Micrillus variceps, Assing, 2019

Assing, Volker, 2019, A revision of Palaearctic and Oriental Scymbalium and Micrillus IV. The Iauna of Cambodia (Coleoptera, Staphylinidae, Paederinae), Linzer biologische Beiträge 51 (1), pp. 21-31 : 28-29

Micrillus variceps nov.sp. ( Figs 10-17 ) T y p e m a t e r i a l: Holotype ♂: ̎ CAMBODIA - Siem Reap province, N Siem Reap city,,

13°26'29''N, 103°52'25''E, light trap, 12-13.XI.2018, leg. W. Rossi / Holotypus ♂ Micrillus variceps sp. n., det. V. Assing 2019̎ (cAss). Paratypes: 1♂, 1♀: ̎ CAMBODIA - Kampong Chhnang prov., Phum Toul Ompel, shore of branch of Tonle Sap Lake , 12°14'N, 104°41'E, 4.+ 7.XI.2018, leg. W. Rossi ̎ (cAss); 2♀♀: ̎ CAMBODIA - Kampong Chhnang prov., Kampong Chhnang env., Toul Ompel , 12°14'14''N, 104°41'15''E, light trap, 19+ 21.V.2018, leg. W. Rossi ̎ (cAss) ; 2♀♀: ̎ CAMBODIA - Banteay Meanchey prov., Mean Chey University campus, 13°34'45''N, 102°55'44''E, light trap, 1.XI.2018, leg. W. Rossi ̎ (cAss) ; 1♀: ̎ CAMBODIA - Kampong Chhnang prov., Rolea B'ier distr., Toulkrolanh vill., 12°13'31''N, 104°39'50''E, light trap, 7.XI.2018, leg. W. Rossi ̎ (cAss) .

E t y m o l o g y: The specific epithet (Latin, adjective) alludes to the remarkably variable size and shape of the head.

D e s c r i p t i o n: Body length 7.0- 8.5 mm; length of forebody 4.0- 4.7 mm. Habitus as in Fig. 10 . Coloration variable: head dark-brown to black; pronotum reddish to black; elytra reddish with the anterior portion more or less distinctly and more or less extensively infuscate; abdomen reddish with the discs of tergites III-VI slightly darker, to blackish with the apex (segments VII-X) reddish to reddish-brown; legs pale-reddish; antennae reddish.

Head ( Figs 11-12 ) of very variable shape, relatively larger in larger than in smaller specimens, 1.0-1.1 times as long as broad, broadest across or behind eyes, with lateral margins behind eyes weakly diverging, subpararallel, or smoothly curving towards posterior constriction; punctation moderately dense and moderately coarse; median and anterior dorsal surface sparsely punctate or impunctate; interstices with fine transverse microsculpture. Eyes distinctly shorter than postocular region, strongly convex in smallheaded and weakly convex in large-headed specimens. Antenna 3.1-3.3 mm long; antennomeres IV approximately 2.5 times as long as broad, V-X of gradually decreasing length and decreasingly oblong, and X weakly oblong. Apical palpomere of maxillary palpus of slender conical shape, approximately half as long as maxillary palpomere III.

Pronotum ( Figs 11-12 ) slender, 1.17-1.24 times as long as broad and 0.85 (large specimens) to 0.97 times (small specimens) as broad as head, weakly tapering posteriad; punctation fine and dense, on either side of midline with a dorsal series composed of 6-8 coarser punctures; midline narrowly impunctate; interstices without microsculpture.

Elytra ( Figs 11-12 ) 0.87-0.90 times as long as pronotum; punctation very dense, fine, and somewhat asperate. Hind wings fully developed. Protarsomeres I-IV not dilated. Metatarsomere I slightly longer than the combined length of II and III.

Abdomen ( Fig. 10 ) narrower than elytra; punctation dense and fine, somewhat less dense on tergites VII and VIII; interstices with fine transverse microsculpture; posterior margin of tergite VII with palisade fringe; tergite X and sternite IX small; postero-lateral processes of segment IX circular in cross-section and nearly three times as long as tergite X.

♂: posterior excision of sternite VIII rather deep and large ( Fig. 17 ); aedeagus ( Figs 13-

16) 0.65-0.70 mm long, compact, nearly symmetric, and weakly sclerotized; internal sac with a large dark membranous structure.

C o m p a r a t i v e n o t e s: This species is separated from other Micrillus species by the characters indicated in the group diagnosis above and by the morphology of the aedeagus. It is additionally distinguished from the syntopic, similarly sized, and sometimes similarly coloured M. kongi by a more slender, posteriorly weakly tapering, less densely punctured, and distinctly more glossy pronotum, coarser punctation of the head, and a much deeper posterior excision of the male sternite VIII.

D i s t r i b u t i o n a n d n a t u r a l h i s t o r y: Micrillus variceps is currently known from four localities in Siem Reap, Kampong Chhnang, and Banteay Meanchey provinces, Cambodia. Most of the specimens were collected with light traps, together with various other Micrillus species.

Figures

Figs 10-16: Micrillus variceps (10-11, 13-14): holotype; 12, 15-16: male paratype): (10) habitus; (11-12) forebody; (13-16) aedeagus in lateral and in ventral view. Scale bars: 10-12: 1.0 mm; 13- 16: 0.2 mm.

Figs 17-24: Micrillus variceps (17) and M. bispinosus (18-24): (17, 20) male sternite VIII; (18) habitus; (19) forebody; (21) abdominal segments IX-X; (22-24) aedeagus in lateral and in ventral view. Scale bars: 18-19: 1.0 mm; 17, 20-21: 0.5 mm; 22-24: 0.2 mm