NO. 6 



GRASSHOPPER ABDOMEN SNODGRASS 



43 



are no tergal muscles in Acrididae corresponding with those inserted 

 on the intervalvulae in Gryllidae. (See Abdomen, Part II, Smith- 

 sonian Misc. Coll., vol. 89, no. 8, fig. 17 E, H, 5, 8.) 



The second valvulae are provided with a pair of short muscles aris- 

 ing anteriorly on the anterior intervalvula (fig. 17 B, C, 2/^), and 

 inserted distally in the free ends of the second valvulae. These small 

 intermediate valvulae evidently are functional in guiding the eggs 

 properly between the other valvulae in their passage through the 

 ovipositor. 



An important accessory of the acridid ovipositor is the egg guide. 

 This organ is a small, tapering median process arising from the re- 



IXTXT 



Fig. 18. — End of abdomen and ovipositor of Tcttigidca lateralis. 



A, terminal segments of abdomen, with ovipositor. B, left valvulae and 

 apodeme of ovipositor. C, ventral view of second and third valvulae, inter- 

 valvulae, and apodemes of ovipositor. 



fleeted distal end of the eighth sternum (figs. 4, 13, eg) directly in 

 line with the opening of the oviduct {Gpr) in the floor of the genital 

 chamber. The egg guide normally projects between the bases of the 

 ventral valvulae, and serves to direct the eggs issuing from the gono- 

 pore upward and into the intervalvular space of the ovipositor. It is 

 an immovable process developed in the nymph as a median outgrowth 

 from the posterior margin of the eighth sternum. 



The ovipositor of Tetrigidae, as illustrated by Tettigidea lateralis 

 (fig. 18), is of the acridid type of structure in that it is composed of 

 the first and third valvulae (B), and has a pair of lateral intervalvu- 

 lar apodemes (B, C, Ap) with muscles for opening the valvulae. The 



