COLEOPTERA 



99 



Fig. 39. — A diving beetle Hydrop- 

 orous iindulatus. 



3. The water beetles (Fig. 39) : There are several families 

 of these, all similar form, having 

 boat-shaped bodies and flattened 

 oar-like hind legs. These are 

 adaptations for swimming. Note in 

 any of the forms : 



(a) The compactness and rigidity 

 of the body. 



(b) The predacious jaws. 



(c) The naked , slender, reversible 

 antennae. 



(b) The difference between the 

 hind (swimming) feet and the 

 other feet, 

 (e) The difference in some of 



these between male and female in the form of the fore 



feet. The ones with sucking discs underneath the 



front tarsi are the males. 



The most peculiar of water beetles is the group of the 



whirligigs (Gyrinidae) which have the eyes divided, so that 



there seem to be two pairs, one for looking up into the air 



and one for looking down into the water as they gyrate in 



the surface film. These have an unique form of hind feet. 



4. The rove beetles: Mostly small, elongate, actively run- 

 ning beetles, secretive in habits, having a very characteris- 

 tic appearance that is due to the shortness of the wing covers. 

 These cover only the basal segments of the abdomen, and 

 are cut off squarely behind, like a sackcoat. 



