VIII 
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. " 
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. 
