REACTIONS TO LIGHT IN VANESSA ANTIOPA 



387 



Table 4 shows that four butterflies were tested, making 23 

 trials in all, and that in 12 of these there was no response, while 

 in 8 the butterflies turned toward the blackened eye, and in 3 

 toward the functional eye. 



The results recorded in these two tables show clearly that a 

 sudden increase of intensity tends to cause the butterflies to turn 

 sharply toward the functional eye and that a sudden decrease 

 tends to cause them to turn in the opposite direction. 



The reactions, as described above, upon a sudden change in 

 the intensity of the light are very puzzling until the behavior of 

 the individual animals is carefully examined. In one of the 

 butterflies, 10/8-c, whose reactions are given in table 3 and in 



TABLE 4 



Effect upon the angle of deflection of suddenly decreasing the illumination from I4OO 



mc. to 104 mc. 



figure 10, the angle of deflection did not change in three trials, 

 but in seven out of the other nine trials made, it increased, at 

 once, when the intensity was suddenly increased. Immediately 

 afterwards, however, as shown in figure 10, the organism turned 

 toward the gloiver, and deflected at a smaller angle with the rays of 

 light than it had before the intensity had been increased. In one 

 trial, though, at the sudden increase of intensity, it decreased 

 the angle, and deflected only slightly in the bean. In another 

 trial it increased the angle and went out of the beam. 



The behavior of this last animal gives, I think, the clue to 

 the explanation of the fact that when the intensity of the light is 

 suddenly changed the angle of deflection decreases in some ani- 

 mals, while in others it increases. The fact that this butterfly 



