72 



MOSQUITOES 



down. After one of them has -wriji^prled up to the surface 

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

 into its trachese, 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 Culex ap- 

 pears to pass through three 

 different stages of growth, 

 reaches maturity, and trans- 

 forms to pupa, in a minimum 

 of about s(>ven 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' cwi. 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 SAvimming 

 whenever it feels that it has 

 to sAvim. In this stag-e the 

 Fio. 10.— Pupa of Cfilfx pun- insect is lighter than water. 



gens; enlarged, with Anal Seg- 



It remains motionless at the 



meiif bcldw, .still more enlarged. 



(Autlior's illustration.) surface and when disturbed 



