NO. b INSECT ABDOMEN SNODGRASS 49 



subgenital plate underlapping the base of the ovipositor. The first 

 valvifers {iVlf) are displaced posteriorly, and are thus entirely sepa- 

 rated from the tergum of the eighth segment, though they are in closer 

 association with the eighth sternum. The broad ovipositor shows only 

 the first and third valvulae externally {iVl, 3VI) , the second valvulae 

 being concealed between the outer blades. 



The mature ovipositor of Scuddcria is strongly upcurved, and its 

 free margins are toothed (fig. 13 C). The mechanical relations of the 

 parts of the organ to one another can be studied only in fresh speci- 

 mens, or in specimens preserved in liquid ; the parts are best seen 

 when the entire ovipositor is removed from the body. Each of the 

 first, or ventral, valvulae (iVl) is attached to a small, oval lateral 

 plate at the base of the ovipositor (iVlf), which is the first valvifer 

 (" pileolus " of Chopard, 1920). The first valvifer and its valvula are 

 continuous, but they are flexible on each other by reason of the nar- 

 rowness of their union (c). The upper end of the valvifer is con- 

 nected, also by a flexible union (&), with the basal part of the broad 

 third, or dorsal, valvula (sVl), the side of which it overlaps ven- 

 trally. From an angle on the anterior margin of the first valvifer there 

 projects internally a strong apodeme (e), on which muscles are at- 

 tached. If the first valvifer is revolved upward on its flexible dorsal 

 attachment (b), the ventral valvula is retracted. In some of the 

 Tettigoniidae the proximal part of the first valvula is more or less 

 distinctly difterentiated as a basal sclerite, or basivalvula, shown in 

 the nymph of Scudderia (fig. 12, hv). 



Each of the dorsal, or third, valvulae of Scudderia (fig. 13 C, 3VI) 

 is somewhat thickened at its base where the first valvifer is attached, 

 there being differentiated here an area {2Vlf) that evidently corre- 

 sponds with the second valvifer of an ovipositor having a more typical 

 structure (figs. 10 C, 31 B), in which each limb base element of the 

 ninth segment becomes divided into a valvifer {2Vlf) and a distal 

 lobe {3VI). The muscles inserted on this basal part of the dorsal 

 valvula in Scudderia and other tettigoniids are those of the second 

 valvifer in other insects. The area in question is sometimes called 

 the " basivalvula " of the dorsal valvula, but the term is unnecessary 

 and misleading since the area so designated does not correspond mor- 

 phologically with the basivalvula of the ventral valvula. A strong 

 apodeme (fig. 13 C, g) projects from the anterior margin of the 

 valvifer area. This apodeme is the superior apophysis of Walker 

 (1919). 



The dorsal and ventral valvulae are rather weakly connected with 

 each other in Scudderia, but in the Tettigoniidae and Gryllidae gen- 



