240 Annals Entomological Society of America [Vol. XIII, 



VII. Summary and Conclusions. 



1. There is a well-differentiated and continuous digestive 



tube in both male and female adult Tibicen septendecim. 



2. The esophagus, which empties into the crop, shows no 



peculiarities of structure. 



3. The crop is divided into two unequal parts (the anterior 



and posterior crops) by a constriction at the place where 

 thorax and abdomen join. 



4. The crop is partially obscured by a mass made up of 



ascending intestine and malpighian vessels. This mass 

 has been called the "internal gland" (Lubbock '59). 

 .5. The posterior crop is greatly enlarged, especially in the 

 adult male, and its epithelium is extremely thin except 

 at the extreme anterior and posterior ends. 

 :6. The posterior crop empties into the ascending intestine 

 which is yellow in color and runs forward until 

 immediately dorsal to the anterior crop it winds about 

 with the malpighian vessels to make the "internal 

 gland." 



7. The ascending intestine emerges from the internal gland 



and empties into the descending intestine. 



8. The malpighian vessels are four in number and they empty 



into the digestive tube at the junction of ascending and 

 descending intestines. 

 '9. The descending intestine runs dorsally in a general posterior 

 direction until it joins the rectum. The former is 

 gray in color. 



10. There is no degeneration of parts of the digestive tube 



of either male or female in the sense that any part ceases 

 to be well organized or becomes disconnected from 

 another part. 



11. Nothing has been learned in connection with this study 



which throws any light upon the reasons for the peculiar 

 life history of the cicada. 



