Discovery of mass migration and breeding of the painted lady butterflyVanessa carduiin the Sub-Sahara: the Europe-Africa migration revisited

Abstract

Migratory behaviour has repeatedly evolved across taxa as an adaptation to heterogeneity in space and time. However, insect migration is still poorly understood, partly because of the lack of field data. The painted lady butterfly Vanessa cardui undertakes a long-distance annual migration between Europe and Africa. While spring flights from the Maghreb to Europe are well characterized, it is not known how far the European autumn migrants travel into Africa and whether they massively cross the Sahara Desert. We conducted fieldwork in four African countries (Chad, Benin, Senegal, and Ethiopia) in autumn and documented southward migrants in central Chad and abundant breeding sites across the tropical savannah as far south as the Niger River in the west and the Ethiopian highlands in the east. Given directionality and timing, these migrants probably originated in Europe and crossed the Mediterranean, the Sahara and the Sahel, a hypothesis that implies the longest (>4000 km) migratory flight recorded for a butterfly in a single generation. In the light of the new evidence, we revise the prevailing spatiotemporal model for the annual migration of V. cardui to incorporate tropical Africa, which could potentially be regarded as the missing geographic link between autumn (southwards) and spring (northwards) movements.