REACTIONS TO LIGHT IN VANESSA ANTIOPA 377 



meiit. This was followed by a zig-zag course nearly parallel 

 with the edge of the beam. This circus movement is worthy 

 of notice for it was made in the shaded region outside the beam, 

 when the animal was in very weak light. It should also be 

 noted that the diameter of the curve made is very nearly the same 

 as the diameter of the curve made in the beam in comparatively 

 strong light, when the insect was first started in this trial. This 

 peculiarity will be correlated later with the results of other experi- 

 ments. In the thirteenth trial after performing a circus move- 

 ment in the beam the organism continued to the right in a fairly 

 straight course to the edge of the table. In the fourteenth a 

 circus movement in the beam was made, and then the animal 

 went 7 cm. beyond the edge and oriented, moving toward the 

 glower. In the fifteenth it crossed the rays of light and made 

 a circus movement to the right of the beam. It then went toward 

 the glower in a fairly straight line, but before reaching the source 

 of light it made another circus movement. In the sixteenth a 

 circus movement was made to the right of the beam. This was 

 followed by a zig-zag course toward the glower. The behavior 

 in the succeeding eighteen trials was essentially similar to that 

 described above. It should be noted, however, that in the 

 twenty-fourth trial the butterfly after moving to the right until 

 the edge of the beam was reached turned more sharply toward 

 the functional eye at this point. It did not, however, perform 

 a circus movement, but gradually turned to the left. This sharp 

 turn toward the functional eye on reaching the edge of the beam 

 seems to support the conclusion arrived at from the trials on the* 

 previous day, namely, that change in illumination tends to favor 

 the performance of circus movements. 



These trials on the second day thus confirm strongly the con- 

 clusions drawn from the reactions on the first day, and they show 

 moreover that after a certain amount of experience the angle of 

 deflection tends to decrease, for on the first day the average 

 angle between the path of the butterflies and the rays of light 

 was 100 degrees while on the second day it was only 89.5 degrees. 



The reactions on the third day (fig. 4) differed very markedly 

 from those described for the first two days in several respects. 



THE JOCRNAI, OF EXPERIMENTAL ZOOLOGT, VOL. 20, NO. .3 



