Lathrobium tricarinatum, Assing, 2015

Assing, Volker, 2015, New species and additional records of Lathrobium and Elytrobium from the Palaearctic region, with special reference to the fauna of East Yunnan (Coleoptera: Staphylinidae: Paederinae), Beiträge Zur Entomologie = Contributions to Entomology 65 (1), pp. 41-74 : 52-54

Lathrobium tricarinatum spec. nov.

( Figs 36–44 )

Type material: Holotype : “ CHINA [7] – Yunnan, mts W Dongchuan, 2620 m, 26°06'08"N, 102°54'46"E, pine for., 14.VIII.2014, V. Assing / Holotypus  Lathrobium tricarinatum spec. nov., det. V. Assing 2014” (cAss).

Paratypes: 2 , 1  [1 teneral]: same data as holotype (cAss).

Etymology: The specific epithet (Latin, adjective) alludes to the presence of three carinae on the ventral process of the aedeagus.

Description: Species of moderate size, without evident sexual size dimorphism; body length 7.3–7.7 mm; length of forebody 3.3–3.5 mm. Habitus as in Fig. 36 . Coloration: body black; legs pale-brown, with the profemora darkbrown and with the tarsi yellowish-brown; antennae reddish.

Head ( Fig. 37 ) weakly transverse, approximately 1.03 times as broad as long, usually weakly dilated behind eyes; punctation moderately coarse and moderately sparse, in median dorsal portion sparser; interstices with distinct microreticulation, on average somewhat broader than diameter of punctures in lateral and posterior dorsal portions. Eyes weakly convex, weakly projecting from lateral contours of head and of moderate size, slightly less than half, but distinctly more than one-third as long as postocular region in dorsal view and composed of significantly more than 50 ommatidia. Antenna approximately 1.8 mm long.

Pronotum ( Fig. 37 ) rather broad and relatively weakly oblong, 1.15–1.20 times as long as broad and approximately 1.1 times as broad as head; punctation similar to that of head; impunctate midline moderately broad; interstices without microsculpture.

Elytra ( Fig. 37 ) short and broad, approximately 1.7 times as broad (combined width) as long and approximately 0.53 times as long as pronotum, not distinctly dilated posteriad; humeral angles moderately marked; punctation moderately dense, shallower than that of pronotum; interstices without microsculpture. Hind wings completely reduced. Protarsomeres I–IV with weak, but noticeable sexual dimorphism.

Abdomen approximately 1.1 times as broad as elytra; punctation fine, rather dense on tergites III–VI, sparser on tergite VII; interstices with shallow transverse microsculpture; posterior margin of tergite VII without palisade fringe; tergite VIII with weak sexual dimorphism.

: protarsomeres I–IV distinctly dilated; posterior margin of tergite VIII very obtusely angled in the middle; sternite VII ( Fig. 38 ) distinctly transverse, approximately 1.55 times as broad as long, posteriorly without distinct median impression and with broadly and weakly concave posterior margin, pubescence not distinctly modified; sternite VIII ( Fig. 39 ) nearly as long as broad, posteriorly with very small excision and with an ill-defined cluster of moderately modified black setae; aedeagus ( Figs 40–42 ) approximately 1.2 mm long, slightly asymmetric, dorsoventrally depressed, weakly sclerotized apically, and with small basal portion; ventral process slightly asymmetric, apically deeply bifid, the apices slender, ventrally with two lateral carinae in basal half and one median carina extending from apical incision to basal third; dorsal plate weakly sclerotized, truncate basally and convex apically, and without separate basal portion; internal sac with an irregular membranous ring-shaped structure, without additional structures.

: protarsomeres I–IV dilated, but slightly less so than in male; posterior margin of tergite VIII distinctly angled in the middle (more so than in male); sternite VIII ( Fig. 43 ) approximately 1.1 times as long as broad and with strongly convex posterior margin; tergite IX ( Fig. 44 ) with short antero-median portion with median suture, and with slender postero-lateral processes; tergite X ( Fig. 44 ) flattened and very long, approximately six times as long as antero-median portion of tergite IX.

Comparative notes: Based on the external and sexual characters, particularly on the modifications of the aedeagus, L. tricarinatum belongs to the L. tentaculatum group. It is distinguished from both L. crenatum and L. rostratum by the morphology of the aedeagus and by the smaller posterior excision of the male sternite VIII, from the geographically close L. crenatum additionally by smaller body size, slightly smaller eyes, the different shape and chaetotaxy of the male sternite VII, and by the slightly longer antero-median portion of the female tergite IX.

Distribution and natural history: The type locality is situated near the Sedan Snow Mountain Scenic Resort in the mountains to the West of Dongchuan, northeastern Yunnan. The specimens were sifted from litter, moss, and the roots of herbs in a terraced secondary pine forest at an altitude of 2620 m. One of the paratypes is teneral.

Figures

Figs 36–53: Lathrobium tricarinatum spec. nov. (36–44) and L. laciniatum spec. nov. (45–53): habitus (36, 45); forebody (37, 46); male sternite VII (38, 47); male sternite VIII (39, 48); aedeagus in ventral view (40, 49); aedeagus in dry preparation in ventral view (41, 50); aedeagus in dry preparation in dorsal view (42); female sternite VIII (43, 52); female tergites IX–X (44, 53); apical portion of aedeagus in dorsal view (51). Scale bars: 36–37, 45–46: 1.0 mm; 38–44, 47–50, 52–53: 0.5 mm; 51: 0.2 mm.