Lathrobium iunctum 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 : 51-52

Lathrobium iunctum Assing & Peng sp. n. Figs 2A39

Type material.

Holotype ♂: 'CHINA: Sichuan, Prov. Emeishan City, Mt. Emeishan, 29°33'N, 103°20'E, 23.vii.2012, alt. 2,000-2,300 m, Dai, Peng & Yin leg. / Holotypus ♂ Lathrobium iunctum sp. n., det. Assing & Peng 2012' (SNUC). Paratypes: 10♂♂, 13♀♀: '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'; 1♂: 'P. R. CHINA, Sichuan, Emei Shan, 29°32.932'N, 103°20.466'E, 2310 m, 01.vii.2009, sifting 14, V. Grebennikov'; 1♂, 3♀♀: 'P. R. CHINA, Sichuan, EmeiShan, 29°32'56.0"N, 103°20'28.0"E, 2310 m, 20.vi.2010, sifting 38, V. Grebennikov'; 1♀: 'P. R. CHINA, Sichuan, EmeiShan, 29°33'36.3"N, 103°20'38.0"E, 1947 m, 15.vi.2010, sifting 33, V. Grebennikov'; 10♂♂, 9♀♀: '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, cSme, and cAss).

Etymology.

The specific epithet (Latin, adjective: connected, fused) alludes to the merged ventral process and dorsal plate of the aedeagus.

Description.

Species of moderately large and somewhat variable size, without sexual size dimorphism. Body length 8.0-9.5 mm; length of forebody 3.4-4.2 mm. Habitus as in Fig. 2A. Coloration: body blackish-brown to black, abdominal apex indistinctly paler; legs reddish-brown to dark-brown with pale-reddish tarsi; antennae reddish.

Head usually weakly transverse, 1.00-1.05 times as broad as long; punctation variable, moderately coarse to coarse and moderately dense to dense, sparser in median dorsal portion; interstices with fine but distinct microreticulation. Eyes weakly convex and rather large, approximately half the length of postocular region in dorsal view, or nearly so, and composed of numerous (> 50) ommatidia. Antenna 2.0-2.3 mm long.

Pronotum relatively broad, approximately 1.2 times as long as broad and 1.05-1.10 times as broad as head; punctation similar to that of head or somewhat finer; impunctate midline moderately broad; interstices without microsculpture.

Elytra short and broad, distinctly dilated posteriorly, approximately 0.55 times as long as pronotum, and at posterior margin approximately 1.6-1.7 times as broad (combined width) as long; punctation somewhat variable, usually shallow and moderately defined. Hind wings completely reduced. Protarsi without evident sexual dimorphism, moderately dilated in both sexes.

Abdomen with fine and rather dense punctation, that of tergite VII only slightly sparser than that of anterior tergites; interstices with fine microsculpture; posterior margin of tergite VII without palisade fringe; tergite VIII without sexual dimorphism, with truncate to weakly convex posterior margin.

Male. Sternites III-VI unmodified. Sternite VII strongly transverse, with asymmetric, somewhat oblique median impression posteriorly, this impression with pronounced and extensive cluster of numerous distinctly modified, short and stout black setae; posterior margin bisinuate or with shallow excision in asymmetric position (Fig. 3A). Sternite VIII transverse, pubescence unmodified; posterior excision almost symmetric, narrowly V-shaped and rather deep, its depth approximately 1/4-2/5 the length of sternite (Fig. 3B). Sternite IX as in Fig. 3D. Aedeagus (Figs 3C, E) approximately 1.5 mm long, slender, distinctly asymmetric, and with rather small basal portion; ventral process and dorsal plate fused; internal sac with small and weakly sclerotized basal sclerite.

Female. Sternite VIII approximately as long as broad and with distinctly convex posterior margin, its shape similar to that of Lathrobium coniunctum (cf. Fig. 4B). Tergite IX undivided in the middle, with short median portion, and with long posterior processes; tergite X more than twice as long as tergite IX in the middle.

Comparative notes.

In external characters, Lathrobium iunctum is highly similar to the closely related Lathrobium coniunctum and Lathrobium conexum (see comparative notes in the following section), from which it is reliably distinguished only by the male sexual characters (shape and chaetotaxy of the male sternite VII; deep and narrow posterior excision of the male sternite VIII; shape of the aedeagus).

Distribution and natural history

. This species is most likely endemic to the Emei Shan, where the type specimens were sifted from leaf litter at elevations from approximately 1,800 to 2,500 m, together with Lathrobium coniunctum , Lathrobium hastatum , and Lathrobium bisinuatum . The locality where the holotype was collected is illustrated in Fig. 9.