SELECTION IN COLOURING. 335 



as the stingless Chrysididce and many proboscidian beetles, are 

 protected by a strong coat of mail ; bugs, lady-birds, and many 

 butterflies have dermal glands from which the secretion — as 

 every one knows in the case of the bug — is excessively objec- 

 tionable to the pursuer, or even in some way injurious ; others 

 can escape pursuit by extreme . rapidity of liight, while others 

 again assume a peculiar posture by which — as it would seem — 

 they can actually frighten away their enemies. It is in connec- 

 tion with these facts that, according to the statements of this 

 distinguished naturalist and of other inquirers, such brilliantly 

 coloured insects are usually, if not invariably, avoided by the 

 generality of insect-eaters; birds — as well as frogs and lizards — 

 showing a preference for the dull-coloured over the gaily 

 coloured species. This view is strengthened by the fact adduced 

 by Wallace that those insects or larvse which are inconspicuous 

 in colour are commonly devoid of any kind of defensive weapons 

 such as are found in the more splendidly coloured species. 

 Hence, according to Wallace, the use of the bright colours is 

 evident ; the creatures which pursue these insects soon learned 

 by experience, and communicated to their progeny, the useless- 

 ness of pursuing these harlequin insects, as any attempt to 

 attack them might be bitterly avenged. 



At the first glance this view seems a striking one. It may 

 be the correct one in many or all of the cases here adduced, but 

 it is certainly open to doubt whether it can be unhesitatingly 

 applied — as has sometimes been done — to every case of splendid 

 colouring in the skin of animals. Darwin has already raised 

 this question as against Wallace, and he proposes to substitute 

 the view that all or most cases of brilliant colouring have 

 originatsd from a variety of natural selection which he terms 

 Sexual Selection. According to this view, coloiu-ing has resulted 

 from the determining selective influence of the sexes and their 

 preference for certain colours and modes of colouring. Still, 

 Darwin himself had already mentioned, though only inciden- 

 tally, that there are many animals characterised by their 

 splendid motley or metallic colouring which could not have 

 preserved it through sexual selection; for example, all the 

 different Polypes, and more particularly the sea-anemones and 



