Revision of the genus Georissus (Coleoptera, Hydrophiloidea, Georissidae) of Japan

. Japanese species of the genus Georissus are revised. Seven species, including two new, G . ( Neogeorissus ) takahashii sp. nov. and G . ( Ne .) satoi sp. nov. are recognized. Georissus ( Neogeorissus ) sakaii Satô, 1972 and G . ( Ne .) katsuoi Nakane, 1995 are synonymized with G . ( Ne .) japonicus Satô, 1972. Based on the type series and additional specimens, three subgenera and seven species are (re) described with SEM micrographs of the external morphology and ﬁ gures of male and female genitalia. The terminology of some structures of the head and the pronotum are rede ﬁ ned for convenience of taxonomy. A key to the Japanese species is also given. Yasuda K. & Yoshitomi H. 2022. Revision of the genus Georissus (Coleoptera, Hydrophiloidea, Georissidae) of Japan. European Journal of Taxonomy 817: 111–142. https://doi.org/10.5852/ejt.2022.817.1767


Material and methods
Dry specimens were prepared by soaking the whole body in hot water for about one hour. They were then soaked in a hot solution of neutral detergent for a few hours to remove dirt and sand from the specimens. Photographs were taken under a Leica MZ95 using a microscopy camera system (Nikon DS-Fil-L2) and combined using the Combine ZP (Alan Hadley, UK) automontage software. Some structures (Figs 1, 5-8) were observed using a SEM (JSM-5600LV) and images were enhanced using Adobe ® Photoshop CC. The mouth parts and genitalia were removed with forceps under a Leica MZ95 stereo microscope.
Terminology follows mainly Fikáček & Falamarzi (2010), Lawrence et al. (2011), and Archangelsky et al. (2016), and the structures of the head and pronotum are redefi ned as in Fig. 1. ELYTRA. Provided with ten punctate rows. All or alternate intervals slightly to highly raised. Hind wings well developed or absent in some species.
Key to the species of the genus Georissus from Japan

Remarks
This subgenus is distinguished by the following characteristics: lacking sdn (present in Neogeorissus); posterior portion of pronotal disc smooth, with median longitudinal groove (uneven, with granules or depression in other subgenera); elytral interstices smooth, not highly elevated (in contrast to uneven, granulated in other subgenera); parameres provided with small dense spines on the anterior portion (even in other subgenera).

Diagnosis
This species resembles palearctic species G. crenulatus, and is distinguished from the latter by the presence of shallow longitudinal groove on posterior portion of pronotum (lacking in G. crenulatus). Redescription COLORATION ( Fig. 2A). Black, weakly shining. HEAD (Fig. 6A). Clypeus uneven, provided with large granules on anterior portion; slr consisted of carinae and granules, granulation of anterior portion distinct, in contrast to posterior portion indistinct. Frons provided with scattered granules. Longitudinal groove distinct, wide, and surrounded by granules; lsa narrow, linear. PRONOTUM (Fig. 7A). Relatively small, widest at posterior ⅓; anterior portion sparsely provided with short grooves and small foveae; anterior margin smooth; smlg deep, with short longitudinal grooves; posterior portion with small granules and shallow longitudinal grooves; lateral margin except anterior portion regularly bearing granules; slb indistinct, densely covered with large granules; pg short, subobsolete. ELYTRA (Fig. 5A). Humeral bulges distinct. All intervals slightly elevated and provided regularly with punctures. Lateral ridges indistinct, but with row of small granules. Hind wings well developed. ABDOMEN (Fig. 8A). Lateral margin of ventrites gradually narrowing posteriorly, especially ventrites 1-2 strongly narrowing. Granules of ventrite 1 large, relatively dense; vt large. Granulation of ventrites 2-4 indistinct, 5 distinct and dense. MALE GENITALIA (Fig. 9A). Aedeagus 0.40 mm long. Parameres slightly shorter than phallobase; basal portions combined as wide as anterior portion of phallobase; lateral margins slightly bulbous at anterior portion; internal margins asymmetrical; anterior portion with short setae densely. Median lobe shorter than parameres, gradually narrowing apically; basal struts short. Phallobase about 1.8 times as long as wide, widening posteriorly; posterior portion with large basal foramen. FEMALE GENITALIA (Fig. 10A). Latero-tergites 8 forming acute angle; apex strongly incurved. Spines of gonostylus long.

Biological notes
This species is common in Hokkaido and inhabits wet sandy river beds in summer (Sharp 1888;Miwa 1937).

Diagnosis
This species resembles the palearctic species G. crenulatus, and is distinguished from the latter by the granulation of the frons: G. babai has large granules on the median and lateral portions whereas G. crenulatus only on the median portion. Redescription COLORATION (Fig. 2B). Black to dark reddish brown, weakly shining. HEAD (Fig. 6B). Clypeus uneven, provided with bearing large granules on anterior portion extensively; slr consisted of large granules. Frons provided with large granules along the anterior to lateral margin; longitudinal groove distinct and narrow, surrounded granules only anterior portion; lsa relatively wide, slightly curving inside. PRONOTUM (Fig. 7B). Relatively large, widest at the posterior third. Anterior portion provided with short grooves and small deep foveae; anterior margin slightly crenelated; smlg shallow, with short longitudinal grooves. Posterior portion smooth, lacking granules; longitudinal groove indistinct. Lateral margin except anterior portion regularly bearing granules; slb indistinct, sparsely with large granules; pg relatively long and narrow.

Biological notes
This species was collected using a pitfall trap at a sandy place with Imperata cylindrica (L.) Raeusch. (Poaceae) in Shizuoka Prefecture (Tabira & Ishikawa 2011). But there have been no additional records from Niigata Prefecture, the type locality of this species.

Diagnosis
This species is easily distinguished from other Japanese species of Georissus by the granulated pronotum and shape of male aedeagus; shape elongated and narrow, phallobase widening. This species is distinguished from Georissus biroi described from Papua New Guinea by the carinae of frons; G. granulosus has transverse carinae, in contrast to their absence in G. biroi. Redescription COLORATION (Fig. 2C). Black, mat, legs dark reddish brown. HEAD (Fig. 6C). Clypeus uneven, provided with foveae and carinae throughout; slr, consisted of granules, connecting to smb at median portion; smb nonsequential, connecting each other, forming oblong oval; lsa connecting each other, forming U-shape. PRONOTUM (Fig. 7C). Relatively large, widest at the middle. Pronotal disc provided with granules densely. Anterior portion provided with indistinct granules extensively; anterior margin smooth, not crenelated; smlg distinct, with longitudinal row of pits. Posterior portion slightly convex than anterior potion, bearing granulation regularly; lateral margins protruding; slb developed; pg indistinct, short.
FEMALE GENITALIA. Not examined.

Biological notes
This species inhabits tidal fl ats that are submerged at high tide (Akita 2008). The holotype was collected at light (Satô 1981).

Redescription
HEAD. Clypeus uneven, with a line of low granules along the anterior margin. Surface of clypeus provided with scattered granules; slr long, reaching to mid-length of frons. Frons provided with granules and some foveae on median portion; lsa distinct, connecting each other, forming U-shape. Mandibles (Fig. 4L) relatively large; median lateral margin curving strongly, apex unidentate or bidentate, mola well developed. Antennae (Fig. 4O) relatively long; antennomere 4 thin, more than twice as long as antennomere 3; pubescence of club long. Labrum (Fig. 4F) not protruding anterior, spines on anterior margin distinct. Apical segment of labial palpi (Fig. 4I) oblong oval, with long spines densely. Galea (Fig. 4C) densely bearing long setae.
PRONOTUM. Half circular, anterior portion slightly projecting to lateral. Median longitudinal groove reaching at the middle of pronotum. First half of pronotal disc bearing foveae and grooves irregularly, the second half of disc with foveae, especially distinct on a central one (cd) and two oblique large ones just before the posterior margin (sdp). Pronotal sides have dentation at subbasal portion (sdn). Posterior margin provided with granules, bearing grooves along the posterior margins.
ELYTRA. Provided with rows of granules. Puncture distinct. Elytral interstices raised and formed distinct carinae in some species. Humeral bulges distinct, with granules. Lateral ridges on each elytron developed, with granules.
FEMALE GENITALIA. Ovipositor relatively elongate to lateral portion. Two long setae of gonostylus long to short. Spermatheca oblong oval, curving inside, slightly sclerotized. Bursal sclerite slightly asymmetrical, slightly to highly sclerotized.

Diagnosis
This species is distinguished from other Japanese Neogeorissus species by the combination of following characteristics; distinct granulation of pronotum and elytra; median lobe shorter than paramere (in contrast to median lobe longer than paramere in other Japanese species of Neogeorissus). Redescription COLORATION (Fig. 2D). Black to dark brown, matt. Body surface often covered with grayish substance. HEAD (Fig. 6D). Clypeus uneven, provided with large granules sparsely; slr consisted of granules, reaching to posterior third of frons, posteriorly connected to smb by an arc of sparsely arranged granules and formed a pair of half-rounded foveae; smb consisted of tubercles and granules, anterior portion projecting to laterally; lsa with a shallow groove along the posterior margin. PRONOTUM (Fig. 7D). Relatively large, widest at the middle. Anterior portion provided with granules densely; smlg relatively wide, granulation dense, with longitudinal row of sparse pits. Posterior portion somewhat convex than anterior portion; cd rhomboid, surrounded by granules; sdp oblong oval, larger than cd, surrounded by granules; slb developed, with distinct granules; pg short and narrow, not reaching median portion of sdp; sdn developed, having a few teeth.

Holotype of G. (Ne.) japonicus
ELYTRA. Humeral bulges distinct. All intervals slightly elevated, provided with distinct lows of granules. Elytral punctures distinct. Lateral ridges on each elytron highly elevate, bearing distinct granules. Hind wings fully developed. ABDOMEN (Fig. 8D). Lateral margin of ventrites uniformly narrowing posterior. Granules of ventrite 1 large and dense. Granulation of ventrites 2-4 indistinct, ventrite 5 distinct and sparse. MALE GENITALIA (Fig. 9D). Aedeagus 0.30 mm long. Parameres shorter than phallobase, their basal portions combined as wide as anterior portion of phallobase; lateral margins bulbous at median portion; internal margins straight. Median lobe shorter than parameres, subparallel-sided, slightly angular at apex; basal struts short. Phallobase about 2.5 times as long as wide, sides paralleled: posterior portion with large basal foramen. FEMALE GENITALIA. Latero-tergites 8 forming acute angle (Fig. 10C); apex strongly incurved. Setae of gonostylus short. Spermatheca (Fig. 11E) curved oval, narrowing at apical portion. Bursal sclerite (Fig. 11A) large and asymmetrical, feebly sclerotized. Satô (1972) mentioned that Georissus (Neogeorissus) sakaii was closely related to G. japonicus and distinguished by granules and foveae on body surface. Subsequently, Nakane (1995) described Georissus (Neogeorissus) katsuoi as a new species without comparison with the related species G. sakaii and G. japonicus. Both species were described based on only holotypes, and there have been no additional records until now. After a detailed comparison of holotype and additional specimens of the above three species, we conclude that they are the same species.

Biological notes
This species was collected from coastal sandy beaches (Shizuoka, Tokushima), a river bank (Iwata & Iwata 2012, in Saitama by pit fall trap), or the shores of ponds (Niigata, Fukuoka).
Redescription COLORATION (Fig. 2E). Black, weakly shining, legs dark reddish brown. Body surface often covered with greyish substance. HEAD (Fig. 6E). Clypeus relatively smooth, provided with a few large granules on median portion; slr consisted of carinae and indistinct granules, reaching to mid-length of frons, posteriorly connected to smb by an arc of sparsely arranged large granules and formed a pair of half-rounded foveae; smb V-shaped and not connected each other, with indistinct granules; lsa with a few small granules at lateral portion. PRONOTUM (Fig. 7E). Relatively small, widest at the middle. Anterior portion provided with granules and pits densely; anterior margin crenellated; smlg shallow and narrow, with distinct longitudinal row of pits. Posterior portion somewhat convex than anterior portion; cd circular and relatively small, surrounded by many granules; sdp oblong oval to rectangle, larger than cd, with some granules; slb well developed, provided with distinct granules at posterior portion; pg short and narrow, not reaching median portion of sdp; sdn poorly developed, provided with a few teeth.

Biological notes
This is a common species collected in all seasons. It inhabits wet sandy river beds and is often observed under rocks (Fig. 12B). This species was also collected using pitfall traps or light traps (Arai 2006;Iwata & Iwata 2012).

Etymology
This species name is dedicated to Dr Keiichi Takahashi, the collector of the type series. Description COLORATION (Fig. 2F). Light reddish brown, matt. Body surface often covered with greyish to white substance. HEAD ( Fig. 6G-H). Clypeus uneven, bearing a few large granules sparsely on median portion; slr consisted of granules, anterior granules distinct, but posterior ones indistinct; reaching to posterior third of frons, posteriorly connected to smb by an arc of sparsely arranged granules and formed a pair of rounded foveae; smb consisted of tubercles and granules; lsa with small indistinct granules sparsely.
PRONOTUM (Fig. 7G-H). Relatively small, widest in the anterior third. Anterior portion provided with granules and pits sparsely; anterior margin slightly crenellated; smlg relatively narrow, provided with longitudinal row of small pits. Posterior portion strongly convex than anterior portion; cd rhomboid and large, with granules on only lateral portion; sdp oblong oval, larger than cd, with a few granules; slb poorly developed, with indistinct granules; pg wide and triangular, not reaching median portion of sdp; sdn well developed, having a few teeth.
MALE GENITALIA (Fig. 9F-G). Aedeagus 0.32 mm long. Parameres shorter than phallobase, their basal portions combined as wide as anterior portion of phallobase; lateral margins bulbous at basal portion. Median lobe longer than parameres, widening basally, obtuse at apex; basal struts long. Phallobase about 2.2 times as long as wide, subparallel-sided; posterior portion with large basal foramen.

Biological notes
This species was collected under rocks near a river (Y. Hisasue pers. com.). Specimens from Kochi Prefecture were collected using a car net trap.

Etymology
This species name is dedicated to the late Dr Masataka Satô, who made a great contribution to entomology in Japan.

Material examined
Holotype JAPAN -Okinawa: Ishigaki-jima • 1ex.; Yonehara; 20 Oct. 1998, K. Takahashi leg.; EUMJ.   Description COLORATION (Fig. 2G). Dark red, weakly shining. Body surface often covered with white substance. HEAD (Fig. 6I). Clypeus uneven, bearing large granules in median portion, and small granules; slr consisted of granules, granulation of anterior portion dense, in contrast to posterior portion sparse; smb consisted of granules and large tubercles, narrowing posteriorly; lsa with small indistinct granules at anterior portion. PRONOTUM (Fig. 7I). Relatively large, widest at the middle; anterior margin crenellated; smlg relatively wide, granulation sparse, bearing a few small pits. The fi rst half of anterior portion provided with granules densely, in contrast to the last half bearing pits sparsely. Posterior portion strongly convex than anterior potion; cd rhomboid and large, surrounded by granules; sdp oblong oval, larger than cd, surrounded by granules sparsely; slr strongly developed, with large granules; pg relatively wide and short, not reaching median portion of sdp; sdn well developed, provided with many teeth. ELYTRA. Widest at the middle, slightly wider than pronotum in basal margin; suture and all intervals slightly elevate, regularly bearing distinct granules; granulation projecting and forming serration; punctures distinct and regular. Humeral bulges indistinct. Lateral ridges on each elytron highly elevate, bearing distinct granules. Hind wings not developed. ABDOMEN (Fig. 8I). Lateral margin of ventrites uniformly narrowing posterior. Ventrite 1 with large and sparse granules; serial small bulges arising at anterior margin of ventrite 1 and forming ridge. Granulation of ventrites 2-5 distinct and sparse. MALE GENITALIA (Fig. 9H). Aedeagus 0.35 mm long. Parameres shorter than phallobase, their basal portions combined as wide as anterior portion of phallobase; lateral margins slightly curved at median portion; internal margins slightly bulbous at basal portion. Median lobe longer than parameres, widening basally, angular at apex; basal struts long. Phallobase about 2.5 times as long as wide, slightly widening posteriorly; posterior portion with large basal foramen. FEMALE GENITALIA. Latero-tergites 8 (Fig. 10F) forming obtuse angle; apex strongly incurved. Setae of gonostylus long. Spermatheca (Fig. 11H) elongated oval, constricted at basal portion. Bursal sclerite (Fig. 11D) large and almost symmetrical, slightly sclerotized.

Biological notes
This species was collected from leaf litter (T. Yoshida pers. comm.).

Discussion
In this study, we added two new species from Japan. These species were found in southwest Japan, where it is expected that additional species will be found, particularly inhabitants of leaf litter in wet environments like as G. satoi sp. nov. Some specimens thought to belong to an undescribed taxon were obtained from Amami-Oshima Island, but we do not describe them in this study because there are few specimens, and in poor condition.
One species, G. formosanus Kono, 1936, has been described from Taiwan, but the type specimen could not be examined and was not included in this study. According to the original description (Kono 1936), this species is considered to be closely related to G. (Ne.) japonicus.