MAY FLIES AND MIDGES OF NEW YORK 17 



dd No closed cell in tlie first fork of the radial 

 sector before the base of the second divi- 

 sion of the sector (pl.3, fig.3); coxae of 

 fore legs shorter than femora 



Palmobius u. gen. type H. amiculus Fitch 

 CO First of the three or four divisions of the radial 

 sector arising well beyond the basal sub- 

 costal crossvein (pl.2, fig.l); in the hind 

 v^ing vein M1+2 is more or less confluent 

 with the base of the radial sector, elimi- 

 nating or reducing the crossvein be- 

 tween Hemerobius 



EPHEMERIDAE 



BY JAMES G. NEEDHAM 



Since the publication of Museum Bulletin 47 little attention 

 lias been given by the workers at the Entomologic Field Station 

 to the collection and rearing of mayflies. Incidentally, however, 

 a number of new and most interesting forms have been brought 

 together, and nine additional species representing as many addi- 

 tional genera have been reared — ^mostly by Mr Betten and myself 

 during the summer of 1901 at Ithaca. It is the purpose of this 

 paper to give the results of new life history studies, and also new 

 keys for both adults and nymphs, that shall serve as a better 

 introduction to the study of this interesting group. 



That the group is of great economic importance in water culture 

 there can be no doubt. Past food studies have demonstrated 

 this; and every aquatic collector has found the waters teeming 

 with the immature stages. There are mayfly nymphs for every 

 Kort of situation in fresh water, and they are almost everywhere 

 abundant. These are perhaps the dominant insect herbivores of 

 fresh water. Notwithstanding their ecological interest, the vv^on- 

 derful ways in which they have adapted themselves to diverse 

 modes of life in different sorts of places, and their singular, 

 though fragile, beauty, their study is very much neglected among 

 us. It is in the hope of interesting more of our field workers in 

 them that I have added to the life histories and descriptions, 

 the keys and text figures of the present paper. 



Few life histories of American species, whose nymphs have been 

 positively determined by rearing, have as yet been written. The 

 singular nymph of Baetisca obesa Say has long been 



