REACTIONS TO LIGHT IN VANESSA ANTIOPA 



381 



said to have oriented in the 'shaded region.' When orientation 

 occurred either precisely at the edge of the beam or within one 

 centimeter beyond the edge it is considered to have occurred 

 'near the edge of the beam.' In those trials in which the insect 

 either continued to perform circus movements or passed on out- 

 side the beam into the shaded region beyond, in a more or less 

 straight course with no turn toward the source of light, 'no 

 orientation' is said to have occurred. 



An examination of this table shows that out of a total of 3077 

 trials the butterflies turned toward the functional eye in 2699 

 trials, and away from it in 207 trials, while in 171 trials they 



Fig. 7 , Reproduction of 33 successive trails made by butterfly 10/14-b (left 

 eye blackened) on the first day of the tests, a and h, limits of horizontal beam 

 lof light; 1-33, paths made in successive trials; small arrows, direction of move- 

 |ment of animal; large arrows, direction of rays of light; illumination at x, 1510 

 ic; at y, 250 mc. Note that this insect modified its behavior in that it per- 

 formed circus movements in 13 out of the first 16 trials, but made circus move- 

 ments in only 6 of the next 16 trials. 



moved toward the glower without first turning toward one side 

 or the other. This indicates clearly that there is in Vanessa 

 with one eye blinded a strong tendency to turn toward the func- 

 tional eye. 



The table shows also that in 2399 of the 3077 trials individuals 

 with but one functional eye oriented and moved fairly directly 

 toward the light, and that in 287 trials orientation occurred in 

 the beam of light, indicating strongly that both eyes are not 

 necessary in this process. 



