Hypselosyrphus is based on an Ubristes species in which the 4th abdominal segment is short and triangular. As with Stipomorpha, this character is considered only of species group value.
Ubristes (Hypselosyrphus) species have postmetacoxal bridge complete; abdomen triangular, broad basally, strongly narrowed apically, short, almost equilateral in shape; metatibia with long pile along dorsal edge, forming a distinct brush of pile; basoflagellomere not furcate, usually not greatly elongate; metabasitarsomere not enlarged; and vein R4+5 with an appendix extending posteriorly into cell R4+5.
Adapted from original description (Curran 1940).
A small, shining black species with triangular abdomen; pile black except for the head and yellow maculae on the thorax.
MALE.
Head black, the facial orbits yellowish; pile pale yellowish on the face and lower half of the occiput, black above. Front narrowest at the anterior fifth, widening to the vertex and below, the ocellar triangle small, longer than wide, situated at the middle of the upper section of the front. Occiput with pale pollen on the lower half. Gena linear, not visible in profile. Face very gently convex, almost flat for much of its length, strongly narrowed below. Antennae about as long as the face; the basoflagellomere about twice as long as scape, its apex rather sharply rounded above; pedicel about half as long as scape.
Thorax shining black, the pleura somewhat castaneous; pile erect, black; small maculae of yellow pile at the inner ends of the suture and in front of the sides of the scutellum, the scutellum usually with some yellow pile laterally on the free border, short and only gently convex apically; pleura with long, sparse yellow hairs across the middle. Legs black and with black pile, posterior surfaces of the anterior four tibiae and the basal half of the upper surface of the metatibiae with white pile. Pile short, long on the dorsal surface of the metatibiae. Wings strongly tinged with brown; vein M1 transverse or very slightly recurrent, the bend broadly rounded and with a short appendix in front. Calypter grayish, with brown border and fringe. Halteres brownish.
Abdomen broad, the fused third and fourth segments almost as long as the basal two combined and tapering from base to the sharply rounded apex. Pile black except for a triangle of white pile on the posterior corners of the second segment. Genitalia small. Venter black or brown and practically without hair.
Synonym:
Microdon triangularis Curran, 1940: 6.
Ubristes (Hypselosyrphus) triangularis (Curran, 1940).
Curran, C.H. (1940) Some new Neotropical Syrphidae (Diptera). American Museum Novitates 1086, 14 pp. [1940.10.16]
unless otherwise stated