper.
Dianous, Part 1, 25
amamiensis Sawada, Part 1, 33
calceatus-group, Part 1, 27
chinensis-group, Part 1, 30
coerulescens-group, Part 1, 32
gongen Y. Watanabe, Part 1, 37
iwakisanus Y. Watanabe, Part 1, 35
japonicus Sawada, Part 1, 37
morimotoi Naomi, Part 1, 37
moritai Naomi, Part 1, 27
septentrionalis Naomi, Part 1, 37
shibatai Sawada, Part 1, 40
uedai Naomi, Part 1, 27
viridicatus Naomi, Part 1, 37
yoshidai Naomi, Part 1, 30
Stenus, Part 1, 42
abbreviatus Naomi, Part 1, 193
abdominalis-group, Part 1, 293
aboblitus Naomi & Nomura, Part 1, 185
acerrimus Naomi, Part 2, 163
acutatus Naomi, Part 3, 193
aestivus Naomi, Part 1, 217
agrestis Naomi, Part 3, 207
akikoae Naomi, Part 3, 79
akojagai Hromádka, Part 3, 245
akome Naomi, Part 3, 180
alesi Naomi, Part 2, 102alienus Sharp, Part 1, 54
alpicola-group, Part 1, 285
alter Puthz, Part 3, 61
amagasui Naomi, Part 3, 86
amamiensis Naomi, Part 2, 204
ambiguellus Naomi, Part 3, 280
amida Naomi, Part 3, 184amma Naomi & Nomura, Part 3, 257
amurensis Eppelsheim, Part 1, 87

ancyleus Naomi, Nomura & Puthz, Part 1, 227
anfractus Naomi, Part 2, 63
angusticulus Naomi, Nomura & Puthz, Part 2, 219
anthracinus Sharp, Part 1, 57
aoi Naomi & Puthz, Part 3, 123
aquilonalis Naomi & Puthz, Part 1, 251
araiorum Naomi, Part 2, 77
asiuensis Naomi, Nomura & Puthz sp. nov., Part 3, 281
asyura hakonensis Naomi, Part 2, 96
asyura-group, Part 2, 5
asyura-subgroup, Part 2, 53
asyura Naomi, Part 2, 94
autumnalis Naomi, Part 2, 134
awajinis Naomi spec. valid., Part 3, 230
basara Naomi, Part 2, 90
benefactor Ryvkin, Part 1, 229
beppuensis Bernhauer, Part 1, 89
bicara Naomi, Part 2, 74
bicolon Sharp, Part 1, 294
bifoveolatus Gyllenhal, Part 1, 220bifurcatus Naomi, Part 3, 275
biguttatus (Linnaeus), Part 1, 51
bishamon Naomi, Part 2, 20
bispinus-group, Part 1, 283
biwa Hromádka, Part 2, 72
bohemicus Machulka, Part 1, 249
boops Ljungh, Part 1, 173
bosatsu Naomi, Part 3, 268
brendelli Naomi, Part 2, 55
brevispinis Naomi, Part 3, 97
bunraku Hromádka, Part 2, 116
caesariatus Naomi & Ito, Part 2, 231calliceps Bernhauer, Part 1, 94
campaniformis Naomi, Nomura & Puthz, Part 2, 157
canariculatus-group, Part 1, 177
carura Naomi, Part 2, 22
cephalotes Sharp, Part 3, 64

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307

ferus Naomi, Part 3, 199
cephalotes-group. Part 3, 53
ﬁnalis Ryvkin, Part 1, 210
cephalotes-subgroup. Part 3, 59
ﬂammeus-group, Part 2, 198
cicindela Sharp, Part 2, 261
ﬂavidulus Sharp, Part 1, 280
cicindeloides (Schaller), Part 1, 261
ﬂavidulus paederinus Champion, Part 1, 282
cinanomontis Naomi & Nomura, Part 3, 95
ﬂavipes-group, Part 1, 224
circularis-group, Part 1, 165
formosanus L. Benick, Part 1, 96
cirriformis Naomi, Part 2, 217
friebi-complex, Part 3, 39
cirrus-group, Part 2, 209
fugu Hromádka, Part 2, 169
crassus-group, Part 1, 200
fujiensis Puthz, Part 3, 35
clavicornis-group, Part 1, 68
fujimontis Puthz, Part 3, 33
clavicornis (Scopoli), Part 1, 98
fukuimontium Puthz, Part 3, 283
clio Naomi, Part 2, 59
fulvidus Naomi, Nomura & Puthz sp. nov., Part 3, 159
coelogaster-group, Part 1, 275
fulvivestis Naomi & Y. Watanabe, Part 2, 90
coﬀeatus Naomi, Part 3, 72
cohaerens Naomi, Nomura & Puthz sp. nov., Part 3, 114 fusciceps Naomi, Part 2, 191
gagyumontis Naomi, Part 3, 253
coiﬀaitiellus Naomi & Puthz, Part 3, 165
gatenpio Naomi, Part 1, 77
comma-group, Part 1, 45
geisha Puthz, Part 2, 26
comma LeConte, Part 1, 46
gestroi Fauvel, Part 1, 314
concinnus Sharp, Part 1, 232
gestroi-group, Part 1, 313
confertus Sharp, Part 1, 244
gibbicollis-group, Part 1, 187
coronatus zipanguensis Puthz, Part 1, 297
gion Naomi & Ito, Part 3, 155
corrugatus Naomi & Shimada, Part 1, 138
giushin Naomi, Part 1, 119
cosiciensis Naomi & Hayashi, Part 3, 137
gloriﬁcus Naomi, Nomura & Puthz sp. nov., Part 3, 129
cucumeroides Naomi & Puthz, Part 2, 165
gracilior Naomi, Part 3, 37
currax Sharp, Part 1, 283
guttalis Fauvel, Part 1, 317
curvaticellus Naomi, Part 1, 142
guttalis-group, Part 1, 316
cygnipenis Puthz, Part 3, 205
guttalis ishigakiensis Naomi, Part 1, 317
cylindricollis-group, Part 1, 266
gyrosus Naomi, Part 3, 227
daigonis Naomi & Puthz, Part 3, 215
hagai Naomi, Part 1, 140
daikoku Naomi, Part 2, 104
haginoi Naomi, Part 2, 118
daimio Naomi, Part 3, 141
hagoromo Naomi, Part 3, 50
dainichi Puthz, Part 3, 84
hakonensis Naomi, Part 2, 96
davidhulli Naomi, Part 2, 15
hammondi Puthz, Part 1, 113deltoides Naomi, Nomura & Kamezawa, Part 3, 201
hanami Hromádka, Part 1, 269
depressus Puthz, Part 1, 225
haniwa Hromádka, Part 3, 107
displicatus Naomi, Nomura & Puthz, Part 1, 146
hannia Naomi, Part 2, 110dissimilis Sharp, Part 1, 246
hayashii Puthz, Part 2, 11
distans Sharp, Part 1, 89
hijiri Naomi, Part 2, 65
disterminus Puthz, Part 1, 92
hime Naomi & Puthz, Part 3, 19
domburi Hromádka, Part 2, 223
himiko Naomi, Part 3, 118
dubitativus Puthz, Part 2, 127
hirashimai Naomi, Part 3, 149
ebisu Naomi, Part 3, 211hiroyukii Puthz, Part 1, 175
ellipsoides Naomi, Part 2, 86
hirtellus Sharp, Part 1, 237
enma Naomi, Part 3, 261
hirtiventris Sharp, Part 1, 205
etsukoae Naomi, Part 3, 40
hoshinai Naomi, Part 3, 109
expansus Naomi & Ito, Part 3, 265
hotei Naomi, Part 3, 12
expugnator Ryvkin, Part 1, 115

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Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

houomontis Naomi & Ito, Part 1, 161
houou Naomi, Part 2, 44
humilis-group, Part 1, 105
hypovelox Naomi & Puthz, Part 2, 178
ichihashii Naomi, Part 3, 221
ichihashii miunensis Naomi syn. nov., Part 3, 221ichikawai Naomi, Part 3, 195
ignolabilis Naomi, Part 3, 228
ignorabilis awajinis Naomi, Part 3, 230
imadatei Naomi & Puthz syn. nov., Part 3, 42
imasakai Naomi, Part 3, 135
immarginatus Mäklin, Part 1, 201
inaequatus Puthz, Part 2, 42
inaestimatus Puthz, Part 3, 103
inamatus Puthz, Part 3, 101
inaspectus Puthz, Part 3, 133
inassuetus Puthz, Part 3, 139
inbecillus Naomi, Part 2, 17
incalcaratus Naomi, Part 3, 99
incanus-group, Part 1, 183
inclarescens Puthz, Part 3, 157
incommodus Puthz, Part 2, 13
incumbens Naomi & Y. Watanabe, Part 3, 182
incurvatus Naomi & Nomura, Part 3, 255
indagator Eppelsheim, Part 1, 72
indubius-group, Part 2, 130
indubius Sharp, Part 2, 193
indubius-subgroup, Part 2, 142
inexoratus Puthz, Part 3, 68
ingens Naomi, Part 3, 217
ingens ryugatakensis Naomi syn. nov., Part 3, 217
inimitabilis-subgroup, Part 2, 133
inimitabilis Puthz, Part 2, 138
intermixtus Puthz, Part 3, 21
intrarius Naomi & Ito, Part 3, 125
intumescens Naomi, Nomura & Puthz, Part 1, 144
ivanloebli Naomi, Nomura & Puthz sp. nov. Part 3, 88
izanagi Naomi & Puthz, Part 2, 50
jambar Naomi, Part 2, 200
jamesashei Naomi, Part 3, 93
japonicus Sharp, Part 1, 108
javanus-group, Part 1, 167
jukata Hromádka, Part 3, 197
juno Paykull, Part 1, 70
jurojin Naomi, Part 2, 79
kagura Naomi & Puthz, Part 3, 176
kaguyahime Naomi, Part 3, 79

kajika Naomi & Puthz, Part 3, 12
kamezawai Naomi, Nomura & Puthz, Part 1, 301
kanmiyai Naomi, Part 1, 229
kannoi Naomi, Nomura & Puthz sp. nov., Part 3, 23
kanzeon Naomi, Part 2, 234
kasumi-subgroup, Part 2, 9
kasumi Naomi, Part 2, 33
katoi Naomi & Ito, Part 1, 80
kazami Naomi, Part 3, 42
keman Naomi, Part 3, 107
kiesenwetteri Rosenhauer, Part 1, 264
kirin Naomi & Ito, Part 1, 123
kishimotoi Naomi & Puthz, Part 2, 183
kisomontanus Naomi, Nomura & Puthz, Part 2, 28
kiyosumiensis Naomi & Takeda, Part 2, 196
kobensis Cameron, Part 1, 62
kochiensis Naomi, Nomura & Puthz sp. nov., Part 3, 135
koinobori Hromádka, Part 3, 46
kokie Naomi, Part 1, 152
komonoensis Naomi, Part 2, 61
kumoma Naomi, Part 2, 48
kyotoensis Naomi, Nomura & Puthz sp. nov., Part 3, 91
kyushuensis Naomi & Puthz, Part 2, 174
laborator Sharp, Part 1, 103
lanceolatus Naomi, Part 1, 127
latitarsis Sharp, Part 1, 222
leehermani Naomi, Part 3, 289
lentus Sharp, Part 1, 72
lewisius Sharp, Part 1, 77
longisetosus Puthz, Part 2, 223
lubomiri Naomi, Part 3, 219
macies Sharp, Part 1, 65
maiko Naomi & Puthz, Part 3, 169
mammops Casey, Part 1, 110
maruyamai Naomi, Part 2, 67
masaakii Naomi & Nomura, Part 3, 267
masatakai Naomi & Nomura, Part 3, 251
matobai Naomi, Part 3, 174
melanarius-group, Part 1, 172
melanarius Stephens, Part 1, 175
melanarius verecundus Sharp, Part 1, 175
mercator Sharp, Part 1, 254
mikado Hromádka, Part 1, 193
mikawanis Naomi, Part 3, 225
miroku Naomi, Part 3, 249
miyama Naomi, Part 1, 198
mysticus Sharp, Part 1, 303

The Steninae of Japan Part 3309

plagiocephalus L. Benick, Part 1, 271
mystiformis Naomi, Nomura & Puthz, Part 1, 307
praeclarus Naomi, Part 2, 108
nachiensis Puthz, Part 2, 212
productus Naomi, Part 3, 167
nagasakianus Bernhauer, Part 3, 64
protrudens Naomi & Y. Watanabe, Part 2, 125
nakanei Hromádka, Part 3, 228
protuberans Naomi & Y. Watanabe, Part 2, 88
nakanei awajinis (Naomi), Part 3, 230
puberulus Sharp, Part 1, 183
nakanei mikawanis Naomi, Part 3, 225
pubescens fraternus Casey, Part 1, 215
namazu Hromádka, Part 1, 292
pubescens-group, Part 1, 214
naomii Puthz, Part 2, 159
pubicornis Naomi, Part 3, 237
naturalis Naomi & Y. Watanabe, Part 2, 112
pudefactus Ryvkin, Part 1, 195
nemoralis Naomi syn. nov., Part 3, 29
pulcher-group, Part 1, 279
nemorosus Naomi & Y. Watanabe, Part 3, 31
punctifer Naomi, Part 2, 200
nipponensis Cameron, Part 1, 108
puthziellus Naomi, Part 3, 48
nipponomontanus Naomi, Part 1, 134
puthzorum Naomi & Y. Watanabe, Part 1, 60
nishikawai Naomi, Part 1, 84
nogohakusanus Naomi, Nomura & Kamezawa, Part 2, 98 raddei Ryvkin, Part 1, 178
rasilis Naomi & Ito, Part 2, 227
nomurai Naomi, Part 1, 188
notomontis Naomi, Nomura & Puthz sp. nov., Part 3, 160 recurvatus Naomi, Part 1, 299
regularis Naomi & Y. Watanabe, Part 3, 111
nyoirin Naomi, Part 2, 240
riukiuensis Puthz, Part 1, 167
nyorai Naomi, Part 2, 26
rorellus-group, Part 1, 243
oblitus Sharp, Part 1, 239
rufescens Sharp, Part 3, 190
oblongulus Naomi, Part 3, 66
rufescens-subgroup, Part 3, 145
obtusus Naomi, Nomura & Puthz sp. nov., Part 3, 161
rugipennis Sharp, Part 1, 290
ochiba Naomi & Puthz, Part 1, 129
ruralis Erichson, Part 1, 170
ohbayashii Naomi, Part 1, 125
ruricolaris Naomi, Part 2, 57
ohishii Naomi, Part 2, 189
ryugu Naomi, Part 3, 74
ohtoensis Naomi, Part 3, 203sadoensis Naomi, Part 2, 147
oisami Naomi & Puthz, Part 2, 70
sakaii Naomi & Puthz, Part 2, 225
okamotoi Naomi, Part 3, 257
sakana Hromádka, Part 2, 171
okayamaensis Naomi, Part 3, 15
sakura Hromádka, Part 1, 117
okiensis Naomi & Shimada, Part 3, 241
santira Naomi, Part 2, 83
oliverbetzi Naomi, Nomura & Puthz, Part 1, 234
sasajii Naomi, Part 1, 183olliformis Naomi, Part 3, 208
sasajiiellus Naomi, Nomura & Puthz sp. nov., Part 3, 285
olliformis owasenus Naomi syn. nov., Part 3, 208
satsuki Naomi, Part 3, 17
omogoensis Naomi & Y. Watanabe, Part 1, 308
satsuki-group, Part 3, 7
oni Naomi, Part 2, 120
satushin Naomi, Part 1, 132
oni-subgroup, Part 2, 106
sauteri Bernhauer, Part 1, 82
ookami Hromádka, Part 2, 167
sawadai Hromádka, Part 2, 180
opticus-group, Part 1, 212
sawadaianus Hromádka, Part 2, 236
oshimaensis Naomi, Part 1, 275
sawadaiellus Naomi & Puthz, Part 2, 38
otohime Naomi, Part 3, 82
scissilis Naomi, Nomura & Puthz, Part 2, 30
pallitarsis-group, Part 1, 217
sedatus Sharp, Part 1, 256
palpalis Sharp, Part 1, 310
seminiger-group, Part 1, 65
palposus-group, Part 1, 170
serratimarginatus Naomi, Part 1, 154
pediculifer Naomi & Nomura, Part 3, 187
serratus Naomi, Part 2, 145
piliferus-group, Part 1, 231
sexualis Sharp, Part 1, 165
piliferus Motschulsky, Part 1, 241
sharpi Bernhauer & Schubert, Part 1, 310
pilosiventris Bernhauer, Part 1, 207

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sharpi-group, Part 1, 310
ukon Naomi & Puthz, Part 2, 172
Sharpianus Cameron, Part 1, 292
unagi Hromádka, Part 2, 167
shogun Puthz, Part 1, 180
uncinatus Naomi, Nomura & Puthz, Part 2, 40
shojiroi Naomi, Part 3, 127
uneme Naomi, Part 3, 27
shuheii Naomi, Part 3, 279
unicoloratus Naomi & Puthz, Part 2, 153
sibiricus J. Sahlberg, Part 1, 288
unicuspidatus Naomi & Nomura, Part 2, 31
sicyoideus Naomi, Nomura & Puthz sp. nov., Part 3, 105 unzenmontis Naomi & Puthz, Part 2, 136
silvaticulus Naomi, Part 3, 44
usitatus Naomi & Nomura, Part 3, 271
similis-group, Part 1, 248
utan Naomi, Part 3, 291
siphonifer Naomi, Part 2, 140
varicosus Naomi, Nomura & Puthz, Part 1, 191
snodgrassi Naomi, Part 3, 163
virgula-group, Part 1, 290
spurius L. Benick, Part 1, 277
velox Sharp, Part 1, 267
strobilus Ryvkin, Part 1, 212
verecundus Sharp, Part 1, 175
subserratus Naomi, Part 2, 149vernalis Naomi, Part 2, 193
subulifer Naomi, Nomura & Puthz sp. nov., Part 3, 121 vernicosus Naomi & Nomura, Part 2, 238sugiei Naomi, Part 2, 229
veselovae Ryvkin, Part 1, 286
syaca Naomi, Part 3, 277
volkeri Naomi, Part 3, 239
syugen Naomi syn. nov., Part 3, 118
volkerputhzi Naomi, Nomura & Puthz, Part 3, 25
takane Naomi, Part 2, 151
wakayamanus Puthz, Part 2, 176
takara Nakane, Part 1, 314
warabi Naomi & Nomura, Part 3, 116
takashii Naomi, Part 1, 163
wasabi Hromádka, Part 3, 213
takashiiellus Naomi, Nomura & Puthz sp. nov., Part 3, 143 wasamatanus Puthz, Part 1, 136
takedai Naomi, Part 1, 101
wasmanni-group, Part 1, 277
tanuki Hromádka, Part 2, 176
weisei Bernhauer, Part 1, 258
taoi Naomi, Part 3, 29
yamabusi Naomi & Ito, Part 2, 210
tateoi Naomi, Part 2, 187
yamajii Naomi & Puthz, Part 3, 153
tateoitoi Naomi, Nomura & Puthz sp. nov., Part 3, 273 yamato Naomi, Part 1, 75
tengu Hromádka, Part 2, 83
yanoi Sawada & Nakane, Part 1, 57
tenuipes Sharp, Part 1, 48
yashiro Naomi & Puthz, Part 2, 221
testaceopiceus Bernhauer, Part 3, 235
yasuhikoiellus Naomi, Part 2, 46
tohokuensis Naomi & Puthz, Part 2, 155
yasutoshii Naomi, Part 1, 159
tokunis Naomi, Part 2, 202
yatsugatakensis Naomi, Part 2, 36
tomitaorum Naomi, Part 1, 203
yokozekii Naomi, Part 2, 185
toshiharui Naomi, Part 3, 178
yoshidai Naomi, Part 3, 147
toukin Naomi & Puthz, Part 1, 148
yoshidaiellus Naomi, Nomura & Puthz sp. nov., Part 3, 190
triprotrudens Naomi & Y. Watanabe, Part 2, 123
yoshitomii Naomi, Part 3, 70
trispinosus Naomi & Nomura, Part 2, 24
yukawai Naomi, Part 2, 100
tsukubamontis Naomi, Nomura & Kamezawa, Part 2, 81 zaishin Naomi, Part 1, 121
tsurusakii Naomi, Part 3, 243zaishin ohbayashii Naomi, Part 1, 125
tsushimamontis Naomi, Nomura & Puthz sp. nov., Part 3, 76 zdenae Hromádka, Part 2, 114
tuberascens Naomi, Nomura & Puthz, Part 2, 161
zipanguensis Puthz, Part 1, 297
tumifactus Naomi, Part 3, 287
zipanguensis watanabei Puthz, Part 1, 297
ubusuna Naomi & Ito, Part 1, 150
zimmermanni Puthz, Part 1, 156
uedai Naomi, Part 2, 215
zimmermanni curvaticulus Naomi, Part 1, 142
uenoi Naomi & Nomura, Part 3, 262

National Museum of Nature and Science Monographs(Nos. 1–35 were published as “National Science Museum Monographs)
No. 1*.
No. 2*.
No. 3*.
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No. 5.
No. 6.
No. 7.
No. 8.
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No. 28.

Early Cretaceous marine and brackish-water Gastropoda from Japan. By Tomoki Kase, 199 pp., 31 pls.,
1984.
A taxonomic study on the subfamily Herminiinae of Japan (Lepidoptera, Noctuidae). By Mamoru
Owada, 208 pp., 1987.
Small mammal fossils and correlation of continental deposits, Safford and Duncan Basins, Arizona,
USA. By Yukimitsu Tomida, 141 pp., 1987.
Late Miocene floras in northeast Honshu, Japan. By Kazuhiko Uemura, 174 pp., 11 pls., 1988.
A revisional study of the spider family Thomisidae (Arachnida, Araneae) of Japan. By Hirotsugu Ono,
252 pp., 1988.
The taxonomic study of Japanese dictyostelid cellular slime molds. By Hiromitsu Hagiwara, 131 pp.,
1989.
A systematic study of the Japanese Chiroptera. By Mizuko Yoshiyuki, 242 pp., 1989.
Rodent and lagomorph families of Asian origins and diversification: Proceedings of Workshop WC-2
29th International Geological Congress, Kyoto, Japan. Edited by Yukimitsu Tomida, Chuankuei Li, andTakeshi Setoguchi, 195 pp., 1994.
A microevolutional history of the Japanese people as viewed from dental morphology. By Hirofumi
Matsumura, 130 pp., 1995.
Studies on the human skeletal remains from Jiangnan, China. Edited by Bin Yamaguchi and Huan
Xianghon, 108 pp., 3 pls., 1995.
Annoted checklist of the inshore fishes of the Ogasawara Islands. By John E. Randall, Hitoshi Ida,
Kenji Kato, Richard L. Pyle, and John L. Earle, 74 pp., 19 pls., 1997.
Deep-sea fauna and pollutants in Suruga Bay. By Tsunemi Kubodera and Masaaki Machida, et al., 336
pp., 12 pls., 1997.
Polychaetous annelids from Sagami Bay and Sagami Sea collected by the Emperor Showa of Japan anddeposited at the Showa Memorial Institute, National Science Museum, Tokyo. Families Polynoidae andAcoetidae. By Minoru Imajima, 131 pp., 1997.
Advance in vertebrate paleontology and geochronology. Edited by Yukimitsu Tomida, Lawrence J.
Flynn, and Louis L. Jacobs, 292 pp., 1998.
Proceedings of the Second Gondwanan Dinosaur Symposium. Edited by Yukimitsu Tomida, Thomas H.
Rich, and Patricia Vickers-Rich, 296 pp., 1999.
Onuphidae (Annelida, Polychaeta) from Japan, excluding the genus Onuphis. By Minoru Imajima, 115
pp., 1999.
Description of a new species of Anhangueridae (Pterodactyloidea) with comments on the pterosaur
fauna from the Santana Formation (Aptian-Albian), northeastern Brazil. By Alexander W. A. Kellner
and Yukimitsu Tomida, 135 pp., 2000.
Proceedings of the First and Second Symposia on Collection Building and Natural History Studies in
Asia. Edited by Keiichi Matsuura, 188 pp., 2000
A taxonomic revision of the marine species of Cladophora (Chlorophyta) along the coasts of Japan andthe Russian Far-east. By Christiaan van den Hoek and Mitsuo Chihara, 242 pp., 2000.
Deep-sea fauna and pollutants in Tosa Bay. Edited by Toshihiko Fujita, Hiroshi Saito and Masatsune
Takeda, 380 pp., 2001.
Marine Fauna of the Shallow Waters around Hainan Island, South China Sea. Edited by Keiichi Matsuura, 126 pp., 2001.
Proceedings of the Third and Fourth Symposia on Collection Buildings and Natural History Studies in
Asia and the Pacific Rim. Edited by Tsunemi Kubodera, Masanobu Higuchi, and Ritsuro Miyawaki,
193 pp., 2002.
Polychaetous Annelids from Sagami Bay and Sagami Sea Collected by the Emperor Showa of Japanand Deposited at the Showa Memorial Institute, National Science Museum, Tokyo (II). Orders included
within the Phyllodocida, Amphinomida, Spintherida and Eunicida. By Minoru Imajima, 221 pp., 2003.
Proceedings of the Fifth and Sixth Symposia on Collection Building and Natural History Studies in
Asia and the Pacific Rim. Edited by Shinobu Akiyama, Ritsuro Miyawaki, Tsunemi Kubodera, andMasanobu Higuchi 292 pp., 2004.
Revision of scydmaenid beetles of the genus Syndicus Motschulsky (Coleoptera, Scydmaenidae). By
Pawel Jaloszynski, 108 pp., 2004.
A new specimen of Apatosaurus ajax (Sauropoda: Diplodocidae) from the Morrison Formation (Upper
Jurassic) of Wyoming, USA. By Paul Upchurch, Yukimitsu Tomida, and Paul M. Barrett, 108 pp., 10
pls., 2004.
Leaf-rolling Sawflies of the Pamphilius vafer complex (Hymenoptera, Pamphiliidae). By Akihiko Shinohara, 116 pp., 2005.
Types of Japanese Bird. By Hiroyuki Morioka, Edward C. Dickinson, Takashi Hiraoka, Desmond Allen
and Takeshi Yamasaki, 154 pp., 2005.

No. 29.
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No. 48
No. 49No. 50No. 51
No. 52Deep-sea fauna and pollutants in Nansei Islands. Edited by Kazunori Hasegawa, Gento Shinohara andMasatsune Takeda, 476 pp., 2005.
Phenology and Growth Habits of Tropical Trees: Long-term Observations in the Bogor and Cibodas
Botanic Garden, Indonesia. Edited by Hiroaki Hatta and Dedy Darnaedi, 436 pp., 2005.
The Cretaceous System in the Makarov area, southern Sakhalin, Russian Far East. Edited by Yasunari
Shigeta and Haruyoshi Maeda, 136 pp., 2005.
Revision of the Palearctic species of the myrmecophilous genus Pella (Coleoptera, Staphylinidae, Ale­ocharinae). By Munetoshi Maruyama, 207 pp., 2006.
Checklist of Japanese lichens and allied fungi. By Syo Kurokawa and Hiroyuki Kashiwadani, 157 pp.,
2006.
Proceedings of the Seventh and Eighth Symposia on Collection Building and Natural History Studies in
Asia and the Pacific Rim. Edited by Yukimitsu Tomida, Tsunemi Kubodera, Shinobu Akiyama andTaiju Kitayama, 294 pp., 2006.
Anatomy of a Japanese Tomistomine Crocodylian, Toyotamaphimeia Machikanensis (Kamei et Ma­
tsumoto, 1965), from the Middle Pleistocene of Osaka Prefecture: The Reassessment of its Phylogenetic Status within Crocodylia. By Yoshitsugu Kobayashi, Yukimitsu Tomida, Tadao Kamei and Taro
Eguchi, 121 pp., 2006.
A systematic study of the genus Siriella (Crustacea: Mysida) from the Pacific and Indian oceans, withdescriptions of fifteen new species. Edited by Masaaki Murano and Kouki Fukuoka, 173 pp., 2008.
Chromosome atlas of flowering plants in Japan. Edited by Tsunehiko Nishikawa, 706 pp., 2008.
The Lower Triassic System in the Abrek Bay area, South Primorye, Russia. Edited by Yasunari Shigeta,
Yuri D. Zakharov, Haruyoshi Maeda and Alexander M. Popov, 218 pp., 2009.
Deep-sea Fauna and Pollutants off Pacific Coast of Northern Japan. Edited by Toshihiko Fujita, 755 pp.,
2009.
Joint Haeckel and Ehrenberg Project: Reexamination of the Haeckel and Ehrenberg Mircofossil Collections as a Historical and Scientific Legacy. Edited by Yoshihiro Tanimura and Yoshiaki Aita, 106 pp.,2009.
Middle and Late Miocene Marie Bivalvua from the Northeern Kanto Region, Central Japan. Edited by
Yukito Kurihara, 87 pp., 2010.
Chemical Compositions of Electrum Grains in Ore and Placer Deposits in the Japanese Islands. By Kazumi
Yokoyama, Shogo Takeuchi, Izumi Nakai, Yukiyasu Tsutsumi, Takashi Sano, Masako Shigeoka, Ritsuro
Miyawaki and Satoshi Matsubara, 80 pp., 2011.
Digeneans (Trematoda) Parasitic in Freshwater Fishes (Osteichthyes) of the Lake Biwa Basin in Shiga
Prefecture, Centeral Honshu, Japan. By Takeshi Shimazu, Misako Urabe and Mark J. Grygier, 105 pp.,2011.
Deep-sea Fauna of the sea of Japan. Edited by Toshihiko Fujita, 291 pp., 2014.
Olenekian (Early Triassic) Stratigraphy and Fossil Assemblages in Northeastern Vietnam. Edited by
Yasunari Shigeta, Toshifumi Komatsu, Takumi Maekawa and Huyen Dang Tran, 309 pp., 2014.
The Subfamily Steninae Macleay, 1825 (Coleoptera: Staphylinidae) of Japan Part 1. Dianous and Stenus (S. comma Group to S. guttalis Group). By Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz,
339 pp., 2017.
Bio-Anthropological Studies of Early Holocene Hunter-Gatherer Sites at Huiyaotian and Liyupo in
Guangxi, China. By Hirofumi Matsumura, Hsiao-chun Hung, Li Zhen and Kenichi Shinoda, 228 pp.,2017.
Flavonoids of the Plants Composing Flora of Japan. By Tsukasa Iwashina, 649 pp., 2018.
Checklist of Lichens and Allied Fungi of Japan. By Yoshihito Ohmura and Hiroyuki Kashiwadani, 143pp., 2018.
Campanian (Late Cretaceous) ammonoids and inoceramids from the Ribira River area, Hokkaido,
northern Japan. By Yasunari Shigeta, Masataka Izukura and Tomohiro Nishimura, 139 pp., 2019.
The Subfamily Steninae Macleay, 1825 (Coleoptera: Staphylinidae) of Japan Part 2. Stenus AsyuraGroup to S. Cirrus-Group. By Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz, 259 pp., 2019.
Checklist of planktonic diatoms in the coastal waters of western Japan. By Keisuke Tezaki, Megumi
Saito-Kato and Kazumi Matsuoka, 151 pp., 2021.
All inquiries concerning the Monographs should be addressed to:
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