THE DIGESTIVE SYSTEM OF THE PERIODICAL 



CICADA, TIBICEN SEPTENDECIM LINN. 



III. MORPHOLOGY OF THE SYSTEM IN 



THE NYMPH. 



L. M. HICKERNELL, 



SYRACUSE UNIVERSITY. 



In an earlier paper, the form and relationships of the various 

 parts of the digestive system of the adult cicada were considered. 

 It was found that in both sexes the system is complete and well 

 organized but much complicated by a winding and twisting 

 together of its parts, so that the continuity of the system could 

 be established only with some difficulty. The intertwining in- 

 testine, esophagus, and malphigian tubules in the anterior part 

 of the body cavity makes the "internal gland" or filter which 

 seems to be characteristic of so many of the Homoptera. This 

 structure, while different in some respects in the cicada from that 

 described in other homopterous forms, has a general arrangement 

 which is similar. 



It was found further that certain organs of the digestive system 

 change shape markedly, as the insect increases in age, but that 

 the ground plan of the alimentary tract remains the same through- 

 out the life of the insect and that the system does not degenerate 

 or become broken as has been believed by certain workers. 



Because of the numerous peculiarities which were found in the 

 adult digestive organs, it seemed worth while to examine the 

 nymphal stages with the object of determining what conditions 

 exist there and also to determine, if possible, the origin of some 

 of the peculiar structural relationships. For, although the peculi- 

 arities of the homopteran digestive tube have been recognized 

 for some time, the beginnings of these peculiarities in embryo- 

 logical history have not been figured or explained in many cases. 

 It can at least be established whether the peculiar windings of 

 the digestive organs arise at the time of one of the numerous 

 moults or are to be traced back to the egg itself. 



The consideration of the morphology of the digestive organs 

 of the Homoptera dates back to the work of Lubbock, Leydig, 



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