WARNING COLOURS AND MIMICRY 145 



assailant, profiting by experience, will refrain in future 

 from attacking similarly coloured insects. We shall 

 readily admit, for example, that an animal which has once 

 suffered from the sting of a wasp is likely to recognise 

 and avoid wasps for the rest of its life ; while the same 

 reasoning applies to insects, such as the ladybird and the 

 cinnabar moth caterpillar, which have a nauseous taste. 

 The whole conception is based upon the truth of the 

 adage, " once bit twice shy." Obviously a considerable 

 number of conspicuous insects must fall victims each year 

 to the attacks of young and inexperienced assailants. But 

 in nature the welfare of the individual is always subordi- 

 nate to that of the species ; and it is clear that " pro- 

 tected ' species — as those which possess some noxious 

 quality are usually termed — cannot fail to reap advantage 

 if their appearance is such that they will readily be seen 

 and recognised. 



This theory of warning coloration was first suggested 

 by Dr. A. R. Wallace to account for the extremely bright 

 colours displayed by certain caterpillars. It has since 

 been applied to whole groups of insects, of all orders ; and 

 so strong is the evidence in its favour — the result of 

 systematic experiments conducted in various latitudes 

 with birds, reptiles, and other insectivorous creatures — 

 that what was once hypothetical may now be regarded as 

 a well-established fact. Indeed, so characteristic are the 

 colours and patterns of protected insects, as distinct from 

 those which possess no noxious qualities, that an expert 

 naturalist is often able to form a shrewd guess as to 

 whether a newly discovered insect is warningly coloured 

 or not, even though he may be quite ignorant as to its 

 habits. Black, associated with white, yellow, or red, are 

 the commonest warning combinations ; while the patterns 

 usually consist of strongly defined rings, stripes, or spots. 



K 



