NO. O INSECT ABDOMEN SNODGRASS 95 



Magicicada there is a tubular extension from the sac that proceeds 

 in the direction of the stomach, but the writer beheves it goes into 

 the filter chamber and not into the stomach lumen, though the facts 

 could not be more closely investigated for the lack of fresh material. 

 However, the anatomical incongruity of having a diverticulum of the 

 stomach opening to the exterior through a pair of spiracles suggests 

 a human error rather than a lapse of nature. 



Most of the visceral organs of the cicada's abdomen, except the 

 stomach, which lies anteriorly, are crowded into the rear part of the 

 abdomen by the posterior extension of the air chamber, which ends in 

 the seventh segment. The turgid form of the middle part of the 

 abdomen (fig. 30 A), therefore, presents the shape of the air sac. 

 The region between the second and the eighth segments contains a 

 succession of regular tergal and sternal plates. The lateral edges of 

 the terga are inflected to meet the sterna, which are pleurosternal 

 plates, there being no intervening pleurites or other lateral sclerites. 

 In the adult, the spiracles of these segments are contained in small 

 peritremal sclerites united with the anterior lateral angles of the 

 sterna ; in the nymph the spiracles have the same position but they lie 

 in membranous areas between the tergal and sternal plates (figs. 11 A, 

 30D). 



The tergum of the seventh segment does not differ from the terga 

 preceding it. The seventh sternum (fig. 30 A, VIIS), however, is 

 shortened, but its deeply emarginate posterior edge underlaps the base 

 of the ovipositor (Ovp). Above the seventh sternum is a small ves- 

 tibular cavity (fig. 32 A, Vst), in the anterior wall of which is a large 

 genital opening (a) above a small fold (VlllStn), which is the pos- 

 terior lip of the otherwise invaginated eighth sternum. The genital 

 aperture may be exposed by depressing the seventh sternum, or by 

 pulling the latter forward (fig. 31 A, a). It leads into a large copula- 

 tory pouch (GC), which, as will be shown later, is the true genital 

 chamber. 



The eighth segment is exposed dorsally but its ventral parts are 

 normally concealed within the seventh segment. The tergum is de- 

 clivous behind the seventh tergum (fig. 30 A, VIIIT) ; its lateral 

 parts are narrowed and are widely separated from the sternal region 

 of its segment. The anterior end of the eighth sternum appears as 

 a small fold beneath the opening of the genital chamber (figs. 31 A, 

 32 A, VlllStn), but most of the sternal plate is reflected anteriorly 

 upon the floor of the chamber (fig. 32 B, VlllStn) and is therefore 

 concealed within the latter. The exposed anterior (anatomically pos- 

 terior) end of the eighth sternum is connected by membranous folds 



