Stenus exesus Liu and Tang

Liu, Sheng-Nan & Tang, Liang, 2017, Seven new species of the Stenus cirrus group (Coleoptera, Staphylinidae) from Guangxi, South China, Zootaxa 4268 (2), pp. 238-254 : 242-243

Stenus exesus Liu and Tang , new species

( Figs 5, 6 , 33–40 )

Type material. CHINA: Guangxi: Holotype: ♂, Xing’an County, Mao’ershan Mt. , 25°48'N 110°24'E, alt. 1500 m, 24.VII.2012, ZHU Jian-Qing leg. ( SHNU) . Paratupes : 4♂♂ 6♀♀, same data as for the holotype ( SHNU) . 2♂♂ 2♀♀, Mt. Mao’ershan , 25°54'N 110°27'E, alt. 1550–1750 m. HU Jia-Yao & SONG Xiao-Bin leg. ( SHNU) .

Description. Brachypterous; body brownish black, head darker, each elytron with a small and conspicuous orange spot near lateral margin, which is about 1/2 as long as and 2/5 as broad as the respective elytron. Antennae, maxillary palpi and legs yellowish brown except antennal club infuscate. Labrum reddish brown.

BL: 4.3–5.2 mm, FL: 2.0– 2.2 mm.

HW: 0.76–0.92 mm, PL: 0.65–0.70 mm, PW: 0.62–0.67 mm, EL: 0.65–0.78 mm, EW: 0.74–0.79 mm, SL: 0.51–0.59 mm.

Head 1.01–1.07 times as wide as elytra; interocular area with two deep longitudinal furrows, median portion convex, extending to the level of inner eye margins; punctures round, larger and sparser on median portion than those near inner margins of eyes, diameter of large punctures about as wide as apical cross section of antennal segment II; interstices between punctures smooth, distinctly narrower than half the diameter of punctures, except few along the midline of the posterior median portion, which may be rarely wider than the diameter of punctures. Paraglossae oval.

Pronotum 1.00–1.06 times as long as wide, disk moderately uneven, with very shallow median longitudinal furrow, which is about 1/2 the length of pronotum; punctures mostly round and more or less confluent, about the same size to those of head; interstices smooth, distinctly narrower than half diameter of punctures except in median furrow, which may be as wide as the diameter of punctures.

Elytra 0.87–0.99 times as long as wide, disk uneven; punctation similar to that of head, except for punctures larger.

Legs with tarsomeres IV strongly bilobed.

Abdomen cylindrical; paratergites narrow and almost impunctate, present only in segment III, tergites and sternites totally fused in segments IV–VI, posterior margin of tergite VII without distinct palisade fringe; punctures round to elliptic, gradually becoming smaller and sparser posteriad; interstices smooth, mostly much wider than diameter of punctures except those on basal impressions of tergites III–V, varied from smaller to larger than diameter of punctures.

Male. Sternite VIII ( Fig. 33 ) with round emargination at middle of posterior margin; sternite IX ( Fig. 35 ) with long apicolateral projections, posterior margin serrate; tergite X ( Fig. 34 ) with posterior margin truncate and slightly emarginated at middle. Aedeagus ( Fig. 36 ) with apical sclerotized portion triangular and roundly projected at apex; expulsion clasps not existed; parameres distinctly longer than median lobe, swollen at apical parts, with 19–21 setae on apico-internal margins.

Female. Sternite VIII ( Fig. 38 ) entire; tergite X ( Fig. 40 ) with posterior margin truncate; spermatheca ( Fig. 39 ) strongly sclerotized, similar to that of S. bullatus , except for less swollen spermatheca duct.

Distribution. China (Guangxi).

Remarks. The new species is unique among the member of Stenus cirrus group by lacking expulsion clasps of aedeagus. In general appearance, it is similar to S. lijinweni Tang, Zhao & Puthz 2008 from Jiangxi and Zhejiang, and S. bullatus sp. n. from same locality, but can be distinguished from the latter two by the sparser punctation of tergite III, from S. bullatus also by smaller ratio of HW/EW ( S. exesus : 1.01–1.07; S. bullatus : 1.09–1.18).

Etymology. The specific name is derived from the Latin word ‘exesus’, meaning ‘inexistent, shortage’, referring to the lacking expulsion clasps of aedeagus.

Figures

FIGURES 5 – 6. Dorsal habitus of Stenus exesus sp. n. Scale bars: 1 mm.

FIGURES 33 – 40. Diagnostic features of Stenus exesus. 33. Male sternite VIII. 34. Male tergites IX – X. 35. Male sternite IX. 36 – 37. Aedeagus, in dorsal view. 38. Female sternite VIII. 39. Valvifers and spermatheca. 40. Female tergites IX – X. Scale bars: 0.25 mm.