THE COLOURS OF ANIMALS AND PLANTS 133 



in order to soften them, rub them on their head or 

 legs till they are caught by the hairs which cover 

 them. "The whole proceeding is most human and 

 purposeful." These processes are gone through 

 both by night and day, and a blinded Stenorhynchus, 

 if cleaned of its weed, "will immediately begin to 

 clothe itself again with the same care and precision 

 as before." It shows no disposition to take up a 

 position among similarly coloured objects ; and some 

 individuals which have taken up stations among 

 weeds do not dress themselves at all. 



Warning Colours. 



If an animal belonging to a group liable to be 

 eaten by others, is possessed of a nauseous taste, 

 or if an animal, such as a wasp, is specially armed 

 and venomous, it is to its advantage that it should 

 be recognised quickly, and so avoided by animals 

 that might be disposed to take it as food. 



Hence arises warning coloration, the explanation 

 of which is due to Wallace. Darwin, who was 

 unable to explain the reason for the gaudy coloration 

 of some caterpillars, applied to Wallace, stated his 

 difficulty, and asked for suggestions. Wallace 

 thought the matter over, considered all known 

 cases, and then ventured to predict that birds 

 and other enemies would be found to refuse such 

 caterpillars if offered to them. This explanation, 

 first applied to caterpillars, soon extended to adult 

 forms, not only of insects, but of other groups as 

 well. 



