RATE OF LOCOMOTION IN VANESSA ANTIOPA 517 



When however the flash frequency of intermittent hght is 

 very rapid the effects of continuous hght and intermittent hght 

 upon the movement of Vanessa seem to be the same, while if 

 the frequency of interruption is very slow the butterflies seem 

 to move at a slower rate than they do in continuous light. This 

 conclusion is drawn from the data presented in table 6. As is 

 shown in this table, the average rate of all of the 8 insects tested 

 was exactly the same in intermittent light the frequency of 

 interruption of which was 22 per second as it was in continuous 

 light when the motor was running, thus showing that the inter- 

 ruption of the light had no effect on the rate of movement. 

 This table shows also that 7 out of the 8 butterflies moved more 

 slowly in intermittent hght of a flash frequency of 1 per second 

 than they did in continuous hght. That vibration from the 

 motor did not produce these results is indicated by the fact 

 that while 6 out of the 8 insects moved more slowly in continuous 

 light while the motor' ran than they did in continuous light while 

 the motor was not running, 7 moved slower in intermittent 

 light of low flash frequency than they did in continuous light 

 while the motor was running. 



That this increased rate of movement in intermittent light of 

 a certain frequency of interruption is not due to the fact that the 

 illumination was greater in the tests made in continuous light 

 than it w^as in those made in intermittent hght is shown by the 

 fact that Vanessa tends to move at about the same rate in con- 

 tinuous lights of different illuminations unless the difference 

 is much greater than was that between the continuous illumina- 

 tion and the intermittent illumination. Even in illuminations 

 differing by nearly 100,000 per cent this butterfly tends to move 

 at about the same rate, as is shown in table 2. Yet in none of 

 the tests in intermittent light did the illuminations differ by 

 more than 300 per cent. 



Consequently, the three experiments described in the preceding 

 paragraphs seem to show that Vanessa tends to move at a faster 

 rate in intermittent light of a frequency of interruption of. 10 

 and 16 per second than it does in continuous light, while it tends 

 to move at a slower rate in intermittent light of a flash frequency 



