Learn ‘Why Butterflies Need Volcanoes’ during online program Feb. 28

The recent announcement of a dramatic decline in this year’s population of overwintering monarchs has increased interest in knowing more about the challenges the butterfly faces during migration and in the months spent in the fir forests of Mexico.

It is common practice to define the eastern monarch’s life cycle as egg, caterpillar, pupa and adult but it can also be described as a mix of geography and season: breeding in the Midwest during the summer, a cross continental fall and spring migration, and surviving winter in Mexico.

Each of these stages weaves together varying weather patterns within diverse habitats.

Scientists believe this year’s low monarch count was the result of an unusually hot and dry autumn in the southern U.S. states. Nectar sources weren’t sufficient for sustaining the butterflies on the long, arduous migration south. Fewer were able to complete it.

Eastern monarchs migrate to the mountains of the Trans-Mexican Volcanic Belt but what lures prairie butterflies across long distances to these mountains?

Once there, they spend the winter at high altitudes with temperatures between 32° and 59°F. They’re in diapause, a state of suspended development and reduced metabolic activity.

To keep warm, thousands of butterflies cluster together on a single tree. There is a delicate balance between staying cool enough to limit flight and warm enough not to freeze.

Emily Stone, a naturalist and director of education for the Cable Natural History Museum in Wisconsin, describes the interactions of temperature and humidity sustaining the butterflies as a “tangle of relationships” unspooling while the climate changes around them.

During a trip to the monarch sanctuaries in December 2022, Stone had a close look at the monarch’s unique cold weather survival strategy requiring a flight of over a thousand miles and spending months in a chilly forest.

On Wednesday, Feb. 28, hear more about how monarchs make it through the winter and experience the astonishing sight of millions of monarchs at “Why Butterflies Need Volcanoes,” a virtual program hosted by the DuPage Monarch Project and River Prairie Group of the Sierra Club.

It will begin at 7 p.m. via Zoom. Register via

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