Trechisibus striatus, 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 : 61-63

Trechisibus striatus n. sp.

( Figs. 8 a, 8b, 8c, 8d, 17)

Type locality. Argentina, Neuquen, Pen. Quetrihué.

Diagnosis. A Trechisibus species 3.46–3.74 mm long, dark brown and shiny; legs, antennae, mouth parts and lateral border of elytra reddish brown. Hind angles of pronotum usually acute and protruding outwards. Elytra oval, slightly convex on disc, with 2 discal setigerous punctures (in addition to the preapical pore) on the 3rd stria, the first at about 1/4 from base and the second just behind middle. T. striatus n. sp. is distinguished from all other Trechisibus species distributed in Patagonian Argentina by the deeply impressed 1st–3rd elytral striae ( Fig. 8 a) and by the peculiar morphology of the median lobe of aedeagus as well as of the copulatory piece ( Fig. 8 b).

Type Series. HT ♂, Argentina, Neuquen, Pen. Quetrihué, 12.II.1998, legit Riccardo Sciaky (CSc). PTT: 4 ♀♀, same data as the holotype (CAl, CGi, CSc).

Description. Habitus as in Fig. 8 a. Overall length of the HT ♂ (from labrum to apex of elytra) 3.74 mm. Body dark brown, obovate, shiny. Microsculpture very superficially impressed on pronotum and elytra in both sexes, markedly impressed on head. Antennae, mouth parts, legs and lateral border of elytra reddish brown. Brachypterous.

Head moderately large, eyes large and convex; temples slightly convex and delicately pubescent, hardly shorter than eyes. A microsculpture in isodiametric meshes markedly impressed on whole upper surface of head. Clypeus with two apical setae on each side; labrum transverse, 6-setose, distinctly excavate at apex. Frons between eyes convex with a small depression on vertex. Antennae moderately long, reaching the basal 4th of elytra.

Pronotum convex on disc, transverse (width/length = 1.46), with base slightly wider than anterior margin ( Fig. 17 ). Disc almost shiny and microsculpture nearly absent except at sides and near fore margin. Sides rounded on whole length; basal margin almost rectilinear, slightly sinuate at sides. Front angles hardly prominent; hind angles usually acute and protruding outwards (seldom nearly right angles). Mid longitudinal line distinctly impressed, deepened and enlarged near base. A wide basal impression on each side, separated at middle by a wrinkled convexity of the base and by the enlarged mid longitudinal line. Lateral border narrow and only slightly broadened towards base; anterior and posterior margins bordered only at sides. Two lateral setae on each side, one at hind angles (moved a little forwards from the angle) and one at about 2/3 from base.

Elytra oval (length/width=1.33), fairly convex and not depressed on disc. Microsculpture in transverse meshes, very superficial in both sexes and hardly visible only near base and at sides. Shoulders with humeral angle distinct. The basal margin interrupted in correspondence with the 5th stria. 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 narrow over the whole length, reddish brown and distinctly contrasting in colour with the darker elytra. Two discal setigerous punctures in small foveae on the 3rd stria, the 1st at basal 4th of elytra and the 2nd just behind middle; the punctures usually divert the 3rd stria linearity; preapical pore at about middle of the recurrent striole. Umbilicate series of 4+2+2 punctures, with a wide distance between the 1st and the 2nd group. 1st–3rd striae (and sometimes 4th) deeply impressed but vanishing at base and at apex, the 5th–7th very superficial and hardly visible, the 8th deeply impressed in the posterior half. Inner intervals feebly convex, the others flat. Elytral apex broad and rounded. The recurrent striola moderately long and arcuate.

Legs slender. Protibiae straight and externally distinctly furrowed. Tarsi pubescent on the upper side. The 1st and 2nd male protarsomeres asymmetrically dilated.

Median lobe of aedeagus moderately slender, in lateral view the inferior edge delicately sinuate towards apex ( Fig. 8 b), which is short and, in dorsal view, widely blunt ( Fig. 8 c). The internal armature consists of a cylindrical copulatory piece anteriorly provided with a longitudinal bundle of sclerotized teeth ( Fig. 8 c). Parameres wide and short, almost equally long, each provided with 4 apical setae ( Fig. 8 b).

Etymology. The specific epithet refers to the deeply impressed inner elytral striae.

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

Relationships. At the present state of knowledge, the phylogenetic affinities of Trechisibus striatus n. sp. are unclear. Despite the strong differences in the morphology of aedeagus, this species shows many similarities in the external morphology with Trechisibus sciakyi n. sp., Trechisibus brevis n. sp. and Trechisibus longipenis n. sp.

Figures

FIGURE 8. Trechisibus striatus 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).