Plastus Plastus amplus Wu & Zhou

Wu, Jie & Zhou, Hong-Zhang, 2010, Taxonomic study of subgenus Plastus s. str. (Coleoptera, Staphylinidae, Osoriinae) in China, with descriptions of five new species, ZooKeys 51, pp. 17-32 : 20-23

Plastus Plastus amplus Wu & Zhou sp. n. Figs 161116, 17

Type material.

Holotype male, Xizang: Motuo, 1370 m, 18.ix.1979, Gentao Jin and Jianyi Wu coll. (SEM-CAS). Paratypes (13 spp.): 2 males and 9 females, same data as for holotype; male, Xizang: Motuo: Kabu, 1100 m, 8.v.1980, Gentao Jin and Jianyi Wu coll. (SEM-CAS); female, Xizang: Motuo, 1000-1200 m, 11.ii.1983, Yinheng Han coll. (IZ-CAS).

Description.

Measurement. Body length: 10.04-11.13 mm; HL: 0.74-0.82 mm; HW: 1.58-1.70 mm; PL: 1.70-1.97 mm; PW: 2.23-2.47 mm; EL: 2.49-2.58 mm; EW: 2.35-2.54 mm.

Coloration. Head black with labrum red-brown, mandibles black with inner side red-brown (Fig. 6). Pronotum and elytra black (Fig. 1). Abdomen black except for 8th segment slightly brown. Antennae brown. Femora black, tibiae black at base and gradually becoming brown apically. Tarsi slightly yellow-brown.

Structural attributes. Head transverse (Fig. 6), about twice as long as wide, sides slightly concave in middle and slightly convex outward basally; frontal impression strongly transverse, about 3.5 times as wide as long, anterior margin slightly arc-shaped and weakly emarginate in middle with two small granulated frontal teeth on sides, distance between apices of two frontal teeth almost as wide as 2/3 of frontal impression, posterior margin slightly emarginate in middle and slightly obliquely convergent posteriorly; lateral teeth blunt and distinctly convergent anteriorly with apices slightly introflexed, on apical 1/3 of ventral side with distinct subsidiary denticle apically pointed and curved forward, on inner side with row of 5-6 long setae extending onto anterior margin of frontal impression; lateral impression triangularly and widely depressed along almost whole external side of lateral tooth and anterior margin of frontal angle of head, bearing 4-6 short setae; anterior margin of frontal angle of head slightly convex forming small and blunt outer lateral tooth; median sulcus on vertex about twice as long as frontal impression, gradually broadened posteriorly, but abruptly divergent at posterior 1/3, the posterior end of which is almost twice as wide as middle; clypeus short and steeply inclined, anterior margin slightly rounded, baso-laterally with 3-5 long setae; eye glabrous and convex, almost occupying half side of head; vertex moderately convex, in depressed regions near frontal impression with shallow longitudinal depression on each side of median sulcus, surface evenly covered with fine micropunctures, along lateral and postero-lateral margin with some scattered punctures and long setae, at each side of posterior end of median sulcus with 4-7 setiferous punctures concentrated in shallow foveae.

Antennae subgeniculate, antennomere I baculiform and apically slightly depressed to form shallow sulcus on dorsal side, antennomere II smallest, slightly transverse; antennomere III elongate about 1.7 times as long as II; antennomeres IV and V almost quadrate; antennomeres VI–X gradually more transverse apically; antennomere XI elongate, apically rounded, about twice as long as X.

Mentum trapeziform (Fig. 11), frontal angle slightly rounded, anterior margin weakly depressed in middle, with small pointed median denticle, ventral surface setose, with three transverse ridges, first distinct and almost straight, second and third slightly wrinkled and indistinct, disc between third ridge and posterior margin polished and with 4 or 5 larger setiferous punctures scattered along base of third ridge.

Pronotum transverse, distinctly wider than head, anterior margin weakly bisinuate, sides almost parallel, median longitudinal sulcus deep and narrow, slightly broadened posteriorly, not reaching either anterior nor posterior margins; lateral marginal area with 30-35 setiferous punctures, punctures on upper half distinctly larger than on lower half, disc polished, with indistinct micropunctures evenly distributed.

Protibiae externally furnished with 11-15 denticles, which gradually become shorter basally.

Elytra almost quadrate, epipleural line complete, setiferous punctures on lateral marginal side sparser and less distinct than those on sides of pronotum.

Abdomen cylindrical, along anterior and posterior margin of III–VI segments respectively with row of setae, but VI segment distinctly with additional median row of setae extending to central disc, segments VII and VIII densely setose, disc of III–VI segment densely punctured except for transverse glabrous region near to posterior margin, basal distinctly denser than apical, on disc of VII and VIII, centrally with longitudinal glabrous region, narrow and extending to basal region.

Aedeagus submembranous (Figs 16, 17), basal part of median lobe slightly bulbous and strongly curved behind basal orifice, almost L-shaped in lateral view; posterior part baculiform, slightly narrower than basal bulbous part, sides almost parallel, distinctly sclerotised on both ventral and lateral sides, with apex membranous and protruding; parameres elongate and weakly curved with apices not extending beyond apical level of basal protruding part, anterior margin strongly convex and pointed near base; basal part protruding ventrally, but not connecting to each other below basal orifice.

Remarks.

This new species is similar to Plastus Plastus brachycerus (Kraatz, 1859), but can be distinguished from the latter by more transverse frontal impression, anteriorly convergent lateral teeth and small outer lateral teeth on anterior margin of frontal angle of head (Fig. 6).

Distribution.

Only known from type locality in Xizang, elevations of 1000-1370 m.

Etymology.

The species name is derived from Latin word ‘amplus’ (broad) to indicate distinctly transverse frontal impression of head.