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

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Stenus exesus Liu and Tang

new species

Stenus exesus Liu and Tang  , new species

( Figs 5, 6View FIGURES 5 – 6, 33–40View FIGURES 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)GoogleMaps  . Paratupes : 4♂♂ 6♀♀, same data as for the holotype ( SHNU)GoogleMaps  . 2♂♂ 2♀♀, Mt. Mao’ershan , 25°54'N 110°27'E, alt. 1550–1750 m. HU Jia-Yao & SONG Xiao-Bin leg. ( SHNU)GoogleMaps  .

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. 33View FIGURES 33 – 40) with round emargination at middle of posterior margin; sternite IX ( Fig. 35View FIGURES 33 – 40) with long apicolateral projections, posterior margin serrate; tergite X ( Fig. 34View FIGURES 33 – 40) with posterior margin truncate and slightly emarginated at middle. Aedeagus ( Fig. 36View FIGURES 33 – 40) 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. 38View FIGURES 33 – 40) entire; tergite X ( Fig. 40View FIGURES 33 – 40) with posterior margin truncate; spermatheca ( Fig. 39View FIGURES 33 – 40) 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.