HELIOTROPISM OF ANIMALS 71 
plate, they do not again leave it, and now creep toward the 
window also. The animals are forced to bring the surfaces 
of their bodies as much as possible in contact with other solid 
bodies. 
These phenomena are not altered when the plate is cov- 
ered with blue glass. If, however, it is covered with red 
glass, the animals, even when in the middle of the plate, 
move as frequently toward the window as toward the room 
side. So far as the stereotropism of these animals is con- 
cerned, it must be added that the animals collect in the con- 
cave edges of dark boxes. 
It might be supposed that the function of stereotropism 
is to protect the bodies of the animals from evaporation as 
far as possible. I covered one-half of the bottom of a box 
with a moist cloth and the other with a dry one, and, after 
putting fifty animals in each half of the box, I placed it in 
the dark. After two hours not a single animal was found 
in the moist half of the box. The animals flee from moisture 
and seek dry spots. Contact-irritability and negative heliot- 
ropism determine the habits of these animals, which live 
protected from the light, in flour. 
The negative heliotropism of the larvee of June bugs.— 
The behavior of the larve of Melolontha vulgaris is quite 
similar to that of Tenebrio molitor. As they move for the 
most part while lying on their sides, their orientation takes 
place rather slowly ; nor do they follow in the direction of the 
rays of light as sharply as do the animals which have 
been described above. They flee from the light and move 
from the window to the room side of a vessel. 
The following experiment, which also serves to give an 
idea of the time required for experiments on these animals, 
shows that only the more refrangible rays are of chief 
importance in bringing about the heliotropic phenomena: 
At 10:40 o’clock I placed twenty-three larvae in the middle 
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