Osoriellus frater ( LYNCH, 1884 ) 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 : 268-269

Osoriellus frater ( LYNCH, 1884) new combination

( Figs 73A , 97F )

Osorius frater LYNCH, 1884: 346

Material examined: Paraguay: Villarica, female, 1939, determined as O. frater (AMNH) .

Diagnosis: Compared to the other species of similar size, O. frater can be identified by the nearly parallel sides of the pronotum. The type specimen was not found in the Museo Argentino de Ciencias Naturales ‘Bernadino Rivadavia’, Buenos Aires. The specimen determined as O. frater in AMNH highly coincides with the description made by Lynch Arribálzaga (1884), in particular, concerning the parallel sides of the pronotum. Lynch described a size variance of 5 – 6 mm. The specimen in AMNH is slightly larger. Unfortunately only a female specimen could be studied.

Description: Length: 6.4 mm. Colouration: Brown; pronotum slightly lighter than head; elytra and posterior edge of abdominal segments reddish; legs red; antennae dark red.

Head: 0.8 mm wide, 1.2 mm wide; eyes not prominent; sides of fore-head distinctly convergent to front angles of clypeus; angles of clypeus produced to short granule; front edge of clypeus even; supra-ocular setiferous punctation granulate; punctures coriaceous; punctures on vertex large and dense with impunctate midline; setiferous punctures on clypeus partly granulate; area at base of antennae impunctate; on vertex, interstices between punctures half as wide as diameter of punctures; netlike microsculpture distinct; surface slightly shiny; central area close to neck and area at base of antennae without microsculpture; surface polished.

Antennae only slightly longer than head with second antennomere globular and third conical; third antennomere not longer than second; fourth antennomere slightly smaller than third; following antennomeres increasing in width; antennomeres 4 to 6 approximately quadrate; penultimate antennomeres slightly wider than long.

Pronotum: 1.2 mm long, 1.3 mm wide; widest at anterior angles; slightly and evenly narrowed to posterior smoothly rounded angles; sides with narrow margin; punctures large in irregular rows and with wide impunctate midline; row of punctures adjacent to midline coarse, nearly coriaceous; laterally punctation sparser; very sparse micro-punctation present; without microsculpture; surface polished.

Elytra: 1.25 mm long, 1.25 mm wide; with coriaceous ground-sculpture; setiferous punctation nearly invisible in coarse ground-sculpture; punctures deep and irregularly dense; surface less shiny than on pronotum.

Abdomen densely and deeply punctate; punctures setiferous; midline impunctate; weak netlike microsculpture present; surface slightly shiny.

Protibia: 0.72 mm long, 0.30 mm wide, 8 spines at outer edge; apical spines on short broad digits; WLR: 2.6; in posterior aspect, comb of inner emargination totally visible; posterior face densely covered by yellow setae.

Aedeagus unknown.

Figures

Fig. 73-78: Osoriellus-s. str.-group: Osoriellus frater (73), O. latipes (74); O. mexicanus (75), O. brevipennis (76), O. argentinus (77), O. crassus (78); antenna (A), protibia (B), aedeagus in lateral aspect (C); scale bar: 0.1 mm.

Fig. 97: Osoriellus-s. str.-group: Head, pronotum and elytra of Osoriellus bicolor (A), O. ashei (B), O. eggersi (C), O. parumpunctatus (D); O. humicola (E), O. minor (F); scale bar: 0.5 mm.