Lathrobium semicirculatum, Assing, 2014

Assing, Volker, 2014, New species and records of Lathrobium from the Palaearctic region, primarily from Nepal (Coleoptera: Staphylinidae: Paederinae), Beiträge Zur Entomologie = Contributions to Entomology 64 (1), pp. 1-28 : 3-5

Lathrobium semicirculatum sp. n.

( Figs 1–9 , Map 1 )

Type material: Holotype : “ NEPAL, Mechi / Taplejung, 17,5 km NE Ghunsa, Lhonak , 4770 m, 27°47'27"N, 88°02'12"E, 12.V.2003, leg. A. Weigel / Holotypus  Lathrobium semicirculatum sp. n., det. V. Assing 2013” ( NME) . Paratypes: 1 : same data as holotype (cAss); 2 : “ NEPAL Yalungi , Taplejung 3500 m, V.1989 P. Morvan ” (cRou, cAss) .

Etymology: The specific epithet (Latin, adjective: semicircular) refers to the shape of the posterior excision of the male sternite VIII.

Description: Body length 6.0– 7.6 mm; length of forebody 3.0– 3.2 mm. Habitus as in Fig. 1 . Coloration: body blackish; legs dark-brown; antennae reddish to dark-brown.

Head ( Fig. 2 ) weakly oblong, 1.02–1.04 times as long as broad; punctation sparse and moderately coarse; interstices much broader than diameter of punctures, with fine but distinct microreticulation. Eyes moderately small, composed of approximately 30–40 ommatidia, one-fourth to one-third as long as postocular region in dorsal view. Antenna approximately 1.7 mm long.

Pronotum ( Fig. 2 ) approximately 1.15 times as long as broad and 1.04–1.10 times as broad as head; punctation similar to that of head, but denser; midline moderately broadly impunctate; interstices without microsculpture.

Elytra ( Fig. 2 ) rather broad, transverse, and short, approximately 0.53 times as long as pronotum; punctation fine and shallow; interstices without distinct microsculpture. Hind wings completely reduced. Protarsomeres I–IV with weakly pronounced sexual dimorphism.

Abdomen approximately 1.15 times as broad as elytra; punctation fine and moderately dense; microsculpture shallow on tergites III–VI, somewhat more pronounced on tergites VII–VIII; posterior margin of tergite VII without palisade fringe; tergite VIII with weakly convex posterior margin, without distinct sexual dimorphism.

: protarsomeres I–IV moderately dilated; sternite VII ( Fig. 3 ) strongly transverse, with relatively sparse unmodified setae, middle narrowly without setae, posterior margin broadly concave; sternite VIII ( Fig. 4 ) weakly transverse, approximately 1.07 times as broad as long, in postero-median portion (anterior to postero-median excision) with dense and rather short setae, otherwise with relatively sparse unmodified setae, posterior excision weakly asymmetric, of nearly semi-circular shape; aedeagus ( Figs 5–7 ) approximately 1.25 mm long, slender, and strongly curved in lateral view, weakly asymmetric in ventral view; ventral process with pronounced long median carina; dorsal plate lamellate, distinctly sclerotized, with long apical portion and short basal portion; internal sac with long dark membranous structures.

: protarsomeres I–IV moderately dilated, slightly less so than in male; sternite VIII ( Fig. 8 ) approximately as long as broad, posterior margin broadly convex, indistinctly angled in the middle; tergite IX ( Fig. 9 ) undivided in the middle, postero-lateral processes short, only slightly extending beyond apex of tergite X; tergite X ( Fig. 9 ) flat, of oval shape, and approximately as long as anteromedian portion of tergite IX.

Comparative notes: Based on the external and sexual characters, L. semicirculatum belongs to the L. nepalense group. Among the species of this group it is characterized particularly by the shape and chaetotaxy of the male sternite VIII, as well as by the distinctive morphology of the aedeagus. The latter is most similar to that of L. infractum ASSING, 2012 , from which L. semicirculatum differs by the sparser pubescence of the male sternite VII, the chaetotaxy and the pronounced posterior excision of the male sternite VIII (absent in L. infractum ), and by the distinctly longer, more slender, and less asymmetric aedeagus. For illustrations of other species of the L. nepalense group see ASSING (2012).

Distribution and natural history: The species was collected in two localities ( Map 1 ) in the extreme northeast of Nepal (Taplejung province and border between Taplejung and Mechi provinces), one of them to the northeast of Ghunsa and the other near the Yalung Glacier (27°37'N, 88°04'E), at altitudes of 4770 and 3500 m, respectively.

Figures

Map 1: Distributions of Lathrobium species in Nepal: L. semicirculatum (white triangles), L. constrictum (black triangle), L. descendens (white circles), L. ascendens (black circle), L. rude (white star), L. latibasale (black star), L. eques (white diamond), L. equitans (black diamond), L. abruptum (black square), L. kemum (white square).

Figs 1–15: Lathrobium semicirculatum sp. n. (1–9) and L. constrictum sp. n. (10–15): habitus (1, 10); forebody (2, 11); male sternite VII (3, 12); male sternite VIII (4, 13); aedeagus in lateral and in ventral view (5–6, 14–15); apical portion of aedeagus in ventral view (7); female sternite VIII (8); female tergites IX–X (9). Scale bars: 1–2, 10–11: 1.0 mm; 3–9, 12–15: 0.5 mm.