Protection by Mimicry–A Problem in Mathematical Zoology

Abstract

UNDER the above heading in the Japan Weekly Mail of February 3, 1883, we drew attention to what appeared to us an error made by Mr. Alfred R. Wallace in a letter to NATURE regarding the protection gained by two distinct species of insects of distasteful nature assimilating in appearance when subject to the attacks of young and inexperienced birds. The article was sent to Mr. Wallace, who by letter, and in an article in NATURE, vol. xxvii. p. 481, without hesitation, acknowledged the correction, saying that he had misstated Dr. Müller's proposition. He then gives Dr. Müller's own words, which are:—“If both species are equally common, then both will derive the same benefit from their resemblance—each will save half the number of victims which it has to furnish to the inexperience of its foes. But if one species is commoner than the other, then the benefit is unequally divided, and the proportional advantage for each of the two species which arises from their resemblance is as the square of their relative numbers.” This alters the question altogether. Mr. Wallace had stated it, through an oversight, quite otherwise. He said:—“The number of individuals sacrificed is divided between them in the proportion of the square of their respective numbers.” Such was what we took objection to; and we showed that it was not according to the squares, but to the simple numbers.