Batrisocenus cavernicolus Yin and He, 2020

Yin, Zi-Wei & He, Li, 2020, New Cavernicolous Pselaphinae from Sichuan, China (Coleoptera: Staphylinidae), The Coleopterists Bulletin 74 (4), pp. 827-836 : 828-830

Batrisocenus cavernicolus Yin and He , new species

zoobank.org/ urn:lsid:zoobank.org:act:F3108446-188B-48EE-A9C6-BD355CFF16A2 ( Figs. 1–2 )

Type Material (41 exx). Holotype: CHINA: ♂, “China: Sichuan, Meishan City, Renshou Co, Lujia Town , Shiping Vill., Mengjia Cave , 29°48 ′ 42.61 ′′ N, 104°20 ′ 3.94 ′′ E, 425 m, 8.iii.2020, L. He & Y. Li, 眉山市仁寿县禄加镇石坪村孟家洞” ( SNUC) . Paratypes: CHINA: 4 ♂♂, 13 ♀♀, same collection data as holotype ( SNUC); 9 ♂♂, 10 ♀♀ , “ China: Sichuan, Meishan City, Renshou Co, Lujia Town , Chongfeng Vill., Huanggu Cave , 29°48 ′ 52.86 ′′ N ,

104°22 ′ 17.96 ′′ E, 474 m, 29.ii.2020, He, Li & Zhou, 眉山市仁寿县禄加镇冲锋村黄鼓洞” (5 ♂♂, 6 ♀♀ in SNUC, 1 ♂, 1 ♀ each in CCZ, CLH, CYJL, CYL) ; 1 ♂, 2 ♀♀, same collection data except “ 21.xii.2019, L. He & Y. Li ” ( SNUC) ; 1 ♂, “ China: Sichuan, Meishan City, Renshou Co, Wangyang Town , Jinquan Vill., Shenxian Cave , 29°44 ′ 56.87 ′′ N, 104°18 ′ 9.65 ′′ E, 488 m, 8.iii.2020, L. He & Y. Li, 眉山市仁寿县汪洋镇金泉村神仙洞” ( SNUC) .

Diagnosis. Male. Habitus elongate, body length 2.35–2.47 mm; antenna and legs conspicuously elongate; dorsal surface of head and pronotum finely punctate; protibia with thin, elongate apical trichome-like structure on mesal margin, protrochanter ventrally protuberant; abdominal tergite 1 (IV) with transverse cavity at middle, and one oval nodule posterior to cavity; aedeagus with small and strongly constricted basal capsule, markedly elongate ventral lobe, and broader and shorter dorsal lobe. Female. Habitus and size similar to male; antenna slightly shorter; legs and abdomen lacking modifications; genital complex with sternite 7 (IX) about as wide as genital plate.

Description. Male ( Fig. 1A ). Body reddishbrown, length (combined from head, pronotum, elytra, and abdomen) 2.35–2.47 mm. Head subrectangular, almost as long as wide, length from anterior margin of clypeus to head base 0.46–0.48 mm, width across eyes 0.47 mm; dorsal surface ( Fig. 1B ) finely punctate; antennal tubercles prominent; vertexal foveae nude, located slightly posterior to a point level with middle of eyes, vertexal sulcus straight between antennal tubercles, interrupted anterior to vertexal foveae; antenna markedly elongate, length 1.53–1.59 mm, club weakly indicated by apical three enlarged antennomeres; ocular-mandibular carinae present; each eye composed of about 35 facets. Pronotum ( Fig. 1B ) about as long as wide, length along midline 0.50 mm, maximum width 0.51 mm; disc finely punctate; posterior margin of antebasal sulcus roughened and forming ridge; with small antebasal tubercles. Elytra together slightly wider than long, length along suture 0.72–0.78 mm, maximum width 0.75–0.79 mm, narrowed at bases, thin discal striae extending to apical 3/4 of elytral length; with slightly raised humeral prominences; marginal stria present only on posterior half of elytron, lacking subhumeral foveae. Legs distinctly elongate and slender, protrochanter ( Fig. 1C ) with two small tubercles on ventral margin; apex of protibia ( Fig. 1D ) with elongate, trichome-like modification on mesal margin. Abdomen wider than long, length along midline 0.50–0.51 mm, maximum width 0.67–0.68 mm; tergite 1 (IV) ( Fig. 1E ) longer than 2–4 (V–VII) combined, with transverse cavity at middle of tergite, anterior margin of cavity strongly prominent laterally, with row of dense setae at apices, with forked protuberance at middle and two lateral transverse ridges inside cavity, setiferous patches lateral to cavity large, one oval nodule posterior to cavity, with two clusters of thick setae at apex; discal carinae distinct, slightly oblique; marginal carinae clearly indicated only on basal half; sternite 7 (IX) ( Fig. 1F ) rounded and semimembranous. Length of aedeagus 0.31 mm, aedeagus ( Fig. 1G, H ) asymmetrical; basal capsule strongly constricted; ventral lobe extremely elongate and curved leftwards at apical 1/ 3 in ventral view; dorsal lobe long and broad through entire length in lateral view; parameres fused to form flattened ventral membrane.

Female. Similar to male in general appearance and size. Antenna slightly shorter. Each eye composed of about 20 facets. Legs and tergite 1 (IV) lacking modifications. Genital complex as in Fig. 2I . Measurements (as for male): Body length 2.36–2.38 mm; length of antenna 1.47–1.49 mm; length/width of head 0.49–0.50/ 0.47 mm; pronotum 0.48–0.51/ 0.50–0.51 mm; elytra together 0.69–0.70/ 0.75–0.76 mm; abdomen 0.64–0.45/ 0.71 mm; width of genital complex 0.27 mm.

Comparison. The roughened and ridged posterior margin of the pronotal antebasal sulcus, and the strongly constricted basal capsule of the aedeagus fit well with the concept of Batrisocenus Raffray ( Chandler 2001: 262) , a genus comprising 78 valid species distributed in the Australo-Oriental region ( Newton 2020). Three species occur in China ( Li et al. 2019): Batrisocenus cicatricosus (Raffray) from Yunnan, Batrisocenus sauteri Raffray from Taiwan, and Batrisocenus sinensis Raffray from Hong Kong, with none being associated with cave environments. Batrisocenus cavernicolus can thus be readily differentiated by the conspicuously elongate antenna and legs, unique modification of the protibia and tergite 1 (IV) of the male, as well as the shape of the aedeagus.

Notes on Collection and Biology. Most individuals were collected from the twilight to dark zone of Huangu Cave ( Figs. 2A–C ) and Mengjia Cave ( Figs. 2D–F ), typically in areas 10–50 m from the entrance. A majority of the adults were found under stones ( Figs. 2G, H ), while a few were spotted wandering around on cave walls. A single male was collected under a stone from the twilight zone of Shenxian Cave, about 10 m from the entrance.

Distribution. Southwestern China: Sichuan.

Etymology. The new specific epithet is a Latin adjective that refers to the restriction of the new species to cave environments.

Figures

Fig. 1. Habitus and diagnostic characters of Batrisocenus cavernicolus, new species, male. A) Habitus, B) Head and pronotum, C) Protrochanter, D) Protibia, E) Tergite 1 (IV), F) Sternite 7 (IX). Aedeagus: G) Ventral view, H) Lateral view. Scale bars: 1.0 mm in A; 0.3 mm in B; 0.2 mm in C, E; 0.1 mm in G, H.

Fig. 2. Collection environment, adults in situ, and female genital complex of Batrisocenus cavernicolus, new species. Arrows indicate locations of the cave entrances. Huanggu Cave: A) Nearby environment, B) Entrance, C) Inside environment. D–F) Same for Mengjia Cave. Individuals found under stones in Huanggu Cave: G) Male, H) Female. I) Female genital complex. Scale bar: 0.1 mm.