MOSQUITOES AND FLIES 



thorax, the mouths of which open above the water when 

 the pupa comes in contact with the surface. The pupa, of 

 course, does not feed, but it is almost as active as the larva, 

 for it must avoid its enemies. When disturbed it rapidly 

 swims downward by quick movements of the abdomen, 

 the extremity of which is provided with two large swim- 

 ming flaps. The duration of the pupal stage in midsummer 

 is about two days. 



The adult mosquito issues from the pupal skin through a 

 split in the back of the latter. We now see why the pupa 

 is made lighter than 

 water — it must float 

 at the surface in order 

 to allow the adult to 

 escape into the air. 



The full-fledged 

 mosquito (Fig. 174 A) 

 has the general fea- 

 tures of any other 

 two-winged fly, but 

 it is distinguished 

 from nearly all other 

 flies by the presence 

 of scales on its wings 

 and on parts of its 

 head, body, and ap- 

 pendages. The mouth 

 parts of the adult 

 mosquito are of the 

 piercing and sucking type, and are similar in structure to 

 those of the horsefly, except that the individual pieces are 

 longer and slenderer, and together constitute a beak, 

 or proboscis, extending forward and downward from the 

 head (Fig. 176 A, Prb). The male and the female mos- 

 quitoes are readily distinguishable by the character of the 

 antennae, these organs in the male being large and 

 feathery (Fig. 174 B), while those of the female are 



I 335} 



Fig. 177. A'edes airopalpus, male, a mosquito re- 

 lated to the yellow fever mosquito and similar to 

 it in appearance 



