The Problem of Orientation 87 



steadily, especially with the aid of a hand rest, above 

 the disk. A cabbage butterfly, Pieris rap<s, was held 

 facing the center of the disk and presenting its right 

 side to the light. Almost immediately the butterfly 

 attempted to turn toward the light, and by the ac- 

 tion of its legs caused the disk to rotate in the op- 

 posite direction. After a few rotations of the wheel 

 the butterfly was turned into the reverse position 

 so that its left side was exposed to the light. Within 

 a few seconds it began to turn the disk away from 

 the light as before. When replaced in its original 

 position the butterfly rotated the disk again toward 

 the left side. Several subsequent trials gave similar 

 results, and another specimen of the same species 

 responded in practically the same way as the one 

 described. 



"Experiments with Melitaa chalcedon gave results 

 very similar to those with the cabbage butterfly. 

 When the insect was held pointing obliquely away 

 from the light it would still turn the disk away 

 from the more illuminated side. When pointing 

 obliquely toward the light the butterfly would give 

 the same response. In every position except that 

 in which the body was parallel to the rays there 

 were efforts to turn toward the light, which resulted 

 in the rotation of the disk. If the insect was held 

 facing the light, rotary movements were set up as 

 a consequence of attempts at forward locomotion. 

 In many cases the disk would be rotated for several 

 minutes without cessation, and when the butterfly 



