Orphnebius (Deroleptus) siamensis CAMERON, 1946

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 : 63-64

Orphnebius (Deroleptus) siamensis CAMERON, 1946 ( Figs 53 , 70, 74 , 299–303 )

Orphnebius (Mesocephalobius) siamensis CAMERON, 1946: 693 .

Type material examined: Holotype ♂: “62250 / Siam, Renong / Doherty / Orphnebius siamensis Cam. Type / Fry Coll. 1905.100. / Type / Holotypus ♂ Orphnebius siamensis Cameron , rev. V. Assing 2015” ( BMNH).

Comment: The original description is based on a unique male from “ Siam: Renong” ( CAMERON 1946).

Redescription: Body length 5.4 mm; length of forebody 2.3 mm. Coloration: head and pronotum blackishbrown; elytra pale-brown, with the postero-lateral portions extensively dark-brown; abdomen reddish, with segments VI–VII slightly darker; legs: pro- and mesofemora brown, metafemora bicoloured with the basal half yellowish and the apical half brown, tibiae and tarsi pale-reddish; antennae blackish-brown with antennomeres I–II, the base of III, and the apex of XI reddish; maxillary palpi reddish.

Head ( Fig. 70 ) 1.33 times as broad as long; posterior angles weakly marked; lateral dorsal portions with moderately scattered fine punctation; median dorsal portion extensively impunctate; interstices without microsculpture. Eyes large, approximately as long as the distance from posterior margin of eye to posterior constriction of head in dorsal view. Antenna ( Fig. 53 ) 1.9 mm long and slender; antennomeres IV–VI distinctly oblong, VII approximately as long as broad, VIII–X weakly transverse, and XI approximately as long as the combined length of IX and X.

Pronotum ( Fig. 70 ) 1.15 times as broad as long and approximately as broad as head, strongly convex in crosssection; anterior margin strongly concave in the middle; lateral margins nearly straight and subparallel in dorsal view; disc with a median pair of punctures, otherwise practically impunctate; near lateral margins with three long and erect black setae anteriorly.

Elytra ( Fig. 70 ) approximately 0.85 times as long as pronotum; punctation fine and sparse; pubescence long, pale, and depressed to sub-erect. Hind wings present. Metatarsomere I approximately as long as the combined length of II–IV.

Abdomen ( Fig. 74 ) approximately as broad as elytra; tergite VI at posterior margin with a tubercle on either side of the middle, laterally with a long carina on either side; tergite VII with coarse sculpture, at posterior margin with some setiferous punctures; tergite VIII ( Fig. 302 ) with coarsely granulose setiferous punctation, with a transverse band of numerous gland openings in anterior half, and with a distinctly tridentate posterior margin; sternite VIII ( Fig. 303 ) with a transverse band of gland openings in anterior half, with convexly produced posterior margin, and laterally with a cluster of stout black setae on either side.

♂: median lobe of aedeagus ( Figs 299–300 ) 0.55 mm long and slender; ventral process dorso-ventrally depressed and apically tricuspidate in ventral view; paramere ( Fig. 301 ) 0.5 mm long and of distinctive shape.

♀: unknown.

Comparative notes: Among the species of the O. niger group, O. siamensis is characterized by the slender antennae and particularly by the shapes of the median lobe and the parameres of the aedeagus.

Distribution and natural history: The type locality is situated in the vicinity of Ranong, South Thailand. Additional data are not available.

Figures

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 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 296–316. Orphnebius niger (296–298), O. siamensis (299–303), O. discrepans (304–306), O. triapicalis (307–310), O. gracilior (311–313), and O.sexcarinatus (314–316): tergite VIII (296, 302, 310, 311, 314); female sternite VIII (297, 312, 315); spermatheca (298, 313, 316); median lobe of aedeagus in lateral and in ventral view (299–300, 304–305, 307–308); paramere (301, 306, 309); male sternite VIII (303). Scale bars: 0.2 mm.