42 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 94 



anterior intervalvula (C, D, 241) are a pair of slender muscles aris- 

 ing anteriorly on the eighth sternum (fig. 13) ; they probably assist 

 also in the adduction of the valvulae. 



The muscles that open the valvulae dorsoventrally consist of the 

 four huge bundles of fibers arising on the lateral apodemes, one pair 

 dorsally (fig. 17 A, B, 2yi), the other pair ventrally {2'/2). The 

 dorsal muscles, which are the levators of the third valvulae, are in- 

 serted dorsally in the bases of these valvulae ; the ventral muscles, or 

 depressors of the first valvulae, are inserted within the bases of the 

 first valvulae on the lateral basivalvular sclerites and on the posterior 

 ventral sclerites (A, E, a, b). These four powerful muscles of the 

 ovipositor produce the movements of the valvulae by which the earth 

 is compressed peripherally in the digging of the egg chamber in the 

 ground. 



The closing of the valvulae evidently is produced by muscles of 

 the anterior intervalvula, there being no muscles inserted on the 

 valvulae that directly oppose the opening muscles. The muscles of 

 the anterior intervalvula include the slender retractor muscles (fig. 

 17 C, D, 24/) arising anteriorly on the eighth sternum (fig. 13), and 

 a pair of short, broad muscles (fig. 17 C, D, ^7j) arising on the ovi- 

 positor apodemes. Since the anterior intervalvula lies between the 

 l:)ases of the dorsal and ventral valvulae, a pull on its muscles brings 

 the valvulae together. These same muscles also eflfect an adduction 

 of the valvulae of opposite sides. 



Transverse movements of the valvulae, i. e., movements of abduc- 

 tion and adduction, are not as pronounced as the dorsal and ventral 

 movements, but it can be shown experimentally on a dead specimen 

 that some of the muscles of the ovipositor separate or approximate the 

 valvulae of opposite sides. The only muscles that may serve as ab- 

 ductors of the valvulae are the retractor muscles inserted on the lateral 

 basal margins of the third valvulae (fig. 17 C, 26^), which arise 

 laterally on the ninth tergum. The adductors are muscles of the inter- 

 valvulae ; a forward pressure on these sclerites brings the valvulae of 

 opposite sides together. The anterior intervalvular muscles comprise 

 the median pair of slender muscles (fig. 17 C, D, 24'j') arising an- 

 teriorly on the ninth sternum (fig. 13), and the lateral pair of wide 

 muscles (^/j) arising on the inner margins of the basal parts of the 

 lateral apodemes ; both pairs converge to their insertions on the small 

 median apodeme of the anterior intervalvula. The posterior inter- 

 valvular muscles consist of a single pair of muscles (B, C, 2^4) 

 arising on the bases of the lateral apodemes, and converging pos- 

 teriorly to their insertions on the posterior intervalvula (piv). There 



