A once-in-decade phenomenon of millions of brightly-coloured butterflies arriving in Ireland after an epic inter-generational journey from north Africa is starting to happen every year.
Painted ladies, one of the largest butterflies in the country, are landing in “massive numbers” on the fringes of the north of the island — Donegal and Down — as well as Dublin and Wicklow over recent days.
Experts are urging people near the coast to watch out for the spectacle as thousands at a time descend in a kaleidoscope of colour as they make landfall on Irish shores, seeking out wild plants and seaside gardens to feed on.
But they are also warning of a “very unusual” pattern this year, which defies records going back to the 19th century.
Jesmond Harding, one of Ireland’s foremost butterfly experts, said the once ten-year cycle of mass influxes of the species — also known as Vanessa cardui — has been disrupted as large numbers have arrived in each of the last three years.
“This is very, very unusual. This is new,” he said.
From the 1800s until 2017, one vast arrival of painted ladies could be expected roughly every ten years. The year after the big swarm, there would be a total collapse in their population.
They would usually descend around May or June, having started their journey in the likes of Morocco, where after a large build up, a millions-strong flutter would fly — hundreds of kilometres a day — in strong southerly winds to central Spain.
After breeding there, the next generation would fly on to northern Europe, including Ireland and Britain.
“This year is very unusual, there has been a succession of arrivals,” said Mr Harding, who runs Butterfly Conservation Ireland.
“I can’t remember it ever happening before, and never in winter.
“We had them coming in large numbers in the middle of January, and parts of February. Then we had them in late June and early July. Now we have them in late July, early August.
“This is also the third year in succession we have had big numbers of painted ladies , and this year is bigger than the previous two years.
“It is certainly signalling some sort of change, either in the species itself, or in climate.”
Mr Harding said the reasons for the unusual migration pattern will become clearer in the coming years “but it seems that climate change is responsible” as hotter, dryer conditions in the south leave no vegetation for the butterflies.
“I think they are following the food,” he said.
A “massive front” travelling via Scotland landed on the Donegal coastline last week, where a Tory islander described them as “like an amazing carpet” of butterflies. In Kilteel, Co Down, a man reported around 100 painted ladies feeding on verbena and lavender in his garden.
“Very big numbers” were spotted on the Dublin and Wicklow coast over the weekend, Mr Harding said.
He added the spectacle should last another week or two.
“If you are on the coast at the right time in the coming days, you could be lucky enough to see great clouds or carpets of hundreds or thousands of painted ladies,” he said.
“When you see a mass of them, it is really amazing to look at. It is breathtaking.”