v COLOURS OF ANIMALS 351 



showy colours and slow flight. It is good for them to be 

 seen and recognised, for then they are never molested ; but 

 if they did not differ in form and colouring from other 

 butterflies, or if they flew so quickly that their peculiarities 

 could not be easily noticed, they would be captured, and 

 though not eaten would be maimed or killed. 



As soon as the cause of the peculiarities of these butterflies 

 was clearly recognised, it was seen that the same explanation 

 applied to many other groups of animals. Thus, bees and 

 wasps and other stinging insects are showily and distinctively 

 coloured ; many soft and apparently defenceless beetles, and 

 many gay-coloured moths, were found to be as nauseous as the 

 above-named butterflies ; other beetles, whose hard and glossy 

 coats of mail render them unpalatable to insect-eating birds, 

 are also sometimes showily coloured ; and the same rule was 

 found to apply to caterpillars, all the brown and green (or 

 protectively coloured species) being greedily eaten by birds, 

 while showy kinds which never hide themselves like those 

 of the magpie-, mullein-, and burnet- moths were utterly 

 refused by insectivorous birds, lizards, frogs, and spiders 

 (p. 84). Some few analogous examples are found among 

 vertebrate animals. I will only mention here a very interest- 

 ing case not given in my former work. In his delightful 

 book, entitled The Naturalist in Nicaragua, Mr. Belt tells us 

 that there is in that country a frog which is very abundant, 

 which hops about in the day-time, which never hides him- 

 self, and which is gorgeously coloured with red and blue. 

 Now frogs are usually green, brown, or earth-coloured, feed 

 mostly at night, and are all eaten by snakes and birds. 

 Having full faith in the theory of protective and warning 

 colours, to which he had himself contributed some valuable 

 facts and observations, Mr. Belt felt convinced that this frog 

 must be uneatable. He therefore took one home, and threw 

 it to his ducks and fowls ; but all refused to touch it except 

 one young duck, which took the frog in its mouth, but 

 dropped it directly, and went about jerking its head as if 

 trying to get rid of something nasty. Here the uneatableness 

 of the frog was predicted from its colours and habits, and we 

 can have no more convincing proof of the truth of a theory 

 than such previsions. 



