Lathrobium imberbe, 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 : 21

Lathrobium imberbe sp. n.

( Figs 115–122 )

Type material: Holotype : “ NEPAL Prov. Karnali, Distr. Dolpa, Kagmara Lekh, Garpung Khola , 3000–3800 m 10.V.1995 leg. A. Weigel / Holotypus  Lathrobium imberbe sp. n., det. V. Assing 2013” ( NME).

Paratypes: 1 : same data as holotype (cAss); 1 : “ NEPAL, Prov. Karnali, Garpung Khola E Hurikot, Bachtal , 3800 m NN, 12.V.1995, leg.: J. Weipert ” ( NME) .

Etymology: The specific epithet (Latin, adjective: without beard) alludes to the absence of a comb of palisade setae at the posterior margin of the male sternite VII.

Description: Body length 5.0– 5.8 mm; length of forebody 2.6–2.9 mm. Habitus as in Fig. 115 . Coloration: whole body, including the appendages, reddish.

Head ( Fig. 116 ) 1.03–1.05 times as long as broad; punctation sparse and moderately coarse; interstices on average distinctly broader than diameter of punctures, with shallow microreticulation. Eyes small, composed of approximately 10 ommatidia, approximately one-fifth as long as postocular region in dorsal view. Antenna 1.4–1.5 mm long.

Pronotum ( Fig. 116 ) slender, 1.25–1.30 times as long as broad and about as broad as head; punctation similar to that of head; midline broadly impunctate; interstices without microsculpture.

Elytra ( Fig. 116 ) rather broad, 0.56–0.60 times as long as pronotum; punctation distinct and moderately dense; interstices without distinct microsculpture. Hind wings completely reduced. Protarsomeres I–IV with weakly pronounced sexual dimorphism.

Abdomen only slightly broader than elytra; punctation not very fine and moderately dense; interstices with shallow microsculpture; posterior margin of tergite VII without palisade fringe; posterior margin of tergite VIII weakly convex, without appreciable sexual dimorphism.

: protarsomeres I–IV moderately dilated; sternite VII ( Fig. 117 ) distinctly transverse and with sparse unmodified pubescence, posterior margin broadly concave; sternite VIII ( Fig. 118 ) as long as broad, in the middle with extremely short, fine, and sparse pubescence, posterior excision moderately deep (approximately 0.2 times as deep as length of sternite) and slightly asymmetric; aedeagus ( Figs 119–120 ) 1.25 mm long and apically weakly asymmetric; ventral process shaped like a stout spine; dorsal plate short and lamellate, in lateral view very weakly curved; internal sac without sclerotized structures.

: protarsomeres I–IV moderately dilated, slightly less so than in male; sternite VIII ( Fig. 121 ) approximately 1.15 times as long as broad and with moderately sparse pubescence, posterior margin strongly convex; tergite IX ( Fig. 122 ) undivided in the middle, postero-lateral processes short and apically acute, slightly extending beyond apex of tergite X; tergite X ( Fig. 122 ) flat, of oval shape, and distinctly longer than antero-median portion of tergite IX.

Comment and comparative notes: According to the species group concept proposed in ASSING (2012), L. imberbe would have to be attributed to the L. aculeatum group, which previously included two species from Central Nepal, L. aculeatum COIFFAIT, 1982 and L. spiculatum ASSING, 2012 . These two species probably represent adelphotaxa and are mainly distinguished from the species of the L. pectinatum group by the absence of combs of palisade setae and a more slender aedeagus. Regarding the morphology of the aedeagus, L. imberbe is intermediate between the species of the L. pectinatum group and those previously attributed to the L. aculeatum group. With respect to other external and male sexual characters the species of both groups are very similar. These observations and supporting zoogeographic evidence make it seem likely that the absence of combs of palisade setae at the posterior margin of the male sternite VII is actually a secondary reduction that may have occurred convergently. Consequently, L. imberbe , L. aculeatum , and L. spiculatum are assigned to the L. pectinatum group.

Lathrobium imberbe is readily distinguished from L. aculeatum and L. spiculatum , with which it shares the unmodified chaetotaxy of the male sternite VII, by the different morphology of the aedeagus. Most other species of the L. pectinatum group have conspicuous combs of palisade setae on the male sternite VII. For illustrations of the previously described representatives of the L. pectinatum group see ASSING (2012).

Distribution and natural history: The species was found in two geographically close localities in the Garpung Khola valley in Dolpa District, Karnali Province, West Nepal ( Map 2 ). One paratype was collected at an altitude of 3800 m, the remaining type specimens at an elevation between 3000 and 3800 m, together with an unnamed species ( Lathrobium sp. 1 ; see below).

Figures

Map 2:Distributions of Lathrobium species inNepal:L. flexaculeatum (white square),L. rectaculeatum (blackstar),L. curvaculeatum (white star), L. hebes (black square), L. imberbe (black triangle), L. plicatum (black diamond), L. calcaratum (circles; white circles: new records; black circle: type locality), L. fodens (white triangles), L. aculeatum (white diamonds).

Figs 115–129: Lathrobium imberbe sp. n. (115–122) and L. aculeatum COIFFAIT (123–129): habitus (115, 123); forebody (116, 124); male sternite VII (117, 125); male sternite VIII (118, 126); aedeagus in lateral and in ventral view (119–120, 127–128); female sternite VIII (121, 129); female tergites IX–X (122). Scale bars: 115–116, 123–124: 1.0 mm; 117–122, 125–129: 0.5 mm.