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 
