CHINA: Guizhou: Holotype: ♂, glued on a card with labels as follows: “China: N. Guizhou, Daozhen Co., Dashahe, 29°10'12"N, 107°33'36"E, mixed leaf litter, sifted, 1730 m, 07.VII.2015, Jiang, Peng, Tu & Zhou leg.”. “Holotype / Stenus dashaheensis / Liu, Tang & Luo” [red handwritten label] (SHNU). Paratypes: 2♂♂3♀♀, same data as for the holotype. (SHNU, cPut).

Figures 1–6. 

Habitus. 1, 2 Stenus dashaheensis sp. n. 3, 4 Stenus zhangyuqingi sp. n. 5, 6 Stenus liuyixiaoi sp. n. Scale bars: 1 mm.

The new species can be distinguished from other related species by the following characters: body size smaller (BL < 4.2 mm), elytra distinctly shorter than wide (EL/EW= 0.84–0.90), the rather smooth surfaces of pronotum and elytra, and the larger and less confluent punctation of pronotum and elytra than abdomen.

Brachypterous; body dark brown, each elytron with an orange spot near lateral margin. Antennae except the infuscate club, maxillary palpi, and legs yellowish brown. Labrum reddish brown. BL: 3.3–4.1 mm, FL: 1.7–2.0 mm. HW: 0.69–0.84 mm, PL: 0.55–0.65 mm, PW: 0.53–0.61 mm, EL: 0.57–0.68 mm, EW: 0.64–0.78 mm, SL: 0.43–0.49 mm.

Head 1.06–1.18 times as wide as elytra; interocular area with two deep longitudinal furrows, median portion convex, extending beneath the level of inner eye margins; punctures round, slightly larger and sparser on median portion than those near inner margins of eyes, diameter of large punctures slightly wider than apical cross section of antennal segment II; interstices between punctures smooth, much narrower than half the diameter of punctures except those along the midline of the median portion, which may be slightly narrower than the diameter of punctures. Paraglossae oval.

Pronotum 0.98–1.05 times as long as wide; disk relatively smooth (without impressions) with median longitudinal furrow indistinct; punctures round and slightly confluent, variable in size, slightly larger than those of head; interstices smooth, much narrower than half the diameter of punctures except for few near the actual middle, which may be as wide as the diameter of punctures.

Elytra 0.84–0.90 times as long as wide; disk relatively smooth; punctures round to elliptical, moderately confluent, similar in size to those on pronotum; interstices smooth, distinctly smaller than half the diameter of punctures.

Legs with tarsomeres IV strongly bilobed.

Abdomen cylindrical; paratergites very narrow and almost impunctate, present only in segment III, tergites and sternites totally fused in segments IV–VI, posterior margin of tergite VII with an indistinct apical membranous fringe; punctation of tergites III–VIII sparse and shallow, gradually becoming smaller posteriorly; interstices smooth, mostly wider than diameter of punctures except those on basal impressions of tergites III–V, which may be distinctly narrower than half the diameter of punctures.

Male. Sternite VIII (Fig. 7) with distinct triangular emargination at middle of posterior margin; sternite IX (Fig. 8) with long apicolateral projections, posterior margin serrated. Aedeagus (Figs 9–10) with apical sclerotized portion weakly prominent at apex; sclerotized expulsion clasps large, median ventral band long, narrow, dorsal bands short and relatively broad, lateral longitudinal bands short; copulatory tube stout; parameres longer than median lobe, each with 10–13 setae on apico-internal margins.

Figures 7–12. 

Stenus dashaheensis sp. n. 7 male sternite VIII 8 male sternite IX 9, 10 aedeagus.11 female sternite VIII 12 valvifers and spermatheca. Scale bars: 0.25 mm.

Female. Sternite VIII as in Fig. 11; sclerotized spermatheca (Fig. 12) consisting of basal duct, swollen spermathecal duct, and capsule.

China (Guizhou).

The new species is similar to S. bullatus Liu & Tang, 2017 from Guangxi, but can be easily distinguished from the latter by the less confluent punctation of the pronotum and the elytra, and by shorter elytra (in S. bullatusEL/EW = 0.90–1.07).

The specific name is derived from the type locality of this species.

CHINA: Guizhou: Holotype: ♂, glued on a card with labels as follows: “China: N. Guizhou, Libo County Maolan N.R., Dongdai, 25°17'13"N, 107°56'23"E, 792 m, 24.iv.2017, mixed leaf litter, sifted, Jiang, Jiang, Hu, Liu & Zhang leg.”. “Holotype / Stenus zhangyuqingi / Liu, Tang & Luo” [red handwritten label]. Paratypes: 4♂♂5♀♀, same data as for the holotype. (SHNU, cPut).

The new species is the most characteristic of the group characterized by the largest body, longer than 4.2 mm, a broad head up to 0.83–0.96 mm, and a shallower and narrower median longitudinal furrow of the pronotum than the other two species in this paper.

Macropterous; body blackish, each elytron with an elongated yellow spot near lateral margin. Antennae (except the infuscate club), maxillary palpi, and legs yellowish brown. Labrum reddish brown. BL: 4.2–5.1 mm, FL: 2.1–2.5 mm. HW: 0.83–0.96 mm, PL: 0.64–0.79 mm, PW: 0.61–0.69 mm, EL: 0.84–1.00 mm, EW: 0.78–0.93 mm, SL: 0.68–0.79 mm.

Head 1.03–1.13 times as wide as elytra; interocular area with two deep longitudinal furrows, median portion convex, extending beneath the level of inner eye margins; punctures round and more or less confluent, larger and sparser on median portion than those near inner margins of eyes, diameter of large punctures larger than apical cross-section of antennal segment II; interstices between punctures smooth, much narrower than half the diameter of punctures except those along the midline of the median portion, which may be as wide as half the diameter of punctures. Paraglossae oval.

Pronotum 1.02–1.15 times as long as wide; disk with impressions, with a shallow and narrow median longitudinal furrow; punctures round and moderately confluent, variable in size, on average larger than those of head; interstices smooth, much narrower than half the diameter of punctures except for those along the middle of posterior half pronotum, which may be as wide as the diameter of punctures.

Elytra 1.07–1.16 times as long as wide; disk smooth; punctures round, moderately confluent, slightly larger than those on pronotum; interstices smooth, distinctly smaller than half the diameter of punctures.

Legs with tarsomeres IV strongly bilobed.

Abdomen cylindrical; paratergites very narrow and almost impunctate, visible only in segment III, tergites and sternites totally fused in segments IV–VI, posterior margin of tergite VII with apical membranous fringe; punctation of tergites III–VIII sparse and shallow, gradually becoming smaller posteriorly; interstices smooth, narrower than half the diameter of punctures on tergite III, narrower than half the diameter to diameter of punctures on tergites III and IV.

Male. Sternite VIII (Fig. 13) with shallow emargination at middle of posterior margin; sternite IX (Fig. 14) with long apicolateral projections, posterior margin serrate. Aedeagus (Figs 15–16) with apical sclerotized portion triangular , convex at apex; internal structures: sclerotized expulsion clasps long, median ventral band long, narrow, dorsal bands long, lateral bands short; copulatory tube rather short, the main tube weakly curved near the middle; parameres longer than median lobe, slightly swollen in apical part, each with 10–12 setae on apicointernal margins.

Figures 13–18. 

Stenus zhangyuqingi sp. n. 13 male sternite VIII 14 male sternite IX 15, 16 aedeagus 17 female sternite VIII 18 valvifers and spermatheca. Scale bars: 0.25 mm.

Female. Sternite VIII as in Fig. 17; sclerotized spermatheca (Fig. 18) with spermathecal duct very coiled.

China (Guizhou).

The new species is closely related to S. guangxiensis Rougemont, 1984 from Zhejiang, Anhui, and Guangxi, as well as to S. liuyixiaoi sp. n., but can be easily distinguished from them by the narrower elytra (in the other two species, HW similar to or distinctly smaller than EW) and different sexual characters.

This species is named in honor of Mr. Yu-Qing Zhang who collected some of the specimens of the new species.

CHINA: Guizhou: Holotype: ♂, glued on a card with labels as follows: “China: N. Guizhou, Libo County Maolan N.R., Bizuo, 25°16'59"N, 106°03'18"E, 587 m, 28.iv.2017, mixed leaf litter, sifted, Jiang, Jiang, Hu, Liu & Zhang leg.”. “Holotype / Stenus liuyixiaoi / Liu, Tang & Luo” [red handwritten label] (SHNU). Paratypes: 6♂♂9♀♀, same data as for the holotype (SHNU, cPut); 2♀♀, Maolan N.R., Dongdai, 25°17'51"N, 107°57'15"E, 808 m, 22.iv.2017, mixed leaf litter, sifted, Jiang, Jiang, Hu, Liu & Zhang leg. (SHNU); 4♂♂3♀♀, Maolan N.R., Dongdai, 25°17'58"N, 107°57'06"E, 874 m, 25.iv.2017, mixed leaf litter, sifted, Jiang, Jiang, Hu, Liu & Zhang leg. (SHNU); 1♂2♀♀, Dongdai, 25°17'13"N, 107°56'23"E, 792 m, 24.iv.2017, mixed leaf litter, sifted, Jiang, Jiang, Hu, Liu & Zhang leg. (SHNU).

The new species is characterized by large body size (4.2–5.8 mm) and relatively sparse punctation of the entire body, especially of the abdominal tergites.

Macropterous; body blackish, each elytron with a large yellow spot near its lateral margin. Antennae (except the infuscate club), maxillary palpi, and legs yellowish brown. Labrum reddish brown. BL: 4.2–5.8 mm, FL: 2.0–2.6 mm. HW: 0.77–0.96 mm, PL: 0.64–0.78 mm, PW: 0.61–0.72 mm, EL: 0.90–1.07 mm, EW: 0.82–1.01 mm, SL: 0.72–0.86 mm.

Head 0.93–1.03 times as wide as elytra, pronotum 1.06–1.13 times as long as wide, elytra 1.03–1.12 times as long as wide.

Other external characters as in S. zhangyuqingi sp. n., except that the punctation of the pronotum and abdomen is slightly sparser.

Male. Sternite VIII (Fig. 19) with shallow emargination at middle of posterior margin; sternite IX (Fig. 20) with long apicolateral projections, posterior margin serrated. Aedeagus (Figs 21–22) with triangular apical sclerotized portion and convex apex; internal structures: sclerotized expulsion clasps large, median ventral band long, narrow, lateral bands short; copulatory tube long, weakly curved in the middle; parameres longer than median lobe, swollen at apical parts, each with 11–13 setae on apicointernal margins.

Figures 19–24. 

Stenus liuyixiaoi sp. n. 19 male sternite VIII 20 male sternite IX 21, 22 aedeagus 23 female sternite VIII 24 valvifers and spermatheca. Scale bars: 0.25 mm.

Female. Sternite VIII as in Fig. 23; spermatheca (Fig. 24) strongly sclerotized with

spermathecal duct very coiled.

Distribution. China (Guizhou).

Remarks. The new species is closely related to S. zhangyuqingi sp. n., but may be distinguished from the latter by the relatively sparser punctation of pronotum and abdomen. It is also very similar to S. guangxiensis Rougemont, 1984, from which it is distinguished only based on the sexual characters.

Etymology. This species is named in honor of Mr. Yi-Xiao Liu who collected some specimens of the new species.