274 
COLOUR IN NATURE 
CHAP. 
Colours of Humming-birds 
Turning now to humming-birds, we find that 
here pigmental colours are of relatively little im¬ 
portance, while structural colours attain an extra¬ 
ordinary beauty and brilliancy. Further, we find 
that the place of the pigmental colours of sun-birds 
in contrasting with and showing up the metallic 
colours is taken in humming-birds by black and 
white. White especially is often of great import¬ 
ance in producing the general effect of beauty. 
Fig. 3.—Metallic feather from the throat of a humming¬ 
bird. The colour is confined to the central pigmented 
patch and is there exceedingly bright. The barbs are con¬ 
tinued beyond the metallic region, but are then without 
barbules. The figure at the side is a section through the 
barb to show the method of insertion of the barbules which 
produces strongly marked ridges on the surface, so that the 
barbs lie at the bottom of a trough. 
In humming-birds metallic tints occur in both 
sexes, but are usually more brilliant in the male. 
They very frequently occur on the general contour- 
feathers, the colour being then often a bronze-green, 
which is not sharply confined to a transverse band, 
but fades away gradually behind. The metallic 
