COLOR VISION 351 



question but that these creatures while in their nests 

 avoid white light, and particularly rays of the shorter 

 wave lengths, and that red is much less efficient in stimu- 

 lating them than any other color. The effect of the dif- 

 ferent rays is at least to some degree specific. The dis- 

 tribution of efficiency in stimulating ants in the prismatic 

 solar spectrum is certainly not proportional to the dis- 

 tribution of energy or brightness as judged by the human 

 eye. But why this is true and what mechanism is involved 

 in the process of avoiding the shorter waves are questions 

 upon which Lubbock's results have no definite bearing. 



Can the reactions of ants to colors be explained by 

 assuming that they are negative to rays of the shorter 

 wave lengths, and that they are oriented by the light in 

 the sense of Loeb's definition of heliotropism, or in any 

 other definite way? In the absence of larvae or pupae there 

 is some evidence indicating that ants orient and move 

 from light containing the shorter waves, and that their 

 movements are fairly definitely controlled by external con- 

 ditions, but in the presence of these organisms there is no 

 evidence showing that their reactions are thus definitely 

 controlled. Under such conditions internal factors must 

 have much to do with the reactions. In transferring 

 larvae and pupae, as in the experiment of Lubbock quoted 

 above, a given individual may pass back and forth many 

 times from the red end of the spectrum to the violet and 

 ultra-violet before all the young are deposited in the red 

 or beyond. It cannot be maintained that they become nega- 

 tive to violet light when they are carrying their young and 

 positive when they are not; for this opposes the fact that 

 in the absence of larvae and pupae they avoid the violet. 

 During the process of transferring their young the ants 

 cannot therefore be considered either negative or positive 

 to the violet or to any other color or condition of illumi- 

 nation. These reactions must be regulated primarily by 

 internal factors. What these factors are is a question con- 

 cerning which there is yet very little knowledge. That the 



