185 



Family Therevidae— The Stilleto Flies 



Thereva species. 



Flies of moderate size, more or less bristly and often pilose, witli 

 predaceous habits. 



Front not excavated, the eyes of the males usually holoptic or 

 nearly so; proboscis projecting, the labellas broad; palpi two-seg- 

 mented; ocelli present. Antenna? with three segments and usually a 

 sharp terminal style. Abdomen elongate, the genitalia small but ex- 

 posed, the ovipositor with a circlet of spines. Legs with bristles; 

 empodia absent; pulvilli usually present. Third vein furcate; five 

 posterior cells, the fourth sometimes closed; anal cell closed toward 

 the margin of the wing or narrowly open. 



The adults are found in various places but are most al)undant in 

 dry areas, such as meadows, pastures and along sandy beaches. They 

 often occur in considerable numbers in burnt-over areas and arc always 

 most abundant during hot weather. Cole* has revised the family and 

 given keys to the North American species. A number of species have 

 been described during recent years but most of the species will be found 

 in Cole's paper. 



The larvae are not well known but are all believed to be predaceous 

 and they may prove to be of considerable importance in the control 

 of certain insects. 



1923. Proc. U. S. N. M., Ixii, Art. 4. pp. 1-140. 



