184 Evolution and Adaptation 
namely fishes, amphibians, reptiles and birds, that various 
kinds of crests, knobs, horns and combs have been developed 
apparently for this sole purpose.” , 
It is asking a great deal to suppose that animals, so dull 
and sluggish as these beetles, are endowed with a sufficient 
zesthetic discrimination to select in each generation those 
males whose horns are a little longer than the average. The 
resemblance of the horns to those of stags is, as Darwin 
points out, obvious, but in the latter case also it remains to 
be proven that they are the result of sexual selection, as 
Darwin believes to be the case; but the evidence for this 
belief is not much better, as we shall see in the case of the 
antlers of deer, than it is in these beetles. 
In regard to butterflies, the males and females are both 
often equally brilliantly colored; in other species the differ- 
ences in the sexes are very striking. Darwin states :— 
“Even within the same genus we often find species pre- 
senting extraordinary differences between the sexes, whilst 
others have their sexes closely alike.” The fine colors of 
the wings of many moths are also supposed by Darwin to 
have arisen through sexual selection, although the colors 
are usually on the lower wings, which are covered during 
the day by the less ornamented upper wings. It is assumed 
that, since the moths often begin to fly at dusk, their colors 
might at this time be seen and appreciated by the other sex. 
It should not be overlooked, however, that, in the case of 
some of the most highly colored moths, it is known that the 
males find the females through the sense of smell. More- 
over, although moths are often finely colored, Darwin points 
out that “it is a singular fact that no British moths which 
are brilliantly colored, and, as far as I can discover, hardly 
any foreign species, differ much in color according to sex; 
though this is the case with many brilliant butterflies.” 
Yet Darwin does not hesitate to conclude: “From the sev- 
eral foregoing facts it is impossible to admit that the brilliant 
