72 CHILDHOOD OF ANIMALS 



which stand out conspicuously against the general brown coloratiorf 

 of the body ; whilst the white, erect tails of rabbits and other 

 small creatures that run in single file in the dusk along special 

 tracks may well serve as moving sign-posts. 



The most common case of the utility of conspicuous coloration 

 is when that serves to advertise an animal to its enemies, so that 

 it may be easily seen, easily remembered and avoided in future. 

 It is plain that such an advertisement is of little use unless it be 

 associated with the existence of an unpleasant or dangerous property, 

 such as nasty flavour, bad odour, power of stinging or of giving 

 poisonous bites. The advantage is either to the individual animal or 

 to the species, or to both. It is useless for a snake to have to strike 

 its poison-fangs into an animal that is too big for it to eat ; it is 

 worse than useless, for the process exhausts the poison glands 

 temporarily and puts them out of action so that they cannot be 

 used for some time for the purposes of the snake, whilst there is 

 always a chance of the snake itself being killed and eaten by its 

 prey. And so bright colours, terrifying attitudes and noises, such 

 as hissing and rattling, are useful to the snake. Warning colours 

 are still more useful in the case of bees where the sting is left in 

 the wound and its loss kills the bee. Very many smaU animals 

 with evil odours, such as skunks, have patterns of vivid black and 

 white which are specially visible in the dusk, and it is supposed 

 that they can thus be recognised by carnivorous animals that 

 otherwise would kiU them and then find themselves unable to eat 

 them. No doubt a few individuals would perish each season 

 whilst young carnivores were learning the lesson that such animals 

 were not worth the trouble of killing, but the species would gain. 



Opinions differ widely as to the closeness of relation between. 

 unpalatabUity and bright colours amongst insects, but after reading 

 through a considerable part of the very extensive and rather 

 pugnacious literature on the subject, I think there is a strong 

 balance of evidence in favour of the view first suggested by 

 A. R. Wallace to Darwin, that adult insects and caterpillars which 

 insectivorous birds and lizards find nauseous are extremely often 

 brightly coloured and conspicuously marked. Some of the most 

 striking negative experiments have been made on birds and reptiles 

 in captivity, and as these are frequently tame and accustomed to 

 take any food that is offered to them, it is not surprising that they 

 have been found to eat insects that are probably nauseous. Such 

 negative evidence is more than outweighed by the cases where 



