I'ils] Thoracic Sclerites of llemiptera 239 



MODIFICATIONS IN OTHER HETEROPTERA. 



As in the Homoptera, it is difficult to trace the modifications 

 of the higher Heteroptera along definite lines of development. 

 Unlike the Homoptera, however, the higher families of Heterop- 

 tera show considerable departure from the primitive type, and 

 resemble only slightly the Belostomatidae and their near rel- 

 atives. Of the forms studied only the Corixidae (Figure 19), 

 Notonectidse (Figures 15 and 16), and Nepidse (Figure 17) show 

 characters very similar to Belostoma. The Nepidas seem in a 

 number of ways to be a connecting link between these and the 

 more modified forms. 



Before commencing the discussion of the modifications of 

 the thorax in the Heteroptera, it may be well to mention 

 Heymons', 1S99, interpretation of the thorax of Nepa cinerea, 

 since this work is frequently referred to by other writers. In 

 the later larval stages, which he studied and figured, the body is 

 much flattened dorso-ventrally. The pleural plates are thus 

 apparently ventral. Heymons has hence called the episternum 

 of the various segments the "lamina subcoxalis" or subcoxal 

 plate (Subcoxalplatte), since its true position is beneath the 

 coxa. The mesothoracic epimeron is a sickle-shaped flap, which 

 extends beyond the hind coxa. This sclerite was considered by 

 Heymons to be the metathoracic "pleurite," but that it is most 

 certainly the mesothoracic epimeron is clearly seen by lifting 

 the flap and observing its attachment. A sclerite which 

 Heymons designates as paratergite, the writer believes from its 

 location to be the metathoracic epimeron. 



Prothorax. 



This segment is fairly constant throughout the group. It 

 may vary in size and shape, but in its ground plan it is essentially 

 the same in all the families studied. It is of minor importance 

 in the study of the sclerites, and is not figured in this paper. 

 One notable exception obtains in the Gerridae, where the scu- 

 tellar region of the pronotum extends so far back as to entirely 

 cover the mesonotum. 



Mesothorax. Figures 14, 15, 17, 18, 19, 21, 22, 23, 24 and 25. 



Notum. The notum of the mesothorax in the suborder 

 Heteroptera is usually divided by sutures into pretergite (prt), 

 prescutum (psc), scutum (sc), scutellum (si) and postscutellura 



