ADAPTATION FOR THE SPECIES 129 



each other's appearance. Some naturalists, especially 

 those who have worked chiefly in the laboratory, in- 

 sist that it is the odor, not the color of these insects, 

 which is attractive, and some experiments which have 

 been made would seem to point in this direction. But 

 the creatures experimented upon most carefully were 

 night-flying moths, and it is quite possible that the 

 sense of sight in the night-flying moths has lost its 

 vigor. 



The great difficulty in understanding sexual attrac- 

 tion in insects, as based upon beauty, lies in the un- 

 doubtedly lower development of their nervous activ- 

 ity; in other words, in the apparent absence of any- 

 thing worth calling mind. I think no one imagines 

 that a butterfly, looking upon two other butterflies 

 who are competing for her affections, deliberates be- 

 tween them, and determines to admit to the circle of 

 her friendship the more brilliantly colored male. 

 Moths are so irresistibly attracted to a light as to fly 

 into it without apparent power to withstand its influ- 

 ence. They repeat the flight again and again until 

 they are destroyed. If they react so vigorously to 

 the stimulus of the light, it seems not impossible that 

 they may also act vigorously to the stimulus of color 

 pattern, and that the male most beautifully colored, 

 according to the nervous ideal of the female, should 

 win her unconscious regard. At least it is certain 



