26 



WATER-BEETLES— APPLE-SMELLERS. 



small fish and aquatic insects. They have no direct bearing upon 

 horticulture, except, perhaps, by destroying large numbers of the 

 larvae of mosquitoes, which annoy fruit-growers as well as other 

 people. The illustration, (Fig. 25), gives an idea of the form of 

 such beetles and their larv;e. The larvae, though aquatic, leave 

 the water when ready to change to pupae. This is performed in 

 an earthen cell made for this purpose in adjoining dry soil. 



Fig. 25.— Carnivorous Water Beetles. After Brehm. 



FAMILY WHIRLIGW-BEETIJES OK APPLE-SMELLERS. 



(Gyrinidae) . 



This family is mentioned here not because its members smell 

 like apples, the act which gives it its name, nor because they are 

 fond of that fruit, but simply to show how certain organs can be 

 modified for specific purposes. In these beetles we find that the 

 eyes are completely divided by the margin of the head, so that 

 they appear to possess the unusual number of four eyes (Fig. 7) ; 

 they are also remarkable for their long front legs, which are used 

 for grasping their food. The other legs seem to be absent, but 

 this is not so, as they are simply folded up in the smallest pos- 

 sible space when not in actual use. Every one knows these 

 social black and shiny beetles, small in size, which, however, 

 sometimes crowd together in such numbers on the surface of our 



