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Secrets of the Monarch Butterfly

Scientists think they know why monarch butterflies have white spots on their wings.

A profile of a monarch butterfly on an orange and yellow flower.

© Marilyn Gould/

Why do monarch butterflies have white spots on their wings?

Monarch butterflies are beautiful! Their orange, black, and white wings look like they were painted by a talented artist. But scientists say the white spots on a monarch’s wings aren’t just pretty. They may help the monarch fly.

Each fall, some monarch butterflies migrate (travel) from Canada and the United States to Mexico. They spend the winter in the warmer climate. In the spring, they fly north again. The trip is about 2,000 miles (3,200 kilometers) each way. That’s a lot of distance to cover, especially for a tiny butterfly. Scientists wanted to know how monarch butterflies are able to fly all that way.

Scientists studied the monarch butterflies that were able to make it all the way to Mexico and those that were not. They found that the successful flyers had more white spots on their wings. Scientists also studied types of butterflies that do not migrate. These insects had smaller white spots than migrating monarchs.

The scientists think the white spots help monarchs because they cause sunlight to heat the wings differently in different places. This changes the airflow around the wings, making it easier to fly.

© Jose Carlos Macouzet Espinosa—Creatas Video+/Getty Images Plus

These monarch butterflies migrated to Mexico, where it’s warm.

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Fun Fact

© Andreistanescu, Patricioj/, © Linda McKusick/; Photo illustration Encyclopædia Britannica, Inc.

The temperature needs to be at least 55 degrees Fahrenheit (13 degrees Celsius) for a monarch butterfly’s wings to be warm enough to fly.

Butterflies Need Milkweed!

© Danita Delimont/

This caterpillar eats just one thing.

Monarch butterflies start out as caterpillars, which eat only one thing: the leaves of the milkweed plant. In the U.S., people can help monarch butterflies by planting milkweed in their yards!

But be sure to plant the right kind of milkweed. Experts say it’s best not to plant tropical milkweed. Tropical milkweed continues to bloom in the fall, so monarchs want to be around it when they’re supposed to be flying to Mexico for the winter. Many monarch butterflies need to fly south for the winter because they will not survive in the cold weather.

A Long Journey

© Uryadnikov Sergey, thawats/, © Buddhapong Wongsanont, Brian Magnier/, © doescher—iStock/Getty Images Plus; Photo illustration Encyclopædia Britannica, Inc.

Some animals travel a long way to reach their winter homes. There’s a lot more to learn about migration!

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Word of the Day


Part of speech:



used to make something more attractive : used for decoration

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Can you find all the different types of butterflies?


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