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COLOURS OF ANIMALS 
387 
yellow with black heads. In North America we might have 
raccoons, squirrels, and opossums, in parti-coloured livery of 
white and black, so as exactly to resemble the skunk of the 
same country ; while in South America they might be black 
with a yellow throat-patch, so as to resemble with equal 
closeness the tayra of the Brazilian forests. Were such 
resemblances to occur in anything like the number and with 
the wonderful accuracy of imitation met with among the 
Lepidoptera, they would certainly attract universal attention 
among naturalists, and would lead to the exhaustive study 
of the influence of local causes in producing such startling 
results. 
One somewhat similar case does indeed occur among the 
Mammalia, two singular African animals, the Aard-wolf (Pro- 
teles) and the hysena-dog (Lycaon), both strikingly resembling 
hyaenas in their general form as well as in their spotted 
markings. Belonging as they all do to the Carnivora, though 
to three distinct families, it seems quite an analogous case 
to those we have imagined; but as the Aard-wolf and the 
hysena-dog are both weak animals compared with the hyaena, 
the resemblance may be useful, and in that case would come 
under the head of mimicry. This seems the more probable 
because, as a rule, the colours of the Mammalia are protective, 
and are too little varied to allow of the influence of local 
causes producing any well-marked effects. 
When we come to birds, however, the case is different, 
for although they do not exhibit such distinct marks of the 
influence of locality as do butterflies — probably because the 
causes which determine colour are in their case more complex 
— yet there are distinct indications of some effect of the kind, 
and we must devote some little time to their consideration. 
One of the most curious cases is that of the parrots of the 
West Indian islands and Central America, several of which 
have white heads or foreheads, occurring in two distinct 
genera , 1 while none of the more numerous parrots of South 
America are so coloured. In the small island of Dominica 
we have a very large and richly-coloured parrot (Chrysotis 
augusta) corresponding to the large and richly -coloured 
butterfly (Papilio homerus) of Jamaica. 
1 Pionus albifrons and Chrysotis senilis (C. America), Chrysotis salM (Hayti), 
