REACTIONS TO LIGHT IN VANESSA ANTIOPA 373 



angle with the rays of hght, and then continued until they 

 reached the edge of the beam. Here they usually turned sharply 

 toward the glower and moved along the edge of the beam toward 

 the source of light (fig. 1, /) but occasionally they continued to 

 turn here and made circus movements (fig. 1, i), and sometimes 

 they did not respond at all when they reached the edge of the 

 beam, but continued until they had passed into the shaded region 

 from 2 to 5 cm. when they usually turned and proceeded directly 

 toward the glower, remaining in this region (fig. I, g). On a few 

 occasions, however, they did not turn when they reached the 

 edge of the beam, but proceeded on in the shaded region indefi- 

 nitely (fig. 1,' h). A few animals did not turn toward the func- 

 tional eye, but oriented fairly accurately and walked toward the 

 glower in a nearty straight course (fig. 1, k). Several specimens 

 in some trials turned toward the blackened eye, crossed the beam, 

 and on reaching the edge turned and walked along it toward the 

 source of light (fig. 1, j). 



Many insects, as the trials proceeded, showed an increase in 

 accuracy of orientation. This was evident in three respects: (1) 

 in the number of circus movements made, (2) in the angle of 

 deflection, and (3) in the promptness \^dth which they oriented 

 at the edge of the beam. 



The above general description msiy perhaps be made clearer 

 if the reactions of one organism are described in detail. This 

 animal designated as butterfly 10/25-a (left eye blackened) was 

 tested on three successive days. 



On the first day this butterfly was given twenty trials (fig. 2). 

 In every one it turned toward the unblackened eye immediately 

 upon being placed in the beam. In the first trial it crossed the 

 beam at an angle of approximately 95 degrees with the rays of 

 light, and passed into the shaded region. After it had ggne 6 

 cm. in this region it turned to the left (the blinded eye) and 

 walked toward the glower in a slightly zig-zag course, remaining, 

 however, in the comparative darkness to the right of the beam. 

 In the second trial, after crossing the beam at an angle of nearlj' 

 80 degrees, it again went to a point 6 cm. beyond the edge of the 

 beam, but then it turned sharply to the right (toward the func- 



