REACTIONS TO LIGHT IN VANESSA ANTIOPA 



383 



on the two sides of the body varies with the relative amount of 

 Hght energy received by the two retinas. No such relation, 

 however, was at all evident in the observations on Vanessa. 

 Curves of the same size were made in both positions, and very 

 frequently those in the region of low illumination outside the 

 beam were smaller than those in the region of comparatively 

 high illumination in the beam. This is well seen in the ninth 

 trial made by animal 10/14-b on the third day (fig. 8). In this 

 case the butterfly, while in the beam, began to perform a circus 

 movement of a diameter of 6.5 cm. By the time it was half 



Fig. 8 Reproduction of 21 successive trails made by butterfly 10/14-b (left 

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

 of light; 1-21, paths made in successive trials; small arrows, direction of move- 

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

 mc. ; at y, 250 mc. Note that in trial 9 this insect turned very much more sharply 

 toward the functional eye while in the shaded region to the right of the beam than 

 it did while in the comparatively strong light in the beam. 



completed the animal was 3 cm. beyond the edge, and in the 

 weak light to the right of it. On reaching this point, the insect 

 turned sharply to the right, and made another circus movement 

 of a diameter of only 1.5 cm. i.e., in weak light the organism 

 turned more sharply toward the functional eye than in strong. 

 Similar reactions were observed in many other cases. 



3. Relation between the angle of deflection and the luminous intensity 



a. Effect of beginning the trials in different intensities. It has 

 been shown that in those trials before the Nernst glower in which 

 circus movements are not performed continually, Vanessa antiopa 



