On some Lomechusini of the Palaearctic and Oriental regions (Coleoptera: Staphylinidae: Aleocharinae) Author Assing, Volker text Beiträge Zur Entomologie = Contributions to Entomology 2016 2016-12-20 66 1 13 111 https://www.contributions-to-entomology.org/article/view/1904 journal article 2419 10.21248/contrib.entomol.66.1.13-111 d2933fad-1cac-4a5a-a558-2633f8314541 0005-805X 6421171 Orphnebius opticus CAMERON, 1946 ( Figs 14 , 40 , 261–262 ) Orphnebius ( Mesocephalobius ) opticus CAMERON, 1946: 692 . Type material : Syntype ♀ : “62249 / Siam , Renong / Doherty / Orphnebius opticus Cam. Type / Fry Coll. 1905.100. / Type / Syntypus ♀ Orphnebius opticus Cameron , rev. V. Assing 2015” ( BMNH ) . Comment : The original description of O. opticus is based on an unspecified number of syntypes from “ Siam : Renong” ( CAMERON 1946 ). The sole syntype found in the collections at the BMNH is a female and consequently not designated as the lectotype . Redescription : Body length 5.7 mm ; length of forebody 2.5 mm . Coloration: head and pronotum brown, with the frons, the clypeus, and the mouthparts yellowishred, and the pronotal margins narrowly reddish; elytra dark-yellowish with the postero-lateral portions extensively brown; abdomen and legs dark-yellowish; antennae distinctly bicoloured, with antennomeres V–XI darkbrown and antennomeres I–IV reddish; maxillary palpi reddish with the apical palpomere yellowish. Head ( Fig. 40 ) strongly transverse, 1.3 times as broad as long; posterior angles obsolete; punctation extremely fine, barely visible, and very sparse; median and posterior dorsal portions extensively impunctate; interstices without microsculpture. Eyes very large, nearly reaching posterior margin, and more than twice as long as distance from posterior margin of eye to posterior constriction of head in dorsal view. Antenna ( Fig. 14 ) 1.6 mm long, distinctly incrassate, and distinctly asymmetric; antennomere IV small and approximately as long as broad; antennomere V broader than IV and distinctly transverse; antennomeres VI–X strongly asymmetric, of gradually increasing width, and strongly transverse, approximately twice as broad as long; XI longer than the combined length of IX and X, but shorter than the combined length of VIII–X. Pronotum ( Fig. 40 ) 1.25 times as broad as long and 1.05 times as broad as head, moderately convex in crosssection; lateral and posterior margins together nearly forming a semi-circle, posterior angles completely obsolete; disc with a median pair of punctures, otherwise impunctate; margins with additional punctures; lateral margins with at least two long and erect black setae anteriorly. Elytra ( Fig. 40 ) approximately 0.8 times as long as pronotum; punctation sparse and fine; pubescence long, pale, and depressed to sub-erect. Hind wings fully developed. Metatarsomere I nearly as long as the combined length of II–IV. Abdomen narrower than elytra; tergites III–VI each with two lateral punctures bearing black setae on either side; tergite VII with dense non-setiferous punctation in posterior two-thirds, at posterior margin with a transverse row of eight setiferous tubercles, posterior margin with distinct palisade fringe; tergite VIII ( Fig. 261 ) weakly serrate, with eight setiferous tubercles at posterior margin, posterior margin broadly convex. ♂ : unknown. ♀ : spermatheca as in Fig. 262 . Comparative notes : Among the revised species of the O. serratus subgroup with a serrate posterior margin of tergite VIII, this species is characterized by a less distincty quadrangular head, pale coloration, the antennal morphology, the pronotum being slightly broader than the head, the weakly serrate posterior margin of tergite VIII, and the shape of the spermatheca. Distribution : The type locality, today Ranong , is situated in southern Thailand .