Revision of the intertidal rove beetle genus Bryothinusa from Japan (Coleoptera: Staphylinidae: Aleocharinae) Author Liu, Tian-tian Entomological Laboratory, Graduate School of Bioresource and Bioenvironmental Sciences, Kyushu University, Fukuoka, 819 - 0395, Japan & The Kyushu University Museum, Hakozaki Author Ono, Hiroki Sounan, Minami-ku, Sagamihara-shi, Kanagawa, 252 - 0312, Japan Author Maruyama, Munetoshi The Kyushu University Museum, Hakozaki dendrolasius@gmail.com text Acta Entomologica Musei Nationalis Pragae 2021 Acta. Ent. Mus. Natl. Pragae 2021-05-07 61 1 163 201 http://dx.doi.org/10.37520/aemnp.2021.009 journal article 10.37520/aemnp.2021.009 1804-6487 5037330 27EA8466-6B29-40F4-8236-DD49061C523B Bryothinusa hokkaidensis sp. nov. ( Figs 1I ; 2I ; 11 ; 21C ; 22 ) (Japanese name: Hokkai-nagisa-hanekakushi) Type material. Hඈඅඈඍඒඉൾ: J, JAPAN : Hඈκκൺංൽත: Shunkunitai, 43.2725 N , 145.472 E , Nemuro-shi, Hokkaidô , 11.ix.1999 , M. Maruyama ( KUM ). Pൺ*©ൺඍඒඉൾඌ: Hඈκκൺංൽත: 3 JJ 4 ♀♀ , 96 unsexed spec., same data as holotype ( KUM , NMPC , BMNH ); 1 ♀ , 4 unsexed spec., Usu-chô, Date-shi, Hokkaidô , 12.iv.2020 ,Y.Tasaku ( KUM ). KඒǕඌΗǕ: 1♀ , Nokono-shima, Fukuoka-shi, Fukuoka-ken, 21.iv.2018 , T .Hashizume ( KUM ). Fig. 10. Bryothinusa constricta sp. nov. A – labrum; B – mandible, dorsal view; C – lacinia, dorsal view; D – labium; E – mentum; F – male sternite VIII; G – female sternite VIII; H – median lobe, ventral view; I – median lobe, lateral view; J – paramere; K – spermatheca. Scale bars: 0.1 mm. Fig. 11. Bryothinusa hokkaidensis sp. nov. A – labrum; B – mandible, dorsal view; C – lacinia, dorsal view; D – labium; E – mentum; F – male sternite VIII; G – female sternite VIII; H – median lobe, ventral view; I – median lobe, lateral view; J – paramere; K – spermatheca. Scale bars: 0.1 mm. Description. Body ( Fig. 1I ) small, about 1.8–2.2 mm in length, covered with minute setae. Abdomen almost dark brown and darker than head and pronotum; elytra lighter than pronotum; legs yellowish brown; antenna brown, similar coloured with mouthparts and legs, lightly paler than body colour. Head evenly oval, wider than long, shorter than pronotum and elytra; eyes ( Fig. 2I ) large, setae present between about 22–25 facets, slightly longer than tempora length; antenna brown, equals to total length of head and pronotum; segment I as long as II, almost 2.3 times longer than III, and as long as XI; antennal segments III–IV subquadrate, V–X almost same length and wider than long. Mouthparts ( Figs 11A–E ) with distribution of labral setae as in Figure 11A , with large and thick spiniform seta at antero-laterally; mandibles ( Fig. 11B ) elongate triangle, asymmetrical, right mandible with some median tooth and irregular; median tooth longer than 1/4 of mandibles; left mandible without tooth, blunt at apex; maxilla with apical margin of lacinia ( Fig. 11C ) at obtuse angle; at tip with two spines very small and not closely interdigitating; 2–3 setae on inner margin of lacinia; labial palpus ( Fig. 11D ) with most setae located basally, small ligula; mentum ( Fig. 11E ) with antero-lateral angles prolonged into spinose processes; anterior margin deeply truncate; small “v seta” far away from apical setae. Pronotum shorter than elytra, wider than head. Elytra subquadrate but wider than long, slightly narrower than pronotum; hind wings present but very small, apparently flightless. Male abdominal sternite VIII ( Fig. 11F ) with posterior margin slightly serrate. Median lobe of aedeagus as in Figures 11H, I ; paramere ( Fig. 11J ) elongate. Female abdominal sternite VIII ( Fig. 11G ) slightly serrate similar male on posterior margin. Spermatheca ( Fig. 11K ) simplified in shape, about 1 time coiled near base. Measurements. BL 1.80–2.20, FBL 0.90–1.00, HL 0.25– 0.30, HW 0.38–0.40, PL 0.33–0.35, PW 0.40–0.43, EL 0.35–0.38, EW 0.35–0.40, HTL 0.25–0.35, AL 0.60–0.68, AS-I 0.10–0.11, AS-II 0.09–0.10, AS-III 0.04–0.05. Differential diagnosis. In general appearance, the species is similar to B. fulvipennis sp. nov. and B. itsuroi sp. nov. but distinguished from them by the combination of the following character states: the body colour (especially head and pronotum colour) and the spermathecal shape. Etymology. Toponym. Named after Hokkaidô , the type locality of this new species; adjective. Distribution. Japan ( Hokkaidô ; Kyûshû: Fukuoka-ken). Remarks. A distribution map of examined specimens of this species in Japan is illustrated in Figure 22 .