Stenus (Nestus) alopex Ryvkin 2012, sp. nov.

Stenus (Nestus) alopex sp. nov.

(Fig. 3 A–C)

Material examined

RUSSIA: Holotype: ♂, ‘ Putorana Highland, Ayan Lake near | source of Ayan River. | Lakeshore osier | tundroid. 22.08.1983. | K.Yu. Eskov. #74.’ <printed label in Russian>, ‘HOLOTYPUS’ <my standard printed red label>, ‘ Stenus HT | alopex sp. n. | A.B. Ryvkin det., 1994’ <my standard determinative label> (ZMMU). – Paratypes: 1 ♂, ‘ Putorana Highland, Ayan Lake near | source of Ayan River. | Lakeshore tundroid. | 23.08.1983. | K.Yu. Eskov. #75.’ <printed label in Russian> (AR); 1 ♀, ‘ Putorana Highland, Ayan Lake. | Alpine belt. | 28.07.1983. | K.Yu. Eskov. #54.’ <printed label in Russian> (AR); 2 ♂♂, ‘ Taymyr, Khatangskiy District, | Taymyrskiy Nature Reserve, | Ary-Mas: right bank of Novaya River | near field research station. [Mosses and litter under dwarf Salix sp. and Betula ? exilis] near small rill. | 17.07.1992. A. Ryvkin. #93.’ <printed label in Russian> (IRSN, MTD); 1 ♂, 1 ♀, ‘ Taymyr, Khatangskiy District, | Taymyrskiy Nature Reserve, | Ary-Mas: right side of Novaya River | near Ulakhan-Yuryakh River mouth. Bank | of [Novaya] River [: shingles, sand]. 19.07.1992. A. Ryvkin. #98.’ <printed label in Russian> (AR); 2 ♀♀, ‘ Taymyr, Khatangskiy District, | Taymyrskiy Nature Reserve, | Ary-Mas: right side of Novaya River | near Ulakhan-Yuryakh River mouth. | Swampy floodplain of [small] rill[: mosses and litter among Carex spp., Salix spp., Betula ? exilis etc.]. | 19.07.1992, A. Ryvkin. #99.’ <printed label in Russian> (AR); 1 ♀, ‘ Taymyr, Khatangskiy District, | Taymyrskiy Nature Reserve, | Ary-Mas: right bank of Novaya River | near field research station. Shore of ‘small’ | lake [ESE of Ulakhan-Yuryakh River mouth. Mosses, litter and sweeping at lake shore: Carex spp., Comarum palustre]. 20.07.1992. A. Ryvkin. #104.’ <printed label in Russian> (AR); 2 ♂♂, ‘ Taymyr, Khatangskiy District, | Taymyrskiy Nature Reserve, | Ary-Mas: right bank | of Novaya River, near lake between | small rill and Ulakhan- | Yuryakh River.’, ‘ Mosses and litter under Larix [gmelinii] with | Cassiope tetragona, Pyrola | sp., Vaccinium vitis-idaea etc. | on S slope. 23.07.1992. | A.B. Ryvkin. #115.’ <printed labels in Russian> <one specimen without head and pronotum> (AR); 1 ♂, 1 ♀, ‘ Taymyr, Khatangskiy District, | Taymyr Nature Reserve, | Ary-Mas: right bank | of Novaya River near mouth of Ulakhan- | Yuryakh River (watershed of Novaya River and | small rill).’, ‘ Mosses and litter on glade | in sparse larch forest | with Betula ? exilis, Salix spp., | Vaccinium vitis -idaea, V. | uliginosum, Pyrola sp., | Cassiope tetragona, Cladonia | spp., Carex spp., etc. | 24.07.1992. A.B. Ryvkin. #118.’ <printed labels in Russian> (AR). — The paratypes listed above are also provided with both “ PARATYPUS ” printed red label and my standard determinative label (‘ Stenus | alopex sp. nov. | A.B.Ryvkin det., 1994’) for each lot. — 1 ♀, Chukot Peninsula, 78-84, Ayopechan Island, Ust’-Chaun, 19 Jul. 1978, E.G. Matis leg. <?> (AR).

Differential diagnosis

This species resembles S. (N.) canaliculatus Gyllenhal, 1827 and can be distinguished from it by the narrower and shorter elytra, by the much elongated pronotum, by the character of puncturation, 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 specific name is derived from the Latin generic name of the arctic fox Alopex lagopus (Linnaeus, 1758).

Description

LENGTH. 3.2–3.9 mm (the last value for the specimen with abdomen extended).

COLORATION. Black, moderately shining, with moderately long and dense greyish- or yellowish-silvery pubescence. Legs pitchy black, tibial apices and tarsi somewhat lighter. Antennae pitchy brown, with segments 1–2 black and club vaguely infuscate; 1st segment of maxillar palpi yellow, 2nd brown with yellowish base, 3rd dark brown, with base a bit lighter.

HEAD. About 1/5 to 1/6 broader than pronotum (47:39), exactly as broad as elytra between humeri (47:47), distinctly narrower than those in broadest part (47:54). Front feebly evenly convex, with very vague and shallow lateral impressions distinguishable only between antennal tubercles and eyes. Puncturation moderately dense and regular, nonconfluent, as a rule, except of periocular areas, without smooth spots and strips; average diameter of punctures about as large as basal cross–section of antennal segment 3. Frontal slope before antennal fossae rather flat. Anterior margin of labrum with a small median notch. Antennae moderately long, reaching the middle 1/3 of pronotum. Length proportions of antennal segments 2–11 = 6:5:4.5:5:4:4:3:3.5:4.5:4; segments of club a little longer than broad (3.5:3, 4.5:4, 4:3.5).

PRONOTUM. Evidently longer than broad (45:39), broadest near middle, narrowed feebly convexly towards anterior margin and feebly concavely towards posterior one. Longitudinal median furrow not deep but evident over almost entire length of disk. Laterobasal depressions very shallow, nearly vanishing. Puncturation dense and fairly deep, sometimes nonrugosely confluent near midline; punctures somewhat larger than those of head.

ELYTRA. A bit broader than long (54:52), distinctly longer than pronotum (52: 45 in holotype), at suture nearly as long as the latter (46: 45 in holotype). Humeral angles short but evident, lateral sides uniformly moderately divergent posteriorly (47:54). Humeral and sutural depressions nearly absent. Puncturation deep and fairly regular, evidently larger in diameter than that of pronotal disk, sometimes confluent, but not forming long furrows.

LEGS. Fairly short; segment 1 of metatarsi about as long as segment 5.

ABDOMEN. Moderately convex, with well developed paratergites and two pairs of keels at bases of anterior visible tergites. Lateral sides nearly parallel, feebly convergent in apical part. Posterior margin of tergite 7 with fine light fringe. Puncturation of tergites much smaller than that of head and pronotum, on anterior visible tergites denser laterally, medioposteriorly with some interstices comparable to diameter of punctures.

MICROSCULPTURE. The whole dorsal side with fine and dense ground sculpture visible throughout.

MALE. Meso- and metatibiae without specific characters; posterior margin of 8th abdominal sternite with a fairly broad but not deep angularly-rounded emargination, without deep impressions and keels, slightly depressed in posterior half; abdominal sternite 9 as in Fig. 3C; aedeagus as in Fig. 3A, B.

FEMALE. Posterior margin of 8th abdominal sternite angularly rounded.

Remarks

This new species seems to be a late derivative of S. (N.) canaliculatus Gyllenhal, 1827; the latter also inhabits both the Taymyr Peninsula and the Putorana Highland (see above).Additional material including male specimens is necessary to prove the distribution of the new species up to the Chukot Peninsula.