DIGESTIVE SYSTEM OF PERIODICAL CICADA. 



region in the 14 mm. nymph, the same organs are found as 

 before, but there is slightly less complication in the way of 

 folding and intertwining than is found in the later stages. Fig- 

 ures 7 and 8 represent transverse sections through the anterior 

 region of the digestive organs of a 2^ mm. nymph. Here again 

 the various organs are seen to have assumed a position similar to 

 that in which they are found in the later nymphs and adult. 

 The peculiar relation of anterior crop, intestine, and malphigian 

 tubules is, therefore, established in all these nymph stages the 

 same as in the adult. In seeking the origin and significance of 

 this arrangement, it is necessary, then, to go back to the develop- 

 ment of the embryo within the egg. 



In Figs, i and 2 the malphigian tubules have not been repre- 

 sented. They are present in the same number and arrangement 

 as in the adult. They have been left out of the above figures 

 since they only tend to obscure the clear representation of the 

 digestive organs. 



The function of the posterior crop as an accessory storage 

 organ seems, at first, to be indicated by a comparison of the 

 different stages here considered. Originally a tube of small 

 diameter, it increases in size until it exceeds any of the other 

 organs in capacity. I have never found any precipitate or 

 coagulum in the cavity of this organ, however, so that the mere 

 size of its lumen may not justify one in attributing a storage 

 function to it. 



In summarizing it may be said that from the observations upon 

 the four nymphal instars of the cicada it is evident that the 

 digestive organs show an arrangement which is similar in ground 

 plan with that of the adult and also it is similar in many respects 

 with that of other Homoptera which have been described. The 

 complication of digestive organs in the anterior region of the 

 insect is fully established in the earliest nymph and hence is 

 developed at a time previous to that represented in the material 

 here considered. The posterior crop loses its simple tubular 

 character and becomes saccular at some time after the 14 mm. 

 nymph stage. 



Since the foregoing part of this paper was written, the paper 

 by Snodgrass dealing with the anatomy of the cicada has come 

 to hand. In this publication the large vesicular organ which 



