NO. 6 GRASSHOPPER ABDOMEN SNODGRASS 5I 



closely associated with the lower margin of the ninth tergum. The 

 second valvifer {2V If) is clearly differentiated in the ninth segment, 

 and has essentially the adult form (H, 2Vlf). Between the bases of 

 the second and third valvulae of opposite sides are formed the small 

 median sclerites that become the intervalvulae of the ninth segment in 

 the adult. 



Throughout the development of the gryllid ovipositor, it is to be 

 observed, there is a significant difference in the position of the parts 

 derived from the two genital segments. The first valvulae and the 

 first valvifers are developed from the ventral membrane of the 

 eighth segment entirely behind the eighth sternum. The sternal plate 

 of the eighth segment, therefore, does not contain the limb bases of 

 this segment. The valvifers and valvulae of the ninth segment, on 

 the other hand, arise from the entire ventral region of this segment, 

 except for a small median part from which are formed the inter- 

 valvulae. We may presume, therefore, that the apparent sternal region 

 of the ninth segment has a coxosternal composition, as have the usual 

 definitive sternal plates of the abdomen. The median sternal part 

 forms the intervalvulae ; the lateral coxal areas give rise to the valvulae 

 and valvifers. In each genital segment the dorsal muscles of the re- 

 spective valvifers arise on the tergum. 



From the above it is evident that the facts of the development of 

 the ovipositor need " interpretation " to make them fit with the the- 

 oretical origin of the ovipositor from segmental limbs, but, it should 

 be observed, they are at least not inconsistent with this theory. It is 

 important to note, furthermore, that the first valvulae are the gona- 

 pophyses of the first gonopods, while the first formed processes of 

 the ninth segment are the third valvulae, which are elongations of the 

 coxopodites ; the second valvulae, or true gonapophyses of the ninth 

 segment, are of later development. This same order of development 

 of the ninth segment processes recurs in most insects with three valvu- 

 lar components in the ovipositor. In Gryllidae, as in Acrididae, the 

 second valvulae remain rudimentary. 



The primitive segmental relations of the valvifers in Gryllidae are 

 somewhat confused in the final development of the basal mechanism of 

 the ovipositor. Each first valvifer, as we have seen, in the last nymphal 

 stage of Gryllus (fig. 21 G) has a posterior lobe (3;) interposed be- 

 tween the base of the third valvula {3VI) and the small lateral sclerite 

 of the ninth segment (x), which latter has become closely associated 

 with the lower edge of the ninth tergum (IXT). In the adult cricket 

 (H) the sclerite .r is solidly fused with the lobe y and thus becomes 



