INTRODUCTION. 



b'^. Hemelytra entirely membra- 

 naceous Henicocephalidae. 



b. Tarsi two-jointed. 



a^. Anterior legs normal. 



«'■'. Hemelytra more or less re- 

 ticulate, consisting of strong 

 irregular thick lines forming a 

 framework of cells. Anterior 

 legs inserted on tlie posterior 



margin of the prosternum Tingididae. 



b"^. Hemelytra neither reticulate nor 



cellular. Anterior legs inserted 



on the disk of the prosternum . Aradidae. 



¥. Anterior legs short and stout, with 



long coxae, short thick femora, and 



cuvvate pointed tibise ; frequently 



witliout tarsi Phymatidas. 



b. Mesopleurse and metapleurse composed 

 of several pieces ; hemelytron with a 

 cuneus. ' 



a, Hemelytron with an embolium. 



a\ Ocelli absent Cimicidae. 



b^. Ocelli present. 



cr. Antennae long and thin, clothed 



with long hairs: third and 



fourth joints together twice as 



long as the first and second .... Ceratocombidae, 

 b-. Antennae not very thin, nor 



clothed with long hairs, third 



and fourth joints not nearly 



twice as long as the first and 



second Anthocoridae. 



b. Hemelytron without an embolium. . . . Capsidae. 

 2. Abdomen clothed beneath with a silvery 



velvety pubescence. (Species aquatic or 

 subaquatic.) 



A. Antennae five-jointed Hebridae. 



B. Antennae four-jointed Hydrometridae. 



Seeies II. Antennae concealed, either situate 

 on the underside of the head to 

 which they are closely pressed, or in 

 foveas under the head. {Aquatic.) CRYPTOCERATA. 



A. Body short and broad; head very broad, 



with prominent eyes ; ocelli present. 



Posterior legs thin, formed for running . Pelegonidae. 



B. Body elongate or ovate, head of moderate 



size, 

 a. Anterior legs inserted on disk of anterior 

 margin of prosternum. 



a. Antennas with four joints ; no anal 



appendix. 



a' . Posterior tibiae spinulose Naucoridae. 



¥. Posterior tibiae flattened and pro- 

 vided with swimming-hairs Belostomatidae. 



b. Antennae with three joints; abdomen 



with a long tubular appendix Nepidae. 



TOL. I. d 



