Lathrobium bibaculatum, Assing, 2013

Assing, Volker, 2013, On the Lathrobium fauna of China III. New species and additional records from various provinces (Coleoptera: Staphylinidae: Paederinae), Beiträge Zur Entomologie = Contributions to Entomology 63 (1), pp. 25-52 : 31-32

Lathrobium bibaculatum sp. n.

( Figs 19-25 , 32 )

Type material:

Holotype : “ CHINA: W-Sichuan 1999, Ya’an Prefecture , Tianquan Co., E Erlang Shan Pass, 2900 m, 9 km SE Luding, 29°52N, 102°18E, Gesiebe, 20. VI., leg. M. Schülke / Holotypus  Lathrobium bibaculatum sp. n., det. V . Assing 2012” (cAss). Paratypes: 4 , 3 : “ CHINA W. Sichuan (Ganzi Tibet. Aut. Pref., Luding Co.) Erlang Shan Pass , Road 318, ca. 3000 m, 8 km SE Luding, 190 km SW Chengdu , 21.-29. VI .1999 , D. W. Wrase ” (cSch, cAss); 1 , 1 : “ CHINA: W-Sichuan 1999, Ganzi Tibet. Aut. Pref., Luding Co., W Erlang Shan Pass, 2900 m, 29°51N, 102°17E, Weiden + Moos, Blockhalde , 21. VI., leg. M. Schülke ” (cSch, cAss); 1 : “ CHINA: W-Sichuan 1999, Ya’an Prefecture, Tianquan Co., E Erlang Shan Pass, 2900 m, 9 km SE Luding, 29°52N, 102°18E, Gesiebe , 22. VI ., leg. M. Schülke ” (cSch); 5 : “ CHINA: W-Sichuan, Ya’an Prefecture , Tianquan Co., W Erlang Shan Pass / 2900 m, 21. VI.1999, 29.51.13N, 102.17.28E, leg. A. Pütz, sifted” (cPüt, cAss); 1 : same data, but 29. VI .1999 ” (cPüt); 1 : “ CHINA: W-Sichuan, Ya’an Prefecture , Tianquan Co., W Erlang Shan Pass, 2780 m, 29. VI .1999 , 29.51.27N, 102.15.47E, leg. A. Pütz, sifted” (cPüt); 2 , 1 : “ CHINA: Sichuan Prov., Tianquan County, Mt. Erlangshan , 29°52'N, 102°17'E / 11.vii.2012, alt. 2,600 –2,800 m, Dai, Peng & Yin leg.” ( SNUC) .

Etymology:

The specific epithet (Latin, adjective: with two sticks) alludes to the presence of two long spines in the internal sac of the aedeagus.

Description:

Relatively small species, without evident sexual size dimorphism. Body length 6.5-7.5 mm; length of forebody 2.9-3.3 mm. Coloration: body dark-brown to blackishbrown, elytra sometimes slightly paler brown; legs reddish to pale reddish-brown; antennae reddish.

Head ( Fig. 19 ) approximately as long as broad; punctation moderately coarse and moderately dense, sparser in median dorsal portion; interstices with pronounced microreticulation, nearly matt. Eyes weakly convex and moderately small, one fourth to nearly one third the length of postocular region in dorsal view and composed of approximately 40-50 ommatidia. Antenna 1.7-1.8 mm long.

Pronotum ( Fig. 19 ) slender, 1.26-1.30 times as long as broad and 1.20-1.05 times as broad as head; punctation similar to that of head; impunctate midline rather narrow to moderately broad; interstices without microsculpture.

Elytra ( Fig. 19 ) short, approximately 0.55 times as long as pronotum; punctation fine, sparse, shallow, and often weakly defined. Hind wings completely reduced. Protarsi with pronounced sexual dimorphism.

Abdomen with very fine, somewhat indistinct, and not particularly dense punctation, that of tergite VII distinctly sparser than that of anterior tergites; interstices with fine microsculpture; posterior margin of tergite VII without palisade fringe; tergite VIII without sexual dimorphism, posterior margin weakly convex to indistinctly obtusely pointed in the middle.

: protarsomeres I-IV strongly dilated; sternites III-VI unmodified; sternite VII ( Fig. 20 ) moderately transverse, symmetric, and with shallow median impression of triangular shape posteriorly, this impression with rather sparse strongly modified, short and stout black setae, posterior margin weakly concave in the middle; sternite VIII ( Fig. 21 ) weakly transverse, symmetric, and with long median impression, this impression with unmodified setae, posterior margin weakly and broadly concave; aedeagus ( Figs 22-24 ) 1.0- 1.1 mm long, symmetric, and with slender ventral process, apical portion of dorsal plate thin, lamellate, and rather weakly sclerotized, basal portion of dorsal plate short and extremely thin, internal sac with pair of distinctly sclerotized, very long spines.

: protarsomeres I-IV moderately dilated, much less so than in male; sternite VIII ( Fig. 32 ) approximately 0.9 mm long, weakly oblong, and with strongly convex posterior margin; tergite IX with median portion undivided and short, posterior processes moderately long and slender; tergite X flat and more than twice as long as tergite IX in the middle ( Fig. 25 ).

Comparative notes:

Based on the similar external and sexual characters, particularly the presence of a pair of spines in the internal sac and the shape of the ventral process of the aedeagus, L. bibaculatum is the sister species of L. bispinigerum , an endemic of the same mountain. For distinguishing characters see the comparative notes in the following section.

Distribution and natural history:

The species is probably endemic to the Erlang Shan in western Sichuan. The specimens were sifted from leaf litter and moss at elevations between approximately 2700 and 3000 m.

Figures

Figs 19-31: Lathrobium bibaculatumsp. n. (19-25) and L. bispinigerum sp. n. (26-31): forebody (19, 27); male sternite VII (20); male sternite VIII (21); aedeagus in lateral and in ventral view (22-23, 28-29); internal structures of aedeagus in dorsal view (24, 30); female tergites IX-X (25, 31); habitus (26). Scale bars: 19, 26-27: 1.0 mm; 20-25, 28-31: 0.5 mm.

Figs 32-43: Lathrobium bibaculatum sp. n. (32), L. bispinigerum sp. n. (33-35), and L. bihastatum sp. n. (36-43): female sternite VIII (32, 35, 42); male sternite VII (33, 37); male sternite VIII (34, 38); forebody (36); aedeagus in lateral and in ventral view (39-40); internal structures of aedeagus in dorsal view (41); female tergites IX-X (43). Scale bars: 36: 1.0 mm; 32-35, 37-43: 0.5 mm.