REACTIONS OF ARTHROPODS TO LIGHTS 



505 



In the sets of pairs in which green and yellow are compared 

 with the other colors the percentages of negative responses in 

 each pair are practically equal. Thus the theoretical result when 

 yellow is balanced with yellow or green with green is 50 % : 50 %, 

 while the actual result is 53 % : 47 % and 49 % : 51.% for the 

 green and yellow combinations respectively. 



The percentages of responses when green-yellow and yellow- 

 green are opposed are 49 % : 51 % and 50 % : 50 % respec- 

 tively. These results indicate that yellow and green are practi- 

 cally equal in potency as far as their effectiveness in orienting 

 the cockroach is concerned. 



TABLE 15 



Percentages of reactions of Periplaneta to each of the four colors when compared 

 with red and with darkness 



The reactions of the cockroach to the pairs of colors in which 

 blue is balanced with green and yellow, the percentage of the 

 responses to the blue is not greater than when blue is used alone. 

 This result is somewhat inconsistent in view of the fact that the 

 cockroach is negative to the green and yellow and positive to 

 the blue. In using such pairs of lights one would naturally 

 expect a larger percentage of the cockroaches to go to the blue 

 than in the case when blue is used alone. 



In table 15 are shown the percentages of responses for the 

 pairs red or darkness with each of the colors. The results exhib- 

 ited in this table demonstrate that i?ed of an intensity and quality 

 used in these experiments, has no more effect than darkness in 

 stimulating the cockroach. 



The reactions of the cockroach to light are unique in that 

 they are positive to the blue, negative to the green and yellow 

 and indifferent to red. 



