The single species of Notosyrphus is almost certainly related to Dasysyrphus but differs from that genus in the parallel-sided face, in the more extensive katepisternal pilosity, in the reduction of wing microtrichia, in the much larger non-lunulate abdominal markings and in many features of the genitalia. Among the latter are the elongate and slender surstylus, superior lobe and lingula, and the very different configuration of the aedeagus. The skatepisternal pilosity of Notosyrphus is very similar to that of Scaeva. The reduction of the wing microtrichia also suggests a relationship with Scaeva, although it has not extended nearly as far as in that genus. The enlarged dorsal eye facets of the males of Scaeva also serve to distinguish the two genera, as do many differences in the genitalia (from Vockeroth 1969).