DIPTERA 



861 



pomace-fly. 



on 



The pomace-flies and their alHes constitute the family Drosophil- 

 idae. In this family the costa is microscopically broken twice, once 

 just beyond the humeral cross-vein 

 and again just before the end of vein 

 Ri ; the subcostal vein is vestigial ; the 

 arista are almost invariably plu- 

 mose; the vibrissas are present; the 

 postvertical bristles are convergent ; 

 and the foremost fronto-orbital 

 bristles are proclinate. 



The larvae of most species of this 

 family, so far as is known, live in 

 decaying fruit or in fungi ; a few are 



leaf -miners; and some exotic species have been found feeding 

 other insects, Aleurodes and Clastoptera. 



One of the pomace-flies, Drosophila melanogdster, which is easily 

 bred and which has a short life-cycle, is widely used in laboratories in 

 the study of heredity. This species has been commonly known as 

 Drosophila ampelophila; but melanogaster is the older specific name. 



A monograph of this family was published by Sturtevant ('21). 



The family GEOMYZID^ is a group of small flies of which 

 nearly fifty species have been described from our fauna. In these 

 flies the postvertical bristles are convergent when present ; the clypeus 

 is large, the foremost fronto-orbital bristles are directed backward; 

 and the fringe of the calypteres is not dense. 



The larvae of the few species of which the habits are known live 

 in the stems of plants or mine in leaves. 



The family was monographed by Melander ('13 b). 



Family AGROMYZID^ 



Fig. 1 1 13. — Mine of Phytomyza aquil- 

 egia. 



sites of the cottony-cushion scale. 



This family includes small or 

 minute flies in which the costa is 

 broken only at the end of the 

 subcostal vein; the oral vibrissae 

 are present, the arista of the an- 

 tennae is closely short-pubescent, 

 the post-vertical bristles are di- 

 vergent, and the lower fronto- 

 orbital bristles are convergent. 



The genus Cryptochcetum dif- 

 fers from the typical members of 

 this family in having the costa 

 twice broken and in that the an- 

 tenna lack the arista. One or 

 two species of this genus have 

 been introduced into California 

 from Australia, as they are para- 



