Trechus cratocephalus 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 : 64-67

Trechus cratocephalus Belousov & Kabak , sp. n.

( Figs. 12 , 18–21 )

Type material: Holotype: 1(1) ♂, “ CH, Xinjiang , W of Narat Mt. R, 7–9 km SE of Sarkhob village, 42°47´15´´

N / 81°14´45´´ E— 42°46´00´´ N / 81°15´20´´ E, 2200–2550 m, 23.07.2003, Kabak I.I. leg.” ( ZISP) . Paratypes: 10(5) ♂♂, 4♀♀, collected with holotype ( IZAS, MPU, BMNH, ZSM, CAG, CBK, CJS) ; 9(7) ♂♂, 3♀♀, “ CH, Xin- jiang, W of Narat Mt. R, 10 km SE of Sarkhob village, 42°45´40´´ N / 81°15´35´´ E— 42°45´25´´ N / 81°15´40´´ E, 2800–3000 m, 24.07.2003, Kabak I.I. leg.” ( ZISP, CAK, CBK, CDW, CVZ) .

Description. Small-sized species with subparallel and slightly depressed body. Legs and antennae rather short. Color of dorsum varying from reddish-brown to testaceous reddish with darker head (in paler specimens, only posterior part of head obscured) and disk of elytra except for suture, margins, and occasionally base of elytra; antennae vaguely obscured in distal parts; legs uniformly pale testaceous.

Head extremely large (HW/PW ratio 1.14–1.21, on average, 1.18) evenly and moderately convex. Frontal furrows evenly impressed, regularly arcuate and markedly approaching each other in median part. Frons narrow. Supraorbital setiferous pores located in lines convergent posteriad; both slightly foveolate. Posterior supraorbital pore located at level significantly behind posterior margin of eye. Eyes small, gradually protruding; tempora long, evenly convex, clearly pubescent. Mandibles stout, straight for most of length, sharply curved only at apices.

Pronotum markedly transverse, flat, with maximum width before mid-length. Sides broadly rounded anteriorly, either rectilinearly convergent posteriorly or shallowly sinuate before hind angles. Hind angles obtusangular, with pointed apices. Basal margin straight medially, emarginated laterally. Apical margin rectilinear; front angles completely rounded off. Prebasal transverse impression vague, located far from basal margin and parallel to it, markedly curved laterally in basal foveae. Latter large and moderately deep. Basal surface coarsely rugose. Lateral groove of medium width, dilated in posterior part; margins slightly reflexed. Median line shallow, becoming deeper behind mid-length and at base. Discal foveae indistinct. Preapical transverse impression distinct laterally, more or less reduced medially.

Elytra parallel-sided, depressed on disk, with maximum width at mid-length. Prehumeral margins oblique. Humeri marked. Elytra broadly rounded at apex, nearly truncate. Preapical sinuation shallow. Two discal setiferous pores in stria 3, anterior one usually at level between umbilicate pores 3 and 4, posterior one slightly before umbilicate pore 5. Preapical pore located on interspace 3, in apical cross of stria 2 and 3, at level slightly before anterior termination of apical striole, in middle between umbilicate pores 7 and 8 or closer to the former. Apical triangle markedly elongate, its inner side approximately parallel to elytral suture; exterior pore located at level clearly behind umbilicate pore 8. Umbilicate pores well-aggregated. Elytral striae shallow and regular, though exterior ones less impressed (nonetheless, usually even stria 7 traceable for most of its length); occasionally exterior striae reduced: in this case stria 4 significantly shallower than striae 1–3, stria 7 barely distinguishable. All striae finely punctured. Interspaces flat. Interspace 2 less than one and a half times as wide as interspace 3. Striolation on apical slope as follows: 2x 3 and prolonged up to elytral apex, 3x 4, 5x 6 at level markedly behind umbilicate pore 6. Parascutellar striole short. Apical striole rather short, gently impressed, terminated anteriorly near level between umbilicate pores 7 & 8, joining striae 7 or 5 anteriorly. Lateral groove narrow and evenly widened posteriad, margins markedly reflexed.

Fore tibiae clearly grooved, without distinct hairs on anterior surface. Male foretarsi with two basal segments markedly dilated and dentate; both segments 1 and 2 clearly transverse.

Microsculpture rather shallow, consisting of isodiametric meshes on head, clearly transverse meshes on pronotum, and irregular meshes coupled with serrate lines on elytra. Microsculpture suppressed on median part of frons and pronotum. Micropunctures distinct throughout.

Aedeagus ( Figs 18–21 ) not large, rather thick, markedly curved, its ventral margin in distal third nearly straight, apex simple. Sagittal lobe indistinct. In dorsal view, aedeagus parallel-sided for most of its length, triangular shaped at apex. Endophallus armature consisting of scaly areas with a well-defined hemisphere-like structure in proximal portion (this piece is normally open toward right wall of aedeagus—see Figs 18, 19, 21 ). Parameres slender, faintly curved in distal portions, each bearing 4 apical setae which are nearly reaching the apex of aedeagus; left paramere longer, with slight ventral apophysis.

Comparative notes. In its subparallel and depressed habitus, rather pale color of dorsum, small eyes as well as even and slightly waved striation of elytra, the new species is similar to the sympatric T. aghiazicus sp. n. described above, but differs in much bigger head, shape of pronotum with sides more markedly constricted to base, elytra with broadest point clearly behind their mid-length, posterior elytral setiferous pore shifted posteriad, much closer to the level of umbilicate pore 5 ( Fig. 12 vs. Fig. 11 ) and quite different structure of the male genitalia ( Figs 18–21 vs. Figs 15–17 ).

However, aside from the rather pale color of the dorsum, T. cratocephalus sp. n. seems to be much closer to T. mogul Belousov & Kabak, 2001 . This viewpoint is supported by the identical shape of both the pronotum and the elytra, and especially by the similar structure of the male genitalia. However, T. cratocephalus sp. n. differs from the latter species in having much lighter, brownish testaceous color of the dorsum, larger head and a particular semispherical structure in the endophallus armature ( Figs 18–21 ), a unique character among all Trechus species known so far from Central Asia. Additionally, the distal portion of the ventral side of aedeagus is not clearly convex in T. cratocephalus sp. n. In this respect it seems to be more similar to T. zhaosuensis Deuve & Tian, 2004 , another species closely related to T. mogul described from the same area ( Deuve 2004). Through the courtesy of Dr. M.-Y. Tian (Guangzhou, China) we were able to examine the holotype of T. zhaosuensis . This specimen, though pale testaceous, is teneral and the species seems to be in fact, based on our knowledge about morphology and distribution of related taxa in this area, rather dark colored, similar to T. mogul and not to T. cratocephalus sp. n. Apart from this, T. cratocephalus sp. n. differs readily from the latter species, once again, in its hypertrophied head and the hemispherical structure (with circular projection in lateral view) of the endophallus armature. It is worth noting that T. cratocephalus sp. n. co-exists at all collecting sites with members of the T. mogul — T. zhaosuensis lineage, which seems to be split into a series of allopatric forms.

Distribution. Western extremity of the Narat Mountain Range from the vicinity of the Sarkhob Village to the Koekbel Pass.

Bionomics. The species has been found in humid meadow biotopes in the forest and low-alpine zones, within the range of elevations between 2200–3000 m a.s.l. The species was mostly collected from under stones.

Derivatio nominis. The species is named “cratocephalus” to stress its remote similarity, in the large size of its head, with members of the subgenus Cratocephalus Kirsch, 1859 of the genus Carabus Linnaeus, 1758 occurring in the same area.

Figures

FIGURES 11–12. Trechus Clairville, 1806, habitus, males, paratypes. 11, T. aghiazicus sp. n.; 12, T. cratocephalus sp. n.

FIGURES 13–21. Male genitalia of Trechus spp. n., paratypes: a—lateral view, b—dorsal view. 13—T. saluki sp. n.; 14—T. kashensis Belousov & Kabak, 2001 (from Belousov & Kabak 2001); 15–17—T. aghiazicus sp. n.; 18–21—T. cratocephalus sp. n.