128 THE MEANING OF EVOLUTION 
women is so intensely attractive to man, and that 
vigor and manliness in man are so attractive to 
women, leads us to infer that among the lower ani- 
mals, although of course in a vastly less degree, vigor 
and beauty are also attractive. The weakest point of 
the position lies in the fact that it probably presup- 
poses a higher degree of capacity for appreciation on 
the part of lower animals than they possess. Those 
who deny the truth of the theory laugh at the idea 
that a butterfly can see clearly enough and care enough 
for what it sees to notice whether its mate has wings 
of one type or of another. The size, number and 
position of the spots on the wings of many butterflies 
are so nearly constant that they cannot of themselves 
have been entirely determined by the choice of the in- 
sect. Yet this may not preclude the possibility of the 
fact that, while the spots were produced through some 
other agency, certain types of them were selected by 
sexual preference. 
If attractive coloration is effective anywhere in the 
animal world, it will possibly be found among the in- 
sects, but it is especially likely to be found among the 
birds. Very many field workers in these groups feel 
quite sure of the value of attractiveness. When but- 
terflies chase each other up and down, circling and 
doubling, following each other for long distances, it 
would certainly seem as if they were pleased with 
