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Families Mydaidae and Apioceridae

The flies of the family Mydaidae, for which there is no other popular name than the "Mydas-flies," are large and rather slender forms, frequently black with yellow or red bands and with smoky wings. They much resemble the robber-flies of the family Asilidae, to which they are rather closely related. They are quite abundant in this country, though rare elsewhere in the world. The flies are predatory like the robber-flies and feed upon other insects. The early stages are known in only a few species. The larva of Mydas fulvipes Walsh lives in decaying sycamore trees and is probably predatory on other insects living in such locations. This larva is nearly two inches long. Other species are said to be predaceous in the larval stage and on the larvae of the gigantic long-horned beetles of the genus Prionus, which are generally found in dying or dead trees and usually in the roots. The remarkable species known as Mydas luteipennis Loew, which occurs in Texas and New Mexico, has dark orange-yellow wings of the same shade as those of the so-called tarantula-killer (a very large wasp known as Pepsis formosa). This is obviously a case of aggressive or protective mimicry, and the same phenomenon is seen with some of the slender black and yellow-banded flies of this family, which look like Scoliid wasps.

The flies of the family Apioceridae also look something like the robber flies, but our species are all western. They are rather large and slender; some rest on the ground and others hover over flowers like humming-birds. The early stages and transformations are not known.