214 NEW YORK STATE MUSEUM 
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 has 
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 om 
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. The 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. 
