DRAGONFLIES AND DAMSELFILIES IN PONDFISH CULTURE. 203 
Of course, the snails crawl about over these sponges, as well as over the alge. The 
nymphs probably took in the spicules while feeding on these insects and snails, for they 
would hardly eat the sponge itself. The Libellula nymphs had eaten a much smaller 
number of mayfly larve than those of Anax and were content with the Amphipod 
Hyalella, in place of crayfish. 
Twenty of these nymphs were taken from pond 7 D, June 23, 1916, while the others 
came from ponds 1, 2, and 3 D, at different dates in July and August. Pond 7 had been 
stocked in the spring with 75,000 small fry of the buffalofish; on July 1 these young 
fish had reached a length of 1 inch, and on July 15 specimens were taken an inch and a 
half long. Previous to June 23, on this basis of growth, the fish were small enough to 
be caught and eaten by the nymphs, if the latter had made the attempt. The entire 
absence of fish from the diet of these nymphs shows that they chose other food even 
when fish were present. The remains of odonate nymphs in so many of their gizzards 
is good evidence, on the other hand, that the /uctuosa nymph is not inert and lethargic. 
The food of the Erythemis nymphs consists also of snails and entomostraca, with 
a moderate amount of beetle and mayfly larve, and an almost complete absence of the 
larger crustacea and of damselfly nymphs. A large amount of alge was present in 64 
per cent of the gizzards, and in several individuals nothing else had been eaten; at least, 
there were no remains in either gizzard or intestines. Alge, therefore, must constitute 
a respectable portion of the food of these nymphs. 
It might seem strange to report Simulid larve from a fishpond, but the screens at 
the outlets of all of the ponds were covered with the larve of Simuliwm vitiatum, and 
some of the nymphs evidently picked them off the screens. The ephippium surrounding 
the Cladoceran egg is proof against the digestive juices of the nymphs, and eggs taken 
from the posterior end of the intestines were as plump and uninjured as those just 
swallowed. The Desmids and Diatoms, like those found in /uctuosa nymphs, are not 
numerous enough to make it certain that they were really sought for and eaten. They 
might well have been taken in accidentally with some of the food. ‘Ten of these nymphs 
were taken from pond 7 D on June 26, 1916, and 15 were taken from pond 9 D on July 7. 
As already stated, the former pond contained an abundance of small fish, while the 
channel cats in the latter pond had produced a brood of fry previous to the capture of 
the nymphs. None of them had eaten fish, however, and their small size makes it 
improbable that they could overpower any but the smallest fry. 
Entomostraca and copepods are the chief articles of diet for the Pachydiplax nymphs, 
and there is a minimum amount of snails, beetle larve, and mayfly larve. The larger 
crustacea are practically absent, and damselfly nymphs are the only odonates repre- 
sented. ‘The food in the gizzards of these nymphs and that in the Erythemis nymphs 
was particularly well ground up, so that only small fragments were left. Even the 
shells of the small entomostraca were broken and resembled the débris obtained from 
the posterior intestine of Anax and Libellula. 
The damselfly nymphs included species of Enallagma, Ischnura, Argia, and Lestes, 
and were obtained from the various ponds indiscriminately. No attempt was made to 
separate the different species, and they were treated as though all one kind. The 
food in the gizzards of these numphs was broken up into smaller fragments than that 
of any of the dragonflies, and in much of it the identification of species or even genera 
was almost impossible. As will be seen the great bulk of the food consisted of ento- 
