Vockeroth (1969) gave a genus diagnosis for Syrphus.
Small to medium sized, robust species with mesonotum yellowish- or greyish-pollinose laterally and tergites with transverse yellow fasciae or pairs of maculae.
Eye usually bare, rarely sparsely or densely pilose. Front and face of male rarely slightly swollen, in this case the face broad and with indistinct tubercle. Face usually entirely yellow, rarely with a very narrow brown median vitta. Basoflagellomere usually short oval and broadly rounded apically, rarely slightly elongate and subacute. Scutum shining or subshining, aeneous to black, sometimes with faint, dark, narrow median and submedian vittae; sides of scutum and all of pleura usually slightly but distinctly yellowish- or greenish-grey pollinose. Dorsal and venrtal katepisternal pile patches joined posteriorly by narrow band of hairs. Metasternum bare. Lower lobe of squama almost always with many long erect pale pile on at least posteromedian part of upper surface, these hairs few in number or absent only in one species from Patagonia. Metacoxa with tuft of pile at posteromedian apical angle. Abdomen oval, narrow to moderately broad, slightly convex dorsally, weakly margined from about middle of tergum 2 to apex of tergum 5 or 6. Tergum 2 with a pair of yellow maculae, terga 3 and 4 with sharply defined, often somewhat undulate, narrow or broad, entire or divided, bright yellow fasciae which mayor may not extend to lateral margins. Sterna yellow.
MALE TERMINALIA. Surstylus short, broad, curved slightly ventrad, bluntly rounded apically; inner surface with weak marginal flange dorsally and posteriorly except at apex. Sternite 9 with moderate emargination posteroventrally, with long, rather slender, slightly tapering lingula which is either subcylindrical or grooved on dorsal surface and is curved very slightly to strongly ventrad near its apex. Superior lobe long, broad, directed posterodorsad, strongly compressed, with many minute setae laterally; anteroventral angle with a short recurved hook, ventrolaterally and posterolaterally with a very low compressed submarginal flange which ends posterodorsally in a short projecting tooth. Aedeagal base subtriangular in profile, deeper and slightly compressed dorsally, projecting ventrad as a flat, depressed, apically truncate or apically rounded plate which almost always bears a small to moderately large, anteriorly directed, sub lateral or lateral tooth on each side near apex. Distal portion of aedeagus subtriangular or somewhat depressed in section, flattened posterodorsally and subcarinate anteroventrally, the apex only slightly weaker and slightly to strongly flared laterally and ventrally, with many minute pale spicules anteriorly.
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