DIPTERA 319 



hair, and which are often abundant especially about fresh cow-dung. 

 Other members of this family are found in meadows and in moist places ; 

 some feed on other insects which they capture. 



The larvae of some species have been bred from excrement; some live 

 in the stems of plants; and some are said to be parasitic in caterpillars. 



This family is named the Scatophagidae by some writers. 



Family Anthomyid^e 

 The Anthomyids 



The anthomyids are very common flies of which about five hundred 

 species have been described from North America. They are somewhat 

 similar to the housefly in appearance but structurally distinct. 



The larval habits are variable. Most species live in decaying vege- 

 table matter; many live in excrement. A few species are parasitic within 

 living insects and some attack growing plants. Among the latter are 

 certain well-known pests of garden crops. The more important of these 

 are the following. 



The cabbage-root maggot, Hylemyia brassicce. — This insect in its 

 larval state feeds on the roots of cabbage, radish, turnip, and cauli- 

 flower; it also attacks the roots of various weeds belonging to the same 

 family of plants. There are two or more generations of this pest each 

 year. The first generation infests the young plants; the eggs of the sec- 

 ond generation are laid late in June or in July. The maggots are espe- 

 cially injurious to cabbage plants in the seedbed and to early cabbage 

 plants in the field. 



The onion maggot, Hylemyia antlqua. — The larva of this species is 

 often exceedingly destructive to onions, destroying young plants in the 

 spring, and when the plants are older, burrowing into the bulb and 

 causing decay. 



The beet or spinach leaf -miner, Pegomyia hyoscyami. — This leaf- 

 miner infests the leaves of beets, sugar-beets, spinach, orach, mangels, 

 and chard. The mine at first is thread-like but is soon enlarged to form 

 a blotch. Several larvae usually occupy the same leaf and their mines 

 usually coalesce. There are several generations each year, and the winter 

 is passed in the pupal state under fallen leaves in the soil. 



The kelp-flies, Fucellia. — The larvae of these flies live in brown sea- 

 weeds, cast up by waves along ocean beaches. The adults can be found 

 all summer on the masses of these weeds often in immense numbers. 



Family Gasterophilid^; 

 The Bot-flies of Horses 



This family includes the well-known pests the larvae of which infest 

 the alimentary canal of horses and which are commonly known as 

 bots. Three species are now well established in the United States and 

 Canada. In the adult flies the oral opening is small and the proboscis 

 vestigial. 



The common bot-fly or the stomach bot, Gasterophilus intestinalis . — 

 The adult fly closely resembles the honey-bee in form except that the 



