No. 1774. 



THORAX OF HYMEN0PTERA—SN0DGRAS8. 



47 



Peps, 



sternum are one or two ejnsternal jmraytera, small plates connected 

 with the head of the wing and giving insertion to the extensor and 

 pronator muscle of the wing. At the upper end of the epimerum 

 there is likewise frequently one and very rarely two epimeral parap- 

 tera. The metapleurum of tlie stonefly, shown in figure 5, has 

 only one parapteral plate (P), situated just in front of the wing 

 process and not entirely disconnected from the episternum. 



Audouin (1824) first described the "paraptere" as a little plate 

 of the pleurum situated in front of the wing base. The present 

 writer, in a former paper (1909), applied the term in the plural 

 to the series of little subalar pleural plates both before and behind 

 the wing process, as defined here. Some authors have supposed 

 that Audouin referred to the tegula'in describing the "paraptere," 

 but his description shows clearly what he meant. (The present 

 writer has fully discussed this subject 

 in a former paper, 1910, footnote a, 

 pp. 20 and 21.) 



Ventrad to the episternum and in 

 front of the coxa is a variable plate 

 called the trochantin (fig. 5, Tn). 

 It is best developed in the lower 

 orders, where it articulates by its 

 lower end with the ventral rim of 

 the coxa; but it is often rudimentary 

 or is fused with the lateral precoxal 

 part of the sternum. In cases where 

 the coxa appears to articulate ven- 

 trally with the sternum, it may be 

 that the articulation is really with the 

 absorbed trochantin. 



In the Orthoptera and Euplexop- 

 tera there is very often present a 

 plate lying before the episternum which the writer (1909) has 

 termed the preepisternum (fig. 7, Peps). In a few cases it forms 

 a continuous band from the front of the episternum to the front 

 of the sternum (presternum). It was described by Verhoeff (1903) 

 as the "katopleure." When the preepisternum does not reach the 

 sternum ^ there is very frequently a plate lying between it and the 

 sternum (fig. 7, x). In a former paper on the thorax the writer 

 (1909) followed the prevalent custom, especially among German 

 entomologists, of regarding these plates as separated presternal 

 sclerites (the ''Vorplatten" of the Germans). Crampton (1909), 

 however, has elaborated the following theory based principally on 

 a study of the Blattidse and Euplexoptera. He supposes that in a 

 primitive form the chitin was continuous across the ventral surface 



Fig. 7.— Right half op mesopectus of 

 Spongiphora apicidentata (earwig): 

 Cx, coxa; CxP, pleural coxal process; 

 Epm, epimerum; Eps, episternum; Peps, 

 preepisternum; PS, pleural suture; 

 S, sternum; Tn, trochantin; x, plate 



BETWEEN THE STERNUM AND PREEPISTER- 

 NUM. 



