Unusually Large Butterfly Migration Reaches Sweden

You can now spot rare large swarms of painted lady butterflies across Sweden. This offers residents in Stockholm a great chance to observe wildlife in local parks. Researchers at the University of Gothenburg reported this unusual migration. The butterflies travelled all the way from North Africa and Southern Europe.

Painted lady butterflies cannot survive Swedish winters. They migrate north to Sweden every year. In 2026, unusually large numbers arrived. Similar big migrations happened before in 2009 and 2019. Heavy spring rain in North Africa helped them reproduce. Warm European weather then aided their flight north.

A new study in Nature Ecology and Evolution shows global butterfly ranges are changing. Researcher Patrice Pottier and an international team analyzed 1,758 butterfly species across 105 countries. Nine out of ten species have shifted their geographical locations. Rising temperatures push many species further north or to higher ground.

To spot painted ladies, check local parks for thistles and mugwort. Females lay eggs on these plants in Sweden. You can report sightings to the Swedish Species Observation System called Artportalen. You can also use the app iNaturalist to share your findings.