36 Annals Entomological Society of America [Vol. V, 
When it was brought near the stone again, it would at first 
swim toward it, but as soon as the heat was felt it would again 
turn and swim away. Some of the forms, upon coming in 
contact with the hot rock, would suddenly dart off, make a 
little circuit, and then return. This was repeated several times, 
the circuit becoming more and more extended until finally the 
nymph would no longer return to the stone. Still others would 
leap from place to place on the rock as though in search of a 
cool spot, some finally deciding to leave the stone, while others 
would quietly settle down and like the large majority of them, 
would cling to the stone until overcome by the heat. 
While working on the food reactions, I came across a speci- 
men that showed an exceptionally strong thigmotactic propen- 
sity. When it was placed in a separate dish of water it swam 
about very much animated, and after intervals of rest, its 
vigorous activity was again resumed. When a stone was placed 
in the dish the nymph eagerly attached itself and remained 
perfectly quiet, but when the stone was taken out and a small 
piece of alga was placed in the dish, the insect would come up 
to it, attach itself, and then quickly swim away again. The 
soft consistency of the plant evidently did not appeal to it. 
The circus movements were repeated every time I appeared 
near the dish. Not until after five days of fasting did the nymph 
attach itself to the morsel of food, to which it clung so firmly 
that its body became a complete ring. Then it commenced 
to feed on the ball of food it held so tightly in its claws. The 
smaller the piece of alga became the more tightly the specimen 
seemed to cling to it. Finally when only a small part of the 
food was left, the nymph discontinued feeding but still clung to 
the small particle. Thinking that this was probably due to the 
chemical stimulus of the plant, I took it away and gave the 
nymph a tiny pebble about the size of an ordinary sweet pea. 
The pebble was eagerly accepted but being much too small to 
afford normal attachment, the nymph coiled itself around the 
pebble and thus brought as much of its body in contact with it 
as possible. It continued encircling the pebble for six days 
when I noticed that it was about to moult. This was a difficult 
task, and although the pebble was cast aside during the attempt 
to get out of the old skin, the specimen now retained its ringlike 
shape. As the nymph was unable to moult in that condition, 
the old integument was carefully torn off, but the unfortunate 
