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Chapter XIX 



ANOPHELINAE— THE LARVA AND NYMPH 



The Larva 



The larva of Anopheltnes when first hatched out 

 are minute characteristic creatures, with very black 

 heads and transparent bodies. They move with a 

 very active wriggling movement. They can, even 

 at this stage, be distinguished from the larvae of 

 Culex, especially with the aid of a lens, as they take 

 up a horizontal position. At first the heads of all 

 species are dark and very conspicuous. After a 

 certain number of days, however, the head becomes 

 lighter in colour, and characteristic markings can 

 be made out on the dorsum. When first hatched 

 the head is very large in proportion to the thorax, 

 later, it is smaller, and finally, it is the thorax 

 which is the larger. 



During the first few days the palmate hairs 

 are siriiple lanceolate structures, and cannot be 

 used as specific characters. 



Duration of Larval Stage. — -This is determined by at least 

 two factors, (i) Food. — Thus larvae kept in tap- water in the 

 laboratory grow very slowly, if at all ; (2) temperature. — Thus 

 the larval stage oiA. maculipennis varies from sixteen to twenty- 

 two days at air temperatures of 68°-78° F., while in the tropics 

 the time is much shorter, e.g., twelve days for Ce. Argyrotarsis 

 in Havana, and eleven days for M . rossii, where the tempera- 

 ture of the water varied from 96°- 102° F. 



