Ckacus, Tian & Huang, 2021

Tian, Mingyi & Huang, Sunbin, 2021, Discovery of a new cavernicolous trechine genus and species from a deep pit in Anlong, southwestern Guizhou Province (Coleoptera: Carabidae: Trechinae), Zootaxa 4985 (2), pp. 194-202 : 196

Ckacus n. gen.

(Chinese name: 喀Ḇù步fflƌ)

Type species: Ckacus youcha n. sp. (Luoshui Dong cave, Xianheping, Anlong , Qianxinan , Guizhou)

Generic characteristics. Medium-sized for cavernicolous trechine beetles, semi-aphaenopsian wholly pubescent, eyeless and depigmented; body rather thin, elongate, with moderate slender appendages. Head strongly elongate; genae nearly parallel-sided; two pairs of supra-orbital setiferous pores present; frontal furrows short and reduced posteriorly; vertex moderately convex; right mandibular tooth tridentate though median one reduced; labial suture completely disappeared; mentum bisetose, base largely and deeply concave; submentum with a row of 12-setose; antennae moderately thin, not extending over apices of elytra. Propleura invisible from above; pronotum quadrate, slightly longer than wide, presence of two pairs of latero-marginal setae, both fore and hind angles sharpened. Elytra elongated ovate, with a distinct but rounded humeral angle on each side; slightly longer than fore body including mandibles; lateral margins ciliate throughout; disc strongly convex, punctation of striae noticeable, intervals convex, the 1 st intervals very narrowed in apical 1/3; two pairs of dorsal setiferous pores present on the 3 rd stria, preapical pores present; the 4 th pore of marginal umbilicate series far from the 3 rd, 5 th and 6 th pores close to each other. The 1 st and 2 nd protarsomeres modified in male, slightly widened and distinctly denticulate inwardly. Ventrite VII with one pair of apical setae in male. Male genitalia thin and elongate, moderately sclerotized.

Remarks. Ckacus looks like Bathytrechus Uéno, 2005 , which was recorded from the cave Tiankeng Dong in Leye, northwestern most of Guangxi, in the medium and elongate body which is wholly pubescent, the tridentate right mandible, sharpened hind angles of pronotum, and entirely striate elytra with the first intervals extremely narrowed at the apical third of elytra. However, it differs from the latter genus in many characters, such as: (1) Mentum and submentum completely fused and submentum 12-setose, versus labial suture traceable and submentum only 6-setose in Bathytrechus ; (2) Frontal furrows distinctly reduced posteriorly, versus entire in Bathytrechus ; (3) 1 st and 2 nd protarsomeres modified in male, versus not modified in Bathytrechus ; (4) the middle group of the marginal umbilicate pores close to each other, versus widely spaced in Bathytrechus ; and (5) apical striole of elytra absent, versus present in Bathytrechus . In addition, male genitalia is much more elongate, with a sharp apical lobe in Ckacus , whereas shorter and apical lobe rod-like in Bathytrechus .

Etymology. The generic name is derived from the abbreviations of “ China Karst Cave Union” (中国喀Dz特洞 ËḆDz). Gender masculine.

Generic range. China (Guizhou).