Mimicry in Butterflies

Many animals that are poisonous or bad-tasting advertise this fact with bright colors. A bird that eats a bitter butterfly with orange and black wings usually becomes ill and learns to avoid similar insects. Such warning colors benefit both the predator, which avoids a bad meal, and the prey, which is left alone.

In 1862, the naturalist Henry Walter Bates noticed that some harmless butterflies in the Amazon closely resembled poisonous species. He proposed that these imitators gain protection without the cost of producing toxins, because predators mistake them for the dangerous models. This form of deception is now called Batesian mimicry. It works only as long as the mimics remain relatively rare; if they became common, predators would often catch tasty individuals and would stop avoiding the warning pattern.

In 1878, the German zoologist Fritz Müller described a different arrangement. He observed that several poisonous species sometimes share nearly identical color patterns. In this case, no species is cheating. By adopting a common signal, the species share the cost of “teaching” predators, since fewer individuals of each species need to be eaten before the lesson is learned. Müllerian mimicry therefore represents cooperation rather than deception.