Micrillus virgatus

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 : 26-27

Micrillus virgatus ASSING, 2018 M a t e r i a l e x a m i n e d: Cambodia: 4♂♂, 5♀♀, Kampong Chhnang prov., Rolea B'ier

distr., Toulkrolanh vill., 12°14'N, 104°40'E, light trap, 7.XI.2018, leg. Rossi (cAss); 11♂♂, 15♀♀, Kampong Chhnang prov., Phum Toul Ompel, shore of branch of Tonle Sap Lake , 12°14'N, 104°41'E, 4.+ 7.XI.2018, leg. Rossi (cAss) ; 4♂♂, 1♀, Kampong Chhnang prov., Rolea B'ier distr., Toekchenh vill., 12°08'N, 104°38'E, light trap, 6.XI.2018, leg. Rossi (cAss) .

C o m m e n t: This recently described species appears to be rather common in Cambodia and has also been reported from one locality in Thailand ( ASSING 2018).

Micrillus rossianus nov.sp. ( Figs 1-7 ) T y p e m a t e r i a l: Holotype ♂: ̎ CAMBODIA - Kampong Chhnang prov., Rolea B'ier

distr., Toekchenh vill., 12°07'36''N, 104°38'05''E, light trap, 6.XI.2018, leg. W. Rossi / Holotypus ♂ Micrillus rossianus sp. n., det. V. Assing 2019̎ (cAss). Paratypes: 1♂: same data as holotype (cAss); 2♂♂, 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: This species is dedicated to Walter Rossi (L'Aquila), whose material the present study is largely based on and who collected all the new species.

D e s c r i p t i o n: Large species; body length 9.0- 10.3 mm; length of forebody 5.1- 5.3 mm. Habitus as in Fig. 1 . Coloration: body pitchy-reddish with the abdomen sometimes darker; legs pale-brown with the tibiae usually somewhat darker; antennae reddish with the apices of the apical antennomeres whitish-yellow (owing to very dense pale pubescence).

Head ( Fig. 2 ) approximately as broad as long or weakly transverse, of subquadrate shape, and weakly convex in cross-section; integument dorsally with dense and fine punctation bearing short to moderately long, fine, pale, and sub-erect setae, and with scattered macropunctures bearing long and black erect setae in lateral and anterior dorsal portions; median and anterior dorsal portions with sparse micropunctation; interstices with fine transverse microsculpture. Eyes 0.5-0.7 times as long as postocular region in dorsal view. Antenna long and very slender, nearly 4 mm long; antennomeres IV-X distinctly oblong, of gradually decreasing length, and decreasingly oblong; IV approximately three times as long as broad; X less than twice as long as broad. Maxillary palpus slender, apical palpomere of slender conical shape, slightly more than half as long as maxillary palpomere III.

Pronotum ( Fig. 2 ) approximately 1.05 times as long as broad and approximately as broad as head; lateral margins straight, weakly converging posteriad in dorsal view; posterior margin broadly and weakly concave; punctation very fine and dense; on either side of middle with dorsal series each composed of 4-7 macropunctures; midline with or without very indistinct and narrow impunctate median band; interstices without microsculpture.

Elytra ( Fig. 2 ) approximately as long as pronotum, or nearly so; punctation extremely fine, extremely dense, and somewhat asperate, rendering the surface matt. Hind wings fully developed. Protarsomeres I-IV distinctly dilated. Metatarsomere I slightly longer than the combined length of II and III.

Abdomen ( Fig. 1 ) approximately as broad as elytra; tergites with very fine and extremely dense micropunctation bearing short and pale depressed pubescence and with macropunctures bearing very long black setae at posterior margins and on disc; posterior margin of tergite VII with palisade fringe; tergite X and sternite IX very small; posterolateral processes of segment IX approximately three times as long as tergite X.

♂: posterior excision of sternite VIII concave ( Fig. 3 ); aedeagus ( Figs 4-7 ) 0.80-0.85 mm long, symmetric, and weakly sclerotized; internal sac with dark membranous structure, but without spine-shaped sclerites.

C o m p a r a t i v e n o t e s: Micrillus rossianus is currently the largest known representative of the genus. It is additionally distinguished from the sympatric M. virgatus by darker coloration (especially of the legs), denser and more distinct punctation of the pronotum, and by a smaller aedeagus with a differently shaped apex and without a rod-shaped structure in the internal sac. The new species differs from M. badius (MOTSCHULSKY, 1858) ( India, Myanmar) and M. nepalensis ( ASSING, 2013) ( Nepal) by larger size, a broader and less oblong pronotum with denser and more distinct micropunctation ( M. badius : pronotum approximately 1.1 times as long as broad), shorter elytra ( M. badius : elytra longer than pronotum), and a larger aedeagus ( M. badius and M. nepalensis: aedeagus approximately 0.7 and 0.6 mm long, respectively). For comparison, the aedeagus of M. badius is illustrated in Figs 8-9 . For figures of M. nepalensis see ASSING (2013).

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: The known distribution is confined to two localities in Cambodia. All the type specimens were collected at light traps together with several other Micrillus species, including M. virgatus .

Figures

Figs 1-9: Micrillus rossianus (1-7) and M. badius (8-9): (1) habitus; (2) forebody; (3) male sternite VIII; (4-9) aedeagus in lateral and in ventral view. Scale bars: 1-2: 1.0 mm; 3: 0.5 mm; 4-9: 0.2 mm.