Trechisibus parvulus, Allegro, Gianni & Giachino, Pier Mauro, 2016

Allegro, Gianni & Giachino, Pier Mauro, 2016, Nine new Trechisibus species from Peru and Argentina (Coleoptera: Carabidae: Trechinae), Zootaxa 4193 (1), pp. 49-72 : 68-70

Trechisibus parvulus n. sp.

( Figs. 12 a, 12b, 12c, 12d, 21)

Type locality. Argentina, Neuquen, Pen. Quetrihué.

Diagnosis. A Trechisibus species 2.53–2.78 mm long, brown or reddish brown, shiny, with pronotum paler than elytra; legs, antennae, mouth parts and lateral border of elytra yellowish. Hind angles of pronotum obtuse. Elytra oval, widest at middle, moderately depressed on disc, with 2 discal setigerous punctures (in addition to the preapical pore) on the 3rd stria, the first at about 1/3 from base and the second just behind middle. T. parvulus n. sp. is distinguished from all other Trechisibus species distributed in the Patagonian Andes by its small size and by the peculiar morphology of the median lobe of aedeagus.

Type Series. HT ♂, Argentina, Neuquen, Pen. Quetrihué, 12.II.1998, legit Riccardo Sciaky (CSc). PTT: 6 ♂♂, same data as the holotype (CAl, CGi, CSc).

Description. Habitus as in Fig. 12 a. Overall length of the HT ♂ (from labrum to apex of elytra) 2.67 mm (PTT ♂♂ 2.53–2.78). Body brown or reddish brown with pronotum paler than elytra, obovate, shiny. Microsculpture distinctly impressed only on fore half of head, nearly absent on pronotum and elytra. Legs, antennae, mouth parts and lateral border of elytra yellowish. Brachypterous.

Head moderately large, eyes small and convex; temples convex and delicately pubescent, hardly longer than eyes. A microsculpture in isodiametric meshes impressed on fore half of head, on vertex and neck less distinct. Clypeus with two apical setae on each side; labrum transverse, 6-setose, distinctly excavate at apex. Frons between eyes convex depressed on vertex. Antennae relatively short, hardly reaching the basal 5th of elytra.

Pronotum convex on disc, transverse (width/length = 1.34), with base much narrower than anterior margin ( Fig. 21 ). Microsculpture very superficial, nearly absent on disc and hardly visible near base and fore margin. Sides rounded for most of length, shortly sinuate before hind angles; basal margin almost rectilinear. Front angles feebly prominent; hind angles obtuse. Mid longitudinal line distinctly impressed between the submarginal sulci, deepened towards base. A wide basal impression on each side, separated at middle by the superficially wrinkled convexity of the base. Lateral border moderately wide on whole length; anterior and posterior margins unbordered. Two lateral setae on each side, one at hind angles (moved distinctly forwards from the angle) and one at about 2/3 from base.

Elytra oval (length/width=1.35), widest at middle, feebly depressed on disc. Microsculpture absent on disc and hardly visible at base and apex. Shoulders rounded with humeral angle indistinct. The basal margin interrupted in correspondence with the 5th interval. A short scutellar stria is present, as well as a juxtascutellar pore near base, in correspondence with the 2nd stria. Sides moderately rounded; lateral border moderately wide on whole length, reddish brown and distinctly contrasting in colour with the darker elytra. Two discal setigerous punctures in small and superficial foveae on the 3rd stria, the 1st at basal 3rd of elytra and the 2nd just behind middle; the punctures divert the 3rd stria linearity; preapical pore at about middle of the recurrent striole. Umbilicate series of 4+2+2 punctures, with groups widely spaced from each other. The four inner striae distinctly impressed only on disc, obliterated towards base and apex as well as all the other striae; the 8th stria deeply impressed in the posterior half. Intervals nearly flat. Elytral apex broad and rounded. The recurrent striola moderately long and arcuate.

Legs relatively short. Protibiae nearly straight and externally superficially furrowed. Tarsi pubescent on the upper side. The 1st and 2nd male protarsomeres asymmetrically dilated.

Median lobe of aedeagus tiny, ventrally rectilinear in lateral view and tapered towards apex ( Fig. 12 b); apical blade short and, in dorsal view, rounded at apex ( Fig. 12 c). A simple copulatory piece, short and triangular in dorsal view ( Figs. 12 c). Parameres short, the right one shorter than the left, each provided with 4 apical setae ( Fig. 12 b).

Etymology. The specific epithet refers to the small size of this species.

Distribution and habitat. At present Trechisibus parvulus n. sp. is only recorded from the type locality. The specimens of the type series were collected at about 800 m a.s.l.

Relationships. At the present state of knowledge, the phylogenetic affinities of Trechisibus parvulus n. sp. are unclear, but due to the marked differences in the morphology of the habitus and aedeagus, this species probably belongs to a different lineage with respect to the other species collected at the same locality and here described, namely Trechisibus striatus n. sp., Trechisibus sciakyi n. sp., Trechisibus brevis n. sp. and Trechisibus longipenis n. sp.

The Trechisibus species so far recorded from Argentina, with their respective regional distribution, are:

Figures

FIGURE 12. Trechisibus parvulus n. sp. HT: habitus (a); median lobe of aedeagus in lateral view (b); median lobe of aedeagus in dorsal view (c).

FIGURES 17 – 21. Pronotum of Trechisibus: striatus n. sp. HT (17); sciakyi n. sp. HT (18); brevis n. sp. HT (19); longipenis n. sp. HT (20); parvulus n. sp. HT (21).