THE DIGESTIVE SYSTEM OF THE PERIODICAL 

 CICADA. II. PHYSIOLOGY OF THE ADULT 



INSECT. 



CHARLES W. HARGITT. 



The periodical cicada, now technically known as Tibicen 

 septendecim, is well characterized by Marlatt (Bulletin No. 71, 

 Bureau of Entomology, 1907, p. n) as "undoubtedly the most 

 anomalous and interesting of all the insects peculiar to the 

 American continent. This cicada is especially remarkable in 

 its adolescent period, the features of peculiar divergence from 

 other insects being its long subterranean life of thirteen or seven- 

 teen years, during all of which time its existence is unsuspected 

 and unindicated by any superficial sign, and the perfect regularity 

 with which at the end of these periods every generation, though 

 numbering millions of individuals, attains maturity at almost 

 the same moment." Dealing with these several peculiarities 

 and related problems of distribution, economic bearings, localized 

 broods, etc., a large literature has accumulated since its first 

 recorded advent at Plymouth, Mass., in 1623. But literature 

 concerned with the more technical problems of its life history, for 

 example, its embryology, morphology and physiology, is rela- 

 tively small in vol.ume and not of especially high value. Of 

 some three hundred titles cited by Marlatt in the above-men- 

 tioned bulletin, by far the most of them relate to matters of 

 habit, distribution, injuries caused, enemies, etc., and only an 

 occasional reference to the anatomical or physiological problems 

 concerned in its life. Much of this apparent indifference may be 

 attributed to the highly obscure character of the life history of 

 the insect, but not wholly so. For example, until the former 

 paper by Hickernell appeared, there seems not to have been any 

 critical account of the internal anatomy of any of the several 

 organ systems of the insect. Nor has particular attention been 

 directed to what must be rather unique physiological processes 

 in such an organism. It is the purpose in what follows to submit 

 an outline at least of the chief physiological observations which 



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