THE BEETLES: COLEOPTERA 39 



circling about on the surface of still water. They can see 

 both below and above the surface of the water, as the two 

 eyes are divided into four, and the parts separated so that 

 watch can be kept for danger from either direction. The 

 whirligigs are protected by a strong-smelling milky secretion 

 which probably renders them distasteful to fishes. They are 



nor 



FIG. 22. Diving Beetle. Slightly enlarged 



able to dive to escape danger, carrying down with them a 

 small supply of air. 



Beneath the surface of such ponds and pools as the whirli- 

 gig-beetles frequent are to be found different species of diving 

 beetles (Dytis'cm, Fig. 22), which have adaptations similar to 

 those mentioned among the aquatic Hemiptera. Thus in some 

 the spiracles, which in land insects are along the sides of the 



