COLOUR AND PATTERN IN ANIMALS 73 



they have either completely refused the subjects of experiment or 

 rejected them after tasting ; whilst the fact that brightly coloured 

 insects and caterpillars in their native haunts very seldom conceal 

 themselves is a cogent argument for the view that they are un- 

 palatable. It has been found, moreover, that young birds and 

 no doubt the same is true of young lizards have no instinctive 

 knowledge of which insects are not good to eat, and that they have 

 to learn by experiment. Such experimental tasting must be 

 disastrous to the individual subjected to it, but as insects and their 

 caterpillars usually occur in great numbers at a time, the species 

 gains, although some of its individual members perish. 



Other cases of the possible utility of bright colour and conspicuous 

 pattern are grouped under the theory of mimicry. It is certainly 

 true that some animals without unpleasant qualities resemble very 

 closely, in their appearance and ostentatious habits, other animals 

 living in the same locality which have both conspicuous coloration 

 and some quality the possession of which it is useful to advertise. 

 The genuinely unpleasant creature is called the model, and the 

 creature resembling it is called the mimic, and it was supposed by 

 H. W. Bates, who first suggested this explanation, that the imitation 

 of the model by the mimic was useful to the latter by deceiving its 

 enemies into the belief that they had to deal with an animal 

 better left alone. The most probable examples occur amongst 

 insects. Ants, because of their ferocity and their power of defence 

 and aggression by means of their biting jaws and venomous stings, 

 are very generally left alone by other members of the animal kingdom, 

 and are frequently closely imitated by harmless beetles and bugs. 

 The stinging bees and wasps are similarly imitated in coloration 

 and pattern by harmless flies. Manv tropical butterflies and moths 

 that are known to be distasteful are brightly coloured and show by 

 their habits and slow flight that it is not necessary for them to 

 avoid attracting attention. They are closely mimicked by other 

 butterflies and moths that are not distasteful. 



It is plain that if such mimicry really bear the interpretation that 

 has been placed upon it, it can be effective only when the mimics 

 are less numerous than the models. Otherwise, in the process of 

 the experiments of young birds and other insectivorous creatures, 

 the lesson would be spoiled if the brightly coloured creatures were 

 as often harmless or tasty as otherwise. F. Miiller extended the 

 theory of mimicry to cover a further set of observations. He 

 showed that frequently a number of different species or kinds of 



