That's an Imposter!

By Tom Allen, Contributing Editor

Imitation is the sincerest form of flattery. If that phrase is true, then the monarch and pipevine swallowtail have it made. Both of these popular flying flowers are toxic species other butterflies imitate.

This behavior, known as Batesian mimicry, has developed over time. It is an evolutionary process whereby a species changes its color or pattern through genetic mutation to closely resemble a toxic species. Butterflies are just one of the insects that use this behavior.

They do this for protection. Other than their look-alike technique, these butterflies have no defense against predators. If they resemble a toxic butterfly, then they have a better chance of surviving and passing their traits to offspring.

Model Behavior

When it comes to understanding mimic butterflies, you must first look to their source. For instance, the toxic butterfly that another butterfly copies is the source model.

Predators recognize toxic butterflies because of their warning colors, which often consist of black, yellow, white and red combinations. These colors provide maximum visibility against the greens and browns of natural habitats. It's like sending a big warning sign to predators.

Viceroy photo: Paula A. Smith

One of the most common examples of mimicry behavior is that of the viceroy butterfly. It looks and behaves like the monarch, which feeds on the toxic milkweed plant. It wants to fool predators into thinking it is also toxic, so the viceroy appears at the same time of year as the monarch and uses similar habitats.

The queen and soldier butterflies also resemble the monarch, but they are not mimics. They feed on milkweed and therefore are toxic, so they are yet another model for the viceroy.

Since viceroys are found throughout most of North America, the butterflies have different options. In the northern part of the United States, the orange and black fliers mimic the monarch. Farther south, they tailor their look after the queen and soldier butterflies, which have slightly different coloring in certain regions.

For example, I live in Florida, and queen and soldier butterflies are much darker brown than monarchs. Because of this, the viceroys here have evolved to a darker coloration pattern to give them even better protection against predators in their natural habitat.

Pipevine Impersonator

The Diana fritillary, the red-spotted purple, the spicebush swallowtail and female tiger swallowtail all mimic the chemically toxic pipevine swallowtail. Since the pipevine is found from the central U.S. southward, these mimics—at least the black forms—are in the same region.

In northern states, female tiger swallowtails remain yellow, since pipevines don't exist in that region. But the true mimics of pipevines use similar woodland habitats within their range and fly during similar periods of the year.

The female Diana fritillary is a rare and beautiful woodland butterfly that is truly dimorphic, meaning the males and females look very different. For years, it fooled scientists into thinking that the males and females of the Appalachian species were two different butterflies.

These unique butterflies live in moist and shaded woodland habitats in the Appalachian and Ozark Mountains. Their only form of protection is to mimic the pipevine.

So the next time you think you see a pipevine swallowtail or monarch, be sure to take a closer look. You could be looking at a different species altogether!