Dactylotrechus yalongensis Belousov & Kabak

Belousov, Igor A. & Kabak, Ilya I., 2014, A new genus of trechine beetles, Puertrechus gen. n., with two new species and a new species of Dactylotrechus Belousov et Kabak, 2003 from Southern China (Coleoptera: Carabidae: Trechinae), Zootaxa 3856 (3), pp. 375-398 : 377-382

Dactylotrechus yalongensis Belousov & Kabak , sp. n.

( Figs. 1–3 )

Type material: Holotype: 1(1)♂, “ China, Sichuan Province, SW Mianning Town, 28º13´19´´ N / 101º43´21´´ E, H= 3700 m, 0 7.07.2011, Belousov & Kabak leg.” ( ZISP). Paratype: 1(1)♀, collected together with holotype ( CBK).

Description. Medium-sized species, body length 4.10–4.25 mm. The morphometric characters of this species are given in Table 1 . Habitus ( Figs. 1–2 ) briefly ovate, strongly convex, with relatively strong constriction at pronotal base. Legs and antennae rather thin, medium in length. Color of dorsum blackish piceous, translucent with reddish tinge. Head slightly obscured in its median part, labrum darkened medially, mandibles weakly paler than the remainder of head; pronotum pale-reddish in apical part, at base, along median line and along margins. Elytra vaguely reddish at base, margins and suture. Legs and antennae unicolorously reddish-brown, only femora in their proximal parts feebly darkened.

Head rather large, widest across eyes. Frontal furrows strongly sinuate in anterior third, subparallel-sided in median portion, gradually arcuate posteriorly, deepest at level of clypeal suture and at level of parietal impression, becoming increasingly shallower behind the latter. Frons strongly convex. Parietal impression shallow but distinguishable. Eyes rather large, evenly convex, clearly longer than tempora, the latter rather weakly convex, glabrous. Supraorbital carina well developed, rather high, becoming less elevated towards the eyes. Two clypeal setae on each side of head, two usual supraorbital setiferous pores of which the anterior one is strongly foveolate. Labrum sexsetose, with angular emarginate anterior margin. Mandibles rather slender, regularly curved for most of their length, their apices distinctly attenuated and more strongly curved inward. Tooth on the right mandible tridentate, proximal denticle being fused with the rest of the tooth, incision between it and median denticle deepest. Both proximal and distal denticles acute and produced, distal one biggest, median one shortest, subrectangular. Tooth on the left mandible bidentate, with proximal denticle weakly longer. Maxillary palpi glabrous or at most with a rudimentary seta located in apical portion of penultimate segment. All segments rather thick, the ultimate weakly attenuating in the apical half; penultimate strongly constricted towards the base and deeply concave along inner margin; inner margin of the second segment S-shaped, its outer margin evenly convex. Labial palpi relatively robust, ultimate segment fusiform, asetose, approximately as long as penultimate; its maximum width near midlength; penultimate segment quadrisetose (two setae located on the inner margin, of which the posterior one is slightly before the mid-length of the segment, one seta on the outer margin of the segment at the level of inner anterior seta, and one seta in usual subapical position). Glossum triangular-shaped, with a couple of long median setae and a few shorter lateral setae on each side. Paraglossae rather long, weakly curved, feebly pubescent internally. Mentum and submentum fused in a semicircular structure. Six rather long submental setae, of which the lateral are the longest. Anterior margin of labial emargination thickly bordered, labial tooth rather long, produced forwards and upwards, not grooved ventrally but with a small fovea in the distal part, its apex is blunt or weakly notched.

Pronotum distinctly transverse, strongly constricted toward base and slightly constricted toward apex. Pronotal sides nearly straight in anterior quarter, evenly rounded in broadest part at level of anterior third of pronotum and sinuate posteriorly. Lateral border distinct only in anterior part of pronotum, disappearing behind mid-length; at most, partly traceable near posterior lateral seta. Lateral groove rather wide in anterior third of pronotum, nearly disappearing at level of posterior termination of lateral border and further posteriad again well-impressed and fused with basal fovea of pronotum forming a sharp common angular impression. Lateral sides of prosternum shifted onto dorsal surface in a way that posterior lateral seta is markedly displaced inward. Outer margin of pronotum in its posterior third is made up of lateral portion of prosternum, which is freely visible from above. Hind angles as small processes produced backwards, triangular-shaped in lateral view, their lateral surface visible from above. Prebasal transverse impression smooth and shallow laterally, reduced medially, joining lateral foveae. Apical transverse impression reduced, barely traceable laterally. Three (seldom two on one side) anterior lateral setiferous pores located in the anterior third of the pronotum. Basal margin straight medially, deeply and briefly emarginate laterally near the hind angles. Anterior margin rectilinear, anterior angles of pronotum not protruding. Surface of pronotum smooth.

Elytra broadly ovate, convex, with maximum width slightly behind mid-length, their lateral slopes very steep. Humeri distinct though rounded. Apices of elytra conjointly rounded, preapical sinuation weak. Lateral groove rather wide throughout its whole length, becoming narrower toward its anterior termination, but completely visible from above even here; lateral margins moderately reflexed upward. Discal elytral striae effaced, stria 8 traceable in posterior part of elytra, extending anteriad up to umbilicate pore 5. Parascutellar striole shallow, deeper in anterior part where it forms a comma-like sharp impression. Apical striole relatively long, broadly curved to nearly straight, directed latero-anteriad, gradually disappearing and curved inward anteriorly, its anterior termination at level of umbilicate pore 8; apical carinula wide, evenly convex. Normally seven, seldom eight foveolate discal setiferous pores on each elytron. Their distribution on disc very irregular, varying on left and right elytron and different in two available specimens. In the male, these pores are arranged mostly in three longitudinal rows (left: 2–2–4, right: 3–2–2), inner row located on site of the third interspace between vestigial striae 2 and 3. In the female specimen, the discal setiferous pores are arranged principally in two longitudinal irregular rows (left: 2–5, right: 3–3), the middle pores of the inner rows being located in stria 3, both the anteriormost and posteriormost pores slightly shifted inward, the latter located in position typical of the preapical pore at level clearly anteriad of the anterior termination of the recurrent striole. Exterior row most stable, located approximately on site of stria 5 and consisting of two (three on one elytron of one specimen) pores confined to anterior third of elytron. Angulo-apical pore attached to apical border of elytron much further from suture than from apical margin and located only weakly closer to suture than to exterior pore. Preapical and angulo-apical pores located on lines clearly convergent posteriad. Pores of umbilicate series well aggregated, umbilicate pores 1, 4 and 7 markedly removed from lateral margin. All umbilicate pores of the humeral and median groups evenly distributed within their groups; pores 7 and 8 most spaced.

All dorsum smooth and shining, without any trace of microsculpture but with well-developed micropunctures rather densely disseminated throughout elytra and markedly more sparsely distributed on head and pronotum. Under-side mostly smooth, traces of microsculpture visible only fragmentary, mostly between hind coxae. Suture between second and third visible abdominal sternites interrupted medially.

Anal sternite with two pairs of setae in female and one pair in male; visible abdominal sternites 3-5 with one pair of paramedian setae.

Legs rather long. Femora densely pubescent, with three longer setae along lower margin. Tibiae nearly straight, strongly and densely pubescent, including anterior surface of front tibiae, exterior surface of the latter grooved, at least, in middle part. Male protarsi with two basal segments dilated, segment 1 barely longer than wide, segment 2 clearly transverse, both with short and stout inner tooth, their under-side with well-developed adhesive appendages.

Aedeagus ( Fig. 3 ) long and slender, step-like curved at basal third, with distinct sagittal aileron and apical portion attenuated and weakly S-curved, with a small knobbed apex. Basal orifice clearly emarginate. Endophallus armature well-developed, pairwise, the right piece long, heavily sclerotized and markedly projecting beyond apical orifice while the left one much shorter, less distinctly outlined, rounded apically. Parameres slender, curved, each bearing 3–4 apical setae; left one clearly longer, with small but distinct ventral apophysis.

Sexual dimorphism. Though only one male and one female are presently availble, some differences in proportions between these are rather typical of most trechine beetles: antennae and legs are marginally longer (YL/ L3 1.01 vs. 1.19; L3/W3 2.29 vs. 2.16; EL/TiL 1.84 vs. 1.89 respectively), elytra slightly larger (EL/PL 2.59 vs. 2.55) in the male specimen while head is somewhat larger in the female specimen (EW/HW 2.02 in female vs. 2.07 in male). On the contrary, the female specimen turns out to be marginally larger what, according to our experience, is not often observed in Trechini .

Comparative notes. The new species differs from the only known congener, Dactylotrechus setosus Belousov & Kabak, 2003 , in having much more robust body, with shorter elytra, darker coloration of the upper-side (black piceous versus dark reddish-brown in D. setosus ), only three (seldom two) anterior lateral pores on the pronotum instead of four or five in D. setosus and less numerous setiferous pores on the elytra (7–8 setae on each elytron versus normally more than 20 in D. setosus ) (see Figs. 1–2 and 4). The shape of the median lobe of the aedeagus is very similar, though marginally longer, the endophallus armature, compared to D. setosus , is more clearly sclerotized, with the right piece attenuating and extending beyond the apical orifice while poorly sclerotized and not extending beyond the apical orifice in D. setosus .

Distribution. Right bank of the Yalong River, SW of Mianning City, Sichuan Province, China ( Fig. 5 , white circle).

Bionomics. The species was sifted from flood debris on banks of a small brook located within a mountain forest at an elevation of 3700 m.

Figures

FIGURE 1. Dactylotrechus yalongensis sp. n., male holotype, habitus.

FIGURE 2. Dactylotrechus yalongensis sp. n., female paratype, habitus.

FIGURE 3. Male genitalia of Dactylotrechus yalongensis sp. n.: a—lateral view, b—dorsal view, c—parameres, d—genitalic sac.

FIGURE 5. Distribution of Dactylotrechus species. 1 (black circle) — Dactylotrechus setosus Belousov & Kabak, 2003. 2 (white circle) — Dactylotrechus yalongensis sp. n.

Tables

TABLE 1. Morphometric characters of Dactylotrechus yalongensis sp. n.

Indices PW/HW	Range 1.25–1.28	Indices EL/BH	Range 2.04–2.05
YL/TL	1.52–1.73	EL/TiL	1.84–1.89
YL/L3	1.01–1.19	TiL/TaL	1.38–1.44
AL/EL	1.00–1.02	EL/BH	2.04–2.05
L3/L2	1.23–1.25	(DP/EL) x 100	78.5–81.5
L3/W3	2.16–2.29	(U1/EL) x 100	10.1–10.9
PW/PL	1.21–1.23	(U2/EL) x 100	14.3–14.5
PW/PB	1.57	(U3/EL) x 100	19.9–20.8
PW/PA	1.29–1.35	(U4/EL) x 100	26.8–27.2
EL/EW	1.29–1.30	(U5/EL) x 100	57.1–57.4
EL/PL	2.55–2.59	(U6/EL) x 100	62.8–63.7
EW/HW	2.02–2.07	(U7/EL) x 100	74.9–76.8
EW/PW	1.61–1.63	(U8/EL) x 100	83.1–84.5