The painted lady is an orange and black migrating butterfly present in most of the world. Every summer, populations of these butterflies can be found in Western Europe where they arrive after migrating across the Sahara from Western Africa. However, the number of butterflies that arrive and are later born in Europe is as much as 100 times higher in some years than in others. Researchers from various universities in Europe and Asia recently studied what determines that painted lady population each year.

The researchers modeled possible routes the butterflies could take from their starting point in West Africa to get to Europe and noted that the most successful routes had experienced high levels of rainfall during the monsoon season before the butterflies made their migration. This high level of rainfall allowed an increase in plant growth. Since painted lady butterflies only live for a couple of weeks, they need to stop and breed during the annual migration, leaving their children to continue the flight northward. Increased level of plant growth allowed the adult butterflies to find very specific areas to lay their eggs and provided plenty of nutrients for the larvae to grow on once they were hatched. Ultimately, this meant a greater number of mature butterflies finished the migration and arrived in Europe.

Rainfall patterns in West Africa and the Sahara are changing with climate change, and researchers note that this may impact the migratory behavior of painted lady butterflies in ways that affect how many make it to Europe. This is an important topic that may be studied in the future. For now, however, the researchers note that finding the drivers of this migration between Africa and Europe may help explain what influences painted lady migrations in the rest of the world.

Gao Hu studies insect migration at Nanjing Agricultural University

Managing Correspondent: Emily Kerr

Scientific Article: Environmental drivers of annual population fluctuations in a trans-Saharan insect migrant

News Article: Rain in sub-Saharan Africa can mean more butterflies in Europe

Image Credit: Painted Lady Butterfly by Creativity+ Timothy K Hamilton

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