44 



SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 82 



The pterotlioracic pleura. — The pleurites of each side of the meso- 

 thorax and metathorax are firmly united to form continuous lateral 

 walls of the pterotlioracic region (fig. 26) in which the episterna and 

 epimera {Eps, Epin) are distinct plates separated by oblique grooves 

 sloping from above downward and posteriorly. The first principal 

 groove is the pleural suture of the mesothorax {PIS2), the second is 

 the intersegmental line, the third is the pleural suture of the meta- 

 thorax (PIS3). Each pleural suture terminates above in a large wing 



WP. 



/ 



2 Sa Ba WP, 



Fig. 26. — The pterothoracic pleura of Dissosteira. 



Ba, basalar sclerites ; Cx, coxa ; Epm, epimeron ; Eps, episternum ; Fim, base 

 of hind femur ; /, prepectal suture ; PIS, pleural suture ; PNz, lateral arm of 

 metathoracic postnotum ; Ppct, prepectus ; r. pleuro-sternal suture ; S, sternum ; 

 Sa, subalare ; Spz, mesothoracic spiracle ; Sps, metathoracic spiracle ; Tn, tro- 

 chantin ; Tr, trochanter ; WP, pleural wing process. 



process {WP2, WP3), and below in the pleural articulation of the 

 coxa. The episternum of each segment (Epso, EpSz) is united ven- 

 trally before the coxal cavity with the edge of the sternum, the line of 

 union (r) in the adult insect being obsolete in the mesothorax, but 

 distinct in the metathorax. In the nymph of Dissosteira and of other 

 Acrididae (fig. 27 A) the ventral edge of the precoxal part of the 

 pleuron in both the mesothorax and the metathorax is distinctly sepa- 

 rated from the sternum ; in the nymph of Gryllus (B) a precoxal plate 

 (Ac.v) is separated from the pleuron and intervenes between the 

 episternum and the sternum. The episternum of the mesothorax of 

 Dissosteira (fig. 26, EpSo) is marked anteriorly by a submarginal 



