72 



MOSQUITOES 



down. After one of tliem has wriggled up to the surface 

 of the water, its breathing tube extrudes, fresh air runs 

 into its trachea), and the tension of the so-called surface 



film of the water assists it 

 in maintaining its position. 

 After an introductory wrig- 

 gle, which pulls the breath- 

 ing tube below, the insect 

 sinks. The larval Cidex ap- 

 pears to pass through three 

 different stages of growth, 

 reaches maturity, and trans- 

 forms to pupa, in a minimum 

 of about seven days in warm 

 summer weather. 



The pupa differs markedly 

 from the larva in the great 

 swelling of the thoracic seg- 

 ments, as shown in the ac- 

 companying cut. The pupa 

 seems to be all head and 

 thorax, with a slender abdo- 

 men and with two large flaps 

 at the end of the abdomen, 

 which assist it in swimming 

 whenever it feels that it has 

 to swim. In this stage the 

 Fig. 10.— Pupa of Culex pun- insect is lighter than water. 

 gejis; enlarged, with Anal Seiif- -ri • j« i l j.i 



mentbelow, still more enlarged. It remains motionless at the 

 (Author's illustration.) surface and when disturbed 



