Gnathymenus arboreus, Assing, 2017

Assing, Volker, 2017, Two new species of Gnathymenus from Ecuador (Coleoptera: Staphylinidae: Paederinae: Dolicaonina), Linzer biologische Beiträge 49 (2), pp. 1023-1028 : 1024-1025

Gnathymenus arboreus nov.sp. ( Figs 1-9 )

T y p e m a t e r i a l: Holotype 3: " ECUADOR - Pastaza, Paya near S. Clara, 950 m, canopy fogging, 30.VII.-1.VIII.2010, leg. Rossi, Bernardi, Torres / Holotypus 3 Gnathymenus arboreus sp. n. det. V. Assing 2017" (cAss). Paratypes: 1633, 22♀♀: same data as holotype (cAss, MNB, QCAZ).

E t y m o l o g y: The specific epithet (Latin, adjective: of a tree) alludes to the habitat where the specimens were collected.

D e s c r i p t i o n: Body length 3.0-4.0 mm; length of forebody 1.7-2.0 mm. Coloration: head and pronotum reddish; elytra and abdomen blackish-brown to blackish, with the posterior margins of segments I-VII and the abdominal apex (segments VIII-X) slightly paler; legs, antennae, and maxillary palpi dark-yellowish to pale-reddish.

Head ( Fig. 1 ) approximately as broad as long, lateral margins behind eyes subparallel in dorsal view; punctation coarse and moderately dense in antero-dorsal portion, sparse and finer in posterior and median dorsal portions; interstices without microsculpture. Eyes approximately 0.7-0.8 times as long as postocular region in dorsal view. Antenna ( Fig. 1 ) approximately 0.9 mm long.

Pronotum ( Fig. 1 ) approximately 1.15 times as long as broad and slightly broader than head, weakly tapering posteriad; midline broadly impunctate, laterally not delimited by a distinct dorsal series of punctures; punctation moderately fine and moderately sparse; interstices without microsculpture.

Elytra ( Fig. 1 ) moderately long, approximately 0.9 times as long as pronotum and with marked humeral angles; punctation sparse, fine and shallow; interstices without microsculpture. Hind wings present. Metatarsomere I longer than II, but shorter than the combined length of metatarsomeres II and III.

Abdomen approximately as broad as elytra; segments III-VI with distinct paratergites; punctation finer and sparser on posterior than on anterior tergites; interstices with distinct transverse microsculpture; posterior margin of tergite VII with palisade fringe; posterior margin of tergite VIII strongly convex.

3: sternite VII ( Fig. 2 ) with an oblong median impression without pubescence, lateral margins of this impression with an oblong cluster of dense modified setae directed diagonally postero-mediad, posterior margin with a small median concavity; sternite VIII ( Fig. 3 ) approximately as long as broad and with deep and narrow posterior incision; aedeagus ( Figs 4-9 ) of somewhat variable size, 0.38-0.45 mm long, subapically with a pair of acute lateral projections best visible in lateral view; 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 the distinctive morphology of the aedeagus and by the distinctive shape and chaetotaxy of the male sternite VII. Based on the similar modifications of the male sternite VII and on the similar general morphology of the aedeagus, G. arboreus appears to be closely allied to G. tungus HERMAN, 1981 ( Ecuador), from which it differs by external characters ( G. tungus : greater body size; head blackish; antennae and maxillary palpi partly infuscate; head tapering posteriorly and with less pronounced posterior angles; pronotum distinctly tapering posteriorly; elytra longer), by the shape and chaetotaxy of the male sternites VII and VIII, and by the shape of the aedeagus ( G. tungus : ventral process apically distinctly bifid in ventral view). For illustrations of G. tungus 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 is situated in the west of Pastaza province, East Ecuador, at an altitude of 950 m. The type specimens were collected by canopy fogging, suggesting that G. arboreus is arboricolous. Some of the specimens are teneral.

Figures

Figs 1-9: Gnathymenus arboreus nov.sp.: (1) forebody; (2) male sternite VII; (3) male sternite VIII; (4-9) aedeagus in ventral and in lateral view. Scale bars: 1: 1.0 mm; 2-3: 0.2 mm; 4-9: 0.1 mm.