THE WINDOW FLIES 259 



inch long. It has a humpbacked appearance, and the 

 abdomen is flattened. Osten Sacken (1886) has given 

 a good review of the European literature on the habits 

 of this fly, and has shown that it has been reared from 

 decaying tree fungi, from horse hair in a mattress, 

 from a swallow's nest, from the cocoon of a large moth, 

 from carpets, from a branch of a tree, from pine boards, 

 from the pupa of a large moth, and from a root of 

 aconite. 



The different European authors making these obser- 

 vations from time to time have thought variously that 

 the window fly was carnivorous or vegetarian, in ac- 

 cordance with the substances from which they reared 

 it. Osten Sacken, however, concludes rather positively 

 that it is carnivorous, that the larva does not frequent 

 fungi, rotten wood, swallows' nests, etc., for the sake 

 of vegetable material or animal remains, but for the 

 sake of the pupae and perhaps also of the larvae which 

 it finds there. He deduces from this that when it oc- 

 curs in carpets and horse hair, it is not because it feeds 

 on them, but because it hunts there for the larvae and 

 pupae of the moths or other insects that live in them. 



Similarly in this country divers observations have 

 been made, and the records of the Bureau of Entomol- 

 ogy at Washington show that it has been reared from 

 strawberry plants, from the egg-pods of grasshoppers, 

 from the hair of a Navajo blanket, from a sack of rye 

 infested with the grain beetle, from under carpets, 

 among stored oats and stored corn, from a basket con- 

 taining small rolls of cotton and woolen goods, and 



