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 regar 
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..calours. I really see no reason why we should doubt 
the power r 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 
whether 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 
