Orsunius stimulans, Assing, 2014

Assing, V., 2014, On Orsunius II. Eight new species and additional records (Coleoptera: Staphylinidae: Paederinae: Medonina), Linzer biologische Beiträge 46 (1), pp. 461-479 : 466

Orsunius stimulans nov.sp.

( Figs 7-8 , 10-13 , Map 2 )

Type material: Holotype: " Vietnam-N, Quang Binh prov., 1 km N of Cha Lo, 400 m, Vietnam-Laos border area , 17°41'22''N, 105°45'45''E, L. Dembický leg., 11.-24.iv.2010 / Holotypus Orsunius stimulans sp.n. det. V. Assing 2013" ( NHMB) . Paratype: "Thai 25.5.91, Fang 300 m, 19°55'N, 99°12'E, David Král lgt." (cAss).

Etymology: The specific epithet is the present participle of the Latin verb stimulare (to sting) and alludes to the acute apex of the ventral process of the aedeagus.

Description: Body length 3.8-4.1 mm; length of forebody 2.1-2.2 mm. Habitus as in Fig. 10 . Body distinctly bicoloured: head blackish; pronotum pale-reddish; elytra yellowish, with the middle and the lateral margins more or less extensively infuscate; abdomen brown to dark-brown, with the apex more or less extensively yellowish; legs yellowish; antennae reddish.

Head ( Fig. 11 ) transverse, approximately 1.15 times as broad as long, slightly tapering behind eyes, and with moderately marked posterior angles; posterior margin weakly concave in the middle; punctation very dense, moderately coarse, and umbilicate; interstices without microsculpture; dorsally with moderately long and laterally with very long black setae. Eyes very large and bulging, longer than postocular portion in dorsal view. Antennae 1.1-1.3 mm long and slender; preapical antennomeres very weakly transverse. Anterior margin of labrum with U-shaped excision in the middle.

Pronotum ( Fig. 11 ) approximately 1.15 times as wide as long and nearly as broad as head; posterior angles rounded, weakly marked; lateral margins with numerous long black setae; punctation similar to that of head; midline with distinct impunctate band at least in posterior two-thirds; interstices without microsculpture.

Elytra ( Fig. 11 ) nearly 1.15 times as long as pronotum; punctation dense, approximately as coarse as that of pronotum; interstices without microsculpture. Hind wings fully developed. Protarsomeres I-IV distinctly dilated in both sexes. Metatarsomere I long and slender, approximately as long as the combined length of II and III.

Abdomen narrower than elytra; punctation fine and very dense; posterior margin of tergite VII with palisade fringe.

: sternite VII ( Fig. 7 ) with weakly concave posterior margin; sternite VIII ( Fig. 8 ) weakly oblong and with V-shaped posterior excision; aedeagus ( Figs 12-13 ) long in relation to body size, 0.75 mm long, ventral process long, slender, and apically very acute.

Comparative notes: Aside from the distinctive morphology of the aedeagus and the shape of the male sternite VIII, O. stimulans is characterized particularly by the coloration, the umbilicate punctation of the head and pronotum, and by the slender legs and antennae.

Distribution and natural history: The type locality is situated in North Vietnam, near the border with Laos, at an altitude of 400 m. The paratype was collected in the extreme north of Thailand ( Map 2 ), close to the border with Myanmar, at an altitude of 300 m.

Figures

Map 2: Distributions of Orsunius gladiator (white and black circles), O. latexcisus (black circle), O. flavovirgatus (black circle), O. heissi (black star), O. stimulans (black and grey triangles), O. granulosus (white and grey triangles), O. cuneatus (white diamond), and O. spathulatus (black square).

Figs 1-9: Orsunius spathulatus nov.sp. (1-6), O. stimulans nov.sp. (7-8), and O. gladiator nov.sp. (9): (1) habitus; (2) forebody; (3, 8, 9) male sternite VIII; (4) posterior portion of male sternite VIII; (5) aedeagus in lateral view; (6) ventral process in ventral view; (7) male sternite VII. Scale bars: 1- 2: 1.0 mm; 3-9: 0.2 mm.

Figs 10-17: Orsunius stimulans nov.sp. (10-13) and O. gladiator nov.sp. (14-17): (10, 14) habitus; (11, 15) forebody; (12, 16) aedeagus in lateral view; (13) aedeagus in ventral view; (17) ventral process in ventral view. Scale bars: 10-11, 14-15: 1.0 mm; 12-13, 16-17: 0.2 mm.