168 IKSECTA. 



Geriiis, Lat. 



Where the antennae are filiform, the sheath of the sucker is triar- 

 ticulated, and the second pair of legs are very remote from the first, 

 and at least double the length of the body *. 



The two anterior legs, as well as in the following subgenus, act as 

 pincers. 



Velia, Lat. 



Where the antennae are also filiform, but the sheath of the sucker 

 has but two apparent joints, and the legs, much shorter, are inserted 

 at nearly equal distances from each other f . 



FAMILY II. 



HYDROCORISiE. 



In our second family of the Hemiptera, the antennse are inserted 

 and concealed under the eyes; they are shorter than the head, or 

 hardly as long. 



All these Insects are aquatic, carnivorous, and seize others with 

 their anterior legs, which flex on themselves and act as pincers. 



They sting severely. 



Their tarsi present but one or two joints. Their eyes are in gene- 

 ral remarkably large. 



Some — Nepides — have the two anterior legs in the form of pincers, 

 composed of a thigh, either very thick or very lung, with a groove 

 underneath for the reception of the inferior edge of the tibiae, and 

 of a very short tarsus ; or one that is even confounded with the tibia, 

 and forming with it a large hook. 



The body is oval and much depressed in some, and linear in others. 

 They form the genus 



Nepa, Lin., 



Or that of the Aquatic Scorpions, as they are commonly called, which 

 is thus divided : 



Galgulus, Lat., 



Where all the tarsi are similar, cylindrical, and composed of two 

 very distinct joints, the last with two terminal hooks. The antennae 

 appear to consist of but three joints, the last of Avhich is the largest 

 and ovoid \. 



The antennae of the following genera are quadriarticulated, and 

 the anterior tarsi terminate simply in a point or hook. 



* Lat., Gener. Crust et Insect., Ill, p. 131. 



t Lat. II). 



X Lat. lb., p. 144 ; Naucoris ocidata, Fab. 



