AQUATIC BEETLES 



n 



ment of its abdominal segments, drawing in pure air 

 and breathing out the air vitiated by the oxidation of 

 the tissues. After a few minutes, more or less accord- 



FiG. i8. — Hydrophilus piceus, male. Antenna (enlarged), and side view of head 



with antenna in place. 



ing to the activity of the Insect, the imprisoned air 

 within and without the body has become sensibly 

 impure, and then a fresh supply must be obtained 



