Butterflies - Warning Coloration And Mimicry
( Originally Published 1917 )
The colors of a great many animals, including a considerable percentage of American butterflies and their larvae, have been commonly explained by the theory of warning colors. According to this theory animals which were for any reason not edible by birds and mammals have developed various striking combinations of color such as black and yellow, red and black, or black and white, in order to advertise to their foes their inedible qualities. This theory has been very generally accepted by naturalists and will be found expounded at length in many books published during the last quarter century.
The whole subject of the validity of warning coloration has recently been brought up for reconsideration by the illuminating investigations of Mr. Abbott H. Thayer and discussed at length in the book upon "Concealing Coloration" already mentioned. In an appendix to this book dated 1908 Mr. Thayer states that he no longer holds the belief that "there must somewhere be warning colors." He has convincingly shown that a large proportion of the animals which were supposed to be examples of this theory are really illustrations of concealing coloration. But there yet remain various facts which have been conclusively proven that apparently require the theory of warning colors to explain them. Here is another field in which there is a real need for much careful investigation under conditions that are rigidly scientific.
Along with the theory of warning coloration the theory of mimicry has been propounded. According to this if a butterfly in a given region shows warning coloration, having developed such coloration because it is distasteful to birds and mammals, it may be mimicked by another butterfly in the same region belonging to another group, the latter butterfly being edible, but benefiting by its resemblance to the distasteful species, because birds or mammals mistake it for the latter and do not attempt to catch it. The most notable example of such mimicry in North America is that of the Monarch butterfly, which is supposed to be the distasteful species, and the Viceroy butterfly, which is supposed to mimic it. Several other instances of mimicry are found among our own butterflies, while in South America, Africa, and Asia there are number-less examples.