Gnathymenus abscisus, Assing, 2015

Assing, Volker, 2015, New species and additional records of Dolicaonina from Ecuador (Coleoptera: Staphylinidae: Paederinae), Linzer biologische Beiträge 47 (2), pp. 1119-1132 : 1128

Gnathymenus abscisus nov.sp. ( Figs 25-31 )

T y p e m a t e r i a l: Holotype 3: " ECUADOR - Zamora Chinchipe, Estacion Cientifica S. Francisco, 3°59'S, 79°05'W, 1900m, 10-14.VIII.2014, Rossi / Holotypus 3 Gnathymenus abscisus sp. n. det. V. Assing 2014" (cAss). Paratypes: 333, 3♀♀: same data as holotype (cAss).

E t y m o l o g y: The specific epithet is the past participle of the Latin verb abscidere (to cut off) and alludes to the basally conspicuously truncate sclerotized portion of the aedeagus.

D e s c r i p t i o n: Small species; body length 2.7-3.2 mm; length of forebody 1.5-1.6 mm. Coloration: body bicoloured; head and pronotum reddish; elytra and abdomen blackish, with the terminal abdominal segments (VIII-X) slightly paler; legs, antennae, and maxillary palpi yellowish.

Head ( Fig. 25 ) approximately as long as broad or weakly oblong, widest across eyes, tapering behind eyes; dorsal surface with fine and sparse punctation, median dorsal portion nearly impunctate; interstices without microsculpture. Eyes rather large and convex, approximately as long as postocular region in dorsal view. Antenna approximately 0.7 mm long.

Pronotum ( Fig. 25 ) relatively slender, approximately 1.25 times as long as broad and as broad as head, widest in anterior half and distinctly tapering posteriad; the broadly impunctate midline laterally delimited by a more or less irregular dorsal series of relatively coarse punctures on either side; lateral portions with fine and very sparse punctation; interstices without microsculpture.

Elytra ( Fig. 25 ) long, approximately as long as pronotum and with marked humeral angles; punctation fine and rather sparse; interstices without microsculpture. Hind wings present. Metatarsomere I shorter than II.

Abdomen slightly narrower than elytra; segments III-VI with distinct paratergites; punctation moderately fine and moderately sparse on tergites III-VI, very sparse on tergites VII-VIII; interstices with fine transverse microsculpture; posterior margin of tergite VII with palisade fringe; posterior margin of tergite VIII moderately convex ( Fig. 26 ).

3: sternites V and VI flattened in the middle; sternite VII ( Figs 27-28 ) approximately 1.2 times as broad as long, without distinct postero-median impression and with unmodified pubescence, posterior margin with shallow concavity in the middle; sternite VIII ( Fig. 29 ) approximately 1.25 times as long as broad and with deep median incision; aedeagus ( Figs 30-31 ) strongly asymmetric and of conspicuous morphology, sclerotized portion approximately 0.48 mm long; basal portion unsclerotized, sclerotized portion seemingly cut off basally (truncate); parameres completely reduced.

C o m p a r a t i v e n o t e s: This species is distinguished from all its congeners particularly by its distinctive male sexual characters. Using the key to females in HERMAN (1981), G. abscisus would key out at couplet 85, together with G. angulus HERMAN, 1981 from Ecuador, from which it is distinguished by smaller body size ( G. angulus : 3.5 mm), the much darker elytra and abdomen ( G. angulus : dark reddishbrown), the less transverse male sternite VII with a differently shaped posterior margin, and by the completely different shape of the aedeagus. For illustrations of the male sexual characters of G. angulus see HERMAN (1981).

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 type locality and the circumstances of collection are identical to those of G. crucifer and G. stipulatus .

Figures

Figs 25-31: Gnathymenus abscisus nov.sp.: (25) forebody; (26) male tergite VIII; (27) male sternite VII; (28) postero-median portion of male sternite VII; (29) male sternite VIII; (30-31) aedeagus in lateral (internal structure extruded) and in ventral view. Scale bars: 25: 0.5 mm; 26-27, 29-31: 0.2 mm; 28: 0.1 mm.