48 NOTONECTINA. 



Section ^.—NOTONECTINA. 



Notonectides^ p., Leach ; Am. et Serv. 

 Notonectici, p., Burm. 

 Notonectidae, p., Westw. 

 Notonectidea, Notonectas et Plese, Fieb. 

 . Notonectica, Fior. 



Posteriorly, laterally compressed; longitudinally convex. ITead 

 large, transverse, convex, rounded in front ; Crotvn and Face not 

 separated. Antennce 4-jointed. Eyes large, triangular, posterior. 

 nostrum free, 3 or 4-jointed. Elytra corneous or pergamentous 

 throughout ; Emholium linear, oblique or horizontal ; Membrane 

 ample and saddle-formed, or wanting. Legs : first pair inserted on 

 the posterior margin of the prosternum ; tarsi 2 or 3-jointed. 

 These insects swim with their backs downwards, and move rapidly 

 by means of their long hind legs. 



Family 1.— NOTONECTIDJE. 



Long-oVal. Head large, with the eyes almost reniform, curved 

 under. Antenncs : first joint short, stout ; second long, very stout ; 

 third in length subequal, narrower, cultrate, with long capitate 

 hairs ; fourth very short, conical. Eyes approximate. Rostrum 

 4-jointed. Pronotiun hexagonal, subtrapeziform. ScuteUum large. 

 Elytra pergamentous ; Emholium long, linear, liorizontal ; Mem- 

 hrane indistinctly separated from the corium, gradually thinner, 

 folded longitudinally ; apex deeply notched. Legs subequal ; an- 

 terior tihice dilated ; posterior pair longest, and with their tarsi long 

 ciliated ; tarsi all 2-jointed. 



Abdomen with a ciliated middle keel. Gen. 1, Notonecta. 



t^AMILY 2.— PLEID^. 



Ovate, broadest in front, very convex longitudinally, the abdomen 

 laterally compressed and angulated. Head broad, curved under. 

 Antennce : first and second joints very short ; third long, broad- 

 fusiform ; fourth small, clavate, inserted obliquely below the apex of 



