Will this be a 'painted lady summer'?

 

This spring was notable for an early influx of migrant painted lady butterflies that arrived here on warm southerly winds, raising hopes that this might be a 'painted lady summer'.

They began to appear in Weardale in substantial numbers towards the end of the heatwave in May but were reported in southern and western counties from mid-April onwards. There has long been speculation that these early arrivals fly here directly from North Africa. The tattered state of the butterfly in the photo above, nectaring on sweet rocket aka dame's violet Hesperis matrionalis in my garden, suggests that it might have had a long and eventful journey.

L. Hugh Newman, whose family ran a butterfly farm in Kent (that supplied Winston Churchill with butterflies for his garden at Chartwell) kept detailed records of their lifespans. Resident breeding species typically had lifespans of less than a month , with the exception of those that overwintered as adults (10-11 months for brimstone, small tortoiseshell, peacock) and found that 30 days was the maximum lifespan of painted ladies. They are known to fly at night and with a favourable wind, they are reckoned to fly about 150km. per day, so it’s just conceivable that some early spring arrivals here might have made the one-way journey directly from North Africa, but there’s no doubt that the true test of whether we are due a ‘painted lady summer’ depends on their breeding success at various locations in continental  Europe, and favourable summer winds.

Most arrive in relays, crossing the Mediterranean to breed in France and Spain first. With their short life cycle - egg to imago in six weeks - their numbers multiply exponentially as they move northwards, a rolling wave of butterflies that reaches our shores in mid- summer.

Spectacular ‘painted lady summers’ are the stuff of lepidopterists’ legends. I recall walking along the coast near Whitby in 1996, surrounded by hundreds of painted ladies settling to feed in flowery cliff-top grassland. That invasion reached Orkney and Shetland. The most recent mass migration that I remember here was in 2009, but size and frequency of such events are subject to favourable winds and clement weather.

 

Painted Ladies

Lately a few painted lady butterflies have begun to appear in Teesdale and Weardale, wafted in by warm winds from the south. It's nothing like the spectacular invasion we enjoyed in 1996, when the first arrivals appeared in early July and bred on thistles to produce a second generation, so that there were enormous numbers by early autumn. Sometimes late invasions arrive in early autumn, as they did in 1903 (see below).

Painted ladies are noted for their infrequent but spectacular invasions and some of the largest of these, according to F.W. Frohawk in his Complete Book of British Butterflies published in 1934, coincided with wet summers in 1879 and 1903. 

This is how Frohawk described them:

"In 1879 the first migratory swarm appeared in North Africa in the middle of April. At Barcelona and Valencia enormous numbers occurred at the end of April and reached the island of Minorca on the first three days of May. On June 15th. vast swarms passed over Sevres, flying all day in a north-westerly direction. Similar flights were seen at Strasburg passing in countless numbers to the north, At Angers, on June 10th., an immense swarm flew over the city; it was estimated that between 40,000 and 50,000 passed along a single street in one hour; they were flying so low that pedestrians were inconvenienced by them. At Bisheim, on June 8th., the same phenomenon was observed and their numbers were so enormous that they darkened the sky. On June 11th. the flight that passed through Steyer in Austria, was so great that between one and two o'clock p.m. 90 to 100 per minute were counted in the breadth of 100 paces, the swarm being estimated at 1,000,000. Similar vast swarms were encountered in other places. 

Again, in 1903, a sudden and great invasion of these butterflies occurred in the autumn. They arrived in hundreds of thousands along the southern and eastern coast and dispersed over the whole of the British Islands. The flight was so vast that it extended from the Shetlands to the extreme south of England and Ireland. Their numbers were so prodigious that they swarmed along the whole of the eastern seaboard, from Durham to Kent, and wherever observations were made on the Scottish coast, they were abundant. The first arrivals of this vast invasion reached our shores on September 18th., and the flight continued for five or six days, their numbers increasing daily."

These butterflies look particularly attractive when you view them from below, with the sun shining through their wings that then resemble stained glass windows.

This individual was in Weardale yesterday, feeding on knapweed.

Painted lady

This was the first painted lady butterfly that I've seen here in the North East this year. I saw one last year but didn't manage to get a photo - this one was more obliging.

It was nectaring mainly on knapweed and thistles, on the hill to the north of Blanchland in Northumberland.

It's a long time now since we've had a full-scale painted lady invasion here. I think the last one was in 2009, when they arrived in late spring and produced a second generation, so that by early September there were hundreds of them - so many that it was reported in the national press.