ORDER DIPTERA. 



99 



the nectar of flowers through a long proboscis, but nothing is yet 

 known of their transformations. 



Family 22, Bombyliidce. — The Bee Flies belong to this family. 

 They are small or middle-sized insects, densely clothed with hairs. 

 They are exceedingly active insects with long tongues, with which 



Fig. 139. — XylopTiagus Ater (Mag-j 



they suck honey from flowers. Their larvce are often parasitic in 

 their earlier stages on other insects. 



They are very useful in North America by keeping down the 

 number of locusts, in the egg capsules of which the larvce feed. 



Two species, Bombyliis major 2SiA B. medius^ are common in this 



Fig. 140 — Ceria Conopsoides (.Mag.) 



country, and may often be seen in gardens and open spaces i:i 

 woods during the spring and summer months. 



Fa??iily 23, Therevidce. — This family is a very numerous one, 

 especially those of the typical genus Thercva. They are slender, 

 middle-sized black insects, and their bodies are generally covered 

 with hair. They are generally found in the neighbourhood of 

 bushes and trees. 



