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 

 aesthetic 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 



