96 



^A' ACCOUNT OF BRITISH FLIES. 



the alimentary canal being plainly seen through the integuments. 

 On the ventral surface organs of locomotion seem to be represented 

 by slight swellings armed with bristles. 



A. 



B. 



Y\Q. 14. A. \.?ci\2^ oi Sciophila ; B. Larva of Ceroplatits ; c. oiSciara. 



The habits of the larvae are interesting. They are all gregarious. 

 They all, with the exception of Sciara, seem to live in fungi. Sciara 

 prefers vegetable mould and under the bark of trees for its home. 

 The larvK, according to various observations, appear to moult several 

 times before they pupate. The Sciophila larvae do not live inside 

 fungi but seem to prefer to crawl about on the outer surface, on the 

 under side of the pileus, which they cover with threads. This web- 

 formation is a very common feature in the larvae of this family ; a 

 coarse webbing is formed over the surface or under side of the pileus, 

 and in and under this the larvae live. The larvae forms a slimy 

 tract where it crawls along. Perhaps the most interesting are those 

 of Sciara, known as the "Army Worm."* They differ from other 

 Mycetid larvs by the absence of any bristles on the ventral surface, 

 by the structure of their trophi and by their habits, nearly all living 

 in large numbers under the bark of trees and in mould. At certain 

 times these larvae seem to migrate, for what purpose we do not know. 

 They form columns twelve to fourteen feet in length, two or three 

 inches broad and half an inch thick, containing countless numbers 

 as close together as they can be packed. These processions are often 

 seen in woods on the Continent, but what they are for or what they 

 mean we cannot tell ; as the larvae are always full grown it cannot be 

 for feeding purposes. It is this habit that has given them the name 

 of " Army Worms." Some larvae of this family are noted for a 



* Heer-ivunn is a better term, as so many larva: which are gregarious are called 

 " Army Worms." 



