374 NORTH A]\IERICAN DIPTERA 



Family Psilidae 



Somatia xanthomelas. 



Flies of medium or small size. 



Front broad, with bristles on the upper part; face perpendicular 

 or receding in profile; oral vibrissa? absent; antennie decumbent, rather 

 short to very long; arista pubescent, rarely long i)lumose. Abdomen 

 slender or moderately slender; genitalia not prominent, the ovipositor 

 usually elongate. Wings moderately large, the auxiliary vein absent 

 or incomplete; apical cell not narrowed apically; second basal and anal 

 cells large. Legs rather elongate; tibiae without preapieal bristles. 



The adults are usually found in moist places or shady woods. The 

 Psilidas are not always easy to recognize but all the known species have 

 a peculiar ridge or weakening across the basal third of the wing extend- 

 ing from the end of the incomplete auxiliary vein. The character is not 

 at all conspicuous but its presence is sufficient to place the insects. 



The larvae live in the roots or galls of plants and one of them is 

 known as the carrot rust fly, often doing considerable damage to this 

 crop. The larvae of Psila are slender, bare, cylindrical and of a pale 

 yellowish color, the posterior spiracles forming small rounded or button- 

 like processes. 



Melander* has published a synopsis of the known species. 



1920, Psyche, xxvii, pp. 91-101. 



