AGENTS OF DISEASE 277 



the life-history of both the Anopheline mosquitos 

 and our common Gnats belonging to the sub- 

 family Culicinae ; both pass the larval and pupal 

 stages of their existence in shallow, stagnant 

 pools, water-tubs, and the like, and also have 

 a superficial resemblance in their general 

 appearance during these early stages of their 

 lives. The female Anopheline mosquito deposits 

 her eggs, which vary in number from fifty to one 

 hundred and fifty, upon the;surface of the shallow 

 pools, depositing them singly without any 

 cement-substance, so that they do not appear as 

 raft-like masses, as is the case with the eggs 

 deposited by the Culex mosquito, but float about 

 singly, in star-shaped groups or parallel forma- 

 tion upon the surface of the water. The eggs are 

 boat-shaped, small in size (from about 07 to i *o 

 mm. in length), and when first deposited white in 

 colour, rapidly darkening to a blackish hue. 



From these floating eggs emerge the quaint- 

 looking, wriggling larvae, and start upon their 

 aquatic life, rising to the surface of the pool from 

 time to time to take in a supply of air. There 

 are one or two points by which the Anophelines 

 can readily be distinguished from any other 

 mosquito larvae. For instance, when undis- 

 turbed, the Anopheline larva will lie flat along 

 and just beneath the surface of the water, the 

 curious palmate hairs on the body segments, 

 which are peculiar to Anopheline larvae, indent- 

 ing the surface film of the water. Another 

 distinguishing feature between the Anopheline 

 and the ordinary Culex larva, is that the former 

 has no long syphon-tube on the eighth segment 



