"To figure out how the painted ladies ended up in French Guiana, researchers approached the question from many angles. They looked at weather data for the weeks leading up to the butterflies’ arrival and saw that wind conditions could have supported a voyage from Africa to South America.

They also sequenced the butterflies’ genomes and learned that they were relatives of insects from Africa and Europe, which helped them rule out the possibility that the migrants had flown from North America. In addition, they analyzed isotopes in the butterflies’ wings, which can point to their area of origin—this suggested they were born in western Europe and western Africa.

Providing yet another line of evidence, the team sequenced the DNA of pollen grains stuck to the butterflies’ bodies. This allowed them to identify the plants the creatures had recently visited—Guiera senegalensis and Ziziphus spina-christi, two shrub species that only flower at the end of West Africa’s rainy season."