140 



ELEMENTARY ENTOMOLOGY 



The predacious diving-beetles (Dytisci- 

 dae) are to be found in any pond, where 

 they may be seen suspended at the sur- 

 face of the water with the tip of the abdo- 

 men thrust up so that air may be drawn 

 in under the elytra, or diving here and 

 there after their prey, which consists of 

 any insects that they can overpower, small 

 aquatic animals, and occasionally small 

 fish. The largest species are about an 

 inch long, while the commoner ones are 

 one half or three fourths as large and are 

 brownish-black, often marked with dull 

 yellow. The hind legs are long, flattened, 

 and fringed with hairs, 

 forming admirable swim- 

 ming organs. The larvae are elongate, spindle- 

 shaped grubs, with strong, ferocious-looking jaws, 

 with which they grasp and suck out the juices of 

 their prey, which has given them the name of 

 water- tigers. 



Whirligig-beetles. Every pool is the home of 

 a school of the well-known whirligig-beetles (Gyri- 

 nidae), which chase each other over the surface, 

 where they feed on small insects which fall into 

 the water. They are usually much smaller than the last-named 

 family, are oval in shape, much flattened, of a jet-black color, and 



FIG. 194. A ground-beetle 



(Calosoma calidiim}. (Natural 



size) 



FIG. 195. Lebia 

 grandis, an im- 

 portant enemy of 

 the potato-beetle 

 (Enlarged) 



FIG. 196. A common ground-beetle (Harpalus caliginostis'}. (Enlarged) 

 A, its larva ; J3, head of larva, showing mouth-parts. (After Riley) 



