Lathrobium ensigerum Assing & Peng

Assing, Volker, Peng, Zhong & Zhao, Mei-Jun, 2013, On the Lathrobium fauna of the Emei Shan, Sichuan, China (Coleoptera, Staphylinidae, Paederinae), ZooKeys 277, pp. 47-67 : 56-58

Lathrobium ensigerum Assing & Peng sp. n. Figs 2D6

Type material.

Holotype ♂: 'P. R. CHINA, Sichuan, EmeiShan, 29°32'57.2"N, 103°20'37.7"E, 16.vi.2010, 2289 m, sifting35, V. Grebennikov, Holotypus ♂ Lathrobium ensigerum sp. n., det. V. Assing 2012' (CAS). Paratype ♀: same data as holotype (cAss).

Etymology.

The specific epithet (Latin, adjective: carrying a sword) alludes to the shape of the ventral process of the aedeagus.

Description.

Large species; body length 11.0-13.0 mm; length of forebody 5.5-5.8 mm. Habitus as in Fig. 2D. Coloration: head and pronotum blackish-brown to black; elytra reddish-brown; abdomen brown to dark-brown, apex (posterior margin of segment VII; segments VIII-X) slightly paler; legs and antennae reddish to reddish-brown, antennomere I somewhat infuscate.

Head weakly oblong, approximately 1.05 times as long as broad; punctation not particularly coarse and moderately dense, sparser in median dorsal portion; interstices with fine but distinct microreticulation. Eyes weakly convex and rather small, less than one third or even only one fourth as long as postocular region in dorsal view. Antenna 3.2-3.3 mm long.

Pronotum slender, approximately 1.35-1.40 times as long as broad and 0.95 times as broad as head; punctation similar to that of head or somewhat finer; impunctate midline broader posteriorly than anteriorly; interstices without microsculpture.

Elytra short, not distinctly dilated posteriorly (i.e., lateral margins subparallel in dorsal view), approximately 0.50-0.55 times as long as pronotum; punctation shallow and dense. Hind wings completely reduced. Protarsi with weakly pronounced sexual dimorphism.

Abdomen with fine and rather dense punctation, that of tergite VII slightly sparser than that of anterior tergites; interstices with fine microsculpture; posterior margin of tergite VII without palisade fringe; tergite VIII without sexual dimorphism, in both sexes with weakly convex posterior margin.

Male. Sternites III-VI unmodified. Sternite VII (Fig. 6D) strongly transverse, with median impression of triangular shape posteriorly, this impression with numerous distinctly modified, short and stout black setae; posterior margin distinctly concave in the middle. Sternite VIII (Fig. 6E) moderately transverse, with pair of posteriorly diverging impressions posteriorly, these impressions with numerous modified short black setae; posterior margin bisinuate, i.e., the shallow median excision with projection in the middle. Aedeagus (Figs 6C, F, G) 2.1 mm long and symmetric; ventral process blade-shaped, laterally compressed; dorsal plate with apical portion large, distinctly curved in lateral view, and apically acute in dorsal view; basal portion very short and thin; internal sac with long sclerotized spine and apically with additional, weakly sclerotized structure.

Female. Sternite VIII 1.7 mm long, distinctly oblong, posterior margin strongly produced in the middle (Fig. 6A). Tergite IX undivided in the middle, with long median portion, and with moderately long posterior processes; tergite X sharply keeled along the middle and approximately as long as tergite IX in the middle (Fig. 6B).

Comparative notes.

Lathrobium ensigerum is readily distinguished from all other species known from the Emei Shan by its much larger size alone. In addition, it is characterized by the slender pronotum, as well as the distinctive male and female sexual characters. For details regarding its phylogenetic affiliations see the comparative notes in the following section.

Distribution and natural history.

The type locality is situated in the Emei Shan. The specimens were sifted from leaf litter at an altitude of nearly 2,300 m.