ANNALS 



OF 



The Entomological Society of America 



Volume IV J U N E , 1 9 I 1 Number 2 



MAY-FLIES OF FALL CREEK. 



By Anna H. Morgan. 

 Limnological Department, Cornell University. 



The following paper is a preliminary study of the ecology 

 of the May-flies in the streams about Ithaca, N. Y., more 

 especially in Fall Creek. In these, as in most fresh water streams, 

 the nymphs of this order are abundant. In Fall Creek they 

 are the dominant insects of the stream during the months of 

 {April, May and June, and by their fine adaptations to diverse 

 environments they offer a satisfying field of study to any brook 

 traveler. The nymphs may be easily secured, but only imagoes 

 exist in most collections, and these usually as dried distorted 

 specimens whose life-histories are little known. The winged 

 or aerial life lasts but a few days at most; the nymphal or 

 aquatic life may extend over two or three years. The imago 

 exhibits great specialization of parts concerned with reproduct- 

 ion and more striking atrophy of other parts than may be seen 

 any where else among insects. Imagoes of all the groups are 

 remarkably alike in superficial appearance. The nymphs, on 

 the other hand, display a series of adaptations as diverse as 

 their environments. Only by rearing specimens from nymphal 

 to adult life may these two stages be linked together. Many of 

 the life-histories of those species found in Eastern North 

 America have been made known. It has been with the hope 

 of adding to the number of these life-histories, as well as with 

 the purpose of gaining more knowledge of the habits of those 

 already known, that this study has been begun. The earlier 

 American workers, Say, Hagen and Walsh* scarcely took up 



* Walsh, B. D. On the pupa o£ the Ephemerinous genus Baetisca Walsh. 

 Proceed, of the Ent. Soc. of Philadelphia. 1864. pp. 200-206. 



* Walsh, D. B. List of the Pseudoneuroptera of Illinois. Proceedings of the 

 Natural Sciences of Philadelphia. 1862. 



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