REACTIONS OF ARTHROPODS TO LIGHTS 



501 



A moth allowed to enter the chamber was free to go to one 

 side or the other, but since it is positively phototrophic it would 

 be expected, other factors being equal, to go to the light exerting 

 the greater stimulus. 



3. Results. The moths reacted to the various pairs of lights 

 as shown in table 10. The numbers represented in table 10, 

 though too small to warrant a comparison of the percentages 

 of the responses to the various colors, nevertheless show that 

 of the four colors used those of the more refrangible rays are 

 more effective in stimulating and orienting the adult Feltia sub- 

 gothica. The effectiveness of the four colors, therefore, is in 

 the order beginning with the strongest: blue, green, yellow, red. 



F. Periplaneta americana Linne (adult) 



The adult cockroach, Periplaneta americana, has, so far as 

 I know, never been used in experiments with spectral lights. 

 Graber ('84) has, however, made a series of investigations with 

 a closely allied form, Blatta germanica Linne, with colored lights 

 produced by means of screens. 



TABLE 10 



Reactions of Feltia to pairs of monochromatic lights of equal intensity 



