NO. 6 GRASSHOPPER ABDOMEN — SNODGRASS 67 



sclerites (g) in the floor of the genital chamber (figs. 25 D, 33 B, 

 35 B), on which are inserted strong muscles (^61) from the lateral 

 parts of the ninth abdominal tergum. 



The aedeagus is ordinarily entirely concealed within the posterior 

 part of the genital chamber beneath the hood of the pallium (fig. 

 24 A). In the protracted condition, however, the organ is exposed 

 by a retraction of its coverings (fig. 33 B). The genital lobe of the 

 ninth sternum (IXSL) is now depressed, and the pallium is turned 

 inside-out, appearing in this condition as a large posterior fold (Pal) 

 around the base of the aedeagus, while the basal fold of the genital 

 chamber floor (bf) correspondingly embraces the aedeagus anteriorly; 

 the epiphallus (Epph) has emerged from its pocket beneath the 

 eleventh segment, and stands boldly exposed on the projected floor 

 of the genital chamber anterior to the ensheathing folds of the 

 aedeagus. 



The exsertion of the phallic organs would appear to be accomplished 

 by pressure resulting from a contraction of the pregenital part of the 

 abdomen, since there are no muscles connected with the genital organs 

 capable of producing the protracted condition of the latter (fig. 33 B). 

 The aedeagus apparently is held in the position of retraction by a 

 broad sheet of muscles on each side (fig. 25 A, 266) arising medially 

 on the ninth abdominal sternum and attached dorsally on the lateral 

 margins of the genital chamber floor. To be exserted, the aedeagus 

 must first be drawn forward from the pocket of the pallium ; its 

 release from the latter evidently is effected by the contraction of the 

 strong muscles (D, 261) inserted on the small sclerites (g) at the 

 sides of the epiphallus, which take their origins on the lateral parts 

 of the ninth tergum. The epiphallus itself is provided with a pair of 

 large muscles (A, 26/) arising medially on the ninth sternum, which 

 curve upward around the anterior end of the endophallic bulb and 

 insert on the lateral lobes (h) of the epiphallus. It is probable that 

 a contraction of these muscles brings about an elevation of the distal 

 parts of the phallic apparatus, and that pressure from within the 

 abdomen then protrudes the aedeagus. A second pair of epiphallic 

 muscles (B, 2/8) arises posteriorly on the zygoma of the aedeagal 

 apodemes and extends anteriorly to the lateral lobes of the epiphallus. 

 The action of these muscles is not clear, but the muscles undoubtedly 

 play some part in the function of the epiphallus in copulation. 



The following description of the musculature of the aedeagus and 

 endophallus is based on a study of Dissosteira Carolina, but a cursory 

 examination of the other species suggests that the musculature and 

 mechanism of the acridid male organs are the same throughout the 

 family. 



