WATER SCAVENGER-BEETLES. 



53 



The last genus is regarded by many as constituting the type of a 

 small family distinct from the Parnidse. Most of these imperfectly 

 aquatic insects are clothed with fine silken hairs which seem to have 

 the property of shedding the water, and of enabling the insect to sur- 

 round its body with a globule of air whilst clinging to the stones be- 

 neath the surface; whereas the purely aquatic beetles, the Dytiscidae, 

 the GyrinidiB and the Hydrophilidte, which have the faculty of swim- 

 ming and of rising to the surface of the water whenever they need a 

 fresh supply of air, have no such clothing. Forty-eight IST. A. species 

 are known. A synopsis of the Parnidse of the United States is given 

 by Dr. Geo. H. Horn in the 3d. vol. of the Tran. Am. Ent. Society. 



Family VI. HYDROPHILID.E. 



I Fig. 17.] 



Hydkophilus :— a, Utyh oi H. piceus, Linn.; e, egg-ease ; d, same opened showing arrangement of 

 eggs ; c, pupa— after Blanchard : b, H. triangularis, Say., natural size ; /, antenna ; q, anterior tarsus ot 

 female ; h, same of male, all magnified ; i, side view of the sternal spine— after Kiley. 



This family is named from the genus Hydrophilus, a word of Greek 

 composition meaning a lover of water. They constitute a somewhat ex- 

 tensive series of water-beetles, but less numerous and less eminently 

 aquatic than the Dytiscidie. In swimming they move the hind legs 

 alternately, whilst the Dytiscidne strike with them both together like a 

 frog. Both of these families contain both large and small species, the 

 largest being an inch and a half in length. Many of the larger species 

 of Hydrophilidte have the sternum or breast bone in the form of a keel, 

 and prolonged posteriorly to a sharp point. They are essentially dis- 

 tinguished from the predaceous water-beetles by their short clavate an- 

 tennae and their loug palpi, which are usually longer than the antennae, 

 and are carried projecting forwards whilst swimming. The larvae of 

 Hydrophilus are predaceous. The names of one hundred and twenty- 

 two N. A. species are given in Dr. LeConte's catalogue, inclusive of 

 twenty-one species of the small sub-family of Sphseridiides. 



