THE NEPIDiB. 125 



departing considerably from the usual form of the in- 

 sects contained in it. These are Ernesa, Cerascopus, 

 and Ploiarta, which are very elongate and slender, — 

 indeed, perfectly filiform. The two former occur in 

 America, and the latter in Europe, Their anterior 

 legs are raptorial, and, we believe, rarely used in pro- 

 gression, but kept vibrating with the antennae, which 

 are exceedingly slender and angulated : the interme- 

 diate and posterior legs are also very long; and it is 

 upon them that these insects stalk about seeking their 

 prey. They are found chiefly in houses. 



(116.) Our next group, the Nepid^, will detain us 

 but a few moments. The genera differ considerably 

 from each other in form : thus, JVepa itself is broad, ovate, 

 and quite flat; Ranatra, very elongate and cylindrical; 

 Belostoma, nearly ellipsoidal ; and Naucoris, almost cir- 

 cular, and slightly convex. These insects all inhabit 

 the water, as all of the preceding were occupants of the 

 land. They are very predacious, which is sufficiently 

 evinced by their powerful anterior predatorial legs. It 

 is probable that the Galgulini should form a component 

 portion of this group ; for, excepting that their posterior 

 legs are cursorial instead of being ciliated for swimming, 

 they very closely resemble Naucoris. From structure, 

 •as we observe above, they are distinctly land, as the 

 others are water insects, and inhabit the banks, forming 

 holes in the ground, where they lurk for their prey. 



(117.) Velia, Gerris, and their allies, appear quite 

 as typical of a group as any of the preceding. Although 

 much resembling Ranatra among the last, and Eme&a 

 among the Reduvii, they possess peculiarities of struc- 

 ture and habits which at once distinctly estrange them 

 from both. In the first place, they inhabit the surface of 

 the water, where they run with considerable velocity; and 

 thus appear a sort of analogy among haustellate insects 

 to what we observe in Gyrinus among the natatorial 

 Coleoptera. The relative proportions of their legs differ ; 

 thus, in Velia, Gerris, and Hydroessa, the intermediate 

 legs are the longest, and the anterior usually kept bent : 



