Agonotrechus spinangulus, Belousov & Kabak & Liang, 2019

Belousov, Igor A., Kabak, Ilya I. & Liang, Hongbin, 2019, New species of the tribe Trechini from China (Coleoptera: Carabidae), Zootaxa 4656 (1), pp. 143-152 : 144-147

Agonotrechus spinangulus sp. n.

( Figs 1 , 2–4 )

Type material: Holotype: CHINA: 1(1) ♂, with label data “ China, Sichuan, Muli County, Liziping Xiang , Kangwu Pass , mixed forest, N 28.12630, E 101.15987 ”; “ 2012.VI.6, D, 3773 m, Yang Xiaodong leg., Institute of Zoology , CAS. [In Chinese]: Sichuan, Muli Xian, Kangwu Yakou” ( IOZ) . Paratypes: 1 ♀, collected in the same place as holotype, but 2012. VI.5, Huang Hao leg. ( IOZ) .

Description. Medium-sized and rather gracile species with relatively narrow head, discoid pronotum markedly constricted at base and ample elytra ( Fig. 1 ), body length 4.9–5.0 mm. Legs and antennae slender.

Color of dorsum amber-brownish, rather pale, with slight bronze metallic lustre; posterior portion of the head and, in male specimen, disc of pronotum darker; margins and suture of elytra somewhat paler. Legs and antennae unicolorous, pale-brownish.

Microsculpture of dorsum rather distinct (faint only on disc of pronotum), largely consisting of fine transverse lines, partially anastomosing and forming, on occiput, transverse meshes. Elytral surface with shallow tile-like sculpture pattern. All surface with micropunctures, clearly iridescent.

Head elongate, rather narrow compared to pronotum ( PW / HW 1.43–1.44), eyes medium-sized (YL/TL 1.16– 1.31, L3/YL 1.04–1.06), slightly convex; tempora long, subparallel, markedly convex in their posterior portion; neck rather narrow. Frontal furrows complete, deepest behind their mid-length, slightly sinuate in median portion. Ophthalmic lobes large, more than twice wider than frons between frontal furrows; each ophthalmic lobe with oblique impression connecting anterior supraorbital pore and frontal furrow at level of parietal impression, the latter distinct. Two supraorbital setae located in lines subparallel to body axis. Mandibles slender, not large, gently curved inward. Exterior edge of mandibles, apart from one conventional scrobe seta, with one long and occasionally 1–2 shorter additional setae. Right mandible with a tooth, deeply concave on inner margin. Labial tooth simple, acute, pointed apically, directed slightly downward. Labial suture very fine but traceable. Four submental setae (median pair absent). Maxillary palpi completely glabrous. Penultimate segment of the labial palpi quadrisetose. Ligula triangular-shaped, with two long apical setae and shorter lateral setae. Paraglossae moderately long, slender, slightly curved and distinctly pubescent.Antennae longer than average for the genus, longer than elytra, AL/EL 1.14 in male and 1.05 in female, antennomeres rather stout, L3/ W3 2.44 –2.53; L3/L2 1.31–1.41.

Pronotum slightly transverse ( PW / PL 1.15–1.18), marginally more constricted to apex than to base ( PW / PB 1.47–1.49), with base somewhat wider than the apex ( PB /PA 1.11–1.15); sides broadly rounded for most of their length except for a short and deep emargination just before hind angles. The latter large and acute, with apices attenuated and pointed. Basal margin convex medially and emarginate laterally. Anterior margin straight, front angles broadly rounded and slightly protruding anteriad. Lateral groove wide but much narrower than in most congeners, lateral margins markedly reflexed. Basal foveae large and deep. Prebasal transverse impression shallow, with a deep and small impression on each side approximately in middle between basal fovea and median line. The latter continuous, rather deep, especially at base and before its mid-length. Apical transverse impression shallow. Basal surface smooth. Discal foveae absent. Two lateral setiferous pores on each side of pronotum, the anterior one clearly shifted anteriad (PSa 25.3–26.8%), and the posterior one at narrowest point of pronotum.

Elytra subconvex ( EL /BH 2.71 in male and 2.53 in female), broad, ovate, ( EL / EW 1.38–1.39) ( EL / PL 2.48 in male and 2.54 in female; EW/ PW 1.52 in male and 1.59 in female; EW/HW 2.18 in male and 2.28 in female), with distinct humeri and maximum width near their mid-length. Basal margins obliquely convergent anteriad. Preapical sinuation shallow, elytral apices obtuse, conjointly rounded. Lateral groove of average width, approximately as wide as that of pronotum, clearly broadened at humeral area, margins markedly reflexed. Basal border reaching the base of stria 5. Elytral striae reduced, only stria 1 deep and distinct throughout, striae 2–6 very shallow; others evanescent; all striae faintly punctured. Interspaces flat, of subequal width except for interspace 1, which is slightly narrower. Apical recurrent striole short, shallowly impressed, subparallel to body axis anteriorly. Paracutellar striole rather short, parascutellar setiferous pore present. Apical triangle markedly elongate, angulo-apical pore approximately in middle between elytral suture and exterior pore. Preapical pore attached to stria 2 clearly before anterior termination of apical striole. Two discal setiferous pores in anterior half of elytra, both attached to stria 3; discal formula: D1 16.9–17.4%, D2 44.6–47.8%, DP 83.6%. Umbilicate series clearly divided into three typical groups, all pores subequidistant within each of these groups, except for the preapical one with pores slightly more spaced; umbilicate formula U1–8: 9.5–9.7%, 13.4–14.4%, 18.7–19.5%, 23.4–24.6%, 50.7–52.3%, 56.2–57.7%, 80.5–80.6%, 87.1–88.2%.

Ventral surface: metepisternites smooth, approximately 1.5 times as long as wide. One paramedian seta on each side of abdominal sternites. Anal sternite with two setae in male and four setae in female.

Legs: fore tibiae markedly grooved (nearly carinate) on exterior surface, distinctly pubescent anteriorly. Male protarsi with two basal segments moderately dilated and each provided with a narrow band of adhesive setae shifted inward, more markedly so in segment 1. Hind tibia: EL/HTi ratio is 1.65 in male and 1.78 in female; HTi/HTa— 1.45 in female.

Aedeagus ( Figs 2–3 ) very small, moderately curved, with short apical portion clearly bent downward in lateral view. In dorsal view, the aedeagal tube slender, gradually and slightly widened distally, with very short, obliquely truncate and broadly rounded apex. Sagittal aileron not large. Endophallus armature spatulate, moderately sclerotized, its ventral margin distinctly waved. Parameres subequal in size, with rather stout apical portion, their ventral margin barely concave, each paramere bearing 4 apical setae. Urite ( Fig. 4 ) subtriangular.

Comparative notes. Among all members of Agonotrechus Jeannel, 1923 sensu lato ( Deuve et al., 2016), the new species is no doubt most similar to A. reflexicollis ( Uéno, 1977) , described in the genus Bhutanotrechus Uéno, 1977 . Both species share the following characters: oblong and not convex habitus with slender appendages, similar brownish color with specific luster, very similar elongate head with small eyes and long nearly parallel-sided tempora; elytral striae nearly effaced, barely traceable, slightly waved and without distinct punctures (except for stria 1 which is well-impressed), two discal setiferous pores and one preapical pore and flat interspaces. However, A. spinangulus sp. n. differs readily in having only 4 submental setae vs. 6 in its counterpart ( Uéno 1977), pronotum less transverse and much more markedly constricted at base, with hind angles more acute and produced, and apical lamella of aedeagus shorter and more widely rounded in dorsal view.

As for the Chinese congeners, the new species seems to be rather isolated and differs from all of them in having the pronotum less transverse, markedly constricted toward its base, with sides deeply emarginated before the hind angles, which are much more acute ( Fig. 1 ). Apart from the peculiar shape of the pronotum, the new species is easily distinguishable by the very long and nearly parallel tempora and very short apex of the aedeagal median lobe, both in lateral and particularly in dorsal views ( Figs 2–3 ).

To summarize, A. spinangulus sp. n. seems to be rather isolated within the genus Agonotrechus , its external similarities with A. reflexicollis are mostly of adaptive nature and are not supported by the submental chaetotaxy and structure of the male genitalia. In this respect, the discovery of this species bridges to some extent the gap between Agonotrechus and Bhutanotrechus and argues in favor of the Th. Deuve’s synonymy of these two genera ( Deuve et al 2016).

Distribution. Kangwu Pass, Liziping Town, Muli County, southern Sichuan.

Bionomics. The species was found in a mixed forest at an elevation of 3773 m a.s.l.

Derivatio nominis. The species’ epithet refers to the conspicuous, acute hind angles of the pronotum giving this species a distinctive appearance.

Figures

FIGURE 1. Agonotrechus spinangulus sp. n., female paratype, habitus.

FIGURES 2–4. Agonotrechus spinangulus sp. n., holotype, male genitalia and urite: 2—lateral view; 3—dorsal view; 4— urite.