How do painted lady butterflies travel such long distances?

LEILA FADEL, HOST:

Butterflies are traveling across the Atlantic from West Africa. It's one of the longest insect journeys ever recorded.

STEVE INSKEEP, HOST:

These are painted lady butterflies. Gerard Talavera came across about 10 of them in a place he did not expect. He's a senior scientist at the Botanical Institute of Barcelona in Spain.

GERARD TALAVERA: We found butterflies of this species in South America, which is a continent where this species does not occur. There's no evidence for reproduction or for established populations that live there, and that was the beginning of this scientific journey for us.

FADEL: The butterflies looked worn out, with tattered wings.

INSKEEP: As mine would be.

FADEL: Yeah, far.

INSKEEP: Anyway, go on.

FADEL: Talavera figured the butterflies must have traveled an extremely long distance - but how? It was a research challenge.

TALAVERA: There are plenty of butterflies that are migratory by nature, but we are just starting to know what is the extent of these trips. There's no technology out there that allows us to learn what we just have learned about this transoceanic journey. We cannot put GPSes or radio trackers on these insects.

FADEL: So the scientist looked at wind conditions.

TALAVERA: The first thing I did was to try to model the winds, and when I saw that the winds were great from Africa, then I clearly saw that this was a strong hypothesis to test.

INSKEEP: Talavera had a partner in this research - Megan Reich, a postdoctoral fellow at the University of Ottawa.

MEGAN REICH: We think that as they were approaching sub-Saharan Africa, they got swept by the wind over the Atlantic Ocean, and then finding themselves over the ocean, they had no choice but to continue with the wind until they found land, which was South America.

FADEL: Sometimes, you've just got to go where the wind takes you.

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