214 NEW YORK STATE MUSETJM 



status. The nymphs are associated with Corethra larvae, and, 

 like them, are generally in excessive abundance at all seasons of 

 the year. Unlike the better known May flies, this species ha» 

 no single period of transformation; but imagos may be found 

 beside the pond most of the time from April till September. 

 There are, to be sure, as with Corethra, a larger number in evi- 

 dence at the beginning of their season, about the middle of May, 

 than at any time thereafter, but that, I think^ is due to the cold 

 weather retarding the process of transformation more than it 

 retards growth. I have found the imagos quite abundant in 

 September. This repetition and overlapping of generations 

 makes for continuity of food supply in the water. 



The nymphs at transformation climb up only to the surface on 

 some support, and then leave their cast skins floating on the 

 water. The subimago stage lasts about 24 hours and is spent, 

 as is usual, inactively. The male imagos are much in evidence, 

 flying in little flocks in sheltered places in the sunshine, weaving 

 up and down in their peculiar, rapid, dancing flight, and scatter- 

 ing on the approach of a net and settling on the reeds so quickly 

 and sitting so quietly that they usually entirely disappear from 

 view. I have found it difficult to capture many specimens of this 

 species, even when they are abundant. Tlie females are very 

 seclusive. I have rarely found one flying with the males, or 

 been able to discover one resting on shore. They are frequently 

 seen floating on the surface of the pond, resting on the water 

 with wings outspread, in which manner, like many other species 

 of May flies, they deposit their eggs. 



I append a description of this species in both adult and 

 nymphal stages. The accompanying figures will suffice for the 

 recognition of the genus. The adults of the genus are recogniz- 

 able by the costal band of brown on the wings, best marked in 

 the female, and the generic characters of the nymphs are stated 

 in the table for the genera of May fly nymphs given in bulletin 

 47 on page 419. 



