386 



WILLIAM L. DOLLEY, JR. 



of the light. This conclusion receives still further support from 

 the results obtained in non-directive light which are reserved for 

 discussion later. Before entering upon further discussion based 

 on table 2 we will describe experiments as to the effect upon 

 behavior of changes of intensity. 



b. Effect of sudden changes of intensity on the angle of deflection. 

 The previous experiment in which the position of the glower was 

 unchanged, but in which the intensity of the light varied in 

 different trials was supplemented by others. In some of these 

 the light was increased after the butterflies had oriented. In 

 others it was suddenly decreased. The insects with only one 

 eye functional were placed in a beam of light, and, as soon as 



TABLE 3 



Effect upon the angle of deflection of suddenly increasing the illumination from 104 



mc. to 1400 mc. 



they had assumed a definite direction of locomotion, the glower 

 was suddenly moved closer to the organisms, or was suddenly 

 moved further away. In this way the intensity of the light was 

 suddenly changed from 104 mc. to 1400 mc. and vice versa. 

 Some butterflies turned suddenly toward the functional eye, 

 others turned toward the blinded eye, and still others did not 

 respond. The reactions of the animals to sudden increase of 

 intensity are given in table 3; those to a sudden decrease of 

 intensity in table 4. 



Table 3 shows that in 21 out of 41 trials, the insects immedi- 

 ately turned toward the functional eye when the light was sud- 

 denly increased; that in 4 they turned toward the blinded side; 

 and that in 15 there was no response. 



