Trisunius penicillatus, Assing, 2015

Assing, Volker, 2015, A revision of Trisunius V. Three new species and additional records, including the first records of the genus from Vietnam (Coleoptera: Staphylinidae: Paederinae), Linzer biologische Beiträge 47 (2), pp. 1179-1190 : 1187-1189

Trisunius penicillatus nov.sp. ( Figs 13-18 )

T y p e m a t e r i a l: Holotype 3: " THAILAND [58] - Doi Pha Hom , Huay Nam Saw, 20°04'N, 99°11'E, 1530 m, along stream, 23.I.2014, leg. Ob / Holotypus 3 Trisunius penicillatus sp. n. det. V. Assing 2015" (cAss).

E t y m o l o g y: The specific epithet is an adj ective derived from the Latin noun penicillum (brush) and alludes to the conspicuous pair of clusters of black setae at the posterior margin of the male sternite VII.

D e s c r i p t i o n: Body length 3.3 m m; length of forebody 1.8 mm. Habitus as in Fig. 13 . Coloration: head dark-brown; pronotum brown; elytra dark-brown, with the posterior and postero-sutural portion extens ively and diffusely paler; abdomen darkbrown; legs pale yellowish-brown; antennae reddish.

Head ( Fig. 14 ) approxim ately 1.05 times as long as broad; lateral m argins behind eyes subparallel in dorsal view; punctation extrem ely fine and dense; interstices with pronounced microreticulation, particularly on frons, rendering the surface matt or nearly so. Eyes weakly protruding from lateral contours of head approximately 0.6 times as long as postocular region in dorsal view. Antenna 0.95 mm long.

Pronotum ( Fig. 14 ) 1.17 tim es as long as broad and 0.9 tim es as broad as head; lateral margins distinctly converging posteriad in dorsal view; posteriorly with a fine m edian furrow; punctation very fine and dense, but slightly more distinct than that of head; impunctate midline indistinct; interstices without microsculpture and glossy.

Elytra ( Fig. 14 ) slightly longer than pronotum; punctation very fine and dense; interstices without microsculpture. Metatarsomere I approximately as long as II.

Abdomen approximately as broad as elytra; punctation very fine and very dense; interstices with distinct microreticulation; posterior margin of tergite VII with palisade fringe; posterior margin of tergite VIII weakly convex.

3: sternite VII ( Fig. 15 ) distinctly transverse, with extensive, but not very deep posteromedian impression, this im pression with dense and rather long black pubescence in posterior portion, posterior margin with br oad and very shallow posterior excision, on either side with a conspicuous dense cluster of long and stout black setae; sternite VIII ( Fig. 16 ) weakly transverse, without pubescence in postero-m edian portion, posterior excision narrow and approximately 0.3 tim es as deep as length of sternite; aedeagus ( Figs 17-18 ) small and compact, 0.25 m m long (0.32 m m including apical internal structures); ventral process short and apically truncate in ventral view; apical internal structures somewhat shaped like an "H" in ventral view.

C o m p a r a t i v e n o t e s: This species is characterized particularly by the distinctive shape and chaetotaxy of the male sternite VII and by the morphology of the aedeagus. Based on the sim ilarly derived general m orphology of the aedeagus (small size, very short and broad ventral process, internal sac with conspicuous apical structures, T. penicillatus is closely allied to T. truncatus ASSING, 2011 ( China: western Yunnan), from which it differs by the more slender pronotum, the conspicuous m odifications of the male sternite VII, and by the narrower posterior excision of the male sternite VIII. For illustrations of T. truncatus and other Trisunius species see A SSING (2011, 2012, 2013, 2014).

D i s t r i b u t i o n a n d n a t u r a l h i s t o r y: The type locality is situated in Doi Pha Hom in the extreme north of Thailand, very close to the border with Burma. The holotype was sifted from leaf litter along a stream at an altitude of 1530 m.

Figures

Figs 13-18: Trisunius penicillatus nov.sp.: (13) habitus; (14) forebody; (15) male sternite VII; (16) male sternite VIII; (17-18) aedeagus in lateral and in ventral view. Scale bars: 13: 1.0 mm; 14: 0.5 mm; 15-16: 0.2 mm; 17-18: 0.1 mm.