288 Annals Entomological Society of America [Vol. V, 
RESPONSES TO DAYLIGHT. 
Daylight was used as the source of stimulation for a large 
series of experiments. Many observations were recorded upon 
a great many different dragon-fly nymphs. In general it may 
be said that there was no evidence of orientation to the direction 
of the rays, and there seemed to be little indication of response 
to the light intensity, and the light was certainly brighter at the 
opening into the dark room than it was some distance away, 
within the dark room. The animals seemed to be generally 
indifferent to the light. At times, a few organisms indicated a 
tendency toward the positive reaction, but such facts are not 
uncommon in any experiments with light. Unless the dragon- 
fly nymphs are nothing more than reflex machines, it is to be 
expected that there will be some physiological variation in the 
internal condition of the different individuals even under the 
effect of the same stimuli. There are usually a few animals 
which appear to vary in their responses from the majority at 
any given time. 
SUMMARY AND CONCLUSION. 
The Agrionid nymphs discussed in this paper were col- 
lected in the vicinity of Ann Arbor, Michigan. In their natural 
habitat they respond strongly to contact. They are fre- 
quently found clinging to Elodea and Ceratophyllum, and are 
generally in close contact with these plants. They are also 
found in the angles formed by the various parts of the plants. 
The nymphs are obscured in such positions because of certain 
resemblances in color and form between themselves and the 
plants to which they cling. These factors are probably pro- 
tective, as is the death-feigning instinct which 1s so well devel- 
oped in these insects. In the vicinity of Ann Arbor, Michigan, 
Agrionid nymphs were taken in abundance in still waters, at 
varying depths from 10—80 cm. They are not generally 
found in bright light, but are more abundant in habitats shaded 
by aquatic vegetation and treés. The fact that they inhabit 
such situations 1s probably due to their negative response to 
strong light and to their positive response to contact. Two 
common enemies of these dragon-fly nymphs are the two 
species of fishes Lepomis gibbosus and Perca flavescens. The 
aquatic bugs Ranatra and Belostoma destroy large numbers of 
nymphs, when kept in confinement. Agrionid nymphs are 
