510 



WILLIAM L. DOLLEY, JR. 



In experiment 2 five insects were tested in two illuminations. 

 In one illumination the intensity in the beam varied from 0.4 

 m.c. at one end of the table to 1.56 m.c. at the other. In the 

 other it varied from 1.56 m.c. to 1500 m.c. The results ob- 

 tained are presented in table 2. These results show that the 

 average rate of movement of the 5 butterflies in each of these 

 two fights was the same, being 2.16 cm. per second. They 

 therefore moved at about the same rate in both illuminations, one 

 nearly 1000 times stronger than the other. This indicates that 

 the rate of locomotion in Vanessa is within rather wide fimits 

 independent of the luminous intensity. 



TABLE 2 



Rate of locomotion of Vanessa antiopa in two illuminations, one from nearly 1000 

 to nearly 4 tim,es the other at the two ends oj a 300 cm. course 



The conclusion stated previously, that Vanessa usually moves 

 faster in weak fight than in strong light if the ifiuminations 

 differ by a certain amount, is supported by the results obtained 

 in the individual trials. The butterflies, as they moved toward 

 the source of fight, were being exposed to a gradually increasing 

 luminous intensity. They should therefore, according to the 

 ''continuous action theory," gradually increase their rate of 

 locomotion as they approached the source. That this was not 

 the case is shown in table 3 in which is given the average rate of 

 movement of each insect in each of the illuminations used in 

 experiments 1 and 2 in the first 75 cm. (nearest the source), the 

 middle 75 cm., and the last 75 cm., of the 300 cm. course. 



