Lathrobium daweianum, 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 : 55-57

Lathrobium daweianum spec. nov.

( Figs 54–62 )

Type material: Holotype : “ CHINA [22] – Yunnan, SE Pingbian, primary forest, 22°54'31"N, 103°41'44"E, 2100 m, 27.VIII.2014, V. Assing / Holotypus  Lathrobium daweianum spec. nov., det. V. Assing 2014” (cAss).

Paratypes: 2 , 2 : same data as holotype, but leg. Schülke (cAss, cSch); 1 , 2 : “ CHINA [22a] – Yunnan, SE Pingbian, primary forest, 22°54'31"N, 103°41'44"E, 2100 m, 28.VIII.2014, V. Assing” (cAss); 1 : same data, but leg. M. Schülke (cSch) .

Etymology: The specific epithet is an adjective derived from the name of the mountain where the type locality is situated.

Description: Small species of slender habitus, without evident sexual size dimorphism; body length 5.5–7.0 mm; length of forebody 2.6–2.8 mm. Habitus as in Fig. 54 . Coloration: head dark-brown; pronotum and elytra reddish-brown to brown, with the suture and the posterior margins of the elytra reddish; abdomen blackish-brown to blackish, with segments VIII–X reddish; legs reddish-yellow; antennae reddish.

Head ( Fig. 55 ) oblong, approximately 1.1 times as long as broad, weakly dilated behind eyes; punctation rather dense and coarse in lateral, anterior, and posterior dorsal portions, sparse and finer in median dorsal portion; interstices with distinct microreticulation, on average approximately as broad as diameter of punctures in lateral and posterior dorsal portions. Eyes weakly convex, weakly projecting from lateral contours of head and small, approximately one-fourth as long as postocular region in dorsal view and composed of approximately 40 ommatidia. Antenna relatively short, 1.4–1.5 mm long.

Pronotum ( Fig. 55 ) slender, approximately 1.35 times as long as broad and about 1.1 times as broad as head; punctation similar that of head; impunctate midline moderately broad; interstices without microsculpture.

Elytra ( Fig. 55 ) short, 0.51–0.53 times as long as pronotum, not distinctly dilated posteriad; humeral angles moderately marked; punctation moderately dense and shallow; interstices without microsculpture. Hind wings completely reduced. Protarsomeres I–IV with rather pronounced sexual dimorphism.

Abdomen slender, only slightly broader than elytra; punctation fine, rather dense on tergites III–VII, only slightly less dense on tergite VII than on tergite VI; interstices with shallow transverse microsculpture; posterior margin of tergite VII without palisade fringe; tergite VIII with pronounced sexual dimorphism.

: protarsomeres I–IV strongly dilated; tergite VIII with weakly convex posterior margin; sternite VII ( Fig. 56 ) moderately transverse, approximately 1.4 times as broad as long, posteriorly without shallow median impression, this impression with a cluster of moderately modified long and stout setae; sternite VIII ( Fig. 57 ) approximately as long as broad, with very small and very shallow posterior excision and posteriorly with weakly modified pubescence; aedeagus ( Figs 58–59 ) approximately 1.05 mm long, nearly symmetric; ventral process long, slender, and strongly curved in lateral view; dorsal plate lamellate, with long and distinctly sclerotized apical portion and with very short unsclerotized basal portion; internal sac with two massive, broad-based, sclerotized spines of different shapes.

: protarsomeres I–IV moderately dilated, distinctly less so than in male; tergite VIII with strongly convex posterior margin; sternite VIII ( Fig. 60 ) elongated, approximately 1.35 times as long as broad and with strongly convex posterior margin; tergite IX ( Fig. 61 ) with long antero-median portion without median suture and with moderately slender postero-lateral processes; tergite X ( Fig. 61 ) flattened, only slightly longer than antero-median portion of tergite IX; segment IX ( Fig. 62 ) with a conspicuous large black internal structure.

Comparative notes: Lathrobium daweianum is readily distinguished from all other Lathrobium species recorded from eastern Yunnan by much smaller size, paler coloration, the more slender head with smaller eyes, the much more slender pronotum, the denser punctation of the abdominal tergite VII, the pronounced sexual dimorphism of the protarsi and the abdominal tergite VIII, the completely different morphology of the aedeagus, the much more oblong female sternite VIII, and the different morphology of the female tergites IX and X (tergite IX without median suture and with shorter postero-lateral processes; tergite X shorter).

The species cannot be assigned to any of the species groups previously known from Yunnan and adjacent provinces without difficulty. Based on the morphology of the female tergites IX and X, on the general morphology of the aedeagus, and on the absence of an anterior cluster of gland openings on the male sternite VIII, the only eligible candidates would be the L. curvatissimum , the L. bihamulatum , and the L. desectum groups. The latter two groups can be ruled out, too, as L. daweianum does not share the synapomorphies that constitute these groups. The new species shares the long, slender, and strongly curved ventral process of the aedeagus with species of the L. curvatissimum group, which are distributed in northwestern Yunnan and Sichuan, but it is distinguished from them by much smaller body size, a more slender body (oblong head; much more oblong pronotum, etc.), the presence of massive internal spines in the internal sac of the aedeagus, a flat female tergite X, and the presence of a large black internal structure in the female segment IX. Consequently, L. daweianum is attributed to a species group of its own.

Distribution and natural history: The type locality is situated in the Dawei Shan Virgin Forest Park to the southeast of Pingbian in southeastern Yunnan, close to the border with Vietnam. Thus, L. daweianum and the syntopic L. coadultum represent the southernmost records of the genus in mainland China. The specimens were sifted from leaf litter in a primary subtropical broadleaved forest at an altitude of 2100 m, together with the types of L. coadultum .

Figures

Figs 54–69: Lathrobium daweianum spec. nov. (54–62) and L. coadultum spec. nov. (63–69): habitus (54, 63); forebody (55, 64); male sternite VII (56); male sternite VIII (57); aedeagus in lateral view (58, 66); internal structures of aedeagus in lateral view (59); female sternite VIII (60); female tergites IX–X (61); female segments IX–X in ventral view (62); median dorsal portion of head (65); aedeagus in dry preparation in lateral, ventral, and dorsal view (67–69). Scale bars: 54–55, 63–64: 1.0 mm; 56–62, 66–69: 0.5 mm; 65: 0.2 mm.