v COLOURS OF ANIMALS 381 
that “it is so bold that the sight of man creates no alarm.” 
The beautifully-coloured Thaumastura cora “rarely permits 
any other humming-bird to remain in its neighbourhood, but 
wages a continual and terrible war upon them.” The magni- 
ficent bar-tail, Cometes sparganurus, one of the most imposing 
of all the humming-birds, is extremely fierce and pugnacious, 
“the males chasing each other through the air with surprising 
perseverance and acrimony.” These are all the species I find 
noticed as being especially pugnacious, and every one of them 
is exceptionally coloured or ornamented, while not one of 
the small, plain, and less ornamental species are so described, 
although many of them are common and well observed species. 
It is also to be noticed that the remarkable pugnacity of these 
birds is not confined to one season or even to birds of the 
same species, as is usual in sexual combats, but extends to any 
other species that may be encountered, while they are said 
even to attack birds of prey that approach too closely to 
their nests. It must be admitted that these facts agree well 
with the theory that colour and ornament are due to surplus 
vital energy and a long course of unchecked development. 
We have also direct evidence that the males are more active 
and energetic than the females. Mr. Gosse says that the 
whirring made by the male Polytmus humming-bird is shriller 
than that produced by the female; and he also informs us 
that the male flies higher and frequents mountains, while the 
female keeps to the lowlands.? 
Theory of Normal Colours 
The remaining kinds of animal colours, those which can 
neither be classed as protective, warning, nor sexual, are for 
the most part readily explained on the general principles of 
the development of colour which we have now laid down. It 
is a most suggestive fact that in cases where colour is required 
only as a warning, as among the uneatable caterpillars, we 
find, not one or two glaring tints only, but every kind of 
colour disposed in elegant patterns, and exhibiting almost as 
much variety and beauty as among insects and birds. Yet 
1 Some other cases are noticed at p. 317. For some further develop- 
ments and illustrations of the theory of sexual colour, see Darwinism, 
chap. x. 
