i e e . 
xviii The Naturalist in Nicaragua 
and, neither snatching nor biting it, deliberately tears it 
across, aS a man tears paper with his hands. He then puts 
one end of it into his mouth, and after chewing it up, pre- 
sumably to soften it, takes it out in the chele and rubs it 
firmly on his head or legs until it is caught by the peculiar 
curved hairs which cover them. If the piece of weed is 
not caught by the hairs, the crab puts it back in his mouth 
and chews it up again. The whole proceeding is most 
human and purposeful.” 
There is another class of colours in which not conceal- 
ment but conspicuousness is the object aimed at. Such 
colours are borne by animals provided with formidable 
weapons of defence (the sting of the wasp, for example), or 
possessed of an unpleasant taste or offensive odour, and 
their foes come by experience to associate this form of 
colouring with disagreeable qualities and avoid the animals 
so marked. Belt was the first to account, in this way, for 
the conspicuous colouration of the skunk; and it is now 
believed that startling colours and conspicuous attitudes 
are intended to assist the education of enemies by enabling 
them to learn and remember the animals which are to be 
avoided. The explanation of warning colours was devised 
by Mr. Wallace to account for the brilliancy in the tints of 
certain caterpillars which birds find disagreeable, and the 
subject has been principally studied by experiments upon 
such caterpillars. But examples of warning colours are 
recognised, among many others, in the contrasted’ black 
and yellow of wasps, bees, and hornets, the bright red, 
black, and yellow bands of the deadly coral snakes, and 
the brilliantly coloured frog of Santo Domingo which hops 
unconcernedly about in the daytime in his livery of red 
and blue—‘‘ for nothing will eat him he well doth know.” 
But—and here comes in the principle to which the term 
‘‘mimicry ” is now restricted—if warning colours are help- 
ful to noxious animals, then defenceless animals acquiring 
these colours will share in the protection afforded by 
them. And so we find a deceptive similarity between 
animals occurring in the same district, but not closely 
related, in which the mimicked form is unpalatable or has 
an odour repulsive to birds and lizards. It must, of course, 
be understood that the mimicry is unconscious, the result, 
as in the cases of cryptic resemblance, having been brought 
