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MIMICRY

M.Tevfik Dorak, M.D., Ph.D.

Mimicry is the resemblance of one organism (mimic) to another (model) such that these two organisms are confused by a third organism (receiver). The model and mimic are not usually taxonomically related. In molecular mimicry, pathogenic organism (or a parasite) mimics a molecule of the host so that it escapes recognition as foreign (a kind of aggressive mimicry, see below). An evolving mimicry takes advantage of previously evolved communication signals and responses between organisms (for example, between a predator and a warningly colored prey). To be successful and beneficial to the mimic, the model should be an abundant species whose noxious characteristics have left a lasting impression on predator.

Batesian mimicry: First described by the British naturalist Henry Walter Bates in 1852. He found two unrelated but similarly marked families of Brazilian forest butterflies one of which (model) was poisonous to the birds and the other palatable ones (mimic) survived because of the resemblance to the poisonous ones. They usually mimic the aposematic coloration of the model species. In this kind of mimicry, the mimicking organism has evolved some features of a poisonous organism but is not poisonous itself. This is essentially equivalent to camouflage. Batesian mimicry is particularly common among insects. The mimicry by grasshoppers of poisonous tiger beetle is another example from the insect world. Theoretically, selection only favors the mimic if it is less common than the model. The fitness of the mimics is negatively frequency-dependent.

Mullerian mimicry: The German zoologist Fritz Muller proposed an explanation to Bates’s paradox in 1878. Bates had observed a resemblance among several unrelated butterflies all of which were inedible. This paradoxical observation puzzled him. Muller realized that the explanation might lie in the advantage to one inedible species in having a predator learn from another. Once the predator has learned to avoid the particular conspicuous warning coloration with which it had its initial contact, it would then avoid all other similarly patterned species, edible or inedible. Maximum protection is gained by Mullerian mimics when all individuals have the same signal (signal standardization). The number of individuals sacrificed in educating the predators is spread over all of the species sharing the same warning pattern (called mimicry rings). This tendency of inedible and noxious species to evolve to have the same or similar warning signals is called Mullerian mimicry. One example is the black and yellow striped bodies of social wasps, solitary digger wasps and the caterpillars of the cinnabar moths. Mullerian mimicry could be considered not to be true mimicry because the receiver is not actually deceived and it is not obvious which organism is the model and which one is the mimic.

Aggressive mimicry: The organism mimics a signal that is attractive or deceptive to its prey. The examples are the egg mimicry by cuckoos and praying mantis mimicking flowers and vegetation to attract insects (a wolf in sheep’s clothing). Another example is that cuckoo bees lay their eggs in the nests of humblebees, which they closely resemble. Host mimicry by parasites, in which the host is both the model and receiver, is an extension of aggressive mimicry. Most examples occur in birds and between viruses and their hosts including humans.

A lecture on mimicry from University College of London

Examples of Mimicry in Sea Animals

An article by Lev-Yadun on Aposematic Coloring in Plants

A high school activity on Mimicry with a list of examples

Female mimicry in garter snakes by Mason & Crews, 1985 & by Shine et al, 2001

Motion camouflage by Dragon Flies (New Scientist)

Crypsis & Mimicry Images Insect Mimicry The Art of Deception

Encyclopedia Britannica article on mimicry (subscribers only)

Animal Imposters: PBS video Adaptations for Survival in the Sea: ORG Video

M.Tevfik Dorak, MD, PhD

Last updated 9 January 2007

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