REACTIONS TO LIGHT IN VANESSA ANTIOPA 371 



BEHAVIOR OF SPECIMENS WITH BUT ONE FUNCTIONAL EYE 

 A. BEHAVIOR IN NORMAL CONDITIONS OF ILLUMINATION 



In normal conditions of illumination the behavior of butter- 

 flies with but one functional eye was very different from that 

 described above. Such specimens were tested on the floor of 

 the cage referred to previously, on a table before a window, and 

 in a beam of light in the dark room. Before a window and on 

 the floor of the cage it was found that whenever they moved 

 they turned continuously toward the functional eye, exhibiting 

 behavior similar to that described by Parker. The periods of 

 activity, which in some cases lasted for several minutes, alter- 

 nated with periods of rest in which the animals remained practi- 

 cally motionless, as if recovering from fatigue. But the point 

 that is of especial interest is that they continued to make circus 

 movements from day to day, and that they did not learn to orient. 

 Two insects with one eye blackened were kept for twenty-three 

 days, and although they were observed many times each day no 

 modification in their behavior was detected. In this respect, 

 however, the reactions in a beam of light differed greatly. 



B. BEHAVIOR IN A BEAM OF LIGHT 



1. Description of reactions — deflection, circus movements, and 



orientation 



Under the conditions of illumination described in the preced- 

 ing paragraph, the animal receives light from all sides, and all 

 the large areas of the functional eye are approximately equally 

 illuminated in every position assumed by the insect. When 

 exposed to the light in a beam the animal receives light from 

 only one direction, and consequently every movement that is 

 not directed toward the glower produces a change in the illumi- 

 nation of different large areas of the uncovered eye. This may 

 account for the difference in behavior observed under the two 

 conditions of illumination. 



The behavior in a beam of light of Vanessa with one eye 

 blackened was studied in 46 different individuals and many of 



