64 NORTH AMERICAN DIPTERA. 



hovering motionless in the air for a time and darting away 

 like a flash. They seek sunny places in woodland roads, 

 about blossoms or on rank vegetation. The Anthracinae are 

 a group especially characteristic of arid regions. In general 

 the members of the family are prettily and delicately marked, 

 and their life histories are often very interesting. In the 

 adult state they are flower flies, feeding upon the pollen and 

 honey deep within the blossoms, extracted by aid of their long 

 proboscis. The larvae of species of Aphcebantus and Systcechus, 

 occurring in western America, are found in the egg-pods of 

 the locust, Caloptenus spretus. "The larvae begin to trans- 

 form themselves into the pupa state early in the summer, and 

 the pupa pushes itself half way out of the ground in order to 

 disclose the fly. They continue to issue during the summer 

 months. As a rule but one year is required for full develop- 

 ment. Aphoebantus is first observed as a yellowish white 

 grub, about half an inch long when extended, it being usually 

 curved so that the head and tail nearly meet. It is usually 

 found in a case of locust eggs which it has devoured, pushing 

 the empty shells aside, and at last occupying the space where 

 were twenty-one to thirty-six eggs. Often it is found in a 

 little space below a number of egg-cases, as though it had 

 feasted off the contents of several nests" (Riley). The larvae 

 of Anthrax have been found parasitic upon Megachile, Osmia, 

 Odynerus, Mamestra, Noctua and Agrotis ; those of Argyra- 

 mceba upon Pelopatus, Meyachile, Cemonus, Osmia and Calico- 

 doma ; those of Bombylius upon Andrena and Colletes ; those 

 of Toxophora upon Eumenes ; those of Callostoma in the egg- 

 cases of Caloptenus itaiicce ; those of Systropus upon Lima- 

 codes, etc. 



TABLE OF GENERA. 



1. The bifurcation of the second and third veins takes place opposite or 

 nearly opposite the anterior cross-vein, the distance not exceeding 

 the length of the cross-vein ; the second vein forms a knee at its 

 origin, the third vein in a straight line with the prefurca. . 2 



