Aquatic Insects 99 



fashions a cell in which it may undergo 

 the transformation with some degree of 

 safety. 



Another beetle, somewhat larger than 

 Dytiscus and of different habit, is one 

 (Hydrophilus piceus), known, sometimes 

 as the " Great Water Beetle " and some- 

 times as the " Silver Water Beetle " ; 

 this latter name has been gained by the 

 beetle's method of carrying its air supply 

 underneath the body where it is dis- 

 played as a beautiful silvery covering. 

 The way in which this air supply is 

 obtained is very remarkable. The apical 

 joints of the antennae act by means of 

 an arrangement of hairs as a sort of 

 scoop which, when thrust above the 

 surface of the water, retain and transfer 

 to the underside of the abdomen a 

 bubble of air. Good architectural powers 

 are possessed by this beetle. The female 

 constructs, with some gum-like material 

 she secretes, a little flask-shaped cocoon 



