vin ORIGIN AND USES OF COLOUR IN ANIMALS 201 



of the different species of sun-birds. Even the keen eye of a 

 hawk will fail to detect them, so closely do they resemble the 

 flowers they frequent. The sun-birds are fully aware of this 

 fact, for no sooner have they relinquished the flowers than they 

 become exceedingly wary and rapid in flight, darting arrow- 

 like through the air and seldom remaining in exposed situations. 

 The black sun-bird (Nectarinea amethystina) is never absent 

 from that magnificent forest-tree, the ' Kaffir Boom ' (Erythrina 

 caffra) ; all day long the cheerful notes of these birds may be 

 heard amongst its spreading branches, yet the general aspect 

 of the tree, which consists of a huge mass of scarlet and purple- 

 black blossoms without a single green leaf, blends and har- 

 monises with the colours of the black sun-bird to such an extent 

 that a dozen of them may be feeding amongst its blossoms 

 without being conspicuous, or even visible." 1 



Some other cases will still further illustrate how the colours 

 of even very conspicuous animals may be adapted to their 

 peculiar haunts. 



The late Mr. Swinhoe says of the Kerivoula picta, which 

 he observed in Formosa : " The body of this bat was of an 

 orange colour, but the wings were painted with orange-yellow 

 and black. It was caught suspended, head downwards, on a 

 cluster of the fruit of the longan tree (Nephelium longanum). 

 Now this tree is an evergreen, and all the year round some 

 portion of its foliage is undergoing decay, the particular leaves 

 being, in such a stage, partially orange and black. This bat 

 can, therefore, at all seasons suspend from its branches and 

 elude its enemies by its resemblance to the leaves of the 

 tree." 2 



Even more curious is the case of the sloths — defenceless 

 animals which feed upon leaves, and hang from the branches 

 of trees with their back downwards. Most of the species have 

 a curious buff-coloured spot on the back, rounded or oval in 

 shape and often with a darker border, which seems placed 

 there on purpose to make them conspicuous ; and this was a 

 great puzzle to naturalists, because the long coarse gray or 

 greenish hair was evidently like tree-moss and therefore 

 protective. But an old writer, Baron von Slack, in his Voyage 



1 Trans. Phil. Soc. (? of S. Africa), 1878, part iv, p. 27. 

 2 Proc. Zool. Soc, 1862 p. 357. 



