1920] Hickernell: Digestive System of Cicada 229 



From what has been said it should be apparent that the 

 adult male cicada possesses a digestive tube which is most 

 peculiar both with respect to elements which compose it and to 

 the manner of their arrangement. It is possible to demonstrate 

 by dissections alone, that this insect has a complete and contin- 

 uous digestive tube yet this fact has been denied by many, and 

 even when admitted, the arrangement and connections of the 

 organs have been imperfectly understood. The relationships 

 of the various parts described must depend upon the study of 

 sections, for it will shortly appear that certain apparent con- 

 nections between elements as indicated in whole preparations 

 are indeed apparent and not real. 



RELATIONSHIPS OF THE DIGESTIVE ORGANS. 



As suggested above, the connection between the various 

 parts of the digestive system are not very clear in gross dis- 

 sections. The actual union of some of the different divisions 

 of the system can be clearly demonstrated only in sections. 



With the view of determining the true nature and relation- 

 ships of parts in the anterior part of the digestive tube, the 

 crop with the internal gland was dissected out of numerous adult 

 insects. Transverse, sagittal and frontal sections were cut, 

 and by means of these the independence of crop and internal 

 gland was established. A median sagittal section of the anterior 

 part of the tube shows that the esophagus is separated from 

 the crop by a valve and that the anterior crop then continues 

 in a posterior direction. As it proceeds, however, its walls 

 become much modified, the floor being greatly thickened, while 

 the roof is relatively thin and much folded. The folds in the 

 roof are very pronounced and run in a general antero-posterior 

 direction. This condition results in the formation of deep exter- 

 nal fissures on the dorsal surface of the anterior crop, the 

 ascending intestine and malpighian vessels each being enveloped 

 by the walls between two adjacent folds. These relationships 

 may be understood by reference to Fig. 9, which is a transverse 

 section through the anterior crop region. The same structures 

 are also represented diagramatically in Fig. 6. 



This modified anterior crop upon reaching the posterior 

 portion joins directly with the latter. The aperture leading 

 into the posterior crop is small and irregular by virtue of the 

 convoluted walls of the connecting portions. While the dorsal 



