The United Kingdom is currently experiencing a rare 'painted lady summer,' with millions of migratory butterflies arriving and breeding, according to wildlife charity Butterfly Conservation. This event, which occurs approximately every ten years, sees large numbers of the distinctive orange, black, and white patterned butterflies flock to the UK.
Warm weather across Europe this spring is believed to have prompted the mass migration. Clouds of painted ladies have been observed feeding and mating in various locations, and their offspring are now emerging nationwide. This year's numbers are already significantly higher than last year and even surpass those recorded at the same point in 2019, suggesting this painted lady summer could be the most substantial on record.
Conservationists are urging the public to participate in the annual Big Butterfly Count by recording sightings of painted ladies. This initiative helps experts monitor butterfly populations and their health.
The migration undertaken by painted lady butterflies from sub-Saharan Africa to Europe is one of the longest insect journeys globally. It is a multi-generational undertaking, meaning the butterflies that leave Africa are not the same individuals that arrive in the UK to breed. Butterflies born in sub-Saharan Africa during winter migrate to north Africa, where they mate and lay eggs. Their offspring then travel across the Mediterranean to southern Europe, where they also mate and reproduce. The generation that hatches in southern Europe then makes the final journey to the UK in late spring.
Butterfly Conservation reports that this year is on track to be among the top three best years for painted lady numbers, potentially rivaling or exceeding the records set in 1996 and 2009. Last year, only 15,856 painted ladies were reported during the Big Butterfly Count, a stark contrast to the over 420,000 recorded during the previous painted lady summer in 2019.
"The inter-continental migration of painted lady butterflies is a wonder of the natural world and one of the longest insect journeys on the planet," said Professor Richard Fox, head of science at Butterfly Conservation. "The numbers we're seeing here at the moment have already dwarfed the total number of painted ladies we saw last year, and we're absolutely delighted."
These butterflies, known for their striking wings, are a popular species among the public. The new generation emerging across the UK is preparing for the next stage of their migratory journey. "Helping to count them is a great excuse to take part in this year's Big Butterfly Count," Professor Fox added.
Painted lady butterflies feed on various flowers, including buddleia, and their caterpillars primarily consume thistles. Abundant populations of these insects can help control invasive creeping thistle plants.
While the exact reasons for these periodic painted lady summers are not fully understood, they are linked to successful breeding seasons in Africa and southern Europe earlier in the year. Factors such as food availability, predator numbers, and favorable weather conditions, including this year's heatwaves, contribute to the boom years for these insects. "It's astonishing that such a seemingly delicate insect can accomplish this incredible long-distance journey," commented Kate Merry, head of engagement at Butterfly Conservation. "We've already seen absolutely loads of them across the UK, so we are very excited to see how many people report them and where."
The Big Butterfly Count runs until Sunday, August 9. Participants are asked to spend 15 minutes in a sunny outdoor location, such as a garden or park, and record their butterfly sightings. Information and participation details are available through the Big Butterfly Count app or at bigbutterflycount.org.