National Museum of Nature and Science Monographs No. 51
ISSN 1881-9109

THE SUBFAMILY STENINAE MACLEAY, 1825
(COLEOPTERA: STAPHYLINIDAE) OF JAPANPART 2. STENUS ASYURA-GROUP TO
S. CIRRUS-GROUP

Shun-Ichiro NaomiShûhei Nomura
Volker Puthz

National Museum of Nature and Science Tokyo,
August 2019

National Museum of Nature and Science Monographs
No. 51

ISSN 1881-9109

National Museum of Nature and Science Monographs No. 51

THE SUBFAMILY STENINAE MACLEAY, 1825
(COLEOPTERA: STAPHYLINIDAE) OF JAPANPART 2. STENUS ASYURA-GROUP TO
S. CIRRUS-GROUP
Shun-Ichiro NaomiShûhei Nomura
Volker Puthz

National Museum of Nature and Science
Tokyo, August 2019

Editorial Board
Fumitaka Wakabayashi, Editor-in-Chief, Department of Science and Engineering
Toshio Kubota, Managing Editor, Department of Science and Engineering
Ritsuro Miyawaki, Principal Editor, Department of Geology and Paleontology
Megumi Saito-Kato, Principal Editor, Department of Geology and Paleontology
Toshiaki Kuramochi, Department of Zoology
Shoji Hamao, Department of Zoology
Masanobu Higuchi, Department of Botany
Yoshihito Ohmura, Department of Botany
Ken-ichi Shinoda, Department of Anthropology
Kazuhiro Sakaue, Department of Anthropology
Yasunori Sato, Institute for Nature Study
Makoto Manabe, Collection Center

National Museum of Nature and Science
Ueno Park, Tokyo, 110–8718
Japan
Copyright ©2019
National Museum of Nature and Science, Tokyo
Published on 1 February, 2019
Printed by International Academic Publishing Co., Ltd., Tokyo
ISSN 1881-9109
ISBN 978-4-87803-045-1

		v

CONTENTS

Abstract......................................................................................................................................... 1
Introduction .................................................................................................................................. 1
Materials and Methods ................................................................................................................ 1
Characters Used for the Taxonomy of Steninae ........................................................................ 2
Methods of Characterizations, Descriptions and Illustrations ................................................ 3
Taxonomy and Descriptions ........................................................................................................ 5
Genus Stenus Lateille, 1797....................................................................................................... 5
Species-group of S. asyura Naomi......................................................................................... 5
A list of the species of S. asyura-group ............................................................................. 7
The kasumi-subgroup ......................................................................................................... 9
The asyura-subgroup ....................................................................................................... 53
The oni-subgroup ........................................................................................................... 106
Incertae sedis ................................................................................................................. 127
Species-group of S. indubius Sharp ................................................................................... 130
A list of the species of S. indubius-group ...................................................................... 131
The inimitabilis-subgroup .............................................................................................. 133
The indubius-subgroup .................................................................................................. 142
Species-group of S. ﬂammeus Tang & Puthz ..................................................................... 198
A list of the species of S. ﬂammeus-group ..................................................................... 199
The ﬂammeus-group....................................................................................................... 199
Species-group of S. cirrus Benick ..................................................................................... 206
A list of the species of S. cirrus-group ........................................................................... 207
The cirrus-group ............................................................................................................ 209
Acknowledgements .................................................................................................................. 242
References ................................................................................................................................. 243
Corrigenda and Addenda to the Steninae of Japan Part 1 .................................................. 247
Habitus Figures ........................................................................................................................ 248

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

Abstract This is the second part of a monographic study of the subfamilial-level clade Steninae
Macleay, 1825 (Coleoptera: Staphylinidae) of Japan. It treats taxonomically four Asian speciesgroups of the genus Stenus Latreille, 1797 and their Japanese species: asyura-group (54 species),
indubius-group (29 species), ﬂammeus-group (3 species) and cirrus-group (15 species). The known
species of Stenus treated here all are redescribed; and the following 6 Stenus species are described as
new to science: S. kisomontanus (Nagano Pref.); S. scissilis (Gifu Pref.); S. uncinatus (Gifu Pref.); S.
campaniformis (Yamagata Pref.); S. tuberascens (Fukui Pref.); and S. angusticulus (Ehime Pref.).
Keys to the species of Stenus treated here are given, together with the detailed illustrations of the taxonomically important structures of all species, and with the habitus photos of the 92 species of Japanand the 4 species of East Asia.

Introduction
This is the second part of our monographic studies, in which we aim at clarifying the Japanese fauna of the subfamily Steninae Macleay, 1825 of Staphylinidae (Coleoptera). In the second
part (Puthz: Contribution No. 356 on Steninae; Naomi: Contribution No. 59 on Steninae), four
Asian species-groups of Stenus (asyura-group, indubius-group, ﬂammeus-group and cirrusgroup) are treated taxonomically, which comprise 101 species from Japan. All known Japanese
species of these 4 species-groups are redescribed; and 6 new species are described, together withkeys to the species. The taxonomically important structures are illustrated in detail for all Stenus
species treated; and the habitus photos are also given for the 92 species of Japan and the 4 species of East Asia.
Materials and Methods
Holotypes of the all species of Stenus treated here are examined by Naomi and/or Puthz.
Depositories of the type specimens are as follows:

2

Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

Institutions
AACO: Agriculture and Agrifood Canada, Ottawa
CBM: Natural History Museum and Institute, Chiba
KUF: Kyushu University, Fukuoka
EUMM: Ehime University Museum, Matsuyama
FMC: Field Museum of Natural History, Chicago
MHNG: Muséum dʼhistoire naturelle, Genève
NHML: Natural History Museum, London
NHMW: Naturhistorisches Museum Wien
NMNST: National Museum of Nature and Science, Tsukuba
NMP: National Museum of Prague—Natural History Museum
OMNH: Osaka Museum of Natural History, Osaka
SMNS: Staatliches Museum für Naturkunde, Stuttgart
TUAA: Tokyo University of Agriculture, Atsugi
Private collections
cN: Collection of Shun-Ichiro Naomi, Chiba
cP: Collection of Volker Puthz, Schlitz
cZ: Collection of Lother Zerche, Eberswalde
As far as the methods of the dissection for observation and illustration, see Naomi et al.
(2017: 4–5).
Characters Used for the Taxonomy of Steninae
The characters used in the Part 2 of the Japanese Steninae monograph are basically the sameas in the Part 1 (Naomi et al., 2017: 5–20). However, since we observed several new aedeagal
structures in some species of Stenus examined in the Part 2, we here describe these new structures as taxonomic characters, and newly use them for the descriptions of species, in which they
are found. Furthermore, during the course of our Stenus studies for the Part 2, we ﬁrst clearly
identiﬁed the bursa copulatrix in the postabdominal chamber of female Stenus. Thus, we alsomention the bursa copulatrix.
Aedeagal median lobe
When the aedeagal median lobe has a small process-like structure at the apicomedian part, it
was termed “apicomedian projection” in the Part 1 (Naomi et al., 2017; ﬁg. 5A). On the other
hand, in the many advanced members of asyura-group, the median lobe is tricuspidate at apex by
the 3 teeth, which are more or less pointed. Out of these 3 teeth, the median one is here called
median cusp, while the lateral ones are called lateral cusps. In this paper, we do not discuss thematter as to whether or not the apicomedian projection is homologous with the median cusp in
Stenus.
Endophallic dorsal membrane
There exists the characteristically dotted membrane which is dorsal to the endophallic copulatory tube in several species of the asyura-group (Fig. 26E) and indubius-group (Fig. 61H).
Since it is dorsal in position in the chamber of aedeagal media lobe, it is here called “dorsal

The Steninae of Japan Part 2

3

membrane” for the sake of description.
Endophallic copulatory tube
In most species of Stenus, the main tube of a copulatory tube is simple (i.e., not divided into
the basal and apical tubes; Fig. 60B), or it is more or less divided into the basal and apical tubes
without modiﬁcation (Fig. 3E), or with modiﬁcations (e.g., lateral processes; Fig. 17B). However, in S. ohishii and S. fusciceps (indubius-group), the main tube of a copulatory tube is different in structure from these forms. Namely, it is double-structured by the inner and outer tubes;
and a thin, inner tube exists or runs inside the outer tube (Figs. 80E, 81H).
Bursa copulatrix and the opening (basal pouch) of spermatheca
When observing the proximal part of a spermatheca in the female Stenus, we often obviously
see a sack, which is usually subconical or conical. The sack has been often called infundibulum(Puthz, 2005), basal pouch (Naomi, 2006a; etc.), etc. in the previous studies of Steninae. The
sack certainly forms the opening of a spermathecal duct, but it was found that it usually almost
completely overlaps dorsoventrally with the “bursa copulatrix” (Naomi, 2018a). Morphologicallyspeaking, the bursa copulatrix is a genital structure of female that is completely different fromthe opening of a spermathecal duct. Thus, we need to recognize them separately in the descriptive studies. Namely, the bursa copulatrix is dorsal in position, relative to the basal pouch (e.g.,
Figs. 85D, 86D). The bursa copulatrix is the receptacle, to which the apex of aedeagal median
lobe of male is inserted, for ﬁxing the median lobe in the female genital chamber during copulation, while the basal pouch is the opening of a spermathecal duct, into which the endophallic
copulatory tube is inserted, for depositing a spermatophore there (Naomi, 2018a).
Methods of Characterizations, Descriptions and Illustrations
As in the Part 1 of the Japanese Steninae monograph, the species-groups of Stenus treated arecharacterized (or diagnosed) in the Part 2; and the species treated are redescribed or newly
described, together with the keys to the species, the illustrations of the taxonomically important
structures, and the habitus photos. See at base “Methods of descriptions and illustrations” (Naomiet al., 2017: 20–21), regarding the methods of descriptions and illustrations in the Part 2.
Being different from the Part 1, the species-groups of Stenus treated (i.e., asyura-group,
indubius-group, ﬂammeus-group and cirrus-group) all are, however, Asian species-groups, many
species of which are distributed in the East Asia. Thus, in the Part 2, added for each speciesgroup is a list of all species which belong to each species-group. The research history on eachspecies-group of Stenus is, when necessary, also added in short. Here, in order for readers to see
more precisely how we deal taxonomically with the species in Stenus in the Part 2, we think it
better to take up separately and mention in short the matters with characterizations, “incertae
cedis”, and revised descriptions (for several structures).
Characterizations
The basic idea on how the species-group of Stenus is characterized in the Part 2, is here mentioned in short. It will be good for us staphylinists in a morphology-based taxonomy, if we manage to ﬁnally detect that a species-group of Stenus results in a monophyletic one (with several
autapomorphies), after we have carefully studied all the species of the species-group in question
during the taxonomic study. On the other hand, in cases where we ﬁnd that a species-group in4

Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

question does not seem to possess a set of robust apomorphic characters, we must do our best in
carefully searching the candidates of the morphological characters that will be useful for characterization of the species-group in question, together with a careful survey of the basal (primitive)
species which must belong to the concerned species-group. In such cases we tentatively propose
a combination of several “good” characters of the species-group for the sake of species identiﬁcation.
See Tang & Zhao (2008) and Puthz (2017) for the characterizations of indubius-group; seeTang et al. (2016) for that of ﬂammeus-group; see Puthz (2003a) and Tang et al. (2008) for thoseof cirrus-group. We will ﬁnd their characterizations to be proper. And, we hope that this paper
will contribute to the characterization of the asyura-group.
Incertae cedis
In the case where the taxonomic position of a Stenus-species is uncertain, the species inquestion is treated as “incertae cedis”. The “uncertain” taxonomic position here means that, basedon our taxonomic studies, a Stenus-species cannot be accurately classiﬁed into a species-groupnor its subgroup, to which it should belong. We virtually treated only S. dubitativus as incertae
cedis in the Part 2.
Revised descriptions
In the Part 2, aiming at the concise and more morphologically adequate descriptions of thespecies-groups and species in Stenus, we slightly change the methods of descriptions and also
revise some morphological terms for descriptions. We think it better to add annotations on somemorphological characters.
Hind wings. All Stenus species treated in the Part 2 are brachypterous. Thus, the matter as towhether the Stenus species in question is macropterous or brachypterous, is not mentioned in thedescription of each species.
Lateroventrites. The descriptions of how the lateroventrites develop in the pregenital abdominal segments are useful for species identiﬁcation in Stenus. The typical conditions of the lateroventrites are usually found in the 4th to 6th segments of abdomen in Stenus, and thus they aredescribed for each species treated, without reiterating the phrase “4th to 6th segments of abdomen” in each description.
Ninth tergum of male. The ventral apophysis of male 9th tergum was identiﬁed as the anteroventral extension of antecostal ring in Aleocharinae (Peschke, 1978). The 9th tergum of male in
Steninae is, we think, basically same in structure as in Aleocharinae. Thus, the ventral apophysisof male 9th tergum in Stenus is here termed antecostal apophysis.
Endophallic longitudinal bands. In the endophallus of the aedeagus in Stenus, there exist apair of median longitudinal bands and a pair of lateral longitudinal bands (Naomi et al., 2017).
This is also true of the species treated in the Part 2. In the descriptions of species, the medianlongitudinal bands and the lateral longitudinal bands are abbreviated as “median bands” and “lateral bands”, respectively, for the sake of convenience. Furthermore, the “ventral bands” and the“dorsal bands” of the median bands are here termed the basal bands and the (dorsally) folded
bands, respectively, because in the chamber of median lobe, the median bands are wholly ventral
in position, relative to the copulatory tube.
Endophallic copulatory tube. The endophallic “copulatory piece” of Stenus was, in the Part 1(Naomi et al., 2017, p.15), called “basal tube”, which is composed of the “basal room” and “tubebody” However, it is here newly called “copulatory tube”, following Naomi (2018). Parts of theThe Steninae of Japan Part 2

5

copulatory tube are also newly called as follows: The copulatory tube comprises the “basal
chamber” and “main tube”; and the main tube is divided into the “basal tube” and “apical tube” incases where the basal part (e.g., very thick, rod-like) is distinctly different in structure from theapical part (e.g., thin, attenuate).
Bursa copulatrix and basal pouch of spermatheca. In cases where both the bursa copulatrix
and the basal pouch of spermatheca can be clearly observed in the female of a Stenus-species
treated (e.g., Fig. 85D), we are to describe the bursa copulatrix just after the description of spermathecal structures. However, it is not easy in many cases for us to clearly observe the bursa
copulatrix in the female genital chamber, due to the dorsoventral overlap of it with the basal
pouch of spermatheca. This is so especially in cases where they are not sclerotized and more orless membranous. Thus, if we cannot precisely identify “what we might be able to identify at ﬁrst
sight as the basal structure of spermatheca”, as “bursa copulatrix” or “basal pouch of spermatheca”, we are to simply describe it as “basal structure” after the description of the spermathecal
structures.
Taxonomy and Descriptions
Subfamily Steninae MacLeay, 1825
Genus Stenus Latreille, 1797
Species-group of S. asyura Naomi
The asyura-group is an East Asian species-group of Stenus, which comprises 62 species. The
species of this group are presently distributed only in Japan, Korea and China. This speciesgroup is not characterized by the robust autapomorphies, but it is still considered a natural group,
as discussed below in detail, based on the important apomorphic characters of aedeagal median
lobe (tricuspidation or bifurcation of the apex of aedeagal median lobe), together with the combination of the characters including the unique habitus, coloration, some postabdominal structuresof male and female, etc.
The tenuimargo-group, asyura-group (kasumi-subg., Figs. 102, 103A–F) and indubius-group(Figs. 106, 107, 108A–E) are at base similar to one another not only in their habitus and coloration, but in several other characters (e.g., 9th ventrite of male; 9th gonocoxites of female), suggesting that they seem to be closely allied phylogenetically. The asyura-group is, however, atbase distinctly separable from its allied species-groups by the unique tricuspidate or bifurcate
apex of aedeagal median lobe. The basal (primitive) species of asyura-group (whose median lobe
is not tricuspidate nor bifurcate at apex) are also separable from the species of the allied speciesgroups, by their possession of the habitus, coloration and postabdominal structures which are
unique to the asyura-subgroup. In addition, the asyura-group is separable from the tenuimargogroup by the smaller body size and the shorter antennae and legs; and furthermore, the kasumisubg. and asyura-subg. are also separable from the latter by the Hypostenus-typed abdomen. The
asyura-group is also separable from the indubius-group by the basic form of spermatheca (Figs.
1E. 23C, 46D).
Subgrouping of the asyura-group: The subgrouping of the asyura-group is here taken up,
together with the brief description on the research history of this species-group.
The asyura-group was ﬁrst established by Naomi (1988a), which comprised the following 5
species: S. asyura, S. basara, S. santira, S. bicara and S. kazami; (note here that S. kazami pres-6

Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

ently belongs to the other species-group; unpublished data). Naomi (2012) vaguely referred tothe members of asyua-group, but he characterized the asyua-group as follows: “secondary sexual
characters of abdominal 6th and 7th sternites of male not developed in general; median lobe of
aedeagus broad in general, with its apicolateral corner distinctly angulate”.
In the list of the Japanese Steninae (Naomi & Puthz, 2013), the asyura-group was divided
into the following 4 subgroups: dubitativus-subg., kasumi-subg., oni-subg. (as hannia-subg.
there) and asyura-subg. Out of them, the latter 3 subgroups are here treated as the subgroups ofasyura-group, although the kasumi-subg. and asyura-subg. are here differently recognized intheir members from those treated in Naomi & Puthz (2013). On the other hand, the dubitativussubg. is recognized as a polyphyletic group, so that the members previously classiﬁed there eachshould be adequately reclassiﬁed to the corresponding species-group, to which each belongs. Outof the 14 species of the dubitativus-subg., only 4 species (S. dubitativus; S. incommodus; S.
hayashii; S. nyorai) are recognized as members of asyura-group in the Part 2. S. dubitativus itself
is tentatively treated as incertae cedis in the asyura-group. In this paper, the asyura-group is thus
constituted by the following 3 subgroups: kasumi-subg., asyura-subg. and oni-subg.
Diagnostic characters of the asyura-group: Body elongate, cylindrical, medium-sized (Fig.
102L) to moderately large (Fig. 103F), but often relatively small in asyura-subg. (Fig. 104L);
coloration: reddish brown (Figs. 103L, 105J) through chocolate brown to dark chocolate brown(Fig. 102L), but often clear yellowish brown to reddish brown in asyura-subg. (Fig. 104L); pronotum with surface having an indistinct median longitudinal furrow (excepting S. scissilis); brachypterous; tarsi each with 4th tarsomere strongly bilobed; 4th to 6th abdominal segments usually without lateroventrites and tergoventrite sutures in the kasumi-subg. and asyura-subg.
(exceptions: e.g., S. clio, S. bishamon having those segments with tergoventrite sutures), or
always with tergoventrite sutures in the oni-subg.
Male: Ninth ventrite with paired macrosetae and pointed apicolateral teeth (Figs. 1B, 21D);
aedeagal median lobe moderately broad to broad even at apicolateral corners (i.e., not or only
weakly narrowed apically in apical 1/2) and distinctly angulate at apicolateral corners (Figs. 2A,
23A), with the apex usually tricuspidate (kasumi-subg. Fig. 3A; and asyura-subg. Fig. 27B) or
bifurcate (oni-subg. Fig. 45C), but showing other diverse forms (e.g., unicuspidate in S. unicuspidatus Fig. 11G; bicuspidate in S. scissilis Fig. 10C; simply pointed in S. nyorai and some otherspecies Fig. 8C; etc.); endophallus usually with expulsion hooks and copulatory tube well-developed (Figs. 1F, 21E).
Female: Gonocoxites each with a pointed apicolateral tooth (Figs. 1G, 21F); spermathecahaving the basic form (Naomi et al., 2017: ﬁg. 7A), usually with capsule very small to small, RTduct more or less thicker than spermathecal duct, the spermathecal duct usually moderately long
(Fig. 1E) to very long (Fig. 8D) but sometimes short with 2 turns (Fig. 2F).
Naturalness of the asyura-group: In many species of the kasumi-subg. (14 out of 21 species) and asyura-subg. (17 out of 30 species), the apex of aedeagal median lobe is tricuspidate(Figs. 3A, 7D, 12D, 27B, 39B); and the tricuspidation has only rarely occurred at the apex ofmedian lobe in the other East Asian and Oriental species-groups of Stenus: indubius-group (e.g.,
S. inimitabilis, S. sawadai). No tricuspidation has hitherto been observed in the species of thetenuimargo-group. Such a biased distributional pattern of the tricuspidate condition in the East
Asian and Oriental species-groups of Stenus shows that the tricuspidation can be no doubt
assessed as an important apomorphic condition for the asyura-group.
The oni-subg. is basically equal in almost all external structures and coloration Fig. 105E–K
to some members of the kasumi-subg. and asyura-subg.; and thus it should be included in theThe Steninae of Japan Part 2

7asyura-group. However, the oni-subg. has, interestingly, the aedeagus with the bifurcated apex
(Fig. 46E; instead of the tricuspidate apex). The tricuspidate apex of median lobe is supposed tohave secondarily lost at the same time when the bifurcated apex has instead evolved.
As a result, the asyura-group will be perhaps considered a natural species-group of Stenus,
based on the unique combination of the unique habitus, coloration, and some important postabdominal structures of male and female (described above), in addition to the afore-mentioned
morphological facts: Namely, many species of kasumi-subg. and asyura-subg. possess the aedeagal apomorphic characters (i.e., median lobe moderately broad to broad even at the apicolateralcorners, with the tricuspidate apex), while all species of oni-subg. possess the aedeagal apomorphic character (i.e., the median lobe characteristically bifurcate at apex).
A list of the species of S. asyura-groupkasumi-subgroup
nomuraianus Puthz, 2012 Distribution: Korea (Chungcheongbuk; Geongsangnam)
hayashii Puthz, 2003 Distribution: Japan (Honshu)
incommodus Puthz, 1993a Distribution: Japan (Honshu)
davidhulli Naomi, 2015 Distribution: Japan (Honshu)
inbecillus Naomi, 2015 Distribution: Japan (Honshu)
bishamon Naomi, 1998a Distribution: Japan (Shikoku)
carura Naomi, 1989 Distribution: Japan (Shikoku)
trispinosus Naomi & Nomura, 2015 Distribution: Japan (Honshu)
nyorai Naomi, 1990 Distribution: Japan (Honshu)=geisha Puthz, 2001akisomontanus Naomi, Nomura & Puthz sp. nov. Distribution: Japan (Honshu)
scissilis Naomi, Nomura & Puthz sp. nov. Distribution: Japan (Honshu)
unicuspidatus Naomi & Nomura, 2015 Distribution: Japan (Honshu)
kasumi Naomi, 1987 Distribution: Japan (Honshu)
yatsugatakensis Naomi, 2015 Distribution: Japan (Honshu)
sawadaiellus Naomi & Puthz, 1994 Distribution: Japan (Honshu)
uncinatus Naomi, Nomura & Puthz sp. nov. Distribution: Japan (Honshu)
inaequatus Puthz, 1993a Distribution: Japan (Honshu)
houou Naomi, 2010 Distribution: Japan (Honshu)
yasuhikoiellus Naomi, 2010 Distribution: Japan (Honshu)
kumoma Naomi, 1987 Distribution: Japan (Honshu)
izanagi Naomi & Puthz, 1994 Distribution: Japan (Honshu)
asyura-subgroup
dongbaishanus Tang, Liu & Zhao, 2017 Distribution: China (Zhejiang)
gajisanensis Oh & Cho, 2017 Distribution: Korea (Gyeongnam, Chungbuk)
suryongensis Oh & Cho, 2017 Distribution: Korea (Chungbuk, Gyeongbuk)
foliaceus Oh & Cho, 2017 Distribution: Korea (Chungnam, Chungbuk)
fusciformis Oh & Cho, 2017 Distribution: Korea (Jeonnam)
brendelli Naomi, 1997 Distribution: Japan (Kyushu)
ruricoralis Naomi, 1998 Distribution: Japan (Kyushu)
clio Naomi Distribution: Japan (Honshu)

8Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

komonoensis Naomi, 2015 Distribution: Japan (Honshu)
anfractus Naomi, 2015 Distribution: Japan (Honshu)
hijiri Naomi, 1989 Distribution: Japan (Honshu)
maruyamai Naomi, 2004a Distribution: Japan (Honshu)
oisami Naomi & Puthz, 1994 Distribution: Japan (Honshu)
biwa Hromádka, 1980 Distribution: Japan (Honshu)
bicara Naomi, 1988a Distribution: Japan (Honshu)
araiorum Naomi, 2015 Distribution: Japan (Honshu)
jurojin Naomi, 2004a Distribution: Japan (Honshu)
tsukubamontis Naomi, Nomura & Kamezawa, 2015 Distribution: Japan (Honshu)
santira Naomi, 1988a Distribution: Japan (Honshu)=tengu Hromádka
ellipsoides Naomi, 2015 Distribution: Japan (Honshu)
protuberans Naomi & Watanabe, 2015 Distribution: Japan (Honshu)
fulvivestis Naomi & Watanabe, 2015 Distribution: Japan (Honshu)
basara Naomi, 1988a Distribution: Japan (Honshu)
asyura Naomi, 1988a Distribution: Japan (Honshu)
hakonensis Naomi, 2004b Distribution: Japan (Honshu)
nogohakusanus Naomi, Nomura & Kamezawa, 2015 Distribution: Japan (Honshu)
yukawai Naomi, 2004c Distribution: Japan (Honshu)
alesi Naomi, 2015 Distribution: Japan (Honshu)
daikoku Naomi, 2004b Distribution: Japan (Honshu)
oni-subgroup (=hannia-subgroup)
praeclarus Naomi, 2005 Distribution: Japan (Shikoku)
hannia Naomi, 1990a Distribution: Japan (Honshu)
naturalis Naomi & Watanabe, 2015 Distribution: Japan (Honshu)
zdenae Hromádka, 1990 Distribution: Japan (Honshu)
bunraku Hromádka, 1990 Distribution: Japan (Honshu)
haginoi Naomi, 1997a Distribution: Japan (Honshu)
oni Naomi, 1988a Distribution: Japan (Honshu)
triprotrudens Naomi & Watanabe, 2015 Distribution: Japan (Honshu)
protrudens Naomi & Watanabe, 2015 Distribution: Japan (Honshu)
incertae sedis
sulcifer Oh & Cho, 2016 Distribution: Korea (Ganwon)
dubitativus Puthz, 1993 Distribution: Japan (Kyushu: Amami Is.)
Japanese fauna of the asyura-group
The asyura-group consists of 54 species in Japan. The Japanese species are classiﬁed into the
3 subgroups (kasumi-subg.:20 species; asyura-subg.: 24 species; and oni-subg. 9 species) andinsertae cedis (1 species). All of these species are indigenous to the Japanese Archipelago.

The Steninae of Japan Part 2

9The kasumi-subgroup
The kasumi-subg. was only recently ﬁrst recognized as a subgroup (14 species) of the asyura-group in the list of Japanese Steninae (Naomi & Puthz, 2013), but the diagnostic characters
were not described there. At present, this subgroup comprises 20 species in Japan; and it is hereﬁrst characterized as below. Although the good apomorphic characters are not found for thewhole subgroup, the 9 derived species (S. kasumi, S. yatsugatakensis, S. sawadaiellus, S. uncinatus, S. inaequatus, S. houou, S. yasuhikoiellus, S. kumoma, S. izanagi) are certainly well-characterized by the highly apomorphic conditions of endophallic copulatory tube as mentioned below.
The 9 basal members are considered to belong to the kasumi-subg., because the habitus, coloration and also the several important aedeagal characters (e.g., shape of median lobe, endophallic
expulsion hooks, copulatory tube) are more or less similar in their conditions to those of thederived members.
Diagnostic characters of the kasumi-subgroup: Habitus (Figs., 102L, 108I) similar to thespecies of indubius-subg.; antennae usually moderately long; abdomen without lateroventrites
nor tergoventrite sutures in 4th to 6th segments (Hypostenus-type). Male: Endophallic expulsion
hooks well-developed, large, each hook usually broad, with anterior plate rounded (Fig. 2D) or
pointed (Fig. 9G); copulatory tube with main tube simply attenuate (Fig. 7E) or its basal and apical tubes more or less demarcated by a constriction (Fig. 3E) in the basal members, while theadvanced members are well-diagnosed as follows: Copulatory tube with the whole main tube
(Fig. 17B) or the apical part of main tube (Fig. 14A) rhombic or sub-rhombic in shape, usually
reinforced by paired lateral processes and paired apical processes, in addition to the membranefound between the lateral and apical processes. (Note here that the paired lateral processes of
copulatory tube are possessed also by a basal member S. carura; Fig. 6E). Female: Gonocoxitewith apicolateral tooth acutely pointed, apicolateral setae very long (Fig. 8F); spermatheca variously formed from the duct short with 2 distinct turns (Fig. 2F), through moderately long andcoiled (Fig. 1E) or very long and strongly coiled (Fig. 7C).
Key to the Japanese species of the kasumi-subgroup1(12) Male: Aedeagal median lobe more or less simply pointed or bicuspidate at apex.
2(3) Male: Aedeagal median lobe bicuspidate at apex (Fig. 10C) ...............................................
........................................................................ S. scissilis Naomi, Nomura & Puthz sp. nov.
3(2) Male: Aedeagal median lobe more or less simply pointed.
4(9) Male: Aedeagal median lobe narrowed apically from the middle to the apicolateral corners, with its apicolateral corner rounded or obtusely angulate.
5(8) Male: Endophallic expulsion hooks connected at posteromesial corners, each with posterior plate shorter, broader. Female: Spermathecal duct shorter, thicker.
6(7) Male: Endophallic copulatory tube with main tube swollen at apex (Fig. 1F). Female:
Spermatheca with capsule larger, duct longer with 6 turns (Fig. 1E) ....... S. hayashii Puthz
7(6) Male: Endophallic copulatory tube with main tube simply thin at apex (Fig. 2E). Female:
Spermatheca with capsule smaller, duct shorter with 2 turns (Fig. 2F) ................................
.............................................................................................................S. incommodus Puthz
8(5) Male: Endophallic expulsion hooks connected at anteromesial corners, each with posterior
plate longer, narrower (Fig. 8G). Female: Spermathecal duct longer, thinner (Fig. 8D) .......
.....................................................................................................................S. nyorai Naomi

10

9(4)

Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

Male: Aedeagal median lobe almost parallel-sided from the middle to the apicolateralcorners, with its apicolateral corner more or less angulate.
10(11) Male: Aedeagal median lobe narrower, bluntly pointed at apex (Fig. 9D); endophallic
copulatory tube attenuate but strongly curved at apex (Fig. 9F) ..........................................
...............................................................S. kisomontanus Naomi, Nomura & Puthz sp. nov.
11(10) Male: Aedeagal median lobe broader, distinctly unicuspidate at apex (Fig. 11G); endophallic copulatory tube attenuate and only very weakly curved at its full length (Fig. 11G)........
.......................................................................................S. unicuspidatus Naomi & Nomura
12(1) Male: Aedeagal median lobe tri-angulate or tricuspidate at apex.
13(22) Male: Endophallic copulatory tube with main tube not rhombic nor subrhombic.
14(21) Male: Legs with femora thinner; endophallic copulatory tube with main tube more or lessbaculiform, narrowed apically.
15(18) Male: Aedeagus median lobe with 3 apical cusps located apically and the incision
between median cusp and lateral cusp broader.
16(17) Male: Aedeagal median lobe with median cusp smaller (Fig. 3A); endophallic expulsion
hooks developed (Fig. 3A). Female: Spermathecal duct shorter and thicker (Fig. 3C) .......
............................................................................................................... S. davidhulli Naomi
17(16) Male: Aedeagal median lobe with median cusp larger (Fig. 6E); endophallic expulsion
hooks atrophied (Fig. 6E). Female: Spermathecal duct longer and thinner (Fig. 6A) ..........
................................................................................................................S. inbecillus Naomi
18(15) Male: Aedeagus median lobe with 3 apical cusps located apicomedially and the incision
between apical cusp and lateral cusp narrower.
19(20) Male: Aedeagal median lobe with apical sclerotized area longer and median cusp larger
than lateral cusps (Fig. 7B); paramere longer (Fig. 7B). Female: Spermathecal duct much
shorter and thicker (Fig. 7E) ..................................................................S. bishamon Naomi
20(19) Male: Aedeagal median lobe with apical sclerotized area shorter and median cusp equalin size and shape to lateral cusps (Fig. 9D); paramere shorter (Fig. 7D). Female: Spermathecal duct much longer and thinner (Fig. 9C) ................. S. trispinosus Naomi & Nomura
21(14) Male: Legs with femora thicker; endophallic copulatory tube with main tube nearlyY-shaped (Fig. 8E) ..................................................................................... S. carura Naomi
22(13) Male: Endophallic copulatory tube with the whole main tube or the apical part of maintube almost rhombic or subrhombic.
23(36) Male: Aedeagal paramere with apical area mesially not having ﬂaps; endophallic copulatory tube with apical area narrower.
24(27) Male: Endophallic copulatory tube without lateral processes.
25(26) Male: Aedeagal median lobe with median cusp longer (Fig. 12D); endophallic copulatory
tube with apical processes not or hardly divided right and left, opened ventrally (Fig.
12E) ............................................................................................................S. kasumi Naomi
26(25) Male: Aedeagal median lobe with median cusp shorter (Fig. 18C); endophallic copulatory
tube with apical processes deeply bifurcate apically, closed ventrally (Fig. 18E)................
........................................................................................................ S. yasuhikoiellus Naomi
27(24) Male: Endophallic copulatory tube with lateral processes.
28(29) Male: Aedeagal median lobe rounded at apicolateral corners (Fig. 15A) ............................
..................................................................... S. uncinatus Naomi, Nomura & Puthz sp. nov.
29(28) Male: Aedeagal median lobe more or less angulate at apicolateral corners.
30(31) Male: Endophallic expulsion hook with anterior plate acutely pointed at apex (Fig. 17F) ..

The Steninae of Japan Part 2

11..................................................................................................................... S. houou Naomi
31(30) Male: Endophallic expulsion hook with anterior plate obtusely angulate at apex.
32(33) Male: Aedeagus median lobe with apical sclerotized area longer (Fig. 16A); endophallic
expulsion hook with posterior plate broader, more weakly, arcuately emarginate at lateralside (Fig. 16F) ....................................................................................... S. inaequatus Puthz
33(32) Male: Aedeagus median lobe with apical sclerotized area shorter; endophallic expulsion
hook with posterior plate narrower, more strongly, arcuately emarginate at lateral side.
34(35) Male: Aedeagal median lobe with median cusp longer (Fig. 13C); endophallic copulatory
tube with apical subrhombic area larger (Fig. 13E) .....................S. yatsugatakensis Naomi
35(34) Male: Aedeagal median lobe with median cusp shorter (Fig. 14C); endophallic copulatory
tube with apical subrhombic area smaller (Fig. 14A) ........ S. sawadaiellus Naomi & Puthz
36(23) Male: Aedeagal paramere with apical area mesially having dorsal and ventral ﬂaps; endophallic copulatory tube with apical area broader.
37(38) Male: Endophallic expulsion hook with its posterior plate subtriangular (Fig. 19C); copulatory tube with its basal chamber ovoidal (Fig. 19E). Female: spermatheca with its duct
longer and thinner (Fig. 19B)...................................................................S. kumoma Naomi
38(37) Male: Endophallic expulsion hook with its posterior plate almost C-shaped (Fig. 18C);
copulatory tube with its basal chamber almost missing (Fig. 20D). Female: spermathecawith its duct shorter and thicker (Fig. 20A) ................................ S. izanagi Naomi & Puthz
Stenus hayashii Puthz(Figs. 1A–G, 102A)
Stenus hayashii Puthz, 2003: 17; Naomi & Puthz, 2013: 142.
Type material examined. Holotype: ♂ (SMNS), Dorogawa, Nara Pref., 15. vii. 2000, Y.
Hayashi leg.
Other material examined. [HONSHU]: 3 ♂1 ♀, Oomine, Nara Pref. (Yamato), 1. vi. 1985, T.
Ito leg.; 1 ♀, Mt. Wasamata, Nara Pref. (Yamato), 14–15. vi. 1997, T. Ito leg.
Distribution. Japan: Honshu (Nara Pref.).
Redescription. Male and female: Body 4.5–4.6 mm (fore body 2.0–2.1 mm) in length, moderately shining, with antennae relatively short, very thin, legs relatively short. Head black; pronotumand elytra reddish chocolate brown; abdomen dark chocolate brown; labrum reddish brown; antennae reddish brown to dark reddish brown; legs reddish brown. Head weakly concave, with a pair ofdistinct, longitudinal furrows; punctures round, sparse to moderately dense, very small to small,somewhat irregular. Pronotum with surface weakly uneven, with indistinct median longitudinal furrow; punctures very dense, moderately large, coarse, somewhat subrugose. Elytra with surface
uneven, almost ﬂat near suture; punctures very dense, coarse, subrugose. Tarsi each with 4th tarsomere strongly bilobed. Abdomen with punctures round to elliptical, moderately dense, small but a
bit various in size, shallow in anterior segments, while posterior segments hardly or only indistinctly punctate. Lateroventrites missing; tergoventrite sutures almost missing or very thin.
Male: Sixth ventrite (Fig. 1C) posteromedially with a semicircular ﬂat area; 7th ventrite (Fig.
1C) posteromedially with an elongate bell-shaped, shallow depression, which is very shallowly
emarginate; 8th ventrite (Fig. 1C) posteriorly with a small emargination; 9th tergum (Fig. 1A)
with antecostal apophyses long; 9th ventrite (Fig. 1B) minutely serrate posteriorly, with macrosetae short, apicolateral teeth acutely pointed, apicolateral setae long; 10th tergum (Fig. 1A) very

12Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

Fig. 1. Stenus hayashii Puthz (A–E, G, Oomine, Nara; F, Dorogawa, Nara). A, 9th and 10th terga of male; B, 9th
ventrite of male; C, 6th to 8th ventrites of male; D, expulsion hooks; E, spermatheca; F, aedeagus; G, posterior
part of gonocoxite. Scale 1: 0.2 mm for A, B, 0.1 mm for D, G; Scale 2: 0.3 mm for C; Scale 3: 0.05 mm for
E; Scale 4: 0.1 mm for F.

The Steninae of Japan Part 2

13

shallowly emarginate. Aedeagal median lobe (Fig. 1F) elongate, uniformly rounded apicolaterally, with pointed apex; apical sclerotized area (Fig. 1F) triangular, relatively narrow. Endophallic median bands (Fig. 1F) broad, each with basal band longer than folded band; lateral bands(Fig. 1F) very thin; expulsion hooks (Fig. 1D) connected at the posteromesial corners, each hooklarge, thick, with anterior plate partially separated by a transverse cleft from posterior plate, theposterior plate turning posterolaterally; copulatory tube (Fig. 1F) long, stout, main tube thick,strongly constricted near the apical 1/3, with apical area fusiform. Parameres (Fig. 1F) each long,almost straight, very acutely pointed at apex; apical area long, hardly swollen mesially, furnishedbasally with a tuft of 4 to 5 setae, mesially with 5 to 6 moderately long setae.
Female: Eighth ventrite simply pointed posteromedially; gonocoxites (Fig. 1G) toothed posteriorly, each with apicolateral tooth very long, acutely pointed, apicolateral setae very long.
Spermatheca (Fig. 1E) with capsule subovoidal, moderately large; RT-duct short, moderately
thick; duct long, relatively loosely coiled, with 6 turns; basal valve very short, basal sclerotizedduct longer than basal valve.
Biology and ecology. S. hayashii is distributed in the mountainous regions of Kinki district,Honshu. The beetles inhabit leaf litter in the natural forest.
Remarks. S. hayashii is allied to S. incommodus, but it is separable from the latter species by
the endophallic copulatory tube with its main tube fusiform at the apical part (Fig. 1F), and thespermatheca with its capsule larger and its duct longer, with 6 turns (Fig. 1E).
Etymology. This species is named in honor of Mr. Yasuhiko Hayashi (Kawanishi, Hyogo),
who studies the Staphylinidae and related groups.
Stenus incommodus Puthz(Figs. 2A–G, 102B)
Stenus incommodus Puthz, 1993a: 146; Herman, 2001: 2229; Naomi & Puthz, 2013: 142.
Type material examined. Holotype: ♂ (MHNG), Seryo Pass, Kyoto, 6. viii. 1980, I. Löbl leg.
Other material examined. [HONSHU]: 1 ♂, Kamijyohou-ji, Eiheiji-cho, Fukui Pref., 9. v.
2010, M. Saito leg.; 1 ♀, Mt. Kunimi, Fukui Pref., 13. vi. 1982, T. Ito leg.; 2 ♂2 ♀, Hanase,
Kyoto-fu, 4. vii. 1987, T. Ito leg.; 1 ♂, Kibune, Kyoto-fu, 1. vi. 1958, Y. Hayashi leg.; 1 ♂,Kurama, Kyoto-fu, 28. v. 1994, T. Ito leg.; 1 ♂1 ♀, Ashiu, Kyoto-fu, 12. vi. 1999, Y. Hayashi
leg.; 1 ♂2 ♀, Syuzan, Kyoto-fu, 3. xi. 1979, T. Ito leg.; 1 ♂, Yawata C., Kyoto-fu, 7. xii. 1986, T.
Ito leg.; 2 ♂, Sasayama, Sanda, Hyogo Pref., 26. iv. 1998, T. Ito leg.
Distribution. Japan: Honshu (Chubu and Kinki districts).
Redescription. Male and female: Body 4.0–4.5 mm (fore body 1.9–2.1 mm) in length, moderately shining, with antennae moderately long, very thin. Head black; pronotum and elytra reddish chocolate brown; abdomen dark chocolate brown; labrum reddish brown to dark red; antennae and legs yellowish brown to reddish brown. Head weakly concave, with a pair of
longitudinal furrows; punctures round, sparse to moderately dense, small, somewhat umbilicate.
Pronotum with surface weakly uneven, with indistinct median longitudinal furrow; puncturesround to elliptical, very dense, various in size, somewhat coarse, two or more punctures sometimes partially fused. Elytra with surface weakly uneven, almost ﬂat near suture; punctures roundto elliptical, very dense, various in size, somewhat coarse. Tarsi each with 4th tarsomere strongly
bilobed. Abdomen with punctures round to elliptical, moderately dense to dense, small, distinct
in anterior segments, while punctures in posterior segments indistinct (i.e., socket hardly concave

14

Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

Fig. 2. Stenus incommodus Puthz (A, F, G, Hanase, Kyoto; B, E, Sasayama, Hyogo; C, D, Kurama, Kyoto). A,
6th to 8th ventrites of male; B, 9th ventrite of male; C, 9th and 10th terga of male; D, expulsion hooks; E,
aedeagus; F, spermatheca; G, posterior part of gonocoxite. Scale 1: 0.3 mm for A; Scale 2: 0.2 mm for B, E,
0.1 mm for G; Scale 3: 0.2 mm for C, 0.1 mm for F.

The Steninae of Japan Part 2

15

at the base of each pubescence). Lateroventrites and tergoventrite sutures missing.
Male: Sixth ventrite (Fig. 2A) posteromedially with a bell-shaped, shallow depression, which
is very shallowly emarginate; 7th ventrite (Fig. 2A) posteromedially with a large, moderately
deep depression, which is arcuately emarginate; 8th ventrite (Fig. 2A) posteriorly with amedium-sized emargination; 9th tergum (Fig. 2C) with antecostal apophyses long; 9th ventrite(Fig. 2B) minutely or hardly serrate posteriorly, with macrosetae long, apicolateral teeth acutely
pointed, apicolateral setae moderately long; 10th tergum (Fig. 2C) entire. Aedeagal median lobe
(Fig. 2E) moderately broad, almost distinctly angulate apicolaterally, acutely pointed at apex;
apical sclerotized area (Fig. 2E) triangular with median longitudinal suture, bidentate at anterior
margin. Endophallic median bands (Fig. 2E) broad, each with basal band distinctly longer thanfolded band; lateral bands (Fig. 2E) very thin; expulsion hooks (Fig. 2D) connected at the posteromesial corners, each hook large, thick, with anterior plate almost wholly hollowed ventrally,rounded anteriorly, partially separated by a midlateral ridge from posterior plate, the posterior
plate projecting posterolaterally; copulatory tube (Fig. 2E) very long, stout, with basal chamberlarge, almost ovoidal, main tube with basal tube thick, apical tube thin. Parameres (Fig. 2E) very
long, each weakly curved laterally behind the base of apical area, pointed apically; apical area
very long, weakly swollen mesially, furnished basally with a tuft of 5 to 6 setae, mesially with 7
to 8 setae of different length.
Female: Seventh ventrite medially with an elongate-elliptical, very shallow depression or ﬂatarea; 8th ventrite indistinctly angulate posteromedially; gonocoxites (Fig. 2G) toothed posteriorly, each with apicolateral tooth long, acutely pointed, apicolateral setae very long. Spermatheca(Fig. 2F) with capsule small; RT-duct short to moderately long, thin; duct short with two distinct
turns; basal valve short; basal sclerotized duct a little longer than basal valve.
Biology and ecology. S. incommodus is distributed in the plains and low mountainous
regions of Kinki district and its neighboring areas, Honshu. The beetles inhabit leaf litter in thenatural forest.
Remarks. S. incommodus is allied to S. hayashii, but it is separable from the latter species by
the endophallic copulatory tube with its main tube simply thin at the apical part (Fig. 2E), andthe spermatheca with its capsule smaller and its duct shorter with 2 turns (Fig. 2F).
Stenus davidhulli Naomi(Figs. 3A–F, 102C)
Stenus davidhulli Naomi, 2015: 12.
Type material examined. Holotype: ♂ (CBM), Mt. Hisamatsu, Tottori Pref., 9. vi. 1984, S.
Nomura leg. Paratypes: 2 ♂3 ♀, Akazai, Hyogo Pref., 23. ix. 1979, T. Ito leg.; 3 ♀, same locality,
15. ix. 1986, T. Ito leg.
Other material examined. [HONSHU]: 4 ♂1 ♀, Makura, Maizuru City, Kyoto Pref., 7. iv.
2004, T. Murao leg.
Distribution. Japan: Honshu (Tottori and Kyoto Prefs).
Redescription. Male and female: Body 4.2–4.3 mm (fore body 2.0–2.1 mm) in length, moderately or strongly shining, with antennae moderately long, very thin. Head black; pronotum, elytra and abdomen reddish brown to dark reddish brown; labrum reddish brown; antennae and legs
yellowish brown to reddish brown. Head weakly concave, with a pair of longitudinal furrows;
punctures round, sparse to moderately dense, small, somewhat umbilicate, distinct. Pronotum

16

Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

Fig. 3. Stenus davidhulli Naomi (A, E, F, Kyûshô, Tottori; B–D, Akazai, Hyogo). A, aedeagus; B, 9th ventrite ofmale; C, spermatheca; D, 6th to 8th ventrites of male; E, copulatory tube; F, median bands. Scale 1: 0.2 mm
for A, B, E, F, 0.1 mm for C; Scale 2: 0.3 mm for D.

The Steninae of Japan Part 2

17with surface slightly uneven, with indistinct median longitudinal furrow; punctures round, very
dense, moderately large, coarse. Elytra with surface weakly uneven, almost ﬂat near suture;punctures round to elliptical, very dense, various in size but moderately large in average, somewhat coarse. Tarsi each with 4th tarsomere strongly bilobed. Abdomen with punctures round to
elliptical, moderately dense, small, distinct in anterior segments, while punctures in posterior
segments very ﬁne, sparse. Lateroventrites and tergoventritel sutures missing.
Male: Sixth ventrite (Fig. 3D) posteromedially with a large, semicircular ﬂat area, which isvery shallowly emarginate; 7th ventrite (Fig. 3D) with a very large, moderately deep depression,and posteromedially with a large, broad-triangular emargination; 8th ventrite (Fig. 3D) posteromedially with a V-shaped emargination; 9th tergum with antecostal apophyses thick, short; 9th
ventrite (Fig. 3B) irregularly serrate posteriorly, with macrosetae short, apicolateral teeth short,pointed, apicolateral setae moderately long; 10th tergum entire. Aedeagal median lobe (Fig. 3A)
broad, angulate apicolaterally, tricuspidate at apex; apical sclerotized area (Fig. 3A) transverse,with median cusp moderately long, pointed, lateral cusps weakly developed, blunt. Endophallic
median bands (Fig. 3F) relatively broad, with basal bands long, distinctly divergent anteriorly,
folded band short, narrowed anteriorly; explusion hooks (Fig. 3A) connected at the posteromesial
corners, each with anterior plate demarcated by a transverse suture from posterior plate, the posterior plate shortly projecting posterolaterally; copulatory tube (Fig. 3E) with basal chamber
ovoidal, main tube with basal tube very thick, apical tube baculiform, thin, slightly sinuous.
Parameres (Fig. 3A) each very long, straight, rounded apically; apical area long, moderately
swollen mesially, furnished mesially with 6 to 7 setae of moderate length on the ventro-marginalarea, and with a few short setae on the dorso-marginal area.
Female: Eighth ventrite bluntly pointed posteromedially; gonocoxites each with apicolateral
tooth short, acutely pointed, apicolateral setae very long. Spermatheca (Fig. 3C) robust, with capsule rounded apically; RT-duct very thick, only indistinctly demarcated from spermathecal duct;
duct thick, almost tightly coiled with 4 distinct turns; basal valve short; basal sclerotized duct
stout, long. Basal structure mushroom-shaped.
Biology and ecology. S. davidhulli is distributed in the plains and low mountainous regions.
The beetles inhabit leaf litter in the natural forests.
Remarks. Given that S. davidhulli and S. incommodus have in common the 6th and 7th modiﬁcations of male ventrites, the very long parameres of aedeagus, and the particular structures ofendophallus (expulsion hooks and copulatory tube), they are closely allied phylogenetically.
However, S. davidhulli is separable from the latter species by the aedeagal median lobe tricuspidate at apex (Fig. 3A) and the spermatheca with its duct thicker and longer with 4 turns (Fig.
3C). S. davidhulli is also allied to S. inbecillus, but it is separable from the latter species by theaedeagal median lobe with its 3 apical cusps shorter (Fig. 3A), the endophallic expulsion hooklarger (or not atrophied) (Fig. 3A), the copulatory tube with its main tube thicker (Fig. 3E), andthe spermathecal duct shorter and thicker (Fig. 3C).
Etymology. This species is named in honor of the biophilosopher Dr. David L. Hull (Northwestern University, Evanston).
Stenus inbecillus Naomi(Figs. 4A–F, 102D)
Stenus inbecillus Naomi, 2015: 14.
Stenus sawadaiellus Naomi & Puthz, 1994: 299 (partim).

18

Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

Type material examined. Holotype of S. inbecillus: ♂ (CBM), Nomugi Pass, Nagawa Vil.,
Nagano Pref., 8. viii. 1996, T. Kishimoto leg. Paratypes of S. inbecillus: 2 ♂6 ♀ (cN), Kozodaira,Hinoemata Vil., Fukushima Pref., 26. vii. 1996, S. Naomi leg.; 1 ♂ (cN), Mt. Azuma, Fukushima
Pref., 10. vii. 1985, S. Nomura leg.; 3 ♂1 ♀ (cN), Nakatsugawa, Mt. Azuma, Fukushima Pref.,19. viii. 1996, S. Naomi leg.; 1 ♂ (cN), Renge Spa, Itoigawa City, Niigata Pref., 8. vi. 1990, T.
Kishimoto leg.; 2 ♂ (cN), Mikuni Pass, Niiharu Vil., Gunma Pref., 27. vi. 1997, S. Naomi leg.;1 ♂ (cN), Mihira Pass, Ozegahara, Gunma Pref., 24. vii. 1995, H. Tamura leg.; 1 ♂, Near
Marunuma, Gunma Pref., 7. ix. 1965, Y. Watanabe leg.; 1 ♂ (cN), Yumoto, Nikko, Tochigi Pref.,10. vii. 1994, S. Naomi leg.; 1 ♂, near Marunuma, Nikko, Tochigi Pref., 19. viii. 1991, Y. Shibata leg.; 5 ♀ (cN), same data as holotype; 2 ♂2 ♀, Mt. Ontake, Kiso, Nagano Pref., 25. vii.
1986, T. Ito leg.
Paratypes of S. sawadaiellus: 1 ♂1 ♀ (cN), Nigorigo Spa, Gifu Pref., 22. ix. 1972, R. Yosii
leg.
Distribution. Japan: Honshu (Tohoku, Chubu and Kanto districts).
Redescription. Male and female: Body 3.6–4.5 mm (fore body 1.8–2.3 mm) in length, moderately shining, with antennae moderately long, thin. Head and abdomen reddish brown to darkbrown; pronotum and elytra yellowish brown to reddish brown; labrum, antennae and legs clear
yellow to yellowish brown or reddish brown. Head weakly concave, with a pair of longitudinalfurrows; punctures round, moderately dense to dense, small, somewhat umbilicate. Pronotumwith surface slightly uneven, with indistinct median longitudinal furrow; punctures round, very
dense, moderately large, coarse. Elytra with surface uneven, almost ﬂat near suture; puncturesround to elliptical, very dense, medium-sized to moderately large, somewhat coarse. Tarsi eachwith 4th tarsomere strongly bilobed. Abdomen with punctures round to almost round, moderately
dense, small in anterior segments, while punctures in posterior segments elliptical, sparse tomoderately dense, very small. Lateroventrites and tergoventrite sutures missing.
Male: Seventh ventrite (Fig. 4F) posteromedially with a subtriangular ﬂat area; 8th ventrite(Fig. 4F) posteromedially with a subtriangular emargination; 9th tergum with antecostal apophyses short, thin; 9th ventrite (Fig. 4B) regularly serrate posteriorly, with macrosetae short, apicolateral teeth very long, acutely pointed, apicolateral setae moderately long; 10th tergum rounded
posteriorly. Aedeagal median lobe (Fig. 4E) moderately broad, constricted near the apical 1/3,
moderately expanded laterally and angulate at apicolateral corners, tricuspidate at apex; apicalsclerotized area (Fig. 4E) anteriorly with a pair of small teeth, medially with a longitudinal line,
and with median cusp large, very long, pointed, lateral cusps each bluntly pointed. Endophallic
median bands (Fig. 4E) moderately long, narrow; explusion hooks (Fig. 4E) connected mesially,
atrophied into very small sclerites; copulatory tube (Fig. 4E) moderately long, with basal chamber long, comprising two rods, main tube short, thin, straight, attenuate. Parameres (Fig. 4E)
each very long, slender, slightly incurved, pointed apically; apical area very long, weakly broadened apically toward the part a little before the tip, furnished with 9 to 10 setae of various length
along the mesial margin.
Female: Eighth ventrite (Fig. 4C) bluntly pointed posteromedially; gonocoxites (Fig. 4D)
each with apicolateral tooth long, acutely pointed, apicolateral setae very long. Spermatheca(Fig. 4A) with capsule long, rounded apically; RT-duct thick; spermathecal duct moderately
thick, tightly coiled; basal valve short; basal sclerotized duct long.
Biology and ecology. S. inbecillus is a relatively common species, which is widely distributed in the mountainous regions of central Honshu. The beetles inhabit leaf litter in the naturalforest.

The Steninae of Japan Part 2

Fig. 4. Stenus inbecillus Naomi (A, Hinoemata, Fukushima; B–F, Nomugi, Nagano). A, spermatheca; B, 9th ventrite of male; C, posterior part of 8th ventrite of female; D, posterior part of gonocoxite; E, aedeagus; F, 7th
and 8th ventrites of male. Scale 1: 0.2 mm for B, E, 0.1 mm for A, D; Scale 2: 0.4 mm for C, F.

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Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

Remarks. S. inbecillus is allied to S. davidhulli, but it is separable from the latter species by
the aedeagal median lobe with its 3 apical cusps longer (Fig. 4E), the endophallic expulsion hooksmaller (or atrophied) (Fig. 4E), the copulatory tube with its main tube thinner (Fig. 4E), and thespermathecal duct shorter and thicker (Fig. 4A).
Stenus bishamon Naomi(Figs. 5A–F, 102E)
Stenus bishamon Naomi, 1998a: 390; Herman, 2001: 2092; Naomi & Puthz, 2013: 142.
Type material examined. Holotype: ♂ (CBM), Ichinotani Val., Tsuzuro, Ichiu, Tokushima
Pref., 5. iv. 1968, M. Yoshida leg. Paratype: 1 ♀, same data as holotype.
Other material examined. [SHIKOKU]: 1 ♂1 ♀, Mt. Tonomaru (1310 m), Kuwadaira, Ichiu,
Tokushima Pref., 23. v. 2010, M. Yoshida leg.
Distribution. Japan: Shikoku (Tokushima Pref.).
Redescription. Male and female: Body 3.5–4.2 mm (fore body 1.9–2.1 mm) in length, moderately shining, with antennae moderately long, very thin. Head and abdomen dark brown to
black; pronotum and elytra dark red; labrum dark red; antennae and legs yellowish brown to reddish brown. Head weakly concave, with a pair of longitudinal furrows; punctures round to almost
round, moderately dense, small. Pronotum with surface weakly uneven, with indistinct medianlongitudinal furrow; punctures round to elliptical, very dense, moderately large, a little coarse.
Elytra with surface uneven, weakly depressed near suture; punctures round to almost round, very
dense, various in size but moderately large in average, coarse. Tarsi each with 4th tarsomere
strongly bilobed. Abdomen with punctures round to elliptical, dense, small in anterior segments,
while in posterior segments, punctures very small and sparse, or existing simply as setal sockets.
Lateroventrites missing; tergoventral sutures distinct, thin.
Male: Fourth and 5th ventrites (Fig. 5A) each posteromedially with a bell-shaped, ﬂat area;
6th ventrite (Fig. 5A) posteromedially with a similar ﬂat area, but a little narrower and longer;
7th ventrite (Fig. 5A) posteromedially with an elongate bell-shaped, shallow depression, which is
weakly emarginate; 8th ventrite (Fig. 5A) posteriorly with a small, almost U-shaped emargination; 9th tergum (Fig. 5C) with antecostal apophyses very long; 9th ventrite (Fig. 5D) minutely
serrate posteriorly, with macrosetae long, apicolateral teeth short, acutely pointed, apicolateral
setae moderately long; 10th tergum (Fig. 5C) rounded posteriorly. Aedeagal median lobe (Fig.
5B) broad, angulate apicolaterally, tricuspidate at apicomedian part; apical sclerotized area (Fig.
5B) broad, subtriangular, with median cusp long, acutely pointed, lateral cusps small, acutely
pointed. Endophallic median bands (Fig. 5B) long, very broad; lateral bands (Fig. 5B) long, thin;
expulsion hooks (Fig. 5B) large, each with the anterior plate acutely pointed anteriorly, partiallydivided antero-posteriorly into two parts by a lateral membranous area, demarcated by a suturefrom posterior plate, the posterior plate much smaller than anterior plate; copulatory tube (Fig.
5B) very long, with basal chamber large, ovoidal, main tube thin, almost attenuate. Parameres(Fig. 5B) very long, sinuous in apical 1/3, acutely pointed apically; stem rather thin, mesiallywith several setae just before apical area; apical area distinctly swollen mesially, furnished mesially with 20 to 23 setae.
Female: Eighth ventrite obtusely angulate posteromedially; gonocoxites (Fig. 5F) irregularly
toothed posteriorly, each with apicolateral tooth long, acutely pointed, apicolateral setae very
long. Spermatheca (Fig. 5E) stout, with capsule rounded apically, short; RT-duct thick, short;

The Steninae of Japan Part 2

Fig. 5. Stenus bishamon Naomi (A–D, Ichinotani, Tokushima; E, F, Tonomaru, Tokushima). A, 4th to 8th ventrites of male; B, aedeagus; C, 9th and 10th terga of male; D, 9th ventrite of male; E, spermatheca; F, posterior
part of gonocoxite. Scale 1: 0.2 mm for B–D, 0.1 mm for F; Scale 2: 0.3 mm for A; Scale 3: 0.1 mm for E.

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Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

duct moderately thick to thick, coiled with 4 turns; basal valve moderately long; basal sclerotizedduct long, thick. Basal structure bowl-shaped, membranous but sclerotized only at the distal part.
Biology and ecology. S. bishamon is a rare species; and it is distributed in the high mountainous regions of eastern Shikoku. The beetles inhabit leaf litter in the natural forests.
Remarks. S. bishamon is allied to S. davidhulli and S. inbecillus, but it is separable from thelatter 2 species by the aedeagal median lobe with its apical sclerotized area well-developed andsubtriangular, and its 3 apical cusps located on the apicomedian part (Fig. 5B), the paramere
characteristically bisinuous in apical 1/3 (Fig. 5B), the endophallic copulatory tube much longer(Fig. 5B), and the spermathecal with its basal sclerotized duct thicker (Fig. 5E).
Etymology. The speciﬁc epithet of this species is derived from the name of god “Bishamon”,
which appears in the Japanese ancient mythology.
Stenus carura Naomi(Figs. 6A–F, 102F)
Stenus carura Naomi, 1989: 48; Herman, 2001: 2115; Naomi & Puthz, 2013: 142.
Type material examined. Holotype: ♂ (KUF), Mt. Ishizuchi, Ehime Pref., 16. vi. 1981, S.
Naomi leg.
Other material examined. [SHIKOKU]: 1 ♂, Saijyo City, Ehime Pref., 9. vii. 2011. M. Saito
leg.
Distribution. Japan: Shikoku (Ehime Pref.).
Redescription. Male: Body 3.7–4.5 mm (fore body 1.9–2.1 mm) in length, moderately shining, with antennae moderately long, very thin. Head black; pronotum, elytra and abdomen reddish brown to dark reddish brown; labrum dark red; antennae and legs yellowish brown to reddish brown. Head transverse, weakly concave, with a pair of distinct longitudinal furrows;
punctures round, moderately dense, small, somewhat umbilicate. Pronotum with surface uneven,with indistinct median longitudinal furrow; punctures round, very dense, small to medium-sized,
coarse. Elytra with surface uneven; punctures round, very dense, small to medium-sized, coarse.
Legs with femora thick, tarsi each with 4th tarsomere strongly bilobed. Abdomen with puncturesround to almost round, dense, small, distinct in anterior segments, while punctures in posterior
segments very small, shallow. Lateroventrites and tergoventrite sutures missing.
Sixth ventrite (Fig. 6A) posteromedially with a shallow, semicircular depression, which isvery weakly emarginate; 7th ventrite (Fig. 6A) posteromedially with a bell-shaped, moderately
deep depression, which is weakly ridged laterally and moderately emarginate posteriorly; 8thventrite (Fig. 6B) posteromedially with a semicircular emargination; 9th tergum with antecostal
apophyses very long; 9th ventrite (Fig. 6F) elongate, hardly serrate posteriorly, with macrosetaevery short, apicolateral teeth short, acutely pointed, apicolateral setae moderately long; 10th tergum (Fig. 6D) entire. Aedeagal median lobe (Fig. 6E) elongate, distinctly angulate apicolaterally,
almost tricuspidate at apex; apical sclerotized area (Fig. 6E) transverse, longitudinally striated,with median cusp short, pointed, lateral cusps each existing as simple angulation. Endophallic
median bands (Fig. 6E) moderately long, broad; expulsion hooks (Fig. 6C) large, connate by theposteromesial parts, posteromedially with a round projection, each hook broad-bean-shaped,with anterior plate hollowed mesially, demarcated by an oblique ridge from posterior plate, theposterior plate posteriorly with a small, sclerorized tooth; copulatory tube (Fig. 6E) stout, broad,almost Y-shaped but weakly asymmetrical, with basal chamber small, basal constriction distinct,

The Steninae of Japan Part 2

23

Fig. 6. Stenus carura Naomi (Ishizuchi, Ehime). A, 6th and 7th ventrites of male; B, posterior part of 8th ventriteof male; C, expulsion hooks; D, 9th and 10th terga of male; E, aedeagus; F, 9th ventrite of male. Scale 1:
0.3 mm for A; Scale 2: 0.2 mm for B, D–F, 0.1 mm for C.

main tube becoming broader apically, with a pair of apicolateral processes, the right processbifurcate, left process acutely pointed. Parameres (Fig. 6E) each almost rounded apically; apicalarea moderately long, weakly swollen mesially, furnished basally with a tuft of 8 to 9 long setaeon the ventral margin, and mesially with 6 to 10 setae on the ventral and apical margins.
Female: Unknown.
Biology and ecology. S. carura is a rare species; and it is distributed in the mountainous
regions of the western part of Shikoku. The beetles inhabit leaf litter in the natural forests.
Remarks. S. carura seems to be allied to S. bishamon and S. davidhulli, but it is easily sepa-

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Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

rable from the latter 2 species by the head more strongly transverse (Fig. 102F), the legs with thefemora thicker in male (Fig. 102F), the aedeagal paramere shorter (Fig. 6E), and the copulatory
tube with its main tube Y-shaped (Fig. 6E).
Etymology. The speciﬁc epithet of this species is derived from the name of a god “Carura” inan ancient Japanese mythology.
Stenus trispinosus Naomi & Nomura(Figs. 7A–G, 102G)
Stenus trispinosus Naomi & Nomura, 2015: 188.
Type material examined. Holotype (NMNST): ♂, Mt. Misaka, Kawaguchi Lake, Yamanashi
Pref., 24. x. 1999, S. Nomura leg. Paratype, ♀ (cN), same data as holotype.
Distribution. Japan: Honshu (Yamanashi Pref.).
Redescription. Male and female: Body 3.5–3.7 mm (fore body 1.7–1.8 mm) in length, moderately shining, with antennae relatively short, thin. Head and abdomen black; pronotum and elytra dark red; labrum reddish brown to dark red; antennae and legs yellowish brown to reddish
brown. Head weakly concave, with a pair of shallow longitudinal furrows; punctures round,moderately dense to dense, small, umbilicate. Pronotum with surface slightly uneven, with shallow median longitudinal furrow; punctures round to elliptical, very dense, moderately large,
sometimes two or more punctures partially fused. Elytra with surface weakly uneven, shallowly
concave along suture; punctures round to elliptical, very dense, various in size, coarse, sometimes two or more punctures partially fused. Tarsi each with 4th tarsomere strongly bilobed.
Abdomen with punctures round to almost round, dense to very dense, small to medium-sized inanterior segments, while punctures in posterior segments round to elliptical, sparse to dense orvery dense, very small to small, regular. Lateroventrites and tergoventral sutures missing.
Male: Sixth ventrite posteromedially with a semicircular ﬂat area; 7th ventrite posteromedially with a shallow, elliptical depression, which is very shallowly emarginate; 8th ventrite posteromedially with a medium-sized, arcuate emargination; 9th tergum (Fig. 7A) with antecostal
apophyses relatively short, thin; 9th ventrite (Fig. 7B) very minutely serrate posteriorly, with apicolateral teeth short, acutely pointed, apicolateral setae short; 10th tergum (Fig. 7A) entire.
Aedeagal median lobe (Fig. 7D) moderately broad, obtusely angulate apicolaterally, tricuspidate
at apicomedian part; apical sclerotized area (Fig. 7D) transverse, weakly bisinuate at anterior
margin, with three cusps of same size, each acutely pointed. Endophallic median bands (Fig. 7E)
each broad, narrowed anteriorly; explusion hooks (Fig. 7F) posteromesially connected by membrane, each with anterior plate partially demarcated by a suture from posterior plate, the posterior
plate posterolaterally protruding, rounded apically, covered with ﬁne denticles; copulatory tube
(Fig. 7E) simple, basal chamber with two shafts of different length, main tube simply attenuate.
Parameres (Fig. 7D) each thin, very weakly incurved, acutely pointed at apex; apical area very
short, weakly swollen mesially at base, furnished mesially with 5 to 6 short setae.
Female: Eighth ventrite pointed posteromedially; gonocoxites (Fig. 7G) each with apicomesial tooth small, pointed, apicolateral tooth incurved, pointed. Spermatheca (Fig. 7C) with capsule very small; RT-duct long, relatively thick; duct very long, thin, almost tightly coiled; basal
valve short; basal duct sclerotized, longer than basal valve. Bursa copulatrix (Fig. 7C) large,
cone-shaped.
Biology and ecology. S. trispinosus is a rare species; and it is distributed in the mountainous

The Steninae of Japan Part 2

Fig. 7. Stenus trispinosus Naomi & Nomura (Misaka, Yamanashi). A, 9th and 10th terga of male; B, 9th ventriteof male; C, spermatheca; D, aedeagus; E, endophallus; F, expulsion hooks; G, posterior part of gonocoxite.
Scale 1: 0.2 mm for A–B, D, 0.1 mm for C, E–G.

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Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

regions of Chubu district, Honshu. The beetles inhabit leaf litter in the natural forests.
Remarks. S. trispinosus is allied to S. nyorai, but it is separable from the latter species by theaedeagal median lobe apicomedially tricuspidate by the 3 cusps of same size (Fig. 7D), and theendophallic expulsion hook smaller, with its posterior plate much shorter and rounded posterolaterally (Fig. 7F).
Stenus nyorai Naomi(Figs. 8A–G, 102H)
Stenus nyorai Naomi, 1990: 8; Herman, 2001: 2307; Naomi & Puthz, 2013: 142.
Stenus geisha Puthz, 2001a: 45.
Type material examined. Holotype of S. nyorai: ♂ (KUF), Aokigahara, Mt. Fuji, Yamanashi
Pref., 23. vii. 1984, S. Nomura leg. Paratypes: 1 ♀ (cN), same data as holotype.
Holotype of S. geisha: ♀ (cP), Subaru-line (2050 m), Mt. Fuji, Yamanashi Pref., 1. viii. 1999,
V. Puthz leg.
Other material examined. [HONSHU]: 3 ♂3 ♀, Shirabiso Highland, Ue-mura, Nagano Pref.,16. xi. 1999, S. Nomura leg.; 1 ♂1 ♀, same locality, 28. vi. 1991, T. Ito leg.; 3 ♂, Abe Pass,
Yamanashi Pref., 11. xi. 2007, Y. Hirano leg.; 2 ♂2 ♀, Mt. Yanbushi, Shizuoka City, Shizuoka
Pref., 1. viii. 2001, T. Watanabe leg.; 2 ♂3 ♀, Fujinomiya, Mt. Fuji, Shizuoka Pref., 8. vi. 1996,
S. Nomura leg.; 1 ♂, Mt. Takahachi, Fijinomiya City, Shizuoka Pref., 17. vi. 2010, T. Watanabe
leg.; 2 ♂3 ♀, Mizugazuka, Susono City, Shizuoka Pref., 5. xi. 2000, S. Nomura leg.
Distribution. Japan: Honshu (Chubu district).
Redescription. Male and female: Body 4.0–4.5 mm (fore body 1.8–2.1 mm) in length, moderately shining, with antennae moderately long, very thin. Head black; pronotum, elytra andabdomen reddish brown to dark reddish brown; labrum dark brown; antennae and legs yellowish
brown to reddish brown. Head weakly concave, with a pair of distinct longitudinal furrows;
punctures round, moderately dense to dense, small. Pronotum with surface weakly uneven, withmedian longitudinal furrow high indistinct or almost missing; punctures round to elliptical, very
dense, small to medium-sized, coarse, sometimes two or more punctures partially fused. Elytra
with surface uneven; punctures round to almost round, very dense, moderately large, coarse.
Tarsi each with 4th tarsomere strongly bilobed. Abdomen with punctures round to elliptical,
dense to very dense, small in anterior segments, while punctures in posterior segments round to
elliptical, moderately dense to dense, very small. Lateroventrites and tergoventrite sutures missing.
Male: Sixth ventrite sometimes posteromedially with a semicircular ﬂat area; 7th ventrite(Fig. 8E) posteromedially with a bell-shaped, ﬂat area; 8th ventrite (Fig. 8E) posteromediallywith an arcuate emargination; 9th tergum (Fig. 8A) with antecostal apophyses long; 9th ventrite(Fig. 8B) very minutely, irregularly serrate posteriorly, with macrosetae long, apicolateral teeth
moderately long, acutely pointed, apicolateral setae long; 10th tergum (Fig. 8A) entire. Aedeagal
median lobe (Fig. 8C) broad, gently rounded apicolaterally, pointed at apex; apical sclerotizedarea (Fig. 8C) almost triangular, covered ventrally with longitudinal or oblique striate and with a
median longitudinal suture. Endophallic median bands (Fig. 8C) each moderately long, verybroad at base; latreral bands (Fig. 8C) long; expulsion hooks (Fig. 8G) very large, connected bymembrane at the anteromesial corners of posterior plates, each hook with anterior plate weakly
incurved, demarcated by a suture from posterior plate, the posterior plate elongate, much longer

The Steninae of Japan Part 2

Fig. 8 Stenus nyorai Naomi (A, E, Fujinomiya, Yamanashi; B, Abe, Yamanashi; C, D, F, G, Aokigahara,
Yamanashi). A, 9th and 10th terga of male; B, 9th ventrite of male; C, aedeagus; D, spermatheca; E, 7th and8th ventrites of male; F, posterior part of gonocoxite; G, expulsion hooks. Scale 1: 0.2 mm for A–C, 0.1 mm
for D, F, G; Scale 2: 0.3 mm for E.

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Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

than anterior plate; copulatory tube (Fig. 8C) with main tube simple, straight, weakly constricted
between the basal and apical tubes. Parameres (Fig. 8C) each acutely pointed apically; apicalarea short, weakly swollen at base, furnished mesially with 5 to 6 short setae.
Female: Eighth ventrite pointed posteromedially; gonocoxites (Fig. 8F) toothed posteriorly,
each with apicolateral tooth pointed, apicolateral setae very long. Spermatheca (Fig. 8D) with
capsule very small; RT-duct long, relatively thick; duct very long, thin, almost tightly coiled;basal valve very short; basal sclerotized duct short.
Biology and ecology. S. nyorai is distributed in the low mountainous to mountainous regionsof the central Honshu. The beetles inhabit leaf litter in the natural forests.
Remarks. S. nyorai is allied to S. trispinosus, but it is separable from the latter species by theaedeagal median lobe simply pointed at apex (Fig. 8C), and the endophallic expulsion hooklarger, with its posterior plate much longer and moderately narrowed apically (Fig. 8G).
Etymology. The speciﬁc epithet of this species “Nyorai” is derived from a traditionally recognized title of Buddha in Japan.
Stenus kisomontanus Naomi, Nomura & Puthz sp. nov.
(Figs. 9A–G, 102I)
Type material. Holotype: ♂ (NSMT-I-C-200325 in NMNS), Mt. Kiso-komagatake (alt.
1550 m), Nagano Pref., 21. ix. 1996, T. Kishimoto leg.
Distribution. Japan: Honshu (Nagano Pref.).
Description. Male: Body 4.5 mm (fore body 2.1 mm) in length, somewhat robust, moderately shining, with antennae moderately long, legs robust. Head black; pronotum and elytra reddish chocolate brown; abdomen dark brown; labrum reddish brown; antennae and legs yellowish
brown to reddish brown. Head weakly concave, with a pair of longitudinal furrows; puncturesround, moderately dense, small, umbilicate. Pronotum with surface uneven, with indistinct, shallow median longitudinal furrow; punctures round, very dense, moderately large, somewhat
coarse, two or more punctures sometimes partially fused. Elytra with surface weakly uneven,almost ﬂat near suture; punctures round to elliptical, very dense, moderately large in average,coarse. Legs with femora thick; tarsi each with 4th tarsomere strongly bilobed. Abdomen with
punctures round, dense, small, regular in anterior segments, while punctures in posterior segments moderately dense, very small, regular. Lateroventrites and tergoventrite sutures missing.
Sixth ventrite (Fig. 9B) posteromedially with a small, semicircular ﬂat area; 7th ventrite (Fig.
9B) almost centrally with a round ﬂat area; 8th ventrite (Fig. 9B) posteriorly with a subtriangularemargination; 9th tergum (Fig. 9C) with antecostal apophyses very long; 9th ventrite (Fig. 9A)
irregularly, very minutely serrate posteriorly, apicolateral teeth short, acutely pointed, apicolateral setae moderately long; 10th tergum (Fig. 9C) almost rounded. Aedeagal median lobe (Fig.
9D) elongate, angulate apicolaterally, pointed at apex; apical sclerotized area (Fig. 9D) subtriangular, with surface sculptured with very thin lines. Endophallic median bands (Fig. 9E) broad,with basal bands almost fused each other, each short, folded band very long; lateral bands thin,long; expulsion hooks (Fig. 9G) connected at the anteromesial parts of posterior plates, eachhook with anterior plate acutely pointed, demarcated by a transverse suture from posterior plate,the posterior plates almost parallel in position; copulatory tube (Fig. 9F) with basal chamber
elongate-ovoidal, main tube attenuate but strongly curved at apex. Parameres (Fig. 9D) each
slender, almost straight, very acutely pointed at apex; apical area short, weakly swollen at base,furnished mesially with 7 to 8 setae.

The Steninae of Japan Part 2

29

Fig. 9. Stenus kisomontanus Naomi, Nomura & Puthz (Kiso-komagatake, Nagano). A, 9th ventrite of male; B,
6th to 8th ventrites of male; C, 9th and 10th terga of male; D, aedeagus; E, median bands; F, copulatory tube;
G, expulsion hooks. Scale 1: 0.2 mm for A, C, D, 0.1 mm for E–G; Scale 2: 0.3 mm for B.

Female: Unkonwn.
Biology and ecology. S. kisomontanus was collected once from the mountainous region of
Chubu district, Honshu. The beetle inhabits leaf litter in the natural forest.
Remarks. S. kisomontanus is allied to S. scissilis and S. unicuspidatus, but it is separable

30

Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

from the latter two species by the aedeagal median lobe with its apical sclerotized area subtriangular (Fig. 9D), and the endophallic copulatory tube with its main tube strongly curved at apex
(Fig. 9F).
Etymology. The speciﬁc epithet of this new species is derived from the name of type locality“Kiso” + the Latin adjective “montanus” which means “mountainous”.
Stenus scissilis Naomi, Nomura & Puthz sp. nov.
(Figs. 10A–F, 102J)
Type material. Holotype: ♂ (NSMT-I-C-200326 in NMNS), Kamisaka Pass, Nakatsugawa
City, Gifu Pref., 15. x. 2006, H. Yokozeki leg.
Distribution. Japan: Honshu (Gifu Pref.).
Description. Male: Body 4.3 mm (fore body 2.0 mm) in length, robust, moderately shining,with antennae moderately long, thin, legs moderately thick. Head and abdomen black; pronotumand elytra dark reddish brown; labrum reddish brown; antennae and legs yellowish brown to reddish brown. Head weakly concave, with a pair of longitudinal furrows; punctures round, sparseto moderately dense, small, umbilicate. Pronotum with surface slightly uneven, with median longitudinal depression hardly developed; punctures round to almost round, very dense, moderately
large, somewhat coarse. Elytra with surface weakly uneven, almost ﬂat near suture; puncturesround to almost round, very dense, moderately large, somewhat coarse. Tarsi each with 4th tarsomere strongly bilobed. Abdomen with punctures round to elliptical, dense to very dense, small inanterior segments, while punctures in posterior segments round to elliptical, sparse to dense, verysmall, regular. Lateroventrites and tergoventral sutures missing.
Sixth ventrite (Fig. 10B) posteromedially with a bell-shaped ﬂat area; 7th ventrite (Fig. 10B)
medially with an elongate, very shallow depression; 8th ventrite (Fig. 10B) posteriorly with amedium-sized emargination; 9th tergum (Fig. 10A) with antecostal apophyses long; 9th ventrite(Fig. 10F) irregularly, minutely serrate posteriorly, with apicolateral teeth short, acutely pointed;
10th tergum (Fig. 10A) rounded posteriorly. Aedeagal median lobe (Fig. 10C) broad, parallelsided behind the middle, distinctly angulate apicolaterally, bicuspidate at apex; apical sclerotizedarea (Fig. 10C) transverse, very short. Endophallic median bands (Fig. 10C) very broad; lateralbands (Fig. 10C) thin, long; explusion hooks (Fig. 10D) separated but connected by the C-shapedrod, anterior plate acutely pointed, demarcated by a transverse suture from posterior plate, theposterior plate obliquely truncate posteriorly; copulatory tube (Fig. 10E) with basal chamber
moderately broad, main tube broad at base, distinctly narrowed and weakly curved toward apex.
Parameres (Fig. 10C) each very acutely pointed at apex; apical area moderately long, weakly
swollen mesially at base, furnished mesially with 7 to 8 setae.
Female: Unknown.
Biology and ecology. S. scissilis is collected only once from the mountainous region of thewestern part of Chubu district, Honshu. The beetle inhabits leaf litter in the natural forest.
Remarks. S. scissilis is allied to S. kisomontanus and S. unicuspidatus, but it is clearly separable from the latter two species by the bicuspidate apex of aedeagal median lobe (Fig. 10C).
Etymology. The speciﬁc epithet of this new species is derived from the Latin adjective “scissilis” which means “splitting”; and the apical cusps of aedeagal median lobe split at base.

The Steninae of Japan Part 2

31

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

Stenus unicuspidatus Naomi & Nomura(Figs. 11A–G, 102K)
Stenus unicuspidatus Naomi & Nomura, 2015: 185.
Type material examined. Holotype: ♂ (NMNST), Oohira Pass, Nagiso-cho, Nagano Pref.,32

Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

Fig. 11. Stenus unicuspidatus Naomi & Nomura (Oohira, Nagano). A, 9th and 10th terga of male; B, 6th to 8th
ventrites of male; C, endophallus; D, posterior part of gonocoxite; E, 9th ventrite of male; F, spermatheca; G,aedeagus. Scale 1: 0.2 mm for A, E, G, 0.1 mm for C–F; Scale 2: 0.3 mm for B.

The Steninae of Japan Part 2

33

15. xi. 1999, S. Nomura leg.
Other material examined. [HONSHU]: 1 ♀ (cN), same data as holotype.
Distribution. Japan: Honshu (Nagano Pref.).
Redescription. Male and female: Body 4.5–4.6 mm (fore body 2.0–2.1 mm) in length, moderately shining, with antennae moderately long, thin. Head black; pronotum and elytra reddish
brown; abdomen dark reddish brown; labrum, antennae and legs yellowish brown to reddish
brown. Head weakly concave, with a pair of longitudinal furrows; punctures round, moderately
dense to dense, small. Pronotum with surface slightly uneven, with indistinct median longitudinal depression; punctures round to elliptical, very dense, small, coarse. Elytra with surface
weakly uneven, almost ﬂat near suture; punctures round to elliptical, very dense, moderately
large, somewhat coarse. Legs with femora relatively thick; tarsi each with 4th tarsomere strongly
bilobed. Abdomen with punctures round to elliptical, moderately dense, small in anterior segments, while punctures in posterior segments sparse, very small, regular. Lateroventrites and tergoventral sutures missing.
Male: Sixth ventrite (Fig. 11B) posteromedially with a bell-shaped ﬂat area; 7th ventrite (Fig.
11B) posteromedially with a shallow, bell-shaped depression, which is smaller than that on 6th
ventrite; 8th ventrite (Fig. 11B) posteriorly with a large emargination; 9th tergum (Fig. 11A) with
antecostal apophyses very long; 9th ventrite (Fig. 11E) minutely serrate posteriorly, with macrosetae short, apicolateral teeth moderately long, acutely pointed, apicolateral setae long; 10th tergum (Fig. 11A) rounded posteriorly. Aedeagal median lobe (Fig. 11G) broad, parallel-sided
behind the middle, angulate to form the almost right-angle at apicolateral corners; apical sclerotized area (Fig. 11G) with the very long median cusp. Endophallic median bands (Fig. 11C) verybroad; lateral bands (Fig. 11C) thin; explusion hooks (Fig. 11C) each with anterior plate acutely
pointed, completely fused with posterior plate, the posterior plates diverging posterolaterally,
obliquely truncate posteriorly; copulatory tube (Fig. 11C) with basal chamber large, main tube
simply attenuate and weakly curved toward apex. Parameres (Fig. 11G) each weakly incurved,
acutely pointed at the apicalmost part; apical area short, weakly swollen mesially at base, furnished mesially with 7 to 9 setae.
Female: Eighth ventrite pointed posteromedially; gonocoxites (Fig. 11D) toothed posteriorly,
each with apicolateral tooth large, acutely pointed, apicolateral setae very long. Spermatheca(Fig. 11F) with capsule longer than broad, rounded at apex; RT-duct moderately long, broad; duct
moderately broad to broad, long, almost tightly coiled; basal valve short; basal sclerotized duct
about 3 times as long as the basal valve. Basal structure conical, membranous.
Biology and ecology. S. unicuspidatus is collected only once from the mountainous region of
Chubu district, Honshu. The beetle inhabits leaf litter in the natural forest.
Remarks. S. unicuspidatus is allied to S. kisomontanus and S. scissilis, but it is separablefrom the latter two species by the aedeagal median lobe with its median cusp very long (Fig.
11G) and the endophallic expulsion hook with its posterior plate turning posterolaterally (Fig.
11C).
Stenus kasumi Naomi(Figs. 12A–H, 102L)
Stenus kasumi Naomi, 1987: 6; Herman, 2001: 2244; Naomi & Puthz, 2013: 142.
Stenus basara Naomi, 1988a: 76 (partim).

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Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

Fig. 12. Stenus kasumi Naomi (A, C, H, Konsei, Gunma; B, D, G, Yumoto, Tochigi; E, Marunuma, Gunma; F,Kuriyama, Tochigi). A, 9th and 10th terga of male; B, spermatheca; C, 9th ventrite of male; D, aedeagus; E,
copulatory tube; F, expulsion hooks; G, posterior part of gonocoxite; H, 6th to 8th ventrites of male. Scale 1:
0.2 mm for A, C, 0.1 mm for E, F; Scale 2: 0.1 mm for B; Scale 3: 0.2 mm for D; Scale 4: 0.3 mm for H;
Scale 5: 0.1 mm for G.

The Steninae of Japan Part 2

35

Type material. Holotype: ♂ (KUF), Mt. Maeshirane, Nikko, Tochigi Pref., 2. vii. 1982. S.
Naomi leg.
Type material examined. Paratype of S. basara Naomi: 1 ♂ (cN), Konsei Pass, Oku-Nikko,
Tochigi Pref., 30. vi. 1982, S. Naomi leg.
Other material examined. [HONSHU]: 1 ♂, Miike, Oze Moor, Hinoemata Vil., Fukushima
Pref., 23. vi. 1990, T. Kishimoto leg.; 1 ♀, Mt. Shibitsu, Oze Moor, Gunma Pref., 8. ix. 1996, S.
Nomura leg.; 1 ♂1 ♀, Konsei Pass, Oku-Nikko, Gunma Pref., 13. viii. 1980, Y. Shibata leg.; 1 ♂,Hanasaki, Katashina Vil., Gunma Pref., 26. v. 1990, T. Shimizu leg.; 6 ♂1 ♀, Marunuma Highland, Gunma Pref., 29. iv. 1991, T. Ito leg.; 3 ♂2 ♀, Nikkozawa-Kinunuma, Kuriyama Vil.,
Tochigi Pref., 3. ix. 1991, S. Naomi leg.; 1 ♀, Yumoto, Oku-Nikko, Tochigi Pref., 10. vii. 1994,
S. Naomi leg.
Distribution. Japan: Honshu (Tohoku and Chubu districts).
Redescription. Male and female: Body 4.3–4.8 mm (fore body 1.8–2.3 mm) in length,
weakly shining, with antennae moderately long, very thin. Head black; pronotum, elytra andabdomen dark brown; labrum dark brown; antennae and legs reddish brown. Head weakly concave, with a pair of longitudinal furrows; punctures round, moderately dense, small, umbilicate.
Pronotum with surface uneven, with indistinct median longitudinal furrow; punctures very dense,coarse, rugose. Elytra with surface uneven, shallowly depressed or almost ﬂat near suture; punctures round to elliptical, very dense, various in size, coarse, rugose. Tarsi each with 4th tarsomere
strongly bilobed. Abdomen with punctures round, moderately dense, small in anterior segments,
while punctures in posterior segments very ﬁne, shallow. Lateroventrites obsoletely retaining
only in outline but tergoventrite sutures are completely missing.
Male: Sixth ventrite (Fig. 12H) posteromedially with a subtrapezoidal ﬂat area; 7th ventrite(Fig. 12H) posteromedially with a nearly bell-shaped ﬂat area, which is very weakly emarginate;
8th ventrite (Fig. 12H) posteromedially with a small semicircular emargination; 9th tergum (Fig.
12A) with antecostal apophyses very long; 9th ventrite (Fig. 12C) serrate posteriorly, with macrosetae relatively short, apicolateral teeth moderately long, pointed, apicolateral setae long; 10th
tergum (Fig. 12A) rounded posteriorly. Aedeagal median lobe (Fig. 12D) moderately broad, distinctly angulate apicolaterally; apical sclerotized area (Fig. 12D) hardly developed, with mediancusp very long, thin, lateral cusps weakly developed, blunt. Endophallic median bands (Fig.
12D) long, very broad; lateral bands (Fig. 12D) very long, thin; expulsion hooks (Fig. 12F) connected by a narrow membrane at the posteromesial parts, anterior plate laterally with a hookturning ventrally, partially demarcated by an oblique line from posterior plate, the posterior plate
broad, more or less angulate posterolaterally; copulatory tube (Fig. 12E) with basal chamber
ovoidal, main tube elongate-rhombic with apical processes not or hardly divided right and left.
Parameres (Fig. 12D) thin, each weakly incurved before apical area, then weakly turning laterally at the apical area, very acutely pointed at apex; apical area moderately long, distinctly swollen mesially at base, furnished mesially with a tuft of 5 to 6 setae at base and with 2 or moresetae near the middle.
Female: Eighth ventrite bluntly pointed posteromedially; gonocoxites (Fig. 12G) each withapicolateral tooth long, acutely pointed, apicolateral setae very long. Spermatheca (Fig. 12B)
with capsule hardly developed; RT-duct long, moderately thick; duct very long, relatively thin tomoderately thick, almost tightly coiled; basal sclerotized duct long; spermathecal gland small,
spherical.
Biology and ecology. S. kasumi is distributed in the high mountainous regions of central
Honshu. The beetles inhabit leaf litter in the natural forests.

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Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

Remarks. S. kasumi is allied to S. yatsugatakensis, but it is separable from the latter species
by the endophallic expulsion hook with its posterior plate distinctly broader (Fig. 12F), the copulatory tube its main tube subrhombic, without the lateral processes (Fig. 12E) and the spermatheca with its duct thinner and longer (Fig. 12B).
Etymology. The speciﬁc epithet of this species is derived from the Japanese noun “kasumi”,
which means “spring haze”.
Stenus yatsugatakensis Naomi(Figs. 13A–G, 103A)
Stenus yatsugatakensis Naomi, 2015: 14.
Type material examined. Holotype: ♂ (OMNH), Shirakoma, Kitayatsu, Mt. Yatsugatake,
Nagano Pref., 13–16. ix. 1996, T. Ito leg. Paratypes: 1 ♂1 ♀, same data as holotype.
Other material examined. [HONSHU]: 1 ♂1 ♀, Ameike, Yachiho Vil., Nagano Pref., 19. viii.
1996, S. Nomura leg.
Distribution. Japan: Honshu (Nagano Pref.).
Redescription. Male and female: Body 4.1-4.2 mm (fore body 2.0-2.1 mm) in length, dull to
weakly shining, antennae moderately long, thin. Head and abdomen dark brown to black; prothorax and elytra dark reddish brown; labrum dark brown; antennae and legs yellowish brown toreddish brown. Head weakly concave, with a pair of longitudinal furrows; punctures round, moderately dense to dense, small, irregular. Pronotum with surface uneven, with indistinct medianlongitudinal furrow; punctures round to elliptical, very dense, coarse, rugose. Elytra with surface
uneven, almost ﬂat near suture; punctures round to elliptical, very dense, moderately large,coarse. Tarsi each with 4th tarsomere strongly bilobed. Abdomen with punctures round to elliptical, dense, small in anterior segments, while punctures in 7th and 8th segments very small,sparse. Lateroventrites and tergoventrite sutures missing.
Male: Seventh ventrite (Fig. 13D) posteromedially with a bell-shaped ﬂat area, which is shallowly emarginate; 8th ventrite (Fig. 13D) posteromedially with a subtriangular emargination; 9th
tergum (Fig. 13B) with antecostal apophyses moderately long; 9th ventrite (Fig. 13F) minutely
serrate posteriorly, with macrosetae short, apicolateral teeth acutely pointed, apicolateral setae
short; 10th tergum (Fig. 13B) rounded posteriorly. Aedeagal median lobe (Fig. 13C) broad, distinctly angulate apicolaterally; apical sclerotized area (Fig. 13C) transverse, with median cusp
very long, thin, lateral cusps broad, blunt. Endophallic median bands (Fig. 13C) each with basal
band moderately long, broad, folded band short; explusion hooks (Fig. 13G) connected by a submembrane at the posteromesial parts of posterior plates, anterior plate broad, demarcated by atransverse suture from posterior plate, the posterior plate narrowed medially, swollen posterolaterally; copulatory tube (Fig. 13E) robust, with basal chamber comprising two sclerotized rods,
not swollen laterally, main tube broad, subrhombic, with apical processes each long, thick, lateralprocesses each incurved, attenuate. Parameres (Fig. 13C) each thin, acutely pointed at apex; apical area short, hardly or weakly swollen at base, furnished mesially with 7 to 9 setae of various
length.
Female: Eighth ventrite bluntly pointed posteromedially; gonocoxites each serrate posteriorly, with apicolateral tooth short, pointed, apicolateral setae long. Spermatheca (Fig. 13A)
robust, with capsule rounded apically; RT-duct thick; spermathecal duct long, moderately thick tothick, moderately coiled; basal valve moderately long; basal sclerotized duct long; basal pouch

The Steninae of Japan Part 2

Fig. 13. Stenus yatsugatakensis Naomi (Shirakoma, Nagano). A, spermatheca; B, 9th and 10th terga of male; C,aedeagus; D, 7th and 8th ventrites of male; E, endophallic copulatory tube; F, 9th ventrite of male; G, endophallic expulsion hooks. Scale 1: 0.1 mm for A, E, G, 0.2 mm for B, C, F; Scale 2: 0.3 mm for D.

37

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Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

conical, sclerotized. Bursa copulatrix (Fig. 13A) funnel-shaped, with anterior (narrower) areasclerotized, posterior (broader) area membranous.
Biology and ecology. S. yatsugatakensis is distributed in the high mountainous regions ofcentral Chubu, Honshu. The beetles inhabit leaf litter in the natural forests.
Remarks. S. yatsugatakensis is allied to S. kasumi, but it is separable from the latter species
by the endophallic expulsion hook with its posterior plate distinctly narrower (Fig. 13G), thecopulatory tube with its main tube rhombic and having the lateral processes (Fig. 13E), and thespermatheca with its duct thicker and shorter (Fig. 13A).
Stenus sawadaiellus Naomi & Puthz(Figs. 14A–F, 103B)
Stenus sawadaiellus Naomi & Puthz, 1994: 299; Herman, 2001: 2379; Naomi & Puthz, 2013:142.
Type material examined. Holotype: 1 ♂ (cP), Mt. Ontake, Ohtaki Vil., Nagano Pref., 6. x.
1972, K. Sawada leg.
Other material examined. [HONSHU]: 1 ♂ (cN), Mt. Ontake, Ohtaki Vil., Nagano Pref., 4.
viii. 1997, S. Nomura leg.
Distribution. Japan: Honshu (Nagano Pref.).
Redescription. Male: Body 3.2–4.2 mm (fore body 1.9–2.0 mm) in length, weakly shining,with antennae long, thin. Body dark chocolate brown to black; labrum dark red; antennae and legs
reddish brown. Head weakly concave, with a pair of distinct longitudinal furrows; puncturesround, moderately dense, small, irregular, somewhat umbilicate. Pronotum with surface uneven,with indistinct median longitudinal furrow; punctures very dense, rugose. Elytra (Fig. 14D) withsurface uneven, almost ﬂat near suture; punctures round to elliptical, very dense, various in size
but moderately large on average, subrugose, coarse. Tarsi each with 4th tarsomere bilobed. Abdomen with punctures round, dense, small, regular in anterior segments, while punctures in posterior
segments very small, shallow, regular. Lateroventrites and tergoventrite sutures missing.
Seventh ventrite (Fig. 14E) posteromedially with a nearly bell-shaped, ﬂat or very shallow
depression, which is very shallowly emarginate; 8th ventrite (Fig. 14E) posteromedially with asemicircular emargination; 9th tergum (Fig. 14B) with antecostal apophyses long; 9th ventrite
with apicolateral teeth acutely pointed; 10th tergum (Fig. 14B) rounded posteriorly. Aedeagal
median lobe (Fig. 14C) broad, distinctly angulate apicolaterally; apical sclerotized area (Fig.
14C) transverse, with median cusp short, pointed, lateral cusps broad, angulate. Endophallic
median bands (Fig. 14A) moderately long, broad; lateral bands (Fig. 14A) long, thin; expulsion
hooks (Fig. 14A, F) separated but connected each other by a submembranous plate at the mesial
sides of posterior plates, each hook with anterior plate having a lateral sclerotized ﬂap, demarcated by a transverse suture from posterior plate, the posterior plate weakly hooked ventrally
along posterior margin; copulatory tube (Fig. 14A) elongate, with basal chamber hardly swollen
laterally, main tube thick, baculiform, subrhombic at apical part, with apical processes moderately long, acutely pointed, lateral processes very short, membranous plate dotted, arcuately
emarginate laterally. Parameres (Fig. 14C) each constricted before the apical area, very acutely
pointed at apex; apical area moderately long, swollen mesially, furnished mesially with 7 to 8
short and 1 or 2 long setae, but glabrous on the apicalmost 1/3.
Female: Unknown.

The Steninae of Japan Part 2

Fig. 14. Stenus sawadaiellus Naomi (Ontake, Nagano). A, apical part of median lobe with outthrusted endophallus;
B, 9th and 10th terga of male (antecostal apophyses not illustrated); C, aedeagus; D, left elytron; E, 7th and 8th
ventrites of male; F, expulsion hooks. 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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Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

Biology and ecology. S. sawadaiellus is distributed in the mountainous region of central
Honshu. The beetles inhabit leaf litter in the natural forests.
Remarks. S. sawadaiellus is allied to S. uncinatus and S. inaequatus, but it is separable fromthe latter two species by the aedeagal median lobe with its median cusp shorter (Fig. 14C), andthe endophallic copulatory tube with its main tube more slender and its subrhombic apical tube
smaller (Fig. 14A). Furthermore, S. sawadaiellus is separable also from S. uncinatus by theaedeagal median lobe broader at the apicolateral corners (Fig. 14C), and from S. inaequatus by
the aedeagal median lobe with its apical sclerotized area less strongly developed (much shorter)(Fig. 14C).
Etymology. This species is named in honor of Dr. Kohei Sawada (Takatsuki, Osaka), who
studies the Aleocharinae (Staphylinidae) based on the chaetotaxal morphology.
Stenus uncinatus Naomi, Nomura & Puthz sp. nov.
(Figs. 15A–G, 103C)
Type material. Holotype: ♂ (NSMT-I-C-200327 in NMNST), Shinhotaka Spa, Kamitakara
Vil., Gifu Pref., 1. x. 2000. T. Watanabe leg. Paratypes: 2 ♂1 ♀ (cN), same data as holotype; 1 ♀
(cN), Tokugo Pass, Nagano Pref., 22. vii. 1967, T. Hozumi leg.
Distribution. Japan: Honshu (Gifu and Nagano Prefs.).
Description. Male and female: Body 3.6–4.2 mm (fore body 2.0–2.3 mm) in length, weakly
shining, with antennae moderately long, very thin. Head black; pronotum and elytra dark brown;
abdomen dark brown to black; labrum dark red; antennae and legs reddish brown. Head weakly
concave, with a pair of distinct longitudinal furrows; punctures round, moderately dense, small,irregular, somewhat umbilicate. Pronotum with surface uneven, with indistinct median longitudinal furrow; punctures very dense, rugose. Elytra with surface uneven, almost ﬂat near suture;punctures round to elliptical, very dense, various in size, subrugose, coarse. Tarsi each with 4thtarsomere bilobed. Abdomen with punctures round, moderately dense to dense, small in anterior
segments, while punctures in posterior segments very ﬁne, shallow. Lateroventrites and tergoventrite sutures missing.
Male: Seventh ventrite (Fig. 15E) posteromedially with a bell-shaped, very shallow depression, which is very shallowly emarginate; 8th ventrite (Fig. 15E) posteromedially with a nearly
semicircular emargination; 9th tergum (Fig. 15C) with antecostal apophyses long; 9th ventrite(Fig. 15B) minutely, sparsely serrate posteriorly, with macrosetae moderately long, apicolateral
teeth acutely pointed, apicolateral setae long; 10th tergum (Fig. 15C) entire. Aedeagal median
lobe (Fig. 15A) moderately broad, gently rounded apicolaterally; apical sclerotized area (Fig.
15A) nearly arched, with median cusp moderately long, lateral cusps short, angulate. Endophallic
median bands (Fig. 15A) moderately long, broad; lateral bands very thin (Fig. 15A); expulsion
hooks (Fig. 15F) separated, with anterior plate demarcated by a transverse suture from posterior
plate, the posterior plate weakly hooked ventrally along posterior margin; copulatory tube (Fig.
15A) stout, basal chamber hardly swollen laterally, main tube almost baculiform basally, funnelshaped at apex, with apical processes each moderately long, pointed, lateral processes each short,pointed. Parameres (Fig. 15A) each almost straight, acutely pointed at apex; apical area long,
weakly swollen mesially at base, furnished mesially with 9 to 11 setae.
Female: Eighth ventrite bluntly pointed posteromedially; gonocoxites (Fig. 15G) toothed
posteriorly, each with apicolateral tooth long, acutely pointed, apicolateral setae very long. Sper-

The Steninae of Japan Part 2

Fig. 15. Stenus uncinatus Naomi, Nomura & Puthz sp. nov. (Shinhotaka, Gifu). A, aedeagus; B, 9th ventrite ofmale; C, 9th and 10th terga of male; D, spermatheca; E, 7th and 8th ventrites of male; F, expulsion hooks; G,posterior part of gonocoxite. Scale 1: 0.2 mm for A–C, 0.1 mm for D, F, G; Scale 2: 0.3 mm for E.

41

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Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

matheca (Fig. 15D) with capsule rounded apically; RT-duct moderately long, thick; duct very
long, thin, tightly coiled; basal sclerotized duct long; basal pouch funnel-shaped, weakly sclerotized in distal part, submembranous in proximal part.
Biology and ecology. S. uncinatus is distributed in the mountainous regions of central Honshu. The beetles inhabit leaf litter in the natural forests; and they were collected under moss in
Shinhotaka, Gifu.
Remarks. S. uncinatus is allied to S. inaequatus, but it is separable from the latter species by
the aedeagal median lobe simply rounded apicolaterally, with its apical sclerotized area narrower(Fig. 15A), the endophallic expulsion hook with its anterior plate a little longer than posterior
plate (Fig. 15F), and the copulatory tube with its subrhombic apical part shorter (Fig. 15A).
Etymology. The speciﬁc epithet of this new species is derived from the Latin adjective “uncinatus” which means “hooked”; and the posterior margin of the posterior plate of endophallic copulatory tube is hooked ventrally.
Stenus inaequatus Puthz(Fig. 16A–F)
Stenus inaequatus Puthz, 1993a: 150; Herman, 2001: 2227; Naomi & Puthz, 2013: 142.
Type material examined. Holotype: ♂ (MHNG), Mt. Kurofu (2100 m), Gunma Pref., 19. vii.
1980, I. Löbl leg. Paratype: 1 ♂ (cP), Mt. Shirane (1750 m), Gunma Pref., 22. vii. 1980, I. Löbl
leg.
Distribution. Japan: Honshu (Gunma Pref.).
Redescription. Male and female: Body 3.6–4.2 mm (fore body 2.0–2.1 mm) in length, moderately shining, with antennae moderately long, thin. Head and abdomen dark brown to black;pronotum and elytra reddish brown to dark brown; labrum dark brown; antennae and legs yellowish brown to reddish brown. Head weakly concave, with a pair of longitudinal furrows; punctures round to almost round, dense to very dense, somewhat umbilicate, sometimes two punctured partially fused. Pronotum with surface uneven, with indistinct median longitudinal furrow;
punctures very dense, strongly rugose. Elytra with surface strongly uneven, weakly concave nearsuture; punctures round to elliptical, very dense, subrugose, coarse. Tarsi each with 4th tarsomere
bilobed. Abdomen with punctures round, dense, small in anterior segments, while punctures in
7th and 8th segments very small, sparse to moderately dense, irregular. Lateroventrites and tergoventrite sutures missing.
Male: Sixth ventrite (Fig. 16E) posteromedially with a semicircular, ﬂat area; 7th ventrite(Fig. 16E) posteromedially with a bell-shaped, shallow depression, which is very shallowly
emarginate posteriorly, and narrower than the ﬂat area in the 6th; 8th ventrite (Fig. 16E) posteromedially with a relatively small emargination; 9th tergum (Fig. 16C) with antecostal apophyses
moderately long; 9th ventrite (Fig. 16D) minutely serrate posteriorly, with macrosetae short, apicolateral teeth broad at base, acutely pointed, apicolateral setae moderately long; 10th tergum(Fig. 16C) rounded posteriorly. Aedeagal median lobe (Fig. 16A) broad, weakly angulate or
rounded apicolaterally, with apicolateral parts weakly expanding laterally; apical sclerotized area
(Fig. 16A) well-developed, with median cusp long, thin, lateral cusps broad, angulate. Endophallic median bands moderately long, broad; lateral bands moderately broad; expulsion hooks (Fig.
16F) separated but connected by a transverse rod, each hook broad, with anterior plate partiallydemarcated by a suture from posterior plate, the posterior plate weakly, arcuately emarginate at

The Steninae of Japan Part 2

Fig. 16. Stenus inaequatus Puthz (Shirane, Gunma). A, aedeagus; B, copulatory tube; C, 9th and 10th terga of
male; D, 9th ventrite of male; E, 6th to 8th ventrites of male; F, expulsion hooks. Scale 1: 0.2 mm for A, C, D,
0.1 mm for B, F; Scale 2: 0.3 mm for E.

43

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Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

lateral side, almost rounded posteriorly; copulatory tube (Fig. 16B) stout, main tube baculiform
basally, subrhombic apically, with apical processes each long, pointed, lateral processes each
short, incurved, pointed. Parameres (Fig. 16A) each almost straight, very acutely pointed at apex;
apical area moderately long, hardly swollen mesially at base, furnished mesially with 8 to 9
setae.
Female: Unknown.
Biology and ecology. S. inaequatus is distributed in the mountainous regions of the northernpart of Kanto district, Honshu. The beetles inhabit leaf litter in the natural forests.
Remarks. S. inaequatus is allied to S. uncinatus, but it is separable from the latter species by
the aedeagal median lobe angulate and weakly expanding laterally at the apicolateral corners,
with its apical sclerotized area broader (Fig. 16A), the endophallic expulsion hook with its anterior plate shorter than posterior plate (Fig. 16F), and the copulatory tube with its subrhombic apical part longer (Fig. 16B).
Stenus houou Naomi(Figs. 17A–H, 103D)
Stenus houou Naomi, 2010: 35; Naomi & Puthz, 2013: 142.
Type material examined. Holotype: ♂ (CBM), Houou Lodge, Mt. Houou, Nirasaki City,
Yamanashi Pref., 13. xi. 1991, K. Hosoda leg. Paratypes: 5 ♂1 ♀, same data as holotype; 1 ♂,same locality, 1. x. 1992, K. Hosoda leg.; 1 ♂, same locality, 8. vi. 1991, K. Hosoda leg.; 1 ♂, 1.
vii. 1989, K. Hosoda leg.; 1 ♀, same locality, 17. vii. 1992, K. Hosoda leg.; 1 ♀, same locality, 8.
viii. 1992, K. Hosoda leg.; 1 ♀, same locality, 21. x. 1988, K. Hosoda leg.; 1 ♀, same locality,
22. vii. 1992, K. Hosoda leg.; 2 ♀, same locality, 3. vi. 1990, K. Hosoda leg.; 1 ♂, Maruno-cho,
Yamanashi Pref., 25. xii. 1992, K. Hosoda leg.
Other material examined. [HONSHU]: 1 ♂, Houou Lodge, Mt. Houou, Nirasaki City,
Yamanashi Pref., 18. vii. 2016, M. Saito leg.
Distribution. Japan: Honshu (Yamanashi Pref.).
Redescription. Male and female: Body 3.7–4.0 mm (fore body 1.7–2.1 mm) in length,
weakly to moderately shining, antennae moderately long, thin. Head and abdomen black; pronotum and elytra dark chocolate brown; labrum dark brown; antennae and legs reddish brown tobrown. Head weakly concave, with a pair of longitudinal furrows; punctures round, moderately
dense to dense, small, irregular, somewhat umbilicate. Pronotum with surface uneven with indistinct median longitudinal furrow; punctures round to elliptical, very dense, rugose, coarse. Elytra
with surface uneven, weakly depressed near suture; punctures round to almost round, very dense,
moderately large, coarse. Tarsi each with 4th tarsomere strongly bilobed. Abdomen with punctures round, moderately dense to dense, small in anterior segments, while punctures in posterior
segments very ﬁne, sparse. Lateroventrites and tergoventrite sutures missing.
Male: Seventh ventrite posteromedially with a bell-shaped ﬂat area, which is very shallowly
emarginate; 8th ventrite (Fig. 17H) posteromedially with a subtriangular emargination; 9th tergum (Fig. 17C) with antecostal apophyses long; 9th ventrite (Fig. 17D) serrate posteriorly, withmacrosetae moderately long, apicolateral teeth moderately long, acutely pointed, apicolateral
setae moderately long; 10th tergum (Fig. 17C) rounded posteriorly. Aedeagal median lobe (Fig.
17E) broad, distinctly angulate apicolaterally; apical sclerotized area (Fig. 17E) weakly developed, arcuately emarginate at anteromedial part, with median cusp long, moderately thick, lateral

The Steninae of Japan Part 2

Fig. 17. Stenus houou Naomi (Houou, Yamanashi). A, spermatheca; B, copulatory tube; C, 9th and 10th terga of
male; D, 9th ventrite of male; E, aedeagus; F, expulsion hooks; G, posterior part of gonocoxite; H, posterior
part of 8th ventrite of male. Scale 1: 0.1 mm for A, G; Scale 2: 0.1 mm for B, F, 0.2 mm for C, D; Scale 3:
0.2 mm for E; Scale 4: 0.25 mm for H.

45

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Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

cusps angulate. Endophallic median bands (Fig. 17E) each moderately long, very broad at base;
expulsion hooks (Fig. 17F) connected by a membrane at the mesial margins of posterior plates,
each hook with anterior plate acutely pointed, widely membranous mesially, demarcated by asuture from posterior plate, the posterior plate smaller than anterior plate, more or less rounded
posteriorly; copulatory tube (Fig. 17B) robust, basal chamber large, elongate-ovoidal, main tube
subrhombic with apical processes each long, thin, lateral processes each acutely pointed. Parameres (Fig. 17E) thin; apical area long, weakly swollen mesially at base, furnished mesially with
11 to 12 setae.
Female: Eighth ventrite obtusely angulate posteromedially; gonocoxites (Fig. 17G) toothed
posteriorly, each with apicolateral tooth long, acutely pointed, apicolateral setae very long. Spermatheca (Fig. 17A) with capsule rounded apically very small; RT-duct long, thick; duct very
long, usually thin but thick at the distal part, almost tightly coiled; basal valve moderately long;
basal sclerotized duct long; basal pouch conical, sclerotized.
Biology and ecology. S. houou is distributed in the high mountainous regions of Southern
Alps and its neighboring areas, central Honshu. The beetles inhabit leaf litter in the natural forests.
Remarks. S. houou is allied to S. yasuhikoiellus, but it is separable from the latter species by
the aedeagus with its lateral cusps developed and distinctly angulate (Fig. 15E) and the endophallic copulatory tube with its apical processes narrowly separated ventrally and its lateral processes pointed (Fig. 17B).
Etymology. The speciﬁc epithet of this species is derived from the name of type locality“Houou”, which is however virtually the name of imaginary bird in the ancient mythology.
Stenus yasuhikoiellus Naomi(Fig. 18A–F)
Stenus yasuhikoiellus Naomi, 2010: 36; Naomi & Puthz, 2013: 142.
Type material examined. Holotype: ♂ (CBM), Kiso-komagadake, Nagano Pref., 24. viii.
1962, Y. Hayashi leg.
Distribution. Japan: Honshu (Nagano Pref.).
Redescription. Male: Body 4.0 mm (fore body 1.8 mm) in length, weakly to moderately shining. Head dark brown; pronotum, elytra and abdomen reddish brown to dark brown; antennae
and legs yellowish brown to reddish brown. Head weakly concave, with a pair of longitudinalfurrows; punctures round, somewhat irregular, distinct. Pronotum with surface uneven withindistinct median longitudinal furrow; punctures round to elliptical, very dense, various in size,
rugose, coarse. Elytra with surface almost even, almost ﬂat near suture; punctures round, very
dense, large, almost regular. Tarsi each with 4th tarsomere strongly bilobed. Abdomen with punctures round, various in size but small on average in anterior segments, while punctures in posterior segments round, very small, almost regular. Lateroventrites and tergoventrite sutures missing.
Seventh ventrite posteromedially with an almost ﬂat area, which is very shallowly emarginate; 8th ventrite (Fig. 18D) posteromedially with a shallow, arcuate emargination; 9th tergum(Fig. 18A) with antecostal apophysis long; 9th ventrite (Fig. 18B) minutely serrate posteriorly,
with macrosetae moderately long, apicolateral teeth short, acutely pointed, apicolateral setae
moderately long; 10th tergum (Fig. 18A) bluntly angulate posteromedially. Aedeagal median

The Steninae of Japan Part 2

Fig. 18. Stenus yasuhikoiellus Naomi (Kisokomagadake, Nagano). A, 9th and 10th terga of male; B, 9th ventriteof male; C, aedeagus; D, 8th ventrite of male; E, copulatory tube; F, expulsion hooks. Scale 1: 0.2 mm for A toC, 0.1 mm for E, F; Scale 3: 0.25 mm for D.

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Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

lobe (Fig. 18C) broad, angulate apicolaterally; apical sclerotized area (Fig. 18C) weakly developed, arcuately emarginate at anteromedial part, with median cusp short, thin, lateral cusps eachexisting as a low, broad angulation. Endophallic median bands (Fig. 18C) long, very broad;
expulsion hooks (Fig. 18F) connected by a membrane at the mesial margins of posterior plates,
each with anterior plate acutely pointed, widely membranous mesially, posterior plate rounded
posterolaterally; copulatory tube (Fig. 18E) very large, nearly spatulate, with basal chamber elongate-ovoidal, main tube subrhombic, apicodorsally with the large, subspherical membranous plat,ventrally with apical processes fused ventrally, each acutely pointed. Parameres (Fig. 18C)
diverging posterolaterally in apical parts, each very acutely pointed at apex; apical area moderately long, swollen mesially at base, furnished mesially with 12 to 13 short setae.
Female: Unknown.
Biology and ecology. S. yasuhikoiellus is a rare species; and it is only once collected from thehigh mountainous region of Chubu district, Honshu. The beetle inhabits leaf litter in the naturalforests.
Remarks. S. yasuhikoiellus is allied to S. houou, but it is separable from the latter species by
the aedeagal median lobe with its lateral cusp existing as a low, broad angulation (Fig. 18C) andthe endophallic copulatory tube with its apical processes fused ventrally and its lateral processes
missing (Fig. 18E).
Etymology. This species is named in honor of Mr. Yasuhiko Hayashi (Kawanishi, Hyogo).
Stenus kumoma Naomi(Figs. 19A–H, 103E)
Stenus kumoma Naomi, 1987: 7; Herman, 2001: 2250; Naomi & Puthz, 2013: 142.
Type material. Holotype: 1 ♂ (KUF), Kawarabo, Mt. Hayachine, Hanamaki City, Iwate Pref.,22–24. vi. 1980, S. Naomi leg.
Type material examimed. Paratype: 1 ♂ (cN), same data as holotype.
Other material examined. [HONSHU]: 2 ♂1 ♀, Mt. Hayachine, Iwate Pref., 17. vii. 1985, S.
Nomura leg.; 1 ♂, Odagoe, Mt. Hayachine, Hanamaki City, Iwate Pref., 12. vi. 2014, H.
Yokozeki leg.; 1 ♂2 ♀, Mt. Hayachine, Iwate Pref., 16. v. 2000, Y. Hagino & T. Fujikawa leg.
Distribution. Japan: Honshu (Iwate Pref.).
Redescription. Male and female: Body 4.5–5.0 mm (fore body 2.0–2.2 mm) in length,
weakly to moderately shining, with antennae moderately long, thin. Head black; pronotum, elytra
and abdomen dark reddish brown to dark brown; labrum dark brown; antennae and legs reddish
brown. Head weakly concave, with a pair of longitudinal furrows; punctures round to almost
round, moderately dense to dense, small, somewhat umbilicate. Pronotum with surface uneven
with indistinct median longitudinal furrow; punctures round to almost round, very dense, coarse,
sometimes subrugose. Elytra with surface uneven, almost ﬂat near suture; punctures round toalmost round, very dense, various in size but moderately large on average, coarse. Tarsi eachwith 4th tarsomere strongly bilobed. Abdomen with punctures round, moderately dense, small,regular in anterior segments, while punctures in posterior segments very small, sparse. Lateroventrites and tergoventrite sutures missing.
Male: Seventh ventrite (Fig. 19H) medially with an elongate ﬂat area, which is very shallowly emarginate; 8th ventrite (Fig. 19H) posteromedially with an arcuate emargination; 9th tergum (Fig. 19A) with antecostal apophyses long; 9th ventrite (Fig. 19D) hardly serrate posteri-

The Steninae of Japan Part 2

Fig. 19. Stenus kumoma Naomi (Hayachine, Iwate). A, 9th and 10th terga of male; B, spermatheca; C, aedeagus;
D, 9th ventrite of male; E, copulatory tube; F, expulsion hooks; G, posterior part of gonocoxite; H, 7th and 8th
ventrites of male. Scale 1: 0.2 mm for A, C, D, 0.1 mm for B, E–G; Scale 2: 0.3 mm for H.

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Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

orly, with macrosetae relatively short, apicolateral teeth acutely pointed, apicolateral setae
moderately long; 10th tergum (Fig. 19A) very weakly emarginate posteriorly. Aedeagal median
lobe (Fig. 19C) broad, distinctly angulate apicolaterally; apical sclerotized area (Fig. 19C) developed, subtriangular, with median cusp short, pointed, lateral subcusps short, angulate. Endophallic median bands (Fig. 19C) each short, very broad at base, narrowed anteriorly; lateral bands(Fig. 19C) thin; expulsion hooks (Fig. 19F) connected by a membranous bar at the mesial sidesof posterior plates, each hook almost elongate-triangular, sclerotized along the lateral margin,
with anterior plate demarcated by a suture from posterior plate; copulatory tube (Fig. 19E) verylarge, with basal chamber ovoidal, main tube subrhombic, with apical processes each long, thin,lateral processes each broad, pointed, membranous plate large, rounded posteriorly. Parameres(Fig. 19C) robust, each weakly incurved and pointed at the apicalmost part; apical area stout,
very long, swollen and distinctly angulate mesially at base, having a very low dorsal and a very
low ventral ﬂaps, furnished mesially with 7 setae of various lengths.
Female: Eighth ventrite obtusely pointed posteromedially; gonocoxites (Fig. 19G) toothed
posteriorly, each with apicolateral tooth long, acutely pointed, apicolateral setae very long. Spermatheca (Fig. 19B) with capsule rounded apically, very small; RT-duct long, thick; duct very
long, usually thin but moderately thick to thick at the distal part, almost tightly coiled; basal
valve short, a little shorter than basal sclerotized duct; basal pouch broad-conical, sclerotized distally.
Biology and ecology. S. kumoma is presently collected only from Mt. Hayachine of Tohoku
district, Honshu. The beetles inhabit leaf litter in the natural forests.
Remarks. S. kumoma is allied to S. izanagi, but it is separable from the latter species by the
body smaller, the 9th tergum with its antecostal apophysis thinner (Fig. 19A), the 9th ventrite
with its apicolateral tooth longer and more strongly pointed (Fig. 19D), the endophallic expulsion hook subtriangular (Fig. 19F), the copulatory tube with its basal chamber large (Fig. 19E),
and the spermatheca with its duct much longer and thinner (Fig. 19B). Note that the endophallic
expulsion hook of S. kumoma is, interestingly, similar in structure to the expulsion hook (e.g.,
Fig. 57G) of some members of the inimitabilis-subgroup of indubius-group.
Etymology. The speciﬁc epithet of this species is derived from a Japanese noun “kumoma”,
which means the “blue sky broken through the clouds”. This word is often used for describing abeautiful scenery that we can see at the high mountains like Mt. Hayachine.
Stenus izanagi Naomi & Puthz(Figs. 20A, C–J, 103F)
Stenus izanagi Naomi & Puthz, 1994: 302; Herman, 2001: 2236; Naomi & Puthz, 2013: 142.
Type material. Holotype: 1 ♂ (CBM), Mt. Hayachine, Hanamaki City, Iwate Pref., 17. vii.
1985, S. Nomura leg.
Other material examined. [HONSHU]: 1 ♂, Mt. Hayachine, Hanamaki City, Iwate Pref., 17.
vii. 1985, S. Nomura leg.; 1 ♂1 ♀, Mt. Kattadake, Miyagi Pref., 22. ix. 1991, Y. Hirano leg.
Distribution. Japan: Honshu (Iwate and Miyagi Prefs.).
Redescription. Male and female: Body 5.0–5.5 mm (fore body 2.3–2.6 mm) in length, robust,
weakly to moderately shining, with antennae moderately long, thin. Head and abdomen darkbrown to black; pronotum and elytra dark reddish brown; labrum reddish brown to dark brown;
antennae reddish brown, with apical segments infuscate; legs reddish brown. Head weakly con-

The Steninae of Japan Part 2

Fig. 20. A, C–J, Stenus izanagi Naomi (A, H, Hayachine, Iwate; C–G, I, J, Kattadake, Miyagi); B, S. nomuraianus Puthz (Cheon, Korea). A, spermatheca; B, C, expulsion hooks; D, copulatory tube; E, 9th and 10th tergaof male; F, 9th ventrite of male; G, aedeagus; H, posterior part of gonocoxite; I, apex of paramere; J, 7th and8th ventrites of male. Scale 1: 0.1 mm for A, H, I; 0.05 mm for B; Scale 2: 0.2 mm for E–G, 0.1 mm for C, D;
Scale 3: 0.3 mm for J.

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Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

cave, with a pair of longitudinal furrows; punctures round to elliptical, moderately dense todense, small. Pronotum with surface uneven, median longitudinal furrow indistinct, with its central area weakly concave; punctures round, very dense, various in size, coarse, subrugose. Elytra
with surface uneven, weakly depressed near the base of suture; punctures round to almost round,very dense, various in size but moderately large on average, coarse. Tarsi each with 4th tarsomere strongly bilobed. Abdomen with punctures round, moderately dense, small, regular in anterior segments, while punctures in 7th and 8th segments very ﬁne, sparse. Lateroventrites and tergoventrite sutures missing.
Male: Legs with femora thick; 7th ventrite (Fig. 20J) posteromedially with a bell-shaped ﬂatarea; 8th ventrite (Fig. 20J) posteromedially with a subtriangular emargination; 9th tergum (Fig.
20E) with antecostal apophyses long, very broad; 9th ventrite (Fig. 20F) minutely serrate posteriorly, with macrosetae relatively short, apicolateral tooth short, pointed, apicolateral setae moderately long; 10th tergum (Fig. 20E) rounded posteriorly. Aedeagal median lobe (Fig. 20G) broad,angulate at apicolateral corners; apical sclerotized area (Fig. 20G) broad-subtriangular, withmedian cusp moderately long, thick, lateral cusps short, pointed. Endophallic median bands (Fig.
20C) each short, very broad at base, strongly narrowed anteriorly; lateral bands (Fig. 20C) moderately long and broad; expulsion hooks (Fig. 20C) widely separated, each hook with anterior
plate small, nearly V-shaped, demarcated by a cleft from posterior plate, the posterior platealmost C-shaped, thin; copulatory tube (Fig. 20D) large, robust, with basal chamber hardly
developed, main tube subrhombic, with apical processes each long, pointed, lateral processes
each thick, membranous plate weakly emarginate apicolaterally. Parameres (Fig. 20G) each verybroad at base, weakly turning laterally at apical area, pointed at apex; apical area (Fig. 20I) moderately long, swollen and distinctly angulate mesially at base, having a low dorsal and a subtriangular ventral ﬂaps, furnished basally with a tuft of 5 to 6 setae, apically with 3 setae, and alsowith 2 short setae on ventral ﬂap.
Female: Eighth ventrite obtusely angulate posteromedially; gonocoxites (Fig. 20H) each withapicolateral tooth long, acutely pointed, apicolateral setae long. Spermatheca (Fig. 20A) with
capsule subovoidal, rounded apically; RT-duct long, thick to very thick; duct moderately long,thick to very thick, almost tightly coiled; basal valve short; basal sclerotized duct long; basal
pouch mushroom-shaped.
Biology and ecology. S. izanagi is a rare species; and it is distributed in the high mountainous
regions of Tohoku district, Honshu. The beetles inhabit leaf litter in the natural forests.
Remarks. S. izanagi is allied to S. kumoma, but it is separable from the latter species by the
body larger, the 9th tergum with its antecostal apophysis thicker (Fig. 20E), the 9th ventrite with
its apicolateral tooth shorter and less strongly pointed (Fig. 20F), the endophallic expulsion hookwith its anterior plate nearly V-shaped and its posterior plate almost C-shaped (Fig. 20C), thecopulatory tube with its basal chamber almost missing (Fig. 20D), and the spermatheca with its
duct shorter and thicker (Fig. 20A). Note that S. izanagi has a peculiar expulsion hook, as
described above (i.e., the anterior plate small and nearly V-shaped; and the posterior plate almost
C-shaped and much longer than the anterior plate). This peculiar condition is not found in S.
kumoma, but also in the other members of kasumi-subg. in Japan. However, the very similar condition of expulsion hook (Fig. 20B) is found in S. nomuraianus (Fig. 108I) from Korea. This may
show that S. izanagi is allied also to S. nomuraianus.
Etymology. The speciﬁc epithet of this species is derived from the name of god “Izanagi”,
which appears in the Japanese ancient mythology.

The Steninae of Japan Part 2

53

The asyura-subgroup
The asyura-subg. was only recently ﬁrst recognized as a subgroup (13 species) of the asyura-group in the list of Japanese Steninae (Naomi & Puthz, 2013); and the diagnostic characters
were not described there. At present, this subgroup comprises 24 species in Japan; and it is hereﬁrst characterized as below. The robust autapomorphic characters are not found for the whole
subgroup. However, based on the unique combination of the characteristic habitus with yellowish brown to reddish brown coloration (Fig. 104A, K), the less-developed modiﬁcations of the
6th and 7th ventrites of male (Fig. 32C), and the several important aedeagal characters (asdescribed below), the asyura-subg. can be characterized to form a natural group.
Diagnostic characters of the asyura-subgroup: Habitus and coloration (yellowish brown toreddish brown) (Figs. 104K, 108J) usually similar to some members of the cephalotes-groupwith bright coloration (e.g., S. okamotoi Naomi, 1989a), but a few species (e.g., S. clio; S. nogohakusanus) having the reddish brown to dark reddish brown coloration (Fig.103I); antennae usually moderately long; abdomen without lateroventrites nor tergoventrite sutures in 4th to 6th segments (Hypostenus-type). Male: Ninth ventrite with relatively small apicolateral teeth (Figs. 32F,
39A); aedeagal paramere often furnished with the anteriorly curved setae (Figs. 28E, 33B) and 2
rather long setae (Figs. 24C, 36E), in addition to the common, straight setae of various length;
endophallic expulsion hooks well-developed, variously formed; copulatory tube with main tube
simple and attenuate (Figs. 21E, 4E), sometimes strongly curved (Fig. 28E), rarely modiﬁed withspiral (Fig. 31C), funnel (Fig. 36C), paired lateral processes (Fig. 33D) or apical swollen area
(Figs. 35B, 39D). Female: Gonocoxite with apicolateral tooth acutely pointed, apicolateral setaevery long (Fig. 21E); spermathecal RT-duct usually moderately long and thick, but rarely very
thick (Figs. 32B, 40A); spermathecal duct short with 2 turns (Fig. 23C), moderately long (Fig.
36B) or very long (Fig. 27A), with surface usually smooth (Fig. 39H), but rarely covered sporadically with small tubercles (Fig. 33F).
Key to the Japanese species of the asyura-subgroup1(18) Male: Aedeagal median lobe simply angulate or pointed at apex.
2(3) Male: Endophallic expulsion hooks fused to form a Y-shaped structure (Fig. 42B) ............
..................................................................................................................S. yukawai Naomi
3(2) Male: Endophallic expulsion hooks composed of paired sclerites.
4(5) Male: Endophallic expulsion hook with posterior plate bilobed (Fig. 26E) .........................
....................................................................................................................... S. hijiri Naomi
5(4) Male: Endophallic expulsion hook with posterior plate not bilobed.
6(9) Male: Aedeagal paramere with apical area longer; endophallic expulsion hook with anterior plate bipartite.
7(8) Male: Endophallic expulsion hook with posterior plate shortly projecting and acutely
pointed posterolaterally (Fig. 24D); copulatory tube only weakly curved at apex (Fig.
24C)...................................................................................................S. komonoensis Naomi
8(7) Male: Endophallic expulsion hook with posterior plate not having posterolateral projection (Fig. 25E); copulatory tube strongly curved at apex (Fig. 25B) ..... S. anfractus Naomi
9(6) Male: Aedeagal paramere with apical area shorter; endophallic expulsion hook with anterior plate solid.
10(13) Male: Eighth ventrite more shallowly emarginate. Female: Spermatheca with RT-duct

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Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

attached at the apicolateral side of the weakly swollen distal part of spermathecal duct.
11(12) Male: Aedeagal median lobe with apical sclerotized area as broad as the median lobe atapicolateral corners (Fig. 21E); endophallic expulsion hook shorter (Fig. 21E) ..................
................................................................................................................. S. brendelli Naomi
12(11) Male: Aedeagal median lobe with apical sclerotized area much narrower than the median
lobe at apicolateral corners (Fig. 22E); endophallic expulsion hook longer (Fig. 22G) ......
..............................................................................................................S. ruricolaris Naomi
13(10) Eighth ventrite more deeply emarginate. Female: Spermatheca with RT-duct simply connected with spermathecal duct antero-posteriorly.
14(17) Male: Endophallic expulsion hook more or less rounded posterolaterally; copulatory tube
without lateral processes.
15(16) Male: Aedeagal median lobe simply pointed at apex (Fig. 23A); endophallic copulatory
tube weakly curved near apex (Fig. 23A). Female: Spermatheca with duct much shorter
with 2 turns (Fig. 23C) .................................................................................... S. clio Naomi
16(15) Male: Aedeagal median lobe pointed apically with median cusp (Fig. 28E); endophallic
copulatory tube strongly curved (Fig. 28E). Female: Spermatheca with duct much longer,
tightly coiled (Fig. 28B)............................................................... S. oisami Naomi & Puthz
17(14) Male: Endophallic expulsion hook acutely pointed posterolaterally (Fig. 33B); copulatory
tube with lateral processes (Fig. 33D) ..... S. tsukubamontis Naomi, Nomura & Kamezawa
18(1) Male: Aedeagal median lobe tricuspidate at apex.
19(22) Male: Endophallic expulsion hooks fused to form a Y-shaped structure.
20(21) Male: Aedeagal median lobe simply tricuspidate at apex (Fig. 43B); endophallic copulatory tube only weakly curved near the middle (Fig. 43D) .............................S. alesi Naomi
21(20) Male: Aedeagal median lobe tricuspidate apically, but distinctly excavated at the base of
median cusp (Fig. 44B); endophallic copulatory tube distinctly constricted near the middle (Fig. 44D) ............................................................................................S. daikoku Naomi
22(19) Male: Endophallic expulsion hooks composed of paired sclerites.
23(38) Male: Endophallic copulatory tube simple or only weakly modiﬁed (e.g., weakly curved
near the middle; weakly swollen apically).
24(27) Male: Aedeagal median lobe with median and lateral cusps much smaller. Female: Spermatheca with duct longer, thinner.
25(26) Male: Endophallic expulsion hook narrower, acutely pointed anteriorly (Fig. 27B); copulatory tube with main tube straight except for the weakly curved apex (Fig. 27B) ..............
............................................................................................................. S. maruyamai Naomi
26(25) Male: Endophallic expulsion hook broader, obtusely angulate anteriorly (Fig. 29F); copulatory tube with main tube strongly curved (Fig. 29C)........................... S. biwa Hromádka
27(24) Male: Aedeagal median lobe with median and lateral cusps much larger. Female: Spermatheca with duct shorter, thinner. (Note: Spermatheca of S. fulvivestis not observed).
28(31) Male: Endophallic copulatory tube weakly swollen at apex.
29(30) Male: Aedeagal median lobe larger (Fig. 35B); paramere with apical area furnished mesially with dense setae (Fig. 35B); endophallic expulsion hook broader, projecting posterolaterally (Fig. 35B) ............................................................................... S. ellipsoides Naomi
30(29) Male: Male: Aedeagal median lobe smaller (Fig. 39B); paramere with apical area mesially having two separated setal areas (Fig. 39B); endophallic expulsion hook narrower,
projecting posteriorly (Fig. 39G) ............................................................... S. asyura Naomi
31(28) Male: Endophallic copulatory tube pointed at apex.

The Steninae of Japan Part 2

55

32(33) Male: Aedeagal paramere longer (Fig. 34A); endophallic expulsion hook distinctly angulate posterolaterally (Fig. 34E) ..................................................................S. santira Naomi
33(32) Male: Aedeagal paramere shorter; endophallic expulsion hook rounded posterolaterally.
34(35) Male: Aedeagal median lobe with apical sclerotized area more developed, having thenotch between the median and lateral cusps deeper (Fig. 40E) .......... S. hakonensis Naomi
35(34) Male: Aedeagal median lobe with apical sclerotized area less developed, having the notch
between the median and lateral cusps shallower.
36(37) Male: Endophallic expulsion hook narrower (Fig. 37F); copulatory tube with main tube
thicker, moderately curved at apex (Fig. 37E) ..................S. fulvivestis Naomi & Watanabe
37(36) Male: Endophallic expulsion hook broader (Fig. 41G); copulatory tube with main tube
thinner, simply attenuate toward apex (Fig. 41B) .................................................................
................................................................ S. nogohakusanus Naomi, Nomura & Kamezawa
38(23) Male: Endophallic copulatory tube strongly modiﬁed (e.g., with ﬂaps, spiral, funnel, lateral or apical processes).
39(40) Male: Endophallic copulatory tube spiral (Fig. 31C) ............................ S. araiorum Naomi
40(39) Male: Endophallic copulatory tube not spiral.
41(42) Male: Aedeagal median lobe with median cusp much longer (Fig. 38F); endophallic
expulsion hook rounded posteriorly (Fig. 38D)......................................... S. basara Naomi
42(41) Male: Aedeagal median lobe with median cusp much shorter; endophallic expulsion hookangulate or pointed posterolaterally.
43(46) Male: Aedeagal paramere shorter; endophallic copulatory tube with main tube not funnelformed.
44(45) Male: Aedeagal median lobe with lateral cusp usually composed of a simple angulation(Fig. 30H); endophallic expulsion hook thinner (Fig. 30H). Female: Spermatheca with
capsule and RT-duct much thinner (Fig. 30B) ............................................S. bicara Naomi
45(44) Male: Aedeagal median lobe with lateral cusp small but distinctly pointed (Fig. 32D);
endophallic expulsion hook thicker (Fig. 32H). Female: Spermatheca with capsule and
RT-duct much thicker (Fig. 32B) ..............................................................S. jyurojin Naomi
46(43) Male: Aedeagal paramere longer (Fig. 36E); endophallic copulatory tube with its maintube funnel-formed (Fig. 36C) ...................................... S. protuberans Naomi & Watanabe
Stenus brendelli Naomi(Figs. 21A–F, 103G)
Stenus brendelli Naomi, 1997: 755; Herman, 2001: 2098; Naomi & Puthz, 2013: 143.
Type material examined. Holotype: ♂ (CBM), Mt. Jyôyama, Munakata, Fukuoka Pref., 8. iii.
1986, S. Nomura leg. Paratype: 1 ♀ (cN), same data as holotype.
Distribution. Japan: Kyushu (Fukuoka Pref.).
Redescription. Male and female: Body 4.0–4.5 mm (fore body 1.9–2.1 mm) in length, moderately shining, with antennae moderately long, thin. Head dark reddish brown to black; pronotum, elytra and abdomen reddish brown to dark reddish brown; labrum reddish brown; antennae
yellowish or reddish brown, with apical segments more or less infuscate; legs yellowish brown toreddish brown. Head weakly concave, with a pair of midlateral longitudinal furrows; puncturesround, moderately dense to dense, small, somewhat umbilicate. Pronotum with surface weakly
uneven, with indistinct median longitudinal furrow; punctures round, very dense, moderately large,

56

Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

Fig. 21. Stenus brendelli Naomi (Jôyama, Fukuoka). A, 6th to 8th ventrites of male; B, 9th and 10th terga ofmale (antecostal apophyses not illustrated); C, spermatheca; D, 9th ventrite of male; E, aedeagus; F, posterior
part of gonocoxite. Scale 1: 0.3 mm for A; Scale 2: 0.2 mm for B, D, E, 0.1 mm for C, F.

The Steninae of Japan Part 2

57

somewhat coarse, two or more punctures sometimes partially fused. Elytra with surface uneven,almost ﬂat or weakly depressed near suture; punctures round to elliptical, very dense, moderately
large, coarse. Tarsi each with 4th tarsomere strongly bilobed. Abdomen with punctures round toalmost round, moderately dense, small, almost regular in anterior segments, while punctures in 7th
and 8th segments sparse to moderately dense, shallow. Lateroventrites missing; tergoventrite suture
existing only at the base of each segment, virtually missing in the posterior part.
Male: Sixth ventrite (Fig. 21A) posteromedially with an elongate shallow depression, which
is very shallowly emarginate; 7th ventrite (Fig. 21A) medially with an elongate depression,
which is arcuately emarginate posteriorly; 8th ventrite (Fig. 21A) anteromedially with a bellshaped, shallow despression, posteriorly with a small, nearly semicircular emargination; 9th tergum as in Fig. 21B; 9th ventrite (Fig. 21D) serrate posteriorly, with macrosetae moderately long,apicolateral teeth pointed, apicolateral setae moderately long; 10th tergum (Fig. 21B) very
weakly emarginate posteriorly. Aedeagal median lobe (Fig. 21E) broad, angulate apicolaterally,
simply pointed at apex; apical sclerotized area (Fig. 21E) triangular, covered sparsely with thin,short setae. Endophallic median bands (Fig. 21E) each with basal band moderately broad, gently
incurved, folded bands fused each other; lateral bands (Fig. 21E) thin; expulsion hooks (Fig.
21E) connected at the posteromesial corners, each hook almost C-shaped, thin, pointed at anterior tip; copulatory tube (Fig. 21E) with basal chamber almost elongate-ovoidal, main tube simply rod-like. Parameres (Fig. 21E) each weakly incurved, pointed at apex; apical area large, long,moderately swollen mesially, furnished mesially with 11 to 12 setae of different length.
Female: Eighth ventrite obtusely angulate posteromedially; gonocoxites (Fig. 21F) each
toothed posteriorly, with apicolateral tooth long, acutely pointed, apicolateral setae very long.
Spermatheca (Fig. 21C) robust, with capsule conical, very small; RT-duct moderately long, thick,branched from the lateral side of the distal swollen area of spermathecal duct; duct short with
two turns, with the distal part becoming thicker distally; basal valve short; basal sclerotized duct
short. Basal structure (Fig. 21C) very large, broad-conical.
Biology and ecology. S. brendelli is known only from the low mountainous region of thenorthern part of Kyushu. The beetles inhabit leaf litter in the natural forests.
Remarks. Given their common possession of the peculiar spermathecal structure (i.e., RTduct branched from the lateral side of the distal swollen area of the spermathecal duct; Figs. 21C,
22F), S. brendelli is the sister species of S. ruricolaris, and it is separable from the latter species
by the aedeagal median lobe with its apical sclerotized area larger and broader (Fig. 21E) and theendophallic explusion hook is C-shaped (Fig. 21E).
Etymology. This species is named in honor of Mr. Martin J. D. Brendell (Natural History
Museum, London).
Stenus ruricolaris Naomi(Figs. 22A–G, 103H)
Stenus ruricolaris Naomi, 1998: 102; Herman, 2001: 2375; Naomi & Puthz, 2013: 143.
Type material examined. Holotype: ♂ (CBM), Mt. Tachibana, Fukuoka City, Fukuoka Pref.,21. vii. 1986, S. Naomi leg. Paratype: 1 ♂11 ♀ (cN), same data as holotype.
Other material examined. [KYUSHU]: 1 ♂ (cN), same data as holotype.
Distribution. Japan: Kyushu (Fukuoka Pref.).
Redescription. Male and female: Body 3.8–4.7 mm (fore body 1.8–2.2 mm) in length, mod-

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Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

Fig. 22. Stenus ruricolaris Naomi (Tachibana, Fukuoka). A, 9th and 10th terga of male; B, 6th to 8th ventrites ofmale; C, 9th ventrite of male; D, posterior part of gonocoxite; E, aedeagus; F, spermatheca; G, expulsion
hooks. Scale 1: 0.2 mm for A, C, E, 0.1 mm for D, F, G; Scale 2: 0.3 mm for B.

erately shining, with antennae moderately long, thin. Head and abdomen dark reddish brown to
black; pronotum and elytra reddish brown; labrum reddish brown; antennae and legs yellowish
brown to reddish brown. Head weakly concave, with a pair of longitudinal furrows; puncturesround, moderately dense to very dense, small, somewhat umbilicate. Pronotum with surface
uneven, with indistinct median longitudinal furrow; punctures round, very dense, moderately
large, coarse, two or more punctures sometimes partially fused. Elytra with surface uneven,

The Steninae of Japan Part 259

almost ﬂat or weakly depressed near suture; punctures round to almost round, very dense, moderately large, coarse. Tarsi each with 4th tarsomere strongly bilobed. Abdomen with puncturesround to elliptical, dense, small, almost regular in anterior segments, while punctures in 7th and8th segments sparse to moderately dense, shallow. Lateroventrites missing; tergoventrite sutures
almost missing but sometimes existing, very thin.
Male: Fifth ventrite posteromedially with a bell-shaped ﬂat area; 6th ventrite (Fig. 22B) posteromedially with a shallow, elongate-subtrapezoidal depression which is very shallowly emarginate; 7th ventrite (Fig. 22B) posteromedially with a large, bell-shaped depression, which isarcuately emarginate; 8th ventrite (Fig. 22B) anteromedially with a short, shallow depression,
posteriorly with a semicircular emargination; 9th tergum (Fig. 22A) with antecostal apophyses
moderately long; 9th ventrite (Fig. 22C) minutely serrate posteriorly, with macrosetae relatively
short, apicolateral teeth short, pointed, apicolateral setae short; 10th tergum (Fig. 22A) weakly
emarginate. Aedeagal median lobe (Fig. 22E) broad, gently rounded apicolaterally, weakly swollen at the area just dorsal from the apicolateral corner, acutely pointed at apex; apical sclerotizedarea (Fig. 22E) triangular, narrow, covered sparsely with very thin, short setae. Endophallic
median bands (Fig. 22E) each with ventral band long, relatively thin; lateral bands (Fig. 22E)
long, thin; expulsion hooks (Fig. 22G) connected at the posteromesial corners, each broad,rounded posteriorly; copulatory tube (Fig. 22E) long, with basal chamber nearly elongate-elliptical, basal constriction indistinct, main tube rod-like, weakly, twice constricted on its way. Parameres (Fig. 22E) each weakly incurved, acutely pointed apically; apical area large, robust, long,moderately swollen mesially, furnished mesially with 9 to 12 setae of different length.
Female: Eighth ventrite almost rounded posteriorly; gonocoxites (Fig. 22D) toothed posteriorly, each with apicolateral tooth very long, acutely pointed, apicolateral setae very long. Spermatheca (Fig. 22F) stout, with capsule very small; RT-duct moderately long, thick, branchedfrom the lateral side of the distal swollen area of spermathecal duct; duct thick to very thick,short with two turns, the distal part becoming swollen distally; basal valve very short; basal
sclerotized duct moderately long.
Biology and ecology. S. ruricolaris is known only from the low mountainous region of thenorthern part of Kyushu. The beetles inhabit leaf litter in the natural forests.
Remarks. S. ruricolaris is the sister species of S. brendelli, and it is separable from the latter
species by the aedeagal median lobe with its apical sclerotized area smaller and narrower (Fig.
22E) and the endophallic explusion hooks each much thicker (Fig. 22G). Given their common
possession of the structural similarities on the endophallic expulsion hooks and copulatory, S.
ruricolaris is also allied to S. clio, but it is separable from the latter species by the aedeagal
median lobe weakly swollen at the area just dorsal from the apicolateral corner (Fig. 22E), theparamere with its apical area longer (Fig. 22E), and the spermatheca with its duct distinctly
thickened at the distal part (Fig. 22F).
Stenus clio Naomi(Figs. 23A–F, 103I)
Stenus clio Naomi, 2015: 20.
Type material examined. Holotype: ♂ (CBM), Mt. Kamagadake, Komono-cho, Mie Pref.,27. viii. 1994, H. Yokozeki leg. Paratypes: 3 ♂1 ♀ (cN), same data as holotype.
Distribution. Japan: Honshu (Mie Pref.).

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Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

Fig. 23. Stenus clio Naomi (Kamagatake, Mie). A, aedeagus; B, expulsion hooks; C, spermatheca; D, apical partof 9th ventrite of male; E, posterior part of 8th ventrite of male; F, posterior part of 8th ventrite of female.
Scale: 0.2 mm for A, E, F, 0.1 mm for B–D.

Redescription. Male and female: Body 3.5–3.8 mm (fore body 1.8–2.0 mm) in length,
weakly shining, with antennae moderately long, thin. Head dark brown to black; pronotum andelytra reddish brown; abdomen dark reddish brown; labrum reddish brown; antennae and legs
yellowish brown to reddish brown. Head weakly concave, with a pair of longitudinal furrows;
punctures round, moderately dense to dense, and small except for the sparsely punctate medianarea. Pronotum with surface uneven, with indistinct median longitudinal furrow; punctures roundto elliptical, very dense, moderately large, coarse. Elytra with surface weakly uneven, almost ﬂat

The Steninae of Japan Part 2

61near suture; punctures round to elliptical, very dense, large, somewhat coarse. Tarsi each with 4thtarsomere strongly bilobed. Abdomen with punctures round to elliptical, moderately dense todense, small in anterior segments, while punctures in posterior segments elliptical, very small.
Lateroventrites missing; tergoventrite sutures existing, distinct.
Male: Sixth ventrite posteromedially with or without a semicircular ﬂat area; 7th ventrite
posteromedially with or without a very shallow, elongate-elliptical depression, which is very
shallowly emarginate; 8th ventrite (Fig. 23E) posteromedially with a deep, moderately large
emargination; 9th tergum with ventral apophyses relatively long, thin; 9th ventrite (Fig. 23D)
irregularly, indistinctly serrate posteriorly, with macrosetae short, apicolateral teeth short, apicolateral setae long; 10th tergum entire. Aedeagal median lobe (Fig. 23A) broad, distinctly angulateapicolaterally, simply pointed at apex; apical sclerotized area (Fig. 23A) weakly developed,
widely arcuate at apicomedian margin. Endophallic median bands (Fig. 23A) long, broad; lateralbands (Fig. 23A) long, very thin; expulsion hooks (Fig. 23B) large, robust, connected at themesial margins of posterior plates, with anterior plate roughly crenulate at mesial margin, demarcated by a curved suture from posterior plate, the posterior plate composing of its strongly sclerotized anterolateral part, and its posterior part with a low, folded rim along posterolateral margin;
copulatory tube (Fig. 23A) with basal chamber large, ovoidal, main tube attenuate but slightly
curved in apical half. Parameres (Fig. 23A) each slender, almost straight; apical area short,hardly swollen mesially, furnished mesially with 9 to 10 short setae at marginal area.
Female: Eighth ventrite (Fig. 23F) weakly angulate posteromedially; gonocoxites eachhardly serrate posteriorly, with apicolateral tooth long, acutely pointed, apicolateral setae long.
Spermatheca (Fig. 23C) with capsule missing; RT-duct moderately long and thick; spermathecal
duct moderately thick to thick, short with two turns; basal valve very short; basal sclerotized duct
stout, long. Basal structure elongate-conical, membranous.
Biology and ecology. S. clio is a rare species; and it is collected only once from the mountainous region of Kansai district, Honshu. The beetles inhabit leaf litter in the natural forest.
Remarks. The 3 distinct but morphologically similar species S. clio, S. komonoensis and S.
anfractus all are distributed in the eastern part of Kansai district. S. clio is allied to S. komonoensis and S. anfractus, but it is separable from them by the 8th ventrite with the larger emargination(Fig. 23E), and the endophallic expulsion hook with its posterior plate rounded posteriorly (Fig.
23B). S. clio is also allied to S. ruricolaris from Kyushu, but it is separable from the latter species by the aedeagal median lobe simply pointed at the apicolateral corner (Fig. 23A), the paramere with its apical area shorter (Fig. 23A), and the spermathecal duct most thick at the 2nd turnand then becoming thinner distally (Fig. 23C).
Stenus komonoensis Naomi(Figs. 24A–G, 103J)
Stenus komonoensis Naomi, 2015: 5.
Type material examined. Holotype: ♂ (CBM), Komono-cho, Mie Pref., 26. xi. 1989, A.
Amagasu leg.
Other material examined. [HONSHU]: 1 ♂3 ♀, Mt. Gozaisho, Mie Pref., 11. x. 2009, T. Itoleg.
Distribution. Japan: Honshu (Mie Pref.).
Redescription. Male and female: Body 3.9–4.5 mm (fore body 2.0–2.2 mm) in length,

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Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

Fig. 24. Stenus komonoensis Naomi (A, B, F, G, Gozaisho, Mie; C, D, E, Komono, Mie). A, spermatheca; B, 9th
and 10th terga of male; C, aedeagus; D, expulsion hooks; E, 6th to 8th ventrites of male; F, 9th ventrite ofmale; G, posterior part of gonocoxite. Scale 1: 0.1 mm for A, D, G, 0.2 mm for B, C, F; Scale 2: 0.3 mm forE.

The Steninae of Japan Part 2

63

weakly shining, with antennae moderately long, very thin, legs moderately thick. Head black;prothorax, elytra and abdomen reddish brown to dark red; labrum reddish brown; antennae reddish brown to dark reddish brown; legs yellowish brown to reddish brown. Head weakly concave, with a pair of longitudinal furrows; punctures round, moderately dense, small. Pronotumwith surface weakly uneven, with indistinct median longitudinal furrow; punctures round, very
dense, moderately large. Elytra with surface very weakly uneven; punctures round, very dense,
moderately large. Tarsi with 4th tarsomeres strongly bilobed. Abdomen with punctures round,moderately dense, various in size, regular in anterior segments, while punctures in 7th and 8th
segments very small, indistinct. Lateroventrites and tergoventrite sutures missing.
Male: Sixth ventrite (Fig. 24E) posteromedially with a transverse ﬂat area; 7th ventrite (Fig.
24E) medially with an elongate shallow depression, which is weakly emarginate; 8th ventrite(Fig. 24E) posteriorly with a subtriangular emargination; 9th tergum (Fig. 24B) with antecostal
apophyses moderately long; 9th ventrite (Fig. 24F) very minutely serrate posteriorly, with macrosetae long, apicolateral teeth acutely pointed, apicolateral setae long; 10th tergum (Fig. 24B)
weakly emarginate. Aedeagal median lobe (Fig. 24C) broad, distinctly angulate apicolaterally,
pointed at apex; apical sclerotized area (Fig. 24C) broad, subtriangular, arcuately emarginate
anteriorly. Endophallic median bands (Fig. 24C) long, moderately broad; expulsion hooks (Fig.
24D) connected posteromedially by membrane, with the anterior plate divided antero-posteriorly
into two parts, demarcated by a transverse suture from posterior plate, the posterior plate membranous posteromesially, weakly protruding and pointed posterolaterally; copulatory tube (Fig.
24C) long, with basal chamber almost elliptical, main tube weakly constricted twice or thrice,
weakly curved in its full length. Parameres (Fig. 24C) long, each very acutely pointed andincurved at the apicalmost part; apical area very long, moderately swollen mesially, furnishedmesially with 8 to 10 setae of different length.
Female: Eighth ventrite pointed or angulate posteromedially; gonocoxites (Fig. 24G) toothed
posteriorly, each with apicolateral tooth very long, acutely pointed, apicolateral setae very long.
Spermatheca (Fig. 24A) with capsule very small; RT-duct moderately long and thick; duct thick,short with two turns; basal valve short; basal sclerotized duct long. Basal structure (Fig. 24A)
almost conical, membranous.
Biology and ecology. S. komonoensis is distributed in the plains and low mountainous
regions of Kinki district, Honshu. The beetles inhabit leaf litter in the natural forests.
Remarks. S. komonoensis is the sister species of S. anfractus, and it is separable from the latter species by the endophallic expulsion hook with its posterior plate distinctly protruding andpointed posterolaterally (Fig. 24D), and the copulatory tube with its main tube only weakly
curved at apex (Fig. 24C).
Stenus anfractus Naomi(Figs. 25A–E, 103K)
Stenus anfractus Naomi, 2015: 5.
Type material examined. Holotype: ♂ (CBM), Mt. Kamagadake, Komono-cho, Mie Pref.,27. viii. 1994, H. Yokozeki leg.
Distribution. Japan: Honshu (Mie Pref.).
Redescription. Male: Body 4.5 mm (fore body 2.2 mm) in length, robust, weakly shining,with antennae very thin, moderately long, legs moderately thick. Head black; prothorax, elytra

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Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

Fig. 25. Stenus anfractus Naomi (Kamagadake, Mie). A, 6th to 8th ventrites of male; B, aedeagus; C, 9th and10th terga of male; D, 9th ventrite of male; E, expulsion hooks. Scale 1: 0.3 mm for A; Scale 2: 0.2 mm for
B–D, 0.1 mm for E.

The Steninae of Japan Part 2

65

and abdomen dark red; labrum reddish brown; antennae reddish brown to dark reddish brown;legs yellowish brown to reddish brown. Head weakly concave, with a pair of longitudinal furrows; punctures round, sparse to moderately dense, small. Pronotum with surface weakly
uneven, with indistinct median longitudinal furrow; punctures round, very dense, moderately
large, coarse. Elytra with surface very weakly uneven, almost ﬂat near suture; punctures round,very dense, moderately large. Tarsi with 4th tarsomeres strongly bilobed. Abdomen with punctures round, moderately dense, various in size in anterior segments, while punctures in 7th and8th segments very small, indistinct. Lateroventrites and tergoventrite sutures missing.
Sixth ventrite (Fig. 25A) posteromedially with a bell-shaped ﬂat area; 7th ventrite (Fig. 25A)
anteromedially with a very shallow, small depression, posteromedially with a shallow, bellshaped depression, which is very weakly emarginate; 8th ventrite (Fig. 25A) posteriorly with ashallow, arcuate emargination; 9th tergum (Fig. 25C) with antecostal apophyses moderately long,thin; 9th ventrite (Fig. 25D) irregularly serrate posteriorly, with macrosetae moderately long, apicolateral teeth short, pointed, apicolateral setae moderately long; 10th tergum (Fig. 25C) weakly
emarginate. Aedeagal median lobe (Fig. 25B) broad, distinctly angulate apicolaterally, bluntly
pointed at apex; apical sclerotized area (Fig. 25B) broad, subtriangular. Endophallic medianbands (Fig. 25B) narrow, relatively long; expulsion hooks (Fig. 25E) moderately large, broadly
connected by membrane behind the middle, each with the anterior plate weakly incurved,
divided antero-posteriorly into two parts, demarcated by a transverse suture from posterior plate,the posterior plate membranous mesially, almost parallel-sided behind the middle; copulatory
tube (Fig. 25B) very long, stout, with basal chamber almost elliptical, main tube weakly constricted twice, strongly curved at apical part. Parameres (Fig. 25B) long, each very acutely
pointed at apex; apical area very long, moderately swollen mesially, furnished mesially with 8 to
9 setae of different length.
Female: Unknown.
Biology and ecology. S. anfractus is once collected in the mountainous region of Kinki district, Honshu. The beetle inhabits leaf litter in the natural forest.
Remarks. S. anfractus is the sister species of S. komonoensis, and it is separable from the latter species by the endophallic expulsion hooks with the posterior plates almost parallel-sided
behind the middle (Fig. 25E), and the copulatory tube with its main tube strongly curved at apex
(Fig. 25B).
Stenus hijiri Naomi(Figs. 26A–H, 103 L)
Stenus hijiri Naomi, 1989: 45; Herman, 2001: 2214; Naomi & Puthz, 2013: 143.
Type material. Holotype: ♂ (KUF), Hirogawara, Mt. Shirane, Yamanashi Pref., 9–13. vii.
1982, S. Naomi leg.
Type material examined. Paratype: 2 ♂5 ♀ (cN), same data as holotype.
Other material examined. [HONSHU]: 2 ♂2 ♀, Senpei Pass, Mt. Nyugasa, Nagano Pref., 24.
viii. 1997, H. Sakayori leg.; 1 ♂2 ♀, Mt. Norikura, Azumi Vil., Nagano Pref., 20. viii. 1996, S.
Nomura leg.; 1 ♂, Mt. Houou, Nirasaki City, Yamanashi Pref., 16. viii. 1996, T. Ito leg.; 2 ♂1 ♀,same locality, 13–15. viii. 1989, T. Ito leg.; 1 ♂, same locality, 11. x. 1997; 1 ♂, Gozaishi Spa,
Nirasaki City, Yamanashi Pref., 17. viii. 1996, T. Ito leg.
Distribution. Japan: Honshu (Nagano and Yamanashi Prefs.).

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Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

Fig. 26. Stenus hijiri Naomi (A–C, F–H, Hirogawara, Yamanashi; D, Nyugasa, Nagano; E, Gozaisho,
Yamanashi). A, 9th ventrite of male; B, copulatory tube; C, spermatheca; D, 9th and 10th terga of male; E,
apex of median lobe with inverted expulsion hooks and dorsal membrane; F, aedeagus; G, 7th and 8th ventrites of male; H, posterior part of gonocoxite. Scale 1: 0.2 mm for A, 0.1 mm for E, H; Scale 2: B, C for
0.1 mm, D, F for 0.2 mm; Scale 3: G for 0.3 mm.

The Steninae of Japan Part 2

67

Redescription. Male and female: Body 3.8–4.3 mm (fore body 1.9–2.1 mm) in length,
weakly shining or dull, with antennae relatively short, thin. Body entirely reddish brown but
head and abdomen infuscate. Head weakly concave, with a pair of longitudinal furrows; punctures round, moderately dense to dense, small, somewhat umbilicate. Pronotum with surface
uneven, with indistinct median longitudinal furrow; punctures round to almost round, very dense,coarse, subrugose. Elytra with surface uneven, weakly concave near suture; punctures round,very dense, various in size but moderately large in average, coarse, subrugose. Tarsi with 4th tarsomeres strongly bilobed. Abdomen with punctures round to elliptical, very dense, small in anterior segments, while punctures in posterior segments elliptical, sparse to moderately dense, verysmall, shallow. Lateroventrites and tergoventrite sutures missing.
Male: Legs moderately thick; 7th ventrite (Fig. 26G) posteromedially with an elongate shallow depression; 8th ventrite (Fig. 26G) posteromedially with a semicircular emargination; 9th
tergum (Fig. 26D) with antecostal apophyses very long; 9th ventrite (Fig. 26A) very minutely
serrate posteriorly, with macrosetae long, apicolateral teeth acutely pointed, apicolateral setae
long; 10th tergum (Fig. 26D) obtusely angulate posteromedially. Aedeagal median lobe (Fig.
26F) elongate, angulate apicolaterally, obtuse or weakly swollen at apex; apical sclerotized area
(Fig. 26E, F) hardly developed except for the weakly swollen apicomedian area. Endophallic
dorsal membrane (Fig. 26E) large, subovoidal, regularly dotted; median bands (Fig. 26F) moderately broad and long; lateral bands (Fig. 26F) short; expulsion hooks (Fig. 26E, F) each almost
Y-shaped; copulatory tube (Fig. 26B) long, with basal chamber subovoidal, main tube broad atbase, narrowed apically, only weakly curved at apex. Parameres (Fig. 26F) long, stout, with stem
incurved; apical area very large, long, thick, turning posterolaterally, swollen mesially at base,with a basal tuft of 7 to 8 setae; dorsal subtransparent ﬂap broad, furnished with 3 to 5 short and
10 to 12 moderately long setae along the mesial margin of its apical half.
Female: Eighth ventrite obtusely angulate posteromedially; gonocoxites (Fig. 26H) toothed
posteriorly, each with apicolateral tooth very long, acutely pointed, apicolateral setae very long.
Spermatheca (Fig. 26C) with capsule missing; RT-duct moderately long, thick; duct moderately
thick to thick, short with two turns; basal valve very short; basal sclerotized duct almost fusiform, surrounded at base by membrane. Basal structure (Fig. 26C) subconical, membranous.
Biology and ecology. S. hijiri is distributed in the high mountainous regions of central Honshu. The beetles inhabit leaf litter in the natural forests.
Remarks. Given their similarities regarding the modiﬁcation of 7th ventrite of male,aedeagus, spermatheca, etc., S. hijiri seems to be allied to S. komonoensis and S. anfractus, but it
is clearly separable from the latter two species by the endophallic expulsion hook Y-shaped (Fig.
26E).
Etymology. The speciﬁc epithet of this species is derived from the Japanese noun “Hijiri”
which here means “mountain ascetic”.
Stenus maruyamai Naomi(Figs. 27A–F, 104A)
Stenus maruyamai Naomi, 2004: 106; Naomi & Puthz, 2013: 143.
Type material examined. Holotype: ♂ (CBM), Sanjyo Spa, Tabayama Vil., Yamanashi Pref.,4. v. 1996, M. Maruyama leg. Paratype: 1 ♂ (cN), Magoso Valley, Okutama-cho, Tokyo, 12. vii.
1992, T. Kishimoto leg.

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Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

Other material examined. [HONSHU]: 3 ♂5 ♀, Karisaka, Ohtaki Vil., Saitama Pref., 30. v.
1997, S. Naomi leg.; 1 ♂1 ♀, Mt. Tenso, Okutama-cho, Tokyo, 14. iv. 2002, S. Nomura leg.;2 ♂, Nippara, Okutama-cho, Tokyo, 14. iv. 2002, S. Nomura leg.; 3 ♂2 ♀, Mt. Mitake, Tokyo,
12. viii. 1990, T. Ito leg.; 3 ♂1 ♀, Mt. Tanba, Yamanashi Pref., 27. v. 2001, K. Haga leg
Distribution. Japan: Honshu (Yamanashi and Saitama Prefs.; Tokyo-to).
Redescription. Male and female: Body 3.9–4.3 mm (fore body 2.0–2.2 mm) in length, moderately shining, with antennae moderately long, thin. Head dark brown, often with median area
reddish brown; pronotum and elytra reddish brown; abdomen reddish brown to dark brown;
labrum yellowish red; antennae and legs yellowish brown to reddish brown. Head weakly concave, with a pair of moderately deep, longitudinal furrows; punctures usually round, sparse tomoderately dense and small, but punctures at the median area very small. Pronotum with surface
uneven, with indistinct median longitudinal furrow; punctures round to elliptical, very dense,
moderately large, coarse, sometimes two or more punctures partially fused. Elytra with surface
uneven, weakly concave near suture; punctures round to almost round, very dense, moderately
large to large, coarse. Tarsi each with 4th tarsomere strongly bilobed. Abdomen with puncturesround, dense, very small in anterior segments, while punctures in posterior segments hardly
developed, each forming only setal socket. Lateroventrites and tergoventrite sutures missing.
Male: Seventh ventrite posteromedially with a bell-shaped, ﬂat area; 8th ventrite (Fig. 27C)
posteromedially with a moderately large, subtriangular emargination; 9th tergum (Fig. 27F) with
antecostal apophyses very long; 9th ventrite (Fig. 27D) minutely serrate and bi-arcuate posteriorly, with macrosetae short, apicolateral teeth acutely pointed, apicolateral setae long; 10th tergum (Fig. 27F) entire. Aedeagal median lobe (Fig. 27B) broad, distinctly angulate apicolaterally,minutely tricuspidate at apicomedian part; apical sclerotized area (Fig. 27B) weakly developed
only at the median part. Endophallic median bands (Fig. 27B) moderately long; lateral bands(Fig. 27B) very thin; expulsion hooks (Fig. 27B) widely separated but connected by the arcuate,
very thin rod, each thin, with the anterior plate small, acutely pointed anteriorly, much shorter
than, and demarcated by a suture from posterior plate, the posterior plate moderately curved laterally; copulatory tube (Fig. 27B) slender, with main tube thin, baculiform, straight but weakly
curved only at apical part. Parameres (Fig. 27B) each turning posterolaterally at the apical area;
apical part moderately long, swollen and distinctly angulate mesially at base, furnished mesiallywith a tuft of 5 to 6 short setae at base, with 17 to 18 short setae in apical half.
Female: Eighth ventrite minutely pointed posteromedially; gonocoxites (Fig. 27E) toothed
posteriorly, with apicolateral tooth very long, acutely pointed, apicolateral setae very long. Spermatheca (Fig. 27A) with capsule rounded apically, small; RT-duct moderately long, moderately
thick to thick; duct very long, usually thin but thick at the distalmost part, strongly coiled; basal
valve short; basal sclerotized duct about as long as basal valve. Bursa copulatrix (Fig. 27A) subtriangular, with its posterolateral corners each strongly protruding posterolaterally.
Biology and ecology. S. maruyamai is distributed in the mountainous regions of central Honshu. The beetles inhabit leaf litter in the natural forests.
Remarks. S. maruyamai is allied to S. oisami and S. biwa, but it is separable from the lattertwo species by the endophallic expulsion hook narrower and acutely pointed anteriorly (Fig.
27B) and the copulatory tube with its main tube thinner and straight at the middle (Fig. 27B).
Etymology. This species is named in honor of Dr. Munetoshi Maruyama (Kyushu University
Museum, Fukuoka), who studies the Aleocharinae (Staphylinidae), the myrmecophilous and termitophilous insects, and others.

The Steninae of Japan Part 2

Fig. 27. Stenus maruyamai Naomi (A, E, Karisaka, Saitama; B–D, F, Sanjyo, Yamanashi). A, spermatheca; B,
aedeagus; C, 8th ventrite of male; D, 9th ventrite of male; E, posterior part of gonocoxite; F, 9th and 10th
terga of male. Scale 1: 0.1 mm for A; Scale 2: B, D, F for 0.2 mm, E for 0.1 mm; Scale 3: C for 0.2 mm.

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Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

Stenus oisami Naomi & Puthz(Figs. 28A–G, 104B)
Stenus oisami Naomi & Puthz, 1994: 304; Herman, 2001: 2313; Naomi & Puthz, 2013: 143.
Type material examined. Holotype: ♂ (NHMW), Mt. Fuji (2,000–2,300 m), Yamanashi &Shizuoka Prefs., Franz col.
Other material examined. [HONSHU]: 2 ♂2 ♀, Mt. Ryogami, Ryogami Vil., Saitama Pref.,10. v. 1997, M. Maruyama leg.; 3 ♂2 ♀, same locality and date, T. Kishimoto leg.; 2 ♂2 ♀, Sumiyaki-daira (1250 m), Mt. Mitsumine, Ootaki Vil., Saitama Pref., 29. iv. 2001, A. Arai leg.; 2 ♂,Daibosatsu, Yamanashi Pref., 6. vii. 1988, T. Ito leg.; 1 ♂2 ♀, same locality, 26. vi. 1991, T. Itoleg.; 4 ♂2 ♀, Subaru-line, Mt. Fuji, Yamanashi Pref., 1. viii. 1999, S. Naomi leg.; 4 ♂3 ♀,Azami-line, Mt. Fuji, Shizuoka Pref., 2. viii. 1999, S. Naomi leg.
Distribution. Japan: Honshu (Kanto and Chubu districts).
Redescription. Male and female: Body 3.8–4.3 mm (fore body 1.7–2.0 mm) in length,
weakly shining, with antennae moderately long, thin. Head dark brown to black, often withmedian area reddish brown; pronotum and elytra reddish brown; abdomen reddish brown to darkbrown; labrum reddish brown; antennae and legs yellowish brown to reddish brown. Headweakly concave, with a pair of distinct, moderately deep, longitudinal furrows; punctures round,
dense to very dense, small, often with the median area sparsely punctate. Pronotum with surface
uneven, with median longitudinal furrow moderately deep; punctures round, very dense, coarse,
moderately large, subrugose. Elytra with surface strongly uneven, weakly concave near suture;punctures round to elliptical, very dense, moderately large to large, coarse, subrugose. Tarsi eachwith 4th tarsomere strongly bilobed. Abdomen with punctures round, very dense, small, regularin anterior segments, while punctures in posterior segments elliptical, very small, shallow. Lateroventrites and tergoventrite sutures missing.
Male: Sixth ventrite (Fig. 28A) posteromedially with a large, semicircular ﬂat area; 7th ventrite (Fig. 28A) posteromedially with a bell-shaped, ﬂat area; 8th ventrite (Fig. 28A) posteromedially with a moderately large, subtriangular emargination; 9th tergum (Fig. 28C) with antecostal
apophyses very long, thin; 9th ventrite (Fig. 28D) minutely serrate posteriorly, with macrosetae
moderately long, apicolateral teeth acutely pointed, apicolateral setae long; 10th tergum (Fig.
28C) rounded. Aedeagal median lobe (Fig. 28E) broad, distinctly angulate apicolaterally; apicalsclerotized area (Fig. 28C) transverse, broad-subtriangular, with median cusp thick, short,pointed. Endophallic dorsal membrane (Fig. 28E) almost circular, medium-sized; median bands(Fig. 28E) relatively short; lateral bands (Fig. 28E) long; expulsion hooks (Fig. 28G) separated
but connected by the V-shaped thin rod, each with anterior plate triangular, small, much smaller
than and demarcated by a suture from posterior plate, the posterior plate moderately protruding
posterolaterally; copulatory tube (Fig. 28E) with basal chamber small, main tube thick, baculiform but strongly curved near the middle. Parameres (Fig. 28E) each weakly curved laterally
behind the base of apical area; apical part moderately long, mesially swollen and angulate atbase, furnished mesially with 8 to 10 setae at base and also with 17 to 20 setae at about apicalhalf.
Female: Eighth ventrite minutely pointed posteromedially; gonocoxites (Fig. 28F) distinctly
toothed posteriorly, with apicolateral tooth long, acutely pointed, apicolateral setae very long.
Spermatheca (Fig. 28B) with capsule rounded apically, small; RT-duct very long, moderately
thick; duct very long, relatively thin to moderately thick, strongly coiled; basal valve short; basal

The Steninae of Japan Part 2

Fig. 28. Stenus oisami Naomi & Puthz (Fuji, Yamanashi). A, 6th to 8th ventrites of male; B, spermatheca; C, 9th
and 10th terga of male; D, 9th ventrite of male; E, aedeagus; F, posterior part of gonocoxite; G, expulsion
hooks. Scale 1: 0.3 mm for A; Scale 2: C–E for 0.2 mm, B, F, G for 0.1 mm.

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sclerotized duct about as long as basal valve.
Biology and ecology. S. oisami is distributed in the mountainous and high mountainous
regions of central Honshu. The beetles inhabit leaf litter in the natural forests. In Mt. Fuji, they
inhabit the forests of timber-limited regions (about 2,000–2,300 m), together with S. fujimontis
Puthz, 2001 or S. fujiensis Puthz, 2001; and the beetles of S. oisami are common there.
Remarks. S. oisami is probably the sister species of S. biwa, but it is separable from the latter
species by the 6th ventrite of male with the large posteromedian ﬂat area (Fig. 28A), the 9th ventrite of male with its apicolateral teeth longer (Fig. 28D), the aedeagal median lobe cuspidate apically with the longer median cusp (Fig. 28E), and the endophallic explusion hook with its anterior plate pointed (Fig. 28G).
Etymology. The speciﬁc epithet of this species is derived from the name of a sacred music“oisami” for the ancient dance performance at the shrines in Japan.
Stenus biwa Hromádka(Figs. 29A–G, 104C)
Stenus biwa Hromádka, 1980: 113; Herman, 2001: 2094; Naomi & Puthz, 2013: 143.
Type material examined. Holotype: ♂ (cP), Yasumiya, Lake Towada, Aomori Pref., 27. vii.
1954, K. Sawada leg.
Other material examined. [HONSHU]: 2 ♂3 ♀, Towada Lake, Aomori Pref., 4. viii. 1987, S.
Nomura leg.; 1 ♂, Tsuta spa, Towada Lake, Aomori Pref., 6. viii. 1987, S. Nomura leg.; 1 ♂,Oirase, Towada Lake, Aomori Pref., 6. viii. 1987, S. Nomura leg.; 2 ♂2 ♀, Towada Lake,
Aomori Pref., 30. ix 1992, M. Sakai leg.
Distribution. Japan: Honshu (Aomori Pref.).
Redescription. Male and female: Body 3.6–3.8 mm (fore body 1.7–1.9 mm) in length,
weakly to moderately shining, with antennae moderately long, thin. Body orange red to reddish
brown but the inner marginal areas of head and postabdomen more or less infuscate; labrum reddish brown; antennae and legs yellowish brown to reddish brown. Head weakly concave, with apair of longitudinal furrows; punctures round, sparse to dense, small, somewhat umbilicate. Pronotum with surface uneven, with indistinct median longitudinal furrow; punctures round toalmost round, very dense, moderately large, coarse, sometimes two or more punctures partiallyfused. Elytra with surface strongly uneven, weakly concave near suture; punctures round toalmost round, very dense, moderately large to large, coarse, sometimes two or more punctures
partially fused. Tarsi each with 4th tarsomere strongly bilobed. Abdomen with punctures round to
elliptical, dense, small in anterior segments, while punctures in posterior segments very small,sparse to moderately dense, shallow. Lateroventrites and tergoventrite sutures missing.
Male: Seventh ventrite (Fig. 29D) posteromedially with an elongate, bell-shaped, very shallow depression; 8th ventrite (Fig. 29D) posteromedially with a moderately deep, subtriangularemargination; 9th tergum (Fig. 29B) with antecostal apophyses long; 9th ventrite (Fig. 29E) very
minutely serrate posteriorly, with macrosetae short, apicolateral teeth short, pointed, apicolateral
setae short; 10th tergum (Fig. 29B) rounded. Aedeagal median lobe (Fig. 29C) broad, angulate or
weakly projecting apicolaterally, minutely tricuspidate at the apicomedian part; apical sclerotizedarea (Fig. 29C) weakly developed near the middle, with median cusp very small, thin, a little longer than lateral cusps. Endophallic median bands (Fig. 29C) very broad; lateral bands (Fig. 29C)
very thin; expulsion hooks (Fig. 29F) connected at the posteromesial margins of posterior plates,

The Steninae of Japan Part 2

Fig. 29. Stenus biwa Hromádka (A, G, Towada, Aomori; B–F, Tsuta, Aomori). A, spermatheca; B, 9th and 10th
terga of male; C, aedeagus; D, 7th and 8th ventrites of male; E, 9th ventrite of male; F, expulsion hooks; G,posterior part of gonocoxite. Scale 1: 0.1 mm for A; Scale 2: 0.2 mm for B, C, E, 0.1 mm for F, G; Scale 3:
0.3 mm for D.

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Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

each with anterior plate much smaller than and partially demarcated by a suture from posterior
plate, the posterior plate gently rounded posteriorly; copulatory tube (Fig. 29C) long, with maintube thick basally, distinctly narrowed and strongly curved toward apex. Parameres (Fig. 29C)
each weakly turning laterally at the apical area; apical part boot-shaped, moderately long, furnished mesially with a tuft of 4 to 5 setae at base, 2 long setae near the middle, with 7 to 9 setae
at about apical half.
Female: Eighth ventrite minutely pointed posteromedially; gonocoxites (Fig. 29G) toothed
posteriorly, with apicolateral tooth very long, acutely pointed, apicolateral setae very long. Spermatheca (Fig. 29A) with capsule rounded apically, moderately long; RT-duct long, thick; ductvery long, thin but moderately thick at the distal part, irregularly coiled; basal valve short; basal
sclerotized duct about as long as basal valve. Bursa copulatrix (Fig. 29A) disc-shaped, strongly
sclerotized.
Biology and ecology. S. biwa is distributed in the mountainous regions of the northern-mostpart of Honshu. The beetles inhabit leaf litter in the natural forests.
Remarks. S. biwa is probably the sister species of S. oisami, but it is separable from the latter
species by the 6th ventrite of male without modiﬁcation, the 9th ventrite of male with its apicolateral teeth shorter (Fig. 29E), the aedeagal median lobe tricuspidate apicomedially, with its
median cusp smaller (Fig. 29C), and the endophallic explusion hook with its anterior plate obtuse(Fig. 29C).
Etymology. The speciﬁc epithet of this species is derived from the Japanese name of the Japanese lute “biwa”.
Stenus bicara Naomi(Figs. 30A–H, 104D)
Stenus bicara Naomi, 1988: 79; Herman, 2001: 2001; Naomi & Puthz, 2013: 143.
Type material. Holotype: ♀ (KUF), Chuzenji, Nikko, Tochigi Pref., 28–30. vi. 1982, S.
Naomi leg.
Type material examined. Paratypes: 1 ♂1 ♀ (cN), same data as holotype.
Other material examined. [HONSHU]: 2 ♂1 ♀, Iidate Vil., Fukushima Pref., 21. vii. 1985, S.
Nomura leg.; 1 ♂2 ♀, Mt. Oharashi, Tateiwa Vil., Fukushima Pref., 23. vii. 1996, S. Naomi leg.;1 ♂1 ♀, Miyakawa, Hanawa-cho, Fukushima Pref., 24. v. 1998, K. Haga leg.; 3 ♂, Konaka,
Seta-Azuma Vil., Gunma Pref., 11. viii. 2004, T. Watanabe leg.; 3 ♂3 ♀, Marunuma, Katashina
Vil., Gunma Pref., 29–30. iv. 1991. T. Ito leg.; 1 ♂2 ♀, Hoshi Spa, Niiharu Vil., Gunma Pref., 26.
vi. 1997, S. Naomi leg.; 1 ♂, Mikuni Pass, Niiharu Vil., Gunma Pref., 19–20. viii. 1998, K. Ishii
leg.; 1 ♂, Sawairi, Higashi Vil., Seta-gun, Gunma Pref., 22. iv. 2003, N. Kanai leg.; 1 ♂1 ♀,Chuzenji, Nikko, Tochigi Pref., 24. vii. 1985, S. Nomura leg.; 3 ♂2 ♀, Yumoto, Oku-Nikko,
Tochigi Pref., 23–25. vii. 1985, S. Nomura leg.
Distribution. Japan: Honshu (Tohoku and Kanto districts).
Redescription. Male and female: Body 3.0–3.7 mm (fore body 1.5–1.8 mm) in length,
weakly shining, with antennae moderately long, thin. Body orange red to reddish brown but the
inner marginal areas of head and postabdomen infuscate; labrum reddish brown; antennae andlegs yellowish brown to reddish brown. Head weakly concave, with a pair of longitudinal furrows; punctures round, moderately dense to dense, small, somewhat umbilicate. Pronotum withsurface strongly uneven, with indistinct long median longitudinal furrow, paired basilateral lon-

The Steninae of Japan Part 2

Fig. 30. Stenus bicara Naomi (A, Sawairi, Gunma; B, F, H, Chuzenji, Tochigi; C–E, G, Yumoto, Tochigi). A,
copulatory tube; B, spermatheca; C, 9th and 10th terga of male; D, basal part of spermatheca; E, 7th and 8th
ventrites of male; F, posterior part of gonocoxite; G, 9th ventrite of male; H, aedeagus. Scale 1: 0.1 mm for A,
B, D, F, 0.2 mm for C, G, H; Scale 2: E for 0.3 mm.

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Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

gitudinal keels, and with an indistinct fovea between the median longitudinal furrow and basilateral longitudinal keel; punctures round to almost round, very dense, moderately large, coarse,
sometimes subrugose. Elytra with surface strongly uneven, weakly concave near suture; punctures round to elliptical, very dense, various in size but moderately large in average, coarse,
sometimes two or more punctures partially fused. Tarsi each with 4th tarsomere strongly bilobed.
Abdomen with punctures round to elliptical, dense to very dense, small in anterior segments,
while punctures in posterior segments very small, shallow, sometimes faint, almost equal to thesockets of setae. Lateroventrites and tergoventrite sutures missing.
Male: Seventh ventrite (Fig. 30E) medially with an elongate, bell-shaped, very shallow
depression, which is very shallow emarginate; 8th ventrite (Fig. 30E) posteromedially with amoderately large, subtriangular emargination; 9th tergum (Fig. 30C) with antecostal apophyses
moderately long; 9th ventrite (Fig. 30G) very minutely serrate posteriorly, with macrosetae long,apicolateral teeth thin, acutely pointed, apicolateral setae long; 10th tergum (Fig. 30C) rounded.
Aedeagal median lobe (Fig. 30H) moderately broad, angulate apicolaterally; apical sclerotizedarea (Fig. 30C) weakly developed, with median cusp small, pointed, lateral cusps each existing
as a weak angulation. Endophallic median bands (Fig. 30H) long, broad; lateral bands (Fig. 30H)
very thin; expulsion hooks (Fig. 30H) connected at the posteromesial corners, each hook curved
laterally at anterior part, acutely pointed and projectiong at posterolateral part; copulatory tube
(Fig. 30A) long, main tube thick, very acutely pointed at apex, with ventral processes closed ventrally, acutely pointed at apex (Fig. 30A) or opened ventrally (Fig. 30H). Parameres (Fig. 30H)
each turning laterally at the apical area; apical area moderately long, swollen mesially at base,furnished mesially with 19 to 23 short and 2 long setae.
Female: Eighth ventrite minutely pointed posteromedially; gonocoxites (Fig. 30F) toothed
posteriorly, with apicolateral tooth long, acutely pointed, apicolateral setae very long. Spermatheca (Fig. 30B) with capsule rounded apically, very short; RT-duct very long, moderately thickto thick; duct long, relatively thin to moderately thick, irregularly coiled; basal valve short; basal
sclerotized duct short (Fig. 30B) or long (Fig. 30D), consisting of the distal thicker part and theproximal thinner part. Bursa copulatrix saucer-shaped (Fig. 30B) or broad-conical (Fig. 30D).
Biology and ecology. S. bicara is distributed in the high mountainous regions. The beetles
inhabit leaf litter in the natural forests.
Remarks. S. bicara is allied to S. araiorum, but it is separable from the latter species by theendophallic copulatory tube with its apical tube attenuate and very acutely pointed at apex (Fig.
30A, H), and the spermatheca with its capsule much smaller (Fig. 30B).
S. bicara is a polytypic species; and the infraspeciﬁc variations are found in the apex of
aedeagal median lobe, the anterior and posterior parts of endophallic expulsion hooks, and the
copulatory tube. Out of them, the copulatory tubes highly vary in structure; and their structures
are different from one locality to another. For example, the main tube (of copulatory tube) is
closed ventrally, with its apical tube very long and very acutely pointed in the beetles of Sawairi(Fig. 30A), or open ventrally, with its apical tube moderately long and acutely pointed in the beetles of Oku-Nikko (Fig. 30H).
Etymology. The speciﬁc epithet of this species is derived from the name of god “Bicara”,
which appears in the Japanese ancient mythology.

The Steninae of Japan Part 2

77

Stenus araiorum Naomi(Figs. 31A–I, 104E)
Stenus araiorum Naomi, 2015: 22.
Type material examined. Holotype: ♂ (CBM), Kitamuki-Jizo, Moroyama, Saitama Pref., 11.
x. 1998, S. Arai leg. Paratypes: 3 ♂ (cN), same data as holotype.
Other material examined. [HONSHU]: 3 ♂5 ♀, Mt. Takao, Tokyo, 11. viii. 1990, T. Ito leg.;1 ♂2 ♀, Fudago, Mt. Kiyosumi, Kimitsu City, Chiba Pref., 18. vii. 1991, S. Naomi leg.; 4 ♂,Kaisho, Mt. Kiyosumi, Ootaki-cho, Chiba Pref., 19. vii. 1991, S. Naomi leg.; 1 ♂2 ♀, Mt. Kiyosumi, Amatsu-Kominato, Chiba Pref., 27. iv. 1997, S. Naomi leg.; 1 ♂, Komatsu Shrine, Chikura-machi, Chiba Pref., 26. vi. 1994, S. Naomi leg.; 1 ♂4 ♀, Chikura-machi, Chiba Pref., 26. vi.
1994, S. Naomi leg.; 4 ♂2 ♀, Utogi, Futtu City, Chiba Pref., 3. v. 1996, S. Naomi leg.; 2 ♂1 ♀,Mt. Takago, Kimitsu City, Chiba Pref., 5. v. 1996, S. Naomi leg.; 1 ♂2 ♀, Umegase Valley, Mt.
Daifuku, Chiba Pref., 6. v. 1998, S. Naomi leg.; 1 ♂1 ♀, Kasamori, Chonan-machi, Chiba Pref.,12. iv. 1997, S. Naomi leg.
Distribution. Japan: Honshu (Kanto district).
Redescription. Male and female: Body 3.3–3.6 mm (fore body 1.6–1.8 mm) in length, elongate, weakly shining, with antennae moderately long, thin. Body bright reddish brown but the
inner marginal areas of head and abdomen infuscate; labrum, antennae and legs yellowish brown
to reddish brown. Head with a pair of shallow longitudinal furrows; punctures round, moderately
dense to dense, small. Pronotum with surface slightly uneven, with indistinct median longitudinal furrow; punctures round, very dense, moderately large, coarse. Elytra with surface slightly
uneven; punctures round, very dense, moderately large. Tarsi each with 4th tarsomere strongly
bilobed. Abdomen with punctures round, moderately dense, small in anterior segments, while
punctures in posterior segments very small, regular. Lateroventrites and tergoventrite sutures
missing.
Male: Seventh ventrite posteromedially with or without a semicircular ﬂat area; 8th ventrite(Fig. 31H) posteromedially with an arcuate, moderately large emargination; 9th tergum (Fig.
31B) with antecostal apophyses very long; 9th ventrite (Fig. 31E) indistinctly serrate posteriorly,
with apicolateral teeth pointed, apicolateral setae short; 10th tergum (Fig. 31B) rounded posteriorly. Aedeagal median lobe (Fig. 31A) broad, distinctly angulate apicolaterally, tricuspidate atapicomedian part; apical sclerotized area (Fig. 31A) weakly developed at the middle, withmedian cusp long, pointed, lateral cusps each small, short, pointed. Endophallic median bands(Fig. 31A) each moderately long, broad; lateral bands (Fig. 31A) each long, very thin; expulsion
hooks (Fig. 31G) separated, each boot-shaped, protruding posterolaterally, with anterior platefused with posterior plate; copulatory tube (Fig. 31C) very large, robust, basal chamber ovoidal,
main tube with basal tube thick, apical tube attenuate but distinctly spiralling 3 times, with a subtransparent ﬂap at the right side of middle part. Parameres (Fig. 31A) each weakly turning laterally at the apical area; apical area moderately long, swollen mesially at base, furnished mesiallywith 15 to 17 setae, several ones of which are decumbent anteriorly.
Female: Eighth ventrite minutely pointed posteromedially; gonocoxites (Fig. 31I) toothed
posteriorly, with apicolateral tooth long, acutely pointed, apicolateral setae very long. Spermatheca (Fig. 31D) with capsule rounded apically, very long; RT-duct moderately long and thick;spermathecal duct very long, rather thin but moderately thick at its distal part, irregularly coiled;basal valve short; basal sclerotized duct moderately long, consisting of the distal and proximal

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Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

Fig. 31. Stenus araiorum Naomi (A–C, E, G, H, Kitamuki, Saitama; D, F, I, Utogi, Chiba). A, aedeagus; B, 9th
and 10th terga of male; C, copulatory tube; D, spermatheca; E, 9th ventrite of male; F, 8th ventrite of female;G, expulsion hooks; H, posterior part of 8th ventrite of male; I, posterior part of gonocoxite. Scale 1: 0.2 mm
for A, B, E, 0.1 mm for C, G, I; Scale 2: 0.1 mm for D; Scale 3: 0.3 mm for F, H.

The Steninae of Japan Part 2

79

portions; basal structure subconical, emarginate basimedially.
Biology and ecology. S. araiorum is distributed in the plains and low mountainous regions of
the Kanto district, central Honshu. The beetles inhabit leaf litter in the natural forests.
Remarks. S. araiorum is allied to S. bicara, but it is separable from the latter species by theendophallic copulatory tube with its apical tube distinctly spiralling three times (Fig. 31C), andthe spermatheca with its capsule much larger (Fig. 31D). In S. araiorum, there is an infraspeciﬁcvariation regarding the shape of the apical part of aedeagal median lobe. It is usually tricuspidate
as in Fig. 29A, but it is simply pointed in a local population of Mt. Takao, Tokyo.
Etymology. This species is named in honor of Mr. Koji Arai and Mrs. Shiho Arai (Ranzan,
Saitama), who studies Staphylinidae.
Stenus jurojin Naomi(Figs. 32A–H, 104F)
Stenus jurojin Naomi, 2004: 108; Naomi & Puthz, 2013: 143.
Type material examined. Holotype: ♂ (CBM), Mt. Nantai, Nikko, Tochigi Pref., 28. v. 1994,
Y. Hagino leg. Paratype: 1 ♀ (cN), same data as holotype.
Other material examined. [HONSHU]: 1 ♂, Yokokawa, Hara-machi, Fukushima Pref., 22. v.
1999, K. Haga leg.; 4 ♂, Mt. Tsukiore, Daigo-machi, Ibaraki Pref., 1. xii. 1995, S. Nomura leg.
Distribution. Japan: Honshu (Tohoku and Kanto districts).
Redescription. Male and female: Body 3.5–4.0 mm (fore body 1.6–1.8 mm) in length, moderately shining, with antennae moderately long, thin. Body reddish brown but the inner marginalareas of head and abdomen infuscate; labrum, antennae and legs yellowish brown to reddish
brown. Head weakly concave, with a pair of shallow longitudinal furrows; punctures round,moderately dense, small. Pronotum with surface uneven, with indistinct median longitudinal furrow; punctures round to almost round, very dense, moderately large, coarse. Elytra with surface
uneven, weakly depressed near suture; punctures round to elliptical, very dense, various in size
but moderately large in average, coarse. Tarsi each with 4th tarsomere strongly bilobed. Abdomen with punctures round to elliptical, dense, small in anterior segments, while punctures in posterior segments sparse and very small, or existing simply as setal sockets. Lateroventrites and tergoventral sutures missing.
Male: Sixth ventrite (Fig. 32C) posteromedially with a semicircular ﬂat area; 7th ventrite(Fig. 32C) posteromedially with a semicircular, very shallow depression; 8th ventrite (Fig. 32C)
posteriorly with a broad-subtriangular emargination; 9th tergum (Fig. 32A) with antecostal
apophyses very long; 9th ventrite (Fig. 32F) very minutely serrate posteriorly, with macrosetae
short, apicolateral teeth short, acutely pointed, apicolateral setae short; 10th tergum (Fig. 32A)
rounded posteriorly. Aedeagal median lobe (Fig. 32D) broad, distinctly angulate apicolaterally,minutely tricuspidate at apicomedial part; apical sclerotized area (Fig. 32D) short, weakly protruding apicomedially. Endophallic median bands (Fig. 32D) very broad, moderately long; lateralbands (Fig. 32D) each long, weakly broadened anteriorly; expulsion hooks (Fig. 32H) each withanterior plate pointed anteriorly, demarcated by a suture from posterior plate, the posterior plate
deeply emarginate laterally, posterolaterally with 1 or 2 small, pointed teeth; copulatory tube
(Fig. 32D, E) large, main tube robust, the basal tube thick with paired lateral processes connectedapically to form an arched sclerotized band, and also with a thin, subtransparent plate between
the lateral processes, the apical tube very thin, attenuate, pointed, with (Fig. 32E) or without

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Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

Fig. 32. Stenus jyurojin Naomi (A, C, E, H, Tsukiore, Ibaraki; B, D, F, G, Nantai, Tochigi). A, 9th and 10th tergaof male; B, spermatheca; C, 6th to 8th ventrites of male; D, aedeagus; E, copulatory tube (dorsal view); F, 9th
ventrite of male; G, posterior part of gonocoxite; H, expulsion hooks. Scale 1: 0.2 mm for A, D, F, 0.1 mm for
B, E, G, H; Scale 2: 0.3 mm for C.

The Steninae of Japan Part 2

81(Fig. 32D) a lateral subtransparent ﬂap. Parameres (Fig. 32D) thick, each weakly turning laterally at the apical area; apical area swollen mesially at base, furnished mesially with 16 to 17
setae, several setae of which are decumbent anteriorly.
Female: Eighth ventrite weakly pointed posteromedially; gonocoxites (Fig. 32G) toothed
posteriorly, each with apicolateral tooth acutely pointed, apicolateral setae very long. Spermatheca (Fig. 32B) very stout, with capsule very large, subconical; RT-duct very large, thick; duct
moderately long and thick, coiled; basal valve short; basal sclerotized duct about 2 times as longas basal valve. Basal structure (Fig. 32B) large, conical, membranous.
Biology and ecology. S. jurojin is distributed in the low to high mountainous regions. The
beetles inhabit leaf litter in the natural forests.
Remarks. S. jurojin is allied to S. tsukubamontis, but it is separable from the latter species by
the aedeagal median lobe tricuspidate at the apicomedial part (Fig. Fig. 32D), the endophallic
copulatory tube with its basal tube having the shorter lateral processes (Fig. 32E), and the spermatheca with its RT-duct much thicker, and its surface almost smooth (Fig. 32B).
S. jurojin is a polytypic species; and the infraspeciﬁc variations are found in the aedeagal
endophallic structures as follows: Regarding the expulsion hook, the anterior plate usually moreor less turns laterally and the posterior plate is simply pointed at the posterolateral corners (Fig.
32D). However, the anterior plate simply turns anteriorly and the posterior plate is bi-toothed at
the posterolateral corners (Fig. 32H) in some males of Tsukiore. Regarding the copulatory tube,
the main tube in the male of Nantai (Fig. 32D) is thicker and shorter than in the male of Tsukiore(Fig. 32E). Furthermore, the lateral process of basal tube in the male of Yokokawa is a little
larger than in the males of Nantai and Tsukiore.
Etymology. The speciﬁc epithet of this species is derived from the name of one of the Seven
Gods of Good Fortune “Jurojin”, which appears in the Japanese ancient mythology.
Stenus tsukubamontis Naomi, Nomura & Kamezawa(Figs. 33A–H, 104G)
Stenus tsukubamontis Naomi, Nomura & Kamezawa, 2015: 320.
Type material examined. Holotype: ♂ (NMNST), Mt. Tsukuba, Ibaraki Pref., 10. ix. 1991, T.
Ito leg. Paratypes: 4 ♂7 ♀, same data as holotype; 4 ♂6 ♀ (NMNST) & 3 ♂3 ♀ (cN), Mt. Ashio,
Makabe-machi, Ibaraki Pref., 11. xii. 1997, S. Nomura leg.
Distribution. Japan: Honshu (Ibaraki Pref.).
Redescription. Male and female: Body 3.7–4.3 mm (fore body 1.6–1.8 mm) in length,
weakly to moderately shining, with antennae moderately long. Body yellowish brown to reddish
brown, but the inner marginal areas of head more or less infuscate; labrum, antennae and legs
yellowish brown to reddish brown. Head weakly concave, with a pair of shallow longitudinalfurrows; punctures round, moderately dense, small. Pronotum with surface weakly uneven, withindistinct median longitudinal furrow; punctures round, very dense, moderately large, somewhat
irregular. Elytra with surface weakly uneven; punctures round to elliptical, very dense, large,coarse. Tarsi each with 4th tarsomere strongly bilobed. Abdomen with punctures round, moderately dense, small, regular in anterior segments, while punctures in posterior segments extremely
small, sparse. Lateroventrites and tergoventral sutures missing.
Male: Sixth ventrite (Fig. 33H) posteromedially with a semicircular ﬂat area; 7th ventrite(Fig.33H) posteromedially with a semicircular ﬂat area, which is a little smaller than that on 6th

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Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

Fig. 33. Stenus tsukubamontis Naomi, Nomura & Kamezawa (Tsukuba, Ibaraki). A, 9th and 10th terga of male;B, aedeagus; C, 9th ventrite of male; D, copulatory tube; E, posterior part of gonocoxite; F, spermatheca; G,posterior part of 8th ventrite of male; H, 6th and 7th ventrites of male. Scale 1: 0.2 mm for A-C, G and
0.1 mm for D-E; scale 2: 0.1 mm for F; and scale 3: 0.3 mm for H.

The Steninae of Japan Part 2

83

ventrite; 8th ventrite (Fig. 33G) posteromedially with an arcuate, moderately large and deep
emargination; 9th tergum (Fig. 33A) with antecostal apophyses long; 9th ventrite (Fig. 33C)
hardly serrate posteriorly, with macrosetae short, apicolateral teeth short, acutely pointed, apicolateral setae short; 10th tergum (Fig. 33A) rounded posteriorly. Aedeagal median lobe (Fig. 33B)
broad, distinctly angulate apicolaterally, acutely pointed at apex; apical sclerotized area (Fig.
33B) weakly developed. Endophallic median bands (Fig. 33B) moderately long, very broad;
expulsion hooks (Fig. 33B) broadly contiguous by the posteromesial margins, each rounded anteriorly, pointed posterolaterally, truncate posteriorly; copulatory tube (Fig. 33B, D) moderately
long, with basal chamber elongate-ovoidal, with two shafts of same length, main tube attenuate
but weakly curved, acutely pointed, with two long, thin lateral processes connected by the subtransparent plate. Parameres (Fig. 33B) thick, each weakly turning laterally at the apical area;
apical area swollen mesially to form its submembranous area, furnished mesially with 20 to 22
setae, several setae of which are decumbent anteriorly.
Female: Eighth ventrite weakly pointed posteromedially; gonocoxites (Fig. 33E) toothed
posteriorly, each with apicolateral tooth acutely pointed, apicolateral setae very long. Spermatheca (Fig. 33F) with capsule missing; RT-duct very long, moderately thick, surface sporadicallywith small, ovoidal or elongate-ovoidal tubercles which exist almost transversely along the transverse ductal stripes; duct short, moderately thick, tightly coiled with 6 turns; basal valve long;
basal sclerotized area not observable. Basal structure (Fig. 33F) subconical, membranous, distally with the sclerotized area almost W-shaped at posterior part.
Biology and ecology. S. tsukubamontis is distributed only in Mt. Tsukuba and its neighboringareas of the Kanto district, central Honshu. The beetles inhabit leaf litter in the natural forests. In
Mt. Tsukuba, the beetles of S. tsukubamontis inhabit the leaf litter together with those of S. asyura in the same Fagus-forests developed around the summit.
Remarks. S. tsukubamontis is allied to S. jurojin, but it is separable from the latter species by
the aedeagal median lobe simply pointed at the apicomedial part (Fig. 33B), the endophallic copulatory tube with its basal tube having the longer lateral processes (Fig. 33D), and the spermatheca with its RT-duct much thinner, and its surface sporadically covered with small, ovoidal or
elongate-ovoidal tubercles (Fig. 33F).
Stenus santira Naomi(Figs. 34A–J, 104H)
Stenus santira Naomi, 1988: 78; Herman, 2001: 2378; Naomi & Puthz, 2013: 143.
Stenus tengu Hromádka, 1990: 57.
Type material. Holotype of S. santira: ♂ (KUF), Mt. Zao, Miyagi Pref., 25. vi. 1983, S.
Nomura leg.
Holotype of S. tengu: ♂ (AACO), Bijyo-daira (1000 m), Toyama Pref., 28. vii. 1980, A & Z.
Smetana leg.
Type material examined. Paratype: 1 ♂ (cN), Mt. Chokai, Yamagata Pref., 5. vii. 1985, S.
Nomura leg.
Other material examined. [HONSHU]: 1 ♂2 ♀, Futakuchi Valley, Miyagi Pref., 12. vii.
1985, S. Nomura leg.; 2 ♂, Mt. Zao, Miyagi Pref., 25. vi. 1983, S. Nomura leg.; 1 ♂1 ♀, samedata as holotype; 1 ♂2 ♀, Nakatsugawa, Mt. Azuma, Fukushima Pref., 19. viii. 1996, S. Naomi
leg.; 3 ♂, Makugawa Spa, Fukushima Pref., 19. vii. 1985, S. Nomura leg.; 2 ♂1 ♀, Arakawa,

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Sanpoku-machi, Niigata Pref., 5. vii. 1985, S. Nomura leg.; 1 ♂, Tainai, Niigata Pref., 3. vii.
1985, S. Nomura leg.
Distribution. Japan: Honshu (Tohoku and Chubu districts).
Redescription. Male and female: Body 3.5–3.7 mm (fore body 1.7–2.0 mm) in length,
weakly shining, antennae relatively short, thin. Head black, with median longitudinal area reddish brown; pronotum and elytra reddish brown; abdomen dark reddish brown, often with theposterior segments almost black; antennae and legs yellowish brown to reddish brown. Headweakly convex, with a pair of longitudinal furrows; punctures round to almost round, moderately
dense to dense, small. Pronotum with surface uneven, with indistinct median longitudinal furrow; punctures round, very dense, various in size, moderately large, coarse. Elytra with surface
uneven, weakly depressed near suture; punctures round to elliptical, very dense, moderately
large, coarse. Tarsi each with 4th tarsomere bilobed. Abdomen with punctures round to elliptical,
moderately dense, small in anterior segments, while punctures in posterior segments very small,sparse, regular. Lateroventrites and tergoventrite sutures missing.
Male: Sixth ventrite (Fig. 34F) posteromedially with a bell-shaped ﬂat area; 7th ventrite (Fig.
34F) posteromedially with a shallow, subelliptical depression; 8th ventrite (Fig. 34F) posteriorly
with a subtriangular, relatively large emargination; 9th tergum (Fig. 34G) with antecostal apophyses very long; 9th ventrite (Fig. 34C) minutely serrate posteriorly, with macrosetae moderately
long, apicolateral teeth acutely pointed, apicolateral setae long; 10th tergum (Fig. 34G) rounded
posteriorly. Aedeagal median lobe (Fig. 34A) moderately broad, distinctly angulate apicolaterally, tricuspidate at apex; apical sclerotized area (Fig. 34A) transverse, short, with median cusp
long, thin, pointed, lateral cusps each existing as obtuse angulation. Endophallic median bands(Fig. 34A) moderately long; lateral bands (Fig. 34A) long, thin; expulsion hooks (Fig. 34A, E)
moderately large, partially fused at the mesial sides of posterior plates, each with the anterior
plate pointed at anterior tip, partially fused with posterior plate, the posterior plate nearly rectangular, weakly emarginate posteriorly; copulatory tube (Fig. 34A, H–J) varied in structure (especially in its apical part), with basal chamber subovoidal (Fig. 34J) or parallel-sided (Fig. 34I),
main tube baculiform, weakly swollen (Fig. 34H) or moderately curved (Fig. 34I, J) behind the
middle, with the apical-most part strongly narrowed apically and curved to various degrees (Fig.
34H–J). Parameres (Fig. 34A) each very long; apical area very large, somewhat fusiform, having
the developed dorsal ﬂap, furnished mesially with 23 to 28 setae of various lengths, two setae of
which are very long.
Female: Eighth ventrite weakly pointed posteromedially; gonocoxites (Fig. 34D) each
toothed posteriorly, with apicolateral tooth very long, acutely pointed, apicolateral setae very
long. Spermatheca (Fig. 34B) with capsule missing; RT-duct moderately long, thick; duct relatively thin to moderately thick, loosely coiled; gland ovoidal, with its opening located on the ducta little proximal from the 2nd turn from the apex; basal valve short; basal sclerotized duct long,
basally wrapped with membrane. Bursa copulatrix (Fig. 34B) sclerotized, saucer-shaped, arcuately bi-emarginate at base.
Biology and ecology. S. santira is widely distributed in the mountainous regions of central tonorthern Honshu. The beetles inhabit leaf litter in the natural forests.
Remarks. S. santira is allied to S. ellipsoides, but it is separable from the latter species by theaedeagal median lobe with its apical sclerotized area shorter (Fig. 34A), the paramere longer(Fig. 34A), and the endophallic copulatory tube longer, with the main tube having the apex
strongly narrowed and more or less curved (Fig. 34A, H–J).
S. santira is a polytypic species; and it shows the geographical variations regarding various

The Steninae of Japan Part 2

Fig. 34. Stenus santira Naomi (A, C, E, F, H, Zao, Miyagi; B, D, Futakuchi, Miyagi; G, Nakatsugawa, Fukushima; I, Tainai, Niigata; J, Chokai, Yamagata). A, aedeagus; B, spermatheca; C, 9th ventrite of male; D, posterior part of gonocoxite; E, expulsion hooks; F, 6th to 8th ventrites of male; G, 9th and 10th terga of male;
H–J, copulatory tube. Scale 1: 0.2 mm for A, C, 0.1 mm for D, E; Scale 2: 0.1 mm for B, H–J, 0.2 mm for G;
Scale 3: 0.3 mm for F.

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Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

parts of the endophallic expulsion hooks and the copulatory tube. The expulsion hook is usuallyformed as in Fig. 34E, but in some cases the anterior plate is not angulate laterally and the posterior plate has posteriorly a much larger emargination. The copulatory tube varies regarding theshape of basal chamber, the length of main tube, the degree of the curvature of main tube, andthe shape of the apical-most part, as illustrated in Fig. 34A, H (Zao, Miyagi), Fig. 34J (Chokai,
Yamagata) and Fig. 34I (Tainai, Niigata).
Etymology. The speciﬁc epithet of this species is derived from the name of god “Santira”,
which appears in the Japanese ancient mythology.
Stenus ellipsoides Naomi(Figs. 35A–F, 104I)
Stenus ellipsoides Naomi, 2015: 24.
Type material examined. Holotype: ♂ (CBM), Futamata, Mt. Asahi, Yamagata Pref., 21. viii.
1996, S. Naomi leg. Paratypes, 3 ♂1 ♀ (cN), same data as holotype; 1 ♂ (cN), Hosono, Urabandai, Fukushima Pref., 9. vii. 1985, S. Nomura leg.
Distribution. Japan: Honshu (Yamagata and Fukushima Prefs.).
Redescription. Male and female: Body 3.5–3.7 mm (fore body 1.7–1.8 mm) in length,
weakly shining. Body entirely yellowish brown to reddish brown, but apical segments of antennae and lateral areas of vertex infuscate. Head weakly convex, with a pair of longitudinal furrows; punctures round to elliptical, moderately dense to dense, small. Pronotum with surface
slightly uneven, with indistinct median longitudinal furrow; punctures round to elliptical, very
dense, various in size, irregular. Elytra with surface slightly uneven, almost ﬂat near suture;punctures round, very dense, moderately large. Legs with femora moderately thick; tarsi eachwith 4th tarsomere bilobed. Abdomen with punctures round to elliptical, moderately dense, small
to moderately large in anterior segments, while punctures in posterior segments very small, regular. Lateroventrites and tergoventrite sutures missing.
Male: Sixth ventrite (Fig. 35C) posteromedially with a bell-shaped ﬂat area; 7th ventrite(Fig. 35C) medially with a very large, shallow, broad depression, which is weakly, arcuately
emarginate; 8th ventrite (Fig. 35D) posteriorly with a large emargination; 9th tergum with antecostal apophyses long; 9th ventrite minutely serrate posteriorly, with macrosetae moderately
long, apicolateral teeth short, acutely pointed, apicolateral setae long; 10th tergum entire. Aedeagal median lobe (Fig. 35B) large, broad, angulate apicolaterally, tricuspidate at apex; apical sclerotized area (Fig. 35B) transverse, with median cusp very long, thin, pointed, lateral cusps eachobtusely pointed, broad. Endophallic median bands (Fig. 35B) each moderately long, very broadat base; lateral bands (Fig. 35B) long, very thin; expulsion hooks (Fig. 35B) large, each almost
C-shaped, pointed at anterior tip, with anterior plate fused with posterior plate; copulatory tube
(Fig. 35B) with basal chamber elongate-ovoidal, main tube almost straight, attenuate but ellipsoidal at apex. Parameres (Fig. 35B) each short to moderately long; apical area short, broadened
apically, subtransparent in the median longitudinal area, furnished mesially with 21 to 23 setae ofvarious lengths, two setae of which are very long (Fig. 35G).
Female: Eighth ventrite (Fig. 35E) weakly pointed posteromedially; gonocoxites (Fig. 35F)
each minutely toothed posteriorly, with apicolateral tooth large, acutely pointed, apicolateral
setae moderately long. Spermatheca (Fig. 35A) with capsule long, rounded apically; RT-duct
long, thick; duct moderately thick, loosely coiled; gland subovoidal, broader than long. Bursa

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87

Fig. 35. Stenus ellipsoides Naomi (Asahi, Yamagata). A, anterior part of sprmatheca; B, aedeagus; C, 6th and 7th
venters of male; D, posterior part of 8th ventrite of male; E, posterior part of 8th ventrite of female; F, gonocoxite of female; G, posterior part of paramere; H, bursa copulatrix. Scale 1: 0.1 mm for A, H, 0.2 mm for B,
D–G; Scale 2: 0.3 mm for C.

copulatrix (Fig. 35H) large, saucer-shaped, sclerotized.
Biology and ecology. S. ellipsoides is distributed in the mountainous regions of Tohoku district, Honshu. The beetles inhabit leaf litter in the natural forests.
Remarks. S. ellipsoides is allied to S. santira, but it is separable from the latter species by theaedeagal median lobe with its apical sclerotized area longer (Fig. 35B), the paramere shorter (Fig.
35B) and the endophallic copulatory tube shorter, with its main tube ellipsoidal at apex (Fig. 35B).

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Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

Stenus protuberans Naomi & Watanabe(Fig. 36A–G)
Stenus protuberans Naomi & Watanabe, 2015: 101.
Type material examined. Holotype: ♂ (TUAA), Mt. Ohasahi, Mts. Asahi, Yamagata Pref., 24.
viii. 1994, Y. Watanabe leg. Paratype: ♀ (TUAA), same data as holotype.
Distribution. Japan: Honshu (Yamagata Pref.).
Redescription. Male and female: Body 3.7–4.0 mm (fore body 1.7–1.9 mm) in length,
weakly shining. Body entirely reddish brown but apical segments of antennae and lateral areas ofvertex more or less infuscate. Head with a pair of longitudinal furrows; punctures round, moderately dense, regular, somewhat umbilicate. Pronotum with surface uneven, with indistinct medianlongitudinal furrow; punctures very dense, coarse, irregular. Elytra with surface uneven; punctures very dense, coarse, irregular. Tarsi each with 4th tarsomere strongly bilobed. Abdomen with
punctures round to elliptical, dense, various in size in anterior segments, while punctures in posterior segments small to very small, regular. Lateroventrites and tergoventrite sutures missing.
Male: Sixth ventrite posteromedially with a semicircular, very shallow depression, which isshallowly emarginate; 7th ventrite medially with a shallow, longitudinal depression, which isshallowly emarginate; 8th ventrite (Fig. 36F) posteriorly with a very large, V-shaped emargination; 9th tergum (Fig. 36A) with antecostal apophyses very long; 9th ventrite (Fig. 36D) very
minutely serrate posteriorly, with macrosetae short, apicolateral teeth pointed, apicolateral setae
moderately long; 10th tergum (Fig. 36A) entire. Aedeagal median lobe (Fig. 36E) moderately
broad, obtusely angulate apicolaterally, tricuspidate at apicomedian part; apical sclerotized area
(Fig. 36E) very short, with median cusp thin, pointed, lateral cusps each obtuse, broad. Endophallic median bands (Fig. 36E) each moderately long, very broad at base; expulsion hooks (Fig.
36E) large, connected by the posteromesial corners, each pointed at anterior tip, with anterior
plate almost completely fused with posterior plate; copulatory tube (Fig. 36C) baculiform, very
thick, main tube broadly open ventrally, with a large, vessel-like structure at apex, which has thepaired, thin, apical processes. Parameres (Fig. 36E) each very long, robust, moderately thick,almost straight; apical area very long, weakly broadened toward apex, obliquely truncate apically, furnished mesially with 23–24 setae of various length, two setae of which are very long.
Female: Eighth ventrite minutely pointed posteromedially; gonocoxites (Fig. 36G) eachirregularly toothed posteriorly, with apicolateral tooth acutely pointed. Spermatheca (Fig. 36B)
with capsule long; RT-duct moderately long, thick; duct moderately long, relatively thin, loosely
coiled with 6 turns; gland small, nearly spherical, located on the tube between 5th and 6th turns;
basal valve very long; basal sclerotized duct short, distinctly narrowed basally. Bursa copulatrix(Fig. 36B) saucer-shaped, sclerotized, anteromesially with a pair of small swells.
Biology and ecology. S. protuberans is a rare species; and it is only once collected from Mts.
Asahi of Tohoku district, Honshu. The beetle inhabits leaf litter in the natural forests.
Remarks. S. protuberans is a remarkable species in having the very thick copulatory tube
with its main tube vessel-like at apex (Fig. 36C). There are no other species of asyura-subg.
which possess such peculiar copulatory tube as this. S. protuberans is allied to S. santira and S.
ellipsoides, but it is easily separable from the latter two species by the vessel-like apex of copulatory tube (Fig. 36C).

The Steninae of Japan Part 2

Fig. 36. Stenus protuberans Naomi & Watanabe (Ohasahi, Yamagata). A, 9th and 10th terga of male; B, spermatheca; C, copulatory tube; D, 9th ventrite of male; E, aedeagus; F, posterior part of 8th ventrite of male; G,posterior half of gonocoxite. Scale 1: 0.2 mm for A, D–G and 0.1 mm for B, C.

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Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

Stenus fulvivestis Naomi & Watanabe(Figs. 37A–F, 104J)
Stenus fulvivestis Naomi & Watanabe, 2015: 101.
Type material examined. Holotype: ♂ (TUAA), Jinmuji, Yokosuka City, Kanagawa Pref., 29.
xii. 1990, T. Nonaka leg. Paratypes: 1 ♂ (TUAA), same data as holotype; 1 ♂ (cN), same locality, 13. vi. 1992, T. Nonaka leg.
Distribution. Japan: Honshu (Kanagawa Pref.).
Redescription. Male: Body 3.7–4.0 mm (fore body 1.7–1.8 mm) in length, weakly shining,with antennae long, thin. Body yellowish brown to reddish brown, but lateral areas of vertex andapical segments of antennae more or less infuscate. Head shallowly concave, with a pair of longitudinal furrows; punctures round, moderately dense, small, umbilicate. Pronotum with surface
weakly uneven, with indistinct median longitudinal furrow; punctures round, very dense, moderately large, irregular. Elytra with surface weakly uneven; punctures round to elliptical, very
dense, large, coarse. Tarsi each with 4th tarsomere strongly bilobed. Abdomen with punctures on
3rd segment round, moderately dense, small, regular; punctures becoming gradually smallerfrom anterior to posterior segments. Lateroventrites and tergoventrite sutures missing.
Seventh ventrite (Fig. 37D) posteromedially with a large, semicircular ﬂat area; 8th ventrite(Fig. 37D) posteromedially with a large, deep, subtriangular emargination; 9th tergum (Fig. 37A)
with antecostal apophyses very long; 9th ventrite (Fig. 37B) hardly serrate posteriorly, with macrosetae long, apicolateral teeth acutely pointed, apicolateral setae moderately long; 10th tergum(Fig. 37A) rounded posteriorly. Aedeagal median lobe (Fig. 37C) broad, distinctly angulate apicolaterally, tricuspidate at apex; apical sclerotized area (Fig. 37C) hardly developed, with mediancusp moderately long, pointed, lateral cusps each broad, blunt. Endophallic median bands (Fig.
37E) moderately broad and long; lateral bands (Fig. 37E) thin; expulsion hooks (Fig. 37F) connected by the posteromesial corners to form a V-shaped structure, each relatively thin, anterolaterally with a pointed tooth, with anterior plate completely fused with posterior plate; copulatory
tube (Fig. 37E) rod-like, long, with main tube curved behind the apical 1/3, acutely pointed atapex. Parameres (Fig. 37C) moderately thick, each curved posterolaterally at the apical area; theapical area moderately long, somewhat fusiform, membranous mesially, furnished mesially with
23–24 setae of various length, two of which are moderately long.
Female: Unknown.
Biology and ecology. S. fulvivestis is distributed in the plains of western Kanto district, Honshu. The beetles inhabit leaf litter in the natural forests.
Remarks. S. fulvivestis is allied to S. basara, but it is separable from the latter species by theaedeagal median lobe apically with its median cusp shorter (Fig. 37C), the endophallic expulsion
hook thinner (Fig. 37F) and the copulatory tube with its basal chamber smaller (Fig. 37E).
Stenus basara Naomi(Figs. 38A–H, 104K)
Stenus basara Naomi, 1988a: 76; Herman, 2001: 2078; Naomi & Puthz, 2013: 143.
Type material. Holotype: ♀ (KUF), Aokigahara, Mt. Fuji, Shizuoka Pref., 20. vii. 1982, S.
Naomi leg.

The Steninae of Japan Part 2

Fig. 37. Stenus fulvivestis Naomi & Watanabe (Jinmuji, Kanagawa). A, 9th and 10th terga of male; B, 9th ventrite of male; C, aedeagus; D, 7th and 8th ventrites of male; E, apical part of median lobe with the endophallus(median bands, lateral bands and copulatory tube); F, expulsion hooks. Scale 1: 0.2 mm for A–C, E, 0.1 mm
for F; scale 2: 0.3 mm for D.

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Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

Type material examined. Paratypes: 1 ♂3 ♀ (cN), same data as holotype.
Other material examined. [HONSHU]: 1 ♂7 ♀, Mizugatsuka, Susono City, Shizuoka Pref.,5. xi. 2000, S. Nomura leg. 2 ♂1 ♀, same locality, 27. x. 2011, T. Watanabe leg.
Distribution. Japan: Honshu (Shizuoka Pref.).
Redescription. Male and female: Body 4.0–4.5 mm (fore body 1.8–2.0 mm) in length,
weakly to moderately shining, with antennae moderately long, very thin. Head dark red to black;pronotum, elytra and abdomen reddish brown; labrum dark red; antennae and legs yellowish
brown to reddish brown. Head shallowly concave, with a pair of longitudinal furrows; punctureson the lateral areas round, moderately dense, small but sparse and very small on the central area.
Pronotum with surface uneven, with indistinct median longitudinal furrow; punctures round to
elliptical, very dense, moderately large, coarse, irregular. Elytra with surface uneven, weakly
depressed near suture; punctures round to elliptical, very dense, various in size but moderately
large in average, coarse. Tarsi each with 4th tarsomere strongly bilobed. Abdomen with punctures round, dense, small, regular in anterior segments, while punctures in posterior segments
dense and very small, or existing simply as setal sockets. Lateroventrites and tergoventrite
sutures missing.
Male: Sixth ventrite (Fig. 38G) posteromedially with a bell-shaped, ﬂat area; 7th ventrite(Fig. 38G) posteromedially with an elongate, bell-shaped, shallow depression, which is shallowly emarginate; 8th ventrite (Fig. 38G) posteromedially with a V-shaped emargination; 9th tergum (Fig. 38A) with antecostal apophyses long; 9th ventrite (Fig. 38B) minutely serrate posteriorly, with macrosetae short, apicolateral teeth very long, acutely pointed, apicolateral setae long;
10th tergum (Fig. 38A) entire. Aedeagal median lobe (Fig. 38F) broad, distinctly angulate apicolaterally, tricuspidate at apicomedian part; apical sclerotized area (Fig. 38F) very short, arcuate
anteriorly, with median cusp very long, pointed, lateral cusps each blunt. Endophallic medianbands (Fig. 38F) very long; lateral bands (Fig. 38F) very long, thin; expulsion hooks (Fig. 38D)
fused by the posteromesial margins of posterior plate, each thick, with anterior plate partiallyfused with posterior plate, the posterior plate rounded posteriorly; copulatory tube (Fig. 38E)
moderately long, with basal chamber large, elongate-elliptical, main tube moderately thick,curved near apex, basiventrally with paired, sclerotized ﬂaps. Parameres (Fig. 38F) each long;
apical area large, long, moderately angulate mesially at base, having a developed dorsal ﬂap, furnished mesially with 30 to 36 setae of various length.
Female: Eighth ventrite pointed posteromedially; gonocoxites (Fig. 38C) each toothed posteriorly, with apicolateral tooth very long, acutely pointed, apicolateral setae very long. Spermatheca (Fig. 38H) with capsule elongate, rounded apically; RT-duct moderately thick, broadened
distally; duct long, thin, tightly coiled; basal valve moderately long; basal sclerotized duct a little
longer than basal valve. Bursa copulatrix subconical, broadly emarginate posteriorly.
Biology and ecology. S. basara is presently known only from the southern foot of Mt. Fuji of
Chubu district, Honshu. The beetles inhabit leaf litter in the natural forests.
Remarks. S. basara is allied to S. fulvivestis, but it is separable from the latter species by theaedeagal median lobe with its median cusp longer (Fig. 38F), the endophallic expulsion hookthicker (Fig. 38D), and the copulatory tube with its basal chamber larger (Fig. 38E).
Etymology. The speciﬁc epithet of this species is derived from the name of god “Basara”,
which appeared in the Japanese ancient mythology.

The Steninae of Japan Part 2

Fig. 38. Stenus basara Naomi (A, Mizugatsuka, Shizuoka). A, 9th and 10th terga of male; B, 9th ventrite ofmale; C, posterior part of gonocoxite; D, expulsion hooks; E, copulatory tube; F, aedeagus; G, 6th to 8th ventrites of male; H, spermatheca. Scale 1: 0.2 mm for A, B, F, 0.1 mm for C–E, H; Scale 2: 0.3 mm for G.

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Stenus asyura Naomi(Figs. 39A–I, 104 L)
Stenus asyura Naomi, 1988a: 75; Herman, 2001: 2068; Naomi & Puthz, 2013: 143.
Type material. Holotype: ♂ (KUF), Jigoku Valley, Kiyosato, Mt. Yatsu, Yamanashi Pref., 8.
vii. 1982, S. Naomi leg.
Type material examined. Paratypes: 5 ♂ (cN), same data as holotype.
Other material examined. [HONSHU]: 1 ♂, Mt. Jinbagata, Nakagawa Vil., Nagano Pref., 2.
v. 1998, T. Shimada leg.; 2 ♂2 ♀, Kanayama-daira, Sutama-machi, Yamanashi Pref., 13. vi.
1982, T. Kishimoto leg.; 1 ♂, Gozaishi Spa, Yamanashi Pref., 12. viii. 1989, T. Ito leg.; 1 ♂,Aokigahara, Mt. Fuji, Yamanashi Pref., 14. ix. 2011, T. Watanabe leg.; 1 ♂, Tencho, Shioya-cho,
Tochigi Pref., 18. v. 1993, T. Kishitomo leg.; 2 ♂2 ♀, Tsukuba City, Ibaraki Pref., 14. iv. 2007, P.
Jałoszynski leg.; 1 ♂, Mt. Tsukuba (600–700 m), Tsukuba City, Ibaraki Pref., 2. xii. 2001, P.
Jałoszynski leg.; 3 ♂, Komine Pass, Hachioji City, Tokyo, 15–16. vii. 1996, T. Kishimoto leg.;1 ♂, Oyama, Machida City, Tokyo, 19. v. 1991, T. Kishimoto leg.; 1 ♂, Yokosuka City,
Kanagawa Pref., 15. iv. 1999, I. Kawashima leg.; 1 ♂, Tomioka, Yokohama City, Kanagawa
Pref., 27–28. vii. 1992, T. Kishimoto leg.; 2 ♂1 ♀, Aoba-cho, Chiba City, Chiba Pref., 31. i.
1994, Y. Hagino leg.; 1 ♀, same locality, 29. ix. 1993, Y. Hagino leg.; 2 ♂, same locality, 6. ii.
1994, Y. Hagino leg.; 1 ♂, Kashiwai, Chiba City, Chiba Pref., 5. iv. 1997, S. Nomura leg.; 1 ♂,Noman, Ichihara City, Chiba Pref., 20. vii. 2004, S. Naomi leg.; 1 ♂, same locality, 31. vii. 2004,
Y. Hagino leg.; 2 ♂, Yoro Valley, Ichihara City, Chiba Pref., 1. vi. 1993, S. Naomi leg.
Distribution. Japan: Honshu (Chubu and Kanto districts).
Redescription. Male and female: Body 3.0–3.5 mm (fore body 1.6–1.8 mm) in length, moderately shining, with antennae moderately long, very thin. Body clear reddish brown but the lateral parts of head and posterior abdominal segments infuscate. Head shallowly concave, with apair of longitudinal furrows; punctures round, moderately dense to dense, small, distinct. Pronotum with surface uneven, with indistinct median longitudinal furrow; punctures round to elliptical, very dense, moderately large, coarse. Elytra with surface weakly uneven, almost ﬂat nearsuture; punctures round to elliptical, very dense, moderately large to large, coarse. Tarsi eachwith 4th tarsomere strongly bilobed. Abdomen with punctures round to elliptical, moderately
dense to dense, small in anterior segments, while punctures in posterior segments elliptical,
dense and very small, or existing simply as setal sockets. Lateroventrites and tergoventrite
sutures missing.
Male: Eighth ventrite (Fig. 39F) posteromedially with a subtriangular emargination; 9th tergum (Fig. 39E) with antecostal apophyses long; 9th ventrite (Fig. 39A) irregularly serrate posteriorly, with macrosetae very long, apicolateral teeth short, acutely pointed, apicolateral setae very
long; 10th tergum (Fig. 39E) rounded posteriorly. Aedeagal median lobe (Fig. 39B, C) broad,
distinctly angulate apicolaterally, tricuspidate at apical part; apical sclerotized area (Fig. 39B, C)
short, transverse, with median cusp very long, thin, pointed, lateral cusps each relatively broad,angulate. Endophallic median bands (Fig. 39B, C) each with basal band very long, thin, foldedband short; lateral bands (Fig. 39B, C) long, very thin; expulsion hooks (Fig. 39G) connected bymembrance at the posteromesial sides of posterior plates, each thin, with anterior plate partiallyfused with posterior plate, the posterior plate pointed posteriorly; copulatory tube (Fig. 39D)
long, with basal chamber ovoidal, main tube rod-like, straight, apically swollen to form a fusiform or subovoidal tip. Parameres (Fig. 39B, C) each with stem very thick at base; apical area

The Steninae of Japan Part 2

Fig. 39. Stenus asyura Naomi (A–D, G–I, Kiyosato, Yamanashi; E, F, Machida, Tokyo). A, 9th ventrite of male;
B, C, aedeagus; D, copulatory tube; E, 9th and 10th terga of male; F, posterior part of 8th ventrite of male; G,
expulsion hooks; H, spermatheca; I, posterior part of gonocoxite. Scale 1: 0.1 mm for A, H; Scale 2: 0.2 mm
for B, C, E, F, 0.1 mm for D, G, I.

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moderately long, angulate mesially at base, furnished mesially with 5 to 6 setae at base, with 2 to
3 long and several short setae near the apical 1/3.
Female: Eighth ventrite pointed posteromedially; gonocoxites (Fig. 39I) each toothed posteriorly, with apicolateral tooth long, acutely pointed, apicolateral setae very long. Spermatheca(Fig. 39H) with capsule missing; RT-duct moderately long and thick; duct long, thin to moderately thick, irregularly, very tightly coiled; gland small, almost ovoidal, wholly covered withvery thin, long ciliae; basal valve short; basal sclerotized duct long. Bursa copulatrix (Fig. 39H)
large, funnel-like, with a very deep, narrow emargination at base.
Biology and ecology. S. asyura is a common species; and it is widely distributed in the plains
and low mountainous regions of central Honshu. The beetles inhabit leaf litter in the natural aswell as relatively dried forests.
Remarks. S. asyura is the sister species of S. hakonensis; and it is separable from the latter
species by the lighter coloration of body (Fig. 104L), the endophallic expulsion hook thinner,with its posterior plate pointed posteriorly (Fig. 39G), the copulatory tube with its main tube
straight and fusiform or subovoidal at apex (Fig. 39D), and the spermathecal duct with its RTduct much thinner (Fig. 39H).
Etymology. The speciﬁc epithet of this species is derived from the name of god “Asyura”,
which appeared in the Japanese ancient mythology.
Stenus hakonensis Naomi(Figs. 40A–H, 105A)
Stenus asyura hakonensis Naomi, 2004b: 29; Naomi & Puthz, 2013: 143.
Stenus hakonensis Naomi, 2015: 26.
Type material examined. Holotype: ♂ (CBM), Sengokubara, Hakone, Kanagawa Pref., 25. x.
1985, S. Nomura leg. Paratypes: 3 ♂1 ♀ (cN), same data as holotype.
Other material examined. [HONSHU]: 2 ♂1 ♀, Hiryu fall, Hakone, Kanagawa Pref., 25. iv.
1997, S. Naomi leg.; 2 ♂3 ♀, Jogao Pass, Yamakita-cho, Kanagawa Pref., 16. xi. 1996, S.
Nomura leg.; 1 ♂3 ♀, Mt. Daigatake, Hakone, Kanagawa Pref., 3. iii. 2001, H. Mizushima leg.;3 ♂2 ♀, Shiroishi-zawa, Tanzawa, Kanagawa Pref., 10. xi. 2002, S. Nomura leg.; 2 ♂4 ♀, Shiraito, Shizuoka Pref., 28. vi. 1991, T. Ito leg.; 1 ♂, Nishi-usuzuka, Fujinomiya, Shizuoka Pref., 7.
x. 2007, T. Watanabe leg.; 2 ♂2 ♀, Taro-bou, Mt. Fuji, Gotenba, Shizuoka Pref., 10. x. 1991, S.
Nomura leg; 1 ♂1 ♀, Mikuni Pass, Yamanakako Vil., Yamanashi Pref., 16. xi. 2002, S. Nomura
leg.
Distribution. Japan: Honshu (Chubu and Kanto districts).
Redescription. Male and female: Body 3.2–4.0 mm (fore body 1.7–2.0 mm) in length, moderately shining, with antennae moderately long, very thin. Head reddish or dark brown to black;pronotum and elytra reddish brown to dark brown; abdomen dark brown; labrum, antennae andlegs yellowish brown to reddish brown. Head shallowly concave, with a pair of longitudinal furrows; punctures round, moderately dense to dense, small. Pronotum with surface uneven, withindistinct median longitudinal furrow; punctures round, very dense, moderately large, coarse.
Elytra with surface weakly uneven, almost ﬂat near suture; punctures round to elliptical, very
dense, moderately large to large, coarse, sometimes two or more punctures partially fused. Tarsi
each with 4th tarsomere strongly bilobed. Abdomen with punctures round to elliptical, moderately dense to dense, small in anterior segments, while punctures in posterior segments round toThe Steninae of Japan Part 2

Fig. 40. Stenus hakonensis Naomi ((A, F, Shiroishi, Kanagawa; B–D, Daigatake, Kanagawa; E, G, H, Sengokubara Kanagawa). A, spermatheca; B, 9th and 10th terga of male; C, 9th ventrite of male; D, copulatorytube; E, aedeagus; F, gonocoxite; G, expulsion hooks; H, posterior part of 8th ventrite of male. Scale 1:
0.1 mm for C; Scale 2: 0.2 mm for A, D, F, G, 0.1 mm for B, E; Scale 3: 0.1 mm for H.

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elliptical, dense, very small. Lateroventrites and tergoventrite sutures missing.
Male: Eighth ventrite (Fig. 40H) posteromedially with a subtriangular emargination; 9th tergum (Fig. 40B) with antecostal apophyses long; 9th ventrite (Fig. 40C) serrate posteriorly, withmacrosetae very long, apicolateral teeth short, acutely pointed, apicolateral setae long; 10th tergum (Fig. 40B) entire. Aedeagal median lobe (Fig. 40E) broad, distinctly angulate apicolaterally,
tricuspidate at apicomedian part; apical sclerotized area (Fig. 40E) transverse, arcuate anteriorly,
with median cusp very long, thin, pointed, lateral cusps each angulate or pointed. Endophallic
median bands (Fig. 40E) each long, narrowed anteriorly; lateral bands (Fig. 40E) long, thin;
expulsion hooks (Fig. 40G) fused at the posteromesial corners, each moderately thick, with anterior plate partially fused with posterior plate, the posterior plate rounded posteriorly; copulatory
tube (Fig. 40D) moderately long, with basal chamber with two thin rods of the same length (Fig.
40E) or of different length (Fig. 40D), main tube rod-like, curved near the middle, very thin andsubulate at the apical-most part. Parameres (Fig. 40E) each with stem very thick at base; apicalarea short to moderately long, weakly angulate mesially at base, furnished mesially with 1 to 2
setae at base, with 2 to 3 setae near the apical 1/3.
Female: Eighth ventrite rounded or weakly angulate posteromedially; gonocoxites (Fig. 40F)
each toothed posteriorly, with apicolateral tooth long, pointed, apicolateral setae very long. Spermatheca (Fig. 40A) with capsule broad, rounded apically; RT-duct very large and thick, long,almost fusiform; duct long, almost tightly coiled, moderately thick except for the thick distal portion; basal pouch bell-shaped.
Biology and ecology. S. hakonensis is distributed in the mountainous regions of central Honshu. The beetles inhabit leaf litter in the natural forests. The habitus and the external structure of
the aedeagus of S. hakonensis are, as described above, highly similar to those of S. asyura, showing that morphologically, these two species form sibling species. However, although their distributional ranges partially overlap in the southern part of central Honshu, they seem to segregate
their habitats from each other. Namely, generally speaking, the beetles of S. hakonensis tend to
inhabit the wet natural forests at the mountainous areas, while the beetles of S. asyura tend to
inhabit the dry secondary forests at the plain and low mountainous areas. This seems to suggestthat they have different ecological requirements at least regarding the degree of humidity.
Remarks. S. hakonensis is the sister species of S. asyura; and it is separable from the latter
species by the darker coloration of body (Fig. 105A), the endophallic expulsion hook thicker,
with its posterior plate rounded posteriorly (Fig. 40G), the copulatory tube with its main tube
curved near the middle, and very thin and subulate at the apical-most part (Fig. 40D), and thespermathecal duct with its RT-duct much thicker (Fig. 40A).
Stenus nogohakusanus Naomi, Nomura & Kamezawa(Figs. 41A–H, 105B)
Stenus nogohakusanus Naomi, Nomura & Kamezawa, 2015: 322.
Type material examined. Holotype: ♂ (NMNST), Mt. Nogo-hakusan, Ohno City, Fukui Pref.,4. x. 2002, S. Nomura leg. Paratypes: 2 ♂ 6 ♀ (NMNST) & 6 ♂ 9 ♀ (cN), same data as holotype; 2 ♂ (cN), Nukumi Pass, Ohno City, Fukui Pref., 4. x. 2002, S. Nomura leg.
Distribution. Japan: Honshu (Fukui Pref.).
Redescription. Male and female: Body 4.5–5.6 mm (fore body 2.0–2.6 mm) in length,
weakly shining, with antennae moderately long, very thin. Head black; pronotum and elytra red-The Steninae of Japan Part 2

Fig. 41. Stenus nogohakusanus Naomi (Nogohakusan, Fukui). A, 9th and 10th terga of male; B, aedeagus; C, 9th
ventrite of male; D, posterior part of gonocoxite; E, spermatheca; F, posterior part of 8th ventrite of male; G,
expulsion hooks; H, 6th and 7th ventrites of male. Scale 1: 0.2 mm for A–C, F, 0.1 mm for D–E, G; Scale 2:
0.3 mm for H.

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Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

dish brown; abdomen dark reddish brown to dark brown; labrum, antennae and legs reddish
brown. Head weakly concave, with a pair of shallow longitudinal furrows; punctures round,moderately dense, small, regular, somewhat umbilicate. Pronotum with surface weakly uneven,with indistinct median longitudinal furrow; punctures round, very dense, moderately large,coarse. Elytra with surface weakly uneven, almost ﬂat near suture; punctures round to almost
round, very dense, various in size but large in average, coarse. Tarsi each with 4th tarsomere
strongly bilobed. Abdomen with punctures round, moderately dense, small, regular in anterior
segments, while punctures in posterior segments round, sparse, very small, regular. Lateroventrites and tergoventrite sutures missing.
Male: Sixth ventrite (Fig. 41H) posteromedially with a bell-shaped ﬂat area; 7th ventrite(Fig. 41H) posteromedially with an elongate ﬂat area; 8th ventrite (Fig. 41F) posteromediallywith a subtriangular emargination; 9th tergum (Fig. 41A) with antecostal apophyses very long,thick; 9th ventrite (Fig. 41C) hardly serrate posteriorly, with macrosetae short, apicolateral teeth
short, pointed, apicolateral setae moderately long; 10th tergum (Fig. 41A) weakly emarginate
posteriorly. Aedeagal median lobe (Fig. 41B) broad, distinctly angulate or weakly protruding apicolaterally, tricuspidate at apex; apical sclerotized area (Fig. 41B) hardly developed, with mediancusp long, pointed, lateral cusps each small, pointed. Endophallic median bands (Fig. 41B) each
long, weakly diverging anteriorly; lateral bands (Fig. 41B) long, thin; expulsion hooks (Fig. 41G)
connected at the mesial margins, each solid, broad, rounded posterolaterally, anterolaterally withtwo depressions of different size; copulatory tube (Fig. 41B) long, with basal chamber ovoidal,
membranous, main tube rod-like, moderately swollen basally, then attenuate toward apex. Parameres (Fig. 41B) each thin, acutely pointed at apex; apical area rather short, furnished mesiallywith 12 to 13 setae along the ventral margin.
Female: Eighth ventrite weakly pointed posteromedially; gonocoxites (Fig. 41D) each
toothed posteriorly, with apicolateral teeth very long, acutely pointed, apicolateral setae very
long. Spermatheca (Fig. 41E) with capsule very small; RT-duct long, very thick at base, becoming thinner distally; duct moderately thick to thick, loosely coiled, moderately long with 6 turns;
gland large, spherical, with its opening located on the duct between 3rd and 4th turns; basal valve
short; basal sclerotized duct stout, about 3 times as long as basal valve. Basal structure (Fig. 41E)
bowl-shaped.
Biology and ecology. S. nogohakusanus is distributed in the mountainous regions of thenorthwestern part of Chubu district, Honshu. The beetles inhabit leaf litter in the natural forest.
Remarks. S. nogohakusanus is allied to S. asyura and S. hakonensis, but it is separable fromthe latter two species by the darker coloration of body (Fig. 105B), the aedeagal median lobe
with its apical sclerotized area more strongly angulate (Fig. 105B), and the paramere with its apical area densely furnished mesially with the more number of setae (Fig. 41B).
Stenus yukawai Naomi(Figs. 42A–E, 105C)
Stenus yukawai Naomi, 2004c: 186; Naomi & Puthz, 2013: 143.
Type material examined. Holotype: ♂ (CBM), Kanaya, Kanaya-cho, Shizuoka Pref., 13–15.
iv. 1994, H. Hayakawa leg. Paratype: ♂ (cN), Arano, Hamaoka-cho, Shizuoka Pref., 18. vii.
1991, H. Ishikawa leg.
Distribution. Japan: Honshu (Shizuoka Pref.).

The Steninae of Japan Part 2

101

Fig. 42. Stenus yukawai Naomi (A, Arano, Shizuoka; B–E, Kanaya, Shizuoka). A, aedeagus of dorsal view; B,
aedeagus of ventral view; C, 9th and 10th terga of male; D, 9th ventrite of male; E, 8th ventrite of male. Scale
1: 0.2 mm for A; Scale 2: 0.2 mm for B–E.

Redescription. Male: Body 3.6–4.0 mm (fore body 1.8–1.9 mm) in length, weakly shining,with antennae relatively short, thin. Head and abdomen dark reddish brown to dark brown; pronotum and elytra reddish brown; labrum clear reddish brown; antennae and legs yellowish brown
to reddish brown. Head weakly concave, with a pair of longitudinal furrows; punctures round toalmost round, moderately dense to dense, small, somewhat umbilicate. Pronotum with surface
weakly uneven, with indistinct median longitudinal furrow; punctures round, very dense, moderately large, somewhat coarse. Elytra with surface almost even; punctures round to elliptical, very
dense, large. Legs relatively thick; tarsi each with 4th tarsomere strongly bilobed. Abdomen with
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Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

punctures in posterior segments elliptical, moderately dense to dense, very small, shallow. Lateroventrites and tergoventrite sutures missing.
Eighth ventrite (Fig. 42E) posteromedially with an arcuate emargination; 9th tergum (Fig.
42C) with antecostal apophyses relatively long; 9th ventrite (Fig. 42D) minutely serrate posteriorly, with macrosetae short, apicolateral teeth short, acutely pointed, apicolateral setae short; 10th
tergum (Fig. 42C) very weakly emarginate posteriorly. Aedeagal median lobe (Fig. 42A, B) broad,
distinctly angulate apicolaterally, simply pointed at apex; apical sclerotized area (Fig. 42B) short,broad-V-shaped, declivous posteriorly, with a median longitudinal keel. Endophallic medianbands (Fig. 42A, B) long, very thin apically; expulsion hooks (Fig. 42A, B) Y-shaped, thin, withanterior plates V-shaped, posterior plates fused to form a straight, thin, rod-like structure; copulatory tube (Fig. 42A, B) thin, with basal chamber ovoidal, small, main tube thin, attenuate, twice
weakly bent dorsoventrally. Parameres (Fig. 42A, B) each moderately thick; apical area moderately long, distinctly swollen and angulate mesially at base, furnished mesially with 5 to 6 setae atbase, with 5 to 7 setae at apex, and with 3 to 4 short setae along ventral margin.
Female: Unknown.
Biology and ecology. S. yukawai is a rare species; and it is distributed in the plains of thesouthern part of Chubu, Honshu. The beetles inhabit leaf litter in the natural forests.
Remarks. Given their similar distributional ranges (Southern part of Chubu district, central
Honshu) as well as the unique Y-shaped endophallic expulsion hooks, the 3 species S. yukawai,
S. alesi and S. daikoku no doubt form a monophyletic group. S. yukawai is separable from thelatter two species by the aedeagal median lobe simply pointed apically (Fig. 42B), and the endophallic median bands narrower (Fig. 42B).
Etymology. This species is named in honor of Dr. Junichi Yukawa (Kyushu University, Fukuoma), who studied the biology and taxonomy of gall-making insects.
Stenus alesi Naomi(Figs. 43A–F, 105D)
Stenus alesi Naomi, 2015: 26.
Type material examined. Holotype: ♂ (CBM), Hirano, Shizuoka City, Shizuoka Pref., 11. xi.
2007, Y. Hirano leg. Paratypes: 1 ♀ (cN), same locality, 11. xi. 2007, Y. Hirano leg.; 1 ♀ (cN),same locality, 11. xi. 2007, T. Shimada leg.
Other material examined. [HONSHU]: 1 ♂ 1 ♀, Udoyama, Shizuoka City, Shizuoka Pref.,23. x. 2016, T. Watanabe leg.
Distribution. Japan: Honshu (Shizuoka Pref.).
Redescription. Male and female: Body 2.9–3.0 mm (fore body 1.5–1.6 mm) in length,
weakly shining, with antennae moderately long, very thin. Head and abdomen dark reddish or
dark brown to black; pronotum and elytra reddish brown; labrum reddish brown; antennae andlegs yellowish brown to reddish brown. Head weakly concave, with a pair of longitudinal furrows; punctures round, dense, small, umbilicate. Pronotum with surface uneven, with indistinct
median longitudinal furrow; punctures round to almost round, very dense, moderately large,coarse. Elytra with surface almost even, ﬂat near suture; punctures round to elliptical, very dense,
moderately large to large. Legs with femora relatively thick; tarsi each with 4th tarsomere
strongly bilobed. Abdomen with punctures round to elliptical, dense, small in anterior segments,
while punctures in posterior segments very small, regular. Lateroventrites and tergoventrite

The Steninae of Japan Part 2

103

Fig. 43. Stenus alesi Naomi (Hirano, Shizuoka). A, spermatheca and bursa copulatrix; B, aedeagus; C, 9th ventrite of male; D, copulatory tube; E, expulsion hooks; F, posterior part of 8th ventrite of male. Scale 1: 0.1 mm
for A, D, E, 0.2 mm for B, C; Scale 2: 0.2 mm for F.

sutures missing.
Male: Seventh ventrite posteromedially with a ﬂat area; 8th ventrite (Fig. 43F) posteromedially with a medium-sized emargination; 9th tergum with antecostal apophyses moderately long;
9th ventrite (Fig. 43C) minutely serrate posteriorly, with macrosetae short, apicolateral teeth
short, acutely pointed, apicolateral setae moderately long; 10th tergum entire. Aedeagal median
lobe (Fig. 43B) broad, obtusely angulate apicolaterally, tricuspidate at apical part; apical sclerotized area (Fig. 43B) transverse, with median cusp long, thin, pointed, lateral cusps each broad,obtusely angulate, and also sculptured with thin, longitudinal lines. Endophallic median bands(Fig. 43B) each very broad at base, strongly narrowed anteriorly; expulsion hooks (Fig. 43E)

104

Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

Y-shaped, with posterior plates partially fused posteriorly (Fig. 43B) or fused only at the posterior parts (Fig. 43E), each hook thin, with anterior plate partially fused with the posterior plate;copulatory tube (Fig. 43D) with basal chamber ovoidal, main tube rod-like, attenuate, twice
weakly bent dorsoventrally. Parameres (Fig. 43B) each acutely pointed at apex; apical area long,narrowed apically, furnished mesially with a tuft of 4 to 5 setae at base, and with a tuft of 3 to 4
setae near the apicalmost part.
Female: Eighth ventrite obtusely angulate posteromedially; gonocoxites each with apicolateral tooth pointed. Spermatheca (Fig. 43A) with capsule small, rounded apically; RT-duct moderately long, thick; duct long, relatively thin to moderately thick; basal valve short; basal sclerotized duct long, thin. Bursa copulatrix (Fig. 43A) well-sclerotized, deeply emarginate at base,with a pair of pointed lateral processes which turn anteriorly.
Biology and ecology. S. alesi is a rare species; and it is distributed in the low mountainous
regions of the southern part of Chubu district, Honshu. The beetles inhabit leaf litter in the natural forest.
Remarks. S. alesi is allied to S. daikoku, but it is separable from the latter species by theaedeagal median lobe with its apicomedian area simply tricuspidate (Fig. 43B), and the endophallic copulatory tube with its main tube attenuate and weakly sinuous (Fig. 43D).
Etymology. This species is named in honor of Dr. Aleš Smetana (Agriculture and Agrifood
Canada, Ottawa), who studied the taxonomy of Staphylinidae, Hydrophilidae and other Coleopterous families.
Stenus daikoku Naomi(Fig. 44A–G)
Stenus daikoku Naomi, 2004b: 29; Naomi & Puthz, 2013: 143.
Type material examined. Holotype: ♂ (CBM), Nihondaira, Shimizu City, Shizuoka Pref., 1.
v. 1989, Y. Saida leg.
Distribution. Japan: Honshu (Shizuoka Pref.).
Redescription. Male and female: Body 3.9 mm (fore body 1.7 mm) in length, weakly shining, with antennae relatively short, thin. Head and abdomen dark brown to black; pronotum andelytra clear reddish brown; labrum reddish brown; antennae and legs yellowish brown to reddish
brown. Head weakly concave, with a pair of longitudinal furrows; punctures round to almost
round, dense, small, umbilicate. Pronotum with surface weakly uneven, with very indistinct
median longitudinal furrow; punctures round to almost round, very dense, moderately large,coarse. Elytra with surface almost even, ﬂat near suture; punctures round to elliptical, very dense,
moderately large, two or more punctures sometimes partially fused. Legs with femora relatively
thick; tarsi each with 4th tarsomere strongly bilobed. Abdomen with punctures round to elliptical, dense, small in anterior segments, while punctures in posterior segments very small, moderately dense, regular. Lateroventrites and tergoventrite sutures missing.
Male: Seventh ventrite (Fig. 44F) posteromedially with a bell-shaped, ﬂat area; 8th ventrite(Fig. 44F) posteromedially with a medium-sized, triangular emargination; 9th tergum (Fig. 44E)
with antecostal apophyses long; 9th ventrite (Fig. 44A) serrate posteromedially, with macrosetae
moderately long, apicolateral teeth short, acutely pointed, apicolateral setae short; 10th tergum
very shallowly emarginate. Aedeagal median lobe (Fig. 44B) broad, distinctly angulate at apicolateral corners, tricuspidate at apicomedian part; apical sclerotized area (Fig. 44B) stiff, trans-

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Fig. 44. Stenus daikoku Naomi (Nihondaira, Shizuoka). A, 9th ventrite of male; B, aedeagus; C, fore body; D,
copulatory tube; E, 9th and 10th terga of male; F, 7th and 8th ventrites of male; G, expulsion hooks. Scale 1:
0.2 mm for A, B, E, 0.1 mm for D, G; Scale 2: 0.3 mm for C; Scale 3: 0.3 mm for F.

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Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

verse, with a square, deep concavity existing just above the median cusp, and with median cusp
short, thin, pointed, lateral cusps each distinctly angulate. Endophallic median bands (Fig. 44B)
each very broad at base, strongly narrowed anteriorly; expulsion hooks (Fig. 44G) Y-shaped dueto the mesially fused posterior plates; copulatory tube (Fig. 44D) moderately long, with maintube strongly constricted between the basal and apical tubes. Parameres (Fig. 44B) each acutely
pointed at apex; apical area moderately long, distinctly angulate and swollen mesially at base,narrowed apically, furnished with a tuft of 2 to 3 setae at base, a tuft of 3 to 4 setae near the apical-most part, and also with 2 very short setae at the middle of dorsal margin.
Female: Unknown.
Biology and ecology. S. daikoku is a rare species, which is only once collected from the plainof southern Chubu district, Honshu. The beetles inhabit leaf litter in the natural forest.
Remarks. S. daikoku is allied to S. alesi, but it is separable from the latter species by theaedeagal median lobe with its apicomedian area tricuspidate but characteristic in that a square,
deep concavity exists just above the median cusp (Fig. 44B), and the endophallic copulatory tube
with its main tube strongly constricted between the basal and apical tubes (Fig. 44D).
Etymology. The speciﬁc epithet of this species is derived from the name of one of the Seven
Gods of Good Fortune “Daikoku”, which appears in the Japanese ancient mythology.
The oni-subgroup
The “oni-group” was ﬁrst proposed by Naomi (1988a), based solely on one species S. oni;
and it was then characterized by the various characters including the modiﬁcations of the abdominal ventrites of male, the aedeagal median lobe with the bifurcate apex, etc. At present, the socalled “oni-group” comprises 8 species having the aedeagal median lobe with the bifurcate apex;
and it is considered a monophyletic group because of the robust apomorphic characters of theaedeagus (e.g., with the bifurcate apex) and the spermatheca described below. Here, the “onigroup” is tentatively treated as a subgroup of the asyura-group (i.e., oni-subgroup). This isbecause the “oni-group” is similar in habitus to the asyura-group, whereas the phylogenetic position of the “oni-group” within the asyura-group is unclear at present.
In the list of the Japanese Steninae (Naomi & Puthz, 2013), the “hannia-subg.” was recognized as a subgroup of the asyura-group, but both of the name oni-subg. and the name “hanniasubg.” designate the same subclade in Stenus as characterized below. Thus, the name oni-subg. is
adopted in this paper, because the name “oni-group” (= oni-subg. of this paper)” was more early
used in Naomi (1988a) than the name “hannia-subg.” was in Naomi & Puthz (2013).
Diagnostic characters of the oni-subgroup: Habitus (Fig. 105J) similar to some membersof asyura-subg. (e.g., S. hijiri); antennae short to relatively short; abdomen with distinct tergoventrite sutures in 4th to 6th segments (Hemistenus-type). Male: Aedeagal median lobe withpaired apical projections (Fig. 48C) or apically with a deep, V-shaped (Fig. 51B) or other-formed(e.g., Fig. 46E) emargination; endophallic copulatory tube asymmetrical, modiﬁed with pointed
teeth (Fig. 53A), ﬂaps (Figs. 47H, 51F, 53B), protrusions of unique shapes (Figs. 52A), etc.
Female: Gonocoxite with apicolateral tooth pointed (Fig. 51G); spermatheca with RT-duct thickto very thick, sometimes narrowed apically, spermathecal duct short, usually with 2, 3 or 4 turns(Figs. 46D, 47A); spermathecal gland sometimes covered with very thin, long ciliae (Figs. 51E,
52B); bursa copulatrix conical, very large, membranous (Fig. 48D).

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Key to the Japanese species of the oni-subgroup
1(4)
2(3)

Male: Aedeagal median lobe with apical projections very narrowly separated.
Male and female: Body entirely black. Male: Sixth ventrite of male without modiﬁcation;
endophallic copulatory tube longer, straight, simply attenulate (Fig. 45C). Female; Spermathecal duct longer, with 4 turns (Fig. 45H) .....................................S. praeclarus Naomi
3(2) Male and female: Body reddish brown to dark brown. Male: Sixth ventrite of male posteromedially with a bell-shaped, ﬂat area (Fig. 46C), endophallic copulatory tube shorter,
curved, broadened toward apex in about posterior half (Fig. 46F); spermathecal duct
shorter, with 2 turns (Fig. 46D).................................................................. S. hannia Naomi
4(1) Male: Aedeagal median lobe with apical projections moderately or very widely separated.
5(10) Male: Aedeagal median lobe with apical projections very widely separated; paramerewith apical area mesially with separated setal parts.
6(7) Male: Aedeagal median lobe with apical projection strongly curved dorsally at apex (Fig.
47C); endophallic copulatory tube with main tube having a lateral ﬂap (Fig. 47H) ............
............................................................................................ S. naturalis Naomi & Watanabe
7(6) Male: Aedeagal median lobe with apical projection simply pointed at apex; endophallic
copulatory tube with main tube having no lateral ﬂap.
8(9) Male: Aedeagal median lobe with apical projections larger, thicker (Fig. 48C); endophallic copulatory tube with main tube narrowed behind the middle to the apex (Fig. 48G).
Female: Spermathecal duct longer, irregularly coiled (Fig. 48D) ....... S. zdenae Hromádka
9(8) Male: Aedeagal median lobe with apical projections smaller, thinner (Fig. 49C); endophallic copulatory tube with main tube moderately constricted a little behind the middle,
then broadened toward apex (Fig. 49F). Female: Spermathecal duct, shorter, with 2 distinct turns (Fig. 49E) ..........................................................................S. bunraku Hromádka
10(5) Male: Aedeagal median lobe with apical projections moderately separated; paramere withapical area almost uniformly setous mesially.
11(12) Male: Aedeagal median lobe broader, with apical projection shorter (Fig. 50C); endophallic copulatory tube boot-shaped (Fig. 50F) ............................................... S. haginoi Naomi
12(11) Male: Aedeagal median lobe narrower, with apical projection longer; endophallic copulatory tube not boot-shaped.
13(14) Male: Aedeagal median lobe with apical projections more widely separated (Fig. 51B);
endophallic copulatory tube with a round apical ﬂap (Fig. 51F); paramere with apical area
longer (Fig. 51B).............................................................................................. S. oni Naomi
14(13) Male: Aedeagal median lobe with apical projections more narrowly separated; endophallic copulatory tube with a lateral projection or a lateral ﬂap; paramere with apical area
shorter.
15(16) Male: Aedeagal median lobe with apical projection longer, having the narrower apex
(Fig. 52A); endophallic copulatory tube with a lateral projection near the apex (Fig. 52A)..................................................................................... S. triprotrudens Naomi & Watanabe
16(15) Male: Aedeagal median lobe with apical projection shorter, having the broader apex (Fig.
53B); endophallic copulatory tube with a large lateral ﬂap near the apex (Fig. 53A)......................................................................................... S. protrudens Naomi & Watanabe

108Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

Stenus praeclarus Naomi(Fig. 45A–H)
Stenus praeclarus Naomi, 2015: 28.
Type material examined. Holotype: ♂ (CBM), Nishijima-Ichinomori, Mt. Tsurugi Tokushima
Pref., 25. vii. 2004, O. Yamaji leg.
Other material examined. [SHIKOKU]: 2 ♂ 1 ♀, Ryotsurugi Valley, Mt. Tsurugi, Tokushima
Pref., 11. ix. 1999, M. Yoshida leg.
Distribution. Japan: Shikoku (Tokushima Pref.).
Description. Male and female: Body 3.8–4.0 mm (fore body 1.9–2.1 mm) in length, weakly
to moderately shining, with antennae relatively short, thin. Body black; labrum dark brown;
antennae reddish brown to dark brown; legs yellowish brown to dark brown. Head weakly concave, with a pair of longitudinal furrows; punctures round, sparse to moderately dense, small,irregular. Pronotum with surface uneven, with an indistinct median longitudinal furrow; punctures round to almost round, very dense, relatively small but a little larger than those on head,sometimes subrugose. Elytra with surface slightly uneven, punctures round, very dense, moderately large, Tarsi with 4th tarsomeres strongly bilobed. Abdomen with punctures round to elliptical, dense, very small to small, almost regular in anterior segments, while punctures in posterior
segments very small, sparse. Lateroventrites existing or recognizable, each thin, punctate; tergoventrite sutures distinct.
Male: Seventh ventrite (Fig. 45D) posteromedially with a semicircular ﬂat area; 8th ventrite(Fig. 45D) posteromedially with a triangular emargination; 9th tergum with antecostal apophyses
long (Fig. 45A); 9th ventrite (Fig. 45B) minutely serrate posteriorly, with macrosetae moderately
long, apicolateral teeth moderately long, acutely pointed, apicolateral setae long. 10th tergum(Fig. 45A) entire or very weakly arcuately emarginate posteriorly. Aedeagal median lobe (Fig.
45C) elongate, almost rounded at apicolateral corners; apical sclerotized area (Fig. 45G) separated right and left to form a pair of pallet-like apical projections which are broadly connected bysubmembrane, each projection pointed at apex. Endophallic median bands (Fig. 45C) long, narrow; expulsion hooks (Fig. 45E) separated but combined only by a thin string near the middles ofthe mesial sides of posterior plates, each with anterior plate rounded at apex, demarcated fromposterior plate by oblique suture, posterior plate angulate at posteromesial corner; copulatory
tube (Fig. 45C) simple, basal chamber ovoidal, main tube slender, straight, weakly swollen atbase then attenuate toward apex. Parameres (Fig. 45C) slender, very acutely pointed; apical part
relatively short, hardly swollen mesially, furnished mesially with 8 to 9 setae.
Female: Eighth ventrite obtusely pointed posteromedially; gonocoxites (Fig. 45F) each
toothed posteriorly, apicolateral tooth moderately long, acutely pointed, apicolateral setae very
long. Spermatheca (Fig. 45H) with capsule missing; RT-duct long, very thick, with sclerotizedtransverse lines each often separated into 2 or 3 sclerites; duct moderately thick to thick, relatively short with 4 turns; gland opened at the lateral side of the duct between 3rd and 4th turns;
basal valve indistinct; basal sclerotized duct long. Bursa copulatrix membranous.
Biology and ecology. S. praeclarus is a rare species; and it is presently distributed only in the
Mt. Tsurugi, the eastern part of Shikoku. The beetles inhabit leaf litter heaped in the natural forests.
Remarks. Given the common possessions of their almost similar habitus, aedeagal median
lobe and parameres, S. praeclarus is allied to S. hannia, but it is separable from the latter by the
body entirely black, the 6th ventrite of male without modiﬁcation, the endophallic expulsion

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109

Fig. 45. Stenus praeclarus Naomi (Tsurugi, Tokushima). A, 9th and 10th terga of male; B, 9th ventrite of male;C, aedeagus; D, 7th to 8th ventrites of male; E, expulsion hooks; F, posterior part of gonocoxite, G, apical partof aedeagus; H, spermatheca. Scale 1: 0.2 mm for A–C, F, 0.1 mm for E, G, H; Scale 2: 0.3 mm for D.

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hooks connected near the middles of the mesial sides of posterior plates (Fig. 45E), the copulatory tube longer, straight, simply attenulate (Fig. 45C), and the spermathecal duct longer, with 4
turns (Fig. 45H).
Stenus hannia Naomi(Figs. 46A–H, 105E)
Stenus hannia Naomi, 1990a: 104; Herman, 2001: 2212; Naomi & Puthz, 2013: 143.
Type material examined. Holotype: ♂ (CBM), Chuzenji, Nikko, Tochigi Pref., 24. vii. 1985,
S. Nomura leg. Paratypes: 9 ♂ 9 ♀ (cN), same data as holotype.
Other material examined. [HONSHU]: 2 ♂ 4 ♀, Fujimi, Mt. Akagi, Gunma Pref., 20. vii.
1996, S. Nomura leg.
Distribution. Japan: Honshu (Tochigi and Gunma Prefs.).
Redescription. Male and female: Body 3.3–3.5 mm (fore body 1.7–1.8 mm) in length,
weakly shining, with antennae relatively short, thin. Head black, with central area dark brown;
pronotum and elytra reddish brown; abdomen reddish brown but the posterior segments infuscate; labrum, antennae and legs reddish brown. Head weakly concave, with a pair of longitudinalfurrows; punctures round, moderately dense to dense, small, somewhat umbilicate. Pronotumwith surface uneven, with indistinct median longitudinal furrow; punctures round to almost
round, very dense, moderately large, coarse. Elytra with surface weakly uneven, almost ﬂat nearsuture; punctures round to elliptical, very dense, moderately large to large, coarse. Tarsi eachwith 4th tarsomere strongly bilobed. Abdomen with punctures round to almost round, moderately
dense to dense, small, regular in anterior segments, while punctures in posterior segments verysmall, regular. Lateroventrites missing; tergoventrite sutures existing.
Male: Femora moderately thick; 6th ventrite (Fig. 46C) posteromedially with a large, bellshaped, ﬂat area, which is weakly emarginate; 7th ventrite (Fig. 46C) posteromedially with anelongate-ovoidal, shallow depression; 8th ventrite (Fig. 46C) posteromedially with a subtriangular emargination; 9th tergum (Fig. 46A) with antecostal apophyses long; 9th ventrite (Fig. 46B)
irregularly serrate posteriorly, with macrosetae long, apicolateral teeth short, acutely pointed, apicolateral setae long; 10th tergum (Fig. 46A) entire. Aedeagal median lobe (Fig. 46E) moderately
broad, with a pair of apical projections narrowly separated, each simply pointed. Endophallic
median bands (Fig. 46E) broad, moderately long; expulsion hooks (Fig. 46G) separated but connected by a thin, C-shaped rod at the posteromesial corners of posterior plates, each hook withanterior plate rounded anteriorly, partially fused with posterior plate; copulatory tube (Fig. 46F)
with main tube relatively short, distinctly curved near the middle, then weakly broadened apically. Parameres (Fig. 46E) each straight, acutely pointed; apical area short, weakly angulate
mesially at base, narrowed apically, furnished mesially with 7 to 8 setae.
Female: Eighth ventrite gently rounded posteriorly; gonocoxites (Fig. 46H) each toothed
posteriorly, apicolateral tooth moderately long, thin, acutely pointed, apicolateral setae very long.
Spermatheca (Fig. 46D) with capsule missing; RT-duct long, very thick, arranged with the dense,
regular, transverse lines in its whole length; duct thick to very thick, short with 2 distinct turns;
gland opened at the mesial side of the duct between 1st and 2nd turns; basal valve long; basal
sclerotized duct short. Bursa copulatrix (Fig. 46D) very large, subconical, membranous.
Biology and ecology. S. hannia is distributed in the mountainous regions of Kanto district,central Honshu. The beetles inhabit leaf litter in the natural forests.

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Fig. 46. Stenus hannia Naomi (Chuzenji, Tochigi). A, 9th and 10th terga of male; B, 9th ventrite of male; C, 6th
to 8th ventrites of male; D, spermatheca; E, aedeagus; F, copulatory tube; G, expulsion hooks; H, posterior
part of gonocoxite. Scale 1: 0.2 mm for A, E, 0.1 mm for D, F, G; Scale 2: 0.1 mm for B; Scale 3: 0.3 mm for
C.

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Remarks. S. hannia is allied to S. praeclarus, but it is separable from the latter by the body
basically reddish brown to dark brown, the 6th ventrite of male posteromedially with a bellshaped, ﬂat area (Fig. 46C), the endophallic expulsion hooks connected at the posteromesial corners of posterior plates (Fig. 46E), the copulatory tube shorter, curved, broadened toward apex inabout posterior half (Fig. 46C), and the spermathecal duct shorter, with 2 turns (Fig. 46H).
Etymology. The speciﬁc epithet of this species is derived from the noun “Hannya”, whichmeans the “wisdom” in Buddhism.
Stenus naturalis Naomi & Watanabe(Figs. 47A–H, 105F)
Stenus naturalis Naomi & Watanabe, 2015: 102.
Type material examined. Holotype: ♂ (TUAA), Kagami-daira (alt. 2,250 m), Gifu Pref., 26.
ix. 1985, Y. Watanabe leg. Paratypes: 1 ♀ (TUAA) & 1 ♀ (cN), same data as holotype.
Distribution. Japan: Honshu (Gifu Pref.).
Redescription. Male and female: Body 4.0–4.5 mm (fore body 2.0–2.1 mm) in length,
weakly shining, with antennae short, thin. Head black; pronotum, elytra and abdomen reddish
brown to dark reddish brown; labrum dark red; antennae reddish brown but apical segments
infuscate; legs yellowish brown to reddish brown. Head weakly concave, with a pair of longitudinal furrows; punctures round, moderately dense to dense, small, somewhat umbilicate. Pronotum with surface uneven, with indistinct median longitudinal furrow; punctures very dense, subrugose. Elytra with surface uneven, weakly depressed near suture; punctures round to elliptical,very dense, moderately large, coarse. Tarsi each with 4th tarsomere strongly bilobed. Abdomenwith punctures round to elliptical, dense to very dense, small in anterior segments, while punctures in posterior segments very small, shallow, regular. Lateroventrites missing; tergoventrite
sutures existing.
Male: Legs with femora moderately thick; 4th ventrite posteromedially with a small, semicircular ﬂat area; 5th ventrite posteromedially with a semicircular, very shallow depression, whichis shallowly emarginate; 6th ventrite modiﬁed as in the 5th, but the depression in the 6th a little
deeper and larger than that in the 5th; 7th ventrite medially with an elongate-ovoidal, shallow
depression, which is shallowly emarginate; 8th ventrite (Fig. 47F) posteromedially with aV-shaped emargination; 9th tergum (Fig. 47D) with antecostal apophyses relatively short; 9th
ventrite (Fig. 47B) serrate posteriorly, with apicolateral teeth short, pointed, apicolateral setae
short; 10th tergum (Fig. 47D) very weakly emarginate. Aedeagal median lobe (Fig. 47C) broad,weakly constricted behind the middle, with apical projections very widely separated, placedalmost in parallel, each strongly curved dorsally at apex. Endophallic median bands (Fig. 47C)
broad, moderately long; expulsion hooks (Fig. 47E) fused at the posteromesial parts of posterior
plates to form a U-shaped structure, each submembranous along the mesial margin, with anterior
plate almost rounded apically, demarcated by a suture from posterior plate; copulatory tube (Fig.
47H) small, pitcher-shaped, with basal chamber large, elongate-ovoidal, main tube short, baculiform, with a lateral ﬂap. Parameres (Fig. 47C) each acutely pointed; apical area relatively long,
weakly swollen mesially at base, furnished mesially with 7 to 8 setae at base, and with 5 to 6
setae at apex.
Female: Eighth ventrite gently rounded posteriorly; gonocoxites (Fig. 47G) each toothed
posteriorly, apicolateral tooth relatively short, acutely pointed. Spermatheca (Fig. 47A) large,

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Fig. 47. Stenus naturalis Naomi (Kagami-daira, Gifu). A, spermatheca; B, 9th ventrite of male; C, aedeagus; D,
9th and 10th terga of male; E, expulsion hooks; F, posterior part of 8th ventrite of male; G, gonocoxite; H,
copulatory tube. Scale 1: 0.2 mm for B–D, 0.1 mm for E, G, H, 0.05 mm for A; Scale 2: 0.2 mm for F.

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with capsule very small, subconical; RT-duct long, very thick; duct thick, short with 3 turns;
basal valve long; basal sclerotized duct short. Bursa copulatrix (Fig. 47A) large, conical, basallywith a very deep, narrow emargination.
Biology and ecology. S. naturalis is a rare species; and it is once collected from the highmountainous regions of western Chubu district, Honshu. The beetles inhabit leaf litter in the natural forests.
Remarks. Given their common possession of the following apomorphic characters (e.g.,aedeagal median lobe with its apical projections very widely separated; parameral apical areawith separated setal portions), the three species S. naturalis, S. zdenae and S. bunraku form amonophyletic group. S. naturalis is, however, separable from the other two species by the aedeagal median lobe with its apical projections placed almost in parallel and each curved dorsally at
apex (Fig. 47C), and the endophallic copulatory tube with its main tube having a lateral ﬂap (Fig.
47H).
Stenus zdenae Hromádka(Figs. 48A–H, 105G)
Stenus zdenae Hromádka, 1990: 127; Herman, 2001: 2438; Naomi & Puthz, 2013: 143.
Type material. Holotype: ♂ (AACO), Mt. Kurofu (2100 m), Gunma Pref., 19. vii. 1980, A. &Z. Smetana.
Type material examined. Paratypes: 3 ♂ (cN), same data as holotype.
Other material examined. [HONSHU]: 1 ♀ (cN), same locality and date as holotype, I. Löbl
leg.
Distribution. Japan: Honshu (Gunma Pref.).
Redescription. Male and female: Body 3.3–3.6 mm (fore body 1.5–1.7 mm) in length,
weakly shining, with antennae short, thin. Head black; pronotum, elytra and abdomen clear yellowish brown to reddish brown; labrum reddish brown; antennae reddish brown but apical segments infuscate; legs yellowish brown to reddish brown. Head weakly concave, with a pair of
longitudinal furrows; punctures round, moderately dense to dense, small, somewhat umbilicate.
Pronotum with surface uneven, with indistinct median longitudinal furrow; punctures round,very dense, relatively small but a little larger than those on head, subrugose. Elytra with surface
uneven, weakly depressed near suture; punctures round to elliptical, very dense, moderately
large, coarse. Tarsi each with 4th tarsomere strongly bilobed. Abdomen with punctures round to
elliptical, moderately dense to dense, small in anterior segments, while punctures in posterior
segments very small, shallow. Lateroventrites missing; tergoventrite sutures existing.
Male: Legs with femora moderately thick; 6th ventrite (Fig. 48E) posteromedially with abell-shaped, ﬂat area, which is very shallowly emarginate; 7th ventrite (Fig. 48E) posteromedially with an elongate, shallow depression, which is shallowly emarginate; 8th ventrite (Fig. 48E)
posteromedially with a V-shaped emargination; 9th tergum (Fig. 48A) with antecostal apophyses
moderately long; 9th ventrite (Fig. 48B) irregularly serrate posteriorly, with macrosetae relatively short, apicolateral teeth short, pointed, apicolateral setae moderately long; 10th tergum(Fig. 48A) trapedoidal. Aedeagal median lobe (Fig. 48C) broad, moderately constricted behindthe middle, with apical projections very widely separated, weakly divergent posteriorly, eachlarge, horn-like, pointed at apex. Endophallic median bands (Fig. 48C) broad, long; lateral bands(Fig. 48C) long, very thin; expulsion hooks (Fig. 48H) fused by a V-shaped, thin rod at the pos-

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Fig. 48. Stenus zdenae Naomi (Kurofu, Gunma). A, 9th and 10th terga of male; B, 9th ventrite of male; C,aedeagus; D, spermatheca and bursa copulatrix; E, 6th to 8th ventrites of male; F, posterior part of gonocoxite;
G, copulatory tube; H, expulsion hooks. Scale 1: 0.1 mm for A–C; Scale 2: 0.1 mm for D, F–H; Scale 3:
0.3 mm for E.

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Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

teromesial corners of posterior plates, each hook with anterior plate smaller than, and demarcatedby a sulcus from posterior plate; copulatory tube (Fig. 48G) small, moderately thick, with basal
chamber large, elongate-ovoidal, main tube short, narrowed apically, weakly curved near apex.
Parameres (Fig. 48C) each pointed at apex; apical area very long, weakly swollen at base, furnished mesially with 12 to 13 setae along the dorso-basal margin, and with 6 to 7 setae along theventro-apical margin.
Female: Gonocoxites (Fig. 48F) each toothed posteriorly, apicolateral tooth moderately long,pointed, apicolateral setae very long. Spermatheca (Fig. 48D) small, with capsule very small; RTduct long, thick, nearly fusiform; duct relatively thin and short, irregularly coiled; basal sclerotized duct short; basal pouch small, subconical. Bursa copulatrix (Fig. 48D) conical, membranous but distally with a sclerotization which is deeply emarginate at base.
Biology and ecology. S. zdenae is distributed in the high mountainous regions of northern
Kanto district, Honshu. The beetles inhabit leaf litter in the natural forests.
Remarks. S. zdenae is allied to S. bunraku, but it is separable from the latter species by the
body smaller (Fig. 105G), the 9th ventrite of male broader at apex (Fig. 48A), the aedeagal
median lobe with its apical projections thicker (Fig. 48C), the endophallic copulatory tube
smaller, with its main tube narrowed toward apex behind the middle (Fig. 48G), and the spermathecal duct irregularly coiled (Fig. 48D).
Etymology. This species is named in honor of Mrs. Zdena Smetana, who collected the beetle
which was designated as the holotype of this species.
Stenus bunraku Hromádka(Figs. 49A–G, 105H)
Stenus bunraku Hromádka, 1990: 128; Puthz, 1993a: 166 (synonym of S. zdenae); Naomi, 2015:30.
Type material. Holotype: ♂ (AACO), near Mt. Shirane (2000 m), Gunma Pref., 22. vii. 1980,
A. & Z. Smetana leg.
Other material examined. [HONSHU]: 1 ♂ 1 ♀ (cN), Mt. Takenoko, Yuzawa-cho, Niigata
Pref., 30. vi. 1996, K. Haga leg.
Distribution. Japan: Honshu (Gunma and Niigata Prefs.).
Redescription. Male and female: Body 4.0–4.5 mm (fore body 2.0–2.3 mm) in length,
weakly shining, with antennae short, thin. Head black; pronotum, elytra and abdomen reddish
brown to dark reddish brown; labrum, antennae and legs yellowish brown to reddish brown.
Head weakly concave, with a pair of longitudinal furrows; punctures round, dense, small, somewhat umbilicate. Pronotum with surface uneven, with indistinct median longitudinal furrow;
punctures round to almost round, very dense, moderately large, coarse. Elytra with surface
strongly uneven, depressed along the suture; punctures round to elliptical, very dense, moderately large, coarse. Tarsi each with 4th tarsomere strongly bilobed. Abdomen with puncturesround to elliptical, dense, small in anterior segments, while punctures in posterior segments verysmall, shallow. Lateroventrites missing; tergoventrite sutures distinct.
Male: Fourth ventrite posteromedially with a semicircular ﬂat area; 5th ventrite (Fig. 49A)
posteromedially with a large, semicircular, very shallow depression, which is very shallowly
emarginate; 6th ventrite (Fig. 49A) modiﬁed as in the 5th, but the depression in the 6th a little
deeper than that in the 5th; 7th ventrite posteromedially with a large, elongate, bell-shaped

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Fig. 49. Stenus bunraku Hromádka (Shirane, Gunma). A, 5th to 8th ventrites of male; B, 9th ventrite of male; C,aedeagus with expulsion hooks; D, gonocoxite of female; E, spermatheca; F, copulatory tube; G, medianbands (of unfolded condition) and ventral sclerites. Scale 1: 0.2 mm for B, C, 0.1 mm for D–G; Scale 2:
0.3 mm for A.

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depression, which is shallowly emarginate; 8th ventrite (Fig. 49A) posteromedially with a small,V-shaped emargination; 9th tergum with antecostal apophyses thin, moderately long; 9th ventrite(Fig. 49B) strongly narrowed posteriorly, minutely serrate posteriorly, with macrosetae short,apicolateral teeth very short, pointed, apicolateral setae moderately long; 10th tergum rounded
posteriorly. Aedeagal median lobe (Fig. 49C) broad, broadly emarginate posteriorly to form abroad V-shaped notch between apical projections, the apical projections very widely separated,distinctly divergent posteriorly, each short, thin, pointed at apex. Endophallic median bands (Fig.
49G) very broad; expulsion hooks (Fig. 49C) separated, with anterior plate pointed anteriorly,
separated by a suture from posterior plate; ventral sclerites (Fig.49G) paired, each subovoidal,very small; copulatory tube (Fig. 49F) large, with basal constriction indistinct, main tube thick atbase, curved and moderately constricted a little behind the middle, then broadened toward apex.
Parameres (Fig. 49C) each slender, pointed; apical area moderately long, hardly swollen at base,furnished mesially with 4 to 5 setae at the basi-ventral margin, and with 4 to 5 setae at the apicoventral margin.
Female: Eighth ventrite gently rounded posteriorly; gonocoxites (Fig. 49D) each partially
toothed posteriorly, with apicolateral tooth moderately long, acutely pointed, apicolateral setae
moderately long. Spermatheca (Fig. 49E) with capsule missing; RT-duct moderately long, thick;duct moderately thick to thick, very short with 2 turns, membranous from the base to 1st turn;gland with its opening located at the middle of the duct between the 1st and 2nd turns.
Biology and ecology. S. bunraku is distributed in the high mountainous regions of Central
Honshu. The beetles inhabit leaf litter in the natural forests.
Remarks. S. bunraku is allied to S. zdenae, but it is separable from the latter species by the
body larger (Fig. 105H), the 9th ventrite of male narrower at apex (Fig. 49B), the aedeagal
median lobe with its apical projections thinner (Fig. 49C), the endophallic copulatory tube larger,
with its main tube moderately constricted a little behind the middle (Fig. 49F), and the spermathecal duct with 2 distinct turns (Fig. 49E).
Etymology. The speciﬁc epithet of this species is derived from the Japanese noun “Bunraku”,
which means “puppet show” in the Japanese traditional performing art.
Stenus haginoi Naomi(Figs. 50A–G, 105I)
Stenus haginoi Naomi, 1997a: 16; Herman, 2001: 2211; Naomi & Puthz, 2013: 143.
Type material examined. Holotype: ♂ (CBM), Mihira Pass, Oze Moor, Gunma Pref., 24. vii.
1995, H. Tamura et al. leg. Paratypes: 4 ♀ (cN), same locality and date as holotype, H. Tamura
leg.; 4 ♂ 4 ♀ (cN), Oze Moor, Katashina Vil., Gunma Pref., 23. x. 1994, H. Sakayori leg.;3 ♂ 5 ♀ (cN), same locality, 2. ix. 1995, H. Tamura leg.; 2 ♀ (cN), Ayame-daira, Oze Moor,
Gunma Pref., 25. vii. 1995, H. Tamura leg; 2 ♂ 4 ♀ (cN), Mt. Shibutu, Oze Moor, Gunma Pref.,3. ix. 1995, H. Tamura leg.
Other material. [HONSHU]: 1 ♂ 4 ♀ (cN), Mt. Keizuru, Katashina Vil., Gunma Pref., 13.
vii. 1996, K. Ishii et al. leg.; 3 ♂ 2 ♀ (cN), Mt. Shibutu, Oze Moor, Gunma Pref., 8. ix. 1996, Y.
Hagino leg.; 6 ♂ 9 ♀ (cN), same data, S. Nomura leg.
Distribution. Japan: Honshu (Fukushima, Gunma and Niigata Prefs.).
Redescription. Male and female: Body 4.3–4.5 mm (fore body 2.0–2.2 mm) in length,
weakly shining, with antennae relatively short, thin. Head black; pronotum, elytra and abdomen

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Fig. 50. Stenus haginoi Naomi (Shibitsu, Gunma). A, spermatheca; B, 9th and 10th terga of male; C, aedeagus;
D, 9th ventrite of male G, ; E, 4th to 8th ventrites of male; F, copulatory tube; G, posterior part of gonocoxite.
Scale 1: 0.2 mm for A, F, G, 0.1 mm for B–D; Scale 2: 0.3 mm for E.

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reddish brown to dark reddish brown; labrum, antennae and legs yellowish brown to reddish
brown. Head weakly concave, with a pair of longitudinal furrows; punctures round, moderately
dense to dense, small, somewhat umbilicate. Pronotum with surface uneven, with a moderately
deep, median longitudinal furrow; punctures round to almost round, very dense, moderately
large, coarse. Elytra with surface strongly uneven, weakly depressed along the suture; puncturesround to elliptical, very dense, moderately large to large, coarse, sometimes two or more punctures partially fused. Tarsi each with 4th tarsomere strongly bilobed. Abdomen with puncturesround to elliptical, dense, small in anterior segments, while punctures in posterior segments verysmall and sparse or existing only as setal sockets. Lateroventrites missing; tergoventrite sutures
distinct.
Male: Fourth ventrite (Fig. 50E) posteromedially with a semicircular ﬂat area; 5th and 6th
ventrites (Fig. 50E) each posteromedially with a bell-shaped, very shallow depression, which isvery shallowly emarginate; 7th ventrite (Fig. 50E) anteromedially with a ﬂat area, posteromedially with an elongate, bell-shaped, shallow depression, which is very shallowly emarginate; 8thventrite (Fig. 50E) posteromedially with a small, V-shaped emargination; 9th tergum (Fig. 50B)
with antecostal apophyses long; 9th ventrite (Fig. 50D) minutely serrate posteriorly, with macrosetae moderately long, apicolateral teeth very short, pointed, apicolateral setae short; 10th tergum(Fig. 50B) entire. Aedeagal median lobe (Fig. 50C) broad, with apical projections each short,broad at base, pointed and incurved at apex. Endophallic median bands (Fig. 50C) with basal
bands fused in the basal (anterior) 2/3 to form a large, subovoidal band, folded bands separated,each very short; expulsion hooks (Fig. 50C) invisible; copulatory tube (Fig. 50F) large, robust,with main tube boot-shaped. Parameres (Fig. 50C) each gently curved mesially; apical area moderately long, hardly swollen at base, furnished mesially with 13 to 15 moderately long setae.
Female: Eighth ventrite gently rounded posteriorly; gonocoxites (Fig. 50G) each toothed
posteriorly, with apicolateral tooth long, acutely pointed, apicolateral setae very long. Spermatheca (Fig. 50A) with capsule missing; RT-duct long, very thick; duct thin in about proximal 1/2,
moderately thick or thick in about distal 1/2, short with 4 turns; basal sclerotized duct short,moderately broad. Bursa copulatrix (Fig. 50A) very large, subconical, membranous.
Biology and ecology. S. haginoi is at present known only from the Oze Moor and its neighboring high mountainous areas, Central Honshu. The beetles inhabit leaf litter in the natural forests.
Remarks. S. haginoi is allied to S. oni, S. triprotrudens and S. protrudens, but it is separablefrom the latter three species by the aedeagal median lobe broader, with its apical projections a little shorter (Fig. 50C), and the endophallic copulatory tube boot-shaped (Fig. 50F).
Etymology. This species is named in honor of Mr. Yasunori Hagino (Natural History
Museum and Institute, Chiba), who studies the Pauropoda.
Stenus oni Naomi(Figs. 51A–G, 105J)
Stenus oni Naomi, 1988a: 81; Herman, 2001: 2313; Naomi & Puthz, 2013: 143.
Stenus basara Naomi, 1988a: 78 (partim).
Type material. Holotype: 1 ♀ (KUF), Mt. Maeshirane, Oku-Nikko, Tochigi Pref., 2. vii.
1982, S. Naomi leg.
Type material examined. Paratype of S. oni: ♂ (cP), same data as holotype. Paratypes of S.

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Fig. 51. Stenus oni Naomi (A–D, F, Maeshirane, Tochigi; E, G, Konsei, Tochigi). A, 9th and 10th terga of male;B, aedeagus; C, 3th to 8th ventrites of male; D, 9th ventrite of male; E, spermathecal and bursa copulatrix; F,
copulatory tube; 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.

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basara (= S. oni): 2 ♀ (cN), Konsei Pass, Oku-Nikko, Tochigi Pref., 30. vi. 1982, S. Naomi leg.
Other material examined. [HONSHU]: 1 ♀ (cP), Nikkozawa-Kinunuma, Kuriyama Vil.,
Tochigi Pref., 3. ix. 1991, S. Naomi leg.
Distribution. Japan (Honshu: Tochigi Pref.).
Redescription. Male and female: Body 4.0–4.3 mm (fore body 1.9–2.1 mm) in length,
weakly shining, with antennae relatively short, thin. Head black; pronotum, elytra and abdomen
reddish brown; labrum, antennae and legs yellowish brown to reddish brown. Head weakly concave, with a pair of longitudinal furrows; punctures round, moderately dense to dense, small.
Pronotum with surface uneven, with indistinct median longitudinal furrow; punctures round to
elliptical, very dense, small to moderately large, coarse, subrugose. Elytra with surface strongly
uneven, weakly depressed along the suture; punctures round to elliptical, very dense, moderately
large, coarse, sometimes two or more punctures partially fused. Tarsi each with 4th tarsomere
strongly bilobed. Abdomen with punctures round to elliptical, dense, small in anterior segments,
while punctures in posterior segments very small, shallow. Lateroventrites missing; tergoventrite
sutures distinct.
Male: Third ventrite (Fig. 51C) medially with a ﬂat area; 4th ventrite (Fig. 51C) ﬂat anteromedially, posteromedially with a bell-shaped, moderately deep depression, which is shallowly
emarginate; 5th to 7th (Fig. 51C) ventrites each anteromedially with a moderately deep depression, posteromedially with a similar depression as in the 4th; 8th ventrite (Fig. 51C) anteromedially with a bell-shaped, very shallow depression, posteromedially with a subtriangular emargination; 9th tergum (Fig. 51A) with antecostal apophyses long; 9th ventrite (Fig. 51D) serrate
posteriorly, with macrosetae short, apicolateral teeth short, pointed, apicolateral setae short; 10th
tergum (Fig. 51A) subtrapezoidal, weakly arcuately emarginate posteriorly. Aedeagal median
lobe (Fig. 51B) moderately broad, distinctly bifurcated apically, with a moderately deep, almost
V-shaped notch between apical projections, the apical projections each broad at base, turning
dorsally at apex, with lateral rim strongly sclerotized. Endophallic dorsal membrane (Fig. 51B)
semicircular, small; median bands (Fig. 51B) with basal bands partially fused, short, broad,folded bands widely separated, each narrowed anteriorly; expulsion hooks (Fig. 51B) fused,highly atrophied to be a small subtriangular sclerite; copulatory tube (Fig. 51F) stout, thick, maintube moderately constricted near apical 1/3, subspatulate at apex, with a round apical ﬂap. Parameres (Fig. 51B) thick, weakly converging posteriorly from the bases to the bases of apicalareas, then running in parallel to the apices; apical area very long, hardly swollen mesially, furnished mesially with 10 to 11 setae along ventral margin.
Female: Eighth ventrite weakly angulate apicomedially; gonocoxites (Fig. 51G) each toothed
posteriorly, with apicolateral tooth moderately long, acutely pointed, apicolateral setae very long.
Spermatheca (Fig. 51E) with capsule missing; RT-duct moderately thick to very thick, very longwith 2 turns; duct very thin to thin, short with 2 turns, with the duct from the base to 1st turnmembranous; gland wholly covered with very thin, long ciliae, with its opening located on thelateral side of RT-duct a little distal from the base of RT-duct. Bursa copulatrix (Fig. 51E) verylarge, conical, membranous, bi-arcuate basally.
Biology and ecology. S. oni is a rare species; and it is distributed in the mountainous regionsof northern Kanto district, Honshu. The beetles inhabit leaf litter in the natural forests.
Remarks. When Naomi (1988a) described S. basara as a new species of Stenus from Honshu,
Japan, he treated two females of S. oni as the paratypes of S. basara, due to his misidentiﬁcation.
These two females are, as described above, here treated as the specimens of S. oni. S. oni is allied
to S. triprotrudens and S. protrudens, but it is separable from the latter two species by the aedea-

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gal median lobe with its apical projections more widely separated (Fig. 51B), the endophallic
copulatory tube with a round apical ﬂap (Fig. 51F), and the paramere with its apical area longer(Fig. 51B).
Etymology. The speciﬁc epithet of this species is derived from the Japanese noun “Oni”,
namely, an “imaginary monster” which appears in the Japanese ancient folk tales.
Stenus triprotrudens Naomi & Watanabe(Figs. 52A–F, 105K)
Stenus triprotrudens Naomi & Watanabe, 2015: 104.
Type material examined. Holotype: ♂ (TUAA), Ishikorobi-zawa, Mts. Iide, Yamagata Pref.,27. vii. 1964, Y. Watanabe leg. Paratypes: 7 ♀ (TUAA) & 1 ♂ 1 ♀ (cN), same data as holotype;
1 ♀ (TUAA), Nukumi-daira, Mts. Iide, Yamagata Pref., 28. vii. 1964, K. Takahashi leg.
Distribution. Japan: Honshu (Yamagata Pref.).
Redescription. Male and female: Body 3.8–4.7 mm (fore body 1.7–2.1 mm) in length,
weakly shining, with antennae short, thin. Head black; pronotum, elytra and abdomen reddish
brown to dark reddish brown; labrum dark reddish brown; antennae and legs yellowish brown toreddish brown. Head weakly concave, with a pair of longitudinal furrows; punctures round,
dense to very dense, small, somewhat umbilicate. Pronotum with surface uneven, with moderately deep median longitudinal depression; punctures round to almost round, very dense, moderately large, coarse. Elytra with surface uneven, ﬂat along the suture; punctures round to elliptical,very dense, moderately large, coarse. Tarsi each with 4th tarsomere strongly bilobed. Abdomenwith punctures round to elliptical, dense, a little varied in size but basically small in anterior segments, while punctures in posterior segments very small and sparse, or existing simply as setal
sockets. Lateroventrites missing; tergoventrite sutures existing.
Male: Legs with femora thick; 4th ventrite posteromedially with a semicircular ﬂat area; 5thventrite posteromedially with a semicircular, very shallow depression, which is shallowly emarginate; 6th ventrite modiﬁed as in the 5th, but the depression a little deeper than that in the 5th;
7th ventrite anteromedially with a ﬂat area, posteromedially with an ovoidal, moderately deep
depression, which is emarginate posteriorly; 8th ventrite (Fig. 52D) posteromedially with aV-shaped emargination; 9th tergum (Fig. 52F) with antecostal apophyses moderately long; 9th
ventrite (Fig. 52E) serrate posteriorly, with macrosetae short, apicolateral teeth very short,pointed, apicolateral setae very short; 10th tergum (Fig. 52F) weakly emarginate posteriorly.
Aedeagal median lobe (Fig. 52A) broad, distinctly bifurcate at apex, with a very deep, narrow-Vshaped notch between apical projections, the apical projections each stout, long, almost roundedat apex. Endophallic median bands (Fig. 52A) with basal bands each short, membranous, verybroad, broadened anteriorly, folded bands widely separated, each thin, dotted; expulsion hooks(Fig. 52A) atrophied into a small, wide-V-shaped structure; copulatory tube (Fig. 52A) large,
stout, basal chamber large, with indistinct basal constriction, main tube with a funnel-shaped
apex and also with a pointed process at its left side near the apex, to form the triprotruded apex.
Parameres (Fig. 52A) each short, rounded apically; apical area hardly swollen mesially, furnishedmesially with 14 to 15 setae.
Female: Eighth ventrite gently rounded posteriorly; gonocoxites (Fig. 52C) each serrate posteriorly, apicolateral tooth moderately long, acutely pointed, apicolateral setae moderately long.
Spermatheca (Fig. 52B) with capsule small, rounded apically, RT-duct moderately long, very

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Fig. 52. Stenus triprotrudens Naomi & Watanabe (Iide, Yamagata). A, aedeagus; B, spermatheca; C, gonocoxites; D, posterior part of 8th ventrite of male; E, 9th ventrite of male; F, 9th and 10th terga of male. Scale 1:
0.2 mm for A, C–E, 0.1 mm for B; Scale 2: 0.2 mm for F.

thick; duct relatively thin at base, thick at the distal part, short with 4 turn; gland small, ovoidal,
wholly covered with very thin, long ciliae, with its opening located on the 3rd turn of the duct.
Biology and ecology. S. triprotrudens is a rare species; and it is distributed in the mountain-

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ous regions of Tohoku district, Honshu. The beetles inhabit leaf litter in the natural forests.
Remarks. S. triprotrudens is allied to S. oni and S. protrudens, but it is separable from the latter two species by the aedeagal median lobe with its apical projections each longer (Fig. 52A),
and the endophallic copulatory tube triprotruded at apex (Fig. 52A).
As far as S. triprotrudens is concerned, it is difﬁcult to homologize the parts of its endophallus, because the median bands and expulsion hooks do not exist as in the common condition. At
ﬁrst glance, the paired large, membranous plates seem to be expulsion hooks, given their position(Fig. 52A). However, these sclerites are here identiﬁed as the basal bands of median bands,
mainly because the relative positions of the folded bands to these “membranous plates” are thesame as in S. oni (which is one of the closely allied species), although the dots are not found on
their surface.
Stenus protrudens Naomi & Watanabe(Fig. 53A–F)
Stenus triprotrudens Naomi & Watanabe, 2015: 105.
Type material examined. Holotype: ♂ (TUAA), Komanoyu Spa, Niigata Pref., 4 vii. 1963, Y.
Watanabe leg.
Distribution. Japan: Honshu (Niigata Pref.).
Redescription. Male: Body 4.6 mm (fore body 2.1 mm) in length, weakly shining. Headblack; pronotum, elytra and abdomen reddish brown to dark reddish brown; labrum, antennae
and legs also reddish brown to dark reddish brown. Head weakly concave, with a pair of longitudinal furrows; punctures round to elliptical, very dense, small, umbilicate. Pronotum with surface
uneven, with indistinct median longitudinal depression; punctures very dense, moderately large,coarse. Elytra with surface uneven, weakly depressed along the suture; punctures very dense,
moderately large, coarse. Tarsi each with 4th tarsomere strongly bilobed. Abdomen with punctures round to elliptical, dense, small in anterior segments, while punctures in posterior segments
very small, regular. Lateroventrites very thin only at the base of 4th segment, while missing in
the 5th to 6th; tergoventrite sutures existing.
Legs with femora thick; 4th ventrite posteromedially with a semicircular ﬂat area, which isvery shallowly emarginate; 5th ventrite posteromedially with a semicircular, very shallow
depression, which is very shallowly emarginate; 6th ventrite (Fig. 53D) modiﬁed as in the 5th,
but the depression a little deeper than that in the 5th; 7th ventrite (Fig. 53D) anteromedially witha ﬂat area, posteromedially with an ovoidal, moderately deep depression, which is shallowly
emarginate; 8th ventrite (Fig. 53E) posteromedially with a large, nearly V-shaped emargination;
9th tergum (Fig. 53F) with antecostal apophyses moderately long; 9th ventrite (Fig. 53C) irregularly serrate posteriorly, with macrosetae long, apicolateral teeth short, acutely pointed, apicolateral setae short; 10th tergum (Fig. 53F) weakly emarginate posteriorly. Aedeagal median lobe
(Fig. 53B) moderately broad, with a semicircular notch between apical projections, the apicalprojections each stout, relatively short, almost rounded apically. Endophallic median bands (Fig.
53B) moderately long, broad; expulsion hooks invisible; copulatory tube (Fig. 53A) robust, maintube very thick at base, narrowed apically, curved right at apex, with a pair of acutely pointed
teeth of different size at the ventral side near the apex, and also with a large ﬂap at the left side
near the apex. Parameres (Fig. 53B) each short, rounded apically; apical area hardly or weakly
swollen mesially, furnished mesially with 8 to 9 setae.

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Fig. 53. Stenus protrudens Naomi & Y. Watanabe (Komanoyu, Niigata). A, copulatory tube; B, aedeagus; C, 9th
ventrite of male; D, 6th and 7th ventrites of male; E, posterior part of 8th ventrite of male; F, 9th and 10th
terga of male. Scale 1: 0.2 mm for C, E, F, 0.1 mm for A; Scale 2: 0.2 mm for B; cale 3: 0.3 mm for D.

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Female: Unknown.
Biology and ecology. S. protrudens is a rare species; and it is only once collected from themountainous region of northern Chubu district, Honshu. The beetle inhabits leaf litter in the natural forests.
Remarks. S. protrudens is allied to S. oni and S. triprotrudens, but it is separable from the latter two species by the aedeagal median lobe with its apical projections each shorter, broader at
apex (Fig. 53B) and with a semicircular notch between the apical projections (Fig. 53B), and theendophallic copulatory tube with a large ﬂap at the left side near the apex (Fig. 53A).
Insertae sedis
S. dubitativus was ﬁrst described by Puthz (1993), based only on one female specimen from
Amami Is., Nansei Isls. in Japan. When having described the characters of the male in detail,Puthz (2001) adequately commented that this species does not belong to the previously recognized Stenus groups in Japan when seen from the viewpoint of the male genital structures, andalso that it just resembles them only superﬁcially. When seeing it taxonomically, what is then, in
actual fact, S. dubitativus? Let us here discuss it.
S. dubitativus is an elongate, chocolate brown to dark chocolate brown species (Fig. 105L).
This species has the Hypostenus-typed abdomen; and it is similar in habitus and coloration to themembers of the asyura-group (kasumi-subg.) and indubius-group. However, this species possesses the postabdomen (male and female) and aedeagus which are similar to those of somemembers of tenuimargo-group (see Puthz, 2011 and Lv et al., 2018), although the tenuimargogroup has the Hemistenus-typed abdomen. Namely, the 8th ventrite of male has the relatively
deep, triangular emargination (Fig. 53C); the gonocoxite of female has more or less falciform
apicolateral tooth (Fig. 53G); the aedeagal median lobe is simply narrowed apically and roundedat apex, with an elongate apical sclerotized area (Fig. 53D); the apical areas of parameres are
weakly but characteristically divergent laterally; and the paramere has its dorsal and ventral ﬂaps
(Fig. 53I) as in S. miwai Bernhauer, 1943, S. mithracifer Puthz, 2011, and S. perroti Puthz, 1981.
To which species-group, S. dubitativus belongs? It is certain that this species does not belong
to the indubius-group (having the gourd-shaped spermatheca in general; Fig. 81E), because thespermatheca of S. dubitativus is of the basic form (Fig. 53H). It seems that S. dubitativus does
not belong also to the asyura-group (having the aedeagus moderately broad to broad even at theapicolateral corners, and angulate, pointed or tricuspidate at apex), because the aedeagus of S.
dubitativus is relatively elongate, and becomes narrower apically, with its rounded apex (Fig.
53D). S. dubitativus may not belong also to the tenuimargo-group, because the body is smaller insize, with the Hypostenus-typed abdomen, and the antennae and legs are shorter. After all, S.
dubitativus seems to be a chimeric species which possesses the habitus of indubius-group or
kasumi-group and the aedeagus and postabdomen of tenuimargo-group. S. dubitativus is heretentatively classiﬁed into the asyura-group because it is very similar in habitus to the members of
its kasumi-subg. However, since it does not possess key characters of the asyura-group, it is here
taxonomically treated as incertae cedis.
Stenus dubitativus Puthz(Figs. 54A–I, 105L)
Stenus dubitativus Puthz, 1993: 181; Herman, 2001: 2165; Naomi & Puthz, 2013: 142.

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Type material examined. Holotype: ♂ (CBM), Mt. Yuwan, Amami Is., Kagoshima Pref., 5. v.
1987, S. Nomura leg.
Other material examined. [KYUSHU]: 5 ♂ 1 ♀, Hatsuno, Amami Is., Kagoshima Pref., 1.
iv. 1966, H. Nomura leg.; 2 ♂, same locality, 1. iv. 1966, T. Ito leg.; 1 ♀, Mt. Yuwan, Amami Is.,
Kagoshima Pref., 5. v. 1997, M. Yoshida leg.
Distribution. Japan: Kyushu (Amami Is.).
Redescription. Male and female: Body 4.7–5.4 mm (fore body 2.0–2.3 mm) in length, moderately shining, with antennae long, very thin, legs moderately long. Head black; pronotum, elytra and abdomen reddish or dark chocolate brown; labrum dark red; antennae and legs yellowish
brown to reddish brown. Head weakly concave, with a pair of indistinct (or thin) midlateral longitudinal furrows; punctures round to almost round, moderately dense to dense, moderately large.
Pronotum with surface weakly uneven, with indistinct median longitudinal furrow; puncturesround to elliptical, very dense, various in size, somewhat coarse. Elytra with surface weakly
uneven; punctures round to elliptical, very dense, large, sometimes coarse. Tarsi each with 4thtarsomere strongly bilobed, about half the length of 5th tarsomere. Abdomen with puncturesround, moderately dense to dense, small in anterior segments, while punctures in posterior segments sparse to moderately dense, very small, irregular. Lateroventrites and tergoventrite sutures
missing.
Male: Body a little more slender than in female; 7th ventrite (Fig. 54C) posteromedially witha subtriangular ﬂat area, which is very shallowly emarginate; 8th ventrite (Fig. 54C) posteriorly
with a V-shaped emargination; 9th tergum (Fig. 54A) with antecostal apophyses long; 9th ventrite (Fig. 54B) minutely serrate posteriorly, with macrosetae long, apicolateral teeth long,acutely pointed, apicolateral setae long; 10th tergum (Fig. 54A) very shallowly, minutely emarginate posteromedially. Aedeagal median lobe (Fig. 54D) elongate, uniformly narrowed apicallyfrom the parameral bases to the apex, narrow but almost rounded at apex; apical sclerotized area
(Fig. 54D) developed, distinctly longer than broad. Endophallic median bands (Fig. 54D) relatively short; lateral bands (Fig. 54D) moderately long, thin; expulsion hooks (Fig. 54F) separated
but connected by a C-shaped rod at the posteromesial corners of posterior plates, each hook slender, with anterior plate pointed apically, partially demarcated by an oblique ridge from posterior
plate; copulatory tube (Fig. 54E) with basal chamber ovoidal, main tube moderately curved near
the middle, with a pair of small dents at the mesial rims of ventral slit, and with basal tube thick,apical tube thin, having a low subtransparent lateral ﬂat. Parameres (Fig. 54D) each slender but
not reaching the apex of median lobe, rounded apically; apical area (Fig. 54I) relatively short,mesially with a dorsal and a ventral ﬂap, and furnished mesially with 9 setae of various lengths.
Female: Eighth ventrite almost rounded posteriorly; gonocoxites (Fig. 54G) toothed posteriorly, each with apicolateral tooth falciform, long, acutely pointed, apicolateral setae very long.
Spermatheca (Fig. 54H) with capsule very small, elongate; RT-duct long, thick at base, weakly
narrowed distally; duct long, almost tightly coiled, with the duct from the opening to 1st turnvery long, almost straight; basal valve short. Basal structure (Fig. 54H) elongate-conical, membranous basally.
Biology and ecology. S. dubitativus is distributed in the mountainous regions of Amami Is.
The beetles inhabit leaf litter in the natural forests.
Remarks. S. dubitativus is probably the sister species of S. sulcifer Oh & Cho, 2016 from
Korea, and it is separable from the latter species by the 8th ventrite of male posteromedially witha deeper emargination (Fig. 54C), the 9th ventrite of male with its posterior margin almost
straight (Fig. 54B), and the endophallic copulatory tube longer and broader (Fig. 54E).

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Fig. 54. Stenus dubitativus Puthz (Hatsuno, Amami Is.). A, 9th and 10th terga of male; B, 9th ventrite of male; C,
7th and 8th ventrites of male; D, aedeagus; E, copulatory tube; F, expulsion hooks; G, posterior part of gonocoxite; H, spermatheca; I, apical part of paramere. Scale 1: 0.2 mm for A, B, D, H, 0.1 mm for E, G, Scale 2:
0.3 mm for C; Scale 3: 0.05 mm for F, I.

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In the endophallic copulatory tube, there exist a pair of small dents at the mesial rims of its
ventral walls (Fig. 54E), just as in the case of Phanerota (Aleocharinae; Ashe, 1986; see also
Naomi, 2018). Thus, only the apical tube (i.e., apical thin part of the copulatory tube) will beinserted into the basal pouch of spermatheca, using the small dents as tools for ﬁxing the copulatory tube to the opening of spermatheca during copulation.
Species-group of S. indubius Sharp
The indubius-group is an Asian species-group of Stenus, whose species are at present distributed in the wide range of Asian region (Vietnam, Thailand, Laos, China, Taiwan, Korea andJapan) (Puthz, 2013a). It comprises 79 species as listed below. The peculiar gourd-shaped spermatheca was once considered the autapomorphy for the indubius-group (Puthz, 2001; Naomi,
2006), but the recent studies (Tang & Zhao, 2008; Puthz, 2017) showed that there exist some
exceptions in some species, in which the spermatheca is not gourd-shaped. For example, only thecapsule is very weakly swollen in the spermatheca of S. nibamontis Puthz, 2017, while the capsule forms a small sphere and the spermathecal duct just proximal to the spherical capsule isalmost simply thick (but not swollen laterally) in S. pectorifossatus Tang, 2008 (Tang & Zhao,
2008).
The indubius-group is similar in external structure and also closely related to the tenuimargogroup (Puthz, 2013a), which was ﬁrst established by Puthz (2011) based on several Oriental Stenus-species. The tenuimargo-group has the following diagnostic characters: Head with postocular region oblique; antennae very long; paraglossae oval; legs very long, with tarsi bilobed;
abdominal margination very narrow; 9th ventrite of male with long apicolateral teeth. It presently
comprises 29 species (Lv, 2018, 2018a; Puthz, 2018); and it is widely distributed in the Oriental
region from Nepal, India, Vietnam, Malaysia, Thailand, Myanmar, Laos to Taiwan and China(Puthz, 2013a). At present, the indubius-group is separable from the tenuimargo-group by thepeculiar structure of spermatheca described below (Puthz, 2013a).
Subgrouping of the indubius-group: The subgrouping of the indubius-group is here taken
up, together with brief descriptions on the research history related to it.
When Hromádka (1979) described several new Stenus-species from Japan, he used the nameindubius-group there; and Puthz (2001) ﬁrst characterized the indubius-group, and mentionedthat the structure of spermatheca should be considered a character of the indubius-group. Naomi(2006) revised taxonomically the Japanese species of indubius-group. Following Puthz, he characterized the indubius-group by considering the large spherical capsule and the large apicalchamber of spermatheca to be the major diagnostic characters of it. However, he excluded fromthe members of indubius-group, the Stenus-species with this diagnostic character in the cases
where they have the lateroventrites or distinct tergoventrite sutures in the 4th to 6th abdominal
segments. In other words, he did not regard the species of inimitabilis-subg. (see below) as themembers of indubius-group.
When Tang & Zhao (2008) studied some Chinese species of indubius-group, they newly
characterized the indubius-group, by recognizing the morphological diversities of abdomen inthis group. That is, there are two different forms of abdominal structure: one is the Hemistenustype, in which the tergoventrite sutures and / or lateroventrites exist in the 4th to 6th abdominal
segments (e.g., S. erlangshanus; S. hewenjiae Fig. 108K); and the other is the Hypostenus-type,in which both the tergoventrite sutures and lateroventrites are missing there (e.g., S. paradecens).
In this paper, we adopt the idea of indubius-group presented by Tang & Zhao (2008), who recog-

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nized two different forms of abdominal structure. The species with the lateroventrites or tergoventrite sutures are here newly grouped into the inimitabilis-subgroup within the indubius-group,
given their possession of the diagnostic characters mentioned at the beginning of the section
inimitabilis-subg. Thus, at present the indubius-group consists of two subgroups: inimitabilissubg. (37 species) and indubius-subg. (39 species), as listed below.
Diagnostic characters of the indubius-group: Body elongate, chocolate brown to dark
chocolate brown or black (Fig. 108D), but elytra each without (Fig. 108D) or with an orange spotin some species (e.g., S. shibatai; Fig. 108 L); brachypterous; tarsi each with 4th tarsomere
strongly or weakly bifurcate; lateroventrites existing, or lateroventrites missing but tergoventrite
sutures existing, or both lateroventrites and tergoventrite sutures missing in 4th to 6th abdominal
segments. Male: Body often more or less smaller than in female; 9th ventrite with macrosetae
and apicolateral teeth (Figs. 55C, 59A); endophallic copulatory tube simple (e.g., thin, slender,
attenuate; Fig. 60B), but its main tube rarely modiﬁed with a division of basal and apical tubes(Fig. 73B), or to form an elongate S-shaped rod (Fig. 82B), etc. Female: Gonocoxite serrate posteriorly, with apicolateral tooth (Figs. 55G, 60E); spermatheca usually gourd-shaped (i.e., both
capsule and apical chamber large, spherical or subspherical; Figs. 55E, 59F), but in some cases
the capsule only developed, (sub)spherical (Fig. 56E), or both capsule and apical chamber small,not (sub)spherical nor swollen laterally (e.g., S. nibamontis).
A list of the species of S. indubius groupinimitabilis-subgroupexplanipennis Rougemont, 1987 Distribution: Thailand (Chiang Mai)
sausai Hromádka, 2001 Distribution: Laos (Bolikhamsai)
vietnamensis Puthz, 1968 Distribution: Vietnam (Ninh-Bingh), China (Hainan), Taiwan (Kaohsiung, Nantou, Chiai)＝ shibataianus Puthz, 2011
electristigma Puthz, 2011 Distribution: Taiwan (Taichiung, Hualien)
shibatai Puthz, 2011 Distribution: Taiwan (Taoyuan, Nantou)
shibataiellus Puthz, 2011 Distribution: Taiwan (Nantou)
taiyangshanus Tang & Li, 2012 Distribution: China (Guangdong)
huapingensis Tang, Li & Huang, 2012 Distribution: China (Guangxi)
absconditus Hu & Tang, 2018 Distribution: China (Guizhou)
hui Tang & Puthz, 2009 Distribution: China (Shaanxi)
scabripunctus Puthz, 2017 Distribution: China (Shaanxi)
dabacola Puthz, 2017 Distribution: China (Shaanxi)
dabaensis Puthz, 2017 Distribution: China (Shaanxi)
pectorifossatus Tang, 2008 Distribution: China (Sichuan)
erlangshanus Tang, 2008 Distribution: China (Sichuan)
zhuxiaoyui Tang, 2008 Distribution: China (Sichuan)
hewenjiae Tang & Li, 2012 Distribution: China (Sichuan)
erlanganus Puthz, 2017 Distribution: China (Sichuan)
nibamontis Puthz, 2017 Distribution: China (Sichuan)
xilingshanus Puthz, 2017 Distribution: China (Sichuan)luojiensis Puthz, 2017 Distribution: China (Sichuan)
trigaulti Puthz, 2018 Distribution: China (Sichuan)

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lizipingus Hu & Tang, 2018 Distribution: China (Sichuan)
fuscus Hu & Tang, 2018 Distribution: China (Sichuan)
cangshanus Tang & Li, 2012 Distribution: China (Yunnan)
doryphorus Puthz, 2017 Distribution: China (Yunnan)habashanus Puthz, 2017 Distribution: China (Yunnan)
aequabilifrons Puthz, 2017 Distribution: China (Yunnan)
hajeki Puthz, 2017 Distribution: China (Yunnan)
zhemoshanus Puthz, 2017 Distribution: China (Yunnan)zhongdianus Puthz, 2017 Distribution: China (Yunnan)
insperabilis Puthz, 2017 Distribution: China (Yunnan)
xueshanus Puthz, 2017 Distribution: China (Yunnan)
tumoripennis Puthz, 2017 Distribution: China (Yunnan)
tumidulipennis Puthz, 2017 Distribution: China (Yunnan)
tonghanggangus Tang, Puthz & Yue, 2016 Distribution: China (Zhejiang)
tianmushanus Tang, Puthz & Yue, 2016 Distribution: China (Zhejiang)
autumnalis Naomi, 1997a Distribution: Japan (Shikoku)
unzenmontis Naomi & Puthz, 1996 Distribution: Japan (Kyushu)
inimitabilis Puthz, 1993a Distribution: Japan (Shikoku, Kyushu)
siphonifer Naomi, 2015b Distribution: Japan (Honshu)
indubius-subgroup
guniujiangensis Tang, Li & Zhao, 2005 Distribution: China (Anhui)paradecens Tang, Li & Zhao, 2005 Distribution: China (Anhui)jaoluopingus Hu & Tang, 2018 Distribution: China (Anhui)yinziweii Tang & Li, 2012 Distribution: China (Guizhou)
zhaiyanbini Tang & Li, 2012 Distribution: China (Guizhou)
micangmontium Puthz, 2017 Distribution: China (Shaanxi)
detestabilis Puthz, 2017 Distribution: China (Shaanxi)
detestatus Puthz, 2017 Distribution: China (Shaanxi)
impressicollis Puthz, 2017 Distribution: China (Sichuan)luojimontis Puthz, 2017 Distribution: China (Sichuan)zhujianqingi Tang, Li & Huang, 2012 Distribution: China (Zhejiang)
curvus Oh & Cho, 2016 Distribution: Korea (Gyeongnam, Jeonbuk, Jeonnam)
tenuiculus Oh & Cho, 2016 Distribution: Korea (Gyeongnam)
unciformis Oh & Cho, 2016 Distribution: Korea (Gyeongnam, Jeonnam)
obesus Oh & Cho, 2016 Distribution: Korea (Jeonbuk)
serratus Naomi, 2006 Distribution: Japan (Honshu)
sadoensis Naomi, 2006 Distribution: Japan (Honshu)
subserratus Naomi, 2006 Distribution: Japan (Honshu)
takane Naomi, 1987 Distribution: Japan (Honshu)
unicoloratus Naomi & Puthz, 2006 Distribution: Japan (Honshu)
tohokuensis Naomi & Puthz, 2006 Distribution: Japan (Honshu)
campaniformis Naomi, Nomura & Puthz sp. nov. Distribution: Japan (Honshu)
naomii Puthz, 2001 Distribution: Japan (Honshu)
tuberascens Naomi, Nomura & Puthz sp. nov. Distribution: Japan (Honshu)
acerrimus Naomi, 2006 Distribution: Japan (Honshu)

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cucumeroides Naomi & Puthz, 2006 Distribution: Japan (Honshu)
unagi Hromádka, 1979 Distribution: Japan (Honshu)＝ ookami Hromádka, 1979
fugu Hromádka, 1979 Distribution: Japan (Honshu)＝ sakana Hromádka, 1979
ukon Naomi & Puthz, 2006 Distribution: Japan (Honshu)
kyushuensis Naomi & Puthz, 2006 Distribution: Japan (Kyushu)
tanuki Hromádka, 1979 Distribution: Japan (Honshu)＝ wakayamanus Puthz, 2001ahypovelox Naomi & Puthz, 2006 Distribution: Japan (Shikoku)
sawadai Hromádka, 1979 Distribution: Japan (Honshu)
kishimotoi Naomi & Puthz, 2006 Distribution: Japan (Honshu)
yokozekii Naomi, 2006 Distribution: Japan (Honshu)
tateoi Naomi, 2006 Distribution: Japan (Honshu)
ohishii Naomi, 1987 Distribution: Japan (Honshu: Awaji Is., Shikoku, Kyushu)
fusciceps Naomi, 2006 Distribution: Japan (Shikoku)
indubius Sharp, 1889 Distribution: Japan (Honshu)＝ vernalis Naomi, 1997
kiyosumiensis Naomi & Takeda, 1991 Distribution: Japan (Honshu)
Japanese fauna of the indubius-group
As far as the Japanese fauna is concerned, the indubius-group comprises 29 species, which
are divided into 2 subgroups: S. inimitabilis-subg. (4 species) and S. indubius-subg. (25 species).
All species are indigenous to the Japanese Archipelago.
Key to the subgroups of the indubius-group
1(2)

2(1)

Pronotum with a median longitudinal furrow on the surface; lateroventrites existing, or
distinct tergoventrite sutures existing in 4th to 6th abdominal segments .............................
.........................................................................................................S. inimitabilis-subgroup
Pronotum without median longitudinal furrow on the surface; both lateroventrites and tergoventrite sutures usually missing in 4th to 6th abdominal segments (but if the tergoventrite sutures exist they are very obsolete or very thin) ........................ S. indubius-subgroup
The inimitabilis-subgroup

The inimitabilis-subg. presently comprises 4 species in Japan, which is characterized as follows:
Diagnostic characters of the inimitabilis-subgroup: Antennae relatively short to moderately long, thin (Fig. 106A); pronotum with a median longitudinal furrow on the surface; elytral
surface usually strongly uneven, punctures subrugose; tarsi each with 4th tarsomere weakly
bilobed, with its furcate ventral lobes short; lateroventrites existing, or lateroventrites missing but
distinct tergoventrite sutures existing in 4th to 6th abdominal segments.

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Key to the Japanese species of the inimitabilis-subgroup
1(4)
2(3)

3(2)

4(1)
5(6)

6(5)

Lateroventrites existing, very narrow in 4th to 6th abdominal segments.
Male: Aedeagal median lobe simply pointed apicomedially (Fig. 55B); endophallic
expulsion hook almost ear-shaped (Fig. 55H). Female: Spermatheca with capsule almost
spherical (Fig. 55E)............................................................................. S. autumnalis Naomi
Male: Aedeagal median lobe tricuspidate, with the short median cusp (Fig. 57C); endophallic expulsion hook subtriangular (Fig. 57G). Female: Spermatheca with capsule elongate-ovoidal (Fig. 57E) .........................................................................S. inimitabilis Puthz
Lateroventrites missing but tergoventrite sutures distinct in 4th to 6th abdominal segments.
Male: Aedeagal median lobe simply pointed apicomedially (Fig. 56F); copulatory tube
apically with a ﬂagellum (Fig. 56H); paramere with apical area longer (Fig. 56F)............................................................................................. S. unzenmontis Naomi & Puthz
Male: Aedeagal median lobe obtusely angulate apicomedially (Fig. 58C); copulatory tube
apically with a ﬂagellum-like (elongate and membranous) tube (Fig. 58C); paramere withapical area shorter (Fig. 58C)................................................................ S. siphonifer Naomi
Stenus autumnalis Naomi(Figs. 55A–H, 106A)

Stenus autumnalis Naomi, 1997a: 15; Herman, 2001: 2076; Naomi & Puthz, 2013: 142.
Type material examined. Holotype: ♂ (CBM), Mt. Kotsu, Yamakawa-cho, Tokushima Pref.,31. x. 1965, M. Sakai leg.; 1 ♂1 ♀ (cN), same locality, 10. x. 1975, M. Yoshida leg.; 1 ♂ (cN),
Mt. Maruzasa, Tokushima Pref., 11. vi. 1972, M. Yoshida leg.; 1 ♂ (cN), Mt. Takashiro,
Tokushima Pref., 3. v. 1978, M. Yoshida leg.; 1 ♂ (cN), Mt. Tsurugi, Tokushima Pref., 3. v. 1969,
M. Yoshida leg.; 1 ♂ (cN), same locality, 20. vii. 1972, M. Yoshida leg.
Other material examined. [SHIKOKU]: 1 ♀, Mt. Tsurugi, Tokushima Pref., 15–17. x. 1980,
S. Naomi leg.; 1 ♀, Minokoshi, Tokushima Pref. (Awa), 1. viii. 1960, T. Shibata leg.
Distribution. Japan: Shikoku (Tokushima Pref.).
Redescription. Male and female: Body 4.1–4.8 mm (fore body 1.8–2.1 mm) in length, moderately shining, with antennae relatively short. Head and abdomen dark red to black; pronotum andelytra dark red; labrum dark red; antennae and legs yellowish brown to reddish brown. Headshallowly concave with a pair of midlateral longitudinal furrows; punctures round, sparse tomoderately dense, various in size. Pronotum with surface uneven, with indistinct, median longitudinal furrow, centrally with a small impunctate area; punctures very dense, strongly rugose.
Elytra with surface rather uneven; punctures very dense, strongly rugose. Tarsi each with 4th tarsomere not bilobed. Abdomen with punctures round to elliptical, moderately dense, small inanterior segments, while puncture in 7th and 8th segments elliptical, sparse, very small. Lateroventrites horizontal in position, very narrow, sparsely, ﬁnely punctate.
Male: Sixth and 7th ventrites (Fig. 55F) each posteromedially with a very shallow, subovoidal depression or ﬂat area; 8th ventrite (Fig. 55F) posteromedially with a small, subtriangularemargination; 9th tergum (Fig. 55A) with antecostal apophyses moderately long, thin; 9th ventrite (Fig. 55C) minutely serrate posteriorly, with macrosetae moderately long, apicolateral teeth
short, pointed, apicolateral setae moderately long; 10th tergum (Fig. 55A) shallowly emarginate

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Fig. 55. Stenus autumnalis Naomi (A, D, F, H, Maruzasa, Tokushima; B, C, E, G, Tsurugi, Yokushima). A, 9th
and 10th terga of male; B, aedeagus; C, 9th ventrite of male; D, copulatory tube; E, spermatheca; F, 7th and8th ventrites of male; G, posterior part of gonocoxite; H, expulsion hooks. Scale 1: 0.2 mm for A, 0.1 mm for
D, E, G, H; Scale 2: 0.1 mm for B, C; Scale 3: 0.3 mm for F.

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posteriorly. Aedeagal median lobe (Fig. 55B) broad, broadest and angulate at apicolateral corner,
simply pointed apically; apical sclerotized area (Fig. 55B) weakly developed, almost V-shaped.
Endophallic dorsal membrane (Fig. 55B) subovoidal; median bands (Fig. 55B) very short; explusion hooks (Fig. 55H) widely separated, each almost ear-shaped, with anterior plate pointed anteriorly, posterior plate rounded posteriorly; copulatory tube (Fig. 55D) very slender, with basal
chamber small, main tube very thin, baculiform, bifurcate at apical part. Parameres (Fig. 55B)
thin, each reaching the anterolateral corner of median lobe; apical area very short, hardly swollen
mesially, furnished mesially with 5–6 setae of various length.
Female: Eighth ventrite almost rounded posteriorly; gonocoxites (Fig. 55G) toothed posteriorly, each with apicolateral tooth very long, acutely pointed, apicolateral teeth long. Spermatheca(Fig. 55E) with capsule spherical, large; apical chamber pyriform, narrower than capsule; ductvery short with two turns, the duct from the base to 1st turn membranous; gland large, with its
opening near the base of apical chamber; basal sclerorized duct short. Basal structure (Fig. 55E)
funnel-shaped, membranous.
Biology and Ecology. S. autumnalis is distributed in the mountainous regions of Shikoku.
The beetles inhabit leaf litter heaped in the natural forests.
Remarks. S. autumnalis is allied to S. unzenmontis, and S. inimitabilis, but it is separablefrom the latter two species by the endophallic expulsion hook almost ear-shaped (Fig. 55H).
Stenus unzenmontis Naomi & Puthz(Figs. 56A–I, 106B)
Stenus unzenmontis Naomi & Puthz, 1996: 156; Herman, 2001: 2427; Naomi & Puthz, 2013: 142.
Type material examined. Holotype: ♀ (CBM), Mt. Unzen, Shimabara, Nagasaki Pref., 10. vi.
1980, S. Imasaka leg. Paratype, 1 ♀ (CBM), same data as holotype.
Other material examined. [KYUSHU]: 1 ♂ (cN), Mt. Seira, Takeo City, Saga Pref., 5. iv.
1983, S. Nomura leg.; 1 ♀ (cN), Hiratani Spa., Mt. Keigadake, Kashima City, Saga Pref., 2. vi.
1981, S. Imasaka leg.
Distribution. Japan: Kyushu (Nagasaki and Saga Prefs.).
Redescription. Male and female: Body 3.7–4.3 mm (fore body 1.9–2.1 mm) in length, moderately shining, with antennae relatively short. Body dark red to black; labrum dark brown to
black; antennae and legs yellowish brown to reddish brown. Head shallowly concave with a pairof midlateral longitudinal furrows; punctures round, moderately dense to dense, various in size.
Pronotum with surface uneven, with indistinct median longitudinal furrow; punctures very dense,
strongly coarse, subrugose. Elytra with surface strongly uneven; punctures very dense, strongly
coarse, subrugose. Tarsi each with 4th tarsomere bilobed, each ventral lobe short. Abdomen with
punctures round to elliptical, moderately dense to dense, small in anterior segments, while puncture in posterior segments round to elliptical, sparse, very small. Lateroventrites missing; tergoventrite sutures distinct.
Male: Seventh ventrite (Fig. 56C) posteromedially with a subtriangular, very shallow depression; 8th ventrite (Fig. 56C) posteromedially with an arcuate, relatively broad emargination; 9th
tergum (Fig. 56A) with antecostal apophyses moderately long, thin; 9th ventrite (Fig. 56B) serrate posteriorly, with macrosetae long, apicolateral teeth acutely pointed, apicolateral setae moderately long; 10th tergum (Fig. 56A) very shallowly emarginate posteriorly. Aedeagal median
lobe (Fig. 56F) moderately broad, broadest and angulate at apicolateral corner, pointed at apex;

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Fig. 56. Stenus unzenmontis Naomi & Puthz (A–C, F, H, I, Seira, Saga; D, Hiratani, Saga; E, G, Unzen, Nagasaki). A, 9th and 10th terga of male; B, 9th ventrite of male; C, 7th and 8th ventrites of male; D, E, spermatheca; F, aedeagus; G, posterior part of gonocoxite; H, apical part of copulatory tube; I, expulsion hooks. Scale
1: 0.2 mm for A, B, F, 0.1 mm for D, H, I; Scale 2: 0.3 mm for C; Scale 3: 0.1 mm for E; Scale 4: 0.1 mm for G.

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apical sclerotized area (Fig. 56F) weakly developed, almost V-shaped. Endophallic median bands(Fig. 56F) each with basal band subfusiform, short, broad, folded band moderately long, narrow;
explusion hooks (Fig. 56I) separated, each with anterior plate narrowed anteriorly, pointed at tip,
posterior plate mesially angulate at the middle; copulatory tube (Fig. 56F, H) very slender, withbasal chamber ovoidal, main tube very long, slender, attenuate, apically with a long, ﬂagellum.
Parameres (Fig. 56F) having stem straight, pointed at apex; apical area long, swollen laterally inthe basal 1/2, then strongly narrowed toward apex, furnished mesially with 4–6 moderately longsetae along ventral margin, and with 3 short setae along dorsal margin.
Female: Eighth ventrite posteromedially minutely pointed; gonocoxites (Fig. 56G) toothed
posteriorly, each with apicolateral tooth very long, pointed, apicolateral teeth long. Spermatheca(Fig. 56D, E) with capsule ovoidal to subspherical, large; apical chamber pyriform (Fig. 56D) or
missing (Fig. 56E); duct moderately thick to thick, short with two turns; gland with its opening
near the base of (or a little proximal from) apical chamber.
Biology and Ecology. S. unzenmontis is distributed in the mountainous regions of the northwestern part of Kyushu. The beetles inhabit leaf litter heaped in the natural forests.
Remarks. S. unzenmontis is allied to S. inimitabilis, but it is separable from the latter species
by the abdomen with its lateroventrites missing (i.e., almost fused with the ventrite) and theaedeagal median lobe simply pointed apically (Fig. 56F).
The distributional range of this species is restricted in the northwestern part of Kyushu, but
the spermatheca shows the infraspeciﬁc variations regarding the structures of capsule and duct.
Namely, in a female of Hiratani (Fig. 56D), the capsule is distinctly constricted at base so that thecapsule and collum are clearly demarcated by the constriction; and the apical chamber is large
and pyriform. On the other hand, in a female of Unzen (Fig. 56E), the capsule is large but notconstricted at base so that the capsule cannot be distinctly demarcated from the collum; and theapical chamber is missing.
Stenus inimitabilis Puthz(Figs. 57A–G, 106C)
Stenus inimitabilis Puthz, 1993a: 162; Herman, 2001: 2231; Naomi & Puthz, 2013: 142.
Type material examined. Holotype: ♂ (AACO), Omogo Valley, Ehime Pref., 18–25. viii.
1980, S. Peck leg.
Other material examined. [SHIKOKU]: 1 ♂ (cN), Omogo Valley, Ehime Pref., 25. v. 1969,
M. Sakai leg.; 1 ♂ (cN), same locality, 18–19. v. 1968, M. Sakai leg.; 2 ♀ (cN), same locality, 29.
v. 1977, A. Oda leg.; 1 ♂ (cN), same locality, 9. x. 1953, T. Nakane leg.; 1 ♂ (cN), Mt. Odami,
Ehime Pref., 15. vii. 1993, E. Yamamoto leg.; 1 ♀ (cN), Mt. Ishizuchi, 16. vi. 1981, S. Naomi
leg.; 1 ♂ (cN), Ookawa Vil., Kochi Pref., 27. v. 2007, T. Miyata leg.; 1 ♀ (cN), Takaita, Monobe
Vil., Tochi Pref., 23. vi. 2002, T. Miyata leg. [KYUSHU]: 1 ♂ (cN), Kokonoe-cho, Ooita Pref.,10. xi. 2007, S. Imasaka leg.
Distribution. Japan: Shikoku (Ehime and Kochi Prefs.) and Kyushu (Ohita Pref.).
Redescription. Male and female: Body 3.3–4.5 mm (fore body 1.9–2.1 mm) in length, moderately shining, with antennae relatively short to moderately long. Head black; pronotum, elytra
and abdomen dark red; labrum dark brown to black; antennae and legs yellowish brown to reddish brown. Head shallowly concave with a pair of midlteral longitudinal furrows; puncturesround, sparse to moderately dense, various in size. Pronotum with surface uneven, with indistinct

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Fig. 57. Stenus inimitabilis Puthz (Omogo, Ehime). A, 9th and 10th terga of male; B, 6th to 8th ventrites of male;C, aedeagus; D, 9th ventrite of male; E, spermatheca; F, posterior part of gonocoxite; G, expulsion hooks.
Scale 1: 0.2 mm for A, C, D, 0.1 mm for E–G; Scale 2: 0.3 mm for B.

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median longitudinal furrow; punctures very dense, coarse, subrugose. Elytra with surface
strongly uneven; punctures very dense, strongly coarse, subrugose. Tarsi each with 4th tarsomere
weakly bilobed, each ventral lobe short. Abdomen with punctures round to elliptical, moderately
dense to dense, small in anterior segments, while puncture in posterior segments elliptical, moderately dense, small, regular. Lateroventrites each narrow, vaguely furrowed posteriorly.
Male: Fourth and 5th ventrites each posteromedially with a small ﬂat area, which is very
weakly emarginate posteriorly; 6th ventrite (Fig. 57B) posteromedially with a bell-shaped, ﬂatarea, which is weakly emarginate posteriorly; 7th ventrite (Fig. 57B) posteromedially with alarge, very shallow depression; 8th ventrite (Fig. 57B) posteromedially with a medium-sized
emargination; 9th tergum (Fig. 57A) with antecostal apophyses long, thin; 9th ventrite (Fig. 57D)
weakly serrate posteriorly, with macrosetae long, apicolateral teeth acutely pointed, apicolateral
setae moderately long; 10th tergum (Fig. 57A) very shallowly emarginate posteromedially.
Aedeagal median lobe (Fig. 57C) broad, angulate apicolaterally, vaguely tricuspidate at apex;
apical sclerotized area (Fig. 57C) weakly developed, with median cusp short, pointed, lateralcusps each existing only as an obtuse angulation. Endophallic median bands (Fig. 57C) relatively
short, broad; lateral bands (Fig. 57C) short, moderately broad; explusion hooks (Fig. 57G) connected at the mesial corners of posterior plates (or narrowly separated), each with anterior plate
pointed anteriorly, demarcated by a suture from posterior plate, the posterior plate subtriangular;
copulatory tube (Fig. 57C) very long, with basal chamber elongate, main tube very long, attenuate, thick basely, apically with a long, whip-like, submembranous tube. Parameres (Fig. 57C)
each straight, acutely pointed at apex; apical area long, furnished mesially with 7–8 short setae.
Female: Eighth ventrite obtusely angulate posteromedially; gonocoxites (Fig. 57F) toothed
posteriorly, each with apicolateral tooth long, acutely pointed, apicolateral teeth long. Spermatheca (Fig. 57E) with capsule elongate-ovoidal, large to very large; apical chamber pyriform,
large; duct membranous proximally, short with two turns; gland with its opening a little proximal
from apical chamber.
Biology and Ecology. S. inimitabilis is distributed in the mountainous regions of the western
Shikoku and the northeastern Kyushu. The beetles inhabit leaf litter heaped in the natural forests.
Remarks. S. inimitabilis is allied to S. unzenmontis, but it is separable from the latter species
by the lateroventrites narrow but distinctly existing, and the aedeagal median lobe with its apicalsclerotized area vaguely tricuspidate at apex (Fig. 57C).
Stenus siphonifer Naomi(Figs. 58A–G, 106D)
Stenus siphonifer Naomi, 2015b: 39.
Type material examined. Holotype: ♂ (CBM), Mt. Minamimata, Ohuchiyama, Mie Pref., 4.
xi. 1996, K. Kanno leg. Paratype: 1 ♂ (cN), Ohdaigahara, Yoshino-gun, Nara Pref., 31. vii. 1958,
T. Shibata leg.
Other material examined. [HONSHU]: 1 ♀, Ohdaigahara, Yoshino-gun, Nara Pref., 5. viii.
2006, Y. Matsuda leg.
Distribution. Japan: Honshu (Mie and Nara Prefs.).
Redescription. Male and female: Body 4.8–4.9 mm (fore body 2.3–2.4 mm) in length, weakly
shining, with antennae moderately long. Head black; pronotum, elytra and abdomen dark brown;
labrum black; antennae and legs reddish brown. Head shallowly concave, with a pair of longitu-

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Fig. 58. Stenus siphonifer Naomi (A, B, D–F: Ohdaigahara, Nara; C, G: Ouchiyama, Mie). A, gonocoxite; B, 9th
and 10th terga of male; C, aedeagus; D, 9th ventrite of male; E, spermatheca; F, posterior part of 8th ventriteof male; G, expulsion hooks. Scale 1: 0.2 mm for A, C, 0.1 mm for E, G; Scale 2: 0.2 mm for B, D, F.

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dinal furrows; punctures round, dense. Pronotum with surface slightly uneven, centrally with an
indistinct, elongate fovea; punctures very dense, coarse. Elytra with surface rather uneven, moreor less elevated along suture; punctures very dense, coarse. Tarsi each with 4th tarsomere moderately bilobed. Abdomen with punctures round to elliptical, dense, small in anterior segments,
while punctures in posterior segments sparse, very small, regular. Lateroventrites missing; tergoventrite sutures distinct.
Male: Sixth ventrite posteromedially with a semicircular ﬂat area; 7th ventrite medially witha very shallow, elongate-ovoidal depression, which is very shallowly emarginate; 8th ventrite
posteromedially with an arcuate (Fig. 58F) or nearly V-shaped emargination; 9th tergum (Fig.
58B) with antecostal apophyses very long, thin; 9th ventrite (Fig. 58D) elongate, minutely serrate
posteriorly, with macrosetae moderately long, apicolateral teeth acutely pointed, apicolateral
setae moderately long; 10th tergum (Fig. 58B) very shallowly emarginate. Aedeagal median lobe
(Fig. 58C) broad, broadest and gently rounded apicolaterally, nearly rounded posteriorly (orobtusely angulate apicomedially); apical sclerotized area (Fig. 58C) broad, anteromedially with adeep, semicircular emargination. Endophallic median bands (Fig. 58C) moderately long andbroad; lateral bands (Fig. 58C) very broad, each without small dots on the surface; expulsion
hooks (Fig. 58G) each almost elongate-triangular, with the anterior plate pointed anteriorly,
demarcated by a transverse suture from posterior plate, the posterior plate pointed posteriorly;
copulatory tube (Fig. 58C) very long, with basal chamber narrow, main tube very long, slender,
attenuate, straight, apically with an elongate membranous tube. Parameres (Fig. 58C) thin, eachweakly incurved, acutely pointed at apex; apical area very short, hardly swollen mesially, furnished mesially with 8–9 short setae.
Female: Eighth ventrite obtusely angulate posteromedially; gonocoxites (Fig. 58A) toothed
posteriorly, each with apicolateral tooth long, acutely pointed, apicolateral teeth moderately long.
Spermatheca (Fig. 58E) with capsule ovoidal, very large; apical chamber almost pyriform; duct
short with two turns, membranous on its way; basal duct not sclerotized; gland with its opening alittle proximal from apical chamber.
Biology and Ecology. S. siphonifer is a rare species; and it is distributed in the mountainous
regions of Kinki district, Honshu. The beetles inhabit leaf litter in the natural forests.
Remarks. S. siphonifer is allied to S. inimitabilis and S. unzenmontis, but it is separable fromthe latter two species by the aedeagal median lobe nearly rounded posteriorly (Fig. 58C).
The indubius-subgroup
The indubius-subg. presently comprises the 25 species in Japan, which is characterized asfollows:
Diagnostic characters of the indubius-subgroup: Antennae usually moderately long (butrarely relatively short), thin to very thin (Fig. 106E); pronotum without any median longitudinalfurrow on the surface; elytral surface usually almost even to weakly uneven, punctures more orless distinct, sometimes coarse (but not subrugose); tarsi each with 4th tarsomere distinctly
bilobed, each lobe about 2/3 the length of 5th tarsomere; both lateroventrites and tergo-ventrite
sutures completely missing or tergoventrite sutures only existing (very thin or obsolete) in 4th to
6th abdominal segments.

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Key to the Japanese species of the indubius-subgroup
1(6)
2(5)

Male: Eighth ventrite posteriorly with a larger and broader emargination.
Male: Aedeagal median lobe uniformly rounded laterally, with apicolateral corners angulate; endophallic copulatory tube with anterior plate not rounded apically.
3(4) Male: Aedeagal median lobe with apical sclerotized area smaller (Fig. 70B); endophallic
expulsion hook with anterior plate simply pointed anteriorly, fused with posterior plate(Fig. 69I). Female: Spermathecal duct with the most anterior part usually extending anteriorly beyond the apical margin of apical chamber (Fig. 70G).............. S. unagi Hromádka
4(3) Male: Aedeagal median lobe with apical sclerotized area larger (Fig. 71B); endophallic
expulsion hook with anterior plate minutely hooked anteromsially, demarcated by suturefrom posterior plate (Fig. 71I). Female: Spermathecal duct with the most anterior part notextending anteriorly beyond the apical margin of apical chamber (Fig. 71G) .....................
.................................................................................................................. S. fugu Hromádka
5(2) Male: Aedeagal median lobe weakly swollen mediolaterally, with apicolateral corners
rounded (Fig. 72B); endophallic copulatory tube with anterior plate rounded apically(Fig. 72H)........................................................................................ S. ukon Naomi & Puthz
6(1) Male: Eighth ventrite posteromedially with a smaller and narrower emargination.
7(12) Male & female: Tenth tergum with a distinct apicomedian tooth or projection.
8(9) Male: Aedeagal median lobe uniformly rounded apically, with apical sclerotized area uniformly sclerotized (Fig. 65C); paramere thicker (Fig. 65C) .................................................
.............................................................S. campaniformis Naomi, Nomura & Puthz sp. nov.
9(8) Male: Aedeagal median lobe with an apicomedian projection; paramere thinner.
10(11) Male: Aedeagal median lobe with apical sclerotized area distinctly longer, having a
median-longitudinal subtransparent area, and an acute, small median cusp (Fig. 66B) .......
....................................................................................................................... S. naomi Puthz
11(10) Male: Aedeagal median lobe with apical sclerotized area distinctly shorter, solid medially,
having a relatively broad, rounded hump at apex (Fig. 67B) ...............................................
..................................................................S. tuberascens Naomi, Nomura & Puthz sp. nov.
12(7) Male & female: Tenth tergum more or less rounded (entire), or only bluntly angulate, oronly weakly emarginate posteriorly.
13(34) Male: Aedeagal median lobe of narrow form, usually more or less narrowed apicallybehind the middle.
14(29) Male: Aedeagal median lobe more or less pointed apicomedially.
15(16) Male: Aedeagal paramere shorter, not reaching posteriorly the apex of median lobe, withapical area much shorter (Fig. 61B) ....................................................S. subserratus Naomi
16(15) Male: Aedeagal paramere longer, usually a little extending posteriorly beyond the apex ofmedian lobe, with apical area much longer.
17(20) Male: Aedeagal median lobe more strongly narrowed toward apex in about apical 1/2,
with apical sclerotized area weakly rounded at anterior margin.
18(19) Male: Endophallic copulatory tube weakly swollen at apex (Fig. 59H). Female: Spermatheca with capsule larger, spherical; apical chamber much smaller (Fig. 59F) ....................
.................................................................................................................. S. serratus Naomi
19(18) Male: Endophallic copulatory tube attenuate, simply aciculate at apex (Fig. 59B).
Female: Spermatheca with capsule smaller, ovoidal; apical chamber much larger (Fig.
60G) .......................................................................................................S. sadoensis Naomi144

Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

20(17) Male: Aedeagal median lobe less strongly narrowed toward apex in about apical 1/2, withapical sclerotized area bisinuate or arcuate at anterior margin.
21(24) Male: Eighth ventrite posteromedially with a deeper emargination; aedeagal median lobe
with apicolateral corner uniformly rounded. Female: Spermathecal duct more strongly
stiff and sclerotized.
22(23) Male: Aedeagal median lobe with apical sclerotized area shorter (Fig. 68B). Female:
Spermathecal duct without any strong constriction on its way (Fig. 68G) ...........................
............................................................................................................... S. acerrimus Naomi
23(22) Male: Aedeagal median lobe with apical sclerotized area longer (Fig. 69B). Female: Spermathecal duct with a very strong constriction on its way (Fig. 69F) ....................................
........................................................................................... S. cucumeroides Naomi & Puthz
24(21) Male: Eighth ventrite posteromedially with a shallower emargination; aedeagal median
lobe with apicolateral corner more or less obtusely angulate. Female: Spermathecal ductless strongly stiff and sclerotized.
25(28) Male: Aedeagal median lobe with apicolateral corners more distinctly angulate. Female:
Spermathecal tube very short to short, thicker, with 2 distinct turns.
26(27) Male: Aedeagal median lobe narrower (Fig. 73B); endophallic copulatory tube comprising the basal (very thick) tube and the apical (apically curved) tube (Fig. 73B). Female:
Spermatheca with capsule larger; duct longer (Fig. 73F) ....S. kyushuensis Naomi & Puthz
27(26) Male: Aedeagal median lobe broader (Fig. 74B); endophallic copulatory tube not divided
into the basal and apical tubes (entirely very thin, simply attenuate) (Fig. 74B). Female:spermatheca with capsule smaller; duct shorter (Fig. 74E) ................. S. tanuki Hromádka
28(25) Male: Aedeagal median lobe with its apicolateral corners less distinctly angulate (Fig.
75B). Female: Spermathecal tube very long, thinner and almost tightly coiled (Fig. 75F)..
.................................................................................................S. hypovelox Naomi & Puthz
29(14) Male: Aedeagal median lobe more or less rounded apically.
30(33) Male: Eighth ventrite with a shallower emargination; aedeagal median lobe narrower;
endophallic expulsion hook with anterior plate about as long as or a little longer than posterior plate; copulatory tube with main tube longer.
31(32) Male: Aedeagal median lobe narrower at apicolateral corners (Fig. 62B); endophallic
expulsion hook with anterior plate turning anterolaterally, simply pointed at apex, about
as long as posterior plate (Fig. 62H) ...........................................................S. takane Naomi
32(31) Male: Aedeagal median lobe broader at apicolateral corners (Fig. 63B); endophallic
expulsion hook with anterior plate turning anteriorly, hooked apicomesially, a little longer
than posterior plate (Fig. 63H) ............................................S. unicoloratus Naomi & Puthz
33(30) Male: Eighth ventrite with a deeper emargination (Fig. 64F); aedeagal median lobe
broader (Fig. 64B); endophallic median hook with anterior plate shorter than posterior
plate (Fig. 64G); copulatory tube with main tube shorter (Fig. 64B) ...................................
.............................................................................................. S. tohokuensis Naomi & Puthz
34(13) Male: Aedeagal median lobe of broad form, usually uniformly broad from the base to apicolateral corners.
35(42) Male: Aedeagal median lobe with apicolateral corners more or less angulate.
36(37) Male: Aedeagal median lobe tricuspidate at apex, with apical sclerotized area subtrapezoidal (Fig. 76A); endophallic lateral bands each narrower at base (Fig. 76A) ...................
............................................................................................................S. sawadai Hromádka
37(36) Male: Aedeagal median lobe simply pointed or obtusely angulate at apex, with apicalThe Steninae of Japan Part 2145

sclerotized area almost broad-triangular; endophallic lateral bands each broader at base.
38(41) Male: Aedeagal median lobe with apical sclerotized area longer, simply pointed apically;
endophallic expulsion hook almost cucumber-shaped. Female: Spermathecal duct withmore than 7 turns.
39(40) Male: Aedeagal median lobe broadest at about basal 2/5 (Fig. 77B). Female: Spermathecal duct not extending anteriorly beyond the anterior margin of capsule (Fig. 77F)............
................................................................................................ S. kishimotoi Naomi & Puthz
40(39) Male: Aedeagal median lobe broadest at apicolateral corners (Fig. 78B). Female: Spermathecal duct extending anteriorly beyond the anterior margin of capsule (Fig. 78F) .............
................................................................................................................ S. yokozekii Naomi
41(38) Male: Aedeagal median lobe with apical sclerotized area shorter, obtusely angulate apically (Fig. 79B); endophallic expulsion hook nearly boot-shaped (Fig. 79H). Female:
Spermathecal duct with 2 turns (Fig. 79F)................................................... S. tateoi Naomi
42(35) Male: Aedeagal median lobe with apicolateral corners rounded.
43(46) Male: Endophallic median bands longer, narrower; copulatory tube shorter, thicker.
44(45) Male: Endophallic expulsion hook with anterior plate partially fused with posterior plate(Fig. 80D); copulatory tube with apical tube weakly curved (Fig. 80E). Female: Spermathecal duct much shorter, thicker, with 1 or 2 turns (Fig. 80F).................. S. ohishii Naomi
45(44) Male: Endophallic expulsion hook with anterior plate demarcated by suture from posterior plate (Fig. 81G); copulatory tube with apical tube almost straight (Fig. 81H). Female:
Spermathecal duct much longer, thinner, with more than 6 turns (Fig. 81E) .......................
.................................................................................................................S. fusciceps Naomi
46(43) Male: Endophallic median bands shorter, broader; copulatory tube longer, thinner.
47(48) Male: Aedeagal median lobe with apical sclerotized area broader (Fig. 82B); endophallic
copulatory tube almost elongate-S-shaped, with lateral ﬂap (Fig. 82B). Female: Spermatheca with capsule smaller; duct coiled without any abrupt bends on its way (Fig. 82E) ....
................................................................................................................... S. indubius Sharp
48(47) Male: Aedeagal median lobe with apical sclerotized area narrower (Fig. 83B); endophallic copulatory tube weakly bisinuous, without lateral ﬂap (Fig. 83B). Female: Spermatheca with capsule larger; duct coiled, partially with abrupt bends on its way (Fig. 83E) ...
.........................................................................................S. kiyosumiensis Naomi & Takeda
Stenus serratus Naomi(Figs. 59A–H, 106E)
Stenus serratus Naomi, 2006: 103; Naomi & Puthz, 2013: 141.
Type material examined. Holotype: ♂ (CBM), Mikuni Pass, Yuzawa-machi, Niigata Pref.,28. v. 1995, K. Haga leg. Paratypes: 2 ♀ (cN), Mukoyama, Yuzawa-machi, Niigata Pref., 3. vi.
1995, K. Haga leg.; 1 ♂ (cN), Otari, Nagano Pref., 5. vi. 1994, T. Ito leg.
Other material examined. [HONSHU]: 1 ♂, Doai Valley, Marumori-machi, Miyagi Pref., 30.
xi. 1995, S. Nomura leg.; 1 ♂, Setogaro Valley, Iwaki City, Fukushima Pref., 19. vii. 1995, S.
Nomura leg.; 2 ♂1 ♀, Hanazono Valley, Kita-ibaraki City, Ibaraki Pref., 1. xii. 1995, S. Nomura
leg.; 1 ♂, Machigasawa, Mt. Tanigawa, Gunma Pref., 27. vii. 1996, S. Nomura leg.
Distribution. Japan: Honshu (Tohoku, Chubu and Kanto districts.)
Redescription. Male and female: Body 4.9–5.8 mm (fore-body 2.1–2.3 mm) in length, with

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Fig. 59. Stenus serratus Naomi (Yuzawa, Niigata). A, 9th ventrite of male; B, aedeagus; C, posterior part of 8th
ventrite of male; D, E, posterior part of gonocoxite; F, G, spermatheca; H, apex of median lobe with the outthrusted endophallic components. Scale 1: 0.2 mm for A, B, 0.1 mm for D–H; Scale 2: 0.25 mm for C.

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antennae moderately long, very thin. Head, pronotum and abdomen dark chocolate brown to
black; elytra reddish brown to dark reddish brown; labrum dark red; antennae and legs yellowish
brown to reddish brown. Head weakly concave, with a pair of broad longitudinal furrows; punctures round to almost round, dense to very dense, somewhat umbilicate near inner margins ofeyes, while punctures round, dense, regular on the median part. Pronotum with surface almost
smooth to weakly uneven; punctures round, very dense, moderately large, regular. Elytra withsurface almost even to weakly uneven; punctures very dense, large. Tarsi each with 4th tarsomere
strongly bilobed. Abdomen with punctures round, dense to moderately dense, small in anterior
segments, while punctures in posterior segments sparse to moderately dense, very small, regular.
Lateroventrites missing; tergoventrite sutures existing, very thin.
Male: Seventh ventrite posteriorly with a small, semicircular ﬂat area, which is very shallowly emarginate; 8th ventrite (Fig. 59C) posteriorly with a broad, arcuate emargination; 9th tergum with antecostal apophyses moderately long; 9th ventrite (Fig. 59A) broad, irregularly serrate
posteriorly, with macrosetae moderately long, apicolateral teeth long, pointed, apicolateral setae
moderately long; 10th tergum rounded posteriorly. Aedeagal median lobe (Fig. 59B) elongate,
relatively narrow in apical half, gently rounded apicolaterally, pointed at apex; apical sclerotizedarea (Fig. 59B) subtriangular. Endophallic median bands (Fig. 59H) long, relatively narrow;
expulsion hooks (Fig. 59H) each elongate, with posterior plate weakly projecting posterolaterally; copulatory tube (Fig. 59H) very long, attenuate, with a weak constriction near apex. Parameres (Fig. 59H) each having stem weakly constricted near the middle, acicular at apex; apicalarea long, moderately swollen mesially, furnished mesially with 12 to 13 short setae.
Female: Eighth ventrite rounded posteriorly; gonocoxites (Fig. 59D, E) irregularly toothed
posteriorly, each with apicolateral tooth very long, acutely pointed, apicolateral setae moderately
long. Spermatheca (Fig. 59F, G) with capsule spherical, large, a little broader than apical chamber; apical chamber pyriform to fusiform, large; duct irregularly bent, moderately coiled, mostly
located behind the middle of apical chamber.
Biology and ecology. S. serratus is distributed in the mountainous regions of central Honshu.
The beetles inhabit leaf litter in the natural forests.
Remarks. S. serratus is allied to S. sadoensis, but it is separable from the latter species by theendophallic expulsion hooks uniformly sclerotized (Fig. 59H), and the spermatheca with its capsule larger and spherical and its apical chamber much smaller (Fig. 59F).
Stenus sadoensis Naomi(Figs. 60A–H, 106F)
Stenus sadoensis Naomi, 2006: 105; Naomi & Puthz, 2013: 141.
Type material examined. Holotype: ♂ (CBM), Mt. Ootaki, Sado Is., Niigata Pref., 5. viii.
1998, S. Naomi leg. Paratype: ♀ (cN), same data as holotype.
Other material examined. [HONSHU]: 1 ♂, Aikawa-machi, Sado Is., Niigata Pref., 9. vi.
2004, H. Yokozeki leg.
Distribution. Japan: Honshu (Sado Is.).
Redescription. Male and female: Body 4.3–5.6 mm (fore body 2.4–2.6 mm) in length, withantennae long, very thin. Head, pronotum and abdomen dark chocolate brown to black; elytra
dark red; labrum dark red; antennae and legs yellowish brown to reddish brown. Head weakly
concave, with a pair of broad longitudinal furrows; punctures round, dense to very dense, umbili-

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Fig. 60. Stenus sadoensis Naomi (Sado, Niigata). A, 9th ventrite of male; B, aedeagus; C, posterior part of 8th
ventrite of male; D, posterior part of 8th ventrite of female; E, F, posterior part of gonocoxite; G, spermatheca;
H, expulsion hooks. Scale 1: 0.2 mm for A, B, 0.1 mm for E–H; Scale 2: 0.25 mm for C, D.

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cate. Pronotum with surface almost even; punctures round, very dense, moderately large, almost
regular. Elytra with surface uneven, weakly depressed near sutures; punctures round to almost
round, very dense, large, coarse. Tarsi each with 4th tarsomere strongly bilobed. Abdomen with
punctures round to almost round, moderately dense to dense, various in size in anterior segments,
while punctures in posterior segments sparse, very small. Lateroventrites missing; tergoventrite
sutures existing, very thin.
Male: Seventh ventrite posteromedially with an elongate-elliptical ﬂat area; 8th ventrite (Fig.
60C) posteromedially with a semicircular emargination; 9th tergum with antecostal apophyses
moderately long; 9th ventrite (Fig. 60A) broad, regularly serrate posteriorly, with macrosetae
moderately long, apicolateral teeth pointed, apicolateral setae moderately long; 10th tergum very
shallowly emarginate posteromedially. Aedeagal median lobe (Fig. 60B) elongate, relatively narrow in apical half, obtusely angulate apicolaterally, pointed at apex; apical sclerotized area (Fig.
60B) almost triangular. Endophallic dorsal membrane subovoidal (Fig. 60B); median bands (Fig.
59B) long, rather thin; expulsion hooks (Fig. 60H) separated, each with anterior plate menbranous, rounded anteriorly, posterior plate weakly projecting and pointed posterolaterally; copulatory tube (Fig. 60B) with basal chamber comprising two thin rods, main tube long, attenuate,
thin, straight. Parameres (Fig. 60B) almost straight; apical area moderately long, swollen mesially at base, acicular at apex, furnished mesially with 12 to 17 short setae.
Female: Eighth ventrite (Fig. 60D) rounded posteriorly; gonocoxites (Fig. 60E, F) distinctly
toothed posteriorly, each with apicolateral tooth long, stout, acutely pointed, apicolateral setae
short. Spermatheca (Fig. 60G) with capsule ovoidal, moderately large; apical chamber pyriform,
very large, shallowly concave on apical surface; duct long, relatively thin, almost tightly coiled.
Biology and ecology. S. sadoensis is distributed only in the mountainous regions of Sado Is.,
Central Honshu. The beetles inhabit leaf litter in the natural forests.
Remarks. S. sadoensis is closely allied to S. serratus, but it is separable from the latter species by the endophallic expulsion hook with its anterior plate membranous (Fig. 60H), and thespermatheca with its capsule smaller and ovoidal, and its apical chamber much larger (Fig. 60G).
Stenus subserratus Naomi(Figs. 61A–H, 106G)
Stenus subserratus Naomi, 2006: 107; Naomi & Puthz, 2013: 141.
Type material examined. Holotype: ♂ (CBM), Mt. Shibitsu, Katashina Vil., Gunma Pref., 8.
ix. 1996, Y. Hagino et al. leg. Paratypes: 2 ♂ (cN), same data as holotype; 2 ♀ (cN), Mt. Keizuru,
Katashina Vil., Gunma Pref., 13. vii. 1996, K. Ishii et al. leg.
Distribution. Japan: Honshu (Gunma Pref.).
Redescription. Male and female: Body 4.3–4.8 mm (fore body 2.0–2.2 mm) in length, withantennae relatively short, thin. Head black; pronotum, elytra and abdomen reddish chocolate
brown to dark brown; labrum dark red; antennae and legs yellowish brown to reddish brown.
Head weakly concave, with a pair of broad longitudinal furrows; surface with punctures round,very dense, small near inner margins of eyes while punctures on the middle round, moderately
dense, small. Pronotum with surface weakly uneven; punctures round to almost round, very
dense, moderately large, sometimes two or more punctures partially fused. Elytra with surface
uneven, weakly depressed near suture; punctures round, very dense, various in size, coarse. Tarsi
each with 4th tarsomere strongly bilobed. Abdomen with punctures round, sparse to moderately

150

Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

Fig. 61. Stenus subserratus Naomi (A–C, F, H, Shibitsu, Gunma; D, E, G, Keizuru, Gunma). A, 9th ventrite ofmale; B, aedeagus; C, posterior part of 8th ventrite of male; D, E, posterior part of gonocoxite; F, G, spermatheca; H, apex of median lobe, with the outthrusted endophallic components. Scale 1: 0.2 mm for A, B,
0.1 mm for D–H; Scale 2: 0.25 mm for C.

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151

dense, small in anterior segments, while punctures in posterior segments sparse to moderately
dense, very small to small. Lateroventrites missing; tergoventrite sutures existing, very thin.
Male: Seventh ventrite posteromedially with a shallow, bell-shaped depression, which is very
shallowly emarginate; 8th ventrite (Fig. 61C) posteromedially with a semicircular emargination;
9th tergum with antecostal apophyses moderately long; 9th ventrite (Fig. 61A) minutely serrate
posteriorly, arcuate and narrow between apicolateral teeth, with macrosetae long, apicolateral
teeth short, stout, pointed, apicolateral setae short; 10th tergum very shallowly emarginate.
Aedeagal median lobe (Fig. 61B) elongate, acutely pointed at apex; apical sclerotized area (Fig.
61B) subtriangular. Endophallic dorsal membrane (Fig. 61H) elliptical, large; median bands (Fig.
61H) very long, thin; expulsion hooks (Fig. 61H) separated, each with anterior plate fused withposterior plate, the posterior plate projecting and pointed posterolaterally; copulatory tube (Fig.
61H) very long, with basal chamber elongate-ovoidal, main tube very long, slender, attenuate.
Parameres (Fig. 61B) rather thick, each weakly broadened in apical 1/3, pointed apically, mesially with 2 or 3 short setae before the apical area; apical area very short, furnished with 8 shortsetae along mesial margin.
Female: Eighth ventrite obtuse posteromedially; gonocoxites (Fig. 61D, E) each with apicolateral tooth pointed, apicolateral setae moderately long. Spermatheca (Fig. 61F, G) with capsulespherical to ovoidal, large to very large; apical chamber pyriform, about as large as or a little
smaller than capsule; duct long, moderately or very tightly coiled.
Biology and ecology. S. subserratus seems to be a rare species; and at present it is distributed
only in the highland Oze moor, central Honshu. The beetles inhabit leaf litter in the natural forests near the moor.
Remarks. S. subserratus is allied to S. serratus and S. sadoensis, but it is separable from thelatter two species by the male 9th ventrite with its apicolateral tooth broader and shorter (Fig.
61A), and the aedeagal paramere shorter, with its apical area much shorter (Fig. 61B).
Stenus takane Naomi(Figs. 62A–H, 106H)
Stenus takane Naomi, 1987: 8; Herman, 2001: 2412; Naomi & Puthz, 2013: 142.
Type material. Holotype: ♂ (KUF), Mayogatai, Aomori Pref., 26–28. vi. 1980, S. Naomi leg.
Type material examined. Paratypes: 1 ♂1 ♀ (cN), Mayogatai, Aomori Pref., 26–28. vi. 1980,
S. Naomi leg.
Other material examined. [HONSHU]: 2 ♂1 ♀, Towada, Aomori Pref., 4. viii. 1987, S.
Nomura leg.
Distribution. Japan: Honshu (Aomori Pref.).
Redescription. Male and female: Body 4.4–5.0 mm (fore body 2.2–2.3 mm) in length, withantennae moderately long, very thin. Head black; pronotum, elytra and abdomen dark chocolate
brown; labrum dark red to black; antennae and legs yellowish brown to reddish brown. Headhardly or only weakly concave, with a pair of distinct longitudinal furrows; punctures round toalmost round, very dense, small, somewhat umbilicate. Pronotum with surface uneven; puncturesround to almost round, very dense, moderately large, coarse, sometimes two or more punctures
partially fused. Elytra with surface weakly uneven, almost ﬂat near suture; punctures round, very
dense, various in size, somewhat coarse. Tarsi each with 4th tarsomere strongly bilobed. Abdomen with punctures round, moderately dense, small in anterior segments, while punctures in pos-

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Fig. 62. Stenus takane Naomi (A–C, F, H; Mayogatai, Aomori; D, E, G, Towada, Aomori). A, 9th ventrite ofmale; B, aedeagus; C, posterior part of 8th ventrite of male; D, E, posterior part of gonocoxite; F, G, spermatheca; H, expulsion hooks. Scale 1: 0.2 mm for A, B, 0.1 mm for D–H; Scale 2: 0.25 mm for C.

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terior segments sparse, very small, regular. Lateroventrites missing; tergoventrite sutures existing, very thin.
Male: Seventh ventrite posteromedially with a bell-shaped ﬂat area, which is very shallowly
emarginate; 8th ventrite (Fig. 62C) posteromedially with an arcuate, broad emargination; 9th tergum with antecostal apophyses moderately long; 9th ventrite (Fig. 62A) minutely serrate posteriorly, with macrosetae moderately long, apicolateral teeth stout, pointed, apicolateral setae moderately long; 10th tergum obtusely angulate. Aedeagal median lobe (Fig. 62B) elongate, roundedapicolaterally, almost round at apex; apical sclerotized area (Fig. 62B) almost fusiform, rounded
anteriorly. Endophallic dorsal membrane (Fig. 62B) almost round; median bands (Fig. 62B)
moderately long, very thin; expulsion hooks (Fig. 62H) separated, diverging anteriorly in theanterior 1/2, each with anterior plate a little broader than posterior plate, posterior plate truncate
posteriorly; copulatory tube (Fig. 62B) very slender with basal chamber elongate-ovoidal, maintube long, very thin, attenuate. Parameres (Fig. 62B) each weakly narrowed on its way, acutely
pointed at apex; apical area very long, moderately swollen mesially at base, furnished mesiallywith 5 to 7 setae of various length.
Female: Eighth ventrite rounded posteriorly; gonocoxites (Fig. 62D, E) toothed posteriorly,
each with apicolateral tooth long, acutely pointed, apicolateral setae long. Spermatheca (Fig. 62F,
G) with capsule spherical, large to very large; apical chamber pyriform or elongate-pyriform,
large; duct very long, thin to moderately broad, almost tightly, irregularly coiled.
Biology and ecology. S. takane is distributed in the mountainous regions of northern Tohoku
district, Honshu. The beetles inhabit leaf litter in the natural forests.
Remarks. S. takane is allied to S. unicoloratus and S. tohokuensis, but it is separable from thelatter two species by the aedeagal median lobe narrower in apical half (Fig. 62B) and the endophallic expulsion hook with its anterior plate a little broader than posterior plate (Fig. 62H).
Etymology. The speciﬁc epithet of this species is derived from the Japanese noun “Takane”,
which means “high mountains”.
Stenus unicoloratus Naomi & Puthz(Figs. 63A–H, 106I)
Stenus unicoloratus Naomi, 2006: 114; Naomi & Puthz, 2013: 142.
Type material examined. Holotype: ♂ (CBM), Iidate-mura, Fukushima Pref., 21. vii. 1985, S.
Nomura leg. Paratypes: 3 ♀ (cN), Dakedai, Fujisato-machi, Akita Pref., 27–28. viii. 1994, Ishii &Yorii leg.; 1 ♀ (CBM), Odake, Fujisato–machi, Akita Pref., 28. viii. 1994, O. Nakamura & Y.
Hagino leg; 4 ♂2 ♀ (cN), same data as above; 1 ♀ (cN), Tanashiro-kami, Fujisato–machi, Akita
Pref., 27. viii. 1994, O. Nakamura & Y. Hagino leg.; 1 ♀ (cN), same data as holotype. [Note: One
female paratype of S. unicoloratus (1 ♀, Tanashiro-kami, Fujisato–machi, Akita Pref., 27. viii.
1994, Naka leg.) does not belong to this species. Since it is an un-identiﬁed species of the asyura-group, it is here excluded from the paratype of this species.]
Other material examined. [HONSHU]: 1 ♂1 ♀, Mt. Higashi-ozana, Fukushima City, Fukushima Pref., 10. vi. 2014, H. Yokozeki leg.; 1 ♂, Mt. Nagare-ishi, Shimogo-machi, Fukushima
Pref., 30. vi. 2008, K. Haga leg.; 1 ♂1 ♀, Urushino-sawa, Kuriyama Vil., Tochigi Pref., 12. x.
1997, S. Nomura leg.
Distribution. Japan: Honshu (Akita, Fukushima and Tochigi Prefs.).
Redescription. Male and female: Body 3.7–5.0 mm (fore body 2.0–2.3 mm) in length, with

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Fig. 63. Stenus unicoloratus Naomi & Puthz (A–E, G, H, Iidate, Fukushima; F, Fujisato, Akita). A, 9th ventriteof male; B, aedeagus; C, posterior part of 8th ventrite of male; D, E, posterior part of gonocoxite; F, G, spermatheca; H, expulsion hooks. Scale 1: 0.2 mm for A, B, 0.1 mm for D–H; Scale 2: 0.25 mm for C.

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antennae moderately long, thin. Body black; pronotum, elytra and abdomen dark chocolate
brown; labrum dark red; antennae and legs yellowish brown to reddish brown. Head weakly concave, with a pair of broad longitudinal furrows; punctures round to almost round, very dense,
small. Pronotum with surface almost even; punctures round, very dense, moderately large, somewhat coarse, sometimes two punctures partially fused. Elytra with surface uneven, ﬂat or weakly
depressed near suture; punctures round to elliptical, very dense, various in size, coarse. Tarsi
each with 4th tarsomere strongly bilobed. Abdomen with punctures round, moderately dense,
various in size, regular, while punctures in posterior segments very small, sparse to moderately
dense, very small. Lateroventrites missing; tergoventrite sutures existing, very thin.
Male: Seventh ventrite posteromedially with a bell-shaped ﬂat area, which is very shallowly
emarginate; 8th ventrite (Fig. 63C) posteromedially with an arcuate, shallow emargination; 9th
tergum with antecostal apophyses moderately long; 9th ventrite (Fig. 63A) incompletely dentate
posteriorly, with macrosetae short, apicolateral teeth acutely pointed, apicolateral setae short tomoderately long; 10th tergum obtusely angulate posteriorly. Aedeagal median lobe (Fig. 63B)
elongate, rounded apicolaterally, round at apex; apical sclerotized area (Fig. 63B) semicircular,
almost straight anteriorly. Endophallic dorsal membrane (Fig. 63B) subovoidal, small; medianbands (Fig. 63B) long, very thin; expulsion hooks (Fig. 63H) separated, each elongate, with theanterior plate weakly incurved or hooked at apex, partially demarcated by a suture from, and alittle narrower than posterior plate, the posterior plate pointed posterolaterally; copulatory tube
(Fig. 63B) very slender, with basal chamber elongate-ovoidal, main tube very thin, long, attenuate. Parameres (Fig. 63B) thick, each very acutely pointed; apical area long, weakly swollen atbase, furnished mesially with 9 to 11 short setae.
Female: Eighth ventrite rounded posteriorly; gonocoxites (Fig. 63D, E) distinctly toothed
posteriorly, each with apicolateral tooth long, pointed, apicolateral setae moderately long. Spermatheca (Fig. 63F, G) with capsule spherical to ovoidal, large; apical chamber almost pyriform
or fusiform, large to very large; duct moderately long, thin to moderately thick, almost tightly
coiled.
Biology and ecology. S. unicoloratus is distributed in the mountainous regions of Tohoku
district, Honshu. The beetles usually inhabit leaf litter in the natural forests, but one male beetle
was collected by sweeping the shrubs at the summit of Mt. Nagare-ishi, Fukushima.
Remarks. S. unicoloratus is allied to S. takane and S. tohokuensis, but it is separable from thelatter two species by the aedeagal median lobe with its apical sclerotized area almost straightanteriorly (Fig. 63B) and the endophallic expulsion hook with its posterior plate projecting andpointed posterolaterally (Fig. 63H).
Stenus tohokuensis Naomi & Puthz(Figs. 64A–H, 106J)
Stenus tohokuensis Naomi & Puthz, 2006: 116; Naomi & Puthz, 2013: 142.
Type material examined. Holotype: ♂ (CBM), Jyuniko, Iwasaki Vil., Aomori Pref., 6–7. x.
1992, T. Kishimoto leg. Paratype: 1 ♀ (cN), same locality, 9. viii. 1987, S. Nomura leg.
Distribution. Japan: Honshu (Aomori Pref.).
Redescription. Male and female: Body 5.1–5.3 mm (fore body 2.0–2.3 mm) in length, withantennae moderately long, very thin. Head black; pronotum, elytra and abdomen dark chocolate
brown; labrum dark red; antennae and legs yellowish brown to reddish brown. Head hardly or

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Fig. 64. Stenus tohokuensis Naomi & Puthz (Jyuniko, Aomori). A, 9th ventrite of male; B, aedeagus; C, spermatheca; D, E, posterior part of gonocoxite; F, posterior part of 8th ventrite of male; G, expulsion hooks; H, posterior part of 8th ventrite of female. Scale 1: 0.2 mm for A, B, 0.1 mm for C–E, G; Scale 2: 0.25 mm for F, H.

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only weakly concave, with a pair of longitudinal furrows; punctures round to almost round, very
dense, various in size. Pronotum with surface almost even; punctures round, very dense, various
in size, somewhat coarse, two punctures sometimes partially fused. Elytra with surface weakly
uneven, almost ﬂat near suture; punctures round, very dense, small near suture, large at lateralparts. Tarsi each with 4th tarsomere strongly bilobed. Abdomen with punctures round, moderately dense, small in anterior segments, while punctures in posterior segments sparse, very small.
Lateroventrites missing; tergoventrite sutures existing, very thin.
Male: Seventh ventrite posteromedially with a bell-shaped ﬂat area; 8th ventrite (Fig. 64F)
posteromedially with a moderately deep emargination; 9th tergum with antecostal apophyses
short; 9th ventrite (Fig. 64A) broad, irregularly serrate posteriorly, with macrosetae moderately
long, apicolateral teeth pointed, apicolateral setae moderately long; 10th tergum almost rounded
posteriorly. Aedeagal median lobe (Fig. 64B) moderately broad, rounded apicolaterally, round at
apex; apical sclerotized area (Fig. 64B) almost semicircular, bidentate at anterior margin. Endophallic dorsal membrane (Fig. 64B) subovoidal, small; median bands (Fig. 64B) moderately
long, very thin; expulsion hooks (Fig. 64G) slightly asymmetrical, each with the anterior platepartially demarcated by a ridge from, and also much smaller than posterior plate, the posterior
plate angulate mesially before the middle; copulatory tube (Fig. 64B) with basal chamber long,thin, elongate-ovoidal at base, main tube short, thin, attenuate. Parameres (Fig. 64B) thick, eachacutely pointed at apex; apical area very long, weakly swollen laterally, furnished mesially, irregularly with 15 to 17 short setae.
Female: Eighth ventrite (Fig. 64H) rounded posteriorly; gonocoxites (Fig. 64D, E) toothed
posteriorly, each with apicolateral tooth very long, acutely pointed. Spermatheca (Fig. 64C) with
capsule spherical, large; apical chamber elongate-pyriform, large; duct moderately long, moderately thick to thick, tightly coiled.
Biology and ecology. S. tohokuensis is distributed in the mountainous regions of northern
Tohoku district, Honshu. The beetles inhabit leaf litter in the natural forests.
Remarks. S. tohokuensis is allied to S. takane and S. unicoloratus, but it is separable from thelatter two species by the aedeagal median lobe broader (Fig. 64B), the endophallic expulsion
hook with its posterior plate angulate mesially before the middle (Fig. 64G), and the copulatory
tube with its main tube shorter (Fig. 64B).
Stenus campaniformis Naomi, Nomura & Puthz sp. nov.
(Figs. 65A–E, 106K)
Type series. Holotype: ♂ (NSMT-I-C-200328 in NMNST), Oguni-cho, Yamagata Pref., 5. vi.
2010, I. Matoba leg.
Distribution. Japan: Honshu (Yamagata Pref.).
Description. Male: Body 5.1 mm (fore body: 2.2 mm) in length, moderately shining, withantennae moderately long. Body black but weakly, reddishly tinged; labrum black; antennae andlegs reddish brown. Head weakly concave, with a pair of distinct, broad longitudinal furrows;
punctures round, dense to very dense, various in size, umbilicate. Pronotum with surface slightly
uneven; punctures round, very dense, various in size, somewhat irregular. Elytra with surface
weakly uneven; punctures round, very dense, medium-sized to large, somewhat coarse. Tarsi
each with 4th tarsomere strongly bilobed. Abdomen with punctures round, sparse to moderately
dense, small, somewhat irregular in anterior segments, while punctures in posterior segments
sparse to moderately dense, very small, almost regular. Lateroventrites missing; tergoventrite

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Fig. 65. Stenus campaniformis Naomi, Nomura & Puthz sp. nov. (Oguni, Yamagata). A, 9th ventrite of male; B,
9th and 10th terga of male; C, aedeagus; D, expulsion hooks; E, 7th and 8th ventrites of male. Scale 1: 0.1 mm
for A, C; Scale 2: 0.2 mm for B, 0.05 mm for D; Scale 3: 0.3 mm for E.

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sutures existing but almost obsolete.
Seventh ventrite (Fig. 65E) posteromedially with a bell-shaped ﬂat area, which is very shallowly emarginate; 8th ventrite (Fig. 65E) posteriorly with a medium-sized emargination; 9th tergum (Fig. 65B) with antecostal apophyses long; 9th ventrite (Fig. 65A) distinctly serrate posteriorly, with macrosetae very long, apicolateral teeth stout, pointed, apicolateral setae moderately
long; 10th tergum (Fig. 65B) apicomedially with a long projection. Aedeagal median lobe (Fig.
65C) elongate, rounded apicolaterally, round at apex; apical sclerotized area (Fig. 65C) almost
semicircular, bidentate at anterior margin. Endophallic dorsal membrane (Fig. 65C) moderately
large, almost round; median bands (Fig. 65C) long; expulsion hooks (Fig. 65D) almost connected
at the posteromesial corners, anterior plate fused with posterior plate; copulatory tube (Fig. 65C)
very long, with basal chamber long, hardly swollen laterally, main tube long, slender but weakly
curved at apical part. Parameres (Fig. 65C) very thick, each very acutely pointed at apex; apicalarea long, weakly swollen mesially, furnished mesially with 2 short setae along ventral margin,
and with 4 to 5 short setae along dorsal margin.
Female: Unknown.
Biology and ecology. S. campaniformis is distributed in the mountainous regions of central
Tohoku district, Honshu. The beetles inhabit leaf litter in the natural forests.
Remarks. When considering their common possession of such characters as the bell-shaped
apical part of aedeagal median lobe, the very acutely pointed apex of aedeagal parameres, etc., S.
campaniformis is probably allied to S. takane, S. unicoloratus and S. tohokuensis, but it is separable from the latter three species by the 10th tergum with an apicomedian projection (Fig. 65B),
the aedeagal paramere distinctly thicker (Fig. 65C), and the endophallic expulsion hook with its
anterior plate fused with posterior plate (Fig. 65D). However, S. campaniformis is certainly similar also to S. naomi, and S. tuberascens in that these 3 species share a very characteristic, cuspidate condition of 10th tergum, but it is separable from the latter two species by the aedeagal
median lobe uniformly rounded apically (Fig. 65C), the paramere much thicker (Fig. 65C), andthe endophallic copulatory tube shorter (Fig. 65C).
Etymology. The speciﬁc epithet of this new species is derived from the Latin adjective “campaniformis”, which means “bell-shaped”; and the apical part of aedeagal median lobe is bellshaped.
Stenus naomii Puthz(Figs. 66A–J, 106 L)
Stenus indubius Sharp, 1889: Hromádka, 1979: 103.
Stenus naomii Puthz, 2001: 38; Naomi & Puthz, 2013: 142.
Type material examined. Holotype: ♀ (NHML), Kobe, Japan, 25. vii. 1927, Ueno. Paratypes:
1 ♂1 ♀ (cN), Mt. Mimuro, Hyogo Pref., 15. ix. 1992, T. Ito leg.; 1 ♂ (cN), Mt. Mayasan, Kobe
City, Hyogo Pref., 12. v. 1980; 1 ♂, Mt. Sanjyo, Nakawa Vil., Okayama Pref., 11. vii. 1993, K.
Watanabe leg.; 1 ♂ (cN), Misasa Spa. Tottori Pref., 28. ix. 1986, T. Ito leg.
Other material examined. [HONSHU]: 2 ♂3 ♀, Mt. Mimuro, Hyogo Pref., 15. ix. 1992, T. Itoleg.; 1 ♀, Mt. Mimuro, Hyogo Pref., 7. vi. 1997, H. Hoshina leg.; 1 ♀, Wakasugi, Okayama Pref.,22. x. 2009, T. Ito leg.
Distribution. Japan: Honshu (Chugoku district).
Redescription. Male and female: Body 4.7–5.3 mm (fore body 2.0–2.3 mm) in length, with

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Fig. 66. Stenus naomii Puthz (A, C–I, Mimuro, Hyogo; B, J, Mayasan, Hyogo). A, 9th ventrite of male; B,
aedeagus; C, posterior part of 8th ventrite of male; D, 10th tergum of female; E, 10th tergum of male; F, G,
posterior part of gonocoxite; H, I, spermatheca; J, expulsion hooks. Scale 1: 0.2 mm for A, B, 0.1 mm for F to
J; Scale 2: 0.25 mm for C–E.

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antennae moderately long, very thin. Head black; pronotum, elytra and abdomen dark chocolate
brown; labrum dark red; antennae and legs yellowish brown to reddish brown. Head weakly concave, with a pair of broad longitudinal furrows; punctures round, dense to very dense, small. Pronotum with surface weakly uneven; punctures round to almost round, very dense, moderately
large, somewhat coarse, two or more punctures sometimes partially fused. Elytra with surface
almost even, ﬂat near suture; punctures round, very dense, large, sometimes coarse. Tarsi eachwith 4th tarsomere strongly bilobed. Abdomen with 10th tergum (Fig. 66D, E) apicomediallywith an acute, small projection, which turns posteroventrally; punctures round, sparse to moderately dense, small in anterior segments, while punctures in posterior segments sparse, very small,regular. Lateroventrites missing; tergoventrite sutures almost obsolete.
Male: Seventh ventrite posteromedially with a bell-shaped ﬂat area, which is very shallowly
emarginate; 8th ventrite (Fig. 66C) posteromedially with an arcuate emargination; 9th tergum
with antecostal apophyses long; 9th ventrite (Fig. 66A) broad, serrate posteriorly, with macrosetae moderately long, apicolateral teeth thin, acutely pointed, apicolateral setae very long. Aedeagal median lobe elongate, rounded apicolaterally, pointed with a small median cusp at apex; apical sclerotized area (Fig. 66B) almost bell-shaped, bidentate at anterior margin, with a
median-longitudinal transparent area. Endophallic dorsal membrane (Fig. 66B) subovoidal;
median bands (Fig. 66B) very long, thin; expulsion hooks (Fig. 66J) separated, each elongate,
lateromedially with a small notch, anterior plate almost fused with posterior plate; copulatory
tube (Fig. 66B) very long, with basal chamber small, main tube slender but moderately swollen
at base, weakly swollen near the middle, and weakly sinuous at apex. Parameres (Fig. 66B)
short, each relatively thick, very acutely pointed; apical area long, moderately swollen mesiallyat base, furnished mesially with 3 to 4 short setae along ventral margin, and with 6 moderately
long setae along dorsal margin.
Female: Eighth ventrite rounded posteriorly; gonocoxites (Fig. 66F, G) toothed posteriorly,
each with apicolateral tooth long, acutely pointed, apicolateral setae moderately long. Spermatheca (Fig. 66H, I) with capsule spherical, moderately large to large; apical chamber pyriform,
very large; duct moderately long and thick, almost tightly coiled.
Biology and ecology. S. naomi is distributed in the plains and low mountainous regions ofeastern Chugoku district, Honshu. The beetles inhabit leaf litter in the natural forests.
Remarks. S. naomii is closely allied to S. tuberascens, but it is separable from the latter species by the aedeagal median lobe distinctly narrower at apex (Fig. 66B), the aedeagal apicalsclerotized area with a median-longitudinal subtransparent area and also with a small apicomedian cusp (Fig. 66B), and the endophallic expulsion hook only weakly broadened posteriorly at
the posterior part (Fig. 66J).
Etymology. The speciﬁc epithet of this species is named after S.-I. Naomi, an author of thispaper.
Stenus tuberascens Naomi, Nomura & Puthz sp. nov.
(Figs. 67A–E, 107A)
Type series. Holotype: ♂ (NSMT-I-C-200329 in NMNST), Takahama, Fukui Pref., 19. v.
1991, M. Saito leg. Paratype: 1 ♂ (cN), Mefu, Maizuru City, Kyoto Pref., 2. iv. 2004, T. Murao
leg.
Distribution. Japan: Honshu (Kyoto and Fukui Prefs.).
Description. Male: Body 4.8 mm (fore body: 2.2 mm) in length, moderately shining, with

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Fig. 67. Stenus tuberascens Naomi, Nomura & Puthz sp. nov. (Takahama, Fukui). A, 9th and 10th terga of male;B, aedeagus; C, 9th ventrite of male; D, expulsion hooks; 8th ventrite of male. Scale 1: 0.2 mm for A, 0.05
mm for D; Scale 2: 0.1 mm for B, C; Scale 3: 0.3 mm for E.

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antennae moderately long, thin. Head black; pronotum, elytra and abdomen dark chocolate
brown; labrum dark red; antennae and legs yellowish brown to reddish brown. Head weakly concave, with a pair of broad longitudinal furrows; punctures round, moderately dense to dense, various in size, irregular. Pronotum with surface uneven; punctures round, very dense, moderately
large, somewhat irregular. Elytra with surface weakly uneven; punctures round, very dense, moderately large to large, coarse. Tarsi each with 4th tarsomere strongly bilobed. Abdomen with
punctures round to elliptical, moderately dense, small, somewhat irregular in anterior segments,
while punctures in posterior segments sparse to moderately dense, very small to small, regular.
Lateroventrites missing; tergoventrite sutures almost obsolete.
Eighth ventrite (Fig. 67E) posteromedially with a small, arcuate emargination; 9th tergum(Fig. 67A) with antecostal apophyses long; 9th ventrite (Fig. 67C) moderately broad, distinctly
serrate posteriorly, with macrosetae long, apicolateral teeth long, acutely pointed, apicolateral
setae very long; 10th tergum (Fig. 67A) apicomedially with an obtuse, moderately broad projection. Aedeagal median lobe (Fig. 67B) elongate, obtusely angulate or weakly rounded apicolaterally; apical sclerotized area (Fig. 67B) short, transverse, bidentate anteriorly, apicomedially witha relatively broad, rounded hump. Endophallic dorsal membrane (Fig. 67B) semicircular; medianbands (Fig. 67B) long, moderately broad; lateral bands (Fig. 67B) long, thick; expulsion hooks(Fig. 67D) connected at the posteromesial corners, each almost boot-shaped, with the anterior
plate thin, rounded apically, toothed at posterolateral corner, much smaller than and demarcatedby a suture from posterior plate, the posterior plate large, strongly broadened posteriorly, membranous at posteromesial area; copulatory tube (Fig. 67B) very slender, basal chamber elongateelliptical, main tube very long, attenuate. Parameres (Fig. 67B) rather thick, each acutely pointed
at apex; apical area very long, weakly swollen mesially, furnished mesially with 9–10 short setae.
Female: Unknown.
Biology and ecology. S. tuberascens is distributed in the plains of the northern part of Kansai
district and the northwestern part of Chubu district, central Honshu. The beetles inhabit leaf litterin the natural forests.
Remarks. S. tuberascens is closely allied to S. naomii, but it is separable from the latter species by the aedeagal median lobe broader and angulate at the apicolateral corner (Fig. 67B), theaedeagal apical sclerotized area shorter, and apicomedially with a relatively broad, roundedhump (Fig. 67B), and the endophallic expulsion hook with its posterior plate strongly broadened
posteriorly (Fig. 67D).
Etymology. The speciﬁc epithet of this new species is derived from the Latin adjective“tuberascens”, which means “tuberous” or “tuberculate; and the apical sclerotized area of aedeagal median lobe is weakly tuberculate ventromedially.
Stenus acerrimus Naomi(Figs. 68A–G, 107B)
Stenus acerrimus Naomi, 2006: 81; Naomi & Puthz, 2013: 141.
Type material examined. Holotype: ♂ (CBM), Mt. Hira, Shiga Pref., 16. viii. 1986, T. Ito leg.
Paratype: 1 ♀ (cN), same data as holotype.
Distribution. Japan: Honshu (Shiga Pref.)Redescription. Male and female: Body 4.3–5.0 mm (fore body 2.1–2.3 mm) in length, withantennae moderately long, thin. Head black; pronotum, elytra and abdomen dark chocolate164

Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

Fig. 68. Stenus acerrimus Naomi (Hira, Shiga). A, 9th ventrite of male; B, aedeagus; C, 9th and 10th terga offemale; D, posterior part of 8th ventrite of male; E, posterior part of 8th ventrite of female; F, posterior part ofgonocoxite; G, spermatheca; H, expulsion hooks. Scale 1: 0.2 mm for A to C, 0.1 mm for F–H; Scale 2:0.25 mm for D, E.

brown; labrum dark red; antennae and legs yellowish brown to reddish brown. Head weakly concave, with a pair of broad longitudinal furrows; punctures round, dense, small, almost regular.
Pronotum with surface weakly uneven; punctures round, very dense, various in size, somewhat
coarse. Elytra with surface weakly uneven, almost ﬂat near suture; punctures round to elliptical,

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165very dense, large, somewhat coarse. Tarsi each with 4th tarsomere strongly bilobed. Abdomenwith punctures round, sparse to moderately dense, small, somewhat irregular in anterior segments, while punctures in posterior segments moderately very dense, small, almost regular. Lateroventrites missing; tergoventrite sutures almost obsolete.
Male: Seventh ventrite posteromedially with a bell-shaped ﬂat area; 8th ventrite (Fig. 68D)
posteromedially with a large, subtriangular emargination; 9th tergum with antecostal apophyses
moderately long; 9th ventrite (Fig. 68A) serrate posteriorly, with macrosetae moderately long,apicolateral teeth very long, sharply pointed, apicolateral setae moderaetely long; 10th tergum
entire or very shallowly emarginate. Aedeagal median lobe (Fig. 68B) elongate, rounded apicolaterally, with a small median cusp at apex; apical sclerotized area (Fig. 68B) subtriangular,
bidentate at anterior margin. Endophallic median bands (Fig. 68B) moderately long; expulsion
hooks (Fig. 68H) separated, each elongate, boot-shaped, angulate or hooked apicolaterally, withanterior plate fused with posterior plate; copulatory tube (Fig. 68B) very slender, with basal
chamber elongate-elliptical, main tube very long, straight. Parameres (Fig. 68B) each very
acutely pointed at apex; apical area moderately long, swollen mesially at base, strongly narrowed
toward apex, furnished mesially with 10 to 11 short and 1 to 2 long setae.
Female: Eighth ventrite (Fig. 68E) obtusely angulate posteromedially; 9th tergum (Fig. 68C)
moderately protruded posterolaterally; gonocoxites (Fig. 68F) toothed posteriorly, each with apicolateral tooth very long, acutely pointed, apicolateral setae moderately long; 10th tergum (Fig.
68C) entire. Spermatheca (Fig. 68G) stout, with capsule spherical, moderately large; apicalchamber moderately large; duct short with 2 distinct turns, the duct from the opening to 1st turnthickened proximally.
Biology and ecology. S. acerrimus is distributed in the mountainous regions of Honshu. The
beetles inhabit leaf litter in the natural forests.
Remarks. S. acerrimus is allied to S. cucumeroides, but it is separable from the latter species
by the aedeagal median lobe with its apical sclerotized area shorter (Fig. 68B), and the spermatheca with its duct longer and simply twice bent (Fig. 68G). S. acerrimus seems to be also allied
to S. tenuiculus from Korean, but it is separable from the latter species by the 8th ventrite of malemore deeply emarginate posteriorly (Fig. 68D), the endophallic expulsion hook longer (Fig.
68H), and the spermathecal duct longer, with the duct from the opening to 1st turn thickened
proximally (Fig. 68G).
Stenus cucumeroides Naomi & Puthz(Figs. 69A–H, 107C)
Stenus cucumeroides Naomi & Puthz, 2006: 83; Naomi & Puthz, 2013: 141.
Type material examined. Holotype: ♀ (CBM), Mt. Kyogatake, Fukui Pref., 26. vii. 1978, H.
Sasaji leg. Paratypes: 1 ♂ (cN), Shimouchinami, Fukui Pref., 9. vi. 1974, H. Sasaji leg.; 5 ♂3 ♀
(cN), Mt. Utatsu, Kanazawa City, Ishikawa Pref., 11. v. 1958, S. Takaba leg.; 1 ♀ (cN), Kuroisawa, Mt. Ena, Gifu Pref., 2. viii. 1994, I. Kiriyama leg.; 1 ♀ (cN), Midoridani, Gifu Pref., 5. v.
1955, I. Bito leg.
Other material examined. [HONSHU]: 2 ♂, Togohara, Sakai City, Fukui Pref., 12. iv. 1998.
Distribution. Japan: Honshu (Fukui, Ishikawa and Gifu Prefs.).
Redescription. Male and female: Body 5.2–5.6 mm (fore body 2.3–2.6 mm) in length, withantennae moderately long, very thin. Head black; pronotum, elytra and abdomen dark chocolate166

Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

Fig. 69. Stenus cucumeroides Naomi & Puthz (A–C, H, Shimouchinami, Fukui; D, F, Ena, Gifu; E, G, Kyogatake, Fukui). A, 9th ventrite of male; B, aedeagus; C, posterior part of 8th ventrite of male; D, E, posterior
part of 9th gonocoxite; F, G, spermatheca; H, expulsion hooks. Scale 1: 0.2 mm for A, B, 0.1 mm for D–H;
Scale 2: 0.25 mm for C.

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167

brown; labrum dark red to black; antennae and legs yellowish brown to reddish brown. Headhardly or very weakly concave, with a pair of distinct longitudinal furrows; punctures round,very dense, small, almost regular. Pronotum with surface uneven; punctures round, very dense,
moderately large, somewhat coarse. Elytra with surface almost even, ﬂat near suture; puncturesround to elliptical, very dense, large, sometimes two punctures partially fused. Tarsi each with
4th tarsomere strongly bilobed. Abdomen with punctures round, moderately dense, small in anterior segments, while punctures in posterior segments sparse to moderately dense, very small tosmall, almost regular. Lateroventrites missing; tergoventrite sutures very thin.
Male: Seventh ventrite posteromedially with a bell-shaped ﬂat area; 8th ventrite (Fig. 69C)
posteromedially with a moderately deep emargination; 9th tergum with antecostal apophyses
moderately long; 9th ventrite (Fig. 69A) distinctly serrate posteriorly, with macrosetae relatively
short, apicolateral teeth long, acutely pointed, apicolateral setae moderately long; 10th tergum
entire. Aedeagal median lobe (Fig. 69B) elongate, gently rounded apicolaterally, with a verysmall median cusp at apex; apical sclerotized area (Fig. 69B) subtriangular, bidentate anteriorly.
Endophallic median bands (Fig. 69B) long, thin; expulsion hooks (Fig. 69H) separated, eachnearly ear-shaped, with anterior plate fused with posterior plate; copulatory tube (Fig. 69B) slender, with basal chamber elongate-elliptical, main tube very long, thin, straight. Parameres (Fig.
69B) thin, slender, very acutely pointed at apex; apical area relatively short, distinctly swollen
mesially at base, each strongly narrowed at apex, furnished mesially with 17 to 19 short and 1 to
2 long setae.
Female: Eighth ventrite obtusely angulate posteriorly; 9th gonocoxites (Fig. 69D, E) toothed
posteriorly, each with apicolateral tooth very long, acutely pointed, apicolateral setae moderately
long. Spermatheca (Fig. 69F, G) stout, with capsule spherical, moderately large; apical chamber
spherical to pyriform, a little larger than capsule; duct short, thick to very thick but once strongly
constricted on its way.
Biology and ecology. S. cucumeroides is distributed in the mountainous regions of the northwestern part of Chubu district, central Honshu. The beetles inhabit leaf litter in the natural forests.
Remarks. S. cucumeroides is closely allied to S. acerrimus, but it is separable from the latter
species by the aedeagal median lobe with its apical sclerotized area longer (Fig. 69B), and thespermatheca with its duct shorter, having a strong constriction on its way (Fig. 69F).
Stenus unagi Hromádka(Figs. 70A–I, 107D)
Stenus unagi Hromádka, 1979: 105; Herman, 2001: 2426; Naomi & Puthz, 2013, 141.
Stenus ookami Hromádka:1979: 106: Puthz, 1993a: 145 (synonym of S. unagi).
Type material examined. Holotype of S. unagi Hromádka: ♂ (NMP), Mt. Iwawaki, Osaka,
21. xii. 1953, Col. K. Sawada.
Holotype of S. ookami Hromádka: ♂ (NMP), Mt. Iwawaki, Osaka, 25. vi. 1954, Col. K.
Sawada.
Other material examined. [HONSHU]: 1 ♀, Sekigahara, Gifu Pref., 15. ix. 1988, T. Ito leg.;1 ♀, Mt. Iwawaki, Osaka Pref., 17. iv. 1966, T. Ito leg.; 1 ♀, same locality, 30. iv. 1986, T. Itoleg.; 1 ♂, same locality, 12–17. ix. 1991, T. Kishimoto leg.; 1 ♂1 ♀, Mt. Kasuga, Nara Pref., 15.
i. 1988, T. Ito leg.; 1 ♀, same locality, 16. vi. 1984, T. Ito leg.; 2 ♂, Mt. Katsuragi, Wakayama

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Fig. 70. Stenus unagi Hromádka (A, I, Katsuragi, Wakayama; B, C, F, H, Iwawaki, Osaka; D, E, G, Kasuga,Nara). A, 9th ventrite of male; B, aedeagus; C, posterior part of 8th ventrite of male; D, posterior part of 8th
ventrite of female; E, F, posterior part of gonocoxite; G, H, spermatheca; I, expulsion hooks. Scale 1: 0.2 mm
for A, B, 0.1 mm for E–I; Scale 2: 0.25 mm for C, D.

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Pref., 13. v. 1993, I. Matoba leg.; 1 ♂, Hashimoto City, Wakayama Pref., 6. i. 1993, I. Matoba
leg.; 1 ♀, Mt. Ryugadake, Daian-cho, Mie Pref., 23. x. 1993, H. Yokozeki leg.; 1 ♂, Nunobiki
Fall, Kiwa, Mie Pref., 25. v. 1996, H. Yokozeki leg.
Distribution. Japan: Honshu (Kinki district and its neighboring regions).
Redescription. Male and female: Body 4.0–5.2 mm (fore body 2.1–2.3 mm) in length, withantennae moderately long, very thin. Head black; pronotum, elytra and abdomen dark chocolate
brown; labrum dark red; antennae and legs yellowish brown to reddish brown. Head weakly concave, with a pair of broad longitudinal furrows; punctures round, moderately dense to dense,
almost regular. Pronotum with surface almost even; punctures round, very dense, moderately
large, sometimes two or more punctures partially fused. Elytra with surface weakly uneven,almost ﬂat near suture; punctures round to almost round, very dense, somewhat coarse, regular.
Tarsi each with 4th tarsomere strongly bilobed. Abdomen with punctures round, moderately
dense to dense, various in size in anterior segments, while punctures in posterior segments
sparse, very small, regular. Lateroventrites missing; tergoventrite sutures very thin.
Male: Seventh ventrite posteromedially with a bell-shaped ﬂat area; 8th ventrite (Fig. 70C)
posteriorly with a large, broad, deep, arcuate emargination; 9th tergum with antecostal apophyses
long; 9th ventrite (Fig. 70A) serrate posteriorly, with macrosetae long, apicolateral teeth long,acutely pointed, apicolateral setae relatively short; 10th tergum entire. Aedeagal median lobe
(Fig. 70B) elongate, angulate apicolaterally, distinctly pointed at apex; apical sclerotized area
(Fig. 70B) subtriangular, with the posterolateral margin arcuate between the apicolateral cornerand the apex. Endophallic dorsal membrane (Fig. 70B) small, subovoidal; median bands (Fig.
70B) long, rather thin; expulsion hooks (Fig. 70I) separated, each nearly elongate-triangular, very
acutely pointed both at anterior and posterior tips, with anterior plate fused with posterior plate;copulatory tube (Fig. 70B) very slender, basal chamber with two thin rods, main tube long, thin,
attenuate, almost straight. Parameres (Fig. 70B) each moderately narrowed near the middle, very
acutely pointed at apex; apical area long, distinctly swollen mesially at base, strongly narrowed
toward apex furnished mesially with 10 to 12 setae of various length.
Female: Eighth ventrite (Fig. 70D) angulate posteromedially; gonocoxites (Fig. 70E, F)
toothed posteriorly, each with apicolateral tooth very long, acutely pointed, apicolateral setae
long. Spermatheca (Fig. 70G, H) with capsule spherical, moderately large to large; apical chamber subspherical to pyriform, more or less larger than capsule; duct moderately thick and longwith 3 or 4 distinct turns, the duct from the opening to 1st turn very long, almost straight.
Biology and ecology. S. unagi is widely distributed in the plains and low mountainous
regions of Kinki district and its neighboring regions, Honshu. The beetles inhabit leaf litter in thenatural forests.
Remarks. S. unagi is the sister species of S. fugu, and it is separable from the latter species by
the aedeagal median lobe with its apical sclerotized area subtriangular and shorter (Fig. 70B), theendophallic expulsion hook acutely pointed anteriorly, with its anterior plate fused with posterior
plate (Fig. 70I), and the spermatheca with its duct longer (Fig. 70G).
Etymology. The speciﬁc epithet of this species is derived from the “unagi”, which is the Japanese name of “eel”.
Stenus fugu Hromádka(Figs. 71A–I, 107E)
Stenus fugu Hromádka, 1979: 104; Herman, 2001: 2188; Naomi & Puthz, 2013: 141.

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Fig. 71. Stenus fugu Hromádka (A, Inamura, Nara; B, Asuka, Nara; C, E–H, Dorogawa, Nara; D, Nachi,
Wakayama; I, Fujiwara, Mie). A, 9th ventrite of male; B, aedeagus; C, posterior part of 8th ventrite of male;D, posterior part of 8th ventrite of female; E, F, posterior part of gonocoxite; G, H, spermatheca; I, expulsion
hooks. Scale 1: 0.2 mm for A, B, 0.1 mm for E–I; Scale 2: 0.25 mm for C, D.

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Stenus sakana Hromádka, 1979: 107; Naomi, 2006: 88 (synonym of S. fugu).
Type material examined. Holotype of S. fugu: ♀ (NMP), Mt. Nachi, Wakayama Pref., 29. iii.
1952, K. Sawada leg.
Holotype of S. sakana: ♂ (NMP), Asuka, Nara Pref., 1. ix. 1963, K. Sawada leg. Paratype of
S. sakana: ♀ (cP), 1. ix. 1963, Asuka, Nara Pref., Japan, K. Sawada leg.
Other material examined. [HONSHU]: 1 ♀, Sekigahara, Gifu Pref., 15. ix. 1988, T. Ito leg.;1 ♂, Nishihotaka-guchi, Gifu Pref., 11. vi. 1980, S. Naomi leg.; 1 ♂2 ♀, Dorogawa, Nara Pref.,2. vi. 1985, T. Ito leg.; 1 ♂, 24. viii. 1991, same locality, T. Ito leg.; 2 ♀, same locality, 17. vi.
1995, T. Ito leg.; 1 ♂, Mt. Sanjyo, Tenkawa Vil., Nara Pref., 28. vi. 1998, S. Nomura leg.; 1 ♀,Mt. Inamura, Oomine, Nara Pref., 23. vii. 1994, T. Ito leg.; 2 ♂, same locality, 16. vi. 1995, T. Itoleg.; 1 ♀, Oomine, Nara Pref., 1. vi. 1985, T. Ito leg.; 1 ♂1 ♀, Toonomine, Nara Pref., 11. xi.
1993, T. Ito leg.; 1 ♂, Mt. Fujiwara, Mie Pref., 11. viii. 1957, T. Hozumi leg.; 1 ♂, same locality,
21. iv. 1957, T. Hozumi leg.
Distribution. Japan: Honshu (Kinki district and its neighboring regions).
Redescription. Male and female: Body 4.0–5.6 mm (fore body 1.8–2.3 mm) in length, withantennae moderately long, very thin. Head black; pronotum, elytra and abdomen dark chocolate
brown; labrum dark red; antennae and legs yellowish brown to reddish brown. Head weakly concave, with a pair of broad longitudinal furrows; punctures round, moderately dense to dense,
irregular, somewhat umbilicate. Pronotum with surface almost even; punctures round, very
dense, variable in size, somewhat coarse, sometimes two or more punctures partially fused. Elytra with surface almost even, ﬂat near suture; punctures round, very dense, various in size. Femora relatively thick; tarsi each with 4th tarsomere strongly bilobed. Abdomen with puncturesround, moderately dense, small in anterior segments; punctures dense to very dense, small in theanterior area of each posterior segment, while punctures sparse, very small in the posterior areaof each posterior segment. Lateroventrites and tergoventrite sutures missing.
Male: Sixth and 7th ventrites each posteromedially with a bell-shaped ﬂat area, which is very
shallowly emarginate; 8th ventrite (Fig. 71C) posteriorly with a large, broad, triangular emargination; 9th tergum with antecostal apophyses long; 9th ventrite (Fig. 71A) sparsely or hardly serrate posteriorly, with macrosetae long, apicolateral teeth stout, very long, acutely pointed, apicolateral setae moderately long; 10th tergum entire. Aedeagal median lobe (Fig. 71B) moderately
broad, distinctly angulate apicolaterally, acutely pointed at apex; apical sclerotized area (Fig.
71B) almost pentagonal, minutely bidentate anteriorly, with the posterolateral margin arcuate
between the apicolateral corner and the apex. Endophallic dorsal membrane (Fig. 71B) subovoidal; median bands (Fig. 71B) long, thin; expulsion hooks (Fig. 71I) separated, each slender, withthe anterior plate hooked anteromesially, demarcated by a suture from posterior plate, the posterior plate narrowed posteriorly, acutely pointed at apex; copulatory tube (Fig. 71B) very slender,
with basal chamber subovoidal, main tube very long and thin, straight. Parameres (Fig. 71B)
each very acutely pointed at apex; apical area relatively short, distinctly swollen and angulate
mesially at base, furnished mesially with 9 to 10 setae.
Female: Eighth ventrite (Fig. 71D) obtusely angulate posteromedially; gonocoxites (Fig.
71E, F) toothed posteriorly, each with apicolateral tooth very long, very sharply pointed, apicolateral setae moderately long. Spermatheca (Fig. 71G, H) with capsule spherical, large; apicalchamber almost pyriform or fusiform, large; duct moderately long and thick, with 4 to 5 turns.
Biology and ecology. S. fugu is widely distributed in the mountainous regions of Kinki District
and its neighboring regions, central Honshu. The beetles inhabit leaf litter in the natural forests.

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Remarks. S. fugu is the sister species of S. unagi, and it is separable from the latter species by
the aedeagal median lobe with its apical sclerotized area almost pentagonal and longer (Fig.
71B), the endophallic expulsion hook distinctly hooked anteromesially (Fig. 71I), with its anterior plate distinctly demarcated by a suture from posterior plate (Fig. 71I), and the spermathecawith its duct shorter (Fig. 71G, H).
Etymology. The speciﬁc epithet of this species is derived from the “fugu”, which is the Japanese name of “blowﬁsh”.
Stenus ukon Naomi & Puthz(Figs. 72A–H, 107F)
Stenus ukon Naomi & Puthz, 2006: 91; Naomi & Puthz, 2013: 141.
Type material examined. Holotype: ♂ (CBM), Nabetani, Tatsunokuchi-cho, Ishikawa Pref.,30. vi. 1995, Y. Sugie leg. Paratypes: 1 ♀ (cN), same locality, 8. iv. 1995, Y. Sugie leg.; 1 ♀ (cN),same locality, 6. v. 1995, Y. Sugie leg.; 1 ♀ (cN), same locality, 27. v. 1995, Y. Sugie leg.; 1 ♂
(cN), same locality, 2. ix. 1995, Y. Sugie leg.; 1 ♀ (cN), Mt. Rokuman, Kaga-Hakusan, Ishikawa
Pref., 16. vi. 2002, Y. Hayashi leg.; 1 ♂ (cN), Hidari, Ishikawa Pref., 14. v. 1961, Y. Hayashi leg.;1 ♂ (cN), Mt. Horyu, 6. v. 1961, Y. Hayashi leg.; 1 ♀ (cN), Mt. Saiho, Fukui Pref., 29–31. v.
1976, H. Sasaji leg.; 1 ♂ (cN), Kami-jyoho Temple, Eiheiji-cho, Fukui Pref., 9. v. 2010, M. Saito
leg.; 1 ♂1 ♀ (cN), Sekigahara, Gifu Pref., 15. ix. 1988, T. Ito leg.; 1 ♂ (cN), Kawakami,
Sakauchi-mura, Gifu Pref., 17. vii. 1988, I. Kiriyama leg.; 1 ♀, Kosaka, Kuze, Gifu Pref., 20. v.
1996, I. Kiriyama leg.; 1 ♂ (cN), Midoridani, Neo, Gifu Pref., 3. v. 1957, I. Kiriyama leg.; 1 ♀
(cN), Nishihotaka-guchi, Gifu Pref., 11. vi. 1980, S. Naomi leg.
Distribution. Japan: Honshu (Ishikawa, Fukui and Gifu Prefs.).
Redescription. Male and female: Body 4.2–5.6 mm (fore body 2.1–2.6 mm) in length, withantennae moderately long, very thin. Head black; pronotum, elytra and abdomen dark chocolate
brown; labrum dark red; antennae and legs yellowish brown to reddish brown. Head weakly concave, with a pair of broad longitudinal furrows; punctures round, moderately dense to dense,
small, somewhat umbilicate. Pronotum with surface weakly uneven; punctures round to almost
round, very dense, moderately large, partially coarse, sometimes two or more punctures partiallyfused. Elytra almost even, gently rounded dorsally; punctures round, very dense, large. Tarsi eachwith 4th tarsomere strongly bilobed. Abdomen with punctures round, moderately dense to dense,
small, almost regular in anterior segments, while punctures in posterior segments sparse, verysmall, regular. Lateroventrites and tergoventrite sutures missing.
Male: Seventh ventrite medially with a narrow, longitudinal, very shallow depression; 8thventrite (Fig. 72C) posteriorly with a large, broad, subtriangular emargination; 9th tergum with
antecostal apophyses long; 9th ventrite (Fig. 72A) serrate posteriorly, with apicolateral teeth
acutely pointed, apicolateral setae short; 10th tergum entire. Aedeagal median lobe (Fig. 72B)
elongate, weakly swollen laterally near the middle, uniformly rounded apicolaterally, with a long
median cusp at apex; apical sclerotized area (Fig. 72B) nearly semicircular but weakly rounded
anteriorly. Endophallic dorsal membrane (Fig. 72B) subovoidal; median bands (Fig. 72B) very
long, thin; expulsion hooks (Fig. 72H) separated, each with the anterior plate spatulate, distinctly
narrowed at base, demarcated by a suture from posterior plate, the posterior plate turning posterolaterally behind the middle, pointed at tip; copulatory tube very slender, with basal chambersmall, main tube long, attenuate but weakly curved at basal half. Parameres (Fig. 72B) each very

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Fig. 72. Stenus ukon Naomi & Puthz (Nabetani, Ishikawa). A, 9th ventrite of male; B, aedeagus; C, posterior partof 8th ventrite of male; D, E, posterior part of gonocoxite; F, G, spermatheca; H, expulsion hooks. Scale 1:
0.2 mm for A, B, 0.1 mm for D–H; Scale 2: 0.25 mm for C.

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acutely pointed at apex; apical area moderately long, distinctly swollen mesially at base, furnished mesially with 15 to 16 short setae.
Female: Eighth ventrite obtusely angulate posteromedially; gonocoxites (Fig. 72D, E) irregularly toothed posteriorly, each with apicolateral tooth very long, acutely pointed, apicolateral
setae moderately long. Spermatheca (Fig. 72F, G) with capsule spherical, large; apical chamber
pyriform to fusiform, large to very large; duct thick, moderately loosely or moderately tightly
coiled, moderately long with 4 to 8 turns.
Biology and ecology. S. ukon is distributed in the plains and mountainous regions of thenorthwestern part of Chubu district, central Honshu. The beetles inhabit leaf litter in the naturalforests.
Remarks. S. ukon is allied to S. unagi and S. fugu, but it is separable from the latter two species by the aedeagal median lobe weakly swollen laterally near the middle and gently roundedapicolaterally (Fig. 72B), and the endophallic expulsion hook with its anterior plate spatulate anddistinctly narrowed at base (Fig. 72H).
Etymology. The speciﬁc epithet of this new species is derived from the “ukon”, which is theJapanese name of “turmeric”.
Stenus kyushuensis Naomi & Puthz(Figs. 73A–H, 107G)
Stenus kyushuensis Naomi & Puthz, 2006: 74; Naomi & Puthz, 2013: 141.
Type material examined. Holotype: ♂ (CBM), Hakozaki, Fukuoka City, Fukuoka Pref., 12. v.
1979, K. Yamagishi leg. Paratypes: 2 ♂3 ♀ (cN), Mt. Fukuchi, Kitakyushu City, Fukuoka Pref.,H. Hoshina leg.; 1 ♂1 ♀ (cN), Chikushi-yabakei, Nakagawa-cho, Fukuoka Pref., 27. xi. 1994, S.
Nomura leg.; 1 ♀ (cN), Yunoharu, Saga Pref., 20. v. 1979, C. Ohkuma leg.; 1 ♂ (cN), same
locality, 23. v. 1979, C. Ohkuma leg.; 1 ♀ (cN), Ikenoharu Marsh, Saga Pref., 9. ix. 1976, H.
Ohishi leg.; 1 ♂1 ♀ (cN), Mt. Tsubaki, Saga Pref., 2. x. 1977, H. Ohishi leg.; 1 ♀ (cN), Mt.
Seburi, Saga Pref., 3. x. 1976, H. Ohishi leg.
Other material examined. [KYUSHU]: 2 ♂, Mizunashi, Maebaru City, Fukuoka Pref., 24. x.
1994, S. Nomura leg.; 1 ♂1 ♀, Mt. Sefuri, Sefuri Vil., Saga Pref., 9. x. 1994, S. Nomura leg.
Distribution. Japan: Kyushu (Fukuoka and Saga Prefs.).
Redescription. Male and female: Body 4.8–5.8 mm (fore body 2.1–2.7 mm) in length, withantennae moderately long, very thin. Head and abdomen black; pronotum and elytra dark chocolate brown; labrum dark red; antennae and legs yellowish brown to reddish brown. Head weakly
concave, with a pair of broad longitudinal furrows; punctures round, usually moderately dense todense but sometimes very dense, small. Pronotum with surface weakly uneven; punctures roundto almost round, very dense, moderately large, somewhat coarse. Elytra with surface weakly
depressed at humeri, almost ﬂat near suture; punctures round to almost round, very dense, moderately large to large, somewhat coarse. Tarsi each with 4th tarsomere strongly bilobed. Abdomen with punctures round, dense, small, regular in anterior segments, while punctures in posterior segments sparse, very small, regular. Lateroventrites and tergoventrite sutures almost
missing.
Male: Seventh ventrite posteromedially with a subtriangular ﬂat area, which is very shallowly emarginate; 8th ventrite (Fig. 73C) posteriorly with a shallow, arcuate emargination; 9th
tergum with antecostal apophyses relatively short; 9th ventrite (Fig. 73A) broad but strongly nar-

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Fig. 73. Stenus kyushuensis Naomi & Puthz (A, B, H, Hakozaki, Fukuoka; C, Fukuchi, Fukuoka; D, E, G, Ikenoharu, Saga; F, Seburi, Fukuoka). A, 9th ventrite of male; B, aedeagus; C, posterior part of 8th ventrite of male;
D, E, posterior part of gonocoxite; F, G, spermatheca; H, expulsion hooks. Scale 1: 0.2 mm for A, B, 0.1 mm
for D–H; Scale 2: 0.25 mm for C.

rowed anteriorly in about basal 2/5, weakly serrate posteriorly, with macrosetae long, apicolateral
teeth long, acutely pointed, apicolateral setae moderately long; 10th tergum weakly emarginate

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posteriorly. Aedeagal median lobe (Fig. 73B) slender, obtusely angulate apicolaterally, pointed atapex; apical sclerotized area (Fig. 73B) subtriangular, bidentate anteriorly. Endophallic medianbands (Fig. 73B) relatively short, thin; expulsion hooks (Fig. 73H) separated, each almost elongate-quadrangular, shallowly emarginate posteriorly; copulatory tube (Fig. 73B) with basal
chamber elongate-ovoidal, main tube with the basal tube stout, thick, broad, distinctly angulate
posterolaterally, and the apical tube thin and baculiform but weakly constricted at base and beakshaped at apex. Parameres (Fig. 73B) almost straight, each very acutely pointed at apex; apicalarea long, moderately swollen and angulate mesially at base, furnished mesially with 6 to 8 shortand 1 to 2 long setae.
Female: Eighth ventrite obtusely angulate posteromedially; gonocoxites (Fig. 73D, E) irregularly toothed posteriorly, each with apicolateral tooth very long, acutely pointed, apicolateral
setae long. Spermatheca (Fig. 73F, G) with capsule spherical (Fig. 73F) or ovoidal (Fig. 73G),
very large; apical chamber almost missing; duct thick, short with two distinct turns.
Biology and ecology. S. kyushuensis is distributed in the plains and mountainous regions ofnorthern Kyushu. The beetles inhabit leaf litter in the natural forests.
Remarks. S. kyushuensis is allied to S. tanuki, but it is separable from the latter species by theaedeagal median lobe narrower especially at the apical part, with its apical sclerotized area longer (Fig. 73B), the endophallic copulatory tube with its main tube much thicker in about basal
half to form the basal tube (Fig. 73B), and the spermatheca with its duct longer and thicker, but
its apical chamber almost missing (Fig. 73F).
Stenus tanuki Hromádka(Figs. 74A–H, 107H)
Stenus tanuki Hromádka, 1979: 107: Naomi, 2006: 64 (synonym of S. indubius); Naomi & Ito,
2015: 213 (revalidated as good species).
Stenus wakayamanus Puthz, 2001a: 44; Puthz & Naomi, 2013: 141; Naomi & Ito, 2015: 213(synonym of S. tanuki).
Type material examined. Holotype of S. tanuki: ♂ (NMP), Hiraoka, Osaka, Kinki Distr., 1. v.
1954, K. Sawada leg.
Holotype of S. wakayamanus: ♀ (cP), Hirai, Wakayama Pref., 14. vii. 1999, V. Puthz leg.
Paratypes of S. wakayamanus: 1 ♂1 ♀ (cN), same data as holotype; 1 ♂ (cN), Mt. Nachi(350 m), Wakayama Pref., 13. vii. 1999, V. Puthz leg.
Other material examined. [HONSHU]: 1 ♀, Tategasaki, Kumano City, Mie Pref., 28. i. 1995,
H. Yokozeki leg.; 2 ♂, Mt. Gomanodan, Wakayama Pref., 11. vi. 1996, I. Matoba leg.; 1 ♂, same
locality, 14. vi. 1994, I. Matoba leg.; 1 ♀, Yunomine, Hongu-cho, Wakayama Pref., 27. xii. 1992,
I. Matoba leg.; 1 ♂, Tanago, Kumanogawa-cho, Wakayama Pref., 18. iv. 1985, I. Matoba leg.;1 ♂, Mizukami, Nakahechi-cho, Wakayama Pref., 2. vi. 1995, I. Matoba leg.; 2 ♂, Mt. Ohto,
Wakayama Pref., 28–29. vi. 1981, S. Naomi leg.; 1 ♂2 ♀, Hoihoi Valley, Mt. Ohto, Wakayama
Pref., 6. v. 1994, S. Nomura leg.; 1 ♀, Mt. Katsuragi, Wakayama Pref., 13. v. 1993, I. Matoba
leg.; 1 ♂, Mt. Kongo, Gose City, Nara Pref., 4. vii. 1998, T. Kishimoto leg.; 1 ♂1 ♀, Mt. Kojin,
Nara Pref., 30. vii. 1995, T. Ito leg.; 1 ♂1 ♀, Mt. Wasamata, Kami-kitayama, Nara Pref., 11. vii.
1999, M. Maruyama leg.; 1 ♂, Mt. Obako, Nosegawa Vil., Nara Pref., 7. v. 1994, S. Nomura
leg.; 1 ♂1 ♀, Mt. Kongo, Osaka, 21. v. 1989, K. Yamazaki leg.; 1 ♀, Hyogo Pref., 19. v. 1982.
Distribution. Japan: Honshu (Kinki district).

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Fig. 74. Stenus tanuki Hromádka (A, B, H, Gomanodan, Wakayama; C, Hirai, Wakayama; D, F, G, Yunomine,
Wakayama; E, Katuragi, Wakayama). A, 9th ventrite of male; B, aedeagus; C, posterior part of 8th ventrite ofmale; D, G, posterior part of gonocoxite; E, F, spermatheca; H, expulsion hooks. Scale 1: 0.2 mm for A, B,
0.1 mm for D–H; Scale 2: 0.25 mm for C.

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Redescription. Male and female: Body 3.9–5.4 mm (fore body 2.0–2.3 mm) in length, withantennae moderately long, very thin. Head black; pronotum, elytra and abdomen dark chocolate
brown; labrum dark red to black; antennae and legs yellowish brown to reddish brown. Headweakly concave, with a pair of broad longitudinal furrows; punctures round, moderately dense todense, small, somewhat umbilicate. Pronotum with surface weakly uneven; punctures round,very dense, moderately large, somewhat coarse. Elytra with surface almost even or weakly
uneven; punctures round, very dense, large. Tarsi each with 4th tarsomere strongly bilobed.
Abdomen with punctures round to elliptical, moderately dense, various in size in anterior segments, while punctures in posterior segments sparse, very small, almost regular. Lateroventrites
and tergoventrite sutures missing.
Male: Eighth ventrite (Fig. 74C) posteriorly with a broad, arcuate emargination; 9th tergum
with antecostal apophyses moderately long; 9th ventrite (Fig. 74A) irregularly serrate posteriorly,
with macrosetae relatively short, apicolateral teeth long, acutely pointed, apicolateral setae moderately long; 10th tergum weakly emarginate posteriorly. Aedeagal median lobe (Fig. 74B) moderately broad, angulate apicolaterally, pointed at apex; apical sclerotized area (Fig. 74B) broadtriangular, arcuately emarginate anteriorly. Endophallic dorsal membrane (Fig. 74B) transverse,
elliptical to fusiform; median bands (Fig. 74B) long, thin; expulsion hooks (Fig. 74H) separated,each with the anterior plate rounded apically, demarcated by a transverse suture from, and muchsmaller than posterior plate, the posterior plate projecting posterolaterally, truncate posteriorly;
copulatory tube (Fig. 74B) very slender, with basal chamber thin, main tube very thin, attenuate,
straight. Parameres (Fig. 74B) each very acutely pointed at apex; apical area long, moderately
swollen mesially at base, furnished mesially with 12 to 13 setae of various length.
Female: Eighth ventrite almost rounded posteriorly; gonocoxites (Fig. 74C, G) toothed posteriorly, each with apicolateral tooth very long, acutely pointed, apicolateral setae moderately
long. Spermatheca (Fig. 74E, F) with capsule ovoidal or elliptical, large to very large; apicalchamber pyriform, large; duct thick, very short with two distinct turns.
Biology and ecology. S. tanuki is distributed in the mountainous regions of Kinki district,Honshu. The beetles inhabit leaf litter in the natural forests.
Remarks. S. tanuki is allied to S. kyushuensis, but it is separable from the latter species by theaedeagal median lobe broader especially at the apical part, with its apical sclerotized area shorter(Fig. 74B), the endophallic copulatory tube with its main tube simply attenuate (Fig. 74B), andthe spermatheca with its duct much shorter, and its apical chamber pyriform (Fig. 74E).
Etymology. The speciﬁc epithet of this new species is derived from the “tanuki”, which is theJapanese name of “raccoon dog”.
Stenus hypovelox Naomi & Puthz(Figs. 75A–H, 107I)
Stenus hypovelox Naomi & Puthz, 2006: 76; Naomi & Puthz, 2013: 141.
Type material examined. Holotype: ♂ (CBM), Oku-dogo, Ehime Pref., 2. vi. 1989, T. Ito leg.
Paratypes: 2 ♀ (cN), same data as holotype; 1 ♀ (MHNG), Mt. Ishizuchi, Ehime Pref., Japon,
13–14. viii. 1980, Cl. Besuchet leg.; 1 ♂1 ♀ (cN), same locality, 16. vi. 1981, S. Naomi leg.; 1 ♀
(cN), Komenono, Ehime Pref., 18. vi. 1978, A. Oda leg; 1 ♂1 ♀, Mt. Kamegamori, Saijyo City,
Ehime Pref., 1650 m, 11–18. viii. 1980, S. & J. Peck leg.; 1 ♀, Mt. Tsutsujo, Omogo Vil., Ehime
Pref., 1600 m, 11–18. viii. 1980, S. & J. Peck leg.; 1 ♀ (cP), Ehime, M. Sakai leg.; 1 ♂ (cP),The Steninae of Japan Part 2

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Fig. 75. Stenus hypovelox Naomi & Puthz (A, B, D, E, G, H, Ishizuchi, Ehime; C, Okudogo, Ehime; F,
Omogokei, Ehime). A, 9th ventrite of male; B, aedeagus; C, posterior part of 8th ventrite of male; D, E, posterior part of gonocoxite; F, G, spermatheca; H, expulsion hooks. Scale 1: 0.2 mm for A, B, 0.1 mm for D–H;
Scale 2: 0.25 mm for C.

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Ehime, Peck leg.
Distribution. Japan: Shikoku (Ehime Pref.).
Redescription. Male and female: Body 4.5–5.2 mm (fore body 2.1–2.6 mm) in length, withantennae moderately long, very thin. Head black; pronotum, elytra and abdomen dark chocolate
brown; labrum dark red to black; antennae and legs yellowish brown to reddish brown. Headweakly concave, with a pair of broad longitudinal furrows; punctures moderately dense to dense,
irregular, somewhat umbilicate. Pronotum with surface weakly uneven; punctures round toalmost round, very dense, various in size, sometimes two or more punctures partially fused. Elytra with surface weakly uneven to uneven, almost ﬂat near suture; punctures round, very dense,
moderately large to large, sometimes coarse. Tarsi each with 4th tarsomere strongly bilobed.
Abdomen with punctures round, moderately dense, small to moderately large in anterior segments, while puncture in posterior segments very small, moderately dense, regular. Lateroventrites and tergoventrite sutures missing.
Male: Eighth ventrite (Fig. 75C) posteromedially with a broad, arcuate emargination; 9th tergum with antecostal apophyses relatively short; 9th ventrite (Fig. 75A) serrate posteriorly, withmacrosetae short, apicolateral teeth long, pointed, apicolateral setae short; 10th tergum almost
entire. Aedeagal median lobe (Fig. 75B) elongate, slender, gently rounded or very weakly angulate at apicolateral corners, distinctly pointed at apex; apical sclerotized area (Fig. 75B) triangular, bidentate anteriorly; median bands (Fig. 75B) relatively short, very thin; expulsion hooks(Fig. 75H) separated, each with the anterior plate sharply hooked at anterior tip, demarcated byan oblique suture from posterior plate, the posterior plate almost truncate posteriorly, pointed
posterolaterally; copulatory tube (Fig. 75B) slender with basal chamber with two thin rods of different length, main tube long, baculiform, straight. Parameres (Fig. 75B) each very acutely
pointed at apex; apical area long, moderately swollen mesially at base, furnished mesially with 8
to 9 setae of various length.
Female: Eighth ventrite almost rounded posteriorly; gonocoxites (Fig. 75D, E) distinctly
toothed posteriorly, each with apicolateral tooth very long, acutely pointed, apicolateral setae
moderately long. Spermatheca (Fig. 75F, G) with capsule ovoidal to subovoidal, moderately
large; apical chamber nearly pyriform, moderately large; duct very long, moderately tightly ortightly coiled, usually thin but the duct from the opening to 1st turn moderately thick.
Biology and ecology. S. hypovelox is distributed in the mountainous regions of the northwestern part of Shikoku. The beetles inhabit leaf litter in the natural forests.
Remarks. S. hypovelox seems to be allied to S. kyushuensis and S. tanuki, but it is separablefrom the latter two species by the aedeagal median lobe with its apicolateral corners only indistinctly recognizable (Fig. 75B), the endophallic expulsion hook with its anterior plate sharply
hooked (Fig. 75H), and the spermatheca with its duct much longer and thinner (Fig. 75F).
Stenus sawadai Hromádka(Figs. 76A–L, 107J)
Stenus sawadai Hromádka, 1979: 108; Herman, 2001: 2379; Naomi, 2006: 93; Naomi & Puthz,
2013: 141.
Type material examined. Holotype: ♂ (NMP), Sasayama, Hyogo Pref., Japan, 18. vii. 1956,
Y. Icho leg. Paratypes: 1 ♂ (cP), Mt. Hiei, Kyoto, 10. iii. 1968, K. Sawada leg.; 1 ♂ (cP), Katuoji, Minoo, Osaka, 13. iv. 1954, K. Sawada leg.

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Fig. 76. Stenus sawadai Hromádka (A, Myoken, Osaka; B, F, Koraibiro, Mie; C, G, Minamimata, Mie; D, L,
Iwakura, Kyoto; E, Ashiu, Kyoto; H, Daihi, Kyoto; I, Mizuho, Kyoto; J, K, Uji, Kyoto). A, aedeagus; B, C,
median lobe; D, 9th ventrite of male; E–G, expulsion hooks; H, I, spermatheca; J, K, posterior part of gonocoxite; L, posterior part of 8th ventrite of male. Scale 1: 0.2 mm for A–D, 0.1 mm for E–K; Scale 2: 0.25 mm
for L.

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Other material examined. [HONSHU]: 1 ♂1 ♀, Koraibiro, Ise City, Mie Pref., 10. i. 1998, H.
Ichihashi leg.; 2 ♀, Nishikikisei, Watarai, Mie Pref., 1. ii. 1997, A. Amagasu leg.; 1 ♂1 ♀, Mt.
Minamimata, Ohuchiyama, Mie Pref., 12. x. 1997, K. Kanno leg.; 2 ♂, Watari, Mie Pref., 18. xii.
1986, A. Amagasu leg.; 1 ♂1 ♀, Mt. Hiei, Shiga Pref., 9. xii. 1984, T. Ito leg.; 1 ex. (cP),
Higashiyama, Pref. Kyoto, 23. iii. 1968, K. Sawada; 1 ♂1 ♀, Ashiu, Kyoto., 5. ix. 1992, T. Itoleg.; 2 ♂, Iwakura, Kyoto.,10–11. iv. 1981, T. Ogata leg.; 1 ♂1 ♀, Gounho, Uji City, Kyoto., 8.
ii. 1997, S. Takahashi leg.; 1 ♀, Yawata, Kyoto, 7. xii. 1986, T. Ito leg.; 1 ♀, Hanase, Kyoto., 20.
x. 1987, T. Ito leg.; 1 ♀, same locality, 2. x. 1987, T. Ito leg.; 2 ♂, same locality, 26. x. 1991, T.
Ito leg.; 1 ♀, Mizuho, Kyoto., 2. vii. 1989, T. Ito leg.; 1 ♂, same locality, 23. xi. 1989, T. Ito leg.;1 ♂1 ♀, Mt. Daihi, Kyoto., 2. xi. 1965, T. Ito leg.; 1 ♂, Oomi-Ogose, Ashibidani, Kyoto., 21. vi.
1967, M. Tomokuni leg.; 1 ex. (cZ), Mt. Myoken, Osaka, Japan, 25. vi. 1993, N. Ito leg; 1 ex.
(cZ), same locality, 19. ix. 1994, N. Ito leg.; 1 ♂1 ♀, same locality, 5. v. 1986, T. Ito leg.; 1 ♂,Sasayama, Hyogo Pref., 18. ix. 1983, T. Ito leg.;
Distribution. Japan: Honshu (Kinki district).
Redescription. Male and female: Body 3.9–4.8 mm (fore body 2.0–2.6 mm) in length, withantennae moderately long, very thin. Head and abdomen black; pronotum and elytra dark chocolate brown; labrum dark red; antennae and legs yellowish brown to reddish brown. Head weakly
concave, with a pair of broad longitudinal furrows; punctures round, moderately dense to dense,
small, somewhat umbilicate. Pronotum with surface weakly uneven or almost even; puncturesround, very dense, moderately large, somewhat coarse. Elytra with surface weakly uneven; punctures round to almost round, very dense, various in size, coarse, sometimes two or more punctures partially fused. Tarsi each with 4th tarsomere strongly bilobed. Abdomen with puncturesround, sparse to moderately dense, small in anterior segments, while punctures in posterior segments sparse, very small, regular. Lateroventrites and tergoventrite sutures missing.
Male: Seventh ventrite posteromedially with a bell-shaped or subtriangular, ﬂat area; 8thventrite (Fig. 76L) posteromedially with a shallow, arcuate emargination; 9th tergum with antecostal apophyses moderately long; 9th ventrite (Fig. 76D) minutely serrate posteriorly, with macrosetae moderately long, apicolateral teeth very long, acutely pointed, apicolateral setae moderately long; 10th tergum almost entire. Aedeagal median lobe (Fig. 76A–C) moderately broad,angulate apicolaterally, tricuspidate at apex; apical sclerotized area (Fig. 76A–C) transverse,
basically trapezoidal but various in shape, with median cusp long, thin, pointed, lateral cusp
existing as angulation. Endophallic median bands (Fig. 76A) each moderately long, thin; expulsion hooks (Fig. 76E–G) separated, each elongate, almost cucumber-shaped, more or less pointed
at anterior tip, with anterior plate fused with posterior plate; copulatory tube (Fig. 76A) very
slender, with basal chamber having two rods of different length, main tube very thin, long, attenuate. Parameres (Fig. 76A) each very acutely pointed at apex; apical area long, moderately swollen mesially at base, furnished mesially with 11 to 12 setae.
Female: Eighth ventrite almost rounded posteriorly; gonocoxites (Fig. 76J, K) toothed posteriorly, each with apicolateral tooth very long, acutely pointed, apicolateral setae moderately long.
Spermatheca (Fig. 76H, I) with capsule spherical, large; apical chamber almost pyriform, large;
duct long, relatively thin, tightly, irregularly coiled.
Biology and ecology. S. sawadai is a common species; and it is widely distributed in theplains and low mountainous regions of Kinki district, Honshu. The beetles inhabit leaf litter in
the natural forests.
Remarks. S. sawadai is allied to S. kishimotoi and S. yokozekii, but it is separable from thelatter species by the aedeagal median lobe tricuspidate and narrower (Fig. 76A–C), and the endo-

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phallic expulsion hook a little broader, with its anterior part only weakly curved laterally (Fig.
76E–G). This species shows the slight variations regarding the apical part of aedeagal median
lobe among the local populations (Fig. 76A–C; see also Naomi, 2006).
Etymology. This species is named in honor of Dr. Kohei Sawada (Takatsuki, Osaka).
Stenus kishimotoi Naomi & Puthz(Figs. 77A–H, 107K)
Stenus kishimotoi Naomi & Puthz, 2006: 97; Naomi & Puthz, 2013: 141.
Type material examined. Holotype: ♀ (CBM), Mt. Takao, Haibara-cho, Shizuoka Pref., 11.
iv. 1994, T. Kishimoto leg. Paratypes: 1 ♂ (cN), same data as holotype; 1 ♀ (cN), Mt. Sobatsubu,
Nakakawane T., Shizuoka Pref., 9. ix. 2004, T. Watanabe leg.; 1 ♀ (cN), Mt. Sanage, Toyota
City, Aichi Pref., 21. iv. 1991, T. Hozumi leg.; 2 ♂1 ♀ (cN), Togashima, Yukinoura, Owase City,
Mie Pref., 4. v. 1996, H. Yokozeki leg.; 1 ♂1 ♀ (cN), Nasazaki, Kuki-cho, Owase City, Mie
Pref., 4. iv. 1998, F. Ichikawa & H. Yokozeki leg.; 2 ♀ (cN), Sugari-cho, Owase City, Mie Pref.,19. i. 1997, A. Amagasu & F. Ichikawa leg.
Other material examined. [HONSHU]: 1 ♂, Kukizaki, Owase City, Mie Pref., 5. i. 1993, H.
Yokozeki leg.
Distribution. Japan: Honshu (Shizuoka, Aichi and Mie Prefs.).
Redescription. Male and female: Body 4.6–5.0 mm (fore body 2.1–2.5 mm) in length, withantennae moderately long, very thin. Head and abdomen black; pronotum and elytra dark chocolate brown; labrum dark red; antennae and legs yellowish brown to reddish brown. Head weakly
concave, with a pair of broad longitudinal furrows; punctures round, moderately dense to dense,
small, somewhat umbilicate. Pronotum with surface weakly uneven to almost even; puncturesround, very dense, various in size. Elytra with surface almost even, ﬂat near suture; puncturesround to almost round, very dense, various in size, somewhat coarse. Tarsi each with 4th tarsomere strongly bilobed. Abdomen with punctures round, sparse to moderately dense, small,almost regular in anterior segments, while punctures in posterior segments very sparse to sparse,
very small, shallow, almost regular. Lateroventrites missing; tergoventrite sutures very thin oralmost missing.
Male: Sixth ventrite posteromedially with a small, bell-shaped ﬂat area; 7th ventrite posteromedially with a large, bell-shaped ﬂat area; 8th ventrite (Fig. 77C) posteromedially with a broad,arcuate emargination; 9th tergum with antecostal apophyses moderately long; 9th ventrite (Fig.
77A) minutely serrate posteriorly, with macrosetae very long, apicolateral teeth stout, long,acutely pointed, apicolateral setae moderately long; 10th tergum almost entire. Aedeagal median
lobe (Fig. 77B) broad, broadest at about basal 2/5, weakly constricted before apicolateral corners, obtusely angulate or rounded at apicolateral corners, simply pointed at apex; apical sclerotized area (Fig. 77B) almost broad-triangular, arcuately emarginte anteriorly. Endophallic medianbands (Fig. 77B) each long, moderately broad; lateral bands (Fig. 77B) each broad at base;
expulsion hooks (Fig. 77H) separated, each thin, cucumber-shaped, pointed posterolaterally, withanterior plate almost fused with posterior plate; copulatory tube (Fig. 77B) very slender, basal
chamber with two rods of different length, main tube long, thin, attenuate. Parameres (Fig. 77B)
thick, each very acutely pointed at apex; apical area long, moderately swollen mesially at base,strongly narrowed toward apex, furnished basally with 6 to 9 short, thin setae, and apically with
2 moderately long setae.

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Fig. 77. Stenus kishimotoi Naomi & Puthz (A–C, F–H, Owase, Mie; D, E, Toyota, Aichi). A, 9th ventrite ofmale; B, aedeagus; C, posterior part of 8th ventrite of male; D, E, posterior part of gonocoxite; F, G, spermatheca; H, expulsion hooks. Scale 1: 0.2 mm for A, B, 0.1 mm for D–H; Scale 2: 0.25 mm for C.

Female: Eighth ventrite almost rounded posteriorly; gonocoxites (Fig. 77D, E) toothed posteriorly, each with apicolateral tooth very long, stout, acutely pointed, apicolateral setae moderately long. Spermatheca (Fig. 77F, G) with capsule spherical, large; apical chamber pyriform toelongate-pyriform, large; duct extending anteriorly a little before or behind the apical margin of
apical chamber, moderately long, almost tightly coiled, usually thin but the duct from the open-

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ing to 1st turn varying in thickness (thin to thick or very thick).
Biology and ecology. S. kishimotoi is distributed in the plains and mountainous regions of thesouthern part of Chubu district and the eastern part of Kansai district, central Honshu. S. kishimotoi and S. yokozekii seem to be almost sympatrically distributed in the eastern part of Kinki district (e.g., Owase City). The beetles of this species inhabit the leaf litter in the natural forests.
Remarks. S. kishimotoi is the sister species of S. yokozekii, and it is separable from the latter
species by the aedeagal median lobe broadest at about basal 2/5 (Fig. 77B), the endophallic
expulsion hook sharply pointed posterolaterally (Fig. 77H), and the spermatheca with its duct
extending anteriorly a little before or behind the apical margin of apical chamber (Fig. 77F).
Etymology. This species is named in honor of Dr. Toshio Kishimoto (Museum of Natural andEnvironmental History, Shizuoka), who studies the Staphylinidae.
Stenus yokozekii Naomi(Figs. 78A–H, 107L)
Stenus yokozekii Naomi, 2006: 99; Naomi & Puthz, 2013: 141.
Type material examined. Holotype: ♂ (CBM), Sugari, Owase, Mie Pref., 19. i. 1997, F.
Ichikawa leg. Paratypes: 1 ♂4 ♀ (cN), same data as holotype, A. Amagasu & F. Ichikawa leg.;1 ♀ (cN), same locality, 13. i. 1996, H. Yokozeki leg.; 1 ♀, Sengokugoe, Ohuchiyama Vil., Mie
Pref., 10. iv. 1994, H. Yokozeki leg.; 1 ♀ (cN), Kyoto, Japan, 23. v. 1988.
Other material examined. [HONSHU]: 1 ♂, same locality as holotype, 19. i. 1997, H.
Yokozeki leg.
Distribution. Japan: Honshu (Kyoto and Mie Prefs.).
Redescription. Male and female: Body 4.6–5.1 mm (fore body 2.1–2.3 mm) in length, withantennae moderately long, very thin. Head black; pronotum, elytra and abdomen dark chocolate
brown; labrum dark red; antennae and legs yellowish brown to reddish brown. Head weakly concave, with a pair of longitudinal furrows; punctures round to almost round, moderately dense todense, small, somewhat umbilicate. Pronotum with surface weakly uneven to almost even; punctures round, very dense, various in size. Elytra with surface almost even, ﬂat near suture; punctures round to almost round, very dense, various in size, somewhat coarse. Tarsi each with 4thtarsomere strongly bilobed. Abdomen with punctures round, moderately dense, small, almost
regular in anterior segments, while punctures in posterior segments sparse, very small, almost
regular. Lateroventrites missing; tergoventrite sutures indistinct or almost missing.
Male: Seventh ventrite posteromedially with a bell-shaped ﬂat area; 8th ventrite (Fig. 78C)
posteromedially with a broad, arcuate emargination; 9th tergum with antecostal apophyses moderately long; 9th ventrite (Fig. 78A) minutely serrate posteriorly with an almost U-shaped emargination between apicolateral teeth, and with macrosetae relatively short, apicolateral teeth stout,
long, acutely pointed, apicolateral setae relatively long; 10th tergum shallowly emarginate posteriorly. Aedeagal median lobe (Fig. 78B) broad, broadest and obtusely angulate at apicolateralcorner, pointed at apex; apical sclerotized area (Fig. 78B) almost broad-triangular. Endophallic
median bands (Fig. 78B) moderately long, thin; lateral bands (Fig. 78B) each broad at base;
expulsion hooks (Fig. 78H) separated, each thin, cucumber-shaped, weakly pointed posterolaterally, with anterior plate almost fused with posterior plate; copulatory tube (Fig. 78B) very slender, with basal chamber having two rods of different length, main tube long, thin but very weakly
broadened at apex. Parameres (Fig. 78B) each very acutely pointed at apex; apical area long,

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Fig. 78. Stenus yokozekii Naomi (Owase, Mie). A, 9th ventrite of male; B, aedeagus; C, posterior part of 8th ventrite of male; D, E, posterior part of gonocoxite; F, G, spermatheca; H, expulsion hooks. Scale 1: 0.2 mm for
A, B, 0.1 mm for D–H; Scale 2: 0.25 mm for C.

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weakly swollen mesially at base, strongly narrowed toward apex, furnished basally with 8 to 9
short, thin setae, and apically with 2 moderately long setae.
Female: Eighth ventrite almost rounded posteriorly; gonocoxites (Fig. 78D, E) toothed posteriorly, each with apicolateral tooth very long, acutely pointed, apicolateral setae moderately long.
Spermatheca (Fig. 78F, G) with capsule spherical, moderately large to large; apical chamber pyriform to almost pyriform, moderate large; duct extending anteriorly beyond the anterior marginof capsule, long, moderately or tightly coiled, usually thin but the duct from the opening to 1st
turn sometimes moderately thick to thick.
Biology and ecology. S. yokozekii is distributed in the plains and low mountainous regions of
Kinki district, Honshu. The beetles inhabit leaf litter in the natural forests.
Remarks. S. yokozekii is the sister species of S. kishimotoi, and it is separable from the latter
species by the aedeagal median lobe broadest at apicolateral corner (Fig. 78B), the endophallic
expulsion hook weakly pointed posterolaterally (Fig. 78H), and the spermatheca with its duct
extending anteriorly beyond the anterior margin of capsule (Fig. 78F).
Etymology. This species is named in honor of Mr. Hideyuki Yokozeki (Yokkaichi, Mie), whocollected the beetles of this species.
Stenus tateoi Naomi(Figs. 79A–H, 108A)
Stenus tateoi Naomi & Puthz, 2006: 101; Naomi & Puthz, 2013: 141.
Type material examined. Holotype: ♂ (CBM), Nomura, Mie Pref., 23. xi. 1986, A. Amagasu
leg. Paratypes: 3 ♀ (cN), Kirihata, Komono, Mie Pref., 30. iv. 1998, F. Ichikawa leg.; 1 ♂3 ♀
(cN), Geinou-cho, Agei-gun, Mie Pref., 23. xii. 1995, H. Ichikawa & A. Amagasu leg.; 1 ♀ (cN),
Igagoe, Anou-cho, Ayama-gun, Mie Pref., 23. xii. 1995, H. Yokozeki leg.; 1 ♀ (cN), Suwa, Ueno
City, Mie Pref., 2. v. 1997, H. Yokozeki leg.; 4 ♂3 ♀ (cN), Mt. Jubusen, Kyoto, 15. ix. 1989, T.
Ito leg.; 1 ♂ (cN), Mt. Watamuki, Shiga Pref., 5. vi. 1988, N. Ito leg.
Distribution. Japan: Honshu (Shiga, Kyoto and Mie Prefs.).
Redescription. Male and female: Body 3.8–5.0 mm (fore body 1.8–2.3 mm) in length, withantennae moderately long, very thin. Head and abdomen black; pronotum and elytra dark chocolate brown; labrum dark red; antennae and legs yellowish brown to reddish brown. Head weakly
concave, with a pair of broad longitudinal furrows; punctures round, moderately dense to dense,
small. Pronotum with surface weakly uneven to almost even; punctures round to elliptical, very
dense, moderately large, somewhat coarse, sometimes two or more punctures partially fused.
Elytra with surface weakly uneven, almost ﬂat near suture; punctures round, very dense, various
in size. Tarsi each with 4th tarsomere strongly bilobed. Abdomen with punctures round, moderately dense to dense, small in anterior segments, while punctures in posterior segments sparse tomoderately dense, very small, almost regular. Lateroventrites missing; tergo-ventrite sutures verythin or almost missing.
Male: Eighth ventrite (Fig. 79C) posteromedially with a broad, arcuate emargination; 9th tergum with antecostal apophyses relatively short; 9th ventrite (Fig. 78A) minutely serrate posteriorly, with macrosetae moderately long, apicolateral teeth long, acutely pointed, apicolateral setae
relatively short; 10th tergum shallowly emarginate posteriorly. Aedeagal median lobe (Fig. 79B)
broad, rounded or obtusely angulate apicolaterally, obtusely angulate at apex; apical sclerotizedarea (Fig. 79B) rather transverse, almost broad-triangular. Endophallic median bands (Fig. 79B)

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Fig. 79. Stenus tateoi Naomi (A, B, D, G, H, Nomura, Mie; C, Geinou, Mie; E, Kirihata, Mie; F, Ueno, Mie). A,
9th ventrite of male; B, aedeagus; C, posterior part of 8th ventrite of male; D, E, posterior part of gonocoxite;
F, G, spermatheca; H, expulsion hooks. Scale 1: 0.2 mm for A, B, 0.1 mm for D–H; Scale 2: 0.25 mm for C.

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moderately long, thin; lateral bands (Fig. 79B) each broad at base; expulsion hooks (Fig. 79H)
separated, each elongate, nearly boot-shaped, sharply hooked anteriorly, with anterior plate fusedwith posterior plate; copulatory tube (Fig. 79B) slender, with basal chamber having two rods ofdifferent length, main tube long, thin, basically fusiform, very weakly broadened at apex. Parameres (Fig. 79B) each very acutely pointed at apex; apical area long, weakly swollen mesially atbase, strongly narrowed toward apex, furnished basally with 7 to 8 short, thin setae, and apicallywith 1 or 2 moderately long setae.
Female: Eighth ventrite almost rounded posteriorly; gonocoxites (Fig. 79D, E) (sometimes
irregularly) toothed posteriorly, each with macrosetae moderately long, apicolateral tooth long,pointed, apicolateral setae moderately long. Spermatheca (Fig. 79F, G) with capsule spherical,
large; apical chamber pyriform, large to very large; duct with 2 distinct turns, the duct from theopening to 1st turn almost straight.
Biology and ecology. S. tateoi is distributed in the plains and low mountainous regions of
Kinki district, Honshu. The beetles inhabit leaf litter in the natural forests.
Remarks. S. tateoi is allied to S. kishimotoi and S. yokozekii, but it is separable from the lattertwo species by the aedeagal median lobe obtusely angulate at apex (Fig. 79B), the endophallic
expulsion hook sharply hooked anteriorly (Fig. 79H), and the spermatheca with its duct with 2
distinct turns (Fig. 79F).
Etymology. This species is named in honor of Mr. Tateo Ito (Yahata, Kyoto), who studies the
Staphylinidae, and also greatly contributed to our monographic studies of the Japanese Steninae,
by loaning a large number of rare Stenus beetles to us for studies.
Stenus ohishii Naomi(Figs. 80A–H, 108B)
Stenus ohishii Naomi, 1987: 5; Herman, 2001: 2313; Naomi, 2006: 70; Naomi & Puthz, 2013:
141.
Type material. Holotype: ♂ (KUF), Shin-yabakei, Oita Pref., 30. iii. 1985, S. Nomura leg.
Type material examined. Paratypes: 1 ♂ (cN), Mt. Tsurugi, Tokushima Pref., 19–20. vi. 1981,
S. Naomi leg.; 1 ♂ (cN), same locality, 15–17. x. 1980, S. Naomi leg.; 1 ♀ (cN), Ochiai Pass,
Tokushima Pref., 18. vi. 1981, S. Naomi leg.; 1 ♂ (cN), Shin-yabakei, Ohita Pref., 30. iii. 1985,
S. Nomura leg.; 1 ♂1 ♀ (cN), Mt. Hiko, Fukuoka Pref., 4. ix. 1977, H. Ohishi leg.
Other material examined. [HONSHU]: 1 ♂, Koda-Hachiman Shrine, Awaji Is., Hyogo Pref.,16. xi. 1998, S. Nomura leg. [SHIKOKU]: 1 ♂, Mt. Odami, Ehime Pref., 25. ix. 1993, I. Okamoto leg.; 1 ♀, same locality, 21. vii. 1993, M. Sakai leg.; 1 ♂, Sakagawa, Tosayamada-cho,
Kochi Pref., 8. x. 1990, S. Nomura leg.; 1 ♂, Ohira, Mino-cho, Tokushima Pref., 2. xii. 1992, M.
Sakai leg. [KYUSHU]: 1 ♀, Mt. Kurodake, Kujyu, Ohita Pref., 28. v. 1986, S. Nomura leg.; 1 ♂,Buzenbo, Mt. Hiko, Fukuoka Pref., 30. iv. 1983, S. Nomura leg.; 1 ♂, same locality, 13. x. 1992,
S. Nomura leg.; 1 ♀, Kinsenji, Mt. Tara, Nagasaki Pref., 7. v. 1983, S. Imasaka leg.; 1 ♀, Mt.
Ichifusa, Kumamoto Pref., 13. v. 1985, S. Nomura leg.
Distribution. Japan (Honshu: Awaji Is., Shikoku, Kyushu).
Redescription. Male and female: Body 4.2–6.0 mm (fore body 2.0–2.6 mm) in length, withantennae moderately long, very thin. Head black; pronotum, elytra and abdomen dark chocolate
brown; labrum dark red to black; antennae and legs yellowish brown to reddish brown. Headweakly concave, with a pair of broad longitudinal furrows; punctures round to elliptical, moder-190

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Fig. 80. Stenus ohishii Naomi (A–F, Buzenbo, Fukuoka; G, H, Hiko, Fukuoka). A, 9th ventrite of male; B,
aedeagus; C, posterior part of 8th ventrite of male; D, expulsion hooks; E, copulatory tube; F, G, spermatheca;
H, gonocoxite. Scale 1: 0.2 mm for A, B, 0.1 mm for D–H; Scale 2: 0.25 mm for C.

ately dense to very dense, various in size, somewhat coarse. Pronotum with surface weakly
uneven to uneven; punctures round to almost round, very dense, various in size, coarse. Elytra
with surface uneven, ﬂat near suture; punctures round to elliptical, very dense, moderately large

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to large, coarse. Tarsi each with 4th tarsomere strongly bilobed. Abdomen with punctures round,moderately dense, small, almost regular in anterior segments; punctures in anterior parts of posterior segments round, dense, very small, while punctures in posterior parts of posterior segments
round, sparse, very small, almost regular. Lateroventrites and tergoventrite sutures missing.
Male: Seventh ventrite posteromedially with a bell-shaped ﬂat area; 8th ventrrite (Fig. 80C)
posteromedially with a broad, arcuate emargination; 9th tergum with antecostal apophyses relatively short; 9th ventrite (Fig. 80A) minutely serrate posteriorly, with macrosetae moderately
long, apicolateral teeth very long, acutely pointed, apicolateral setae short; 10th tergum almost
entire. Aedeagal median lobe (Fig. 80B) broad, gently rounded apicolaterally, apically with avery minute, pointed median cusp; apical sclerotized area (Fig. 80B) weakly developed, nearlyarched. Endophallic median bands (Fig. 80B) very long, moderately broad; expulsion hooks (Fig.
80B, D) separated, each almost elongate-triangular, broadest at or near the most-posterior part,almost truncate posteriorly, with anterior plate partially demarcated by an oblique suture fromposterior plate; copulatory tube (Fig. 80E) moderately long and thick, with basal chamber welldeveloped with two thick rods, basal constriction distinct (Fig. 80B) or indistinct (Fig. 80E),
main tube double-structured by the inner and outer tubes, with the apically exposed inner tube
weakly curved, minutely emarginate at apex. Parameres (Fig. 80B) each slender, straight, very
acutely pointed apically; apical area relatively short to moderately long, swollen mesially at base,furnished mesially with 10 to 12 thin setae.
Female: Eighth ventrite almost rounded posteriorly; gonocoxites (Fig. 80H) each distinctly
toothed posteriorly, with apicolateral tooth long, sharply pointed, apicolateral setae long. Spermatheca (Fig. 80F, G) with capsule elongate-ovoidal to almost spherical, large to very large; apical chamber almost ovoidal to pyriform, large; duct very short to short with 1 or 2 turns.
Biology and ecology. S. ohishii is widely distributed in the plains and mountainous regions.
The beetles inhabit leaf litter in the natural forests.
Remarks. S. ohishii is the sister species of S. fusciceps, and it is separable from the latter species by the endophallic expulsion hook broadest at or near the most-posterior part (Fig. 80B, D),
the copulatory tube with its exposed inner tube weakly curved (Fig. 80E), and the spermathecawith its duct much shorter, having 1 or 2 turns (Fig. 80F). S. ohishii seems to be also allied to S.
guniujiangensis from east China, but it is separable from the latter species by the aedeagal
median lobe a little broader apically (Fig. 80B), the paramere with its apical area a little narrower(Fig. 80B), and the spermatheca with its capsule larger and its duct thicker (Fig. 80F, G).
No variations are basically found among the local populations of Shikoku and Kyushu in S.
ohishii, but the male of Awaji Is. (Hyogo) seems to show some variations as follows: The aedeagal median lobe is a little more strongly constricted near the middle, with its apical sclerotizedarea a little longer; and the endophallic copulatory tube has a little thicker apical tube.
Etymology. This species is named in honor of Mr. Hisashi Ohishi (Kyoto), who collected theStenus beetles of this species.
Stenus fusciceps Naomi(Figs. 81A–H, 108C)
Stenus fusciceps Naomi, 2006: 72; Naomi & Puthz, 2013: 141.
Type material examined. Holotype: ♂ (CBM), Muroto Cape, Kochi Pref., 4. vi. 1988, T. Itoleg. Paratypes: 2 ♂3 ♀ (cN), same data as holotype.

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Fig. 81. Stenus fusciceps Naomi (Muroto, Kochi). A, 9th ventrite of male; B, aedeagus; C, posterior part of 8th
ventrite of male; D, gonocoxite; E, F, spermatheca; G, expulsion hooks; H, copulatory tube. Scale 1: 0.2 mm
for A, B, 0.1 mm for D–H; Scale 2: 0.25 mm for C.

Distribution. Japan: Shikoku (Kochi Pref.).
Redescription. Male and female: Body 4.6–6.0 mm (fore body 2.2–2.5 mm) in length, withantennae moderately long, very thin. Head black; pronotum, elytra and abdomen dark chocolate
brown; labrum dark red; antennae and legs yellowish brown to reddish brown. Head weakly concave, with a pair of broad longitudinal furrows; punctures round to almost round, moderately

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dense to dense, small. Pronotum with surface weakly uneven; punctures round to almost round,very dense, various in size, somewhat coarse. Elytra with surface weakly uneven, ﬂat nearsuture; punctures round to almost round, very dense, moderately large to large, somewhat coarse.
Tarsi each with 4th tarsomere strongly bilobed. Abdomen with punctures round to almost round,moderately dense, small to moderately large in anterior segments, while punctures in posterior
segments sparse to moderately dense, very small, almost regular. Lateroventrites and tergoventrite sutures missing.
Male: Eighth ventrrite (Fig. 81C) posteromedially with a broad, arcuate emargination; 9th
tergum with antecostal apophyses relatively short; 9th ventrite (Fig. 81A) minutely serrate posteriorly, with macrosetae relatively short, apicolateral teeth very long, acutely pointed, apicolateral
setae moderately long to long; 10th tergum almost entire. Aedeagal median lobe (Fig. 81B) relatively broad, gently rounded apicolaterally, apically with a very minute, pointed median cusp;
apical sclerotized area (Fig. 81B) nearly arched, arcuately emarginate anteriorly. Endophallic
median bands (Fig. 81B) long, relatively narrow; expulsion hooks (Fig. 81G) separated, eachnearly elongate-subtriangular, broadest at the mesial corner of posterior plate, with anterior plate
demarcated by a suture from posterior plate; copulatory tube (Fig. 81B, H) relatively short, withbasal chamber well-developed, about as long as main tube, the main tube double-structured by
the inner and outer tubes, with the apically exposed inner tube straight, minutely emarginate atapex. Parameres (Fig. 81B) each slender, straight, very acutely pointed at apex; apical area moderately long, swollen mesially at base, furnished mesially with 10 to 12 thin setae.
Female: Eighth ventrite almost rounded posteriorly; gonocoxites (Fig. 81D) toothed posteriorly, each with apicolateral tooth very long, sharply pointed, apicolateral setae very long. Spermatheca (Fig. 81E, F) with capsule ovoidal, large to very large; apical chamber ovoidal to pyriform, large to very large; duct moderately long, thin, loosely coiled, with more than 6 turns.
Biology and ecology. S. fusciceps is presently distributed only in the plains of southeasternpart of Shikoku. The beetles inhabit leaf litter in the natural forests.
Remarks. S. fusciceps is the sister species of S. ohishii, and it is separable from the latter species by the endophallic expulsion hook broadest at the mesial corner of posterior plate (Fig.
81B), the copulatory tube with its exposed inner tube straight (Fig. 81H), and the spermathecawith its duct much longer, having more than 6 turns (Fig. 81E).
Stenus indubius Sharp(Figs. 82A–H, 108D)
Stenus indubius Sharp, 1889: 330; Herman, 2001: 2231; Naomi, 2006: 64.
Stenus vernalis Naomi, 1997: 750; Herman, 2001: 2430; Puthz, 2001: 36 (synonym of S. indubius).
Type material examined. Lectotype of S. indubius: ♂ (NHML), Japan, Lewis, Sharp coll.
1905–313 [examined by Puthz, 1994]. Paralectotype of S. indubius: 1 ♀ (FMC), Japan. G.
Lewis. 1910–320 / Chicago Nat. Hist. Mus. [examined by Puthz, 1994].
Holotype of S. vernalis: ♂ (CBM), Shimogamo, Minamiizu-cho, Shizuoka Pref., 15. iii.
1996, S. Naomi leg. Paratypes: 1 ♂2 ♀ (cN), same data as holotype.
Other material examined. [HONSHU]: 2 ♂, Kintoki, Hakone, Kanagawa Pref., 23. ix. 1992,
Y. Hirano leg.; 1 ♂, Near Ohkura, Tanzawa, Kanagawa Pref., 2, v. 1971, Y. Shibata leg.; 1 ♀, Mt.
Daisen, Tanzawa, Isehara City, Kanagawa Pref., 6. v. 2000, S. Naomi leg.; 1 ♂1 ♀, same locality,

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Fig. 82. Stenus indubius Sharp (A–D, F–H, Tanzawa, Kanagawa; E, Shimogamo, Shizuoka). A, 9th ventrite ofmale; B, aedeagus; C, posterior part of 8th ventrite of male; D, expulsion hooks; E, F, spermatheca; G, posterior part of gonocoxite; H, head. Scale 1: 0.2 mm for A, B, 0.1 mm for D–G; Scale 2: 0.25 mm for C; Scale 3:
0.3 mm for H.

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25. iv. 2001, S. Arai leg.; 1 ♀, Tanzawa, Kanagawa Pref., 21. iv. 1985, K. Haga leg.; 1 ♀, Sanpoku-machi, Kanagawa Pref., 2. vii. 1993, K. Haga leg.; 1 ♂, Udosan, Shimizu, Shizuoka Pref.,12. x. 1999, Y. Hirano leg.; 2 ♂1 ♀, Bunzawa (600 m), Nakakawane-cho, Shizuoka Pref., 3. v.
2001, S. Arai leg.
Distribution. Japan: Honshu (Kanagawa and Shizuoka Prefs.). Among the old specimens of
the Japanese Stenus species identiﬁed as S. indubius in the late 19th and early 20th centuries,
there are found the Stenus beetles collected not only from Chubu district but also from Kinki or
Chugoku districts (e.g., Puthz, 2001; Naomi, 2006). The old records of this species from thewestern part of Honshu may be, however, based on the misidentiﬁcation of species (e.g., Puthz,
2001: 36). In fact, the true S. indubius beetles are collected only from Chubu district in our days(about last 5 decades). Given this, the available information shows that the true distributional
range of S. indubius seems to be restricted to the southern part of Chubu district, central Honshu.
Redescription. Male and female: Body 4.3–5.5 mm (fore body 2.3–2.6 mm) in length, withantennae moderately long, very thin. Head and abdomen black; pronotum and elytra dark chocolate brown to black; labrum dark red to black; antennae and legs yellowish brown to reddish
brown. Head (Fig. 82H) weakly concave, with a pair of broad longitudinal furrows; puncturesround to almost round, moderately dense to dense, small to moderately large, somewhat umbilicate. Pronotum with surface weakly uneven to almost even: punctures round to almost round,very dense, various in size. Elytra with surface weakly uneven to uneven, ﬂat near suture; punctures round to almost round, very dense, moderately large to large, sometimes coarse. Tarsi eachwith 4th tarsomere strongly bilobed. Abdomen with punctures round, moderately dense to dense,
small to moderately large in anterior segments, while punctures in posterior segments sparse tomoderately dense, very small, shallow. Lateroventrites and tergoventrite sutures missing.
Male: Seventh ventrite posteromedially with a bell-shaped ﬂat area, which is very shallowly
emarginate; 8th ventrite (Fig. 82C) posteromedially with an arcuate, moderately deep emargination; 9th tergum with antecostal apophyses moderately long; 9th ventrite (Fig. 82A) minutely
serrate posteriorly, with macrosetae short, apicolateral teeth long, pointed, apicolateral setae short
to moderately long; 10th tergum almost rounded posteriorly. Aedeagal median lobe (Fig. 82B)
broad, gently rounded apicolaterally, almost simply pointed at apex; apical sclerotized area (Fig.
82B) broad-subtriangular, weakly rounded anteriorly. Endophallic median bands (Fig. 82B)
short, relatively broad; expulsion hooks (Fig. 82B, D) separated, each nearly elongate-triangular,
weakly projecting and pointed posterolaterally, with anterior plate almost demarcated by anoblique suture from posterior plate; copulatory tube (Fig. 82B) with basal tube membranous,
main tube almost elongate-S-shaped, thin to very thin, with a subtransparent, broad, lateral ﬂap
along the right side. Parameres (Fig. 82B) each very acutely pointed at apex; apical area long,
weakly swollen around the base, furnished basally with 5 to 7 short, thin setae, apically with 2 or
3 long setae.
Female: Eighth ventrite almost rounded posteriorly; gonocoxites (Fig. 82G) distinctly
toothed posteriorly, each with apicomesial tooth long, acutely pointed, apicolateral tooth very
long, acutely pointed, apicolateral setae long. Spermatheca (Fig. 82E, F) with capsule ovoidal toelliptical, large; apical chamber pyriform, large; duct moderately long to very long, moderately
thick, moderately or strongly coiled.
Biology and ecology. S. indubius is distributed in the plains and mountainous regions of thesoutheastern part of Chubu district, central Honshu. The beetles inhabit leaf litter in the naturalforests.
Remarks. S. indubius is the sister species of S. kiyosumiensis, and it is separable from the lat-

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ter species by the aedeagal median lobe with its apical sclerotized area broader (Fig. 82B), theendophallic copulatory tube almost elongate-S-shaped (Fig. 82B), and the spermatheca with its
duct simply moderately or strongly coiled, without any abrupt bends on its way (Fig. 82E, F).
Stenus kiyosumiensis Naomi & Takeda(Figs. 83A–F, 108E)
Stenus kiyosumiensis Naomi & Takeda, 1991: 10; Herman, 2001: 2247; Naomi, 2006: 67; Naomi& Puthz, 2013: 141.
Type material examined. Holotype: 1 ♂ (CBM), Fudago, Kimitsu City, Chiba Pref., 20. iv.
1989, S. Naomi leg.
Other material examined. [HONSHU]: 1 ♂, Mt. Tadeshina, Nagano Pref., 1. vii. 201, I.
Matoba leg.; 1 ♀, Tobira Spa, Nagano Pref., 13. ix. 1995, T. Ito leg.; 1 ♂, Daibosatu, Yamanashi
Pref., 6. vii. 1988, T. Ito leg.; 1 ♂, Yanagisawa Pass, Enzan City, Yamanashi Pref., 17. xi. 1999,
S. Nomura leg.; 1 ♂, Mitumine, Ohtaki Vil., Saitama Pref., 28. v. 1997, S. Naomi leg.; 1 ♀,Kiyotaki, Mt. Ryogami, Saitama Pref., 10. v. 1997, T. Kishimoto leg.; 2 ♀, Same locality, 10. v.
1997, M. Maruyama leg.; 1 ♂, Mizunezawa, Okutama, Tokyo, 6. v. 1980, T. Kishimoto leg.; 1 ♀,Hikagezawa, Mt. Takao, Tokyo, 20. iv. 1997, S. Nomura leg.; 1 ♂1 ♀, Mt. Mitake, Tokyo, 1. v.
1991, T. Ito leg.; 1 ♂, Minamiasai, Chikura-machi, Chiba Pref., 31. iii. 1996, S. Naomi leg.; 1 ♀,Mt. Takago, Kimitsu City., Chiba Pref., 7. ii. 1999, S. Arai et al. leg.; 1 ♂1 ♀, same locality, 25.
x. 1998, S. Naomi leg.
Distribution. Japan: Honshu (Chubu and Kanto districts).
Redescription. Male and female: Body 3.8–5.8 mm (fore body 2.0–2.6 mm) in length, withantennae moderately long, very thin. Head and abdomen black; pronotum and elytra dark chocolate brown; labrum dark red to black; antennae and legs yellowish brown to reddish brown. Headweakly concave, with a pair of broad longitudinal furrows; punctures round, moderately dense tovery dense, small, umbilicate. Pronotum with surface weakly uneven; punctures round, very
dense, moderately large, almost regular, sometimes two punctures partially fused. Elytra withsurface weakly uneven, ﬂat near suture; punctures round, very dense, moderately large, regular.
Tarsi each with 4th tarsomere strongly bilobed. Abdomen with punctures round, moderately
dense, small, almost regular in anterior segments, while punctures in posterior segments moderately dense, very small, regular. Lateroventrites and tergoventrite sutures missing.
Male: Seventh ventrite posteromedially with a bell-shaped ﬂat area; 8th ventrite (Fig. 83C)
posteriorly with a shallow, arcuate emargination; 9th tergum with antecostal apophyses moderately long; 9th ventrite (Fig. 83A) irregularly serrate and moderately deeply emarginate posteriorly, with macrosetae moderately long, apicolateral teeth stout, long, acutely pointed, apicolateral
setae moderately long; 10th tergum almost rounded posteriorly. Aedeagal median lobe (Fig. 83B)
broad, gently rounded apicolaterally, almost rounded or obtusely angulate at apex; apical sclerotized area (Fig. 83B) narrow, subtriangular, weakly rounded anteriorly. Endophallic medianbands (Fig. 83B) short, relatively broad; expulsion hooks (Fig. 83B) separated, each elongatesubtriangular, with anterior plate almost demarcated by an oblique ridge from posterior plate, theposterior plate distinctly projecting and pointed posterolaterally; copulatory tube (Fig. 83B) withbasal chamber membranous, main tube long, thin, bisinuous. Parameres (Fig. 83B) each very
acutely pointed at apex; apical area long, moderately swollen around the base, furnished basallywith 13 to 15 thin, short setae, apically with 2 or 3 moderately long setae.

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Fig. 83. Stenus kiyosumiensis Naomi & Takeda (A–C, Chikura, Chiba; D, E, Takago, Chiba; F, Mitake, Tokyo).
A, 9th ventrite of male; B, aedeagus; C, posterior part of 8th ventrite of male; D, gonocoxite; E, F, spermatheca. Scale 1: 0.2 mm for A, B, 0.1 mm for D–F; Scale 2: 0.25 mm for C.

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Female: Eighth ventrite almost rounded posteriorly; gonocoxites (Fig. 83D) distinctly
toothed posteriorly, each with apicomesial tooth long, acutely pointed, apicolateral tooth very
long, acutely pointed, apicolateral setae moderately long to long. Spermatheca (Fig. 83E, F) with
capsule ovoidal to elliptical, large to very large; apical chamber pyriform, moderately large; duct
moderately long, moderately thick to thick, usually moderately coiled but partially with abrupt
bends on its way; gland with its opening located on the posterior side of duct a little proximal
from the base of apical chamber.
Biology and ecology. S. kiyosumiensis is distributed in the plains and mountainous regions of
Chubu and Kanto districts, central Honshu. The beetles inhabit leaf litter in the natural forests.
Remarks. S. kiyosumiensis is the sister species of S. indubius, and it is separable from the latter species by the aedeagal median lobe with its apical sclerotized area narrower (Fig. 83B), theendophallic copulatory tube only weakly bisinuous (Fig. 83B), and the spermatheca with its duct
coiled, partially with abrupt bends on its way (Fig. 83E).
Species-group of S. ﬂammeus Tang & Puthz
The ﬂammeus-group is a small East Asian species-group of Stenus, which was ﬁrst recognized as a “species-complex” within the cirrus-group by Tang et al. (2008); and the species-complex was established as a separate species-group of Stenus by Tang et al. (2016). At present, theﬂammeus-group comprises 17 species; and their species are distributed only in China (Sichuan;
Shaanxi) and Japan (Nansei Isls.). This species-group is well-characterized by an apomorphic
combination of the conical or subconical paraglossae and the abdomen with its surface highly
glittering and sparsely covered with suberect setae (Tang et al. 2016).
The sharpi-group, ﬂammeus-group (Fig. 108F–H) and cirrus-group (Fig. 109A–L) are certainly similar to one another in their habitus. Furthermore, these groups have some morphological similarities as follows: The sharpi-group and ﬂammeus-group share an apomorphic conical or
subconical (Fig. 86J) condition of paraglossae, while the ﬂammeus-group and cirrus-group share
an apomorphic condition of abdomen (the surface sparsely covered with suberect setae).
Although the distribution of these apomorphic characters is incongruent among the 3 groups, it
seems certainly to show that these groups are closely related phylogenetically to one another. The
ﬂammeus-group is separable from the sharpi-group and cirrus-group by the combination of the 2
apomorphic characters mentioned above.
Diagnostic characters of the ﬂammeus-group: Body medium to large in size, cylindrical,
elongate, strongly glittering especially on the abdomen (Fig. 108F–H); antennae relatively short
to moderately long; paraglossa conical or subconical (Fig. 86I, J); tarsus with 4th tarsomere
strongly bilobed; abdomen with surface sparsely covered with suberect setae (Fig. 108F); tergoventrite sutures missing or scarcely existing only at the anterior parts of 4th and 5th segments.
Male: Ninth ventrite with apicolateral tooth usually long (Tang et al. 2016, ﬁg. 14) but sometimes very short (Fig. 84B) to short, acutely pointed, and with the median projection at the posterior margin (Fig. 86E). Female: Gonocoxite with apicolateral tooth (Fig. 84D); spermathecal duct
membranous or weakly sclerotized (Fig. 84H).
In the Japanese species of the ﬂammeus-group, there exist a single median sclerite or paired
sclerites as endophallic component(s); and these sclerite(s) are in situ located near the apex of
copulatory tube (Figs 85H, 86A), or at the lateral sides of the apex of copulatory tube (Fig. 84C).
When it exists as a single plate (Fig. 86A) or a rod (Fig. 85H), it is similar to the apicolateral plateof the pallitarsis-group (Naomi et al., 2017, ﬁg. 88A) in that it has a thin, longitudinal slit which

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is open posteriorly. When they otherwise exist as paired plates (Fig. 84C), it is similar in structure
to the apicolateral plates of the bispinus-group (Naomi et al., 2017, e.g., ﬁg. 113C). Thus, we heretentatively identify these endophallic sclerites as “apicolateral plate(s)” (Naomi et al., 2017, p.
17). Further studies are needed for the precise homologization of these endophallic sclerites.
A list of the species of S. ﬂammeus-groupdabashanus Tang, Liu & Niu, 2016 Distribution: China (Shaanxi)
ﬂammeus Tang & Puthz, 2008 Distribution: China (Sichuan)
bostrychus Tang & Puthz, 2008 Distribution: China (Sichuan)
corniculus Tang, Liu & Niu, 2016 Distribution: China (Sichuan)daicongchaoi Tang, Liu & Niu, 2016 Distribution: China (Sichuan)jiajinshanus Tang, Liu & Niu, 2016 Distribution: China (Sichuan)jindingianus Tang, Liu & Niu, 2016 Distribution: China (Sichuan)
paraﬂammeus Tang, Liu & Niu, 2016 Distribution: China (Sichuan)
pengzhongi Tang, Liu & Niu, 2016 Distribution: China (Sichuan)
pseudoﬂammeus Tang, Liu & Niu, 2016 Distribution: China (Sichuan)punctidorsus Tang, Liu & Niu, 2016 Distribution: China (Sichuan)tuyueyei Tang, Liu & Niu, 2016 Distribution: China (Sichuan)
xilingmontis Tang, Liu & Niu, 2016 Distribution: China (Sichuan)
zhoudeyaoi Tang, Liu & Niu, 2016 Distribution: China (Sichuan)punctifer Naomi, 1988b Distribution: Japan (Kyushu: Okinawa Is.)= jambar Naomi, 1990b
tokunis Naomi, 1998a Distribution: Japan (Kyushu: Toku Is.)amamiensis Naomi, 1988b Distribution: Japan (Kyushu: Amami Is.)
Japanese fauna of the ﬂammeus-group
The ﬂammeus-group consists of 3 species in Japan. All of these species are indigenous toNansei Islands in Japan.
Key to the Japanese species of S. ﬂammeus group
1(2)

2(1)

3(4)

4(3)

Male & female: Elytra with punctures smaller. Male: Eighth ventrite with a larger, semicircular emargination (Fig. 84G); 9th tergum with antecostal apophysis shorter (Fig.
84A); endophallic expulsion hook with posterior plate acutely pointed (or very minutely
bi-pointed) posteriorly (Fig. 84F) ...........................................................S. punctifer Naomi
Male & female: Elytra with punctures larger. Male: Eighth ventrite with a smaller, triangular emargination; 9th tergum with antecostal apophysis longer; endophallic expulsion
hook with posterior plate angulate posteriorly.
Male: Aedeagal median lobe more strongly pointed at apex (Fig. 85H); endophallic copulatory tube with main tube thinner, broadest near the middle, then attenuate apically (Fig.
85E). Female: Spermathecal duct longer, with 6 turns (Fig. 85D) ............S. tokunis Naomi
Male: Aedeagal median lobe less strongly pointed at apex (Fig. 86A); endophallic copulatory tube with main tube thicker, broadest a little before the apex (Fig. 86B). Female:
Spermathecal duct shorter, with 4 turns (Fig. 86D) ........................... S. amamiensis Naomi

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Stenus punctifer Naomi(Figs. 84A–H, 108F)
Stenus punctifer Naomi, 1988b: 35; Herman, 2001: 2361; Naomi & Puthz, 2013: 141.
Stenus jambar Naomi, 1990b: 52.
Type material. Holotype of S. punctifer: ♂ (KUF), Yona, Okinawa Is., Okinawa Pref., 15. iii.
1985, S. Nomura leg.
Holotype of S. jambar: ♀ (KUF), Ie Mountain-road, Kunigami, Okinawa Is., Okinawa Pref.,14. iii. 1985, S. Nomura leg.
Type material examined. Paratypes of S. punctifer: 1 ♂ (cN), Mt. Nago, Okinawa Is., Okinawa Pref., 11. iii. 1985, S. Nomura leg.; 1 ♀ (cN), Yona, Okinawa Is., Okinawa Pref., 15. iii.
1985, S. Nomura leg.; 1 ♀ (cN), Ie mountain-road, Kunigami, Okinawa Is., Okinawa Pref., 22.
iv. 1986, S. Nomura leg.
Other material examined. [KYUSHU]: 1 ♀ (cN), Mt. Nishime, Okinawa Is., Okinawa Pref.,12. ii. 1991, K. Ogata leg.; 1 ♀ (cN), Ie Mountain-road, Kunigami, Okinawa Is., Okinawa Pref.,11. x. 1988, S. Nomura leg.; 1 ♀ (cN), same data as above, 14. iii. 1991, S. Nomura leg.
Distribution. Japan: Kyushu (Okinawa Is.).
Redescription. Male and female: Body 4.3–4.5 mm (fore body 2.0–2.1 mm) in length, slender, strongly shining to glittering, with antennae moderately long, very thin. Body black withdark red tinge; labrum dark red; antennae and legs yellowish brown to dark yellowish brown.
Head shallowly or moderately concave, with a pair of longitudinal furrows; punctures round,
dense, moderately large to large, setiferous. Pronotum with surface slightly uneven, without
median longitudinal furrow; punctures round, very dense, moderately large. Elytra with surface
almost even; punctures round to elliptical, very dense, various in size (small to moderately large
or large). Tarsi each with 4th tarsomere strongly bilobed. Abdomen with anterior segments covered sparsely with thin, suberect long setae, posterior segments (Fig. 84A) sparsely with thin,suberect, very long setae; punctures round, very sparse to sparse, very small to small, irregular.
Lateroventrites missing; tergoventrite sutures almost missing but scarcely existing only at theanterior parts of 4th and 5th segments.
Male: Seventh ventrite posteromedially with an elongate-bell-shaped depression or ﬂat area;
8th ventrite (Fig. 84G) posteromedially with a semicircular emargination; 9th tergum (Fig. 84A)
with antecostal apophyses moderately long, thin; 9th ventrite (Fig. 84B) rounded at posteromedian part, with apicolateral tooth very short, pointed, turning posteromesially, apicolateral setae
long; 10th tergum (Fig. 84A) subtrapezoidal, shallowly emarginate posteriorly. Aedeagal median
lobe (Fig. 84C) elongate, gently rounded at apicolateral corners, apically with a small, pointed
median cusp; apical sclerotized area (Fig. 84C) subtriangular, shallowly emarginate at anteromedian part. Endophallic apicolateral plates (Fig. 84C) paired, sclerotized, large, located anterior to
the expulsion hooks; median bands (Fig. 84C) with basal bands long, relatively thin; lateralbands (Fig. 84C) moderately long; explusion hooks (Fig. 84F) separated, each with anterior plate
acutely pointed or very minutely bifurcate at anterior apex, partially demarcated by a suture fromposterior plate, the posterior plate posterolaterally with the longitudinal folded rim, which turns
ventrally; copulatory tube (Fig. 84E) distinctly bent at the basal constriction, with basal chamber
long, large, narrowed apically, main tube baculiform, straight, attenuate. Parameres (Fig. 84C)
thin; apical area short, hardly swollen mesially, furnished mesially with 8 to 9 short setae.
Female: Seventh ventrite posteromedially with a very shallow emargination; 8th ventrite

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Fig. 84. Stenus punctifer Naomi (A–C, E–G, Nagodake, Okinawa Is.; D, H, Ie, Okinawa Is.). A, 9th and 10th
terga of male; B, 9th ventrite of male; C, aedeagus; D, posterior part of gonocoxite; E, copulatory tube; F,
expulsion hooks; G, posterior part of 8th ventrite of male; H, spermatheca and bursa copulatorix. Scale 1:
0.2 mm for A–C, G, 0.1 mm for D–F, H.

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rounded posteriorly; gonocoxites (Fig. 84D) each posteriorly with several small, irregular, thinteeth, and with apicolateral tooth short, pointed, apicolateral setae long. Spermatheca (Fig. 84H)
with capsule rounded at apex; RT-duct short, thick; duct moderately thick, short with 2 turns;
basal valve short; basal pouch large, bowl-shaped, membranous. Bursa copulatrix (Fig. 84H)
well-sclerotized, broad-subconical.
Biology and Ecology. S. punctifer is distributed in the mountainous regions of Okinawa Is.
The beetles inhabit leaf litter heaped in the natural forests.
Remarks. S. punctifer is allied to S. tokunis and S. amamiensis, but it is separable from thelatter two species by the elytra with punctures smaller, the 8th ventrite of male posteromediallywith a larger, semicircular emargination (Fig. 84G), the endophallic expulsion hook with its posterior plate having a longitudinal folded rim (Fig. 84F), and the spermathecal duct shorter, with 2
turns (Fig. 84H).
Stenus tokunis Naomi(Fig. 85A–H, 108G)
Stenus tokunis Naomi, 1998a: 389; Herman, 2001: 2418; Naomi & Puthz, 2013: 141.
Type material examined. Holotype: ♂ (CBM), Yonama, Toku Is., Kagoshima Pref., 4. v.
1988, S. Nomura leg. Paratypes: 2 ♂1 ♀ (cN), same data as holotypes; 1 ♀ (cN), Mt. Inutabu,
Toku Is., Kagoshima Pref., 3. v. 1988, S. Nomura leg.; 1 ♀ (cN), Tete, Toku Is., Kagoshima Pref.,3. 4. 1988, S. Nomura leg.
Distribution. Japan: Kyushu (Toku Is.).
Redescription. Male and female: Body 4.3–4.5 mm (fore body 1.9–2.0 mm) in length, slender, well-cylindrical, strongly shining to glittering, with antennae moderately long, very thin.
Body black, but pronotum, elytra and abdomen slightly having a dark red tinge; labrum dark red;antennae and legs yellowish brown to dark yellowish brown. Head shallowly concave, with apair of relatively deep, distinct longitudinal furrows; punctures round, sparse to moderately
dense, moderately large. Pronotum with surface almost even to slightly uneven, without medianlongitudinal furrow; punctures round, very dense, small to moderately large. Elytra with surface
almost even, ﬂat along suture; punctures almost round to round, very dense, moderately large tolarge. Tarsi each with 4th tarsomere strongly bilobed. Abdomen with anterior segments covered
very sparsely with thin, suberect long setae, posterior segments sparsely with thin, very longsetae; punctures round, very sparse to sparse, small, irregular. Lateroventrites and tergoventrite
sutures missing.
Male: Sixth ventrite (Fig. 85B) posteromedially with a small, bell-shaped ﬂat area, which isvery shallowly emarginate; 7th ventrite (Fig. 85B) anteromedially with a small, bell-shaped,
shallow depression, posteromedially with an elongate-bell-shaped, shallow depression, which isshallowly emarginate; 8th ventrite (Fig. 85B) posteromedially with a triangular emargination; 9th
tergum (Fig. 85A) with antecostal apophyses long, thin; 9th ventrite (Fig. 85C) posteromediallywith a pointed, small projection, apicolateral tooth short, pointed, apicolateral setae very long;
10th tergum (Fig. 85C) subtrapezoidal. Aedeagal median lobe (Fig. 85H) elongate-ovoidal, angulate at apicolateral corners, very acutely pointed apically; apical sclerotized area (Fig. 85H) narrow, arcuately emarginate anteriorly, strongly narrowed apically behind the apicolateral corners.
Endophallic apicolateral plates (Fig. 85H) baculiform, sclerotized, located posterior to the copulatory tube; median bands (Fig. 85H) with basal bands very long, divergent anteriorly; lateral

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Fig. 85. Stenus tokunis Naomi (Yonama, Toku Is.). A, 9th and 10th terga of male; B, 6th to 8th ventrites of male;C, 9th ventrite of male; D, spermatheca and bursa copulatorix; E, copulatory tube; F, posterior part of gonocoxite; G, expulsion hooks with anterior parts of lateral bands; H, aedeagus. Scale 1: 0.2 mm for A, C, H,
0.1 mm for D–G; Scale 2: 0.3 mm for B.

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bands (Fig. 85H,G) long, thin; explusion hooks (Fig. 85G) separated, each with anterior plate
demarcated by a suture from posterior plate, the posterior plate rounded posteriorly; copulatory
tube (Fig. 85E) with basal chamber almost spherical, main tube asymmetrical, broadest near the
middle, then attenuate apically. Parameres (Fig. 85H) thin; apical area short, weakly swollen
mesially, furnished mesially with 15 to 17 thin, moderately long setae.
Female: Eighth ventrite obtusely angulate posteriorly; gonocoxites (Fig. 85F) irregularly
toothed posteriorly, each with apicolateral tooth short, weakly incurved, pointed, apicolateral
teeth very long. Spermatheca (Fig. 85D) with capsule very small or hardly developed; RT-ductmoderately long, thick; duct thin to moderately thick, moderately long with 6 turns; basal valve
short; basal sclerorized duct short; basal pouch subconical, membranous. Bursa copulatrix (Fig.
85D) well-sclerotized, bowl-shaped, with a deep emargination at base.
Biology and Ecology. S. tokunis is distributed in the plains and mountainous regions of Toku
Is. The beetles inhabit leaf litter heaped in the natural forests.
Remarks. S. tokunis is allied to S. amamiensis, but it is separable from the latter species by
the aedeagal median lobe more strongly pointed at apex (Fig. 85H), the endophallic copulatory
tube with its main tube thinner, asymmetrical, broadest near the middle (Fig. 85E), the apicolateral plate baculiform (Fig. 85H), and the spermathecal duct longer, with 6 turns (Fig. 85D).
Stenus amamiensis Naomi(Figs. 86A–J, 108H)
Stenus amamiensis Naomi, 1988b: 36; Herman, 2001: 2053; Naomi & Puthz, 2013: 141.
Type material. Holotype: ♂ (KUF), Hatsuno, Amami Is., Kagoshima Pref., 27. iii. 1978, S.
Naomi leg.
Type material examined. Paratypes: 2 ♂2 ♀ (cN), same data as holotype.
Other material examined. [KYUSHU]: 1 ♂, Mt. Yui, Amami Is., Kagoshima Pref., 4. v.
1987, S. Nomura leg.; 1 ♀, Asato Pass, Naze City, Amami Is., Kagoshima Pref., 7. iv. 1991, T.
Ueno leg.; 1 ♂, Materia Fall, Yamato Vil., Amami Is., Kagoshima Pref., 19. iii. 1999, T. Ito & A.
Ohkawa leg.
Distribution. Japan: Kyushu (Amami Is.).
Redescription. Male and female: Body 4.0–4.3 mm (fore body 1.6–1.7 mm) in length, slender, well-cylindrical, strongly shining to glittering, with antennae relatively short, very thin.
Body black, but pronotum and elytra slightly having a dark red tinge; labrum dark red; antennae
and legs yellowish brown to dark yellowish brown. Head shallowly concave, with a pair of relatively deep, midlateral longitudinal furrows; punctures round, sparse to moderately dense, moderately large. Pronotum with surface almost even to slightly uneven, with or without median longitudinal furrow; punctures round, very dense, small to moderately large, somewhat umbilicate.
Elytra with surface almost even; punctures round to elliptical, very dense, large to very large.
Tarsi each with 4th tarsomere strongly bilobed, each lobe relatively thick. Abdomen with anterior
segments covered sparsely with thin, suberect long setae, posterior segments (Fig. 86C) sparselywith thin, very long setae; punctures round, very sparse to sparse, small to moderately large,
irregular. Lateroventrites missing; tergoventrite sutures almost missing but scarcely existing at
the anterior parts of 4th and 5th segments.
Male: Seventh ventrite (Fig. 86F) posteromedially with an elongate-bell-shaped depression(Fig. 86F) or ﬂat area, which is very shallowly emarginate; 8th ventrite (Fig. 86F) posteromedi-

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Fig. 86. Stenus amamiensis Naomi (A, Yui, Amami Is.; B, C, E–G, I, J, Hatsuno, Amami Is.; D, H, Akabo,
Amami Is.). A, aedeagus; B, copulatory tube; C, 9th and 10th terga of male; D, spermatheca and bursa copulatorix; E, 9th ventrite of male; F, 7th and 8th ventrites of male; G, expulsion hooks; H, posterior part of gonocoxite; I, paraglossae. Scale 1: 0.2 mm for A, E, 0.1 mm for B, G, H; Scale 2: 0.2 mm for C, 0.1 mm for D;
Scale 3: 0.3 mm for F.

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ally with a triangular emargination; 9th tergum (Fig. 86C) with antecostal apophyses moderately
long, thin; 9th ventrite (Fig. 86E) posteromedially with a short, subtriangular projection, macrosetae moderately long, apicolateral tooth very short, pointed, turning posteromesially, apicolateral setae long; 10th tergum (Fig. 86C) subtrapezoidal, shallowly emarginate posteriorly. Aedeagal median lobe (Fig. 86A) almost fusiform, hardly forming apicolateral corners, apically with asmall, pointed median cusp; apical sclerotized area (Fig. 86A) subtriangular, arcuate at anterior
margin. Endophallic dorsal membrane (Fig. 86G) sclerotized, covered with very small tubercles;
apicolateral plates (Fig. 86C) ovoidal, sclerotized, located near the apex of copulatory tube;
median bands (Fig. 86A) with basal bands long, broad, divergent anteriorly; lateral bands (Fig.
86A) relatively short, each narrowed anteriorly; explusion hooks (Fig. 86G) contiguous at theposteromesial parts of posterior plates, each with anterior plate demarcated by a suture from posterior plate, the posterior plate rounded posteriorly; copulatory tube (Fig. 86B) very large, withbasal chamber subovoidal, main tube very thick, broadest at about apical 1/3, rounded apically.
Parameres (Fig. 86A) thin; apical area relatively short to moderately long, weakly swollen mesially, furnished mesially with 15 to 16 short setae.
Female: Eighth ventrite rounded posteriorly; gonocoxites (Fig. 86H) toothed posteriorly,
each with apicolateral tooth short, weakly incurved, acutely pointed, apicolateral teeth long tovery long. Spermatheca (Fig. 86D) with capsule rounded at apex; RT-duct short, thick; duct moderately thick to thick, relatively short with 4 turns; basal valve short; basal sclerorized duct short;basal pouch funnel-shaped, membranous. Bursa copulatrix (Fig. 86D) well-sclerotized, subconical, with a deep, subtriangular emargination at base.
Biology and Ecology. S. amamiensis is distributed in the mountainous regions of Amami Is.
The beetles inhabit leaf litter heaped in the natural forests and also near the mountain streams.
Remarks. S. amamiensis is allied to S. tokunis, but it is separable from the latter species by
the aedeagal median lobe less strongly pointed at apex (Fig. 86A), the endophallic copulatory
tube with its main tube thicker, symmetrical, broadest at about apical 1/3 (Fig. 86B), the apicolateral plate subovoidal (Fig. 86A), and the spermathecal duct shorter, with 4 turns (Fig. 86D).
Species-group of S. cirrus Benick
The cirrus-group is an Asian species-group of Stenus, which was ﬁrst characterized by Puthz(2003a), and then revised by Tang et al. (2008). At present, it comprises 89 species; and their
species are distributed in India, Vietnam, China, Taiwan and Japan. This species-group is wellcharacterized by a combination of the subovoidal paraglossa (Fig. 96G), the tarsus with its 4thtarsomere simple or weakly bilobed, and the abdomen with the surface highly glittering andsparsely covered with suberect setae (Puthz, 2003a). The cirrus-group is closely allied to theﬂammeus-group (and also sharpi-group), but it is separable from the latter groups by the subovoidal paraglossae (Fig. 96G), the tarsus with its 4th tarsomere simple or weakly bilobed, the9th ventrite of male almost hardly serrate posteriorly (Fig. 87C), and the spermathecal duct
strongly sclerotized and also well-pigmented (Figs. 87F, 93B).
Diagnostic characters of the cirrus-group: Body small to medium or large in size, elongate, strongly glittering (Fig. 109A–L); antennae short to relatively short (but sometimes moderately long); paraglossa subovoidal (Fig. 96G); elytra each with (e.g., S. cactiventris) or without ayellowish spot; tarsus with 4th tarsomere simple (e.g., S. sakaii) or weakly bilobed; abdomenwith surface sparsely covered with suberect setae (Fig. 109A), and usually with punctures setiferous, elliptical (and round), large to very large on the anterior parts of 3rd (and 4th) segment(s),The Steninae of Japan Part 2

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while punctures setiferous, sparse to very sparse, very small to small on the other posterior segments; lateroventrites and tergoventrite sutures existing or missing. Male: Ninth ventrite withapicolateral tooth very short (Fig. 89B) to short (Fig. 87C) or moderately long (Liu et al., 2018:
ﬁg. 23), pointed, or 9th ventrite rarely only serrate apicolaterally (e.g., S. panthera); 9th ventrite
also usually without (Fig. 87C) but rarely with (S. lacrimulus) a posteromedian projection
between the apicolateral teeth. Female: Gonocoxite with apicolateral tooth (Fig. 87B); spermathecal duct stiff, strongly sclerotized (Figs. 87F, 93B), sometimes with a part of the duct forminga tightly coiled ductal mass (Fig. 96E).
A list of the species of S. cirrus-grouppanthera Hromádka, 2001 Distribution: India (Uttar Pradesh)echiniventris Puthz, 1981a Distribution: Vietnam (O-quy-ho)
deliculus Ryvkin, 1992 Distribution: Vietnam (Tam Dao)
aeneofulgens Puthz, 1998 Distribution: Vietnam (Tam Dao)cirripraestans Puthz, 2009 Distribution: Taiwan (Hsinchu)
cirricinctus Puthz, 2009 Distribution: Taiwan (Hsinchu)
cirrativestitus Puthz, 2009 Distribution: Taiwan (Ilan)
cirritunicatus Puthz, 2009 Distribution: Taiwan (Ilan, Chiai)
cirratitogatus Puthz, 2009 Distribution: Taiwan (Kaohsiung)
cirritogatus Puthz, 2009 Distribution: Taiwan (Kaohsiung, Pingtung, Chiai)
cirratus Puthz, 2009 Distribution: Taiwan (Nantou)
cirriger Puthz, 2009 Distribution: Taiwan (Nantou)
cirrimicans Puthz, 2009 Distribution: Taiwan (Nantou)
cirrimiriﬁcus Puthz, 2009 Distribution: Taiwan (Nantou)
cirriornatus Puthz, 2009 Distribution: Taiwan (Nantou)
cirrivestitus Puthz, 2009 Distribution: Taiwan (Nantou)
cirriostentans Puthz, 2012a Distribution: Taiwan (Nantou)
cirratitunicatus Puthz, 2009 Distribution: Taiwan (Pingtung)cirrivestis Puthz, 2009 Distribution: Taiwan (Taichung)cirrativestis Puthz, 2009 Distribution: Taiwan (Taoyuan)
cirrivarians Puthz, 2009 Distribution: Taiwan (Tauchung)lacrimulus Benick, 1942 Distribution: China (Fujian)wuyiensis Puthz, 2003a Distribution: China (Fujian)cooterianus Puthz, 2003a Distribution: China (Fujian)
mangdangshanus Liu, Tang & Luo, 2018 Distribution: China (Fujian)fujianensis Liu, Tang & Luo, 2018 Distribution: China (Fujian)cactiventris Puthz, 2003a Distribution: China (Guangdong)
xuwangi Tang & Li, 2008 Distribution: China (Guangdong)nanlingmontis Tang & Li, 2008 Distribution: China (Guangdong)huanghaoi Tang & Li, 2008 Distribution: China (Guangdong)luoleeorum de Rougemont, 2017 Distribution: China (Hong Kong)guangxiensis Rougemont, 1983 Distribution: China (Guanxi, Zhejiang)
splendidulus Puthz, 1983 Distribution: China (Guangxi)
zhangdinghengi Pan, Tang & Li, 2012 Distribution: China (Guangxi)
maoershanus Pan, Tang & Li, 2012 Distribution: China (Guangxi)

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hujiayaoi Liu & Tang, 2017 Distribution: China (Guangxi)
bullatus Liu & Tang, 2017 Distribution: China (Guangxi)
exesus Liu & Tang, 2017 Distribution: China (Guangxi)
damingshanus Liu & Tang, 2017 Distribution: China (Guangxi)
jinxiuensis Liu & Tang, 2017 Distribution: China (Guangxi)
lianhuashanus Liu & Tang, 2017 Distribution: China (Guangxi)
hechiensis Liu & Tang, 2017 Distribution: China (Guangxi)
dashaheensis Liu, Tang & Luo, 2017 Distribution: China (Guizhou)
zhangyuqingi Liu, Tang & Luo, 2017 Distribution: China (Guizhou)
liuyixiaoi Liu, Tang & Luo, 2017 Distribution: China (Guizhou)
fellowesi Puthz, 2003a Distribution: China (Hainan)
hainanensis Puthz, 2003a Distribution: China (Hainan)
andoi Tang, Li & Zhao, 2005 Distribution: China (Hubei)
parvus Puthz, 2012b Distribution: China (Hubei)
falsus Benick, 1940 Distribution: China (Jiangsu)
huangganmontium Puthz, 2003a Distribution: China (Jiangxi)
lijinweni Tang & Puthz, 2008 Distribution: China (Jianxi, Zhejiang)wugongshanus Yu, Tang & Yu, 2014 Distribution: China (Jiangxi)
mingyuueshanus Yu, Tang & Yu, 2014 Distribution: China (Jiangxi)
songxiaobini Yu, Tang & Yu, 2014 Distribution: China (Jiangxi)
nigritus Tang, Li & Zhao, 2005 Distribution: China (Shaanxi)
parviformis Puthz, 2012b Distribution: China (Shaanxi)
beckeri Benick, 1941 Distribution: China (Sichuan)aeneonitens Puthz, 1998 Distribution: China (Sichuan)
erlangmontium Puthz, 2012b Distribution: China (Sichuan)cariniventris Tang, Liu & Dong, 2018 Distribution: China (Sichuan)
jiangrixini Tang, Liu & Dong, 2018 Distribution: China (Sichuan)lineatus Tang, Liu & Dong, 2018 Distribution: China (Sichuan)emeishanus Tang, Liu & Dong, 2018 Distribution: China (Sichuan)
jiudingshanus Tang, Liu & Dong, 2018 Distribution: China (Sichuan)xichangensis Tang, Liu & Dong, 2018 Distribution: China (Sichuan)
brevilineatus Tang, Liu & Dong, 2018 Distribution: China (Sichuan)
cirrus Benick, 1940 Distribution: China (Zhejiang)
ovalis Tang, Li & Zhao, 2005 Distribution: China (Zhejiang)zhulilongi Tang & Puthz, 2008 Distribution: China (Zhejiang)
jiulongshanus Tang & Puthz, 2008 Distribution: China (Zhejiang)
shenshanjiai Tang & Puthz, 2008 Distribution: China (Zhejiang)
wuyanlingus Liu, Tang & Luo, 2017a Distribution: China (Zhejiang)
yuyimingi Liu, Tang & Luo, 2017a Distribution: China (Zhejiang)
yamabusi Naomi & Ito, 2015 Distribution: Japan (Shikoku)
nachiensis Puthz, 2001a Distribution: Japan (Honshu)
uedai Naomi, 2015b Distribution: Japan (Shikoku)
cirriformis Naomi, 1988b Distribution: Japan (Honshu)
angusticulus Naomi, Nomura & Puthz sp. nov. Distribution: Japan (Shikoku)
yashiro Naomi, 1994a Distribution: Japan (Kyushu)
domburi Hromádka, 1979a Distribution: Japan (Shikoku)

The Steninae of Japan Part 2

209＝longisetosus Puthz, 1993asakaii Naomi & Puthz, 1996 Distribution: Japan (Shikoku)
rasilis Naomi & Ito, 2015 Distribution: Japan (Shikoku)
sugiei Naomi, 1997b Distribution: Japan (Honshu)
caesariatus Naomi & Ito, 2015 Distribution: Japan (Honshu)
kanzeon Naomi, 2004 Distribution: Japan (Honshu)
sawadaianus Hromádka, 1979a Distribution: Japan (Honshu)
vernicosus Naomi & Nomura, 2015a Distribution: Japan (Honshu)
nyoirin Naomi, 2004 Distribution: Japan (Honshu)
Japanese fauna of the cirrus-group
The cirrus-group consists of 15 species in Japan. All of these species are indigenous to theJapanese Archipelago; and all are rare species. The Japanese species (excepting S. uedai) havethe abdomen of Hemistenus-type. The lateroventrites if present exist only in the 4th segment; andeach lateroventrite is both dorsally and ventrally demarcated by suture. The tergoventrite sutures
are distinct in the 5th to 6th segments. On the other hand, S. uedai has the abdomen of Hypostenus-type; and the lateroventrites and tergoventrite are missing in the 4th to 6th segments. In themost Japanese species (excepting S. nachiensis and S. rasilis), the endophallic expulsion hooks
show a unique structure. Namely, they are connected by a thin, arcuate or V-shaped string, so thatthey are almost or nearly M-shaped (e.g., Fig. 101F). Since they are diverse in structure in the
Chinese species (e.g., see Liu & Tang, 2017; Tang et al., 2018), the M-shaped condition is considered apomorphic.
Key to the Japanese species of S. cirrus-group
1(2)
2(1)
3(6)
4(5)

5(4)

6(3)
7(12)
8(11)
9(10)

10(9)

Male & female: Fourth to 6th abdominal segments not margined (Hypostenus-typed
abdomen; Fig. 109B) ................................................................................... S. uedai Naomi
Male & female: Fourth to 6th abdominal segments margined (Hemistenus-typed abdomen).
Male: Aedeagal median lobe broadened apically from the middle to the apicolateral corners (or median lobe broadest at apicolateral corners in apical 1/2).
Male: Aedeagal median lobe narrower (Fig. 87E); endophallic copulatory tube thicker,
curved behind the middle (Fig. 87E). Female: Spermathecal duct thicker, with two distinct turns (Fig. 87F) .................................................................. S. yamabushi Naomi & Ito
Male: Aedeagal median lobe broader (Fig. 88B); endophallic copulatory tube thinner, ﬂagellar, straight (Fig. 88B). Female: Spermathecal duct thinner, with coiled ductal mass at
1st turn (Fig. 88C) .................................................................................. S. nachiensis Puthz
Male: Aedeagal median lobe not broadened apically from the middle to the apicolateralcorners.
Male: Aedeagal median lobe distinctly broader in basal 1/2.
Male: Aedeagal median lobe narrower in apical 1/2; paramere shorter.
Male: Eighth ventrite with deeper emargination (Fig. 90G); endophallic copulatory tube
comprising the basal chamber and main tube (Fig. 90B); paramere thicker (Fig. 90B)..............................................................................................................S. cirriformis Naomi
Male: Eighth ventrite with shallower emargination (Fig. 91E); endophallic copulatory

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Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

tube double-structured (the basal Y-shaped structure and the ﬂagellum) (Fig. 91C); paramere thinner (Fig. 91C).......................... S. angusticulus Naomi, Puthz & Nomura sp. nov.
11(8) Male: Aedeagal median lobe broader in apical 1/2 (Fig. 100B); paramere longer (Fig.
100B)..................................................................................S. vernicosus Naomi & Nomura
12(7) Male: Aedeagal median lobe distinctly narrower in basal 1/2.
13(22) Male: Aedeagal median lobe more or less narrowed apically in apical 1/2.
14(17) Male: Aedeagal paramere not or only weakly spatulate.
15(16) Male: Aedeagal median lobe narrower (Fig. 92F); paramere not spatulate (Fig. 92F).
Female: Spermathecal duct with coiled ductal mass located at 1st turn (Fig. 92A)..................................................................................................... S. yashiro Naomi & Puthz
16(15) Male: Aedeagal median lobe broader (Fig. 93A); paramere weakly spatulate (Fig. 93A).
Female: Spermathecal duct strongly, irregularly coiled at 1st and 2nd turns (Fig. 93B) .....
............................................................................................................S. domburi Hromádka
17(14) Male: Aedeagal paramere strongly spatulate.
18(19) Male: Aedeagal median lobe with apical sclerotized area broader (Fig. 95B); endophallic
copulatory tube shorter, thicker (Fig. 95E) ........................................S. rasilis Naomi & Ito
19(18) Male: Aedeagal median lobe with apical sclerotized area narrower; endophallic copulatory tube longer, thinner.
20(21) Male: Aedeagal median lobe narrower behind the middle (Fig. 94E). Female: Spermathecal duct moderately coiled at 1st turn (Fig. 94F) .......................... S. sakaii Naomi & Puthz
21(20) Male: Aedeagal median lobe broader behind the middle (Fig. 96D). Female: Spermathecal duct with a coiled ductal mass at 1st turn (Fig. 96E) .............................S. sugiei Naomi
22(13) Male: Aedeagal median lobe parallel-sided from near the middle (or apical 1/3) to theapicolateral corners.
23(28) Male: Aedeagal median lobe narrower; endophallic expulsion hook thicker and shorter.
24(27) Male: Aedeagal median lobe with apical area longer; endophallic copulatory tube longer.
Female: Spermatheca with basal sclerotized duct usually longer.
25(26) Male: Endophallic expulsion hooks shorter, each anteriorly more or less rounded (Fig.
97A); copulatory tube thicker, longer, and not surrounded by the nock-like structure (Fig.
97B)........................................................................................... S. caesariatus Naomi & Ito
26(25) Male: Endophallic expulsion hooks longer, each anteriorly pointed (Fig. 98B); copulatory
tube thinner, shorter, and surrounded by the nock-like structure (Fig. 98B) ........................
.................................................................................................................. S. kanzeon Naomi
27(24) Male: Aedeagal median lobe with apical area shorter (Fig. 98D); endophallic copulatory
tube shorter (Fig. 99D). Female: Spermatheca with basal sclerotized duct usually short(Fig. 99B) ................................................................................... S. sawadaianus Hromádka
28(23) Male: Aedeagal median lobe broader (Fig. 101C); endophallic expulsion hook thinnerand longer (Fig. 101F) ...............................................................................S. nyoirin Naomi
Stenus yamabusi Naomi & Ito(Figs. 87A–F, 109A)
Stenus yamabusi Naomi & Ito, 2015: 207.
Stenus domburi Hromádka: Naomi, 1997: 3 (Fig. 1D), 6 (key).
Type material examined. Holotype : ♂ (EUMM), Yokono (680 m), Yanadani Vil., Ehime

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211

Fig. 87. Stenus yamabushi Naomi & Ito (A, C–E, Yokono, Ehime; B, F, Funat, Kochi). A, 9th and 10th terga of
male; B, posterior part of gonocoxite; C, 9th ventrite of male; D, posterior part of 8th ventrite of male; E,
aedeagus; F, spermatheca. Scale 1: 0.2 mm for A, C, E, 0.1 mm for B; Scale 2: 0.3 mm for D; Scale 3: 0.1 mm
for F.

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Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

Pref., 1–2. x. 1994, M. Sakai leg. Paratype: 1 ♀ (cN), Funato, Higashitsuno Vil., Takaoka, Kochi
Pref., 1. v. 1977, M. Yoshida leg.
Distribution. Japan: Shikoku (Ehime and Kochi Prefs.).
Redescription. Male and female: Body 5.0–7.1 mm (fore body 2.1–2.3 mm) in length, glossy
with head and abdomen strongly glittering; antennae thin, slender. Body black; labrum black;antennae and legs yellowish brown to reddish brown. Head relatively small, shallowly concave,with a pair of distinct longitudinal furrows; punctures round, moderately dense, small to moderately large, setiferous on the lateral parts of vertex, while punctures round, sparse, small, setiferous on the median longitudinal swollen area. Pronotum with surface uneven, with indistinct
median longitudinal furrow; punctures round to elliptical, very dense, small to moderately large,strongly coarse. Elytra with surface even; punctures round to elliptical, very dense, various in
size, strongly coarse. Tarsi each with 4th tarsomere very weakly bilobed. Abdomen with punctures elliptical, very dense, large to very large on anterior parts of 3rd and 4th segments; punctures round, moderately dense, moderately large on posterior parts of 3rd and 4th segments;
punctures round to elliptical, very sparse, very small to small on the other posterior segments.
Lateroventrites missing; tergoventrite sutures existing, thin.
Male: Eighth ventrite (Fig. 87D) posteromedially with a broad, arcuate emargination; 9th tergum (Fig. 87A) with antecostal apophyses very long, thin; 9th ventrite (Fig. 87C) not serrate posteriorly, with apicolateral teeth very short, acutely pointed, apicolateral setae very long; 10th tergum (Fig. 87A) rounded posteriorly. Aedeagal median lobe (Fig. 87E) elongate, gently roundedapicolaterally, obtusely angulate at apex; apical sclerotized area (Fig. 87E) well-developed,
extending anteriorly beyond the apicolateral corners along the lateral rims of median lobe. Endophallic median bands (Fig. 87E) with the basal bands fused, short, thin, and the folded bands
weakly diverging anteriorly, longer than the fused basal bands, each thin; expulsion hooks (Fig.
87E) almost M-shaped, each hook weakly incurved; copulatory tube (Fig. 87E) with basal chamber small, main tube attenuate but weakly curved and spiral behind the middle. Parameres (Fig.
87E) each distinctly spatulate, with pedicel rather thin; apical area furnished with 30 to 33 setaeof various lengths along mesial margin.
Female: Eighth ventrite rounded posteriorly; gonocoxites (Fig. 87B) each hardly serrate posteriorly, with apicolateral tooth short, pointed, apicolateral setae very long. Spermatheca (Fig.
87F) with capsule well-rounded at apex, small; RT-duct short, thin; duct moderately thick tothick, short with 2 turns; basal valve short; basal duct short.
Biology and ecology. S. yamabushi is distributed in the mountainous regions of the westernpart of Shikoku. The beetles inhabit leaf litter in the natural forests.
Remarks. S. yamabusi is allied to S. nachiensis, but it is separable from the latter species by
the aedeagal median lobe narrower, obtusely angulate at apex (Fig. 87E), the endophallic copulatory tube with its main tube thicker, weakly curved and spiral behind the middle (Fig. 87E), andthe spermathecal tube simple at the 1st turn (Fig. 87F).
Etymology. The speciﬁc epithet of this species is derived from the Japanese noun “yamabushi” which means “mountain ascetic”.
Stenus nachiensis Puthz(Fig. 88A–G)
Stenus nachiensis Puthz, 2001: 53; Naomi & Puthz, 2013: 141.

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213

Fig. 88. Stenus nachiensis Puthz (A, B, D–G, Tsutsumi, Wakayama; C, Nachi, Wakayama). A, 9th and 10th tergaof male; B, aedeagus; C, spermatheca; D, 9th ventrite of male; E, posterior part of 8th ventrite of male; F,
expulsion hooks; G, copulatory tube. Scale 1: 0.2 mm for A, B, D, 0.1 mm for G, 0.05 mm for F; Scale 2:
0.1 mm for C; Scale 3: 0.2 mm for E.

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Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

Type materal examined. Holotype: ♂ (MHNG), Mt. Nachi, Wakayama Pref., 13. vii. 1999, V.
Puthz leg.
Specimen examined. 1 ♂ (TUAA), Tsutsumi Valley, Shogun-gawa, Hiki-gawa, Wakayama
Pref., 31. x. 2001, S. Tanaka leg.
Distribution. Japan: Honshu (Wakayama Pref.).
Male and female. Body 3.2–4.1 mm (fore body 1.7–1.8 mm) in length, glossy with head andabdomen strongly glittering, antennae very thin. Body black; labrum black; antennae with basal
segments clear yellowish brown, apical segments reddish brown; legs yellowish brown to reddish brown. Head relatively small, shallowly concave, with a pair of distinct longitudinal furrows; punctures round, dense, setiferous on the lateral parts of vertex, while punctures sparse,
setiferous on the median longitudinal swollen area. Pronotum with surface weakly uneven, withindistinct median longitudinal furrow; punctures round, very dense, moderately large, coarse.
Elytra with surface almost even; punctures round to elliptical, very dense, large. Legs each with
4th tarsomere weakly bilobed. Abdomen with punctures elliptical, very dense, very large on anterior parts of 3rd and 4th segments; punctures round, dense, moderately large on posterior parts of
3rd and 4th segments; punctures very ﬁne, very sparse on other posterior segments. Lateroventrites missing; tergoventrite sutures thin.
Male: Eighth ventrite (Fig. 88E) posteromedially with a very broad, arcuate, arcuate emargination; 9th tergum (Fig. 88A) with antecostal apophyses very long; 9th ventrite (Fig. 88D) bisinuate at posterior margin, with apicolateral teeth very short, acutely pointed, apicolateral setae
long; 10th tergum (Fig. 88A) rounded posteriorly. Aedeagal median lobe (Fig. 88B) broad,broadest and gently rounded at apicolateral corners, acutely pointed at apex; apical sclerotizedarea (Fig. 88B) well-developed, extending anteriorly beyond the apicolateral corners along thelateral rims of median lobe, with a median longitudinal line. Endophallic median bands (Fig.
88B) with the basal bands long, fused, and the folded bands separated, each incurved, shorter
than the fused basal band; lateral bands (Fig. 88B) short, thin; expulsion hooks (Fig. 88F) widely
separated, each incurved posteriorly, acutely pointed, with a rounded posterior process; copulatory tube (Fig. 88G) with basal chamber elongate-conical, main tube weakly swollen basally,
then ﬂagellar and very thin. Parameres (Fig. 88B) each rounded at apex; apical area short, moderately swollen mesially at base, furnished with 21–22 setae of moderate length along mesial
margin.
Female: Eighth ventrite rounded posteriorly. Spermatheca (Fig. 88C) with capsule verysmall, rounded; RT-duct short, thin; duct thin to moderately thick, basically having two turns butwith a coiled ductal mass at the 1st turn; basal sclerotized duct moderately long. Basal structure
conical (Fig. 88C).
Biology and ecology. S. nachiensis is distributed in the mountainous regions of the easternpart of Kansai district, Honshu. At Mt. Nachi, the beetles inhabit leaf litter in the natural deciduous forests near the mountain streams (Puthz, 2001).
Remarks. S. nachiensis is allied to S. yamabushi, but it is separable from the latter species by
the aedeagal median lobe thicker and acutely pointed at apex (Fig. 88B), the endophallic copulatory tube with its main tube thinner, simply ﬂagellar (Fig. 88B), and the spermathecal duct with acoiled ductal mass at the 1st turn (Fig. 88G).

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215

Stenus uedai Naomi(Figs. 89A–G, 109B)
Stenus uedai Naomi, 2015: 37.
Type material examined. Holotype: ♂ (CBM), Mt. Unpenji, Ohnohara-chô, Kagawa Pref., 7.
viii. 2004, M. Yoshida leg. Paratypes: 1 ♂ (cN), same data as holotype; 1 ♂1 ♀ (cN), Mt.
Keisoku, Nishi-iyayama, Tokushima Pref., 13. x. 2002, K. Tanaka leg.
Distribution. Japan: Shikoku (Tokushima and Kagawa Prefs.).
Redescription. Male and female: Body 6.0–6.3 mm (fore body 2.5–2.7 mm) in length, glossy
with head and abdomen strongly glittering, antennae relatively short, very thin. Body black;labrum black; antennae with basal segments clear yellowish brown, apical segments brown todark brown; legs yellowish brown to reddish brown. Head relatively small, shallowly concave,with a pair of distinct longitudinal furrows; punctures round to elliptical, dense, small, setiferouson the lateral parts of vertex, while punctures very sparse, very small, setiferous on the medianlongitudinal swollen area. Pronotum with surface uneven, with indistinct median longitudinalfurrow; punctures round to almost round, very dense, moderately large, very coarse. Elytra withsurface weakly uneven; punctures round, very dense, moderately large to large, coarse. Tarsi
each with 4th tarsomere not bilobed. Abdomen with punctures ovoidal to elliptical, very dense,
large to very large, setiferous on anterior parts of 3rd and 4th segments; punctures very sparse,
very small, setiferous on posterior parts of 3rd and 4th segments and also on other posterior segments. Lateroventrites and tergoventrite sutures missing.
Male: Eighth ventrite (Fig. 89E) posteromedially with a broad, arcuate emargination; 9th tergum with antecostal apophyses long, thin; 9th ventrite (Fig. 89B) weakly rounded posteriorly,
with apicolateral teeth very short, pointed, apicolateral setae very long; 10th tergum (Fig. 89G)
entire. Aedeagal median lobe (Fig. 89C) moderately broad, distinctly angulate apicolaterally,
acutely pointed at apex; apical sclerotized area (Fig. 89C) well-developed, triangular, with a thin
median longitudinal suture. Endophallic median bands (Fig. 89C) with basal bands fused, long;lateral bands (Fig. 89C) thin; expulsion hooks (Fig. 89C) M-shaped, each almost cucumbershaped, weakly incurved; copulatory tube (Fig. 89D) with basal chamber having two rods of different length, main tube baculiform, with apical part slightly asymmetrically swollen left andright. Parameres (Fig. 89C) weakly divergent posteriorly at apical areas, each rather long,rounded at apex, with stem mesially having one short seta behind the middle; apical area very
long, furnished with 24–25 long setae along mesial margin.
Female: Eighth ventrite rounded posteriorly; gonocoxites (Fig. 89F) each with apicolateral
tooth short, pointed, apicolateral setae very long. Spermatheca (Fig. 89A) without capsule; RTduct relatively short, thin; duct robust with 2 characteristic turns, usually very thick but relatively
thin at the most basal part; basal valve very short; basal duct very short, broadened proximally;
gland spherical, densely covered with thin, long cilia, with its opening located on the caudal sideof duct near 2nd turn.
Biology and ecology. S. uedai is distributed in the low mountainous regions of the easternpart of Shikoku. The beetles inhabit leaf litter in the natural forests.
Remarks. Given their common possession of the well-angulated apicolateral corners of
aedeagal median lobe, the long parameres, the baculiform copulatory tube of endophallus, etc., S.
uedai seems to be allied to S. bullatus from China, but it is separable from the latter species by
the elytron unicolorate without macula, the median lobe with its apical sclerotized area larger

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Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

Fig. 89. Stenus uedai Naomi (Unpenji, Kagawa). A, spermatheca; B, 9th ventrite of male; C, aedeagus; D, copulatory tube; E, posterior part of 8th ventrite of male; F, posterior part of gonocoxite; G, 9th and 10th terga ofmale. Scale 1: 0.1 mm for A, D, F and 0.2 mm for B3–C, G; and scale 2: 0.3 mm for E.

The Steninae of Japan Part 2

217(Fig. 89C) and the spermatheca with its duct bent twice (Fig. 89A). S. uedai is easily separablefrom all other Japanese species by the median lobe with its apicolateral corners sharply angulated(Fig. 89C) and the spermatheca with its duct characteristically bent twice (Fig. 89A).
Etymology. This species is named in honor of Dr. Kyoichiro Ueda (Kitakyushu Museum andInstitute of Natural History, Kitakyushu), who studies the Noctuidae and also the fossil insects.
Stenus cirriformis Naomi(Fig. 90A–G)
Stenus cirriformis Naomi, 1988b: 34; Herman, 2001: 2126; Naomi & Puthz, 2013: 141.

leg.

Type material. Holotype: ♂ (KUF), Sandankyo, Hiroshima Pref., 13. viii. 1986, I. Okamoto

Type material examined. Paratype: 1 ♀ (cN), Sandankyo, Hiroshima Pref., 30. viii. 1986, I.
Okamoto leg.
Other material examined. [HONSHU]: 1 ♂, Mt. Garyu, Geihoku, Hiroshima Pref., 27. vi.
1987, I. Okamoto leg.
Distribution. Japan: Honshu (Hiroshima Pref.).
Redescription. Male and female: Body 5.0–5.3 mm (fore body 2.1–2.6 mm) in length, glossy
with head and abdomen strongly glittering, antennae relatively short, very thin. Body black;labrum black; antennae and legs yellowish brown to reddish brown. Head relatively small, moderately concave, with a pair of distinct longitudinal furrows; punctures almost round to round,very dense, various in size (small to large), setiferous on the lateral parts of vertex, while punctures sparse, small, setiferous on the median longitudinal swollen area. Pronotum with surface
uneven, with indistinct median longitudinal furrow; punctures almost round to round, very dense,
moderately large, rather coarse. Elytra with surface weakly uneven; punctures round to elliptical,very dense, moderately large to large, rugose. Tarsi each with 4th tarsomere weakly bilobed, eachlobe short, thin. Abdomen covered sparsely with suberect, thin setae; punctures round to elliptical, very dense, large to very large, setiferous on anterior part of 3rd segment; punctures round,
dense, moderately large, setiferous on posterior part of 3rd segment; punctures round, sparse tovery sparse, very small to small, setiferous on the other posterior segments. Lateroventrites existing in 4th and 5th segments, very narrow to narrow, punctate; tergoventral sutures thin in 6th
segment.
Male: Eighth ventrite (Fig. 90G) posteromedially with a broad, moderately deep emargination; 9th tergum with antecostal apophyses long; 9th ventrite (Fig. 90A) hardly serrate posteriorly, with apicolateral teeth very short, acutely pointed, apicolateral setae very long; 10th tergum
rounded posteriorly. Aedeagal median lobe (Fig. 90B) broad, elongate-subovoidal, strongly narrowed apically in about apical 1/2, hardly angulate at apicolateral corners, acutely pointed atapex; apical sclerotized area (Fig. 90B) almost elongate-triangular. Endophallic median bands(Fig. 90B) with basal band long, thin; lateral bands (Fig. 90B) long, moderately broad; expulsion
hooks (Fig. 90B) M-shaped; copulatory tube (Fig. 90B) simple, relatively short, with basal
chamber subovoidal, main tube attenuate. Parameres (Fig. 90B) thick, rounded at apex; apicalarea long, weakly spatulate, furnished densely with about 50 to 55 thin, long setae along mesial
margin.
Female: Eighth ventrite obtusely angulate posteromedially (Fig. 90F); 9th tergum simple(Fig. 90D); 10th tergum (Fig. 90D) entire; gonocoxites (Fig. 90E) each hardly serrate posteriorly,

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Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

Fig. 90. Stenus cirriformis Naomi (A, B, G, Garyu, Hiroshima; C–F, Sandankyo, Hiroshima). A, 9th ventrite ofmale; B, aedeagus; C, spermatheca; D, 9th and 10th terga of female; E, posterior part of gonocoxite; F, 8thventrite of female; posterior part of 8th ventrite of male. Scale 1: 0.2 mm for A, B, D, 0.1 mm for E; Scale 2:
0.1 mm for C; 0.2 mm for F; Scale 3: 0.2 mm for G.

The Steninae of Japan Part 2219with apicolateral tooth acutely pointed, apicolateral setae very long. Spermatheca (Fig. 90C) with
capsule almost missing; RT-duct relatively short; duct moderately thick to thick, tightly coiled toform a ductal mass at the 1st turn, with the duct from the base to 1st turn very long, straight;
basal valve very short; basal sclerotized duct very short. Basal structure (Fig. 90C) sclerotized,
bowl-shaped.
Biology and ecology. S. cirriformis is distributed in the mountainous regions of the central
part of Chugoku district, Honshu. The beetle inhabits leaf litter in the natural forests.
Remarks. S. cirriformis is allied to S. angusticulus, but it is separable from the latter species
by the 8th ventrite of male more deeply emarginate posteriorly (Fig. 90G), the aedeagal median
lobe with its apex broader (Fig. 90B), the endophallic copulatory tube simple in composition(basal chamber and main tube; Fig. 90B), and the aedeagal paramere thicker (Fig. 90B).
Stenus angusticulus Naomi, Nomura & Puthz sp. nov.
(Figs. 91A–E, 109C)Type material. Holotype: ♂ (NSMT-I-C-200330 in NMNST), Mt. Ishizuchi, Ehime Pref., 21.
vii. 1991, I. Okamoto leg.
Distribution. Japan: Shikoku (Ehime Pref.).
Description. Male: Body 5.0 mm (fore body 2.3 mm) in length, glossy with head and abdomen strongly glittering, antennae moderately long, very thin. Body black; labrum black; antennae and legs yellowish brown to reddish brown. Head relatively small, moderately concave, witha pair of distinct longitudinal furrows; punctures almost round to round, very dense, moderately
large to large, setiferous on the lateral parts of vertex, while punctures sparse, small, setiferouson the median longitudinal swollen area. Pronotum with surface uneven, with median longitudinal furrow shallow, broad near the center of pronotum; punctures round, very dense, moderately
large, rather coarse. Elytra with surface weakly uneven; punctures elliptical, very dense, large tovery large, strongly rugose especially near suture. Tarsi each with 4th tarsomere weakly bilobed,
each lobe short, thin. Abdomen covered sparsely with suberect, thin setae; punctures elliptical,very dense, large on anterior part of 3rd segment; punctures round, dense, moderately large, setiferous on posterior part of 3rd segment; punctures round, sparse to very sparse, very small tosmall, setiferous on other posterior segments. Lateroventrites existing only in 4th segment, narrow, punctate; tergoventral sutures thin in 5th and 6th segments.
Eighth ventrite (Fig. 91E) posteromedially with a broad, arcuate emargination; 9th tergum(Fig. 91A) with antecostal apophyses long; 9th ventrite (Fig. 91B) not serrate posteriorly, withmacrosetae very long, apicolateral teeth very short, acutely pointed, apicolateral setae very long;
10th tergum (Fig. 91A) rounded posteriorly. Aedeagal median lobe (Fig. 91C) broad, strongly
narrowed toward apex in about apical 1/3, distinctly constricted a little before the apicolateralcorners, rounded at apicolateral corners, pointed at apex; apical sclerotized area (Fig. 91C) very
narrow, elongate-triangular, with a median longitudinal line. Endophallic median bands (Fig.
91C) with basal bands fused, long, narrow; lateral bands (Fig. 91C) very long, thin; expulsion
hooks (Fig. 91C) M-shaped; copulatory tube (Fig. 91D) double-structured as follows: the basal
Y-shaped sclerite surrounded by the setal band at base, and the thin ﬂagellar tube, the basal
chamber of which is located inside the Y-shaped sclerite. Parameres (Fig. 91C) thin; apical area
long, moderately swollen mesially, furnished densely with about 35 to 40 thin, long setae alongmesial margin.

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Fig. 91. Stenus angusticulus Naomi, Nomura & Puthz sp. nov. (Ishizuchi, Ehime). A, 9th and 10th terga of male;B, 9th ventrite of male; C, aedeagus; D, copulatory tube with the densely pubescent basal part of inner sac; E,
8th ventrite of male. Scale 1: 0.2 mm for A, E; Scale 2: 0.2 mm for B, C, 0.1 mm for D.

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Female: Unknown.
Biology and ecology. S. angusticulus is presently collected only once from Mt. Ishizuchi
located at the northwestern part of Shikoku. The beetle inhabits leaf litter in the natural forest.
Remarks. S. angusticulus is allied to S. cirriformis, but it is separable from the latter species
by the 8th ventrite of male more shallowly emarginate posteriorly (Fig. 91E), the aedeagal
median lobe with its apex narrower (Fig. 91C), the endophallic copulatory tube double-structured(proximal Y-shaped structure and distal ﬂagellum; Fig. 91C), and the aedeagal paramere thinner(Fig. 91C).
Etymology. The speciﬁc epithet of this new species is derived from the Latin adjective“angustus / angusti-” which means “narrow” + a Latin diminutive “-culus”. The apex of aedeagal
median lobe is certainly narrow as in Fig. 91C.
Stenus yashiro Naomi & Puthz(Figs. 92A–H, 109D)
Stenus yashiro Naomi & Puthz, 1994: 257; Herman, 2001: 2438; Naomi & Puthz, 2013: 141;
Naomi & Ito, 2015: 208.
Stenus hirtellus Sharp, 1874: Naomi, 1988, 18: 65.
Type material examined. Holotype: ♂ (CBM), Ryumon Valley, Saga Pref., 23. x. 1977, H.
Ohishi leg. Paratype, 1 ♀ (cN), Mt. Unzen, Nagasaki Pref., 27. ix. 1977, S. Imasaka leg.
Other material examined. [KYUSHU]: 1 ♀, Mt. Kyogadake, Kashima City, Saga Pref., 13.
iii. 2000, S. Nomura leg.; 1 ♀, same locality, 17. iii. 1998, S. Nomura leg.
Distribution. Japan: Kyushu (Saga and Nagasaki Prefs.).
Redescription. Male and female: Body 3.2–3.6 mm (fore body 1.6–1.7 mm) in length, glossy
with head and abdomen strongly glittering, antennae short, thin. Body black; labrum black;antennae and legs yellowish brown to reddish brown. Head relatively small, weakly concave,with a pair of distinct longitudinal furrows; punctures round, moderately dense, small to moderately large, irregular, setiferous on the lateral parts of vertex, while punctures round, sparse,
small, setiferous on the median longitudinal swollen area. Pronotum with surface uneven, withindistinct median longitudinal furrow; punctures round to almost round, very dense, moderately
large, coarse. Elytra with surface weakly uneven; punctures round to almost round, very dense,
large, weakly coarse. Tarsi each with 4th tarsomere weakly bilobed. Abdomen with punctures
ovoidal to elliptical, very dense, large to very large, setiferous on anterior parts of 3rd to 5th segments; punctures very sparse, very small, irregular, setiferous on posterior parts of 3rd to 5th segments and on other posterior segments. Lateroventrites missing; tergoventral sutures thin.
Male: Eighth ventrite (Fig. 92H) posteromedially with a very shallow, arcuate emargination;
9th tergum (Fig. 92B) with antecostal apophyses short, thin; 9th ventrite (Fig. 92G) with apicolateral teeth very short, acutely pointed, apicolateral setae very long; 10th tergum (Fig. 92B) very
weakly emarginate posteriorly. Aedeagal median lobe (Fig. 92F) slender, acutely pointed apically. Endophallic median bands (Fig. 92D) with basal bands running in parallel; expulsion
hooks (Fig. 92E) M-shaped, each relatively broad, with anterior plate clearly demarcated by atransverse suture from posterior plate; copulatory tube (Fig. 92C) with basal chamber ovoidal,
main tube long, attenuate but weakly curved at apical part. Parameres (Fig. 92F) each thin; apicalarea long, hardly swollen mesially, furnished with 24–26 setae along mesial margin.
Female: Eighth ventrite bluntly pointed posteromedially; gonocoxites (Fig. 92I) each with

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Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

Fig. 92. Stenus yashiro Naomi & Puthz (A, I: Kyogatake, Saga: B–H: Ryumon, Saga). A, spermatheca; B, 9th
and 10th terga of male; C, copulatory tube (the arrows show the broken parts of main tube); D, median bands;
E, expulsion hooks; F, aedeagus; G, posterior part of 9th ventrite of male; H, 8th ventrite of male; I posterior
part of gonocoxite. Scale 1: 0.1 mm for A; Scale 2: 0.2 mm for F, 0.1 mm for C–E, G, I; Scale 3: 0.1 mm for
B; and Scale 4: 0.2 mm for H.

apicolateral tooth pointed, apicolateral setae long. Spermatheca (Fig. 92A) with capsule missing;RT-duct very thin; duct very thin to moderately thick, having 2 turns, with a small, coiled ductal
mass at 1st turn; basal valve short; basal duct very long, slender, straight. Basal structure conical,
membranous.
Biology and ecology. S. yashiro is distributed in the mountainous regions of northern
Kyushu. The beetles inhabit leaf litter in the natural forests.
Remarks. Given the small-sized body, the slender form of aedeagal median lobe, etc., S. yas-

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223

hiro seems to be related to S. nigritus from China, but it is separable from the latter species by
the 8th ventrite of male with its apicolateral tooth smaller (Fig. 92G), the endophallic expulsion
hook broader (Fig. 92E), and the spermathecal duct with a coiled ductal mass at the 1st turn (Fig.
92A). S. yashiro is easily separable from all the other Japanese members of cirrus-group by theaedeagal median lobe much narrower (Fig. 92F) and the spermathecal duct more slender (Fig.
92A).
Since only one male specimen of S. yashiro (whose endophallic copulatory tube was broken)
was examined, the copulatory tube was not able to be illustrated nor described unambiguously.
However, the copulatory tube may have a lateral ﬂap along the main tube, given that there exists
the subtransparent fragment of a ﬂap-like structure at the lateral side of the apical part of maintube (see the lower arrow in Fig, 92C).
Etymology. The speciﬁc epithet of this species is derived from the Japanese noun “yashiro”,
which means the place where the people enshrine the god in Japan.
Stenus domburi Hromádka(Figs. 93A–F, 109E)
Stenus domburi Hromádka, 1979: 101; Herman, 2001: 2164; Naomi & Puthz, 2013: 141; Naomi& Ito, 2015: 212.
Stenus longisetosus Puthz, 1993: 160; Naomi & Ito, 2015: 212 (synonym of S. domburi).
Type material examined. Holotype of S. domburi Hromádka: ♂ (NMP), Mt. Kazigamori,Tosa (Kochi Pref.), 21. vii. 1952, K. Sawada leg.
Holotype of S. longisetosus Puthz: ♂ (cP), Mt. Ishizuchi, Tsuchigoya (1,400 m), Ehime Pref.,Japan, 11–18. viii. 1980, S. & J. Peck leg. Paratype of S. longisetosus Puthz: ♂ (cN), same dataas the holotype.
Other material examined. [SHIKOKU]: 2 ♂2 ♀, Mt. Takamaru, Kamikatsu-cho, Tokushima
Pref., 19. vi. 2005, M. Yoshida leg.; 1 ♂, Mt. Kumoso, Kamiyama-cho, Tokushima Pref., 20. viii.
2005, M. Yoshida leg.; 1 ♂1 ♀, Mt. Kotsu, Yamakawa, Yoshinogawa city, Tokushima Pref., 24.
vii. 2005, M. Yoshida leg.; 1 ♂, Mt. Tsurugi, Minokoshi (1,340 m), Tokushima Pref., 11 x. 1999,
M. Yoshida leg.; 1 ♀, Mt. Ishizuchi, Ehime Pref., 21. vii. 1991, I. Okamoto leg.; 1 ♂, same locality, 16. ix. 1992, E. Yamamoto leg.; 1 ♂1 ♀, Mt. Tsutsujo, Ino-machi, Motokawa, Kochi Pref.,30. vi. 2007, T. & R. Miyata leg.; 1 ♂, Monobe, Kochi Pref., 23–24. ix. 2007, T. & R. Miyata
leg.
Distribution. Japan: Shikoku (Tokushima, Kochi and Ehime Prefs.).
Redescription. Male and female: Body 4.8–5.5 mm (fore body 2.1–2.5 mm) in length, glossy
with head and abdomen strongly glittering, antennae relatively short, very thin. Body black, butsometimes pronotum and elytra having reddish tinge; labrum black; antennae and legs yellowish
brown to reddish brown. Head relatively small, moderately concave, with a pair of distinct longitudinal furrows; punctures round, dense to very dense, small to moderately large, setiferous on
the lateral parts of vertex, while punctures sparse, small, setiferous on the median longitudinalswollen area. Pronotum with surface uneven, with indistinct median longitudinal furrow; punctures almost round to round, very dense, small, rugose. Elytra with surface weakly uneven; punctures round to elliptical, very dense, various in size (small to large), strongly rugose. Tarsi eachwith 4th tarsomere very weakly bilobed. Abdomen covered sparsely with suberect, thin setae;
punctures elliptical, very dense, large to very large, setiferous on anterior part of 3rd segment;

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Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

Fig. 93. Stenus domburi Naomi (A, B, D, E, Ishizuchi, Ehime; C, F, Takamaru, Tokushima). A, aedeagus; B,
spermatheca; C, 9th and 10th terga of male; D, gonocoxite; E, 9th ventrite of male; F, posterior part of 8th
ventrite of male. Scale 1: 0.2 mm for A, C, D, E; Scale 2: 0.1 mm for B; Scale 3: 0.2 mm for F.

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225puncture round, sparse, moderately large, setiferous on posterior part of 3rd segment; puncturesround, sparse to very sparse, very small to small, setiferous on other posterior segments. Lateroventrites missing; tergoventral sutures distinct in 4th to 6th segments.
Male: Eighth ventrite (Fig. 93F) posteromedially with an arcuate emargination; 9th tergum(Fig. 93C) with antecostal apophyses moderately long; 9th ventrite (Fig. 93E) hardly serrate posteriorly, with macrosetae very long, apicolateral teeth very short, acutely pointed, apicolateral
setae long; 10th tergum (Fig. 93C) rounded posteriorly. Aedeagal median lobe (Fig. 93A) elongate, strongly narrowed toward apex in about apical 1/2, pointed at apex; apical sclerotized area
(Fig. 93A) narrow, almost elongate-triangular. Endophallic median bands (Fig. 93A) with basal
bands fused, relatively short; lateral bands (Fig. 93A) moderately long and broad; expulsion
hooks (Fig. 93A) M-shaped; copulatory tube (Fig. 93A) with basal chamber elongate-ovoidal,
main tube comprising a very long ﬂagellum. Parameres (Fig. 93A) each thick, weakly spatulate
ae apex; apical area long, furnished densely with about 25 to 30 thin, long setae along mesial
margin.
Female: Eighth ventrite rounded posteriorly; gonocoxites (Fig. 93D) each very minutely or
hardly serrate posteriorly, with apicolateral tooth very short, acutely pointed, apicolateral setae
long to very long. Spermatheca (Fig. 93B) with capsule very small, rounded; RT-duct relatively
short; duct usually thin but moderately thick only at the distal part, strongly coiled at and near the
1st and 2nd turns, with the duct from the base to 1st turn very long, almost straight; basal valve
very short; basal sclerotized duct short. Basal structure (Fig. 93B) sclerotized, bowl-shaped.
Biology and ecology. S. domburi is widely distributed in the mountainous regions of Shikoku. The beetle inhabits leaf litter in the natural forests.
Remarks. S. domburi is allied to S. sakaii, but it is separable from the latter species by theaedeagal median lobe less strongly pointed apex (Fig. 93A), the endophallic copulatory tube with
its ﬂagellum thicker (Fig. 93A), the paramere less strongly spatulate (Fig. 93A), and the spermathecal duct thinner and more strongly coiled (Fig. 93B).
Etymology. The speciﬁc epithet of this species is derived from a Japanese noun “domburi”,
which means a “bowl”.
Stenus sakaii Naomi & Puthz(Figs. 94A–F, 109F)
Stenus sakaii Naomi & Puthz, 1996: 154; Herman, 2001: 2376; Naomi & Puthz, 2013: 141.
Type material examined. Holotype: ♂ (CMB), Mt. Saragamine (1100 m), Ehime Pref., 28. v.
1988. M. Sakai leg.
Other material examined. [SHIKOKU]: 1 ♂, Komenono, Ehime Pref., 23–24. v. 1970, S.
Kinoshita leg.; 1 ♂, Mt. Fukumi, Ehime Pref., 20. ix. 1970, M. Tomokuni leg.; 1 ♂, Mt. Odami,
Ehime Pref., 25. ix. 1993, I. Okamoto leg.; 1 ♀, same locality, 19. vii. 1993, M. Sakai leg.; 1 ♀,Sugitachi, Ehime Pref., 1. xi. 1992, I. Okamoto leg.; 1 ♂, Kuroson, Nishitosa Vil., Kochi Pref.,21. vi. 1999, T. Kan leg.; 1 ♀, same locality, 22–23. v. 1999, T. Kan leg.
Distribution. Japan: Shikoku (Ehime and Kochi Prefs.).
Redescription. Male and female: Body 4.3–5.5 mm (fore body 2.0–2.3 mm) in length, glossy
with head and abdomen strongly glittering, with antennae relatively short, very thin. Body black;labrum black; antennae yellowish brown to reddish brown, with apical segments infuscate; legs
yellowish brown to reddish brown. Head relatively small, shallowly concave, with a pair of dis-

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Shun-Ichiro Naomi, Shûhei Nomura and Volker Puthz

Fig. 94. Stenus sakaii Naomi & Puthz (A, B, F, Odami, Ehime; B, Kuroson, Kochi; D, Komenono, Ehime; E,
Saragamine, Ehime). A, 9th and 10th terga of male; B, 9th ventrite of male; C, gonocoxite; D, 8th ventrite ofmale; E, aedeagus; F, spermatheca. Scale 1: 0.2 mm for A–C, E; Scale 2: 0.2 mm for D, F.

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227

tinct longitudinal furrows; punctures round, dense, small to moderately large, setiferous on thelateral parts of vertex, while punctures sparse, small, setiferous on the median longitudinal swollen area. Pronotum with surface uneven, with indistinct median longitudinal furrow; puncturesround to elliptical, very dense, small to moderately large, rugose. Elytra with surface uneven;punctures round to elliptical, very dense, small to moderately large, rugose. Tarsi each with 4thtarsomere simple (not bilobed). Abdomen covered sparsely with suberect, thin setae; punctures
elliptical, very dense, large to very large, setiferous on anterior parts of 3rd and 4th segments;
punctures round, sparse, moderately large, setiferous on posterior part of 3rd segment; puncturesround, very sparse to sparse, very small to small, setiferous on posterior part of 4th segment andon other posterior segments. Lateroventrites missing; tergoventral sutures distinct in 4th to 6th
segments.
Male: Eighth ventrite (Fig. 94D) posteromedially with an arcuate, broad emargination; 9th
tergum (Fig. 94A) with antecostal apophyses moderately long; 9th ventrite (Fig. 94B) hardly serrate posteriorly, with macrosetae very long, apicolateral teeth very short, acutely pointed, apicolateral setae very long; 10th tergum (Fig. 94A) rounded posteriorly. Aedeagal median lobe (Fig.
94E) elongate, strongly narrowed apically in about apical 1/2, acutely pointed at apex; apicalsclerotized area (Fig. 94E) very small, elongate-triangular, anteriorly with a short, rounded projection, and also with a median longitudinal keel. Endophallic median bands (Fig. 94E) withbasal bands fused, moderately long, folded bands diverging anteriorly, shorter than basal bands;
lateral bands (Fig. 94E) long; expulsion hooks (Fig. 94E) M-shaped; copulatory tube (Fig. 94E)
with basal chamber elongate-ovoidal, small, main tube comprising a very long ﬂagellum. Parameres (Fig. 94E) strongly spatulate; apical area moderately long, furnished densely with about 23
to 25 thin, long setae along mesial margin.
Female: Eighth ventrite rounded posteriorly; gonocoxites (Fig. 94C) each hardly serrate posteriorly, with apicolateral tooth very short, acutely pointed, apicolateral setae long. Spermatheca(Fig. 94F) with capsule missing; RT-duct short, thin; duct moderately thick, irregularly coiled atand near the 1st turn, with the duct from the base to 1st turn long, straight; basal valve very short;basal sclerotized duct long. Basal structure (Fig. 94F) subconical, widely emarginate at base.
Biology and ecology. S. sakaii is distributed in the mountainous regions of the western partof Shikoku. The beetles inhabit leaf litter in the natural forests.
Remarks. S. sakaii is allied to S. domburi, but it is separable from the latter species by theaedeagal median lobe more strongly pointed apex (Fig. 94E), the endophallic copulatory tube
with its ﬂagellum thinner (Fig. 94E), the paramere more strongly spatulate (Fig. 94A), and thespermathecal duct thicker and less strongly coiled (Fig. 94B).
Etymology. This species is named in honor of Dr. Masahiro Sakai (Ehime University, Matsuyama), who studies the Anobiidae and other beetle families.
Stenus rasilis Naomi & Ito(Fig. 95A–F)
Stenus rasilis Naomi & Ito, 2015: 213.
Type material examined. Holotype: ♂ (EUMM), Mt. Tengu, Higashitsuno, Ehime Pref., 4. x.
2001, M. Sakai leg.
Distribution. Japan: Shikoku (Ehime Pref.).
Redescription. Male: Body 5.7 mm (fore body 2.2 mm) in length, glossy with head and228

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Fig. 95. Stenus rasilis Naomi & Ito (Tengu, Ehime). A, 9th and 10th terga of male; B, aedeagus; C, 9th ventrite;
D, posterior part of 8th ventrite of male; E, copulatory tube; F, expulsion hooks. Scale 1: 0.2 mm for A–C,
0.1 mm for E, F; Scale 2: 0.3 mm for D.

The Steninae of Japan Part 2229

abdomen strongly glittering. Body black; labrum black; antennae and legs yellowish brown toreddish brown. Head relatively small, shallowly concave, with a pair of longitudinal furrows;
punctures round, moderately dense, irregular, setiferous on the lateral parts of vertex, while
punctures rather sparse, small, setiferous on the median longitudinal swollen area. Pronotumwith surface uneven, with indistinct median longitudinal furrow; punctures very dense, rather
coarse. Elytra with surface weakly uneven; punctures very dense, large. Tarsi each with 4th tarsomere rather thin, weakly bilobed. Abdomen with punctures elliptical, dense to very dense,
large to very large on anterior parts of 3rd and 4th segments; punctures very small to small, very
sparse on posterior parts of 3rd and 4th segments and on other posterior segments. Lateroventrites missing; tergoventral sutures thin.
Eighth ventrite (Fig. 95D) posteromedially with a arcuate, shallow emargination; 9th tergum(Fig. 95A) with antecostal apophyses very long; 9th ventrite (Fig. 95C) not serrate posteriorly,
with apicolateral teeth very short, pointed; 10th tergum (Fig. 95A) obtusely pointed posteromedially. Aedeagal median lobe (Fig. 95B) slender, becoming gradually narrower toward apex in apical 1/2 but not very narrow even at apicolateral corners, more or less angulate at apicolateral corners, pointed at apex; apical sclerotized area (Fig. 95B) small, triangular, weakly turned dorsallywhen seen laterally. Endophallic expulsion hooks (Fig. 95F) connected at the mesial parts of posterior plates, each elongate, with anterior plate demarcated by an oblique line from posterior
plate, the posterior plate acutely pointed posteriorly; copulatory tube (Fig. 95E) with basal chamber almost elliptical, rounded anteriorly, main tube with basal tube baculiform, apical tube short,very thin. Parameres (Fig. 95B) each weakly swollen mesially near the middle of pedicel; apicalarea short, strongly swollen mesially, furnished densely with 27 to 29 long to very long setae
along mesial margin.
Female: Unknown.
Biology and ecology. S. rasilis is presently collected only once from the low mountainous
region of the northwestern part of Shikoku. The beetle inhabits leaf litter in the natural forest.
Remarks. S. rasilis is allied to S. sugiei, but it is separable from the latter species by theaedeagal median lobe less strongly pointed apically, with its apical sclerotized area shorter (Fig.
95B), the endophallic copulatory tube much shorter, with its main tube comprising the basal andapical tubes (Fig. 95E), and the parameral setae longer (Fig. 95B).
Stenus sugiei Naomi(Figs. 96A–G, 109G)
Stenus sugiei Naomi, 1997b: 3; Herman, 2001: 2409; Naomi & Puthz, 2013: 141.
Type material examined. Holotype: ♂ (CMB), Nabetani, Tatsunokuchi-cho, Ishikawa Pref.,28. vii. 1995. Y. Sugie leg. Paratypes: 1 ♂ (cN), same locality as holotype, 3. v. 1995, Y. Sugie
leg.; 1 ♂ (cN), same locality, 5. v. 1995, Y. Sugie leg.; 1 ♂1 ♀ (cN), same locality, 7. v. 1995, Y.
Sugie leg.; 1 ♀ (cN), same locality, 30. v. 1995, Y. Sugie leg.; 1 ♂1 ♀ (cN), same locality, 7. vi.
1995, Y. Sugie leg.; 1 ♀ (cN), same locality, 25. v. 1996, Y. Sugie leg.
Other material examined. [HONSHU]: 1 ♀, Ichinose, Mt. Hakusan, Ishikawa Pref., 4–14. ix.
2002, H. Hoshina leg.; 1 ♀, same locality, 31. viii. 2001, H. Hoshina leg.; 1 ♀, Bettou-deai, Mt.
Hakusan, Ishikawa Pref., 12. vii. 2002, H. Hoshina leg.; 1 ♂, Mennoki Pass, Aichi Pref., 20. ix.
1978, M. Sato leg.
Distribution. Japan: Honshu (Ishikawa and Aichi Prefs.).

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Fig. 96. Stenus sugiei Naomi (A, F, G, Mennoki, Aichi; B–E, Nabetani, Ishikawa). A, 9th and 10th terga of male;B, 9th ventrite of male; C, gonocoxite; D, aedeagus; E, spermatheca; F, posterior part of 8th ventrite of male;G, paraglossae (with the apices which are weakly bent mesially). Scale 1: 0.2 mm for A–D, 0.1 mm for G;
Scale 2: 0.1 mm for E; Scale 3: 0.2 mm for F.

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231

Redescription. Male and female: Body 4.0–5.0 mm (fore body 1.8–2.3 mm) in length, glossy
with head and abdomen strongly glittering, with antennae short, thin. Body black; labrum black;antennae and legs yellowish brown to reddish brown. Head relatively small, shallowly concave,with a pair of distinct longitudinal furrows; punctures round, very dense, small to moderately
large, setiferous on the lateral parts of vertex, while punctures sparse to moderately dense, small,
setiferous on the median longitudinal swollen area. Pronotum with surface uneven, with indistinct median longitudinal furrow; punctures round to elliptical, very dense, small, rugose. Elytra
with surface uneven; punctures round to elliptical, very dense, small to moderately large, rugose,sometimes two or more punctures partially fused. Tarsi each with 4th tarsomere simple (notbilobed). Abdomen covered sparsely with suberect, thin setae; punctures elliptical, very dense,
large to very large, setiferous on anterior parts of 3rd and 4th segments; punctures round to elliptical, sparse to moderately dense, small to moderately large, irregular, setiferous on posterior
parts of 3rd and 4th segments; punctures round, very sparse to sparse, very small to small, setiferous on other posterior segments. Lateroventrites missing or existing (very thin, punctate) only
in 4th segment; tergoventral sutures distinct in 4th to 6th segments.
Male: Eighth ventrite (Fig. 96F) posteromedially with an arcuate, shallow emargination; 9th
tergum (Fig. 96A) with antecostal apophyses moderately long; 9th ventrite (Fig. 96B) hardly serrate posteriorly, with macrosetae very long, apicolateral teeth very short, acutely pointed, apicolateral setae very long; 10th tergum (Fig. 96A) rounded posteriorly. Aedeagal median lobe (Fig.
96D) slender, narrowed toward apex in about apical 1/2, very acutely pointed at apex; apicalsclerotized area (Fig. 96D) small, elongate-triangular, with a median longitudinal keel. Endophallic median bands (Fig. 96D) with basal bands fused, narrow, short; expulsion hooks (Fig.
96D) M-shaped; copulatory tube (Fig. 96D) with basal chamber elliptical, narrow, main tube
very long, ﬂagellar. Parameres (Fig. 96D) each strongly spatulate; apical area moderately long,
furnished mesially with about 10 to 15 long setae along ventral margin, and with about 25 to 30
short setae along apical and dorsal margins.
Female: Eighth ventrite rounded posteriorly; gonocoxites (Fig. 96C) each hardly serrate posteriorly, with apicolateral tooth very short, acutely pointed, apicolateral setae long. Spermatheca(Fig. 96E) with capsule small, ovoidal; RT-duct very short, thin; duct moderately thick, strongly
coiled at the 1st turn to form a ductal mass, with the duct from the base to 1st turn long, straight;
basal valve very short; basal sclerotized duct long.
Biology and ecology. S. sugiei is distributed in the plains to mountainous regions of the western part of Chubu district, central Honshu. The beetles inhabit leaf litter in the natural forests.
Remarks. S. sugiei is allied to S. rasilis, but it is separable from the latter species by theaedeagal median lobe more strongly pointed apically, with its apical sclerotized area longer (Fig.
96D), the endophallic copulatory tube much longer, with its main tube simply ﬂagellar (Fig.
96D), and the parameral setae shorter (Fig. 96D).
Etymology. This species is named in honor of Mr. Yoshiharu Sugie (Tatunokuchi, Ishikawa),
who collected the Stenus-beetle that was designated as the holotype.
Stenus caesariatus Naomi & Ito(Figs. 97A–G, 109H)
Stenus caesariatus Naomi & Ito, 2015: 210.
Type material examined. Holotype: ♂ (KUM), Obara, Saji-mura, Tottori Pref., 5. vi. 1988, N.

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Fig. 97. Stenus caesariatus Naomi & Ito (A, D, E: Akagai, Hyogo; B, C, F, G: Obara, Tottori). A, B, aedeagus;
C, 9th and 10th terga of male; D, spermatheca; E, posterior part of gonocoxite; F, 9th ventrite; G, 8th ventriteof male. Scale 1: 0.1 mm for A, B, D; Scale 2: 0.2 mm for C, F, G, 0.1 mm for E.

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233

Tsurusaki leg. Paratypes: 1 ♂ (cN), Tottori City, Tottori Pref., 7. viii. 1992, A. Hayakawa leg.;1 ♂ (cN), Kaya-cho, Kyoto, 5. v. 2004, K. Yasukawa leg.; 1 ♀, Sasayama, Hyogo, 18. ix. 1983,
T. Ito leg.; 1 ♀, Akazai, Hyogo, 3. vi. 1979, T. Ito leg.; 1 ♂, same locality, 17. vi. 1979, T. Itoleg.; 4 ♀, same locality, 23. ix. 1979, T. Ito leg.; 2 ♂1 ♀, same locality, 15. ix. 1986, T. Ito leg.
Distribution. Japan: Honshu (Tottori, Hyogo and Kyoto Prefs.).
Redescription. Male and female: Body 4.3–5.0 mm (fore body 1.8–2.1 mm) in length, glossy
with head and abdomen strongly glittering, with antennae relatively short, thin. Body black;labrum black; antennae and legs yellowish brown to reddish brown. Head relatively small, shallowly concave, with a pair of longitudinal furrows; punctures round to elliptical, dense, small tomoderately large, setiferous on the lateral parts of vertex, while punctures sparse to moderately
dense, small, setiferous on the median longitudinal swollen area. Pronotum with surface weakly
uneven, with median longitudinal furrow missing or very indistinct; punctures round, very dense,
small to moderately large, weakly coarse. Elytra with surface weakly uneven; punctures round toalmost round, small to moderately large, weakly coarse. Tarsi each with 4th tarsomere hardly or
weakly bilobed. Abdomen with punctures ovoidal to elliptical, very dense, large on anterior partsof 3rd and 4th segments; punctures round, very small to small, very sparse to sparse on posterior
parts of 3rd and 4th segments and on other posterior segments. Lateroventrites very narrow,
punctate only in 4th segment; tergoventrite sutures distinct in 5th and 6th segments.
Male: Eighth ventrite (Fig. 97G) posteromedially with an arcuate, broad emargination; 9th
tergum (Fig. 97C) with antecostal apophyses short; 9th ventrite (Fig. 97F) not serrate posteriorly,
with macrosetae very long, apicolateral teeth very short, acutely pointed, apicolateral setae very
long; 10th tergum (Fig. 97C) rounded posteriorly. Aedeagal median lobe (Fig. 97A, B) bulbous
in basal 3/5, almost parallel-sided between the basal 3/5 and the apicolateral corners, more orless pointed at apex; apical sclerotized area (Fig. 97A, B) subtriangular, small. Endophallic
median bands (Fig. 97A, B) with basal bands separated at anterior parts, each very thin, long; lateral bands (Fig. 97B) long, thin; expulsion hooks (Fig. 97A, B) M-shaped, each more or lessrounded apically; copulatory tube (Fig. 97A, B) very long, with basal chamber elongate-subovoidal, large, main tube attenuate, ﬂagellar in apical 1/2 (Fig. 97A, B). Parameres (Fig. 97A, B)
each weakly spatulate; apical area long, furnished with 25 to 27 long to very long setae alongmesial margin.
Female: Eighth ventrite rounded posteriorly; gonocoxites (Fig. 97E) each indistinctly serrate
posteriorly, with apicolateral tooth acutely pointed, apicolateral setae very long. Spermatheca(Fig. 97D) with capsule spherical, small; RT-duct short, thin; duct moderately thick to thick,short with 2 turns, and with a relatively large coiled ductal mass at the 1st turn; basal valve very
short; basal duct long, narrow, straight.
Biology and ecology. S. caesariatus is distributed in the plains and low mountainous regionsof the eastern part of Chugoku district and the northern part of Kinki district, Honshu. The beetles inhabit leaf litter in the natural forests.
Remarks. Given their common possessions of the unique structures (aedeagal median lobe
elongate-subovoidal at base, then parallel sided before the apicolateral corners; spermathecal
duct with a coiled ductal mass at or around the 1st turn; etc.), S. caesariatus, S. kanzeon and S.
sawadaianus are allied phylogenetically. S. caesariatus is separable from the latter two species
by the 9th tergum with its antecostal apophysis shorter (Fig. 97C), the aedeagal median lobe lessstrongly pointed (Fig. 97A, B), and the copulatory tube longer (Fig. 97A, B).

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Stenus kanzeon Naomi(Figs. 98A–G, 109I)
Stenus kanzeon Naomi, 2004: 19; Naomi & Puthz, 2013: 141.
Type material examined. Holotype: ♂ (CBM), Fukumizu, Hakui City, Ishikawa Pref., 20. x.
1995, T. Kishimoto leg. Paratypes: 1 ♂1 ♀ (cP) & 1 ♂3 ♀ (cN), same locality as holotype.
Distribution. Japan: Honshu (Ishikawa Pref.).
Redescription. Male and female: Body 4.8–5.0 mm (fore body 1.9–2.1 mm) in length, glossy
with head and abdomen strongly glittering, with antennae short, thin. Body black; labrum black;antennae and legs yellowish brown to reddish brown. Head relatively small, shallowly concave,with a pair of distinct longitudinal furrows; punctures round, very dense, small to large, setiferous on the lateral parts of vertex, while punctures sparse to moderately dense, small to moderately large, setiferous on the median longitudinal swollen area. Pronotum with surface uneven,with indistinct median longitudinal furrow; punctures round to almost round, very dense, small,coarse. Elytra with surface slightly uneven; punctures round to elliptical, very dense, moderately
large to large, coarse, sometimes two or more punctures partially fused. Tarsi each with 4th tarsomere simple (not bilobed). Abdomen covered sparsely with suberect, thin setae; punctures elliptical, very dense, large to very large, setiferous on anterior parts of 3rd and 4th segments; punctures round to elliptical, sparse to moderately dense, small to medium-sized, irregular, setiferous
on posterior part of 3rd segment; punctures round, very sparse to sparse, very small to small, setiferous on posterior part of 4th segment and on other posterior segments. Lateroventrites very
thin, punctate in 4th segment; tergoventral sutures distinct in 4th to 6th segments.
Male: Eighth ventrite (Fig. 98F) posteromedially with an arcuate, very broad emargination;
9th tergum (Fig. 98A) with antecostal apophyses long; 9th ventrite (Fig. 98C) hardly serrate posteriorly, with macrosetae long to very long, apicolateral teeth very short, acutely pointed, apicolateral setae long; 10th tergum (Fig. 98A) rounded posteriorly. Aedeagal median lobe (Fig. 98B)
elongate, almost parallel-sided between the basal 3/5 and the apicolateral corners, acutely
pointed at apex; apical sclerotized area (Fig. 98B) small, elongate-triangular, with a median longitudinal keel. Endophallic median bands (Fig. 98B) with basal bands fused, narrow, relatively
short; lateral bands (Fig. 98B) long, thin; expulsion hooks (Fig. 98B) M-shaped, each acutely
pointed and weakly incurved at anterior tip; copulatory tube (Fig. 98B) moderately long, withbasal chamber elongate-ovoidal, main tube comprising a very long ﬂagellum. Parameres (Fig.
98B) each spatulate; apical area long, furnished with 27 to 33 long setae along mesial margin.
Female: Eighth ventrite rounded posteriorly; gonocoxites (Fig. 98E) each hardly serrate posteriorly, with apicolateral tooth very short, acutely pointed, apicolateral setae long. Spermatheca(Fig. 98D) with capsule very small; RT-duct very short, thin; duct moderately thick to thick,strongly coiled around the 1st turn to form a ductal mass; basal valve very short; basal sclerotized duct long, very thin to thin.
Biology and ecology. S. kanzeon is only once collected from a plain of the northwestern partof Chubu district, central Honshu. The beetles inhabit leaf litter in the natural forests.
Remarks. S. kanzeon is allied to S. caesariatus and S. sawadaianus, but it is separable fromthe latter two species by the endophallic expulsion hook longer, each acutely pointed and weakly
incurved at anterior tip (Fig. 98B), and the copulatory tube with its main tube thinner at base andsurrounded by the nock-like structure (Fig. 98B). In the spermatheca of S. kanzeon, the size ofthe ductal mass formed around the 1st turn of duct varies. The ductal mass is rather large as in

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Fig. 98. Stenus kanzeon Naomi (Fukumizu, Ishikawa). A, 9th and 10th terga of male; B, aedeagus; C, 9th ventrite of male; D, spermatheca; E, gonocoxite; F, posterior part of 8th ventrite of male; G, 9th and 10th terga offemale. Scale 1: 0.2 mm for A–F; Scale 2: 0.2 mm for G.

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Fig. 98D in one female, but it is a little more compact and small in some other females.
Etymology. The speciﬁc epithet of this species is derived from the “Kanzeon”, which is theJapanese name of a Bodhisattva.
Stenus sawadaianus Hromádka(Figs. 99A–F, 109J)
Stenus sawadaianus Hromádka, 1979a: 100; Herman, 2001: 2379; Naomi & Puthz, 2013: 141.
Type material examined. Holotype: ♂ (NMP), Mt. Hiei, Yamashiro, Kyoto Pref., 3. x. 1954,
K. Sawada leg.
Other material examined. [HONSHU]: 2 ♂2 ♀, Hanase, Kyoto Pref., 21. ix. 1990, T. Itoleg.; 1 ♀, same locality, 4. vii. 1987, T. Ito leg.; 1 ♀, same locality, 2. x. 1987, T. Ito leg.; 1 ♀,same locality, 26. x. 1991, T. Ito leg.; 4 ♀, Ashiu, Kyoto Pref., 5. ix. 1992, T. Ito leg.; 1 ♂, Mt.
Daihi, Kyoto Pref., 30. iv. 1987, T. Ito leg.; 1 ♀, Mt. Daihi, Kyoto Pref., 19. ix. 1987, T. Ito leg.
Distribution. Japan: Honshu (Kyoto Pref.).
Redescription. Male and female: Body 4.6–5.8 mm (fore body 2.0–2.5 mm) in length, glossy
with head and abdomen strongly glittering, with antennae short, thin. Body black; labrum black;antennae and legs yellowish brown to reddish brown. Head relatively small, shallowly concave,with a pair of distinct longitudinal furrows; punctures round to elliptical, dense to very dense,
various in size (small to large), setiferous on the lateral parts of vertex, while punctures very
sparse, very small, setiferous on the median longitudinal swollen area. Pronotum with surface
uneven, with indistinct median longitudinal furrow; punctures round to almost round, very dense,
small, coarse, sometimes two or more punctures fused. Elytra with surface uneven; puncturesround to elliptical, very dense, moderately large to large, subrugose, sometimes two or more
punctures partially fused. Tarsi each with 4th tarsomere simple. Abdomen covered sparsely with
suberect, thin setae; punctures elliptical, very dense, large to very large, setiferous on anterior
parts of 3rd and 4th segments; punctures round, sparse, small, setiferous on posterior part of 3rd
segment; punctures round, very sparse, very small, setiferous on posterior part of 4th segment
and on other posterior segments. Lateroventrites very thin, punctate in 4th segment, existing or
missing in 5th segment; tergoventral sutures distinct in 4th to 6th segments.
Male: Eighth ventrite (Fig. 99F) posteromedially with a broad, subtriangular emargination;
9th tergum (Fig. 99C) with antecostal apophyses moderately long; 9th ventrite (Fig. 99A) not
serrate posteriorly, with apicolateral teeth very short, acutely pointed, apicolateral setae very
long; 10th tergum (Fig. 99C) rounded posteriorly. Aedeagal median lobe (Fig. 99D) subovoidal
in basal 4/7, parallel-sided from near the apical 3/7 to the apicolateral corners, acutely pointed atapex; apical sclerotized area (Fig. 99D) small, subtriangular, with a median longitudinal keel.
Endophallic median bands (Fig. 99D) with basal bands separated at anterior parts, each very narrow, long; lateral bands (Fig. 99D) long; expulsion hooks (Fig. 99D) M-shaped; copulatory tube
(Fig. 99D) with basal chamber elongate-ovoidal, main tube with basal tube thick, apical tube ﬂagellar. Parameres (Fig. 99D) each moderately thick, spatulate; apical area moderately long, furnished densely with about 30 to 35 long setae along mesial margin.
Female: Eighth ventrite rounded posteriorly; gonocoxites (Fig. 99E) each posteriorly hardly
serrate or with 1 small tooth, apicolateral tooth very short, acutely pointed, apicolateral setae
long. Spermatheca (Fig. 99B) with capsule small, spherical; RT-duct short, thin; duct thick tovery thick, strongly coiled at the 1st turn to form a ductal mass; basal valve very short; basal duct

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Fig. 99. Stenus sawadaianus Naomi (A, C, D, F, Daihi, Kyoto; B, E, Seryo, Kyoto). A, 9th ventrite of male; B,
spermatheca; C, 9th and 10th terga of male; D, aedeagus; E, gonocoxite; F, 8th ventrite of male. Scale 1:
0.2 mm for A–D, 0.1 mm for E; Scale 2: 0.2 mm for F.

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short.
Biology and ecology. S. sawadaianus is distributed in the plains to mountainous regions of
the northwestern part of Kinki district, Honshu. The beetles inhabit leaf litter in the natural forests.
Remarks. S. sawadaianus is allied to S. caesariatus and S. kanzeon, but it is separable fromthe latter two species by the aedeagal median lobe with its apical triangular part from the apicolateral corners to the apex shorter (Fig. 99D), the endophallic copulatory tube shorter (Fig. 99D),
and the spermatheca with its duct thicker and its basal sclerotized duct short (Fig. 99B).
Etymology. This species is named in honor of Dr. Kohei Sawada (Takatsuki, Osaka).
Stenus vernicosus Naomi & Nomura(Figs. 100A–G, 109K)
Stenus vernicosus Naomi & Nomura, 2015: 59.
Type material examined. Holotype: ♂ (NMNST), Mt. Daisen (Yokote-michi, NW slope
820 m), Daisen-cho, Tottori Pref., 7. ix. 1984, Y. Nishikawa leg. Paratypes: 2 ♀ (cN), Mt.
Kenashi, Tottori City, Tottori Pref., 23. v. 1989, N. Tsurusaki leg.
Distribution. Japan: Honshu (Tottori Pref.).
Redescription. Male and female: Body 4.0–4.3 mm (fore body 2.0–2.1 mm) in length, glossy
with head and abdomen strongly glittering, antennae relatively short, thin. Body black; labrum
black; antennae with basal segments yellowish brown, apical segments brown to dark brown;legs yellowish brown to reddish brown. Head relatively small, weakly concave, with a pair ofdistinct longitudinal furrows; punctures round to almost round, dense, small to moderately large,
setiferous on the lateral parts of vertex, while punctures very sparse, very small, irregular, setiferous on the median longitudinal swollen area. Pronotum with surface weakly uneven, with indistinct median longitudinal furrow; punctures round to almost round, very dense, small to moderately large, coarse. Elytra with surface uneven; punctures round to almost round, very dense,
moderately large to large, coarse. Abdomen with punctures ovoidal to elliptical, dense to very
dense, large to very large on anterior parts of 3rd and 4th segments; punctures very sparse, verysmall, irregular, setiferous on posterior parts of 3rd and 4th segments and on other posterior segments Lateroventrites very thin, punctate in 4th to 5th segments; tergoventrite sutures distinct in
6th segment.
Male: Eighth ventrite (Fig. 100E) posteromedially with an arcuate, broad emargination; 9th
tergum with ventral apophyses long, thin; 9th ventrite (Fig. 100A) not serrate posteriorly, withmacrosetae very long, apicolateral teeth very short, acutely pointed, apicolateral setae very long;
10th tergum (Fig. 100C) rounded posteriorly. Aedeagal median lobe (Fig. 100B) broad, weakly
narrowed apically from near the apical 1/3 to the apicolateral corners, obtusely angulate at apicolateral corners, acutely pointed at apex; apical sclerotized area (Fig. 100B) developed, extending
anteriorly along the lateral rims of median lobe, with a thin median longitudinal suture. Endophallic median bands (Fig. 100D) with basal bands long, fused except for anterior tips, folded
bands fused in about basal 2/3, about as long as basal bands; lateral bands (Fig. 100D) long, thin;
expulsion hooks (Fig. 100D) almost M-shaped, with anterior plate weakly incurved at anterior
tip, demarcated by a suture from posterior plate; copulatory tube (Fig. 100D) long, with basal
chamber large, subconical, main tube attenuate, very thin. Parameres (Fig. 100B) each robust,
furnished mesially with 5 to 6 setae at distal part of stem; apical area long, moderately swollen

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239

Fig. 100. Stenus vernicosus Naomi & Nomura (A–E: Daisen, Tottori; F, G: Kenashi, Tottori). A, 9th ventrite ofmale; B, posterior part of aedeagus; C, 9th and 10th terga of male; D, apical part of median lobe with the outthrusted endophallus; E, posterior part of 8th ventrite of male; F, spermatheca; G, posterior part of gonocoxite.
Scale: 0.2 mm for A–E, 0.1 mm for F, G.

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mesially, with about 40 long setae along mesial margin.
Female: Eighth ventrite rounded posteriorly; gonocoxites (Fig. 100G) each hardly or
minutely serrate posteriorly, with apicolateral tooth acutely pointed, apicolateral setae very long.
Spermatheca (Fig. 100F) robust, with capsule small, weakly narrowed toward the rounded tip;
RT-duct short; duct very thick, short with 2 turns, tightly coiled to form a tuberculous ductal
mass between the 1st and 2nd turns; basal valve very short; basal duct short, moderately thick.
Biology and ecology. S. vernicosus is distributed in the mountainous regions of the central
area of Chugoku district, Honshu. The beetles inhabit leaf litter in the natural forests.
Remarks. S. vernicosus is allied to S. nyoirin, but it is separable from the latter species by theaedeagal median lobe weakly narrowed apically from near the apical 1/3 to the apicolateral corners (Fig. 100B), the endophallic expulsion hook weakly incurved at the anterior tip (Fig. 100D),
and the spermatheca with its duct thicker, and its basal sclerotized duct much shorter (Fig. 100F).
Stenus nyoirin Naomi(Figs. 101A–G, 109L)
Stenus nyoirin Naomi, 2004: 21; Naomi & Puthz, 2013: 141.
Type material examined. Holotype: ♂ (CBM), Nomugi Pass, Nagawa Vil., Nagano Pref., 8.
viii. 1996, T. Kishimoto leg. Paratypes: 1 ♀ (cN), Mt. Kiso-komagadake, Nagano Pref., 21. ix.
1996, T. Kishimoto leg.; 1 ♂ (cN), Hirayu, Gifu Pref., 24. vii. 1987, S. Nomura leg.
Other material examined. [HONSHU]: 1 ♀, Mitsumata, Horisane Vil., Nagano Pref., 18. viii.
1991, T. Watanabe leg.; 2 ♀, Kawashima, Shimoina-gun, Nagano Pref., 23. viii. 1997, H. Sakayori leg.; 1 ♀,Ohshirakawa forest road, Azumi, Matsumoto City, Nagano Pref., 11. ix. 2009, T.
Watanabe leg.; 1 ♂2 ♀, Tsukechi Valley, Kakomo Vil., Gifu Pref., 15. xi. 1999, S. Nomura leg.
Distribution. Japan: Honshu (Nagano and Gifu Prefs.).
Redescription. Male and female: Body 4.9–6.0 mm (fore body 2.3–2.5 mm) in length, withhead and abdomen strongly glittering, pronotum and elytra weakly to moderately shining, withantennae short, very thin. Body black, but pronotum and elytra somewhat having reddish tinge;
labrum black; antennae and legs yellowish brown to reddish brown or dark brown. Head relatively small, shallowly concave, with a pair of distinct longitudinal furrows; punctures round toalmost round, moderately dense to dense, small to moderately large, setiferous on the lateralparts of vertex, while punctures round, very sparse, small to moderately large, setiferous on the
median longitudinal swollen area. Pronotum with surface uneven, with indistinct median longitudinal furrow; punctures round to almost round, very dense, small, subrugose. Elytra with surface
slightly uneven; punctures round to elliptical, very dense, moderately large to large, subrugose,sometimes two or more punctures partially fused. Tarsi each with 4th tarsomere simple (notbilobed). Abdomen covered sparsely with suberect, thin setae; punctures ovoidal to elliptical,very dense, large to very large, setiferous on anterior parts of 3rd and 4th segments; puncturesround, sparse to moderately dense, small, setiferous on posterior part of 3rd segment; puncturesround, very sparse, very small to small, setiferous on posterior part of 4th segment and on otherposterior segments. Lateroventrites very thin, punctate in 4th segment; tergoventral sutures distinct in 4th to 6th segments.
Male: Eighth ventrite (Fig. 101E) posteromedially with a very broad, arcuate emargination;
9th tergum (Fig. 101A) with antecostal apophyses long; 9th ventrite (Fig. 101B) not serrate posteriorly, with macrosetae long to very long, apicolateral teeth very short, acutely pointed, apico-

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241

Fig. 101. Stenus nyoirin Naomi (A, Tsukechi, Gifu, B, C, E, F, Nomugi, Nagano; D, G, Kisokoma, Nagano). A,
9th and 10th terga of male; B, 9th ventrite of male; C, aedeagus; D, spermatheca; E, posterior part of 8th ventrite of male; F, expulsion hooks; G, posterior part of gonocoxite. Scale 1: 0.2 mm for A; Scale 2: 0.2 mm for
B–E, 0.1 mm for F, G.

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lateral setae very long; 10th tergum (Fig. 101A) rounded posteriorly. Aedeagal median lobe (Fig.
101C) elongate-subovoidal in basal 2/3, parallel-sided from near the apical 1/3 to the apicolateralcorners, gently rounded at apicolateral corner, acutely pointed at apex; apical sclerotized area
(Fig. 101C) very small, anteriorly with a small, pointed projection, and with a median longitudinal keel. Endophallic median bands (Fig. 101C) with basal bands fused, long, narrow; lateralbands (Fig. 101C) long, relatively thick; expulsion hooks (Fig. 101F) M-shaped, running almostin parallel, each slender, simply turning anteriorly, weakly broadened toward anterior tip; copulatory tube (Fig. 101C) with basal chamber elongate-ovoidal, main tube long, thick at base but ﬂagellar at the apical 2/3, twice moderately curved on its way. Parameres (Fig. 101C) each spatulate, with stem moderately thick; apical area very long, furnished densely with about 30 to 40
long setae along mesial margin.
Female: Eighth ventrite rounded posteriorly; gonocoxites (Fig. 101G) each hardly serrate
posteriorly, with apicolateral tooth short, pointed, apicolateral setae very long. Spermatheca (Fig.
101D) with capsule very small; RT-duct short, thin; duct thin at proximal part, thick at distal part,strongly coiled at the 1st turn; basal valve very short; basal duct long, thin.
Biology and ecology. S. nyoirin is distributed in the mountainous regions of Chubu district,Honshu. The beetles inhabit leaf litter in the natural forests.
Remarks. S. nyoirin is allied to S. vernicosus, but it is separable from the latter species by theaedeagal median lobe parallel-sided from near the apical 1/3 to the apicolateral corners (Fig.
101C), the endophallic expulsion hook simply turning anteriorly at the anterior tip (Fig. 101C),
and the spermatheca with its duct thinner, and its basal sclerotized duct much longer (Fig. 101D).
Etymology. The speciﬁc epithet of this species is derived from the “Nyoirin”, which is thename of a Bodhisattva.
Acknowledgements
We express our hearty thanks to Toshiya Hirowatari (Kyushu University, Fukuoka), Satoshi
Kamitani (Kyushu University, Fukuoka) and Akiko Saito (Natural History Museum and Institute,
Chiba) for loaning us the types specimens of several Stenus species. We sincerely thank Aleš
Smetana and Anthony Davies (Agriculture and Agrifood Canada, Ottawa) for exchanging theparatypes of some Stenus species for the present study, and also for informing us of the etymology of a Stenus name. We sincerely thank Liang Tang (Shanghai Normal University, Shanghai)
for sending us the photo of the paraglossae of S. ﬂammeus, and also for letting us know the new
information on his recent studies of the indubius-group. We sincerely thank Kwang-Sik Oh (Hannam University, Daejeon) for sending us the photos of the aedeagus of S. sulcifer. We sincerely
thank Ivan Löbl (Muséum dʼhistoire naturelle, Genève) for his constructive comments on a nearﬁnal version of the draft of our Japanese Steninae monograph Part 2. We sincerely thank Hiromu
Kamezawa (Kawagoe, Saitama) for helping us by taking the habitus photos of Stenus-species.
Our special thanks are due to the following entomologists who kindly gift or loan us thevaluable Stenus specimens for the present study: A. Amagasu (Mie), Shiho Arai (Arashiyama,
Saitama), Kaoru Haga (Saitama), Yasuhiko Hayashi (Kawanishi, Hyogo), Yasunori Hagino (Natural History Museum & Institute, Chiba), Yukihiko Hirano (Odawara, Kanagawa), Hideto
Hoshina (Fukui University, Fukui), Koichi Hosoda (Nirasaki, Yamanashi), Futoshi Ichikawa(Mie), Sho-Ichi Imasaka (Fukuoka), Noboru Ito (Kawanishi, Hyogo), Tateo Ito (Yahata, Kyoto),
Paweł Jałoszynski (University of Wrocław, Wrocław), Toshio Kishimoto (Museum of Natural &Environmental History, Shizuoka), Yoshinori Kaneko, Ivan Löbl (Muséum dʼhistoire naturelle,

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Genève), Isao Matoba (Yuasa, Wakayama), Munetoshi Maruyama (Kyushu University Museum,
Fukuoka), Takasuke Miyata (Kochi), Hisashi Ohishi (Kyoto), Ichiro Ohshio, Iwao Okamoto(Kure, Hiroshima), Masahiro Saito (Mikuni, Fukui), Masahiro Sakai (Ehime University, Matsuyama), Yasutoshi Shibata (Machida, Tokyo), Kohei Sawada (Takatsuki, Osaka), Yasutoshi Shibata (Machida, Tokyo), Yoshiharu Sugie (Tatsunokuchi, Ishikawa), Yasuaki Watanabe (Tokyo
University of Agriculture, Atsugi), Takashi Watanabe (Fujisawa, Kanagawa), Kenzo Yamagishi(Meijo University, Nagoya), Hideyuki Yokozeki (Yokkaichi, Mie), Masataka Yoshida (Tokushima).
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Corrigenda and Addenda to the Steninae of Japan Part 1
Corrigenda to the Steninae of Japan Part 1 (Naomi et al., 2017)
Page iv, for “Cover Illustration”, read “Cover Illustration: Stenus ﬂavidulus paederinus Champion”.
Page 19, Fig. 7, for “porch”, read “pouch”.
Page 20, line 9, for “Japanese species of the S. comma group to S. guttalis group of Steninae are revised”, read “Japanese
species of the Dianous and Stenus (S. comma group to S. guttalis group) of Steninae are revised”
Page 188, lines 31–32, for“Stenus nomurai Naomi, 1988c: 45.
Stenus mikado Hromádka, 1979a: Naomi & Puthz, 1994a: 218 (synonym of S. mikado).” read
“Stenus nomurai Naomi, 1988c: 45; Naomi & Puthz, 1994a: 218 (synonym of S. mikado).
Stenus mikado Hromádka, 1979a.”
Addenda to the Steninae of Japan Part 1 (Naomi et al., 2017)
Page 37, Type material examined. Paratypes of Dianous viridicatus: 2♂1♀ (cN), Ohdaigahara, Nara Pref., 25–26. vi.
1981, S. Naomi leg.
Pages 330–339. Add scale in each of Figs. 127 to 136, as follows: “Scale: 0.5 mm” for all Stenus species.
Page 321. Add the following paper after the paper of Clarke and Grebennikov (2009): “de Rougemont, G. M. 1985. In thefoots of H. G. Champion: new Dianous species from the Himalaya (Coleoptera, Staphylinidae). Entomologica
Basiliensia, 10: 123–144.

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Fig. 102. A, Stenus hayashii Puthz (Oomine, Nara); B, S. incommodus Puthz (Yawata, Kyoto); C, S. davidhulli
Naomi (Akazai, Hyogo); D, Stenus inbecillus Naomi (Renge, Niigata); E, S. bishamon Naomi (Tonomaru,
Tokushima); F, S. carura Naomi (Saijyo, Ehime); G, S. trispinosus Naomi & Nomura (Misaka, Yamanashi);H, S. nyorai Naomi (Abe, Yamanashi); I, S. kisomontanus Naomi, Nomura & Puthz sp. nov. (Kiso-komagatake, Nagano); J, S. scissilis Naomi, Nomura & Puthz sp. nov. (Kamisaka, Gifu); K, S. unicuspidatus
Naomi & Nomura (Oohira, Nagano); L, S. kasumi Naomi (Shibitsu, Gunma). Scale: 0.5 mm.

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Fig. 103. A, S. yatsugatakensis Naomi (Shirakoma, Nagano); B, S. sawadaiellus Naomi & Puthz (Ontake,
Nagano); C, Stenus uncinatus Naomi, Nomura & Puthz sp. nov. (Shinhotaka, Nagano); D, S. houou Naomi(Houou, Yamanashi); E, S. kumoma Naomi (Hayachine, Iwate); F, S. izanagi Naomi & Puthz (Kattadake,
Miyagi); G, S. brendelli Naomi (Jôyama, Fukuoka); H, S. ruricolaris Naomi (Tachibana, Fukuoka); I, S. clio
Naomi (Kamagadake, Mie); J, S. komonoensis Naomi (Gozaisho, Mie); K, S. anfractus Naomi (Kukizaki,Mie); L, S. hijiri Naomi (Norikuradake, Nagano). Scale: 0.5 mm.

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Fig. 104. A, S. maruyamai Naomi (Tanba, Yamanashi); B, S. oisami Naomi & Puthz (Ryogami, Saitama); C, Stenus biwa Hromádka (Towada, Aomori); D, S. bicara Naomi (Sawairi, Gunma); E, S. araiorum Naomi (Takao,
Tokyo); F, S. jurojin Naomi (Tsukiore, Ibaraki); G, S. tsukubamontis Naomi, Nomura & Kamezawa (Tsukuba,
Ibaraki); H, S. santira Naomi (Arakawa, Niigata); I, S. ellipsoides Naomi (Hosono, Fukushima); J, S. fulvivestis Naomi & Watanabe (Jinmuji, Kanagawa); K, S. basara Naomi (Mizugazuka, Shizuoka); L, S. asyura
Naomi (Tsukuba, Ibaraki). Scale: 0.5 mm.

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Fig. 105. A, S. hakonensis Naomi (Shiraito, Shizuoka); B, S. nogohakusanus Naomi, Nomura & Kamezawa(Nogo-Hakusan, Fukui); C, S. yukawai Naomi (Arano, Shizuoka); D, S. alesi Naomi (Udoyama, Shizuoka); E,
S. hannia Naomi (Chuzenji, Tochigi); F, S. naturalis Naomi & Watanabe (Kagami-daira, Gifu); G, S. zdenae
Hromádka (Kurofu, Gunma); H, S. bunraku Hromádka (Yuzawa, Niigata); I, S. haginoi Naomi (Shibitsu,
Gunma); J, S. oni Naomi (Konsei, Tochigi); K, S. triprotrudens Naomi & Watanabe (Ishikorobi-zawa,
Yamagata); L, S. dubitativus Puthz (Yuwan, Amami Is.). Scale: 0.5 mm.

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Fig. 106. A, Stenus autumnalis Naomi (Kotsu, Tokushima); B, S. unzenmontis Naomi & Puthz (Unzen, Nagasaki); C, S. inimitabilis Puthz (Odami, Ehime); D, S. siphonifer Naomi (Ohdaigahara, Nara); E, S. serratus
Naomi (Setogaro, Fukushima); F, S. sadoensis Naomi (Ootaki, Sado Is.); G, S. subserratus Naomi (Shibitsu,
Gunma); H, S. takane Naomi (Mayogatai, Aomori); I, S. unicoloratus Naomi & Puthz (Higashi-ozana, Fukushima); J, S. tohokuensis Naomi & Puthz (Jyuniko, Aomori); K, S. campaniformis Naomi, Nomura & Puthz
sp. nov. (Oguni, Yamagata); L, S. naomii Puthz (Mimuro, Hyogo). Scale: 0.5 mm.

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Fig. 107. A, Stenus tuberascens Naomi, Nomura & Puthz sp. nov. (Maizuru, Kyoto); B, S. acerrimus Naomi(Hira, Shiga); S. cucumeroides Naomi & Puthz (Utatsu, Ishikawa); D, S. unagi Hromádka (Katsuragi,
Wakayama); E, S. fugu Hromádka (Inamura, Nara); F, S. ukon Naomi & Puthz (Sekigahara, Gifu); G, S.
kyushuensis Naomi & Puthz (Fukuchi, Fukuoka); H, S. tanuki Hromádka (Kongo, Nara); I, S. hypovelox
Naomi & Puthz (Oku-dogo, Ehime); J, S. sawadai Hromádka (Hanase, Kyoto); K, S. kishimotoi Naomi &Puthz (Kukizaki, Mie); L, S. yokozekii Naomi (Sugari, Mie). Scale: 0.5 mm.

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Fig. 108. A, Stenus tateoi Naomi (Komono, Mie); B, S. ohishii Naomi (Tsurugi, Tokushima); C, S. fusciceps
Naomi (Muroto, Kochi); D, S. indubius Sharp (Nakakawane, Shizuoka); E, S. kiyosumiensis Naomi & Takeda(Yanagisawa, Yamanashi); F, S. punctifer Naomi (Nagodake, Okinawa Is.); G, S. tokunis Naomi (Yonama,Toku Is.); H, S. amamiensis Naomi (Hatsuno, Amami Is.); I, S. nomuraianus Puthz (Jeong-Lyeonchi, Korea);J, S. fusciformis Oh & Cho (Kyongeyomeon, Korea); K, S. hewenjiae Tang & Li (Sichuan, China); L, S. shibatai Puthz (Taichung, Taiwan). Scale: 0.5 mm.

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Fig. 109. A, Stenus yamabusi Naomi & Ito (Funato, Kochi); B, S. uedai Naomi (Keisoku, Tokushima); C, S.
angusticulus Naomi, Nomura & Puthz sp. nov. (Ishizuchi, Ehime); D, S. yashiro Naomi & Puthz (Kyogatake,Saga); E, S. domburi Hromádka (Takamaru, Tokushima); F, S. sakaii Naomi & Puthz (Odami, Ehime); G, S.
sugiei Naomi (Nabetani, Ishikawa); H, S. caesariatus Naomi & Ito (Akazai, Hyogo); I, S. kanzeon Naomi(Fukumizu, Ishikawa); J, S. sawadaianus Hromádka (Ashiu, Kyoto; K, S. vernicosus Naomi & Nomura(Kenashi, Tottori); L, S. nyoirin Naomi (Ohshirakawa, Nagano). Scale: 0.5 mm.

National Museum of Nature and Science Monographs(Nos. 1–35 were published as “National Science Museum Monographs)
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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.

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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.
Deep-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.
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