Cheilosia chukotana Barkalov & Mutin, sp. n.

Cheilosia chukotana Barkalov & Mutin sp. n.

(figs 3A, 4A–D)

Type material. HOLOTYPE, ♀, labeled: Russia: Chukotka, lower reaches of river Anadyr, 64,83° N, 175,96° E, 5 m above sea level, 21.0 7.2013, leg. A. Barkalov, coll. SZM.

PARATYPE: Russia: 1♀, same place as holotype, 21.0 7.2013, leg. A. Barkalov, coll. SZM.

Diagnosis. This species (fig. 3A) is similar to Ch. semifasciata Becker and Ch. parafasciata Barkalov, but differs in its characteristic sharply raised central knob, and by the lack of a transverse stripe and indentation in the anterior third of the frons. Cheilosia semifasciata is distributed in Europe, reaching eastwards to the Caucasus. Cheilosia parafasciata is known from the southern part of the Russian Far East (Khabarovsk and Amur Regions).

Description. Female. Body length: 5.2–5.5 mm, wing length 4.9–5.1 mm. Head: Face black sharply protruding forward, shiny in lower part and with dense grey tomentum in upper part, without distinct hairs; central knob sharply raised (fig. 4A), narrow; eye-margins broad, approximately as broad as width of pedicel, covered with dense grey tomentum (along face with narrow shiny stripe), hairs short, erect, light. Cheeks moderately high, covered with dense grey tomentum and white hairs. Frons broad (fig. 4B), slightly swollen, without transverse stripe and indentation, longitudinal stripes fine, in the middle practically invisible, shiny in most part, only near lunula with narrow strip of grey tomentum, hairs short, erect, yellow. Lunula narrow brown; antennal pits distinctly separated. Antennae black (fig. 4C), postpedicel rounded, covered with grey-brown tomentum; arista short, distinctly broadened in basal 1/3, covered with short hairs. Eyes completely covered with dense, comparatively short brown hairs in length equal to half of scapus width. Vertex covered with black or black and yellow hairs; vertical triangle equilateral. Thorax: Humeri black, with grey tomentum and light hairs. Mesonotum with grey tomentum laterally, shiny medially, covered with moderately long, semi-erect yellow hairs, in front of postalar callus with two short black bristles and with one bristle on postalar callus. Scutellum black, shiny, covered with short erect yellow hairs, two black bristles and two longer yellow hairs on hind margin (in the other specimen, bristles on scutellum are absent). Pleurae with dense grey tomentum and rare light hairs, metasternum with rare light hairs. Legs black with brown knees, covered with light hairs; hind femur without long hairs ventrally. Wings: Narrow, transparent, finely brownish, completely covered with microtrichia; inner angle between veins M1 and R4+5 acute, vein M1 strongly curved (fig. 4D); alula narrow, completely covered with microtrichia. Calypters white with yellow rim and white hairs; halters yellow. Abdomen: Oval, broadest in the end of tergum II, black, shiny with fine brownish tomentum, covered with yellow hairs, erect on sides of terga I–II and semi-erect and erect in the rest of abdomen.

Male. Unknown.

Etymology. The species is named after the Chukotka Peninsula.

Distribution. Russia: Chukotka Peninsula.

Taxonomy. The subgeneric classification of the genus Cheilosia is based on male genitalia (Barkalov 2002). Since we have only females, we can place Ch. chukotana sp. n. to the subgenus Pollinocheila only with a certain degree of conditionality. The evidence comes from the following characters inherent in other females of this subgenus: protruding face, characteristic tomentum of face and frons. Within the subgenus, the new species is similar to Ch. semifasciata Becker and Ch. parafasciata Barkalov, differing from them by the diagnostic characters mentioned above.

Because of the variation in the presence of bristles on the mesonotum and scutellum in Cheilosia chukotana sp. n., in the key to Far Eastern Cheilosia (Barkalov in Mutin & Barkalov, 1999) the new species must be inserted twice.

In the case of a specimen without bristles on the scutellar hind margin, the new species runs to Ch. pollinata Barkalov:

75. Bigger: 9.5–12.0 mm; anepisternum shiny without tomentum............................... Ch. urakawensis Shiraki - Smaller: 5.2–9.3 mm; anepisternum with dense grey dusting................................................. 76 76. Legs and antennae black............................................................... Ch. chukotana sp. n. - Tibiae yellow with dark middle 1/3, postpedicel orange with dark antero-apical 1/3............... Ch. pollinata Barkalov

In the case when strong black bristles are present on the scutellar hind margin, the new species runs to Ch. impressa:

114. Legs black, or only knees narrowly yellow............................................................... 115 115. Fore coxae with basal spur............................................................... C h. impressa Loew - Fore coxae without basal spur........................................................... Ch. chukotana sp. n.