70 NATURE STUDY 



run and leap as the water- striders do, or swim ? Unlike the 

 water-striders also, they occasionally dive and swim beneath the 

 surface. How do they breathe ? Note the little silvery bubble 

 almost always visible at the posterior tip of the body when the 

 beetle is swimming underneath the surface. Examine one of the 

 insects closely, using a magnifier. Note that it has four eyes, 

 one pair on the lower surface ol the head, just underneath the 

 pair on the upper surface. Note also the peculiar shape of the legs, 

 the front pair being rather slender and oar-like, while the hinder 

 two pairs are short, broad and paddle-like; all are, however, 

 adapted for swimming. 



In addition to the water-striders and whirligig beetles, numer- 

 ous other smaller insects may be found on the surface of pools 

 and ponds. Many small two- winged flies run about on the sur- 

 face in search of food, and certain small sucking bugs may often 

 be found running about on the wet shores of the pond or upon 

 the water near the edge. 



WATER-BUGS AND WATER-BEETLES. In the pools on the 

 surface of which the water-striders and whirligig beetles are 

 found, may be found certain insects which swim vigorously about 

 in the water, coming occasionally to the surface and resting there 

 a 'short time. These are the water-bugs 

 and water-beetles. The water-beetles (fig. 

 43) are large, shining black, elliptical in- 

 sects from half an inch to an inch and 

 a half long; the water-bugs (figs. 44 and 

 45) are smaller, being less than half an inch 

 long, and they are gray in general color 

 instead of black. Each of these water- 

 bugs and water-beetles has three pairs of 

 legs, of which one pair is usually especially 

 long and flattened, so as to be oar-like. 



Fig. 43. "Water-scavenger ,_., . . 



beetle (Hydrophtius). They have wings, which are kept closely 



