363 



sluggish in the larval stage, but Beling mentions that one species in 

 Europe is very active. 



The larvae are frequently attacked and killed by internal nematode 

 parasites. 



HABITS OF IMAGINES 



Some species are predaceous, feeding upon soft-bodied insects, 

 but the greatest number are found upon flowers. Tree-trunks or 

 fence-posts are favorite resting-places of the species of Leptis, where 

 they invariably assume a position with the head downward. Some 

 species of Chrysopila usually frequent the densest portions of wood- 

 lands, and others are found commonly only on marshy ground. 



Several species of SympJwromyia are known to attack man and 

 cattle in this country, inflicting very painful bites. 



The females of the genus Atherix have a peculiar egg-laying 

 habit. The eggs are deposited upon branches or twigs of willow or 

 other trees overhanging streams. After oviposition the female does 

 not fly away, but dies and remains attached to her egg-mass. A second 

 female adds to the already deposited mass both her eggs and her 

 body, and gradually others do likewise, until the combined mass of 

 eggs and flies assumes considerable proportions, often containing 

 several thousand dead flies. The larvae which hatch, drop from the 

 mass into the stream below, where they pass the immature stages. The 

 Indians in Oregon at one time collected the masses of eggs and flies 

 and used them as food. An interesting account of this aboriginal 

 utilization of nature's resources is given by Prof. J. M. Aldrich.* 



Key to Genera t 



LARVAE 



1. Apical abdominal segment ending in 2 long stalk-like processes. 



which are fringed with long soft hairs ; paired pseudopods present 

 on abdominal segments; aquatic species Atherix. 



— Apical abdominal segment ending in 2 fleshy lips or in 4 tapering 



points, the spiracles situated at the base of the upper processes ; 

 paired pseudopods absent ; terrestrial species 2 



2. Apical abdominal segment ending in 2 fleshy lips, an upper and a 



lower, the inner surfaces of which are brown. . . .Symphoromyia. 



— Apical abdominal segments ending in 4 pointed processes, the inner 



surfaces of which are pale 3 



*Ent. News, Vol. 23, 1912, pp. 159-163. 



tl have pupae of Chrysopila only, and can not give a key for the separation of 

 the genera in this stage. For a key to the imagines use should be made of that to 

 Leptinae in Williston 's ' ' Manual ' '. 



