Page:Popular Science Monthly Volume 21.djvu/615

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599
ANIMAL SELF-DEFENSE.

or odors, which are not a matter of consciousness or will. In illustration of this method of defense, it will be sufficient to quote the following: "In South America there is a family of butterflies termed Heliconidœ, which are very conspicuously colored and slow in flight, and yet the individuals abound in prodigious numbers, and take no precautions to conceal themselves, even when at rest during the night. Mr. Bates found that these conspicuous butterflies had a very strong and disagreeable odor; so much so, that any one handling them, and squeezing them as a collector must do, has his fingers stained and so infected by the smell as to require time and much trouble to remove it. It is suggested that this unpleasant quality is the cause of the abundance of the Heliconidœ; Mr. Bates and other observers reporting that they have never seen them attacked by the birds, reptiles, or insects, which prey upon other lepidoptera."

Great numbers of animals are permanently colored so as to harmonize with their favorite surroundings. This obscure coloring may be either for the purpose of securing prey, or for concealment. The banded colors of the tiger perfectly blend with the lights and shadows in the jungle-grass. Those forest animals which live on the ground, as game-birds, deer, rabbit, or squirrel, are of brown or neutral hues, which assimilate to the color of dead leaves and tree-trunks; and they are quite impossible to discover as long as they remain motionless. Animals of the desert are dull or rust colored, or of some light tint. Insects, frogs, and lizards, which live among the leaves, are green; those on the ground in dry or rocky places are pale accordingly. Grasshoppers generally have the prevailing hue of the fields where they subsist. Indeed, protective coloration is very common, and any person can find examples.

More remarkable, however, is the protection afforded by what is termed chromatic function. "It consists in the power possessed by many fishes, crustaceans, amphibia, and reptiles, of adapting their general coloring, often by extremely rapid alteration, to the coloring of the surrounding objects, so that they seem to be helped by it in the pursuit of their prey, or especially protected against the attacks of their enemies."

This is very striking in many fishes. It can be readily observed in the common tree-frogs. The chameleon and the devil-fishes are famous for their power of changing color when irritated. The degree of consciousness involved in this is unknown.

The resemblance to inanimate objects of many small animals, especially insects, is one of the most curious things commonly met with. Insects imitate leaves, sticks, dry twigs, stones, lichens, etc., so perfectly as to sometimes deceive the close observer. The most remarkable examples are found in the tropics, where insect-life luxuriates. Wallace thus describes an Indian butterfly (Kallima): "The upper surface of these is very striking and showy, as they are of large size,