COLOURS OF ANIMALS. 189 



Theory of Warning Colours. These differ greatly 

 from the last class, inasmuch as they present us with a 

 variety of brilliant hues, often of the greatest purity, and 

 combined in striking contrasts and conspicuous patterns. 

 Their use depends upon their boldness and visibility, not 

 on the presence of any one colour ; hence we find among 

 these groups some of the most exquisitely-coloured 

 objects in nature. Many of the uneatable caterpillars 

 are strikingly beautiful ; while the Danaidse, Heliconidae, 

 and protected groups of Papilionidse, comprise a series of 

 butterflies of the most brilliant and contrasted colours. 

 The bright colours of many of the sea-anemones and 

 sea-slugs will probably be found to be in this sense 

 protective, serving as a warning of their uneatableness. 

 On our theory none of these colours offer any difficulty. 

 Conspicuousness being useful, every variation tending to 

 brighter and purer colours was selected ; the result being 

 the beautiful variety and contrast we find. 



Imitative Warning Colours : The Theory of 

 Mimicry. We now come to those groups which gain 

 protection solely by being mistaken for some of these 

 brilliantly coloured but uneatable creatures, and here 

 a difficulty really exists, and to many minds is so 

 great as to be insuperable. It will be well therefore to 

 endeavour to explain how the resemblance in question 

 may have been brought about. 



The most difficult case, and the one which may be 

 taken as a type of the whole class, is that of the 

 genus Leptalis (a group of South American butterflies 

 allied to our common white and yellow kinds), many of 

 the larger species of which are still white or yellow, and 

 which are all eatable by birds and other insectivorous 



