EPHEMERIDA 313 



Comparatively few writers have made extended studies of the 

 classification of the ephemerids ; this is doubtless partly due to the fact 

 that pinned specimens usually become shriveled and are very fragile ; 

 consequently this order is poorly represented in most collections of 

 insects. In spite of this, more than one hundred species have been 

 described from the United States. An important paper on the 

 classification of May-flies is that by Dr. Needham ('05) in Bulletin 86 

 of the New York State Museum. Here are given keys for separating 

 the North American genera, one for the adult insects and one for 

 the naiads. 





