Populations of migratory monarch butterflies have decreased by an estimated 90% since the mid-1990s due to the loss of natural habitat along their migration route from the northern U.S. to southern Mexico.
"Missouri has 0.3% or so of our native prairies remaining that were filled with wildflowers 100, 200 years ago," said Tad Yankoski, senior entomologist at the Missouri Botanical Garden Sophia M. Sachs Butterfly House. "[Monarchs] need a lot of snacks for a migration that far, and they need to fuel up and get that energy from wildflowers."
In an effort to boost the species' population, tens of thousands of people are now raising monarchs in captivity — a practice that has Yankoski concerned. He said research shows that captive raised monarchs are weaker and smaller, on average, than their wild counterparts.
"As a result, they're starting at a pretty severe disadvantage to be able to complete that migration," he said. "You also need to be very careful about diseases and pathogens, so that if you are releasing them back into the wild, you're not exposing wild-bred monarch butterflies to those pathogens as well.
Yankoski said research suggests that monarchs' ability to migrate starts when they are in the chrysalis. Bringing them indoors can disrupt that process.
"Day length changes is one of the factors that will tell a monarch butterfly when it's time to fly south," he said. "If they get programmed by internal lighting as opposed to the sun outside, that can interfere with their internal clocks."
The argument over whether raising monarchs in captivity helps or hurts the species is one that St. Clair resident Cheri Firehammer is intimately familiar with. As the founder of the Marvelous Monarchs of Franklin County MO Facebook page, she hears from both sides of the debate.
"I started this Facebook group as a way to get other people interested in learning about monarchs and why it's so important to take care of them, whether it's raising them or just planting milkweed," she said. "Some people will say their way is the right way, and some people will say, 'This way is the right way.' I think there's a [middle ground]."
Firehammer has released more than 200 monarchs since she began rearing them in mesh enclosures three years ago. She spends several hours a day cleaning their enclosures and providing them with fresh, native milkweed and nectar-rich flowers.
"I take very good care of them. It's like having a pet," she said. "I would rather have them just out in nature, doing what they do naturally, but I have seen so many of them disappear in my backyard."
One thing both camps can agree on is that the most effective way to support monarch butterflies is to plant milkweed — the only plant on which monarchs will lay their eggs and the only plant monarch caterpillars will feed on.
"If you want to support native wildlife, you need to provide them with the native plants that they've interacted with for thousands of years," said Missouri Botanical Garden horticulturalist Caitlin Jackson. "And then most importantly, during the fall migration, they need to have nectar. There's not a lot of popular fall-blooming annuals, so having those natives like goldenrod and aster that bloom very consistently in the fall are important."
Jackson added that now is the best time to plant seeds for a monarch-friendly garden in the spring, and next summer is a good time to plant for the 2027 fall migration.
"There's lots of species of milkweed, and all of them work well," Jackson said, with one caveat. "The only one that we don't recommend is tropical milkweed, because there is some research that shows that when monarchs encounter tropical milkweed in this region, it can screw them up."
Monarch butterflies will migrate through St. Louis until mid-October, traveling during the daytime and roosting at night.
For Firehammer, it's an experience like no other.
"It's just beautiful to watch them flying," she said.
To learn more about monarch butterfly migrations — including the fact that no monarch making the trip has ever done it before (it's their great-great-great-grandparents who last flew the route!) — listen to "St. Louis on the Air" on Apple Podcasts, Spotify, YouTube or click the play button below.
"St. Louis on the Air" brings you the stories of St. Louis and the people who live, work and create in our region. The show is produced by Miya Norfleet, Emily Woodbury, Danny Wicentowski, Elaine Cha, Darrious Varner and Alex Heuer. The audio engineer is Aaron Doerr.
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