Youtrechus, Tian & Huang & Jia, 2023

Tian, Mingyi, Huang, Sunbin & Jia, Xinyang, 2023, A contribution to cavernicolous beetle diversity of South China Karst: eight new genera and fourteen new species (Coleoptera: Carabidae: Trechini), Zootaxa 5243 (1), pp. 1-66 : 5-6

Youtrechus n. gen.

Type species: Youtrechus zijunae n. sp. (Feixian Dong, Xianning , Hubei)

Generic characteristics. Medium-sized for cave trechines, semi-aphaenopsian body moderately elongate, surface glabrous. Head stout, slightly longer than wide, sides slightly expanded; neck narrow, constriction well-marked; presence of two pairs of supraorbital setiferous pores; frontal furrows well-marked, not parallel-sided, slightly divergent at base, strongly contracted medially, and widely divergent posteriorly; frons rather flat, vertex convex; right mandibular tooth tridentate, though median one more or less reduced; mentum and submentum separated by labial suture, mentum bisetose, base largely concave, tooth short, widened and blunt at apex; submentum with a row of 6 setae; antennae fairly long, extending at about apical 1/5 and 1/4 of elytra in male and female respectively. Prothorax not tumid, propleura invisible from above; pronotum quadrate, as long as head excluding mandibles, widest at about 1/3 from front, hind angles nearly rectangular, pointed; base emarginate; presence of two pairs of latero-marginal setae; disc slightly convex. Elytra elongated ovate, longer than head plus pronotum, widest at about middle, humeral angles completely rounded; lateral margins smooth and glabrous throughout; disc strongly convex, striae fine and deep, intervals convex; presence of three dorsal and one preapical pores; humeral set of the marginal umbilicate pores not aggregated. 1 st and 2 nd protarsomeres widened and protruded inwardly at apex in male; tibiae longitudinally sulcated. Ventrites smooth, IV– VI each with two pairs of paramedial setae, together with several pubescence in middle portion, VII bisetose apically in male, 6-setose in female. Male genitalia: aedeagus wellsclerotized, moderately elongated, strongly arcuate near base; base large and wide, apical lobe broad in frontal view, slightly bent at tip in lateral view. Parameres thin and small, each with three long setae at apex.

Etymology. “You” + Trechus , “You” means dark in Chinese, referring to the trechine beetles living in subterranean habitat. Gender masculine.

Remarks. Youtrechus is the unique cavernicolous genus of the tribe Trechini known so far from southeastern Hubei Province. It has no evident relative because the locality (cave Feixian Dong) is very far from those of other cave trechine beetles. For instance, the closest cave is Shuilian Dong in northwestern Jiangxi Province (the locality of Luoxiaotrechus Tian & Yin, 2013 ), which is 260 km in linear distance from Feixian Dong. However, the combined generic characters of Youtrechus such as body shape, tridentate right mandibular tooth, modified protarsomeres 1 and 2 in male, presence of labial suture and chaetotaxy patterns on head, pronotum and elytra indicate that this new genus is probably close to the genus Qianaphaenops Uéno, 2000 which is a diverse complex occurring in Guizhou, Chongqing and Shaanxi ( Uéno 2000, Tian et al. 2018, Chen et al. 2019).

Youtrechus may be related to some Japanese trechines (such as Epaphiopsis Uéno, 1953 , Trechiama Jeannel, 1927 and so on) or to Trechiotes Jeannel, 1954 because the presence of a dorsal seta on the 5 th elytral interval, in a more posterior position than the two setae of the 3 rd stria which is a very important character.

This new genus is easily recognized by its stout head with well-developed frontal furrows, quadrate pronotum with well-marked hind angles, elytra with three dorsal pores, and, in particular, the male genital organ which is remarkably enlarged and elongated at base and strongly arcuate near base.

Range. China (Hubei) ( Figure 1n ).

Figures

FIGURE 1. Map indicating the locality caves of the new genera and species. a. Xianren Dong; b. Shisanya Dong; c. Da Dong, Tuoluo; d. Da Dong, Bali; e. Weixiao Tiankeng; f. Laba Dong; g. Gui Dong; h. Suolue Cave I; i. Xiannü Dong; j. Jiudu Cave I; k. Xiannü Dong; l. Yunxian Dong; m. Zhongguo Dong; n. Feixian Dong.