108 



MOSQUITOES 



composed of air chambers, and is used to keep the boat- 

 shaped egg with its flat surface uppermost. The English 

 writers have observed that when the eggs have been much 

 rubbed, the delicate membrane splits off and the egg ap- 

 pears with a glistening black surface like patent leather. 

 They have noted also that when the 

 egg, as frequently happens, is drawn 

 by capillary action a little waj^ up from 

 the water on a leaf, the head or blunt 

 end always points downward, so that 

 when the larva emerges it drops into 

 the water, and not up in the air. 

 Grassi says that the eggs of this 

 species lie in groups of from three to 

 twenty, side by side, like a bridge of 

 boats, but Nuttall and Shipley find 

 them in open pools in Great Britain 

 scattered about. According to these 

 observers the eggs hatch on the second or third day after 

 being laid, depending on the temperature, the young issu- 

 ing through a circular si^lit near the blunt end of the egg. 

 They also state that eggs which were dried less than five 

 days did not hatch. Full and detailed accounts of the 

 anatomj" of the larva and pupa are given by the English 

 writers in a paper entitled " The Structure and Biology 

 of Anoiiheles " {A. macnlipennis) in the Journal of Hygiene, 

 vol. i., No. 1, January, 1901 ; this article is beautifully 

 illustrated. 



Fig. 2.1.— Head of Full- 

 grown Larva of 

 Anopheles puncti- 

 pennis ; enlarged. 

 (Author's illustra- 

 tion.) 



