Hypomedon bicornutus, Assing, 2016

Assing, Volker, 2016, On some Acanthoglossa and Hypomedon species II. Two new species, a new synonymy, and additional records (Coleoptera: Staphylinidae: Paederinae), Linzer biologische Beiträge 48 (1), pp. 317-325 : 324

Hypomedon bicornutus nov.sp.

( Figs 18-21 )

Type material: Holotype ♂: " LAOS-NE, Xieng Khouang prov., ~ 19°37 -8'N 103°20'E, Phonsavan (30 km NE): Phou Sane Mt. , ~ 1400-1500 m, 10-30.v.2009, Z. Kraus leg. / Holotypus ♂ Hypomedon bicornutus sp.n. det. V. Assing 2016" ( NHMB).

Etymology: The specific epithet (Latin, adjective: with two horns) alludes to the deeply bifid ventral process of the aedeagus.

Description: Body length 3.3 mm; length of forebody 1.9 mm. Coloration: body dark-brown; legs brown; antennae with antennomeres I-II brown and antennomeres III-XI pale-brown.

Head ( Fig. 18 ) 1.1 times as broad as long; punctures large, but shallow, very dense, and umbilicate; interstices without microsculpture. Eyes approximately half as long as postocular region in dorsal view. Antenna: antennomere III approximately as broad as long; antennomeres IV-X of gradually increasing width and increasingly transverse; X approximately 1.5 times as broad as long.

Pronotum ( Fig. 18 ) 1.06 times as broad as long and approximately as broad as head; punctation very dense, umbilicate, and shallow; punctures smaller than those of head; interstices without microsculpture.

Elytra ( Fig. 18 ) approximately 1.05 times as long as pronotum; punctation very dense and fine; interstices without microsculpture.

Abdomen narrower than elytra; punctation extremely dense and extremely fine on all tergites; interstices with microsculpture; posterior margin of tergite VII with palisade fringe.

♂: sternite VII unmodified; sternite VIII ( Fig. 19 ) weakly transverse and with shallow posterior excision; aedeagus ( Figs 20-21 ) 0.5 mm long; ventral process distinctly bifid; internal structures of distinctive shapes.

Comparative notes: Hypomedon bicornutus is distinguished from H. debilicornis , H. galilaeus , and H. nasutus by the absence of microsculpture on the head and pronotum, denser punctation of the forebody, much denser and finer punctation of the abdomen, the shape of the male sternite VIII, and by the completely different morphology of the aedeagus (ventral process bifid; internal structures large and distinctly sclerotized). In fact, the species differs so significantly from other Hypomedon species that it is attributed to this genus with some doubt.

Distribution: The type locality is situated 30 km to the northeast of Phonsavan, North Laos, at an altitude of 1400-1500 m.

Figures

Figs 14-21: Hypomedon nasutus nov.sp. (14-17) and H. bicornutus nov.sp. (18-21): (1-2) forebody; (3-10) aedeagus in lateral and in ventral view; (11-13) male sternite VIII. Scale bars: 14, 18: 0.5 mm; 15-17, 19-21: 0.2 mm.