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.