Micrillus siamensis, Assing, 2013

Assing, V., 2013, On the Palaearctic and Oriental species of Scymbalium and Micrillus (Coleoptera: Staphylinidae: Paederinae), Linzer biologische Beiträge 45 (2), pp. 1479-1520 : 1497-1499

Micrillus siamensis nov.sp.

( Figs 17-22 , Map 3 )

Type material examined Holotype [apical portions of antennae missing]: " Bangkok / Bangkok / 159 / inconnu au = 158? / Sharp Coll, 1905-313 / Holotypus Micrillus siamensis sp.n., det. V. Assing 2013" ( BMNH).

Etymology: The specific epithet is an adjective derived from Siam, the ancient name of the region where the type locality is situated.

Description: Body length 5.7 mm; length of forebody 3.2 mm. Habitus as in Fig. 17 . Coloration: body reddish; legs and antennae reddish-yellow.

Head ( Fig. 18 ) 1.08 times as long as broad, widest across eyes, narrowed behind eyes; posterior angles rather weakly marked; punctation fine and sparse, somewhat more distinct in lateral and posterior portions; microsculpture very shallow. Eyes somewhat shorter than postocular region in dorsal view. Antennomeres IV-VIII distinctly oblong; VIII nearly twice as long as broad.

Pronotum ( Fig. 18 ) 1.14 times as long as broad and 1.02 times as broad as head; lateral margins subparallel in anterior two fifths and converging in posterior three fifths in dorsal view; posterior margin distinctly concave; punctation extremely fine and very dense.

Elytra ( Fig. 18 ) approximately as long as pronotum; punctation extremely dense and fine; surface almost matt. Hind wings completely developed. Protarsomeres I-IV not dilated. Metatarsomere I nearly as long as the combined length of II-IV.

Abdomen with rather dense and fine punctation; interstices with iridescent microsculpture; posterior margin with palisade fringe.

: sternite VIII ( Fig. 19 ) of similar shape as in M. indicus , with narrow and rather deep posterior incision; aedeagus ( Figs 20-22 ) minute in relation to body size, 0.39 mm long, distinctly asymmetric; apex of ventral process in ventral view with short process on either side and concave in the middle; sclerotized internal structure curved and apically with three finger-shaped processes.

Comparative notes: In general appearance, M. siamensis somewhat resembles M. indicus , to which it is closely related, as can be inferred particularly from the similar male sexual characters (shape of male sternite VIII; minute aedeagus of similar general morphology). It differs, however, by distinctly larger body size, the more oblong head, the finer punctation of the pronotum, and by the shape of the aedeagus.

Distribution: Micrillus siamensis is currently known only from the type locality in Thailand ( Map 3 ).

Figures

Map 3: Distributions of Micrillus indicus (EPPELSHEIM) (triangles), M. nigriceps (CAMERON) (diamonds), M. intermedius (CAMERON) (open and filled circles), and M. siamensis nov.sp. (filled circle) in the Oriental region, based on examined records.

Figs 17-22: Micrillus siamensis nov.sp.: (17) habitus; (18) forebody; (19) male sternite VIII; (20) aedeagus in lateral view; (21) aedeagus in ventral view; (22) aedeagus in dorsal view. Scale bars: 17-18: 1.0 mm; 19-22: 0.2 mm.