Each year painted lady butterflies cross the Sahara — and then go back again

Move over, monarchs. The painted lady butterfly (Vanessa cardui) now boasts the farthest known butterfly migration.

Though found across the world, the orange-and-brown beauties that live in Southern Europe migrate into Africa each fall, crossing the Sahara on their journey (SN Online: 10/12/16). But what happened after was a mystery because the butterflies disappeared. Researchers hypothesized that the insects either remained in Africa or made a round-trip, but there was no evidence either way.

A new chemical analysis of butterfly wings suggests that the butterflies head back to Europe in the spring. The round-trip, which usually plays out over several generations, is an annual journey of 12,000 kilometers, about 2,000 more than successive generations of monarchs are known to travel in a year (SN: 4/14/18, p. 22).

Researchers were surprised when they detected chemical markers from Africa on some European butterflies’ wings. Those markers told where an individual had eaten when it was still a caterpillar. The study, reported in the June 13 Biology Letters, provides evidence that the creatures return from Africa each year. Some tenacious individuals even make the return trip in a single lifetime.