The Bee-Flies 



Typical Life History of a Bee-Fly 



( Systoechus oreas 0. S.) 



This species is a Western form and is parasitic in the egg- 

 cases of the so-called Rocky Mountain Locust or Western Grass- 

 hopper. It is unfortunate that the life history of no good repre- 

 sentative of the Eastern species in some one of the other genera 

 which may be supposed to live in the nests of wild bees has been 



worked out. Here is 

 a field for some intel- 

 ligent Eastern worker. 

 The eggs of the pres- 



jy I M$b f s^' ent s P ec * es nave not 



// ^l- --tJ? St been observed but the 



larvae are found in the 

 egg-pods of the grass- 

 hopper or near them 

 and of different sizes 

 during most of the 

 year. The larvae be- 

 gin to transform to 

 the pupa state early 

 in the summer and the pupa pushes itself half-way out of the 

 ground in order to disclose the fly. Flies continue to issue dur- 

 ing the summer. Normally there is but one generation annually 

 but there is a great tendency to retardation and sometimes the 

 larvae remain over unchanged until the second year. The larva 

 is a stout, plump, curved, grub-like 

 looking creature with an opaque 

 whitish color with small dark-brown 

 head. The pupa looks something like 

 the pupa of a Lepidopterous insect 

 but bears many spines on the head 

 and thorax and the dorsal ridges of 

 the abdominal segments also bear rows of spines while other 

 portions of the body carry soft dark hairs. 



Fig. 77. — Systoechus oreas. (After Riley.) 



Fig. 78. — S. oreas, pupa. 

 (After Riley.) 



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