Lathrobium crenatum, 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 : 50

Lathrobium crenatum spec. nov.

( Figs 21–29 )

Type material: Holotype : “ CHINA [2] – Yunnan, mts NE Dongchuan, 2670 m, 26°14'10"N, 103°12'31"E, pine for., 9.VIII.2014, V. Assing / Holotypus  Lathrobium crenatum spec. nov., det. V. Assing 2014” (cAss).

Paratypes: 5 , 5 : same data as holotype (cAss); 3 , 3  : same data as holotype, but leg. M. Schülke (cSch); 1 , 1 : “ CHINA [2a] – Yunnan, mts NE Dongchuan, 2670 m, 26°14'10"N, 103°12'31"E, bushes, 9.VIII.2014, V. Assing” (cAss) .

Etymology: The specific epithet is an adjective derived from the Latin noun crena (notch) and alludes to the profoundly notched apex of the aedeagus.

Description: Species of moderate size, without evident sexual size dimorphism; body length 7.5–9.0 mm; length of forebody 3.7–4.0 mm. Habitus as in Fig. 21 . Coloration: body black; legs dark-brown, with the pro- and mesotibiae paler brown and the tarsi yellowish to yellowish-brown; antennae yellowish-red to reddish.

Head ( Fig. 22 ) weakly transverse, 1.01–1.06 times as broad as long, usually weakly dilated behind eyes; punctation moderately coarse and moderately sparse, in median dorsal portion sparse; interstices with distinct microreticulation, on average slightly broader than diameter of punctures in lateral and posterior dorsal portions, much broader in median dorsal portion. Eyes weakly convex, weakly projecting from lateral contours of head and rather large, approximately half as long as postocular region in dorsal view and composed of significantly more than 50 ommatidia. Antenna 2.0– 2.2 mm long.

Pronotum ( Fig. 22 ) rather broad, 1.15–1.20 times as long as broad and 1.07–1.10 times as broad as head; punctation similar to that of head; impunctate midline moderately broad; interstices without microsculpture.

Elytra ( Fig. 22 ) short and broad, approximately 1.75 times as broad (combined width) as long and 0.51–0.54 times as long as pronotum, not distinctly dilated posteriad; humeral angles moderately marked; punctation moderately dense, shallower than that of head and pronotum; interstices without microsculpture. Hind wings completely reduced. Protarsomeres I–IV with moderate 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, but noticeable sexual dimorphism.

: protarsomeres I–IV distinctly dilated; posterior margin of tergite VIII very obtusely angled in the middle; sternite VII ( Fig. 23 ) distinctly transverse, approximately 1.6 times as broad as long, posteriorly with shallow median impression and with a pair of weakly defined and sparse clusters of slightly stouter and longer black setae, posterior margin weakly concave in the middle; sternite VIII ( Fig. 24 ) weakly transverse, approximately 1.05 times as broad as long, posteriorly with dense moderately modified stout black setae, posterior margin with relatively small median excision of nearly semicircular shape; aedeagus ( Figs 25–27 ) 1.25–1.30 mm long and of highly derived morphology, strongly asymmetric, dorso-ventrally depressed, weakly sclerotized apically, and with small basal portion; ventral process asymmetric, apically deeply and asymmetrically notched, and with conspicuous latero-dorsal extension somewhat enwrapping latero-dorsal portion of aedeagus; dorsal plate asymmetric, rather weakly sclerotized, short, broad, and basally truncate, without basal portion; internal sac without noticeable structures, except for the usual ringshaped structure.

: 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. 28 ) approximately 1.1 times as long as broad and with strongly convex posterior margin; tergite IX ( Fig. 29 ) with very short and divided antero-median portion and with slender postero-lateral processes; tergite X ( Fig. 29 ) flattened and very long, approximately ten times as long as antero-median portion of tergite IX.

Comparative notes: Among the species previously recorded from Yunnan, L. crenatum is most similar – and based on the similarly derived morphology of the aedeagus most closely related – to L. tentaculatum ASSING, 2013 from the Ailao Shan, previously the sole representative of the L. tentaculatum group. Both species are externally similar (moderately large and robust black body with strongly transverse elytra and a rather broad pronotum; large eyes; similar punctation), a similar morphology of the female tergites IX and X (anteromedian portion very short and with suture; tergite X very long), a posteriorly angled tergite VIII, and particularly an aedeagus of derived morphology (distinctly asymmetric; dorso-ventrally flattened; ventral process deeply excised apically; basal portion very small; dorsal plate short and broad; internal structures absent, except for the ring-shaped structure). Lathrobium crenatum is distinguished from L. tentaculatum by smaller size, by the shapes and chaetotaxy of the male sternites VII and VIII, as well as by the shape of the aedeagus ( L. tentaculatum : ventral process apically extending into a pair of long and slender processes). For illustrations of L. tentaculatum see ASSING (2013c).

Distribution and natural history: The species was discovered in a mountain to the northeast of Dongchuan in northeastern Yunnan. The specimens were sifted from pine needles between rocks in a secondary pine forest and from litter on a scree slope with bushes and herbs at an altitude of 2670 m.

Figures

Figs 21–35: Lathrobium crenatum spec. nov. (21–29) and L. rostratum spec. nov. (30–35): habitus (21, 30); forebody (22, 31); male sternite VII (23, 32); male sternite VIII (24, 33); aedeagus in ventral view (25, 35); aedeagus in dry preparation in ventral and in dorsal view (26–27); female sternite VIII (28); female tergites IX–X (29); aedeagus in lateral view (34). Scale bars: 21–22, 30–31: 1.0 mm; 23–29, 32–35: 0.5 mm.