April, 1922 EMERGENCE OF A MAYFLY 157 



similar to this is Needham's description of the emergence of 

 Caenis dimimita . "It emerges from the water at nightfall 

 leaving its nymphal skin floating on the surface, and, alighting 

 on the first support that offers, sheds its skin again. * * * " 

 In neither of the last two accounts is it definitely stated 

 whether the mayfly issued from its nymphal skin after reaching 

 the surface of the water or whether the process began before 

 that. In the case of Iron Jragilis with regard to which Miss 

 Morgan uses the phrase, "popped from the surface of the water," 

 it would appear that the shedding of the nymphal skin must 

 have occurred beneath the surface. The emergence I have 

 described, is, I believe, the only case on record in which such a 

 process has actually been observed. 



LITERATURE CITED 



Clemexs, W. a. — 



1915. Life Histories of Georgian Bay Ephemeridas of the Genus Heptagenia. 



Howard, W. E. — 



1905. Polymitarcys Albus Say. In Mayflies and Midges of New York, 

 New York State Museum Bulletin 86 (Entomology 23), p. 60. 



Morgan, Anna H. 



1911. Mayflies of Fall Creek. Annals Entomological Society of America, 

 Vol. 4, pp. 104, 116. 



Needham, James G. — 



1905. Mayflies and Midges of New York State. New York State Museum 



Bulletin 86 (Entomology 23), p. 35. 

 1908. Report of the Entomologic Field Station conducted at Old Forge, 



N. Y., in the Summer of 1905. New York State Museum Bulletin 



124 (Edu. Dept. Bull. 433), p. 178. 

 1918. Burrowing Mayflies of our Larger Lakes and Streams. Bulletin of 



the U. S. Bureau of Fisheries, Vol. 36, 1917-18, p. 280 (also Document 



No. 883, Bureau of Fisheries, 1920). 



