DRAGONFLIES! AND DAMSELFLIES IN PONDFISH CULTURE. 209 
fined to the warmer months, when they are present in greater numbers. The abundance 
of crustacea in the Fairport list will thus depend somewhat upon the fact that all the 
nymphs were examined during the months of July and August. 
ConcLusions.—Comparing the three food lists here presented from widely sepa- 
rated localities, it would seem that odonate nymphs eat very much the same food 
everywhere. They feed largely upon insects and are able to confine themselves practi- 
cally to a single species that happens to be abundant, as in Hawaii, or they may extend 
their diet to include a rich variety of genera and species, as in the other two lists. In 
her text notes Miss Lyon enumerates 11 species that could be identified amongst the 
Chironomid larve, with the probability that still others were represented in the 
unidentified material. 
Judging from the lists, odonate nymphs do not devour many mosquito larve or 
pupe, although Warren (1915) was firmly convinced that the Hawaiian nymph was a 
great destroyer of mosquitoes, in spite of the unfavorable showing of his list. He even 
fed some of his nymphs with mosquito larve and adults. One Pantala nymph ate 
during a single night 40 imagos of Stegomyia scutellaris that had been stunned with 
cyanide fumes and placed in the aquarium with the nymph. Another Pantala nymph 
ate 75 full-grown mosquito larve within 12 hours. But here, as in the eating of the 
fish, no convincing argument can be drawn from what is fed to a nymph when no other 
food is available. 
The food of the odonate nymphs is by no means confined to insects, however; 
they also eat quantities of crustacea and mollusks and may include protozoa, alge, 
and even vertebrates in their diet. In fact, the nymph seems capable of accommodating 
itself wonderfully well to its environment and can seemingly thrive upon whatever 
form of food happens to be available. Consequently if the nymphs are introduced 
into a fishpond, no special food will need to be provided for them. If the pond is 
stocked with the usual insect larve, crustacea, etc., whatever the species may be, the 
nymphs will quickly adapt themselves to them. 
ENEMIES OF ODONATE NYMPHS. 
1. Fisa.—A full discussion of nymphs as food for fishes is given on page 225. 
2. LARGER Nympus.—The proportion in which the smaller nymphs are destroyed 
by the larger ones is well shown in the table and statements already given. 
About 20 per cent of the food of Anax nymphs and 10 per cent of the food of the 
nymphs of L. luctuosa consist of other nymphs smaller than themselves. In general, 
the nymphs that are eaten belong to a different genus, but the large nymphs are can- 
nibalistic as well as rapacious and sometimes eat others of their own species. ‘This 
is not as likely to occur, because all the nymphs of a given species develop at about the 
same time and are consequently nearer the same size. But they always vary more or 
less in their rapidity of growth, so that some are larger than others, and even if two 
were of the same size it would not be safe to keep them together unless plenty of suitable 
food were provided for them. If they once became real hungry, they would fight it 
out and the stronger would devour the weaker. To protect themselves against one 
another, as well as against all their enemies, the Gomphid nymphs habitually burrow 
in the mud or débris of the bottom; L. Juctuosa and the heavier Libellulids sprawl 
