WARNING COLORATION. Certain ani mals are protected from the attacks of other kinds by secreting a repugnant fluid which is either ejected from special repugnatorial glands or which, in the ease of insects. gives them a bad taste. so that they are not eaten by monkeys, birds. lizards, or by other insects. Such inedible species are often conspicuously marked with bright colors. spots. or bands, and such colors are said to warn-toff intruders, which after their first experience recognize them as unfit to eat. A familiar example is the skunk, whose con spicuous black and white markings render it visible even in a rather dark night. Warning coloration is especially common in insects. es pecially gaily colored caterpillars and butter flies. like our milkweed butterfly ( Anosia ar ehippus). The brightly colored caterpiltars, like the currant worm and a number of others, when fed to birds are rejected by them with disgust.
Hence they enjoy an immunity from the at tacks of birds. Wallace. who first suggested the theory of warning colors, called attention to the fact that while most caterpillars are edible and also protectively marked (see PROTECTIVE COLORATION AND RESEMBLANCE), the gaily colored ones are distasteful to birds: and this has since been experimentally proved. Whether, however. the colors have been actually acquired. as Wallace supposes, "for the purpose of Serving as a warn ing of inedibility," still remains to be proved. It should be remembered that the bright red and blue colors of caterpillars and of butter flies are deep-seated and formed from the waste products of the blood, and that their deposition is a chemico-physical or physiological process quite independent of the visits or attacks of birds. etc.