Stenus fuscus Hu & Tang, sp. n.

(Figs. 3, 17–22)

Type Material. Holotype: China: Sichuan: ♂, glued on a card with labels as follows: “ China: Sichuan Prov., Mianning County, Yele Daba, 28°55'22''N, 102°13'32''E, 2500m, 25.VII.2015, Jiang, Peng, Tu & Zhou leg.” “ Holotype / Stenus fuscus / Hu & Tang” [red handwritten label] (SHNU) . Paratypes: 5♂♂ 3♀♀, same data as for the holotype. (SHNU, cPut)

Description. BL: 4.0– 4.3 mm, FL: 1.9–2.1 mm.

HW: 0.86–0.90 mm, PL: 0.69–0.73 mm, PW: 0.63–0.69 mm, EL: 0.66–0.71 mm, EW: 0.70–0.79 mm, SL: 0.50–0.53 mm.

Similar to S. lizipingus sp. nov. in most respects, but different in the following characters: head 1.11–1.23 times as wide as elytra, lateral portion of head with distinct microsculptures; pronotum relatively longer with PL/ PW: 1.04–1.13; elytra relatively narrower with 0.87–0.93 times as long as wide; elytral disk impressions shallower; punctation of abdominal tergites relatively smaller and slightly sparser than that of S. lizipingus sp. nov.

Male. Sternite VIII (Fig. 17) with emargination in the middle of posterior margin; sternite IX (Fig. 18) with very long apicolateral projections, posterior margin serrate. Aedeagus (Figs. 19, 20) with median lobe stout, apical sclerotized area broadly and bluntly, pointed at apex; expulsion clasps large; parameres distinctly longer than median lobe, swollen at apical third, each with 9–12 setae on apico-internal margins.

Female. sternite VIII (Fig. 21) slightly prominent at middle of posterior margin; spermatheca (Fig. 22)sclerotized, basal porch very large, spermathecal duct with two bents, apical chamber large and capsule very large.

Distribution. China (Sichuan).

Remarks. The new species is similar to S. lizipingus sp. nov. both occurred in same locality, and it can be distinguished from the latter by the exterior characters indicated above and the different sexual characters. It is also similar to S. zhuxiaoyui Tang & Zhao, 2008, S. pectorifossatus Tang & Zhao, 2008 and S. erlangshanus Tang & Zhao, 2008 from Sichuan, and can be distinguished from S. zhuxiaoyui and S. erlangshanus by more confluent pronotal punctation, from S. zhuxiaoyui also by larger body size (FL: 1.5–2.0 mm in S. zhuxiaoyui), from S. erlangshanus by lacking distinct subbasal and subapical pronotal impressions and abdominal tergites mostly with microsculptures, from S. pectorifossatus by darker elytral coloration and sparser abdominal punctation.

Etymology. The specific name is derived from the lartin word “ fuscus ” after its dark coloration.