Trechus comma, Belousov & Kabak, 2021

Belousov, I. A. & Kabak, I. I., 2021, Three new species of the genus Trechus Clairville, 1806 from Sichuan (Coleoptera: Carabidae: Trechini), Russian Entomological Journal 30 (4), pp. 401-421 : 405-407

Trechus comma sp. n.

Figs 5–8 .

MATERIAL. Holotype ♂, “ China, NW Sichuan, NE of Lixian, N Tonghua, basin of river near Pingshitou , S of Shibanpengzi, H~ 3900 m, 22.08.2002, Belousov I. & Kabak I. leg.” [31°44´41´´N / 103°22´50´´E]. Paratypes: 12(8) ♂♂, 8(1) ♀♀, collected with holotype ( IZAS, NME, MPU, SMNS, ZSM, CAG, CBK, CJS);13(4) ♂♂, 6(1) ♀♀, “China, NW Sichuan, NE of Lixian, N Tonghua, basin of river near Pingshitou, S of Shibanpengzi, H~ 3600–3900 m, 20.08.2002, Belousov I. & Kabak I. leg.” [31°44´30´´N / 103°22´50´´E — 31° 44´41´´N / 103°22´50´´E] ( BMNH, CAK, CVZ, CBK) .

DESCRIPTION. Body ovate, markedly constricted at pronotal base, convex ( Fig. 8). Appendages not long, legs stout, especially femora in males. Upper side reddish brown, often with darker blackish disc of elytra; the suture, margins of elytra and occasionally head and disc of pronotum paler, reddish. Legs and antennae uniformly yellowish. Head before clypeal suture reddish brown.

Microsculpture well developed on head and pronotum, though becoming shallower on disc of the latter, consisting of isodiametric meshes on median portion of head, more or less uniform transverse meshes on pronotum, and transverse shallow anastomosing lines on elytra, surface of elytra with iridescent luster. All upper side distinctly micropunctured.

Head of medium size, eyes rather small and flat, tempora long and convex, scarcely pubescent. Frontal furrows regularly impressed, subangulate, approaching one another in middle; frons convex. Supraorbital setae located in lines, slightly convergent anteriad, posterior seta far behind posterior margin of eye. Pore of anterior supraorbital seta markedly foveolate that of posterior seta slightly so. Mandibles stout, evenly curved. Tooth on right mandible tridentate, its shape rather variable, distal and proximal denticles always most prominent, with deepest notch between median and distal denticles. Labrum with anterior margin deeply concave.

Pronotum transverse, subconvex, with maximum width clearly before middle, markedly contracted at base. Its sides evenly and broadly arcuate, barely sinuate before hind angles, latter rather small but distinct, subrectangular. Posterior margin straight medially, obliquely truncate laterally; anteri- or margin straight. Anterior angles marked but not salient. Lateral margins narrowly bordered and slightly reflexed, lateral groove of average width, slightly expanded posteriorly. Prebasal transverse impression shallow, vaguely delimit- ed, angularly curved in basal foveae, the latter rather small and shallow. Apical transverse impression irregular, occasionally interrupted medially.Discal foveae missing or slightly impressed. Anterior marginal seta placed in about anterior third of pronotum, posterior seta in hind angle. Base of pronotum distinctly rugose. Median line distinct, slightly impressed, deepest at level of prebasal transverse impression.

Elytra oval, with evenly arcuate sides, widest just after their mid-length. Humeri broadly rounded, prehumeral margin evenly arcuate, posthumeral sinuation indistinct. Elytral apex broadly rounded, nearly truncate, with a distinct preapical sinuation. Elytral striae rather deep and regular, even stria 7 partially visible. Intervals 3–4 subconvex, others flat, interval 2 distinctly wider than interval 1 in apical portion of elytra. All elytral striae finely punctured and slightly undulate. Stria 2 surpassing level of preapical pore, with or without distinct connection with stria 3, latter joining stria 4 at level clearly behind anterior termination of apical striole. Striae 5 and 6 joining each other slightly behind median group of umbilicate series or near that level; stria 7 without clear connection with any of other striae. Both parascutellar striole and parascutellar seta present. Apical recurrent striole of average length, deep and straight anteriorly, usually surpassing level of mid-distance between umbilicate pores 7 and 8 anteriad, joining fused stria (5x6) anteriorly. Striation on apical slope as follows: ((5x6)xAS)(3x4)(2x3). Apical triangle usually subequilateral, inner sides of apical triangles of both elytra subparallel to body axis. Preapical pore placed at level of umbilicate pore 8 or slightly behind. Angulo-apical pore usually set closer to exterior pore than to elytral suture. Lateral margins bordered and narrowly reflexed in posterior part while moderately reflexed in anterior part.

Protibiae depressed and slightly grooved on exterior surface in their median part; two basal segments of male protarsi dilated, markedly transverse.

Median lobe of aedeagus ( Figs 5, 7 ) of medium size, rather thick, angularly curved at basal third, with ventral side nearly straight for most of its length, apical portion distinctly attenuates downwards and gradually narrowing toward small and button-like apex in lateral view. Apical lamella subparallel sided, with apical margin broadly rounded in dorsal view. Sagittal aileron small. Parameres of average size, their apex variable: rounded, oblique or truncate ( Figs 5–6 ). Endophallus armature S-shaped in dorsal view and somewhat triangular shaped in lateral view; one poorly defined scaly area located near left dorsal wall of the median lobe.

SEXUAL DIMORPHISM. Males differ in larger body size (on average, 3.11 mm vs. 3.02 mm in females, p≤0.01), proportionally longer elytra (EL/EW, on average, 1.34 vs. 1.31 in females, p≤0.001; EL/PL, on average, 2.77 vs. 2.73 in females, p≤0.05; EL/TiL, on average, 2.39 vs. 2.36 in females, p≤0.05) and narrower pronotum (PW/PL, on average, 1.38 vs. 1.40 in females, p≤0.05).

COMPARATIVE NOTES. T. comma sp.n. is most closely related to neighboring T. xiongmao sp.n. but differs in having larger size, flatter and longer eyes, less transverse pronotum with sides more deeply sinuate before larger hind angles, which are more produced, basal margin narrower, basal surface more coarsely rugose; elytra more elongate; apical recurrent striole longer, surpassing level of mid-distance between umbilicate pores 7 and 8; lateral margins of both pronotum and elytra less markedly reflexed (the differences in morphometric characters are shown in Table 2). The male genitalia of the new species differ from those of allied taxa in their rather thick shape ( Fig. 5 ) and transverse triangular contour of the main copulatory piece in the endophallus armature (in lateral view). Nonetheless, the principal structure of the endophallus armature is similar to that of related species like T. xiongmao sp.n. ( Fig. 5 vs. Fig. 2 ), T. gansuensis Deuve et Quéinnec, 1993 , and T. xiei Deuve, 1992 .

DISTRIBUTION. The species is known only from the upper valley of the Sanchagou River located north of the township of Tonghua, Wenchuan County, Sichuan.

BIONOMICS. The species occurs in the upper forest and subalpine zones, at elevations of 3600–3900 m. It was found mostly in the forest litter and along banks of mountain streams in the subalpine zone.

DERIVATIO NOMINIS. The species epithet derives from the particular shape of the copulatory piece resembling the comma.

Figures

Figs 2–7. Male genitalia of Trechus spp. n.: 2–4 — T. xiongmao sp. n., paratype; 5–7 — T. comma sp. n., paratype; 2, 5 — lateral view; 3, 7 — dorsal view; 4 — distal portion, right lateral view; 6 — right paramere, apex. Рис. 2–7. Гениталии самцов новых видов рода Trechus: 2–4 — T. xiongmao sp. n., паратип; 5–7 — T. comma sp. n., паратип; 2, 5 — сбоку; 3, 7 — сверху; 4 — дистальнаЯ часть, справа; 6 — верШина правой парамеры.