Painted lady butterfly takes one of longest insect journeys ever recorded

One autumn week about a decade ago, Gerard Talavera spent several days patrolling a beach in French Guiana in search of what he called “the impossible”—a painted lady butterfly.

With tiger-like colorations, painted ladies are common insects in Europe, Africa, Asia, North America, and even Australia. However, the species is not native to South America.

And yet, from time to time, people claim to see them there.

“It was my last day, and suddenly I saw something jumping in the sunlight,” says Talavera, an entomologist and evolutionary biologist at the Botanical Institute of Barcelona in Spain and a National Geographic Explorer.

“I couldn’t believe it, but it was a painted lady.” (See stunning photos of butterflies around the world.)

Interestingly, the insect was not alone—after Talavera got out his net, he observed nine other painted ladies, each with tattered wings, fluttering about the beach. How did these two-inch, seemingly fragile insects arrive on a coast thousands of miles away from their home, outside their known migration route?

More than a decade later, Talavera and his team appear to have solved the mystery.

Using a first-of-its-kind analysis of wind patterns, pollen samples, genomes, and more, the scientists believe the butterflies flew from West Africa after hatching in Western Europe—meaning they flew a total of around 4,300 miles in less than a month, one of the longest nonstop flights ever recorded for individual insects.

It may also be the first verified account of an individual insect crossing the Atlantic Ocean, says Talavera.

All of which begs the question, how many other insects may be making similar journeys without us noticing?

“We are probably overlooking what is happening in terms of long-range migration,” says Talavera, lead author of the study published today in the journal Nature Communications.

Detective work 

Previous research suggested painted ladies have a maximum range of about 500 miles for nonstop flight with no wind. But when Talavera analyzed wind patterns from the days leading up to his observation on the beach, it showed the painted ladies could have hitched a ride from Africa across the Atlantic.

However, to do so, the butterflies must have been alternating between flapping and gliding on wind currents—something other migrating butterflies such as monarchs do but has previously not been recorded in painted ladies.

“It’s evidence, but it’s not proof,” says Talavera. (Related: Monarch butterflies migrate 3,000 miles—here's how.)

Genomics seemed like a logical next step. After looking at painted lady DNA samples from North America, Europe, and Africa, the scientists ruled out North America—the closest location to French Guiana—as a source population.

To add still more evidence, the scientists isolated DNA from some of the pollen grains stuck to the butterflies’ wings, which in turn identified plants they had visited before coming to South America. Most of the dozen or more plant species had wide ranges, which didn’t help much. 

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However, two species—Guiera senegalensis and Ziziphus spina-christi—only flower at the end of the rainy season in West Africa. In other words, the proof was in the pollen. (Related: These mysterious moths fly at night in a straight line—but how?)

Not stopping there, next the team evaluated isotopes, or different varieties, of atoms in the elements hydrogen and strontium in the South American butterflies’ wings, which confirmed they were all born in roughly the same place.

Using all the isotopic information, the team modeled ecosystems that would provide suitable habitat for the insects, which pointed to the United Kingdom, Ireland, France, Portugal, Mali, Senegal, and Guinea-Bissau.

Put all together, the scientists conclude with a high degree of certainty that the painted ladies hatched in Western Europe before traveling to West Africa. They then spent five to eight days gliding over the Atlantic on favorable winds before landing on the South American coast, where Talavera found them. (Learn more about painted ladies' migrations between Africa and Europe.)

“Combining these techniques is really helping and is getting us to places where we couldn't go before,” he says.

A “really elegant” study

“I just think this paper was really elegant,” says Jessica Ware, curator and division chair of Invertebrate Zoology at the American Museum of Natural History in New York City. You can “see the whole story.”

Ware studies the globe skimmer dragonfly, which regularly migrates between India and East Africa, crossing the Indian Ocean and around 3,700 miles in the process. 

“For most insects, saltwater is death, right?” says Ware, who was not part of the new research. “So it’s always interesting when you can kind of show with some type of evidence that they are actually migrating.” (Learn about an Alaska bird that made the longest recorded flight.)

Ware was particularly impressed with Talavera and colleagues’ analysis of pollen, which she says raises still more questions. Namely, if insects and pollen are traversing the Atlantic, then there is potential for a plant to pollinate itself far from its original source.

“It just surprises me that we’re kind of at the infancy of understanding this pretty basic behavior. ‘Do things migrate across this ocean, yes or no?’” says Ware.

“It’s 2024, and we’re still getting discoveries like this, which is really exciting.”