WATEE SCAVENGER-BEETLES. 



53 



The last genus is regarded by iiuiiiy as constituting the typo of a 

 small family distinct from the Parnida;. Most of these imperfectly 

 aqnatic insects are clothed with fine silken hairs wliich 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 tlie purely aquatic beetles, the Dytiscida', 

 the Gyrinida> and the nydroi)hilida', 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 (Nothing. Forty-eight N. A. species 

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

 bv Dr. Geo. H. Horn in the 3d. vol. of the Trau. Am. Ent. Society. 



Family VI. HYDKOPHILID^. 



|FiK. 1 



UYiiKoriiii.rB;— n, larva of IT. piVc»*. Liim. ; «, egg-sase; (i. same opened showing airaujjenipnt of 

 ••UK" ; <^< pui>a— iiftiM- Ulanrhard : b. 11. iriaiKjularix. Say., natural size ; /, antenna ; ;;, anterior tarsiis of 

 female ; h, Hanio of ninlo, all niajjnitieil ; i, sulo view of the sternal spine — after Riley. 



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

 comi)osition meaning a lover of water. They constitute a somewhat ex- 

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

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

 alternately, whilst the Dytiscida- 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 Ilydrophilidir 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- 

 tenna^, and their long palpi, which are usually longer than the antenna*, 

 and are carried projecting forwards whilst swimming. The larvie of 

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

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

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



