Trechus mengensis, Belousov & Kabak, 2020

Belousov, Igor A. & Kabak, Ilya I., 2020, New Trechus species of the kozlovi group from Sichuan (Coleoptera: Carabidae), Zootaxa 4786 (4), pp. 451-484 : 467-468

Trechus mengensis sp. n.

( Fig. 16, 19 )

urn:lsid:zoobank.org:act:FEE772E5-C32C-4DD0-A4F7-908A2830C5B4

Type material: Holotype: 1(1) ♂, “ China, NW Sichuan, NW of Lixian , 12 km WSW of Shangmeng, alp., scree 4000–4200 m, 26.07.2002, Belousov I. & Kabak I. leg.” [31º39´00´´N / 103º01´10´´ E] ( ZISP) . Paratypes: 14(9) ♂♂, 4♀♀, collected with holotype ( IZAS, MPU, ZSM, CAG, CAK, CBK); 3(3) ♂♂,“ China, NW Sichuan, NW of Lix- ian, 10 km WSW of Shangmeng , alp., scree, 3850–4000m, 25.07.2002, Belousov I. & Kabak I. leg.” [31º39´40´´N / 103º01´50´´ E] ( CBK) .

Description. Body broad, oval, markedly constricted at pronotal base, subconvex ( Fig. 16). Appendages moderately long and rather thick. Upperside blackish brown, usually anterior portion of head, disc of pronotum, suture and margins of elytra reddish. Legs pale reddish brown. Antennae vaguely obscured beginning from apical parts of segments 3–5.

Head of average size for the group, eyes medium-sized and convex, tempora rather long and plane or slightly convex, with a few very short hairs. Frontal furrows subangulate or arcuate, approaching each other in middle, becoming slightly deeper just behind their mid-length, shallow in posterior portion. Supraorbital setae located in lines slightly convergent anteriad, posterior seta far behind posterior margin of eye. Pores of both anterior and posterior setae foveolate, though posterior one less markedly.

Pronotum transverse, slightly convex, cordate, rather markedly constricted at base, with maximum width in apical third. Its sides broadly arcuate in anterior part; on average, moderately sinuate before hind angles, the latter variable, ranging from acute to obtuse. Posterior margin straight, slightly oblique or emarginate at sides; anterior margin straight. Anterior angles marked, but rounded. Lateral margins moderately reflexed, lateral groove rather wide, slightly expanded posteriorly. Prebasal transverse impression parallel to and far distant from basal margin, markedly curved near basal foveae, not sharply engraved. Basal foveae large and deep. Apical transverse impression distinct laterally, shallow or even effaced medially. Anterior marginal seta located in about anterior third of pronotum, posterior one at hind angle. Base of pronotum shallowly rugose, more coarsely near middle. Median line well impressed, deepest near its base, not reaching anterior margin.

Elytra broad, oblong-oval, with sides evenly and broadly arcuate, widest clearly behind their mid-length, subconvex on disc. Humeri prominent and broadly rounded. Elytra conjointly rounded, each elytron with a distinct subapical sinuation. Striation of elytra rather regular and complete: striae 1–4 well impressed and continuous, others shallow and shortened anteriad and posteriad, becoming shallower toward sides. Inner intervals subconvex, outer rather flat. All elytral striae slightly punctured. Stria 2 surpassing or not the level of preapical pore, normally without distinct connection with stria 3; the latter joining stria 4 approximately at level of anterior end of apical striole; striae 5 and 6 joining each other far before elytral apex, near level of median group of umbilicate series; stria 7 usually joining apical striole and forming here a distinct sinuation. Parascutellar striole long and well engraved. Parascutellar pore present. Apical recurrent striole deep, straight or slightly curved, rather long, though not reaching level of umbilicate pore 7, markedly divergent from suture anteriad, externally bordered by a well-developed carina. Apical triangle very long, angulo-apical pore more distant from elytral suture than from exterior pore. Lateral margins slightly reflexed, lateral groove of medium width.

Microsculpture well developed over entire body surface, consisting of isodiametric meshes on head, very fine, irregular and slightly transverse meshes on disc of pronotum, becoming much coarser toward pronotal base, and markedly transverse meshes on elytra, the latter with distinct iridescent luster.

Fore tibiae flattened or shallowly grooved on their exterior surface in middle part, with a few short hairs on anterior surface near inner apex of tibia. In male, two proximal segments of protarsi markedly dilated and dentate, both clearly transverse.

Median lobe of aedeagus very large, subcylindrical, angularly bent at basal portion in lateral view ( Fig. 19a ). Both ventral and dorsal margins less emarginate before apex than in T. shangensis sp. n., apical disc well developed. In dorsal view ( Fig. 19b ), median lobe rather slender, broadest in basal portion or, at least, without distinct dilatation in apical third. Preputial field variable, vaguely delimited, almost reaching basal bulb. Ventral surface with a distinct carina, visible from below. Apical lamella well defined, rather long and narrow, broadly rounded at apex, with sides slightly convergent distally. Sagittal lobe large, viewed dorsally distinctly thickened and grooved along its crest. Parameres long and slender, straight in distal half, left paramere clearly longer, with a well-developed ventral apophysis; each paramere bearing 4 apical setae. Endophallus armature consisting of two slightly sclerotized pieces: proximal one semi-ring shaped, located near mid-length of median lobe close to its left and dorsal walls, its dorsal portion simple, without emargination; distal piece smaller, located mainly in horizontal plane, covered with barely distinguishable scaly patch from left side.

Sexual dimorphism. Males differ in longer and flatter elytra (EL/PL, on average, 2.89 vs. 2.79 in females, EL/TiL, on average, 2.18 vs. 2.11 respectively, for both ratios p≤0.05) and smaller head (EW/HW, on average, 2.07 vs. 2.00 in females, p≤0.05).

Comparative notes. Doubtless T. mengensis sp. n. is most closely related to T. shangensis sp. n. described above. Surprisingly, these two so similar species were found syntopically. This fact is of primary importance since it shows that even morphologically very similar species can coexist in the same area without interbreeding with one another. Similarly to many other cases when two related species inhabit the same territory, T. mengensis sp. n. and T. shangensis sp. n. clearly differ morphometrically (p≤0.001, t- criterion): T. mengensis sp. n. is larger (body length, on average, 3.63 mm vs. 3.27 mm in T. shangensis sp. n.), less markedly convex (ratio EL/BH, on average, 2.62 vs. 2.42 in T. shangensis sp. n.), elytra proportionally larger (EW/PW, on average, 1.65 vs. 1.53, EW/HW 2.06 vs. 1.94, EL/PL 2.87 vs. 2.72 in T. shangensis sp. n.), hind tibiae longer (TiL/TaL, on average, 1.43 vs. 1.35, EL/TiL 2.16 vs. 2.29 in T. shangensis sp. n.), the 3 rd antennomere longer (L3/W3, on average, 2.23 vs. 1.98, L3/L2 1.17 vs. 1.11, YL/L3 1.15 vs. 1.20 in T. shangensis sp. n.), pronotum narrower or head broader (PW/HW, on average, 1.24 vs. 1.27 in T. shangensis sp. n.), preapical elytral pore shifted anteriad, umbilicate pores 1–3 and 5 shifted posteriad (for significant differences based on the Mann—Whitney criterion, see Table 2). In addition to these morphometric characters, T. mengensis sp. n. differs from its counterpart in the pronotum with basal margin less markedly oblique laterally and lateral margins more widely reflexed, as well as in elytral striae less distinctly punctate. The aedeagus of the new species differs from that of T. shangensis sp. n. in its larger size, more slender shape, ventral carina more markedly developed, longer and narrower lamella, longer preputial orifice; details of the endophallus armature (proximal sclerite deprived of dorsal emargination) ( Fig. 19 vs. Fig. 18 ).

Distribution. Similarly to T. shangensis sp. n., T. mengensis sp. n. is only known from the upper valley of a small river located WSW of Shangmeng Village, NW of Lixian City, Lixian County, Sichuan.

Bionomics. The species occurs at elevations between 3850 and 4200 m mainly in the alpine zone. It seems to prefer more humid biotopes as compared to the sympatric T. shangensis sp. n.

Derivatio nominis. The species epithet refers to the second part of the toponym “Shangmengxiang”, a village located near mountains where this species was collected.

Figures

FIGURES 18–20. Male genitalia of Trechus spp. n., paratypes: a—lateral view, b—dorsal view. 18—T. shangensis sp. n.; 19—T. mengensis sp. n.; 20—T. cuspis sp. n.