Can multiple-model mimicry explain warning signal polymorphism in the wood tiger moth, Arctia plantaginis (Lepidoptera: Erebidae)?

Abstract

Multiple-model mimicry, whereby different morphs of an aposematic species each resemble another defended species sharing the costs of predator education, has been proposed as a mechanism allowing colour polymorphisms in aposematic species. Male wood tiger moths, Arctia plantaginis (Linnaeus, 1758), are chemically defended and polymorphic (yellow, white) for hindwing coloration. We selected four potentially aposematic moth species and studied whether Müllerian mimicry exists between them and A. plantaginis morphs. We tested the moths’ relative palatability to natural predators with and without visual cues, their phenotypic similarity under a bird visual system, and whether trials with a potential moth model influence a predator’s willingness to attack A. plantaginis. Our results show that (1) three of the four tested species were not sufficiently unpalatable and thus not potential models for A. plantaginis, and (2) birds confused the unpalatable yellow model Arichanna melanaria with yellow A. plantaginis, although their overall appearance is distinguishable. This indicates imperfect mimicry based on shared colour cues. Multiple-model mimicry is thus a potential contributor to the maintenance of multiple morphs, although no unpalatable model was found for the white morph. Our findings highlight the importance of accounting for both prey coloration and palatability, which in concert affect predator behaviour, the ultimate driver of mimicry evolution.