We’ll be seeing huge numbers of colourful migrants in the UK this summer – in what is widely predicted to be the largest arrival of painted-lady butterflies for 17 years.
“We are in the midst of a miracle”, said wildlife writer Simon Barnes in The Observer. Last time there was a painted-lady spike, in 2019, they were seen in their hundreds of thousands. Clouds of the butterflies have already been spotted, as Butterfly Conservation’s annual Big Butterfly Count – the world’s largest citizen-science insect count – gets under way. Large numbers have been recorded along the east coast into northern England and, at Hickling national nature reserve, close to the Norfolk coast, 253 of them have been seen feeding on one patch of brambles.
What are painted ladies?
Formally known as Vanessa cardui, they are medium-sized orange butterflies with black markings and, on their forewing tips, white spots on a black background. Every year, in a spectacular long-distance migration, they fly from the desert fringes of North Africa, the Middle East and central Asia to mainland Europe and then Britain and Ireland. Then in September, they fly south again, completing a 9,000-mile round trip and one of the world’s longest insect journeys. “They can move from egg to adult in less than six weeks,” said Barnes in The Observer, so it might take “three or four” generations to reach the UK.
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In an average year, the number of painted-lady arrivals in the UK hovers around 15,000, although, some years, hardly any reach our shores. But butterfly experts are confidently predicting such a surge in numbers this year that we’re in for “a once-in-a-decade ‘painted lady summer’”, said The Guardian.
Why are numbers spiking?
It’s down to a combination of “favourable early spring conditions in southern Europe”, the recent heatwaves and “benign southerly winds”, said The Guardian. Sightings have been increasing for several weeks but “there’s been a big recent immigration” in the past week, Dan Hoare of Butterfly Conservation told the paper. Painted ladies “grow extremely fast, feed easily and fly really well” and, after breeding particularly successfully during heatwaves in France and Spain, they have benefited from “favourable winds to get them across the Channel”.
The last time this happened, in 2019, more than 420,000 painted ladies were recorded in the UK. But that most recent summer spike pales in comparison to the record year of 2009, when more than two million painted ladies arrived in the UK over a two-day period in May. Over the course of that summer, there were a “barely credible” billion British painted ladies, said Barnes in The Observer.
What about wider butterfly numbers?
In marked contrast to the excitement about the “painted-lady summer”, butterfly numbers in the UK have long been decreasing, according to Butterfly Conservation. Sightings hit record lows in 2024, although there was “improvement” in 2025. Climate change, habitat loss, pollution and plant pesticides have contributed to a picture where more than three-quarters of butterfly species are in decline.
Warnings about the “fragility of nature in the 21st century” are the “naturalist’s lot”, said Barnes in The Observer. But the “awe and disbelief” that will no doubt greet this year’s painted-lady numbers are “symbols of hope”. The bumper success of that butterfly’s 9,000-mile intercontinental journey is a reminder that “if you give nature even the fragment of a chance, it’s always avidly seized”. If the “right decisions” are made, at local, national and international levels, British butterfly “recovery is still possible”.
