NO. 6 GRASSHOPPER ABDOMEN SXODGRASS 4I 



apodemes of the acridid ovipositor represent anterior apodemal proc- 

 esses of the second valvifers in other insects, but it is quite impossible 

 to reconcile the musculature of the acridid apodemes with that per- 

 taining to the second valvifers in the usual type of ovipositor. Accord- 

 ing to Walker (1919) the ovipositor apodemes of Melanoplus are 

 formed in the nymph as invaginations at the angles between the bases 

 of the valvulae. It is perhaps possible that they are highly developed 

 anterior apodemes of the ninth sternum (the latter being represented 

 by the intervalvulae), since the space between the bases of the dorsal 

 valvulae is bridged by the anterior intervalvula. It is significant that 

 the ventral dilators of the rectum, which in the male arise anteriorly 

 on the ninth sternum, take their origins in the female on the ovipositor 

 apodemes (fig. 17 B, 264). 



The muscles of the acridid oviix)sitor function as protractors and 

 retractors of the entire organ, as levators and depressors of the first 

 and third valvulae, as abductors and adductors of the same valvulae. 

 and as motors of the second valvulae : but it appears that some of 

 them may act in more than one capacity. As above noted, it will be 

 fruitless to attempt to trace any homologies between these muscles 

 and the usual muscles of the ovipositor in other insects. It should be 

 observed, however, that with the absence of valvifers in the acridid 

 ovipositor there is correlated an absence of dorsal muscles correspond- 

 ing with those ordinarily inserted on the valvifers. 



The exsertion of the ovipositor evidently is brought about by two 

 pairs of muscles inserted on the anterior ends of the lateral apodemes 

 (fig. 17 A, C, 2f,6, 262). Of these muscles those of the first pair are 

 the short protractors {2^6) arising by wide bases on the anterior 

 lateral parts of the eighth abdominal tergum (fig. 13). The others 

 are the long protractors (fig. 17 C, 262) arising laterally on the pos- 

 terior margin of the ninth tergum (IXT). Retraction of the ovi- 

 ])Ositor is accomplished apparently by a pair of ventral muscles of 

 the first valvulae. by lateral muscles of the third valvulae, and by 

 muscles of the anterior intervalvula. The retractors of the first val- 

 vulae arise anteriorly on the eighth sternum (fig. 13, 248) and in 

 Dissosteira are inserted on the anterior ventral basi valvular sclerites 

 (fig. 17 E, 248). In Melanoplus, however, these muscles are inserted 

 on anterior pockets of the genital chamber (fig. 20 C, 248). The re- 

 tractors of the third valvulae are lateral muscles arising anteriorly 

 on the ninth tergum (fig. 17 C, 26^) and inserted posteriorly on the 

 lateral margins of the bases of the third valvulae. These muscles would 

 appear to act also as abductors of the valvulae. The retractors of the 



