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SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL, 94 



by Walker (1922), they " are surprisingly unlike those of the Acridi- 

 dae." The phallus of Tettigidea lateralis (fig. 27 D) consists of a 

 low ovate elevation on the floor of the genital chamber beneath the 

 pallial valve (C). Sclerites in the lateral walls of the organ converge 

 and unite anteriorly in a median process armed with small spines. 

 Between the lateral plates is a large, widely open, membranous cavity, 

 into the bottom of which the ejaculatory duct opens anteriorly (D, 

 Gpr). The posterior wall of the cavity is directly continuous with 

 the inner membranous fold of the pallium {Pal'). The ejaculatory 



PlVlv 



..Phi 



C / "'^'"'^^^^ D 



Fig. 2y. — Abdomen and male genitalia of Tettigidea lateralis (Tetrigidae). 



A, terminal part of abdomen. B, dorsal view of pallial valve (PlVlv) and 

 anterior process of phallic organ. C, lateral view of ninth sternum and pallial 

 valve, with phallic organ exposed beneath the latter. D, the phallic organ, dorsal 

 view, with base of inner pallial fold. 



duct has strongly muscular walls, and groups of muscle fibers arising 

 on the phallic sclerites are inserted on its terminal part. Coition is 

 probably effected by evagination of the endophallic sac. According 

 to Walker the external phallic plates of the tetrigid organ represent 

 the epiphallus (" pseudosternite ") of the Acrididae ; but the attach- 

 ment of the ejaculatory muscles upon them would make it seem more 

 probable that they are external representatives of the invaginated 

 endophallic plates of the Acrididae. These plates, Walker himself 

 contends, are derived from external plates or processes (" para- 

 meres ") of other Orthoptera. 



