46 



SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 82 



PIA, SA), and the two are connected by a dense mass of short muscle 

 fibers (figs. 34, 35, 86, 115). 



Of particular interest in the pterothoracic pleuron are the epiplexi- 

 rites, or the small plates situated in the membranes below the bases of 

 the wings (figs. 26, 28, 29, Ba, Sa). Upon these plates are inserted 

 the principal so-called direct muscles of the wing mechanism. In the 

 grasshopper there are three epipleurites in each segment, two {Ba) 



WP, 



CxPr 



Fig. 28.- 



-Iniier surface of right pterothoracic pleura of Dissostcira, showing the 

 endoskeletal features. 



Lettering as on figure 26, with the following 

 process ; PIA, pleural arm ; PIR, pleural ridge. 



additions : CxP, pleural coxal 



situated before the wing process and articulated to the episternum, and 

 one {Sa) in the membrane behind the wing process and above the 

 epimeron. The episternal epipleurites are distinguished as the 

 hasalarcs, or hasalar sdcritcs {Ba), the epimeral epipleurite as the 

 subalarc or suhalar sclerite {Sa). In most insects there is but a single 

 basalare. In Dissosteira the basalar sclerites are freely hinged to the 

 upper margin of the episternum before the wing process (fig. 29, iBa, 

 2Ba) so that they can be turned inward and downward by the muscle 

 inserted on their inner faces (fig. 49, E, M'). The function of the 

 epipleurites in connection with the movement of the wings will be de- 

 scribed in Section V. 



