NO. 8 



INSECT ABDOMEN — SNODGRASS 



29 



The gonopods, or appendages of the eighth and ninth abdominal 

 segments, differ in' female Thysanura from the appendages of the 

 pregenital segments in that they lack eversible vesicles, and that each 

 is provided with a long genital process, or gonapophysis (fig. 6 B, C, 

 iGon, 2Gon). The basal plates of each segmental pair of gonopods 

 also are not united with each other. The gonapophysis is a slender 

 hollow extension from the dorsal aspect of the median proximal angle 

 of the basis of the gonopod (fig. 7). Its sclerotic wall is continuous 



VUI IX X XI 



Fig. 6. — The ovipositor and terminal structures of female Thysanura. 



A, abdomen of MachiUs, showing the styli {Sty) in position in life. 



B, C, genital segments of MachiUs, showing gonapophyses (Gon) arising from 

 limb base plates (LB). 



D, bases of caudal filament (cf) and cercus (Cer) of MachiUs, with muscles 

 of tenth segment. 



E, genital segments and base of ovipositor of Thcnnohia, ventral view. 



F, diagrammatic figure of the principal muscles of first gonopod of Thcnnohia. 



with that of the ventral plate of the basis, and the genital process 

 is thus not articulated with the latter, as in the stylus ; but, being 

 flexible at its base, the gonapophysis is movable, and it is provided 

 with short muscles (A, gmcl) arising on the basal plate mesad of 

 the longer muscles of the stylus (smcl). In some of the Thysanura, 

 as in N esomachilis (fig. 7), the four gonapophyses of the ovipositor 

 are individually free structures, except that those of the ninth seg- 

 ment (B) are united at their bases; in others, however, as in Ther- 

 mobia (fig. 6 E), the gonapophyses of the second pair are fused with 

 each other throughout the length of the ovipositor, and only those of 



