Darwin was the first to establish the fact that the bright coloring of flowers is for the purpose of attracting insects in order to accomplish their fertilization, and deduces the general rule that all flowers fertilized by the wind are of dull and inconspicuous colors. In the animal kingdom the principle of assimilation guides and modifies coloring in conformity with surrounding nature, and it is, therefore, to a great extent, protective.
The lion inhabiting the desert is of the color of the sands, so as hardly to be distinguished at a short distance. The leopard lives in jungles, and the vertical stripes on its body harmonize admirably with the vertical
reeds of its tangled lair, and completely conceal it from view.
In arctic regions, white is the prevailing color, as here reign perpetual snows; therefore, it is that the bear is only found white in this part of the globe.
The curious fact that among birds the female is usually of a dull neutral tint, while the male monopolizes the bright colors, is accounted for on the principle of protective coloring, the female needing the obscurity afforded her by her sober plumage. When there is an exception to this rule, the protection is afforded in some other way. And this leads us to the subject of birds’ nests.
Wallace, in a chapter on the theory of birds’ nests, divides them into two classes, those in which the eggs are protected by the shape or position of the nest, and those in which they are left exposed to view. He then gives the following law: “That, when both sexes are of strikingly gay and conspicuous colors, the nest is of the first class, or so as to conceal the sitting bird; while, whenever there is a striking contrast of colors, the male being gay and conspicuous, the female dull and obscure, the nest is open and the sitting bird exposed to view.”
In connection with the subject of protective coloring, the phenomenon of mimicry is not the least curious. Wallace gives several instances of butterflies, moths, snakes, etc., where the coloring of protected families is imitated by weak and unprotected ones not in any way allied to them. A large and bright-colored butterfly, the heliconidæ of South America, which is protected by a disagreeable quality affecting its taste, thus rendering it secure from insect-eating birds, is imitated by a smaller and eatable family, resembling it so completely as to be quite indistinguishable by its
enemies from the former. Thus it is protected and enabled to perpetuate itself by borrowing the colors of its secure and powerful neighbor.
The elaps among venomous snakes is another instance where protection is afforded through mimicry to a harmless snake that would otherwise be defenceless. The elaps and the species that copy its coloring are found only in tropical America, and are peculiar as being the only snakes marked in the same manner by red, black, and yellow rings.