DIPTERA. 



443 



vn. 



nn+j+3 



nr 4+$ 



Vila 



m, + »+3 



The larvae are gregarious, and live in fungi and in decay- 

 ing vegetable matter. They may be found in the fungi 

 growing on logs and 

 trees, in the vegeta- 

 ble mould among 

 dead leaves, under 

 bark, and sometimes 

 in cow-dung. They 

 have eight pairs of 

 spiracles. One spe- 

 cies, Sciara mall 

 (Sci'a-ra ma'li), feeds 

 on ripe apples, es- 

 pecially those that 

 have been previously 

 perforated by the 

 Codlin-moth. 



In this family the 

 larva has a distinct 

 head. The pupa is 

 not enclosed in the 

 skin of the larva ; 

 but in some genera 

 the transformations 

 are undergone in a delicate cocoon. 



The larvae of some species of the genus Sciara often 

 attract attention on account of a strange habit they have of 

 sticking together in dense patches. Such assemblages of 

 larvae are frequently found under the bark of trees. But 

 what is more remarkable is the fact that when the larvae are 

 about to change to pupae an assemblage of this kind will 

 march over the surface of the ground, presenting the appear- 

 ance of a serpent-like animal. Such a congregation is com- 

 monly spoken of as a Sciara-army-worm. Examples have 

 been described that were four or five inches wide and ten or 

 twelve feet long, and in which the larvae were piled up from 



Vila 



FlG. 520.— Wings of fungus-gnats. (The drawings are 

 after Winnertz ; the lettering is original.) 



