CLASSIFICATION OP INSECTS. 243 



uniform structure, not formed for leaping ; the tarsi 

 are three-jointed : terrestrial ; run fast ; fly rapidly, 

 but not far at a time ; feed generally on the sap of 

 vegetables, sometimes on other insects, and occa- 

 sionally, but apparently unnaturally, on the blood 

 of vertebrate animals. Citnex, &c. 



796. Water-bugs {Hydrometrites). AntenniE 

 elongate, conspicuous, four- or five-jointed ; fore- 

 wings coriaceous, of uniform substance ; hind- 

 wings membranaceous ; all the wings linear ; legs 

 of uniform structure, very long, not formed for 

 leaping; tarsi three-jointed ; body elongate, linear: 

 aquatic, running with ease and rapidity on the 

 surface of water. Hydrometra, Gerris, Velia. 



797. Water- scorpions (Nepites). Antenna; 

 very short, concealed below the head ; fore-wings 

 coriaceous, crossed at the apex ; hind-wings mem- 

 branaceous, completely concealed beneath them ; 

 fore-legs hooked, predatory ; tarsi with a single 

 joint; middle- and hind-legs not formed for swim- 

 ming ; tarsi two-jointed ; tail armed with two long 

 setaceous appendages : aquatic ; caniivorous ; 

 crawl on aquatic plants, but do not swim. lia- 

 natra, Nepa. 



798. Water-boatmen (NotonecHtes). Anten- 

 na; very short, concealed below the head ; fore- 

 and hind-wings as in the preceding; fore-legs 

 unarmed, middle- and hind-legs formed for 

 swimming ; all the tarsi two-jointed ; tail without 

 appendages: aquatic; carnivorous; swim with 



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