The Defenses of Butterflies: Mimicry

Mimicry occurs when one group of organisms (mimics) evolves to share perceived characteristics with another group of organisms (models) through selective actions. There are many varieties of mimicry complexes that exist with varying results, but let's look at two particular types of mimicry that exist in the wonderful world of Lepidoptera and the scientists who are attributed with their discoveries.

Müllarian Mimicry

Johann Friedrich Theodor Müller (March 31, 1821 – May 21, 1897), better known as Fritz, was a German biologist and physician who emigrated to Brazil and spent his life studying the sub-tropical Atlantic forests south of Sao Paulo. Müller's discovery in the field of mimicry concerned resemblances between unpalatable species which helps to protect those species from predators capable of learning.

We can see a case of Müllarian Mimicry among the Monarch (Danaus plexippus) and Queen butterflies (Danaus gilippus) in Florida. Both species consume milkweed and sequester toxins from the plants in their bodies, making them both distasteful to predators such as birds. Both species utilize a aposematic or warning coloration of bright orange and red tones that generally warn of toxic qualities in prey. Both species resemble each other so strongly that they are often misidentified by people.

A bird that tastes a monarch will learn and remember that the bright orange coloration and pattern of decoration on a monarch butterfly is a signal of the unpalatability. A queen butterfly flying past later will likely be viewed as 'not food' since it bears such a striking resemblance to a creature which tasted very bad to the bird.

Thus the two species gain an advantage against predators by each offering the same bad taste to the predators and reinforcing that bad taste with a very similar appearance.

Left: monarch / Right: queen

Batesian Mimicry

Henry Walter Bates (February 8, 1825 – February 16, 1892) was an English naturalist who traveled to the Amazon with Alfred Russel Wallace (credited with the co-discovery of natural selection). Bates spent 11 years in the Amazon, sending home some 14,000 specimins of which about 8,000 were entirely new to science. With no formal education in science, Bates was an auto-didact (self-taught) scientist whose observations have helped to shape moden biology. If you have the opportunity, take a look at Bates' work The Naturalist on the Rivers Amazons which tells of his travels in the Amazon.

While in the Amazonian rain forest, Bates noted that noxious species of butterfly in one family of butterflies were often counterfeited in appearance by members of the Pierid (sulphur) family of butterflies. Bates work traced butterflies in the Danainae (milkweed)and Heliconiinae (longwing) families who feed on milkweed and passionvines respectively. The butterflies of these families sequester noxious compounds from their host plants within their bodies and therefore taste bad to predators.

In this mimicry complex, the Danaids and Helaconids become the models. Their mimics, members of the Pierid (or sulphur) family gain protection from predators by mimicing the visual appearance of the distasteful models. Even though they would be quite tasty to predators, the mimics appear to be noxious butterflies and thus are left alone by predators who have already encountered the noxious butterflies and learned that they are bad to eat.

Here in Florida there is an example of Batsian mimicry visible with the Pipevine Swallowtail (Battus philenor) and Tiger Swallowtail (Papilio glaucas). The Pipevine Swallowtail is the model, a butterfly that tastes noxious to predators because of chemicals consumed in its host plants, pipevines (aristolochia spp).

The Tiger Swallowtail, a normally bright yellow butterfly with tiger-like striping has a black form that occurs in females of the species in areas where the Pipevine Swallowtail is present. This black form mimics the look of Pipevine Swallowtails and gains protection for these female butterflies to mate and lay their eggs without being eaten. Probably very handy if you are a female Tiger Swallowtail.

Left: Pipevine male / Right: Tiger female, black form

Etymology of Mimicry
mimetic 1637, "having an aptitude for mimicry," from Gk. mimetikos "imitative," from mimetos, verbal adj. of mimeisthai "to imitate." Originally of persons, attested of animals or plants from 1851. Online Etymology Dictionary