Cheilosia caerulescens caerulescens (Meigen)

Stahls, Gunilla & Barkalov, Anatolij V., 2017, Taxonomic review of the Palaearctic species of the Cheilosiacaerulescens-group (Diptera, Syrphidae), ZooKeys 662, pp. 137-171 : 141-145

Cheilosia caerulescens caerulescens (Meigen) Figs 3, 4

Syrphus caerulescens Meigen, 1822: 295.

Chilosia coerulescens : Becker 1894: 375, Sack 1932: 65; Šuster 1959: 74; Séguy 1961: 36.

Cheilosia caerulescens : van der Goot 1981: 159; Marcos García 1985: 517; Čepelák 1986: 52; Šimić 1987: 38; Brădescu 1991: 39; Stuke 2000: 22; Reemer et al. 2009: 147; Ball et al. 2011: 44.

Nigrocheilosia caerulescens : Vujić 1996:53.

Type locality.

Österreich [Austria].

Type material studied.

Lectotype, ♂, in MNHN. The original description is for both sexes. Becker (1902: 354) mentions only one male specimen which agrees with the original description and he designates it 'Die Type’. The lectotype bears the following labels: ‘Meigen’ [handwritten in ink, round greyish collection label]; ' caerulescens ' [ Meigen’s handwriting].

Description.

Male: Fig. 4A. Face in anterior view slightly divergent from level of antennal insertion to lower mouth edge, with lower part protruding, with pollinosity laterally and below antenna (Fig. 3A). Facial knob moderate in size, shining. Parafacia rather narrow, in width slightly more than 1/2 the width of basoflagellomere, shining in lower part and with pollinosity on upper part narrowly along the eye. Frons slightly swollen, shining, with white and posteriorly some black pile, yellow pile anteriorly along eye inclined. Frontal angle about 90°. Lunula dark brown. Antennal pits confluent. Vertical triangle with black pile. Eye-contiguity about equal or slightly shorter than the length of frons without lunula. Scape and pedicel dark-brown, basoflagellomere small, dark brown to yellowish brown. Arista rather long, with short pile (Fig. 3C). Scutum shining (with bluish tinge), rather coarsely punctated, with whitish to yellowish erect, rather long pile of about even length, intermixed with black pile of same length or slightly longer. Scutellum with yellowish erect pile of same length as on scutum, margin with some longer black or yellow bristles. Postalar callus with 3-5 black bristles. Anepisternum and katepisternum shining, with very slight pollinosity, and with white long pile. Katepisternum with dorsal and ventral hair patches connected. Wing completely microtrichose, hyaline, crossveins darkened. R4 + 5 of wing not distinctly curved, angle of R4 + 5 and M1 about 90°. Halter yellow. Legs with distal part of femora and tibiae, and basal 1/3-1/2 of tibiae yellowish, tarsi dorsally dark-brown. Mesofemur posteriorly with white pile, metafemur anteroventrally and dorsally with long white pile, and ventrally with shorter (stronger) black pile. Abdomen slightly oval, shining (bluish tinge), with coarse punctation, with long erect yellow pile on tergite I, tergites II–IV with erect yellow pile laterally (longest on tergite II), and somewhat shorter erect yellow and black pile intermixed medially. Yellow pilosity on postero-lateral corners tergites II–IV inclined. Sternite I with pollinosity, sternites II–IV shining, all with long yellowish pile. Hypopygium as in Fig. 3 E–G.

Female: Fig. 4D. Face as in the male. Eye-margin width about 1/2 the width of basoflagellomere. Frons coarsely punctuated, with whitish erect pile anteriorly, and with black erect pile on posterior part (Fig. 3B). Whitish pile on anterior part of frons inclined along eye. Vertical triangle with black and white pile. Basoflagellomere rounded, reddish brown to dark-brown (Fig. 3D). Scutum shining, with white pile of even length, with few scattered black pile of about the same length or slightly longer intermixed. Postalar callus with 0-3 black or yellow bristles. Scutellum margin with 2-4 black or yellow bristly-like pile. Metafemur with only yellow pile. Tibiae in basal 1/3 yellow, apically narrowly and obscurely yellow, with broad dark ring, tarsi dorsally brown or yellow, with brown segments 4-5 of protarsi, segment 5 of mesotarsi and segments 3-5 of metatarsi. Abdomen oval. All sternites shining. Otherwise as the male.

Size. Body length 6.5-12 mm.

Additional material studied.

Switzerland 2 ♂, 2 ♀ Zermatt, 1 600-1 700 m, 30.VII.1964 (v.d. Goot; Lucas) [RMNH]; 1 ♂ Zermatt, 30.7.1930 [MNB]; Italy 1 ♂, 1 ♀ Italia, Südtirol, W Tubre di Avigna 1 300-1 800 m 6.VII.1988 (Claussen) [ISEA], 1 ♂ Stilfserjoch [MNB], 2 ♂ Italia, Alpen, Vinschgau Martelltal, Lyfi-Alm, 2 000-2 500 m, 1.7.1995 (Doczkal) [coll. Doczkal], 1 ♂ Italy, Stelvio Park, Trafoi, 1 900-2 000 m, 20.6.1993 ( Ståhls) [MZH]; France 1 ♂ 'Le Lautaret, 4.VIII.26' [MNHN], 1 ♀ 'Le Lautaret, 2.VIII.26' [MNHN], 1 ♂ 'Le Lautaret, 12.VI.1919' [MNHN]; Austria 'Wien, Egger’ [MNB]. See also Table 2 for data molecular specimen vouchers also used for morphological study.

Distribution.

Austria, Belgium, Czech Republic, France, Germany, Great Britain, Italy, Netherlands, Montenegro, Poland, Romania, Spain, Slovakia, Switzerland.

Remarks.

Color of pile on scutum varies from almost yellow with some black pile to yellow with broad stripe of black pile between wing bases (Fig. 4 B–C). Color of tarsi varies from dark to mainly yellow (especially in female). Some studied females do not have yellow bristles or bristle-like pile on scutellum hind margin. The color of basoflagellomere varies from dark brown to yellowish brown. We treat the taxon as subspecies until evidence to the contrary is presented.