Osoriellus triangulatus, Irmler, 2014

Irmler, Ulrich, 2014, The Neotropical species of the genus Osoriellus FAGEL, 1959 (Coleoptera: Staphylinidae: Osoriinae), Beiträge Zur Entomologie = Contributions to Entomology 64 (2), pp. 231-354 : 289-290

Osoriellus triangulatus n. sp.

( Figs 71 A-C, 98E)

Type material: Holotype, male: Venezuela: Prov. Falcón, Cogollal (68°49.64'W, 10°54.96'N), grazed grassland with logs, 19.3.1998, leg. C. Schmidt ( UIC).

Diagnosis: Among the intermediate sized species between 4 and 5 mm, O. triangulatus is characterised by the strongly convergent pronotum. In this respect, it can be confused with O. tuxtlae . But in contrast to O. tuxtlae , the pronotum is still more convergent and the surface is matt due to the distinct microsculpture, whereas the pronotum of O. tuxtlae has no microsculpture and a polished surface.

Description: Length: 4.5 mm. Colouration: Dark brown; legs and antennae lighter brown.

Head: 0.63 mm long, 0.92 mm wide; eyes slightly prominent and slightly shorter than temples; sides of fore-head shortly convergent to obtuse anterior angles; front edge of clypeus even; clypeal angles produced to short granules; setiferous punctation coarse and dense; punctation on midline sparser; coriaceously punctate; close to eyes, punctures partly granulate; at base of antennae, small area impunctate; netlike microsculpture dense and deep except on impunctate area at base of antennae without microsculpture; surface of vertex matt.

Antennae slightly longer than head; second antennomere oval and slightly longer than conical third; antennomeres 4 to 6 as wide as preceding antennomeres, but quadrate; antennomeres 7 to 10 wider than preceding antennomeres and increasing in width; antennomere 7 approximately quadrate; antennomere 10 slightly wider than long.

Pronotum: 0.88 mm long, 0.92 mm wide; widest at obtusely rounded anterior angles; strongly convergent to posterior angles; close to posterior angles more strongly convergent than in anterior half; lateral margin fine; in posterior half slightly wider than in anterior half; in dorsal aspect, not visible close to anterior angles; setiferous punctation coarse; in irregular rows; narrow midline impunctate; wider at anterior edge than at posterior edge; within rows, interstices between punctures shorter than diameter of punctures; between rows, interstices between punctures at least as wide as diameter of punctures; between coarse punctures with sparse micro-punctation; netlike microsculpture weaker and wider than on head; surface slightly shiny.

Elytra: 1.08 mm long, 0.95 mm wide; with rows of setiferous punctures on deep coriaceous ground-sculpture; surface matt.

Abdomen with dense and coarse setiferous punctation except impunctate dorsal midline; microsculpture weak, but dense; surface matt.

Protibia: 0.55 mm long, 0.18 mm wide; 10 spines on outer edge; WLR: 2.8; in posterior aspect, comb at inner edge visible throughout its total length; posterior face with dense setation.

Aedeagus rectangularly angulate; apical lobe long; apex obtusely rounded.

Etymology: The specific name refers to the triangular shape of the pronotum.

Figures

Fig. 68-72: Osoriellus-s. str.-group: Osoriellus boliviensis (68), O. minor (69), O. rugipennis (70), O. triangulatus (71), O. franckei (72); antenna (A), protibia (B), aedeagus in lateral aspect (C); scale bar: 0.1 mm.