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es 
AQUATIC INSECTS IN NEW YORK STATE 213 
I have not been able to determine as yet whether in relation 
to trout culture Aeschna is more disadvantageous than other. 
wise. It eats a few of the fry and it eats the food of the larger 
trout; but, on the other hand, it furnishes a moderate supply of 
food itself for the larger trout. 
Out in the proper foraging ground of the trout, burrowing 
shallowly under the silt of the bottom of the pond, are other 
dragon fly nymphs of the genus Gomphus, which would seem to 
be wholly detrimental. They feed voraciously on other insects 
of the bottom fauna, and, doubtless, on Chironomus larvae, 
while by their burrowing habits they seem to escape the trout 
altogether. 
5 Callibaetis sp.? 
These nymphs, like the preceding, were found in an advanced 
stage of digestion. That they were Callibaetis, however, was 
determinable from the structure of the jaws, the top of the 
thorax and the bases of the setae, which were preserved. Since 
no adult May flies were collected at the pond and no nymphs 
bred, what the species is could not be established. Cal- 
libaetis ferrugina was taken at the hatchery, and the 
nymphs may very well have belonged to this species.+ 
This is a large genus, peculiar to the new world. A. consider- 
able number of species are already described, and doubtless 
many more will yet be discovered. I have found the nymphs ex- 
ceedingly abundant in many small lakes and ponds. They are 
most abundant amid the shore vegetation, but wander out into 
deeper water, resting on the bottom, and darting rapidly from 
place to place. I think it likely that they will be found more 
important as the food of young fishes than of adults, because of 
their greater abundance in the shallower water. 
It is due to the occurrence of a new species! of Callibaetis in 
my campus pond at Lake Forest, where, with my students, I 
have watched it year by year, that I am able to give some facts 
respecting the genus, which have a bearing on its economic 
‘While this is going through the press there comes to my table a 
description of the nymph of this species with figures by Berry, in the 
American Naturalist, 1908. 87:29, 30. 
