Thanks to a monarch butterfly in Northfield, Minn., researchers in central Mexico are reconstructing the journey of the monarchs from this area to their winter habitat.

The University of Kansas has been handing out small stickers marked with an email address, phone number, and unique identification code, and asking people to attach them to the discal cell on the butterflies’ wings. Then record the date and location.

That’s what Julianne Moore, of Northfield, did in her backyard last September, according to Atlas Obscura. It was the second year she’s taken part.

Several years ago, she saw a butterfly emerge from a chrysalis while she was hosting a garage sale. Soon after, she moved the daylilies she’d salvaged from her mother’s garden to make room for a patch of milkweed. Before long, she was even ushering caterpillars into little screened habitats, where they could safely complete their metamorphosis and emerge from a chrysalis, wet and vulnerable. Once they’re dry, she takes them out, holds them gently by the wings, and applies a sticker. (Her grandson gifted her a magnifying glass to assist in the delicate work.) “Then I set them on some flowers around the deck,” she says. “They sit out there for a while, and off they go.”

On a trip Atlas Obscura hosted to the Montane Forest of central Mexico a little over a week ago, biologist Phil Torres found Moore’s butterfly.

Does anyone know a Julianne Moore from Northfield, MN?

We found the butterfly she tagged up there on Sept 2, it made the journey over 2,000 miles away to Mexico! https://t.co/8eV4B9d8gX — Phil Torres (@phil_torres) February 27, 2019

Moore spotted the tweet and confirmed the monarch was from her backyard, the 40th of about 100 she tagged last year. This one, however, is the only one of hers that’s been found.

“I’m greedy enough that I’m hoping that when the rest of the reports come out, [there] may be more,” Moore said from Florida, where she spends the winter handing out milkweed seeds to her friends.

Of the 1.4 million monarchs that have been tagged, just one-tenth of one percent have been located.

“You have to spot one with a tag out of the millions of living and dead butterflies in visual range, which of course doesn’t include those that are too high, or buried beneath other dead ones, or perhaps dead but with the tag on the face-down side, or clustered on a tree not in visual range of the trails you’re allowed to be on,” says Jason Goldman, a science journalist and organizer of the Atlas Obscura trip.

Next winter, the monarchs who arrive in Mexico will be the great-great grandchildren of the ones who are there now.