1918J Thoracic Sclerites of Ilcmiptcni 241 



ward from the coxal articulation (x) to a point about midway up 

 the pleuron. The division of the pleuron is usually indicated 

 on the inner side of the plate by a ridge, the internal represen- 

 tative of the pleural suture, even when the ])leural suture itself 

 is entirely absent. It must be mentioned here that the coxal 

 cleft in the metathorax does not occupy, a position homologous 

 with that in the mesothorax and hence cannot be taken as a 

 "landmark" for the separation of episternum and epimeron in 

 that segment. 



In the Nepidae (Figure 17) and the Thyreocoridas (Figure 



• 25) the episternum of the mesothorax is divided into anepister- 



num (aes) and katepisternuiji (kes), a condition not general 



with the Heteroptera, but met with in Cicadidte, Jassid^e and 



Aphididce, among the Homoptera. 



The distorted condition remarked above in connection with 

 Belostoma is noticed also in the Corixidae (Figure 19) and 

 Notonectidae (Figure 15). The backward projecting flap of the 

 epimeron of Belostoma finds its homologue only in the Nepid^ 

 (Figure 17). though in most forms the posterior margin of the 

 epimeron overlaps more or less the anterior part of the next 

 segment. In the higher Heteroptera, among them the Redu- 

 viidae, Emesida; (Figure 14), Nabida? (Figure 24), Gerrid^E 

 (Figure 21), Capsidae, Phymatidae, L^'ga^id^e, Berytidas (Figure 

 22), Coreidas (Figure 23) and Pentatomida?, the shape of the 

 mesopleuron, and usually of the metapleuron is rectangular. 

 The coxa ( ex) retains its position at the rear of the segment even 

 in the elongated forms, Emesa (Figure 14), Gerris (Figure 21) 

 and Neides (Figure 22), for example. In the Gerrida? (Figure 

 21), where the body is very nearly cylindrical, the mesocoxa 

 (cxo) is partially encased by a cylindrical, bulging socket. The 

 coxal cleft (co) runs the length of this socket. A trochantin (tn. 

 Figure 15) is very probably present in most of the Heteroptera, 

 though its position beneath the episternum prevents it from 

 being easily detected. 



Sternum. The mesothoracic sternum is usually indistin- 

 guishably fused with the pleuron, and consists apparently of a 

 single sclerite. In some instances, namely in the Notonectidae 

 (Figure 15), Reduviidae, Emesida? (Figure 14), Cimicidte, Phy- 

 matidae and Tingitidae, a faint line more or less distinctly marks 

 off the sternum from the pleuron. 



Metathorax. Figures 14, Ifi, 19, 20, 21, 22, 23, 24 and 25. 



