NO. 6 



GRASSHOPPER ABDOMEN SNODGRASS 



IS 



THE CERCI 



The cerci of Acrididae vary in form and size from simple peglike 

 organs (fig. ^^ A, Ccr) to broader lobes of irregular shape (fig. 35 A), 

 sometimes provided with accessory processes (fig. 36). The cerci of 

 Dissosteira are of the simple type; they are longer in the male (fig. 

 7B) than in the female (A), but they have the same structure 

 in both sexes. The appendages arise from membranous areas behind 

 the posterior margin of the tenth abdominal tergum between the 

 bases of the epiproct and the paraprocts (B, Cer). The base of each 

 cercus has a large irregular lobe (b) extending mesally beneath the 



Fig. 



-The cercus and its associated musculature. Dissosteira Carolina. 



A, left cercus of female, dorsal view. B, 

 terminal part of male abdomen, dorsal view, 

 cercus and its muscles. 



same of male. C, left half of 

 D, inner view of base of right 



edge of the epiproct, but it is not articulated to the surrounding scle- 

 rites. The shaft of the organ is clothed with long and short setae, the 

 short setae being more numerous on the apical part. Many of the 

 larger hairs, especially on the proximal half of the cercus, arise from 

 large, conspicuous, rosette-like alveoli with dark scalloped margins. 

 Each cercus is penetrated by a large nerve, and its setae apparently are 

 tactile organs. 



Four muscles are intimately associated with each cercus, and are 

 clearly concerned with its movements, though only two of them are 

 inserted directly on the base of the cercus (fig. 7 D). The cerci of the 

 male are erected during copulation and grasp the base of the sub- 

 genital plate of the female. The elevation of each appendage is pro- 

 duced by the two muscles, abroad median muscle (-S8) and a smaller 



