100 Annals Entomological Society of America [Vol. IV, 



Ephemera simulans Walker. 



No representatives of this genus were collected previous to 

 June 14 when a female specimen was captured at large near 

 upper Fall Creek. From June 23 to 30 full grown nymphs 

 were found about two inches below the surface in a muddy 

 basin connected with the main stream. Near this place a 

 swarm of Ephemera consisting of three to four hundred indi- 

 viduals was dancing about fourteen feet in air at half past 

 seven o'clock in the evening of June 29th. Their steady rising 

 and falling continued over the same area as long as the light 

 kept them visible. One female captured from the swarm was 

 placed on the surface of water in the laboratory. She was 

 unable to fly and lay prone upon the surface. Immediately 

 the last four segments of the abdomen began to move spas- 

 modically and eggs poured forth from the oviducts. At the 

 end of one minute the abdomen was empty, and the glass 

 spread with a single layer of white, firmly adherent eggs, 

 easily distinguished with the naked eye. 



No Ephemera nymphs were found in the lower Creek up 

 to this time, that cleaner portion being nearly devoid of mud. 

 On the first of July, however, the water in Beebe Lake was 

 allowed to run off, bringing into the Lower Creek large quanti- 

 ties of mud. Three days later the shores below the dam were 

 again examined. Tracks similar to those made by earth-worms 

 covered the bottom near the shore-line. Nymphs were crawl- 

 ing over the surface and setae could be seen projecting from 

 many burrows. From an area of about ten square feet thirty 

 nymphs were removed. 



Heptageninae. 



Represented entirely by dwellers in rapid water,, this family 

 is the dominant one in number, and the most homogeneous in 

 nymphal form. It is represented here by four of its six North 

 American genera Heptagenia, Epeorus, Ecdyurus, and Iron, 

 given in order of their relative abundance. As a family the 

 Heptageninae has taken possession of the rapid, thoroughly 

 oxygenated water and the alga-covered stones of the middle 

 stream, apparently coming into the calmer waters only at 

 transformation time. In order to secure and keep this posi- 

 tion against the mechanical force of the water acting upon them 



