XIII 
THE COLOURS OF BIRDS 
269 
bands near the tip of the general contour-feathers, or 
as longitudinal bands at the edges of the quill-feathers. 
Fig. 2.—Barb and barbules from feathers of sun-birds, 
magnified to show the peculiar structure of metallic barbules. 
a is a barb bearing both proximal and distal barbules, the 
lower barbules being partially, the upper completely metallic. 
b, non-metallic distal barbules from a tail-cjuill of a sun- 
bird, showing lamina, hooklets, and filamentous region. 
c, partially metallic distal barbules ; the colour is confined 
to the enlarged filamentous region, but the lamina and 
hooklets persist unaltered, d, completely metallic barbules, 
with no trace of hooklets or lamina. 
In tint they are usually green, blue, violet, or reddish- 
violet, yellow or red structural colours being absent. 
