58 



UOVSEHOU) INSECTS 



hanging downward at an angle of 40 degrees. At the tip 

 of the eighth abdominal segment is a long tube known as 

 the respiratory tube (Fig. 20, g). It is through this tube 

 that the larva takes in its supply of air. This f aet accounts 

 for its position with the tail end up and the breathing 

 tube just at the surface of the water, so that air may 

 be drawn through it to sustain life. At the same time, 

 two dark brushes of hairs about the mouth can be seen 

 in constant vibration, by which currents of water are set 

 up and food thus brought to the animal. In a jar con- 

 taining many of the wrigglers, some may always be seen 

 wriggling to and from the bottom in search of food. 

 The larval stage lasts from five to ten days. 



Pupa. — At the end of a week or ten days, in hot weather, 

 the larva changes to another form that we call the pupa, 

 one of which is shown in Fig. 22. The pupa? live in the 

 water along with the larvae and can 

 wriggle about as actively as the larvae. 

 In fact, we suspect most people call 

 them wrigglers, supposing them to be 

 the same as the larva?. But by look- 

 ing carefully one can see a consider- 

 able difference between these two 

 forms. The pupa is mostly head and 

 thorax, with but a slender abdomen. 

 The breathing apparatus now consists 

 of two respiratory tubes instead of 

 one, and, moreover, they are situated 

 on the thorax instead of on the end 

 of the abdomen, as in the larva. As 

 a result of the change in position of 

 the breathing tubes, the pupa floats in the water with 



Fig. 22. — Pupa 

 Culex, enlarged 



of 



