Decorative Colours 47 



large extent meet the claims made upon them by life, and produce 

 the adaptations which are most purposive, — a further proof, too, of 

 my proposition that the useful variations, so to speak, are always 

 there. The flowers developed the perfumes which entice their visitors, 

 and the male Lepidoptera developed the perfumes which entice and 

 excite their mates. 



There are many pretty little problems to be solved in this con- 

 nection, for there are insects, such as some flies, that are attracted 

 by smells which are unpleasant to us, like those from decaying flesh 

 and carrion. But there are also certain flowers, some orchids for 

 instance, which give forth no very agreeable odour, but one which 

 is to us repulsive and disgusting; and we should therefore expect 

 that the males of such insects would give off a smell unpleasant 

 to us, but there is no case known to me in which this has been 

 demonstrated. 



In cases such as we have discussed, it is obvious that there is 

 no possible explanation except through selection. This brings us to 

 the last kind of secondary sexual characters, and the one in regard 

 to which doubt has been most frequently expressed, — decorative 

 colours and decorative forms, the brilliant plumage of the male 

 pheasant, the humming-birds, and the bird of Paradise, as well as 

 the bright colours of many species of butterfly, from the beautiful 

 blue of our little Lycaenidae to the magnificent azure of the large 

 Morphinae of Brazil. In a great many cases, though not by any 

 means in all, the male butterflies are "more beautiful" than the 

 females, and in the Tropics in particular they shine and glow in the 

 most superb colours. I really see no reason why we should doubt 

 the power of sexual selection, and I myself stand wholly on Darwin's 

 side. Even though we certainly cannot assume that the females 

 exercise a conscious choice of the "handsomest" mate, and deliberate 

 like the judges in a court of justice over the perfections of their 

 wooers, we have no reason to doubt that distinctive forms (decorative 

 feathers) and colours have a particularly exciting effect upon the 

 female, just as certain odours have among animals of so many 

 different groups, including the butterflies. The doubts which existed 

 for a considerable time, as a result of fallacious experiments, as to 

 M'hether the colours of flowers really had any influence in attracting 

 butterflies have now been set at rest through a series of more careful 

 investigations; we now know that the colours of flowers are there 

 on account of the butterflies, as Sprengel first showed, and that the 

 blossoms of Phanerogams are selected in relation to them, as Darwin 

 pointed out. 



Certainly it is not possible to bring forward any convincing proof 

 of the origin of decorative colours through sexual selection, but there 



