THE IVINDOJV-FLIES AND THE 



STILETTO-FLIES 



(Families Scenopinidce and Therevidce.) 



The Scenopinid flies, which Comstock called the window- 

 flies for the reason that they are quite commonly seen upon the 

 windows of houses, are small, active, shining black flies of which 

 we have a half-dozen species in North America, the commonest 

 being Scenopinus fenestralis Linn., which is common to both 

 Europe and North America. Its specific name, fenestralis, is due 

 to its window-loving habit. The larvae of these flies resemble 

 those of the following 

 family, and are long and 

 very slender, white in color 

 and with apparently many 

 joints to the body. They 

 are frequently found under 

 carpets and in decaying 

 wood; also in woolen 

 blankets, and Riley has 

 stated that he found one 



^ * Fig. 79. — Scenopinus fenestralis. (After Smith.) 



This, however, was prob- 

 ably accidental. The manager of a storage warehouse noticed 

 many of these slender, white larvae under carpets sent in by his 

 customers for storage. He was worried at their number since he 

 supposed that their presence might indicate the advent of some 

 new kind of carpet moth. He was assured, however, that they 

 were considered as predatory in habit, and that they feed upon 

 clothes moths and other insects found in such places, such as 

 book-lice. Nowhere, however, does there appear to be any record 

 of any definite observations on this point. One observer tells me 

 that he tried to decide this question, but that the insect intended for 



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