Lathrobium bisinuatum Assing & Peng

Assing, Volker, Peng, Zhong & Zhao, Mei-Jun, 2013, On the Lathrobium fauna of the Emei Shan, Sichuan, China (Coleoptera, Staphylinidae, Paederinae), ZooKeys 277, pp. 47-67 : 61-63

Lathrobium bisinuatum Assing & Peng sp. n. Figs 2F812

Type material.

Holotype ♂: 'CHINA: Sichuan Prov., Emeishan City, Mt. Emeishan, 29°31'N, 103°20'E, 28.vii.2009, alt. 3,000 m, He & Tang leg. / Holotypus ♂ Lathrobium bisinuatum sp. n., det. Assing & Peng 2012' (SNUC). Paratypes: 5♀♀: same data as holotype; 1♂, 3♀♀: same data, but '17.vii.2009, alt. 3,000 m, Li-Zhen Li leg.'; 2♂♂, 3♀♀: same data, but ' 29°32'N, 103°20'E, 18.vii.2012, alt. 2,500-2,600 m, Dai, Peng & Yin leg.'; 9♂♂, 5♀♀: same data, but '19.vii.2012, alt. 2,800-3,000 m, Dai, Peng & Yin leg.'; 4♂♂, 1♀: same data, but '20.vii.2012, alt. 2,800-3,000 m, Dai, Peng & Yin leg.'; 1♂, 1♀: 'P. R. CHINA, Sichuan, EmeiShan, 29°31'36.8"N, 103°19'52.1"E, 15.vi.2010, 2926 m, sifting 30, V. Grebennikov'; 4♀♀: 'P. R. CHINA, Sichuan, Emei Shan, 29°33.6'N, 103°20.6'E, 27.vi.-5.vii.2009, 1800-2400 m, siftings 11-17, V. Grebennikov'; 3♀♀: 'P. R. CHINA, Sichuan, EmeiShan, 29°30'46.5"N, 103°19'47.0"E, 14.vi.2010, 3035 m, sifting 28, V. Grebennikov'; 3♂♂, 3♀♀: 'CHINA Sichuan, Emei Shan, Leidongping, 2500 m, 18.VII.1996, 29°32N, 103°21E C65 / collected by A. Smetana, J. Farkač and P. Kabátek' (Paratypes in CAS, SNUC, cSme, and cAss).

Etymology.

The specific epithet (Latin, adjective) alludes to the bisinuate posterior margin and the bisinuate dorsal plate (lateral view) of the aedeagus.

Description.

Small species without sexual size dimorphism. Body length 5.2-6.5 mm; length of forebody 2.6-2.8 mm. Habitus as in Fig. 2F. Coloration: body dark-brown to blackish-brown, abdominal apex indistinctly paler; legs and antennae reddish. Pronotum moderately slender, 1.21-1.26 times as long as broad. Posterior margin of tergite VIII truncate to weakly convex in both sexes. Other external characters as in Lathrobium hastatum .

Male. Sternites III-VI unmodified. Sternite VII strongly transverse, symmetric, with shallow median impression posteriorly, this impression with sparse and unmodified pubescence; posterior margin weakly and broadly concave (Fig. 8D). Sternite VIII moderately transverse, symmetric, shallowly impressed along the middle, this impression posteriorly with cluster of dense modified black setae on either side of middle; posterior excision very shallow, posterior margin on either side of this impression weakly concave (Fig. 8E). Sternite IX as in Fig. 8F. Aedeagus (Figs 8G, H) 0.9-1.0 mm long; ventral process laterally compressed, rather short, subapically curved, and apically acute; apical portion of dorsal plate of conspicuous shape, very long and slender, bisinuate in lateral view, and considerably projecting beyond apex of ventral process apically; basal portion of dorsal plate very short; internal sac with small and weakly sclerotized basal sclerite and with additional, semi-transparent apical sclerite.

Female. Sternite VIII 0.8-0.9 mm long, weakly oblong, posterior margin distinctly produced in the middle, apex of this projection truncate to weakly convex (Fig. 8B). Tergite IX undivided in the middle, with long median portion, and with relatively short postero-lateral processes; tergite X much shorter than tergite IX in the middle (Fig. 8C).

Comparative notes.

Among the Lathrobium species known from the Emei Shan, Lathrobium bisinuatum is most closely related to the species pair Lathrobium ensigerum + Lathrobium hastatum , a conclusion supported particularly by the structure of the aedeagus (presence of an apical internal sclerite; strongly developed apical portion and reduced basal portion of the dorsal plate) and additionally by the similar female secondary sexual characters (shape of sternite VIII; relative length and shapes of tergites IX and X), the somewhat similar shape and chaetotaxy of the male sternite VIII (posteriorly with shallow excision and with clusters of modified black setae), and the similar external characters. In external characters, Lathrobium bisinuatum is most similar to Lathrobium hastatum , from which it is distinguished by smaller size, darker average coloration, the less slender pronotum, as well as by the male sexual characters.

Distribution and natural history.

Like the other species described above, Lathrobium bisinuatum is probably endemic to the Emei Shan, where it was found primarily at high altitudes (2,500-3,000 m). In one locality at 2,500 m, Lathrobium bisinuatum was found together with Lathrobium iunctum and Lathrobium hastatum . Four females were collected somewhere between 1,800-2,400 m; they have the same label data as specimens of Lathrobium iunctum , Lathrobium coniunctum , and/or Lathrobium hastatum , suggesting that they were collected syntopically. Some of the specimens were sifted from rhododendron litter and humus in a rhododendron forest on a west slope near the mountain summit at an altitude of 2,800-3,035 m (Fig. 12).