THE FLY AND ITS ALLIES 



69 



because it infests wheat seedlings and so weakens them that 



they produce no grain. Other minute gnats or midges 



are destructive to clover in 



the United States, either by 



binding the leaves together 



and sucking the sap of the 



plant or by destroying the 



young seed. 



The mosquitoes, or Culicidse, 1 



are so well known that it is 



hardly necessary to describe 



them. They can always be F - 



identified by the feathery an- 

 tennae, by the presence of a 



fringe of hairs on the hind margin of the wing, and by the 



fact that the marginal vein runs all around the periphery of 



the wing. The larvae are 

 usually aquatic, but some 

 species which are abun- 

 dant on our Western arid 

 plains must breed in the 

 earth. The eggs of the 

 aquatic species are laid in 

 a boat-shaped mass, which 

 floats on the surface of the 



Cecidomyia, the Hessian- 

 fly. <i, larva; b, pupa. From 

 the ' Standard Natural History." 



B 



FIG. 71. Culex, the mosquito. A, larva; 

 c, its respiratory tube. B, pupa; cl, the 

 respiratory tubes; a, the end of the 



niing appendages, dorsal view. After 

 drawing of E. Burgess. 



water. The larvae escape 



abdomen with the two oar-like swim- from the lower ends of the 



egg-cases, and are known 

 as "wi skiers." The larvse 



o o 



rest vertically near the surface of the water, head downward, 

 with the tail end' of the body at the surface of the water, 

 1 Culex was Pliny's name for the fly. 



