On Mimicry

Abstract

IN a letter on p. 197 of NATURE, which I saw only a few days ago, Mr. Walter F. H. Blandford, referring to my suggestion as to the scarcity of individuals of mimetic species of Lepidoptera, rightly insists, that it has first to be shown that there is correlation between the acquirement of mimetic resemblance and the production of small numbers of specimens, before my suggestion becomes acceptable, and adds, that the advantage which the imago state of Lepidoptera probably derives from the resemblance to an immune model may possibly be counteracted by increased destruction in other stages. Mr. Blandford has apparently not taken into account what I thought to be too well known to need fuller explanation, and hence touched only by stating that “so many mimetic species are scarce, in comparison with the non-mimetic allies,” namely, that the number of rare forms amongst mimics is remarkably greater in proportion than the number of rarities among their non-mimetic allies. This excess of scarcity among mimics Mr. Blandford's assumption of increasing destruction in the larval states does not meet, unless we assume, further, that only rare species can become mimetic, or that the excess of rarity among the forms which have become mimetic is due to the acquirement of mimetic resemblance, i.e. that there is the kind of correlation which my suggestion (p. 153) requires. In support of the latter alternative—the former does not concern us here—I adduce the following statements, at which I arrived by a comparison of the mimetic and nonmimetic forms of those two groups of Eastern Papilios among which mimicry occurs (Haase's subgenera Cosmodesmus and Papilio, s. str.)