276 Annals Entomological Society of America [Vol. V, 
Agrionid nymphs are found in quiet waters at a depth 
varying from 10-80 cm. deep. So they live in an environment 
where the light is dim, a sort of twilight, certainly not.a bright 
light. Then frequently there are reeds, sedges, cat-tails, pond- 
lilies, arrowheads, and other aquatic plants which form shadows, 
so modifying the action of the sun’s rays. It is not at all 
uncommon to find willows and alders shading the pools which 
serve as the living places for dragon-fly nymphs. The “‘selec- 
tion’’ of such a habitat is influenced, to a considerable extent, 
by the natural responses of the animals. They react negatively 
to bright light and respond positively to contact. The labor- 
atory experiments largely bear out these environmental obser- 
vations. 
ENEMIES. 
Before considering the reactions of Agrionid nymphs to 
photic stimuli, it seems worth while to discuss briefly their 
food and enemies. While no extensive notes were taken on 
either of these subjects, yet some observations were recorded 
which indicate that the facts discussed in the last three para- 
graphs have a more or less direct bearing upon the relations of 
the nymphs to their food and enemies. In the states of Michi- 
gan and Minnesota, the two gamy little fishes, the common 
sun-fish, Lepomis gibbosus, and the yellow perch, Perca flaves- 
cens, are very abundant. Both of these species have frequently 
been taken by the writer in considerably numbers. It was 
often noticed that among other insects, found in the digestive 
tract, Odonate nymphs were present and many of them were 
Agrionid nymphs. It is very likely that Agrionid nymphs 
form a large portion of the diet of many other species of 
fish. In fact, Forbes (1888, pp. 485-524) found that the 
nymphs of Odonata formed a very important article of food in 
the case of the following fish: the common perch, Perca flaves- 
cens, the pirate perch, Aphredoderus sayanus, the crappie, 
Pomoxis annularis, and the grass pickerel, Hsox vermiculatus. 
In the case of each of the three first named fishes, it was found 
that dragon-fly nymphs formed 10-13 per cent. of their food; 
and in the case of the grass pickerel, they formed 25 per cent. 
of the food. Needham (1898, p. 86) states that he has seen 
dragon-fly nymphs taken in numbers from the stomachs of the 
Great Blue and Green Herons. Aaron (Lamborn, 1890, p. 50) 
