562 The University Science Bulletin. 



Its ventral basal part appears to be entirely membranous. The 

 pygofers fit very snugly around the lateral valves, but are not at- 

 tached to them. These valves are tough, fairly well chitinized and 

 with their outer surfaces pubescent. Their ventral surfaces are 

 plainly visible from an external view. 



The ventral valves (pi. LX, fig. 2) are the middle pair of valves. 

 Other names which have been applied to them are middle valves, 

 anterior processes or ventral processes. They arise from the eighth 

 sternite, to which they are still attached in the adult. Each valve 

 is fastened to its half of the eighth sternite by a membrane which 

 connects the mesal corner of the sternite and the cephalomedian 

 angle of the valve. They are flat rather broad processes, which 

 taper to a fine point and which bear a broad notch near the base of 

 the dorsal margin. The ventral valves enfold the dorsal valves and 

 the ventral and dorsal valves of each side are fastened together by a 

 tongue-and-groove connection. The ventral valves are not as 

 heavily chitinized as either the lateral or dorsal ones. 



The dorsal valves (pi. LX, fig. 5), which have also been called 

 inner valves or median valves, are the innermost of the three pairs 

 of valves, and make up the ovipositor proper. They arise from 

 a genital area on the ninth segment of the nymph and are still at- 

 tached in the adult stage to the cephalic end of the ninth sternite. 

 Each valve is a flat, bladelike structure, broader at the base, but 

 tapering to a pointed apex. The basal half of their inner or dorsal 

 margins are united and the free apical portions bear teeth. These 

 teeth are small, sharply pointed, with broad, shallow indentations 

 between them, and are about fifteen in number. The teeth are used 

 as a saw with which to cut the plant tissue. The ventral margins of 

 these valves bear heavily chitinized grooves into which the tongues 

 of the ventral valves are inserted. 



Extending along the approximate median line of the ventral 

 valves is a slender, chitinous rodlike structure. Superficially this 

 appears to be a chitinous thickening of the valve, but when it is 

 traced cephalad it is not found to be attached basally to the sclerite 

 to which the valve is fastened. The sclerite to which it is fastened 

 is a small, triangular plate (pi. LX, fig. 4), which is attached to the 

 lateral margins of the ninth sternite, the cephalic margin of the 

 pygofer, and normally lies hidden beneath the eighth sternite. It 

 ])robably represents the ninth pleurite. 



