HOW INSECTS BREATHE 139 



face, catch and devour its prey, breathing com- 

 fortably the while. (See page 117.) 



The whirligig beetles, although they spend 

 most of the winter buried in the mud at the bot- 

 tom of their home stream, are most frequently seen 

 spinning about on the surface of gently flowing 

 water. When disturbed by the quick stroke of 

 an oar or the splash of a collecting net, they dart 

 to the bottom as by one accord. Each carries 

 down a bubble of air attached to the tail end of 

 the body. They have no cunningly devised tra- 

 cheal gills and would very soon drown without 

 their silvery globule of air. 



Dragon-fly nymphs are able to breathe while 

 under water, by means of complicated internal 

 tracheal gills. They can also breathe air at the 

 surface through true spiracles. Some insects are 

 known to tap the air-chambers of submerged plants 

 and to utilize the air thus obtained. 



Let us all turn to and study the ways of water 

 folk. Each has its own method of solving its own 

 problems. They do very much as their ancestors 

 did. If they make any improvements from gen- 

 eration to generation we do not notice them. They 

 are a conservative people, and never go in for 

 new-fangled ventilators, patent air-shafts or even 

 automatic air-pumps. 



