NO. 6 GRASSHOPPER ABDOMEN SNODGRASS 39 



end of the abdomen (fig. i) beyond the eighth sternum (VlllStn) 

 from beneath the lobes of the eleventh segment {Eppt, Papt), and 

 thus might appear to belong to the ninth and tenth segments ; the first 

 valvulae, however, are developed in the nymph from the eighth seg- 

 ment, immediately behind the eighth sternum (fig. 22 A, C, iVl) , 

 and the second and third valvulae from the ninth segment (A, C, D). 

 In the adult several basivalvular sclerites are differentiated from the 

 bases of the first valvulae (figs, i, 17 A, a, b, c) , v^hich, though par- 

 tially overlapped by the eighth sternum, are entirely separated from 

 the latter by an inflection of the poststernal membrane that forms the 

 female genital chamber. Between the bases of the dorsal valvulae are 

 anterior and posterior intervalvular sclerites (fig. 17 B, aiv, piv) ; and 

 a pair of large apodemes projects forward in the body cavity from 

 the angles between the bases of the dorsal and ventral valvulae (A, B, 

 D, Ap). An important accessory of the acridid ovipositor is the egg 

 guide, a median process of the eighth sternum (fig. 20 A, eg). 



The first, or ventral, valvulae of Dissosteira Carolina (fig. 17 A, 

 B, E, I VI) are somewhat elongate lobes, flattened from side to side, 

 ending each in a decurved point. Proximally they are united by the 

 membranous integument between their bases, and their ventral walls 

 are continued into the dorsal wall of the genital chamber (fig. 20 A). 

 Each first valvula is differentiated into a strongly sclerotic terminal 

 lobe (fig. 17 A, iVl), and into a basal part containing a large lateral 

 basivalvular sclerite (a) and two narrow ventral sclerites {b, c). The 

 upper surface of the terminal lobe (B) is produced proximally as an 

 elongate plate, or ramus, at the end of which is a wide transverse de- 

 pression that fits closely upon a prominent abutment from the under 

 surface of the basal ramus of the corresponding third valvula (D, i). 

 Proximal to this articulation the dorsal wall of the ventral valvula 

 is membranous and shortly ends at the ventral lip of the hollow base 

 of the lateral apodeme (Ap). The lateral basivalvular sclerite of the 

 first valvula (A, a) is a prominent plate exposed on the side of the 

 abdomen behind the eighth sternum (fig. i). The posterior ventral 

 sclerite (fig. 17 A, B, b) is ordinarily partly exposed behind the 

 eighth sternum, but the anterior ventral sclerite (c) is concealed in 

 the dorsal wall of the genital chamber (fig. 20 A), where it flanks a 

 median channel containing the spermathecal aperture (fig. 17 E). 



The third, or dorsal, valvulae of Dissosteira (fig. 17 A, B, 3VI) 

 resemble the ventral valvulae in general form, except that their points 

 are turned upward, but they are larger and stronger than the ventral 

 valvulae, and they have no basivalvular sclerites. Their dorsal surfaces 

 proximal to the upcurved points are broad and flat. The under surface 



