STRUCTURAL COLOUR: STAR SPECIES NUMBER 3
Name: Heliconius butterfly (actually more of a star genus than a star species)
Special Power: Disguises Itself as a Nasty Tasting Butterfly!
Heliconius comprises a colourful and widespread genus of brush-footed butterflies commonly known as the longwings or heliconians. This genus is distributed throughout the tropical and subtropical regions of the New World, from South America as far north as the southern United States.
Brought to the forefront of scientific attention by Victorian naturalists, these butterflies exhibit a striking diversity and mimicry, both amongst themselves and with species in other groups of butterflies and moths. The study of Heliconius and other groups of butterfly mimics allowed the English naturalist Henry Walter Bates, following his return from Brazil in 1859, to lend support to Charles Darwin, who had found similar diversity amongst the Galapagos finches.
Because of the type of plant material that Heliconius caterpillars favor and the resulting poisons they store in their tissues, the adult butterflies are usually unpalatable to predators. This warning is announced, to the mutual benefit of both parties, by bright colours and contrasting wing patterns, a phenomenon known as aposematism. Heliconius butterflies are thus mimics of one another, and also involved in mimic the patterns and colours of various species of butterflies and moths.
Heliconius butterflies have been a subject of many studies, due partly to their abundance and the relative ease of breeding them under laboratory conditions, but also because of this extensive mimicry. From the nineteenth century to the present day, their study has helped scientists to understand how new species are formed and why nature is so diverse. In particular, the genus is suitable for the study of both Batesian mimicry and Müllerian mimicry.
Batesian mimicry is quite simply a form of copying – where a harmless species has evolved to imitate the warning signals of a harmful species directed at a predator of them both.
Müllerian mimicry is a more complex phenomenon in which two or more, possibly related but often distasteful, species that share one or more common predators have come to mimic each other’s warning signals to their mutual benefit. Predators learn to avoid all of them with just a few experiences. Müllerian mimicry is named after the German naturalist Fritz Müller, who first proposed the concept in 1878, supporting his theory with the first mathematical model of frequency-dependent selection, one of the first such models anywhere in biology.