Osoriellus adustus, 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 : 296-297

Osoriellus adustus n. sp.

( Figs 108 A-C, 123E)

Type material: Holotype, male: Peru: Loreto Prov., Iquitos (73°14'W, 3°44'S), 90 m elevation, collected in leaf litter in the forest, 8.5.1992, leg. J. Danoff-Berg ( KNHM).

Paratype: Peru: 1 female with same data as holotype (UIC) .

Diagnosis: The species is characterised by the deep and dense microsculpture of the pronotum and the digitate protibibia with a WLR of 1.00. Species with a similarly deep pronotal microsculpture are larger such as O. opacus and O. opacinotus or have additionally no digitate protibia.

Description: Length: 4.5 long. Colouration: Dark brown, nearly black; legs and antennae reddish brown.

Head: 0.55 mm long, 0.94 mm wide; eyes prominent; nearly twice as long as temples; sides of fore-head convergent to anterior angles of clypeus in smooth concave curve; anterior edge of clypeus even; punctation with moderately deep and irregularly dense punctation; punctures without setae except one pair of setae on clypeus, one pair on vertex close to neck, and several setae on supraocular area; large area at base of antennae impunctate; punctation on vertex much denser than on clypeus; on vertex, interstices between punctures aproximately as wide as diameter of punctures; on supraocular area, punctation partly coriaceous and with striae; isodiametric microsculpture dense and deep; surface matt.

Antennae slightly shorter than head and half of pronotum combined; second antennomere elongate; approximately 1.5 times as wide as conical third antennomere; fourth and fifth antennomere as wide as third; sixth antennomere quadrate and slightly wider than preceding antennomeres; following antennomeres distinctly wider than preceding antennomeres; quadrate.

Pronotum: 0.94 mm long, 1.05 mm wide; widest at anterior angles; anterior angles slightly produced; sides convergent to posterior angles in smooth even curve; posterior angles distinct, but obtuse; lateral margin fine in anterior half, slightly thicker in posterior half; shortly in front of posterior angles, slightly widened; in dorsal aspect, covered close to anterior angles; punctation sparser and deeper than on head; with short setae; on average, interstices between punctures at least twice as wide as diameter of punctures; punctures denser within irregular row adjacent to moderately wide impunctate midline; isodiametric microsculpture deep and dense; surface matt.

Elytra: 1.13 mm long, 1.08 mm wide; shoulders rounded; sides sligthly widened posteriad; widest in posterior third; punctation similarly dense and deep as on pronotum; in irregular rows; coriaceous ground-sculpture weak; isodiametric microsculpture dense, but weaker than on pronotum; surface slightly shinier than on pronotum.

Abdomen with sparse and fine punctation; punctures without setae except few setae in transverse row; netlike microsculpture weaker than on fore-body; surface shiny. Protibia: 0.57 mm long, 0.15 mm wide; slender; outer edge with seven spines; apical spines inserting on moderately long digits; WLR: 1.0; in posterior aspect, inner emargination with comb visible throughout its total length; posterior face sparsely covered by long yellow setae.

Aedeagus thick; apical lobe smoothly curved; apex widely rounded; inner edge of apical lobe with nine sensillae.

Etymology: The specific name adustus derived from the same Latin word meaning brownish and refers to the dark brown colouration.

Figures

Fig. 103-108: Remaining-species-group: Osoriellustrinitatis (103), O. carinicollis (104), O. sticticus (105), O. acutus (106), O. orbiculatus (107), O. adustus (108); antenna (A), protibia (B), aedeagus in lateral aspect (C); scale bar: 0.1 mm.