NO. 8 INSECT ABDOMEN SNODGRASS 9^ 



connections with the first valvulae, but since the second valvulae 

 are united at their bases with each other, the two inner blades of the 

 ovipositor, which are serrated on their dorsal margins (fig. 29 A, 

 2VI), must work in unison between the outer first valvulae. The first 

 valvulae also may have some independent movement produced by the 

 muscles of the first valvifers, but the writer has not observed the 

 cicadellid ovipositor in action on a living specimen. 



An interesting account of the structure of the valvulae in the 

 cicadellid ovipositor, and their relations to one another is given by 

 Balduf (1933). The anterior valvulae, however, are referred to the 

 " seventh sternite ", and the second or inner pair to the " eighth 

 sternite." This error probably arises from overlooking the true first 

 segment of the abdomen, which is partially united with the second, 

 though in no insect are the valvulae connected with the sternal 

 plates of their segments. 



MAGICICADA SEPTENDECIM (lINNAEUS) 



The well-developed ovipositor of the Cicadidae furnishes an easily 

 studied example of the structure of the ovipositor typical of the 

 Hemiptera. The 17-year cicada here described, however, has a curious 

 and unusual development of the genital chamber, which is provided 

 with a secondary posterior passage giving exit to the eggs directly into 

 the channel of the ovipositor. 



General structure of the abdomen. — There has been so much mis- 

 information given out on the subject of the abdomen of the cicada 

 that it will be permissible to devote a little more attention to the general 

 abdominal structure of this insect than would be necessary otherwise 

 in connection with a study of the ovipositor. 



The general form of the female abdomen in Magicicada septendeciut 

 is shown at A of figure 30. At its base the abdomen is broadly but 

 movably joined to the thorax, but the connecting parts are mostly 

 concealed by overlapping parts of the metathorax. When the thorax 

 and the abdomen are somewhat pulled apart, as shown at B of the 

 same figure, it is seen that there lies in the infolded membrane between 

 the metatergum (Ts) and the first abdominal tergum (IT) a well- 

 developed though narrow postnotal plate of the metathorax (PN3), 

 which bears the large third phragma, and is fused ventrally with the 

 metapleural epimera (Epm^) in the usual manner. On each side of 

 the dorsum the postnotum retains a flexible sclerotic connection (a) 

 with the first abdominal tergum. The latter (IT) is a narrow, trans- 

 verse plate united with the second tergum {I IT) ; its lateral part 



