44 



SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 8o 



mining factor of the pleural structure in. the thorax was the presence 

 of potential wing lobes on each of the thoracic segments. 



Carpentier (1921), in his study of the pleura of wingless Orthop- 

 tera, shows that the pleuron of the prothorax is identical in structure 

 with the pleura of the other two thoracic segments, a condition sug- 

 gestive of the former presence of wings on the prothorax, though 



.Tn--- 



Fig. 20. — Diagrammatic structure of a wing-bearing segment with a phragma 

 attached to each end ; wing cut off at base ; coxa removed. 



ac, antecostal suture ; Acx, precoxal bridge ; ANP, anterior notal wing process ; 

 Aph, anterior phragma; Aw, prealar process, or bridge; Ba, basalare, episternal 

 epipleurite ; Bs, basisternum ; CxC, coxal cavity ; CxP, pleural coxa! process ; 

 Epm, epimeron ; Eps, episternum ; Fs, f urcisternum ; Mb, remnant of inter- 

 segmental membrane ; Pc, precosta ; Pcx, postcoxal bridge ; pla, external root of 

 pleural apophysis; PIS, pleural suture; PN, postnotum (postscutellum) ; PNP, 

 posterior notal wing process; Pph, posterior phragma; PS, poststernum ; Psc, 

 prescutum ; Pzv, postalar bridge ; S, sternum ; Sa, subalare, epimeral epipleurite ; 

 sa, external root of sternal apophysis ; Scl, scutellum ; Set, scutum ; Tn, trochan- 

 tin ; IVP, pleural wing process. 



Carpentier docs not commit himself to this conclusion. The mental 

 picture of a pair of fully-developed wings on each of three consecu- 

 tive segments, however, is not convincing as a mechanical reality ; 

 but the degree of development in the prothoracic pleura may be taken 

 to mean that the paranotal lobes of the prothorax once reached a 

 stage of development in which they, as well as those of the meso- 

 thorax and metathorax, required the supi:)ort of the pleura. Beyond 

 this stage, the lobes of the second and third segments were evolved 



