INSECTS 45 



where mosquitoes breed, one finds countless " suits of 

 cast-off clothing " which would fit all stages of the young 

 wrigglers. 



The mosquito larva has a well-developed head, a thorax, 

 and a jointed or segmented abdomen, but legs and wings 

 are wanting. The most striking characteristic of this stage 

 of the mosquito is the breathing tube that projects diag- 

 onally from the hind end of the abdomen. For while the 

 mosquito larva lives in the water, it is obliged to swim to the 

 surface at short intervals to get its necessary supply of air. 

 It then hangs diagonally with the tip of its breathing tube pro- 

 jecting through the surface film into the air above (Fig. 31). 

 This habit frequently proves its undoing, as we shall see 

 when we come to discuss the methods of mosquito extermi- 

 nation. 



After attaining its full growth as a larva, the insect enters 

 the third or pupa stage (Fig. 31). " The pupa," says Miss 

 Mitchell in her " Mosquito Life," " is the form intermediate 

 between the larva and the adult. Unlike most pupae, those 

 of the mosquito are very active, but like other pupae, they 

 do not eat. They are about the shape of fat commas, 

 floating quietly at the surface or bobbing crazily downward 

 at the least alarm to hide at the bottom, propelled by back- 

 ward flips of the abdomen. . . . The creature no longer 

 breathes through a single tube on the eighth segment of the 

 abdomen but by means of a pair of tubes on the back of 

 the thorax." During this stage the insect develops its 

 sucking mouth parts, its long, slender legs, and its two deli- 

 cate wings, and all these organs may be seen through the 

 transparent outer coat, which is composed of a substance 

 known as chitin. 



At the final molt the mosquito leaves its pupal case in the 

 water and flies into the air, an adult mosquito. If it hatches 



