38 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 89 



The shaft is composed generally of two pairs of bladelike processes, 

 the first and second valvidae (fig. 9, iVl, 2VI). The basal mechanism 

 consists essentially of four lobes or plates, the first and second valvifers 

 {iVlf, 2Vlf), associated with the eighth and ninth segments of the 

 abdomen, together with their connected muscles. The accessory lobes, 

 or third valvidae (3VI), are borne at the posterior ends of the second 

 valvifers. In some insects the basal structure of the ovipositor includes 

 median sclerites lying between the second valvifers, known as the inter- 

 valvulae, and also muscles inserted on these sclerites. The first and 



\ 

 \ 



Ode iVlf vinstn 2Vir 



Fig. 9. — Diagram of the basic structure of the pterygote ovipositor. 



Each gonopod consists of a basal plate, or valvifer (iVlf, 2VIJ), and a gona- 

 pophysis, or valvula {iVl, 2V I) ; each valvifer provided with muscles arising 

 on the tergum of its segment ; the basis of second gonopod produced distally in 

 a free lobe, the third valvula {3VI) ; gonopore {Gpr) at base of ovipositor 

 above eighth sternum. 



second valvulae arise from the anterior ends of the first and second 

 valvifers, respectively. The third valvulae, arising from the posterior 

 ends of the second valvifers, are usually free lobes, but in most Or- 

 thoptera they form a third pair of blades in the shaft of the ovipositor. 

 The first valvifers in the Hemiptera are closely associated with the 

 lower margins of the eighth tergum, though they are united by mesal 

 extensions with the ninth tergum ; in Orthoptera and Hymenoptera 

 they become more or less displaced posteriorly, and articulated with 

 the ninth tergum, or with the second valvifers. The second valvifers 

 are always associated with the ninth tergum. The dorsal muscles of 

 the first valvifers, regardless of the position of the plates themselves. 



