41 8 NEW YORK STATE MUSEUM 



consisting of single, isolated filaments.^ This subfamily includes the two 

 tribes, Capnini and Nemourini of Banks. 



Order ephemerida 



May flies 

 Family ephemeridae 



The May flies are all aquatic. K few of the larger species, which sud- 

 denly appear in countless numbers on the shores of our larger bodies of 

 water and as suddenly disappear again, are very well known. But most 

 May flies, being less concerted in their period of adult life, emerging a 

 few at a time, resting under cover and returning to the water in the 

 twilight to oviposit, are little observed. 



The nymphs live in all sorts of fresh water, and are almost everywhere 

 abundant. They are differentiated into highly specialized groups, each 

 finely adapted to its own peculiar situation. There is great apparent 

 similarity among the imagos ; but the nymphs of the several principal 

 groups are strikingly unlike. The struggle for existence has fallen mainly 

 on the nymphs, and they have specialized for themselves, more or less 

 independently of adult Ufe. On this account, the beginner will find the 

 study of the group greatly facilitated by collecting the nymphs along with 

 the adults. 



Nathan Banks has twice published keys for the determination of the 

 genera of our North American May fly imagos, in the Transactio7is of the 

 American entomological society^ 19:332 and 26:246-47. Nearly all our 

 species are described in Eaton's monograph.^ The following table will 

 serve for the separation of the nymphs of the genera occurring in our 

 fauna. It will also serve to indicate what I believe to be the three 

 principal natural divisions of the family, corroborated by important 

 characters pertaining to both adult and nymphal life. It is based in 

 part on the figures and tables of Pictet^ , Vaysseire* , Eaton^ , and 

 Schiller ^, but mainly on my own breedings of New York May flies. So 

 few species have as yet been reared that this table will doubtless need 

 considerable revision when more of the nymphs are known. 



1 Rarely developed. They are known from the European Nemoura cinerea Oliv., in which 

 species there are six separate filaments at the front end of the prothorax beneath. An undetermined 

 species of Nemoura, bred by me at Ithaca N. Y. possessed no gills whatever. I also bred at 

 Ithaca an undetermined species of Taeniopteryx the nymph of which had attached to the 

 posterior side of each coxa a single, tapering, three jointed, telescopic, gill filament. 



In the Perlinae, the number of filaments in a tuft often increases with the age and size of the 

 nymph. 



2 Eaton. Revisional monograph of recent Ephemerlnae. Linn. soc. Lond. Trans. (2) 3, 1888. 



3 Pictet. Histoire naturelle des neuropteres : Ephemer. Paris 1845. 



4 Vaysseire. Organization des larves des Ephemerines. Sci. nat. zool. Ann. (6) 11, 1881. 



5 Schiller. Die Ephemeriden-larven Sachsens. Sitz, u. abh. der. naturwiss. ges. Isis in Dresden. 

 1890. p. 44-49, 2 pi. 



