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v COLOURS OF ANIMALS 387yellow with black heads. In North America we might haveraccoons, squirrels, and opossums, in parti-coloured livery ofwhite and black, so as exactly to resemble the skunk of thesame country ;while in South America they might be blackwith a yellow throat -patch, so as to resemble with equalcloseness the tayra of the Brazilian forests. Were suchresemblances to occur in anything like the number and withthe wonderful accuracy of imitation met with among theLepidoptera, they would certainly attract universal attentionamong naturalists, and would lead to the exhaustive studyof the influence of local causes in producing such startlingresults.One somewhat similar case does indeed occur among theMammalia, two singular African animals, the Aard-wolf (Proteles)and the hyaena-dog (Lycaon), both strikingly resemblinghyenas in their general form as well as in their spottedmarkings. Belonging as they all do to the Carnivora, thoughto three distinct families, it seems quite an analogous caseto those we have imagined ;but as the Aard-wolf and thehysena-dog are both weak animals compared with the hyaena,the resemblance may be useful, and in that case would comeunder the head of mimicry. This seems the more probablebecause, as a rule, the colours of the Mammalia are protective,and are too little varied to allow of the influence of localcauses 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 theinfluence of locality as do butterflies probably because thecauses which determine colour are in their case more complexyet 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 theWest Indian islands and Central America, several of whichhave white heads or foreheads, occurring in two distinctgenera, 1 while none of the more numerous parrots of SouthAmerica are so coloured. In the small island of Dominicawe have a very large and richly-coloured parrot (Chrysotisaugusta) corresponding to the large and richly -colouredbutterfly (Papilio homerus) of Jamaica.1 Pionus albifrons and Chrysotis senilis (C. America), Chrysotis sallroi (Hayti).