Some butterflies are dingy, others uniform, but in contrast to moths the
majority are beautifully colored. This is especially the case with
tropical forms. How the colors are variegated and contrasted in spots
and bands, how the hues are embellished by metallic shimmer, every one
knows; what exactly the color means is, however, still obscure. A few
general facts may be first noticed: (1) The color is in many cases
subject to variation--it cannot be said to be absolutely constant for a
species; (2) in some instances, at any rate, it is influenced by
external conditions, for different forms at different periods of the
year, is known in many kinds; (3) sometimes the color and markings,
especially of the under surface of the wings, are obviously of use for
the protection of the resting butterfly; (4) in some cases this
protective adaptation is so pronounced as to deserve to be called
mimicry; (5) in many cases the coloring is in direct connection with the
physical constitution of the species, and is usually most marked in the
males.