Research Exposes Myth on Butterfly Coloring : Evolution: Century-old belief is discredited. It held that viceroy butterfly avoids being eaten by mimicking coloration of two kinds that birds dislike.

The long-held notion that the tasty viceroy butterfly escapes being eaten by birds by mimicking the coloration of foul-tasting monarch and queen butterflies has been overturned by two Florida biologists who tested the century-old belief experimentally.

They report in today’s edition of the British journal Nature that they tore the wings off all three types of butterflies and fed their bodies to red-winged blackbirds for a novel taste test.

To their surprise, the researchers found that the monarch and the viceroy butterflies were equally distasteful to the birds and that the queen butterfly--supposedly the object of mimicry--actually tasted better than the other two.

The results undermine a theory that has been part of standard biology textbooks for decades, and they suggest that this form of mimicry occurs far less in nature than had been thought.

The findings also suggest that entomologists will have to rethink the nature of the relationship among the different species of butterflies. The classical explanation for their relationship has been that the viceroy benefits at the expense of both the monarch and queen butterflies (which it mimics) and the birds (which it deceives).

In the new view, said Florida biologists David B. Ritland and Lincoln P. Brower, all three species benefit. The predator more quickly learns to avoid the foul food, because every time it eats a butterfly of that coloring it tastes awful. Fewer butterflies of any single species die because the damage is shared among the three species.

“There have been indirect indications or suggestions that the viceroy is not as palatable to birds as the general dogmatic theory would lead you to believe,” said population biologist Austin P. Platt of the University of Maryland, Baltimore County. “But Ritland and Brower have documented it in a much more intensive way than it was previously. It’s very, very important work.”

The idea that one species can mimic another in appearance, smell, feel or sound to escape predation was developed in 1862 by British biologist Walter Henry Bates. The theory is “one of the most enduring notions of evolutionary biology,” according to entomologist Richard I. Vane-Wright of the British Museum of Natural History.

Bates’ idea that a tasty butterfly could escape predation by mimicking the coloring of a distasteful species was based on a study of Amazonian butterflies. Because of his work, the concept was termed batesian mimicry.

But Bates never studied the classical example of batesian mimicry that is used in virtually every introductory biology text, the viceroy and monarch butterflies. In fact, until recently, no one did.

Nevertheless, most American scientists assumed the species fit the batesian mold.

It may seem amazing that no one has ever attempted to study the taste of the butterflies. “But it’s not amazing if you sit down and try to do it,” Ritland said. Dismembering the butterflies, feeding their torsos to the birds and monitoring the birds’ behavior is tedious work, he said. “Brower had been wanting to do it for a long time, but couldn’t convince anyone to do it.”

Ritland, a graduate student, finally agreed. He fed torsos of all three butterflies, as well as a “tasty” butterfly that the birds normally feed on, to the birds and charted whether they ate them and how long they manipulated them if they did not eat them. From these studies, he concluded that monarchs, viceroys and queens all were distasteful.

Some researchers who haven’t performed the experiments, meanwhile, have argued that batesian mimicry is unlikely in the vast majority of cases.

“Is it not more likely that an unprotected species will develop its own defenses . . . rather than merely simulate the appearance of another?” Vane-Wright wrote in an editorial in today’s Nature. “Bluff, with no stick to wield when challenged, is a risky sort of defense.”

Furthermore, batesian mimicry is harmful to the species being mimicked, Ritland said. “Monarchs and queens depend on predators learning to avoid them. If the viceroy is tasty, it confuses that learning process, so more monarch and queen butterflies are consumed before the bird learns to avoid them.

Evolutionarily, it would make sense for the monarch and queen to “evolve new color patterns to escape from the viceroy,” Ritland said. But scientists have been unable to document such escapes, he noted.

Based on the new research, Vane-Wright said, “batesian mimicry may be much rarer than expected.” Nonetheless, it does exist. The Amazonian butterflies studied by Bates are still the best example, and there are several others in the insect world. Unfortunately, textbook writers have chosen the wrong example in the monarch and viceroy butterflies. “It’s one of the great half-truths of modern biology,” Platt said.