488 



ALFRED O. GROSS 



TABLE 1 

 Reactions of Calliphora adult to single monochromatic lights 



NUMBER OF REACTIONS 



blue. . . 

 green, 

 yellow 

 red 



Positive 



113 

 110 

 150 

 106 



Negative 



PERCENTAGE OF 

 POSITIVE REACTIONS 



9 

 26 



99 

 96 

 94 

 80 



the colors is corroborated by the results of further experiments, 

 to*be described later, on the adult blow-flies with balanced lights 

 of different colors. 



Flies were next tested in the cylinder illuminated by paired 

 lights of the same color and same intensity. About 100 flies 

 used in each of four such pairs were found to be distributed to 

 the two sides as shown in table 2. Theoretically the distribution 

 ratio of the responses of the flies to balanced lights of the same 

 colors should be 50 % : 50 %, but when comparatively small 

 numbers are used slight deviations, as in the above results, may 

 be expected. The percentages, however, even with these limited 

 number of trials, vary only from one to three units from the 

 expected ratio and show the degree of reliability one may place 

 on the records of the reactions of the adult flies to balanced lights. 

 With each new set of trials with any pair of colors the direction 

 of the rays was reversed to eliminate from the results any errors 

 which might arise from defects in the apparatus. 



TABLE 2 



Reactions of Calliphora adult to pairs of monochromatic lights of the same quality 



and of equal intensity 



