Trechus torgaut Belousov & Kabak, 2019

Belousov, Igor A. & Kabak, Ilya I., 2019, New species of the genus Trechus Clairville, 1806 from the Chinese Tien Shan (Coleoptera: Carabidae), Zootaxa 4679 (1), pp. 47-68 : 53-55

Trechus torgaut Belousov & Kabak , sp. n.

( Figs. 2 , 4 )

Type material: Holotype: 1(1) ♂, “ China, Xinjiang, sources of Kunges River, left bank near Adunkur 1 Pass , ESE of Kunges-Linchan, 2500–3100 m, 13.07.2001, Kabak I.I. leg.” [43º12´00´´ N / 84º47´40´´ E— 43º11´15´´ N / 84º47´20´´ E] ( ZISP) { Fig. 9 : 22–23 }. Paratypes: 63(5) ♂♂, 50♀♀, collected with holotype ( IZAS, MPU, BMNH, SMNS, ZISP, ZSM, CAG, CAK, CBK, CDW, CJS, CVZ); 30(4) ♂♂, 45♀♀, “ China, Xinjiang, left bank of Tsagan-Usun River (right tributary of Kunges River ), 2800–3400 m, 15.07.2001, Kabak I.I. leg.” [43º15´30´´ N / 84º47´30´´ E— 43º15´00´´ N / 84º48´05´´ E] ( IZAS, MPU, BMNH, SMNS, ZISP, ZSM, CAG, CAK, CBK) { Fig. 9 : 20–21}; 1(1) ♂, 1(1) ♀, “ China, Xinjiang, Narat Mt. Range Dzhergalan River , H= 3060 m, 18.07.2012, Kabak I.I. leg.” [43º13´03´´ N / 83º26´29´´] ( CBK) { Fig. 9 : 16 }.

Additional material examined: 1(1) ♀ (?), “ China, Xinjiang, Narat Mt. Range Tshon-Dzhergalan Basin, H= 3290 m, 18.07.2012, Kabak I.I. leg.” [43º12´28´´ N / 83º26´39´´] ( CBK) { Fig. 9 : 17 }.

Description. Medium-sized species for the uygur species group, body length 4.65–5.25 mm. Body elongate, constricted at pronotal base, markedly depressed ( Fig. 2 ). Antennae and legs long, especially tarsi. Upper-side reddish dark brown, usually with slightly darker head and disc of elytra. Anterior part of head, disc of pronotum, base, suture and margins of elytra paler, reddish. Legs uniformly brown reddish. Antennae vaguely obscured in apical half.

Head large, eyes small and subconvex, tempora long and convex, their pubescence sparse and extremely short, often barely distinguishable. Frontal furrows evenly impressed, slightly arcuate, nearly subparallel-sided and rather distant from each other in middle. Supraorbital setae located in lines distinctly convergent posteriad, posterior seta far behind posterior margin of eye. Pores of both anterior and posterior setae foveolate, though posterior one shallower.

Pronotum subcordate, convex on disc, markedly contracted at base, with maximum width in apical third. Its sides broadly arcuate in anterior part, nearly straight in posterior part, deeply sinuate before hind angles, the latter large and acute, produced mostly outwards. Posterior margin slightly bisinuate or straight; anterior margin nearly rectilinear, only slightly longer than posterior margin. Anterior angles broadly rounded and more or less produced anteriad. Lateral margins bordered and widely reflexed, especially so in posterior half. Prebasal transverse impression subparallel to posterior margin, rectangularly curved in basal foveae, rather deep, though not sharply engraved. Basal foveae average in size and depth. Apical transverse impression distinct throughout. Apical portion finely, basal portion roughly rugose. Anterior marginal seta placed in about anterior third of pronotum, posterior seta close to hind angle. Median line evenly impressed, more deeply near basal margin.

Elytra narrow, oblong-oval, widest in apical third, with nearly rectilinear sides, much narrower at level of humeri than at level of subapical sinuation. Humeri broadly rounded, prehumeral margin arcuate. Each elytron sinuate before and rounded at apex. Striation of elytra well-impressed: all striae distinct and continuous, though outer ones much shallower and occasionally shortened anteriad. Inner intervals slightly convex, others flat. Apical recurrent striole short and nearly straight, sinuate and joining stria 5 anteriorly. Stria 3 joining stria 4 on apical slope, stria 2 surpassing level of preapical pore, stria 6 joining stria 7 distinctly before anterior termination of recurrent striole. Parascutellar striole distinct. Apical triangle (three pores on apical slope of elytra) slightly oblong, angulo-apical pore located approximately in middle between exterior pore and apex of elytra. All striae finely but distinctly punctured.

Microsculpture shallowly engraved, faint medially on disc of both head and pronotum, consisting of isodiametric meshes on parietal area, irregular and slightly transverse meshes on disc of pronotum, and distinctly transverse meshes on elytra. Body finely micropunctured over entire surface, especially densely near anterior margin of pronotum.

Two basal segments dilated and clearly transverse in male anterior tarsi, both provided with adhesive appendages beneath. Front tibiae flattened on exterior surface, glabrous on anterior surface, except for one row of setae.

Aedeagus ( Fig. 4 ) of medium size, subcylindrical, slightly S-shaped, with oblique apical disc; sagittal aileron medium to small, nearly effaced in some specimens. Lamella rather short, medium-sized, well-defined, of triangular shape, rounded apically, directed to right side in dorsal view. Parameres slender, nearly straight in apical half; left one clearly longer, with distinctly protruding ventral apophysis; each paramere bearing 5–6 apical setae. Endophallus armature rather small, consisting of two pieces located in apical half of median lobe; larger piece semicylindrical in shape, located near ventral surface of aedeagal tube; second piece located near dorsolateral wall.

Sexual dimorphism. Males differ in smaller head (EW/HW on average, 1.76 vs. 1.70 in females, p≤0.001; PW/HW 1.16 vs. 1.14 respectively, p≤0.01), longer elytra (EL/PL, on average, 3.01 vs. 2.95 in females, p≤0.05), and longer antennae (AL/EL 1.01 vs. 0.99 in females, p≤0.01).

Variation. Externally, the population from the Tsagan-Usun River is larger (mean body length 5.0 mm vs. 4.9 mm in specimens from the type locality, p≤0.05), with pronotum wider (PW/PL, on average, 1.41 vs. 1.38 respec- tively, p≤0.01), anterior lateral seta of pronotum is located more posteriad (28% vs. 25% respectively, p≤0.001), all discal pores of elytra are located closer to the elytral base (discal formula: 26, 60, 89 vs. 27, 64, 91 in specimens from the type locality), umbilicate pores 1 and 2 are located more posteriorly (10% and 16% vs. 9% and 15% respectively).

Comparative notes. T. torgaut sp. n. differs from all known members of the uygur species group, in having a medium-sized aedeagus (very large in other species) with a rather short apical portion clearly curved upward.

T. torgaut sp. n. seems to be more similar to T. tsanmensis sp. n. described above, but differs, apart from the above-listed unique characters, in proportionally larger apical lamella and quite different endophallus armature with dorsal piece much smaller, located less proximally and consisting of two poorly sclerotized symmetrical lobes ( Fig. 4 vs. Fig. 3 ). Externally T. torgaut sp. n. can be distinguished from T. tsanmensis sp. n. by its smaller size (on average, 4.93 mm vs. 5.31 mm in T. tsanmensis sp. n.), much narrower habitus with proportionally wider head and pronotum (mean for EW/HW ratio is 1.73 vs. 1.81 in T. tsanmensis sp. n.; PW/PL: 1.40 vs. 1.35 in T. tsanmensis ; EW/PW: 1.50 vs. 1.57 in T. tsanmensis ) and the second discal pores of elytra located mostly at level of umbilicate pores 5 vs. clearly before this level in T. tsanmensis sp. n. T. torgaut sp. n. is also similar to T. uygur , though readily distinguished, first of all, by its shorter apical lamella, which is triangular-shaped in dorsal view vs. very long and parallel-sided, pointed apically in T. uygur and smaller endophallus armature ( Fig. 4 vs. Figs 5–6 ). Externally, the new species is distinguished from allied taxa by the shape of the pronotum with anterior angles, on average, more distinctly produced anteriad. Morphometrically, the new species differs from T. uygur in the longer anterior margin of the pronotum (PA/PB ratio is 1.04 vs. 1.01 in T. uygur , p≤0.001). In addition, T. torgaut sp. n. has wider elytra (means for EL/EW: 1.42 in T. torgaut vs. 1.50 in T. uygur , p≤0.001), more transverse pronotum (average values for PW/PL: 1.40 vs. 1.34, p≤0.001), longer antennae (means for EL/AL: 1.00 vs. 1.11 in T. uygur , p≤0.001) and somewhat smaller eyes; all discal setae are slightly shifted posteriad (discal formula: 26, 62, 90 vs. 24, 57, 88 in T. uygur ).

Distribution. The species inhabits mountains at sources of the Kunges River, Xinjiang, China. Additionally, a small series of this species was collected on the northern slopes of the Narat Mountain Range, in the basin of the Tshon-Dzhergalan River, approximately 15.5 km west of the type locality of T. tsanmensis sp. n. and more than 100 km west of other known findings of T. torgaut sp. n.

Bionomics. The species occurs in a comparatively wide belt of altitudes between 2500 and 3400 m. It was found in the forest zone as well as in the alpine zone and seems to be associated with humid biotopes, especially strictly at lower elevations.

Derivatio nominis. The species is named after a tribe of Mongolian people.

Figures

FIGURE 9. Collecting sites of Trechus species of the uygur group. Yellow rhomb—T. sinus Belousov & Kabak, 2001; red rhomb—T. arshanicus Belousov & Kabak, 2001; yellow square—T. uygur ssp. kuytunicus Belousov & Kabak, 2001; red square—T. uygur ssp. uygur Deuve, 1993; yellow triangle—T. torgaut sp. n.; red triangle—T. tsanmensis sp. n. Locality numbers—as in the “Material” section; those for collecting sites of T. arshanicus and T. sinus—see Belousov & Kabak (2001).

FIGURES 1–2. Trechus Clairville, 1806, habitus, males, paratypes. 1, T. tsanmensis sp. n.; 2, T. torgaut sp. n.

FIGURES 3–4. Male genitalia of Trechus spp. n., paratypes: a—lateral view, b—dorsal view, c—paramere. 3—T. tsanmensis sp. n.; 4—T. torgaut sp. n.

FIGURES 5–6. Male genitalia of Trechus uygur (from Belousov & Kabak 2001): a—lateral view, b—dorsal view. 5—T. uygur ssp. uygur Deuve, 1993 from the Ulan-Gelik Pass; 6—T. uygur ssp. kuytunicus Belousov & Kabak, 2001, paratype.