152 



BRANCH ARTHROPODA 



The carnivorous water beetles (Dytic'idce), of which there are three 

 hundred species, are found everywhere in streams and ponds (Fig. 123). 

 They vary in length from to 1$ inches. The diving beetle projects the tip 



Fig. 122. Ground beetle (Calosoma), similar to C. scrutator; below, a 

 Carabus. (Brehm.) 



of its abdomen through the surface film to breathe. It raises the elytra a 

 little, and the air which is caught under them is held by the fine hairs on the 



Fig. 123. Carnivorous water beetles. (Brehm.) 



back, where the spiracles are situated. Thus, it carries a supply of air 

 which enables it to breathe under water. These beetles make interesting 

 aquarium specimens. 



