FAMILIES MYDAIDAE AND APIOCERID/E 



The flies of the family Mydaidae, for which there is no other 

 popular name than the "My das-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 Asili- 

 dae, 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 My das 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 My das 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 transfor- 

 mations are not known. 



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