52 THE COLOURS OF ANIMALS 



only applies in the warmer weather when there is 

 an abundance of insect food. In the winter, insectivo- 

 rous animals are pinched by hunger, and would devour 

 the pupa in spite of the cocoon. We therefore find 

 that all cocoons which contain pupaB during the winter 

 are well concealed, either spun between leaves which 

 fall off and become brown, or hidden under bark or 

 moss, or constructed on the surface of bark with a 

 colour and texture which renders them extremely 

 difficult to detect. It is very common for particles of 

 the bark to be gnawed off by the larva and fixed on to 

 the outside of the cocoon. It will be shown below 

 that many larvae can also control the colour of their 

 cocoons. 



Protective Resemblances in Butterflies and Moths 



The perfect insect is also commonly defended by 

 very efficient methods of concealment. The under 

 sides of the wings of butterflies are generally coloured 

 like the surface on which the insect habitually rests, 

 and they are the only parts seen during repose. We 

 can form some idea of the perfection of this conceal- 

 ment when we remember the entire disappearance of 

 common butterflies in dull weather. Many of them 

 creep far down among thickly set leaves, while others 

 rest freely exposed upon surfaces which harmonise 

 with their colours. 



Perhaps the most perfect concealment attained 

 by any butterfly is seen in the genus Kallima, found 



