SPOROZOA 1119 



and oval, supported on the surface of the water by ornamental air 

 cells; those of culex are cemented together when laid in raft-like 

 masses. 



The larva are aquatic and die quickly out of water. They are 

 both bottom and top feeders, eat voraciously, consuming alga? and 

 other vegetable matter, and some varieties are cannibalistic. The 

 larvae are provided with a breathing tube or respiratory siphon pro- 

 jecting upward from the dorsal surface at the caudal end, and in 

 breathing this is thrust upward to the surface of the water and the 

 larva hangs suspended from the surface film. In the anophelines the 

 breathing tube is short and its angle with the body is such that the 

 larva lies parallel with the surface; with culex and other genera the 

 body lies at an angle with the surface. The larval stage lasts about 

 six to fourteen days, depending upon the temperature and food sup- 

 ply, and is followed by the pupal stage, during which no feeding 

 occurs; the pupa, however, needs air and is provided with a short 

 respiratory tube at each side of the head. The habit of coming to 

 the surface of the water to obtain air, which obtains in all mosquitoes 

 except the Mansonia, gives a point of attack in combating them, since 

 a layer of mineral oil on the surface of the water occludes the respira- 

 tory siphon and so kills them. 



The adult, or imago, emerges from the pupa when the latter is one 

 to three days old; the pupal case ruptures along its dorsum and the 

 emerging imago rests on the floating pupal case until its wings are 

 dry. Since this is a critical stage in its life history and demands 

 quiet water, it is evident that the least wave action is fatal to the 

 mosquito. 



The nature of the breeding place is characteristic, to a certain 

 extent, of each genus of culicidce; stegomyia (cedes calopus), the car- 

 rier of yellow fever, for example, is strictly domestic and breeds in 

 water jars, tin cans, old beer bottles and other artificial collections 

 of water, ivyeomyia breeds exclusively in the fluid at the base of the 

 leaves of air plants (bromeliads) the anophelines, while domestic to 

 the extent that they live near human habitations, require natural 

 collections of water for breeding places, such as sheltered spots along 

 the overgrown banks of streams, temporary puddles and even in 

 water in the footprints of man and animals. 



A proper classification of mosquitoes requires considerable train- 

 ing, but the following points will suffice to separate the anophelines 

 from other mosquitoes. On either side of the proboscis, as seen 



