156 COLEOPTERA. 



into the air ; for their eyes are divided in such a way as 

 to make them appear to have one pair on the lower 

 and another pair on the upper side of the head. They 

 breathe air, carrying it with them into the water in a 

 curious way. They take it, as they dive down, in the 

 shape of a bubble on the end of the abdomen, and 

 usually remain at the bottom only a short time. In 

 the Hydrophilidse the air is attached to the hairs on 

 the lower side of the body, and looks like a film of 

 silver. This is a purely mechanical effect and may be 

 successfully imitated by plunging into water a piece 

 of cloth with a long nap. 



Fig. 95 is the larva of a European species of the 

 genus Gyrinus. Each segment of the ab- 

 domen bears a pair of respiratory organs. 

 When ready to pupate, the larva leaves the 

 water and spins a cocoon. Dineutus con- 

 ^^-^^ tains larger species than Gyrinus, and can 

 easily be obtained for class work. In the 

 family of diving-beetles, or Dytiscidae, the 

 larvae have mouth parts quite different from 

 those of most beedes. The mandibles are 

 hollow, and liquids are sucked up through 

 Fig. 95- them. By this remarkable modification a 

 mandibulate insect has rendered its biting-organs suit- 

 able for a diet of liquid food. 



CARABID.^. 



One of the best places for collecting ground-beetles 

 and their larvae is under stones on the banks of rivers. 

 The family is a very large one. Hai-palus caliginosiis^ 



