Stenus (Nestus) canosus, Ryvkin, 2012

Ryvkin, Alexandr B., 2012, New species and records of Stenus (Nestus) of the canaliculatus group, with the erection of a new species group (Insecta: Coleoptera: Staphylinidae: Steninae), European Journal of Taxonomy 13, pp. 1-62 : 28-30

Stenus (Nestus) canosus sp. nov.

( Figs. 4A – B , 5D )

Material examined

CHINA: Holotype: ♂, ‘ NW China , Xinjiang Uygur | Zizhiqu , Tien | Shan, Southern slope of Narat Mt Ridge : | Koktau Mts , right confluent | of Koksu River , 3200 m, stone-| sandy bank of rill with sedge tussocks and | small willows. 25.07.[20]01. [S.V.]Saluk. No 11’ <printed label in Russian>, ‘HOLOTYPUS’ <my standard printed red label>, ‘ Stenus HT | canosus sp. n. | A.B. Ryvkin det., 2010’ <my standard determinative label> ( ZMMU) .

Differential diagnosis

This new species is externally very similar to S. (N.) canaliculatus Gyllenhal, 1827 and differs from it by the character of the puncturation, which is much coarser, more sparse and irregular, by the less developed microsculpture, by the median furrow of pronotum, which is deeper and broader, and by the shape of the aedeagus. External differences from all the known species of the canaliculatus -group are given in the key below.

Etymology

The name of this species is the Latin adjective “ canosus ” (grey-haired).

Description

LENGTH. 4.0 mm (with abdomen extended).

COLORATION. Black, distinctly shining, with moderately long and dense silvery pubescence. Legs dark brown with knees somewhat darkened, brownish-black. Antennae dark brown, with segments 1–2 pitchy-black and club vaguely infuscate; 1st segment of maxillar palpi yellow, 2nd brown with yellow base, 3rd dark brown with very base yellowish.

HEAD. Distinctly broader than pronotum (50:44), somewhat narrower than elytra between humeri (50:53), much narrower than those in their broadest part (47:54). Front feebly evenly convex, with very vague and shallow lateral impressions distinguishable mainly between antennal tubercles and eyes. Puncturation moderately dense, somewhat irregular, evidently smaller and denser between antennal tubercles, partly nonrugosely confluent both there and at periocular areas, without distinct smooth spots and strips, but obviously sparser and greater in the middle; average diameter of punctures in the middle distinctly larger than the greatest cross-section of antennal segment 3. Frontal slope before antennal fossae rather flat. Anterior margin of labrum with small median notch. Antennae moderately long, scarcely reaching middle of pronotum. Length proportions of antennal segments 2–11 = 6:5:6:4:4:4:3:4:4.5:6; segments of club longer than broad (4:3, 4.5:4, 6:4).

PRONOTUM. A bit longer than broad (45:44), broadest near middle of length, narrowed feebly convexly towards anterior margin and concavely towards posterior one. Longitudinal median furrow deep and sharp over entire length except for very anterior piece. Laterobasal depressions very shallow, nearly vanishing. Puncturation deep and irregular, partly nonrugosely confluent; punctures distinctly larger than those of head.

ELYTRA. A bit broader than long (60:58), much longer than pronotum (58:45), at suture distinctly longer than the latter (48:45). Humeri anglarly rounded, lateral sides uniformly moderately divergent posteriorly (53:60). Humeral and sutural depressions feeble but evident in anterior half of disk. Puncturation deep, much more regular, evidently larger in diameter than that of head and pronotum, sometimes confluent, but not forming long furrows.

LEGS. Fairly short; metatibia about 1/3 longer than metatarsus (40:29); segment 1 of metatarsi about as long as segment 5 (8:8).

ABDOMEN. Moderately convex, with well developed paratergites and two pairs of keels at bases of anterior visible tergites. Lateral sides feebly uniformly convergent. Posterior margin of tergite 7 with fine light fringe. Puncturation of tergites evidently smaller than that of head and pronotum; on anterior visible tergites much denser and smaller laterally, medioposteriorly with some smooth interstices distinctly wider than average diameter of punctures.

MICROSCULPTURE. Very fine mesh-like ground sculpture visible between punctures, mainly on elytra and abdominal tergites 8–9, as well as on lateral parts of head, pronotum and anterior abdominal tergites, median parts of abdominal tergites quite smooth or slightly irregularly netted only on edges of punctures.

MALE. Meso- and metatibiae without specific characters; 8th abdominal sternite without conspicuous impressions and keels, its posterior margin with very broad and not deep angularly-rounded emargination; abdominal sternite 9 as in Fig. 5D ; aedeagus as in Fig. 4A, B.

FEMALE. Unknown.

Remarks

No records of S. (N.) canaliculatus were previously known from China or from adjacent countries of Central Asia. The capture of S. (N.) canosus sp. nov., which is closely related to S. (N.) canaliculatus , proves that their common ancestor was recently widely distributed throughout these spacious territories.

Figures

Fig. 4. – A–B: Stenus (Nestus) canosus sp. nov.: ♂ (holotype). A. Aedeagus, ventral view. B. Apical part of aedeagus, ventral view. – C–D: S. (N.) canalis sp. nov.: ♂ (holotype). C. Aedeagus, ventral view. D. Apical part of aedeagus, ventral view. [Note that the difference in shape of the apical lobe compared to that in C is due to the level of magnification.] – Scales = 0.1 mm.

Fig. 5. ♂ copulative structures. A–E: Abdominal sternite 9. A. Stenus (Nestus) latipennis J. Sahlberg, 1880 (Russia: Krasnoyarsk Territory: Mirnoye). B. S. (N.) illusor Ryvkin, 1987 (Russia: Magadan Area: 2 km W of Splavnaya). C. S. (N.) delitor sp. nov. (holotype). D. S. (N.) canosus sp. nov. (holotype). E. S. (N.) canalis sp. nov. (holotype). F. S. (N.) caseyi Puthz, 1972 (U.S.A.: Michigan: Berrien Co.). Aedeagus, ventral view. – Scales = 0.1 mm.