190 THE COLOUES OF ANIMALS 



flies, are generally protectively coloured, and hide the 

 bright colours of other parts when the insect is at 

 rest. If the parts exposed during rest are conspicu- 

 ously coloured it is clear that they chiefly possess a 

 warning significance. I say ' chiefly,' because it is 

 probable that the appearance of the mature individuals 

 of any species, however much it may be specialised for 

 other ends, possesses a sexual significance, and appeals 

 as an adornment to the modified taste of the individuals 

 of the same species. We have a rough criterion of 

 the extent to which the taste has been modified when 

 we compare the appearances which have other addi- 

 tional meanings with those which possess a sexual 

 value alone, and which are concealed except during 

 flight and are especially displayed in courtship. 

 Warning Colours are also displayed during the slug- 

 gish flight of a nauseous species, but the insects with 

 purely ornamental colours are swift and wary when 

 upon the wing. 



But quite apart from these considerations, the 

 Warning Colours can be distinguished by the subordi- 

 nation of every other feature to that of conspicuous- 

 ness. Crude patterns and startling strongly contrasted 

 colours are eminently characteristic of a warning 

 appearance, while the colours and patterns produced 

 by courtship include everything that is most beautiful 

 in insects. The two kinds of appearance differ as an 

 advertisement differs from a beautiful picture : the 

 one attracts attention, the other excites admiration. 



