MANUAL OF NATURAL HISTORY. 179 



not dilated in the males. Living in marshy 

 situations. 



II. SUB-ORDER. PREDACEOUS WATER-BEETLES 

 (Hydradephaga). 



Legs short, formed for swimming hinder pair re- 

 mote from the others and horizontal; hind-tibiae and 

 tarsi generally compressed and fringed with hair ; 

 body ovate ; antennae setaceous ; eyes not prominent. 

 Aquatic. 



8. FAMILY. Diving-Beetles (Dyticidae). Antennae 



long, setaceous ; legs unequal, hind pair long- 

 est, deeply fringed ; tarsi broad, flat, fringed, 

 ending in a point ; males with the fore tarsi 

 dilated, females often with elytra sulcate. 

 Swim and dive with agility, inhabit ponds, 

 often fly by night. 



9. FAMILY. Whirlwigs (Gyrinidae). Antennae short, 



clavate, rigid, second joint with a lobate ap- 

 pendage ; eyes divided ; thorax transverse, 

 waved before and behind ; legs unequal, the 

 two front very long, ambulatory; the four 

 hind very short, compressed, formed for swim- 

 ming ; with a metallic lustre. Usually swim 

 on the surface of the water. 



II. LEGION". RYPOPHAGOUS-BEETLES (Rypophaga). 



Mouth with four palpi, the inner maxillary repre- 

 sented by outer lobe of maxillae, which is dilated or 

 jointed but not palpiform ; antennae gradually or 

 abruptly clavate ; males with basal joints of tarsi 



