Orphnebius (Deroleptus) biimpressus, 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 : 74

Orphnebius (Deroleptus) biimpressus spec. nov.

( Figs 67 , 104, 108, 113–114 , 362–364 )

Type material: Holotype ♀: “ Sumatra (Aceh), Ketambe, Leuser Nat. Park , 450 m, 26.II.–1.III.1991, Bocák & Bocáková lgt. / Holotypus ♀ Orphnebius biimpressus sp. n., det. V. Assing 2015” ( NHMB).

Etymology: The specific epithet (Latin, adjective) alludes to the lateral impression on each elytron.

Description: Body length 4.8 mm; length of forebody 2.1 mm. Coloration: head blackish-brown; pronotum and elytra dark-brown; abdomen reddish-brown with segment VII dark-brown; legs reddish; antennae brown with antennomeres II–III and the apex of antennomere XI reddish; maxillary palpi reddish with the apical palpomere yellowish.

Head ( Fig. 104 ) strongly transverse, 1.4 times as broad as long; punctation in lateral portions sparse and fine; median and posterior dorsal portions extensively impunctate; interstices without microsculpture. Eyes enormous and strongly bulging, nearly reaching posterior margin of head. Antenna ( Fig. 67 ) 1.5 mm long and not distinctly incrassate; antennomere IV approximately as long as broad; antennomeres V–X weakly transverse, gradually and very weakly increasing in width; X much less than 1.5 times as broad as long; XI barely as long as the combined length of IX and X.

Pronotum ( Fig. 104 ) 1.26 times as broad as long and 0.9 times as broad as head, moderately convex in crosssection, of inversely trapezoid shape; maximal width across anterior angles; lateral margins nearly straight in dorsal view; posterior angles moderately marked; in posterior portion with a transverse median impression; disc with scattered and very indistinct punctation, nearly impunctate. Elytra ( Figs 104, 108 ) approximately 1.25 times as long as, and much broader than pronotum; laterally with an oblong impression, this impression externally delimited by an oblong elevation; punctation moderately dense and rather fine; interstices with distinct microreticulation; pubescence short, pale, and depressed. Hind wings present. Legs of moderate length and moderately slender; metatibia 1.0 mm long; metatarsus little more than 0.8 times as long as metatibia; metatarsomere I much longer than the combined length of II and III.

Abdomen ( Figs 113–114 ): sternites III–V not distinctly modified; tergites IV–VI each with a lateral tubercle on either side; tergites III–VI with shallow microsculpture anteriorly and each with two lateral setiferous punctures on either side; tergite VI with a pair of small tubercles at posterior margin; tergite VII with dense non-setiferous punctation, except along anterior margin; tergite VIII ( Fig. 362 ) transverse, anteriorly with a pair of extensive clusters of numerous gland openings; posterior margin distinctly serrate and broadly excised; sternite VIII ( Fig. 363 ) strongly transverse, laterally with a cluster of several very stout setae inserting in sclerotized projections, posterior margin nearly truncate in the middle.

♂: unknown.

♀: spermathecal capsule ( Fig. 364 ) rather large and slender, 0.39 mm long, and of distinctive shape.

Comparative notes and comment: Orphnebius biimpressus is characterized by the slender, weakly incrassate antennae, enormous eyes, the transverse impression on the pronotum, the presence of microreticulation on the elytra, the lateral impressions and elevations of the elytra, unmodified abdominal sternites III–V, the presence of a pair of tubercles at the posterior margin of tergite VI, the anterior pair of extensive clusters of gland openings on tergite VIII, and by the distinctive shape of the spermatheca. It additionally differs from O. laticeps , the only other representative of Deroleptus known from Sumatra, by larger body size ( O. laticeps : length of forebody 1.7 mm), the darker antennomere I ( O. laticeps : antennomere I pale-reddish), the relatively smaller and inversely trapezoid pronotum, much finer and sparser punctation of the elytra, much paler coloration of the abdomen and the legs, and the deeper posterior excision of tergite VIII.

Distribution and natural history: The type locality is situated in the Gunung Leuser National Park in Aceh province, North Sumatra, Indonesia. The holotype was collected at an altitude of 450 m.

Figures

Figs 54–83. Antenna (54–69), forebody (70–73), abdomen (74–76), abdominal segments III–V (77, 81), lateral portion of abdominal segments III–V (78, 82), tergites VI–VII (79, 83), and hind leg (80) of Orphnebius spp. of the subgenus Deroleptus: discrepans (54, 73, 75), triapicalis (55, 71, 76), gracilior (56, 72, 77–80), sexcarinatus (57, 81–83), spoliatus (58), cultellatus (59), septemcuspis (60), vates (61), tortus (62), baccillatus (63), carinatus (64), dispar (65), laticeps (66), biimpressus (67), ulcerosus (68), falagrioides (69), siamensis (70, 74). Scale bars: 70–83: 1.0 mm; 54–69: 0.5 mm.

Figs 102–118. Forebody (102–108), abdomen (109–110, 112–113, 115), lateral portion of abdominal segments III–V/ VII (111, 117–118), and tergites VII(–VIII) (114, 116) of Orphnebius spp. of the subgenus Deroleptus: carinatus (102, 117), laticeps (103, 112), biimpressus (104, 108, 113–114), ulcerosus (105, 115–116), dispar (106, 110–111), falagrioides (107, 118), baccillatus (109). Scale bars: 102–110, 112–113, 115, 117–118: 1.0 mm; 111, 114, 116: 0.5 mm

Figs 359–378. Orphnebius laticeps (359–361), O. biimpressus (362–364), O. ulcerosus (365–369), O. falagrioides (370–372), and Drusilla bifida (373–378): tergite VIII (359, 362, 368, 370, 374); female sternite VIII (360, 363, 371); spermatheca (361, 364, 372); median lobe of aedeagus in lateral and in ventral view (365–366, 376–377); paramere (367); male sternite VIII (369, 375); posteromedian portion or head (373); apex of ventral process of aedeagus (378). Scale bars: 359–372, 374–377: 0.2 mm; 373, 378: 0.1 mm.