Orphnebius biformis, Assing, 2016

Assing, Volker, 2016, On some Lomechusini of the Palaearctic and Oriental regions (Coleoptera: Staphylinidae: Aleocharinae), Beiträge Zur Entomologie = Contributions to Entomology 66 (1), pp. 13-111 : 59-60

Orphnebius biformis spec. nov.

( Figs 19–20 , 42–43 , 274–278 )

Type material: Holotype ♂: “ Sumatra: Jambi pr.: Kerinci, Seblat N.P. : 7 km E Kayuaro: Mt. Tujuh , 1750± 250 m, 1°45'S, 101°25'E, Dembický leg., 25.ii.–2.iii.2003 / Holotypus ♂ Orphnebius biformis sp. n., det. V. Assing 2015” ( NHMB).

Paratypes: 2 ♀♀: same data as holotype ( NHMB, cAss) .

Etymology: The specific epithet (Latin, adjective) alludes to the hypothesized pronounced sexual dimorphism of the eyes and the antennae.

Description: Body length 4.3–4.8 mm; length of forebody 1.9–2.0 mm. Coloration: head dark-brown with the clypeus yellowish-red; pronotum dark-brown; elytra dark-brown with the anterior and sutural portions more or less extensively paler; abdomen reddish-yellow; legs yellowish; antennae dark-brown with antennomeres I–IV reddish-yellow; maxillary palpi reddish-yellow with yellowish terminal palpomere.

Head ( Figs 42–43 ) sexually dimorphic, strongly transverse, approximately 1.3 (female) and 1.4 (male) times as broad as long, respectively; laterally with few scattered and very fine punctures; remainder of dorsal portion extensively impunctate; interstices without microsculpture. Eye size sexually dimorphic, in male enormous and strongly bulging, covering all of lateral margins, in female less large and less convex. Antenna ( Figs 19–20 ) sexually dimorphic, approximately 1.6 and 1.3 mm long in male and in female respectively, distinctly incrassate, and distinctly asymmetric; antennomere IV small and moderately transverse; antennomere V moderately transverse and weakly transverse in female, strongly transverse and strongly asymmetric in male; antennomeres VI–X of gradually and distinctly increasing width, increasingly asymmetric, and increasingly transverse, more transverse in male than in female; X more than twice as wide as long; XI elongate, approximately three times as long as broad (male) or twice as long as broad (female).

Pronotum ( Figs 42–43 ) moderately transverse, 1.21– 1.26 times as broad as long and approximately 0.95 (male) or 1.1 times (female) as broad as head, moderately strongly convex in cross-section; posterior angles nearly obsolete; disc with a median pair of punctures, otherwise practically impunctate; lateral margins each with three long and erect black setae.

Elytra ( Figs 42–43 ) approximately 0.7 times as long as pronotum; suture strongly gaping posteriorly; punctation sparse and very fine; pubescence long and pale. Hind wings fully developed. Metatarsomere I approximately as long as, or slightly longer than, the combined length of II and III.

Abdomen: paratergites moderately elevated and moderately sharply edged; tergites III–VI each with two lateral setiferous punctures on either side, tergite VI additionally with median pair of punctures at posterior margin; tergites IV–V with or without median pair of setiferous punctures at posterior margin; tergite VII with non-setiferous punctation in posterior two-thirds and with eight setiferous punctures near posterior margin, posterior margin with palisade fringe; tergite VIII ( Fig. 275 ) with two transverse rows of black setae posteriorly and with broadly truncate posterior margin; sternite VIII with broadly and weakly convex posterior margin.

♂: hemi-tergites IX and tergite X with extremely dense and long pubescence; median lobe of aedeagus ( Figs 277–278 ) 0.51 mm long and of distinctive shape; internal sac without strongly sclerotized structures; paramere ( Fig. 274 ) approximately 0.5 mm long, condylite very short and broad.

♀: abdominal segments IX–X of similar shape and chaetotaxy as in O. hauseri ; spermatheca as in Fig. 276 .

Comment: The holotype male is distinguished from the two female paratypes by the different shape of the antennae, the more transverse head (broader than the pronotum), and the distinctly larger and more convex eyes. These differences, however, are interpreted as sexual dimorphism, not only because the three specimens were collected in the same locality on the same date, but also because they are extremely similar in other respects and because a pronounced sexual dimorphism (of the antennae) was also observed in the closely related O. reductus .

Comparative notes: Based on the modifications of the abdominal segments IX–X, the shape and chaetotaxy of tergite and sternite VIII, the pronounced sexual dimorphism of the antennae, the absence of strongly sclerotized structures in the internal sac of the aedeagus, and particularly on the very similar morphology of the spermatheca, this species is closely allied to O. reductus , from which it differs by different coloration, a pronounced sexual dimorphism of the head (including the eyes), by the shape of the male and female antennae, the coloration, and the primary sexual characters, particularly the completely different shape of the median lobe and the parameres of the aedeagus.

None of the three Orphnebius species previously recorded from Sumatra ( O. laticeps CAMERON, 1925 , O. ophthalmicus CAMERON, 1936 , O. harpagonum PACE, 2010 ) is similar to O. biformis .

Distribution and natural history: The type locality is situated in Sumatera Barat, Sumatra, Indonesia, at an altitude of approximately 1750 m.

Figures

Figs 1–26. Antenna (1–21) and forebody (22–26) of Orphnebius spp. of the O. hauseri group: spinans (1, 23), cernens (2, 24), lunatus (3, 25), bakeri (4, 26), breviceps (5), extensus (6), serratus (7), integer (8), bicuspis, Laos (9), bicuspis, NE India (10), fusicollis (11), retunsus (12), fodens (13), opticus (14), dilatatus (15), fuscapicalis (16), grandicollis (17, 22), reductus (18), biformis, male (19), biformis, female (20), effeminatus (21). Scale bars: 22–26: 1.0 mm; 1–21: 0.5 mm.

Figs 40–53. Forebody (40–50), abdomen (51), and antenna (52–53) of Orphnebius spp. of the O. hauseri group (40–49) and of the subgenus Deroleptus (50–53): opticus (40), effeminatus (41), biformis, male (42), biformis, female (43), bicuspis, NE India (44), retunsus (45), fusicollis (46–47), fodens (48), reductus (49), niger (50–52), siamensis (53). Scale bars: 1.0 mm.

Figs 258–276. Orphnebius bicuspis (258–260; 258–259: India), O. opticus, syntype (261–262), O. fusicollis (263–268), O. reductus (269–273), and O. biformis (274–276): median lobe of aedeagus in lateral and in ventral view (258–259, 263–264, 269–270); tergite VIII (260, 261, 266, 272, 275); spermatheca (262, 268, 273, 276); paramere (265, 271, 274); anteromedian portion of sternite VIII (267). Scale bars: 0.2 mm.

Figs 277–295. Orphnebius biformis (277–278), O. retunsus (279–282), O. fodens (283–286), O. effeminatus (287–292), and O. multimpressus (293–295): median lobe of aedeagus in lateral and in ventral view (277–280, 283–284, 287–288, 293–294); paramere (281, 285, 289, 295); tergite VIII (282, 286, 290); median portion of tergite VIII (291); male tergites IX-X (292). Scale bars: 0.2 mm.