10 MIMICRY— [ch. 



use Bates' term they "mimicked" the Ithomiines, 

 and he set to work to devise an explanation of how 

 this could have come about. The Origin of Species 

 had just appeared and it was natural that Bates 

 should seek to interpret this peculiar phenomenon on 

 the lines there laid down. How was it that these 

 Pierines had come to depart so widely from the general 

 form of the great bulk of their relations, and to mimic 

 so closely in appearance species belonging to an 

 entirely different group, while at the same time con- 

 serving the more deeply seated anatomical features 

 of their own family ? If the change was to be regarded 

 as having come about through the agency of natural 

 selection it must clearly be of advantage to the 

 mimicking forms ; otherwise natural selection coidd 

 not come into operation. What advantage then have 

 the Ithomiines over the majority of butterflies in those 

 parts ? They are small insects, rather flimsy in 

 build, with comparatively weak powers of flight, and 

 yet so conspicuously coloured that they can hardly 

 be mistaken for anything else. In spite of all this 

 they are little subject to the attacks of enemies such 

 as birds, and Bates attributed this to the fact that 

 the juices of their bodies are unpalatable. According 

 to him their striking and conspicuous pattern is of 

 the nature of a warning coloration, advertising their 

 disagreeable properties to possible enemies. A bird 

 which had once attempted to eat one would find it 

 little to its taste. It would thenceforward associate 

 the conspicuous pattern with a disagreeable flavour 



