THE BIRTH OF THE MOSQUITO 29 



back through which it obtains air in a similar manner. 

 After taking a breath of air the larva goes down 

 again to feed. On its head are two swirling circu- 

 latory organs which direct particles of food towards 

 its mouth ; the pupa does not feed. 



The pupa stage lasts, in hot weather, for about 

 twenty-four hours ; but this period may be pro- 

 longed if the water is cold. During this nymph 

 stage, the winged insect is gradually forming within 

 the pupa skin, much as the kernel of a nut becomes 

 loosened within its shell. 



While the pupa is resting near the surface of the 

 water, breathing through the air tubes on its back, 

 the skin splits where the latter meets the surface. 

 Through the split the head, antennae, and the pro- 

 boscis of the mature flying mosquito slowly emerge 

 above the water. The two forelegs are thrust out 

 and rest on the water on each side of the pupa-case, 

 making tiny dimples on the surface of the fluid. 

 These are followed by the next pair of legs, and then 

 the wings are born. For half an hour the partly 

 hatched mosquito remains floating on the old pupa 

 case, from which it is in process of being born. The 

 wings are gently separated and carefully tried, and 

 ultimately the body and last pair of legs are drawn 

 out of the shell, when the new mosquito flies away. 

 If during this process there comes a gust of wind, or 

 the water is disturbed in any way, the mosquito will 

 be drowned. It is a fateful period of its life. 



But if there is not enough food for the three 

 hundred larvae in the water, they will kill each other, 



