Discovery of a troglomorphic trechine beetle from the Ryukyu Archipelago, Southwestern Japan (Coleoptera: Carabidae: Trechinae) Author Sugaya, Kazuki Bioindicator Co., Ltd., Nikkô-Kagurazaka Building, 18 Iwato-chô, Shinjuku, Tokyo, 162 - 0832 Japan Author Kakizoe, Showtaro Center for Collections, National Museum of Nature and Science, Amakubo Author Ooka, Sohei Nanto Co., Ltd., Maekawa 1336, Tamagusuku, Nanjo, Okinawa, 901 - 0616 Japan Author Tamura, Hisao - Author Sone, Shinzaburo Japan Plant Protection Association, Nakazato text Acta Entomologica Musei Nationalis Pragae 2023 2023-12-11 63 2 323 340 http://dx.doi.org/10.37520/aemnp.2023.020 journal article 10.37520/aemnp.2023.020 1804-6487 10621601 996CCDF0-04C6-47A5-AAAA-CCA93ECD3BC2 Ryukyuaphaenops gen. nov. Japanese name: リπ̚キπ̚7̐±fl̽yṽŧõiì^̐ȇ Type species. Ryukyuaphaenops pulcherrimus sp. nov. , here designated. Diagnosis. Ryukyuaphaenops gen. nov. is distinguished from all known genera of Trechina in the world by the following combination of characteristics: 1) aphaenopsian facies; 2) both dorsal and ventral body surfaces sparsely covered with microscopic hairs ( Fig. 24 ); 3) right mandible seemingly bidentate though actually tridentate, due to middle tooth frequently absent ( Figs 4 , 5b ); 4) mentum fused with submentum; 5) submentum multisetose; 6) labial palpomere 2 quadrisetose; 7) maxillary palpi glabrous though palpomere 2 unisetose subapically, palpomere 3 longer than palpomere 4; 8) prothorax barrel-shaped, with notopleural suture completely invisible from above ( Fig. 19b ), front and hind angles effaced; 9) scutellum distinct; 10) elytral basal transverse furrow absent; 11) elytral lateral margins ciliated ( Fig. 20a ); 12) elytral bases distinctly depressed; 13) four pores of humeral set not ranged equidistantly and adjoining marginal gutter except for 3rd and 4th pores, 1st pore isolated anteriad from posterior pores, 2nd and 3rd pores close to each other, and 4th pore widely isolated posteriad from first three pores ( Figs 4 , 20a, 20b ); each two pores of middle and apical sets distant from marginal gutter and isolated from other sets, close to each other in the former, while well distant from each other in the latter ( Figs 4 , 21 ); 14) abdominal sternites 3 and 4 completely fused together; 15) protibiae wholly pubescent and not externally grooved; 16) protarsomere 1 not longer than protarsomeres 2–4 combined; 17) protarsomeres 1 and 2 of male dilated, inwardly denticulated at apices, and furnished beneath with adhesive appendages ( Fig. 10 ); 18) median lobe of male genitalia with simple apical lobe neither reflexed dorsad nor bent ventrad; 19) internal sac without sclerotized teeth patches but with anisotopic copulatory piece; 20) styles elongate, with long setae at apices; and 21) female genitalia with distinct spermathecal complex not on common oviduct but on bursa copulatrix ( Fig. 15 ), gonocoxite 1 almost glabrous. Among all known genera of Trechina , Ryukyuaphaenops gen. nov. shows a close resemblance to some Chinese aphaenopsian genera, in particularly Boreaphaenops Uéno, 2002 and Yanzaphaenops Uéno, 2008 by sharing the following characteristics: 1) body surface sparsely covered with microscopic hairs; 2) elongated head with wide neck; 3) mentum fused with submentum; 4) pronotum barrel-shaped with incomplete lateral borders, basal area pre-pedunculated, front and hind angles degenerated; 5) elytral lateral margins ciliated; 6) humeral set of marginal umbilicate pores not aggregated; 7) protibiae wholly pubescent and not externally grooved; 8) protarsomere 1 not longer than protarsomeres 2–4 combined; 9) protarsomeres 1 and 2 modified in male; and 10) male genitalia with elongated aedeagus and styles, and anisotopic copulatory piece. However, Ryukyuaphaenops gen. nov. can be clearly distinguished from the above two genera as follows: 1) labial palpomere 2 quadrisetose [bisetose in the two genera]; 2) maxillary palpomere 2 unisetose, palpomere 3 longer than palpomere 4 [palpomere 2 completely glabrous in the two genera; palpomere 3 shorter than palpomere 4 in Boreaphaenops , almost as long as palpomere 4 in Yanzaphaenops ]; 3) elytral setiferous dorsal pores on stria 3 composed of two pores [three pores in Boreaphaenops , four pores in Yanzaphaenops ]; 4) abdominal sternites 3 and 4 completely fused together [not fused in the two genera]; and 5) female genitalia with distinct spermathecal complex on bursa copulatrix [spermathecal complex unrecognizable in the two genera]. In addition to the above, Ryukyuaphaenops gen. nov. also differs from Boreaphaenops in the first three pores of the humeral set of marginal umbilicate pores not ranged equidistantly and the aedeagus not reflexed dorsad, and from Yanzaphaenops in the 1st pore of the humeral set of marginal umbilicate pores adjoining marginal gutter. Incidentally, in Yanzaphaenops , it was found that the first three pores of the humeral umbilicate set are not ranged equidistantly, and the 1st pore is removed inward from marginal gutter, based on our re-examination of the type series, although it was originally described with the first three pores ranged equidistantly and adjoining marginal gutter (UḖNO 2005, 2010). In addition, Boreaphaenops liyuani Tian & He, 2020 significantly differs from the type species, B . angustus Uéno, 2002 , in the generically important characteristics, including the four pores of the humeral set of marginal umbilicate pores ranged equidistantly, and elytral lateral borders not ciliated ( TIAN & HE 2020 ). Therefore, Ryukyuaphaenops gen. nov. is easily distinguished from B . liyuani as well. Description. Medium-sized Trechina with aphaenopsian facies; apterous and depigmented; body surface sparsely covered with very minute microscopical hairs. Head elongated subquadrate, gradually narrowing posteriad with wide neck; dorsum feebly convex; frontal furrows absent posteriorly; two pairs of supraorbital pores present; ventral surface of genae ( Figs 18b, 18c ) bearing pair of long hairs before neck constriction; eyes completely missing; clypeus quadrisetose. Labrum sextisetose. Mandibles long and slender, falcate. Right mandible visually bidentate to tridentate, composed of well-developed premolar and wide retinaculum; retinaculum bidentate, though proximal tooth frequently missing while distal one always developed. Left mandible bidentate, with two partially overlapping undeveloped teeth on dorsal and ventral sides. Mentum bisetose and fused with multisetose submentum; ligula trapezoidal in apical part, with two long setae in middle of truncated portion, and three lateral setae on each oblique part; paraglossae elongate, moderately arcuate inwardly, extending much beyond ligula, with minute hairs along inner sides; palps elongate and glabrous, but with labial palpomere 2 quadrisetose, two on inner and outer margins, respectively, and with maxillary palpomere 2 unisetose on inner margin subapically; penultimate palpomere longer than apical one in labium and maxillae, respectively.Antennae exceedingly elongated filiform, longer in male than female, wholly pubescent except on basal half of segment 1. Fig. 3. Habitus of Ryukyuaphaenops pulcherrimus gen. & sp. nov., holotype male (KSES00004), dorsal (a) and lateral (b) views. Prothorax hardly tumid laterad. Pronotum barrel-shaped; dorsum moderately convex; median line distinct, not reaching apical nor basal margins; apical transverse impression distinct though superficial, with longitudinal fine wrinkles; basal transverse impression ( Figs 4 , 19a, 19b ) distinct, not continuous and merging on each side into basal fovea; sides ( Figs 19a, 19b ) not ciliated, incompletely and very finely bordered, and deflexed ventrad before anterior latero-marginal pore; marginal gutters vestigial; both apical and basal margins not bordered entirely; basal margin ( Figs 3a , 4 , 19a, 19b ) almost straight or feebly emarginated in middle, obliquely rounded at just inside of hind angles; front angles effaced; hind angles ( Figs 19a, 19b ) never produced, subrectangular or entirely rounded. Propleura ( Figs 4 , 19a, 19b ) almost invisible from above; notopleural sutures ( Figs 4 , 19a, 19b ) completely invisible from above. Scutellum distinct. Elytra fused together, elongated pyriform; basal peduncle without transverse furrow; dorsum convex though basal area longitudinally and obliquely depressed except for scutellar area; sides narrowly bordered throughout and very finely ciliated; marginal gutters distinct; stria 1 ( Figs 4 , 20b ) adjoining elytral suture except for basal area; basal pore present; two setiferous dorsal pores present on stria 3; preapical pore located at apical anastomosis of striae 2 and 3; two apical pores present; marginal umbilicate pores not aggregated; four pores of humeral set of marginal umbilicate pores not ranged equidistantly and adjoining marginal gutter except for 3rd and 4th pores, 1st pore isolated anteriad from posterior two pores, 2nd and 3rd pores close to each other, and 4th pore widely isolated posteriad from first three pores; two pores of middle set of marginal umbilicate pores close to each other, both isolated from humeral set and widely distant from marginal gutter, 1st pore more removed inward from marginal gutter than the 2nd pore; two pores of apical set of marginal umbilicate pores well distant from each other, isolated from middle set, 1st pore widely distant from marginal gutter while 2nd pore not so distant. Abdominal sternites 3 and 4 completely fused together, suture between them completely absent; sternites 4–6 each bearing pair of paramedian setae near posterior margin; sternite 7 bisetose in male, quadrisetose in female. Legs exceedingly long; protibiae wholly pubescent and not externally grooved; tarsomeres 4 with long hyaline ventral apophysis in pro- and mesotarsi; in male,protarsomeres 1 and 2 dilated, inwardly denticulate at apices, and furnished beneath with adhesive appendages. Male genital organ small and slightly sclerotized; median lobe elongated tubular, gradually tapered toward apex; apical lobe almost straight, with simple extremity; sagittal aileron distinct. Internal sac without sclerotized teeth patches; copulatory piece anisotopic and spatulate. Styles elongate; left style obviously more elongate than right one, each usually bearing four long setae at apex. Genital segment devoid of distinct basal peduncle. Female genital organ with distinct spermathecal complex on dorsal surface of bursa copulatrix near its junction with vagina. Gonocoxite 1 short, pick-shaped and almost glabrous, with a few short apical fringe setae (afs) along apical margin ventrally, two elongated apico-medial setae (ams) on apico-internal corner dorsally; gonocoxite 2 subconical, with two long dorsal ensiform setae (des) proximally, two apical nematiform setae (ans) preapico- -ventrally. Fig. 4. Chaetotaxy of Ryukyuaphaenops pulcherrimus gen. & sp. nov., holotype (KSES00004), dorsal (a) and dorso-lateral (b) views. Etymology. A combination of “Ryukyu” and “ Aphaenops ”. “Ryukyu [ ñṉ ]” refers to the range of the new trechine beetle. Aphaenops Bonvouioir, 1862 is a generic name of the famous Pyrenean trechine beetle with a strongly developed troglomorphism and is also traditionally used as root of the generic name of other strongly troglomorphic (aphaenopsian) trechines. Gender is masculine. Remarks. Though the direction of apical striole has been traditionally considered important to the trechine taxonomy, we do not use this character in generic diagnosis of Ryukyuaphaenops gen. nov. , because the character has been recently reported to be unstable in several genera and/or species (UḖNO 1999, BELOUSOV & KABAK 2003 ). In fact, the character state of the type species of Ryukyuaphaenops gen. nov. is unstable, and in many cases, the direction of apical striole is undetermined, due to its degeneration.