Trechus tsanmensis 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 : 49-53

Trechus tsanmensis Belousov & Kabak , sp. n.

( Figs. 1 , 3 )

Type material: Holotype: 1(1) ♂, “ China, Xinjiang, Narat Mt. Range, sources of Zhasylkol River (left trib. of Za- nma River ) 3000–3200 m, 24.06.2001, Kabak I.I. leg.” [43º12´00´´ N / 83º39´00´´ E— 43º11´40´´ N / 83º39´00´´ E] ( ZISP) { Fig. 9 : 18–19 }. Paratypes: 45(5) ♂♂, 107(1) ♀♀, collected with holotype ( IZAS, MPU, BMNH, SMNS, ZISP, ZSM, CAG, CAK, CBK, CDW, CJS, CVZ) .

Description. Size very large, body length, on average, markedly exceeding 5 mm (see Table 1 ). Body shape ( Fig. 1 ) oblong-ovate, markedly constricted at pronotal base, subconvex, depressed on elytral disc. Antennae and legs long, especially tarsi. Upper-side reddish brown, with slightly darker head and disc of elytra. Anterior part of head, disc of pronotum, suture and margins of elytra often a little paler, reddish. Legs uniformly reddish, antennae either uniformly reddish or vaguely obscured in apical half.

Head of large size, 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 bisinuate or straight; anterior margin nearly straight, clearly longer than posterior margin. Anterior angles rounded and slightly produced. Lateral margins bordered and moderately reflexed, lateral groove slightly widened posteriorly. Prebasal transverse impression subparallel to posterior margin, rectangularly curved in basal foveae, rather deep, though not sharply engraved. Basal foveae of average size and depth. Apical transverse impression distinct throughout. Apical portion of pronotum finely, basal portion roughly longitudinally rugose. Anterior marginal seta placed in about anterior third of pronotum, posterior seta close to hind angle. Median line evenly impressed, more deeply near prebasal transverse impression.

Elytra oblong-oval, with broadly rounded sides, widest in apical third, much narrower at level of humeri than at level of subapical sinuation. Humeri and prehumeral margin evenly rounded. Each elytron markedly sinuate and separately rounded at apex. Striation of elytra rather shallow: only 3–4 inner striae distinct and continuous, others barely distinguishable, often shortened anteriorly or posteriorly, becoming less distinguishable toward sides. Intervals flat. Apical recurrent striole short and nearly straight or slightly sinuate anteriorly, directed to stria 5. Only striae 2 and 3 distinctly joining on apical slope, their common continuation normally disappearing slightly behind preapical pore. Parascutellar striole distinct but shallow. Apical triangle (consisting of the preapical pore and two apical pores) slightly oblong.

Microsculpture shallowly engraved, faint medially on disc of both head and pronotum, consisting of nearly 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 toward anterior margin of pronotum.

Two basal segments dilated and clearly transverse in male anterior tarsi, both with adhesive appendages beneath. Front tibiae flattened and bordered by weak ribs on exterior surface, with a row of few, sparse and rather long hairs on anterior surface.

Aedeagus ( Fig. 3 ) large, slightly depressed dorso-ventrally, step-like curved, with apical portion only marginally bent upward and oblique apical button. Lamella well-defined, rather short and narrow, of triangular shape, with convergent sides and rounded apex in dorsal view. Sagittal aileron medium-sized. Parameres long and slender, nearly straight in apical half, distinctly widened distally, left one clearly longer, with a rather short ventral apophy- sis; each paramere normally bearing 6 apical setae. Endophallus armature consisting of large and poorly sclerotized pieces and a vaguely differentiated scaly patch located in apical half of median lobe.

Sexual dimorphism. Males differ in larger elytra (EL/PL on average, 3.0 vs. 2.91 in females, significance level p≤0.001; ratio EL/EW 1.40 vs. 1.38 respectively, p≤0.05), smaller head (EW/HW on average, 1.83 vs. 1.79 in fe- males; PW/HW 1.17 vs. 1.15, p≤ 0.05 in both ratios), and smaller eyes (L3/YL on average, 1.27 vs. 1.19 in females, p≤0.01).

Comparative notes. T. tsanmensis sp. n. appears to be rather isolated within the uygur species group. It differs from all known species in having aedeagus with basal portion markedly curved and apical portion short and nearly straight, only faintly curved upwards ( Fig. 3 ). Endophallus armature is also rather specific: proximal copulatory piece homologous to that of other species is small and located near mid-length of the aedeagal tube while all distal part of the tube is filled with hyaline structure, which either completely missing or significantly reduced in other species. Among all known members of the group, it seems to be most similar to T. arshanicus Belousov & Kabak 2001 . These two species share very large size with body length significantly exceeding 5 mm and large aedeagus with basal portion markedly curved ( Belousov & Kabak 2001). However, T. arshanicus differs in the median lobe of aedeagus with apical portion markedly curved upward in lateral view, very broad apical lamella in dorsal view and only one well-delimited copulatory piece near its mid-length ( Fig. 7 ). On the other hand, T. tsanmensis sp. n. is rather similar to the two known geographic races of T. uygur Deuve, 1993 ( Deuve 1993, Belousov & Kabak 2001). Both species are similar in having generally the same appearance, large aedeagus with oblique apical disc and parameres widened apically. Externally, the new species differs from T. uygur mostly in shallower elytral striae becoming indistinct on the outer area of the apical slope. It can be more readily distinguished by the structure of the male genitalia: the median lobe is much more markedly curved at its base, with apical lamella rather small and of triangular shape in T. tsanmensis sp. n. while the median lobe is slightly and symmetrically S-curved at basal and apical portions in lateral view, with apical portion much longer and lamella parallel-sided for most of its length and pointed, not rounded apically in T. uygur ( Figs 5–6 ). Morphometrically, the new species is larger (average body length 5.3 mm vs. 4.9 mm in T. uygur ), its elytra are wider (EL/EW, on average, 1.39 vs. 1.50; EW/PW 1.57 vs. 1.50; EW/HW 1.81 vs. 1.74, p≤0.001) and shorter (EL/PL 2.96 vs. 3.01 in T. uygur , p≤0.05), anterior margin of pronotum longer (mean for ratio PA/PB is 1.07 vs. 1.01 in T. uygur , p≤0.001), antennae longer (average values for ratios: EL/AL 1.01 vs. 1.04, p≤0.05, L3/W3 2.74 vs. 2.50, L3/L2 1.45 vs. 1.33 in T. uygur , p≤0.001), eyes smaller (means for ratios: L3/YL 1.23 vs. 1.08, YL/TL 1.03 vs. 1.11 in T. uygur , p≤0.01), discal pore 1 and all umbilicate pores, except for pore 5, located closer to the elytral base.

Distribution. T. tsanmensis sp. n. is known only from northern slopes of the eastern part of the Narat Mountain Range, Xinjiang, China ( Fig. 9 ).

Bionomics. The species occurred in screes near melting snow at elevations of 3000–3200 m.

Derivatio nominis. The species is named after the toponym “Tsanma”, a left tributary of the Kunges River.

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 7–8. Male genitalia of Trechus spp., paratypes (from Belousov & Kabak 2001): a—lateral view, b—dorsal view. 7—T. arshanicus Belousov & Kabak, 2001; 8—T. sinus Belousov & Kabak, 2001.

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.