3i8 



THE STUDY OF INSECTS 



Family Drosophilid^ 



The Pomace-flies and their Allies 



There are certain small yellowish flies from | to i of an inch in length 

 which are very common about the refuse of cidermills, decaying fruit, 



and fermenting vats of grape pomace; 

 these are the pomace-flies (Fig. 561). 



The larvae of most species of this fam- 

 ily, so far as is known, live in decaying 

 fruit or in fungi; a few are leaf-miners. 



One of the pomace-flies, Drosbphila 

 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 



Fig. 561. — A pomace-fly. 



as Drosoph ila ampeloph ila; but melano- 

 gaster is the older specific name. 



Family Agromyzid^e 



This family includes small or minute 

 flies, most of which infest living plants. 

 The larva? form galls on the stems or 

 mine in various parts of the plants, 

 but principally in the leaves. A com- 

 mon species, Phytomyza aquilegice, 

 makes serpentine mines in the leaves 

 of wild columbine (Fig. 562). Other 

 species mine in the leaves of oats, 

 wheat, strawberries, asters, goldenrod, 

 and blackberries, while one species, 

 Agromyza maura var simplex, is a 

 pest to asparagus for the larvae mine under the epidermis of the 

 stems. 



Fig. 562 — Mine of Phytomyza aquilegice. 



The following eight families of those flies which have a frontal suture 

 possess well developed alula or calypteres. They are therefore known as 

 the calyptrate flies or muscids. To this group belong some of the most 

 familiar flies, for example, the housefly and the flesh-flies. 



Family Cordylurid.^ 

 The Dung-flies 



The members of this family are often of considerable size. 



Although members of several families of flies frequent excrement, 

 certain species of this family and of the Borboridae are so commonly 

 observed about dung and refuse that they have received the common 

 names of dung-flies. Among these are those of the genus_ Scatophaga; 

 these are rather slender flies, which have the body clothed with yellowish 



