HELIOTROPISM or 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 larvce of June bugs. 

 The behavior of the larvse 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 larvse in the middle 



