Dasysyrphus osburni (Curran, 1925):177

Dasysyrphus osburni (Curran, 1925).

Curran, C.H. (1925) Contribution to a monograph of the American Syrphidae north of Mexico. Kansas University Science Bulletin (1924) 15, 7-216, 12 pls. [1925.12.01]

Eyes pilose. Face with a broad median black stripe; scutellum yellow pilose; abdomen with three pairs of reddish yellow spots, the last two arcuate, all reaching the side margins in their full width.

Adapted from original description (Curran 1925).

MALE.

Head: Face translucent yellowish, with a bluish opalescence; gena before suture, oral border narrowly and a broad facial vitta, not quite reaching the antennae, shining black; lateral side of face (jowls) metallic bluish, lightly dusted with greyish pollen. Face, in profile, with a small swelling just below the antennae, thence almost perpendicular, deeply and sharply excavated between the tubercle and anterior oral margin; pile sparse, fine, whitish. Frontal triangle metallic bluish, lightly dusted with greyish pollen; pile black more cinereous above. Vertical triangle long, metallic bluish, with black pile, which becomes whitish posteriorly. Occiput black, along the orbits densely greyish pollinose, with whitish pile; cheeks with whitish pile. Antennae yellowish, basoflagellomere brownish above, oblong oval; arista luteous.

Thorax metallic blackish green, with pallidly yellow pile. Scutellum translucent yellowish brown, with strong metallic blue reflection; base and sides metallic blue; pile all long, pale, yellowish. Legs reddish yellow, the basal half of the anterior four and four-fifths of the metafemora, blackish; metatarsi fuscous apically. Wings hyaline; stigma luteous. Squamae almost white, with pale yellow border and fringe. Halteres pale yellow.

Abdomen shining brownish black, the second segment largely subopaque; with three pairs of yellow maculae. First pair of maculae situated about the middle of the second segment, elongate oval, broadly separated from each other, and moderately so from the lateral margins, but there is an obscure streak stretching forward laterally toward the margin; the maculae transverse. Second and third pairs of maculae arcuate, moderately separated from each other, concave in front, slightly convex behind, their inner ends somewhat clubbed and nearer the anterior margin than the outer end; posteriorly they are somewhat narrowed laterally by a black triangle. Apices of the fourth and fifth segments yellow; fifth with the narrow lateral margin and a small triangular macula on each anterior angle, reddish. Pile long, yellow, shorter on the disc; black on the black portions beyond the middle of the second segment. Venter yellow; first segment, except apically, and moderately broad fasciae on each of the following segments, shining black; the first fascia emits a narrow median vitta to the front margin of the second segment; pile yellow.

Superficially this species resembles Dasysyrphus pauxilus, but may be distinguished at once by the broader spots which reach the side margins,.

Body length: 8 mm.

Nearctic species found from Alaska to Labrador, South to Massachusetts.