Painted lady show creates a dazzling butterfly effect

ANOTHER LIFE:IT WAS, as her e-mail said, "snowing butterflies – hundreds of butterflies swaying and darting in between the trees and shrubs, flying merrily on – to where?"

Eithne Heneghan, writing from Mayo’s Turlough country, was, like so many watchers in the west last weekend, mesmerised by the phenomenal flow of painted lady butterflies. Fluttering on an easterly breeze, they reached my garden at the coast and accumulated in dozens, sunbathing at the tops of trees, probing for nectar at buttercups and bramble blossom and joining the bumblebees at garden flowers. By evening, a mating pair were twirling up through the branches of an ash, gilded in the late bank holiday sun.

Next morning, most of them had moved on, but friends on Inishbofin, out on the horizon, reported the butterflies arriving “in clouds”, some even invading the house. Beyond ’Bofin, only the sunny Atlantic awaited.

The painted lady, Vanessa cardui, is in the same family of butterflies as the red admiral and a regular migrant from North Africa, at least a few reaching Ireland every summer – in occasional years a great many. But this year’s eruption to Britain and Ireland is extraordinary by any standard and, as the butterflies reproduce, a second and even third generation should add a flickering gaiety to countryside, parks and gardens.

The cause lies in a climatic quirk that brought an abnormally rainy winter to the Atlas mountains in Morocco – the wettest in 30 years – and a strong growth of the food plants of the painted lady’s caterpillars (cardui in its Latin name, means “of the thistles”). A Spanish student of the species, Constanti Stefanescu, found an estimated 150,000 pupae in a meadow of only 1.8 hectares south of the Atlas mountains, near Agadir.

Within weeks, migrating waves of the butterflies were crossing the Mediterranean into Spain, to lay eggs on thistles and mallows. A special feature of the species is its continuous breeding, without hibernation, and a rapid life-cycle, often complete from egg to butterfly in less than a month. From February onwards, pulses of painted ladies were spreading northwards across Europe.

By late May, they were entering Britain in their millions, notably on a tail wind to East Anglia, where observers counting the clouds of migrants gave up at 50,000. Most of the butterflies were in the bright, fresh colours of the southern European generation. The easterly breezes before the Bank Holiday brought them on to Ireland.

Here again, our plentiful thistles will feed the next generation. After mating, the slightly larger female lays eggs singly on the upper side of leaves – a tiny green barrel the size of a pin-head, surprisingly small for an insect with a 7cm wingspan. The egg hatches in a few days into a caterpillar with a spiky skin that is velvety black, with yellow dashes along its segments. It walks to the underside of the leaf, where it spins itself a little silky tent.

Inside, it gnaws at the leaf without breaking the upper tissue and, as it grows, makes new and larger tents of leaves held together with silk.

Inside the last, it forms the chrysalis from which its brilliant wings will unfold.

GIVEN THIS CAREFUL concealment, one might wonder at the self-advertisement of the adult butterflies themselves. Watching them perched, spread-winged, on the upper leaves of trees, I wondered if the swallows, skimming above them, might not be tempted to a takeaway: painted ladies do not, after all, have the big eye-spots on the wings of the peacock butterfly, serving as frighteners when suddenly displayed.

But swooping on butterflies seems to be an acquired taste for birds: they may need to peck at a dead one first (though peacocks – the feathered kind – and pheasants are, as David Measures reports, great gobblers of butterflies, wings and all).

What happens to painted ladies at the end of summer is still rather mysterious. They don’t, so far is known, have a reverse migration of the summer’s broods, though I did meet one once, at the end of a mild November, loitering along the shore at Slyne Head in Connemara.

Second-generation red admirals, on the other hand, can make exits in quite spectacular numbers from headlands on the south coast, heading for southern Europe, though climate change is now persuading some to overwinter in Ireland. In the latest Irish Naturalists’ Journal, Frank Smyth and David Nash describe watching over red admiral eggs and pupae in winter tents on nettles in sheltered spots on Co Dublin’s Howth Peninsula. Adults from the November eggs emerged in April and May.

Given the great start to summer, we could expect abundant migrant red admirals and clouded yellows, not to mention the more exotic migrant moths. Keep an eye out for the unmistakable hummingbird hawkmoth, hovering as it probes flowers for nectar with its extra-long tongue: a first encounter is one of life’s amazements.

Watching swallows swooping over the Slaney, I noticed other birds, of the same size, among them. They had a light- brown back, darker head, were white underneath and landed on the water and disappeared for several seconds.

Anne Kelly, Enniscorthy, Co Wexford

They were dippers that feed on insects and other aquatic life. They swim on or in the water, or walk on the bottom of streams.

We observed a heron feeding in the shallow tide on Clogherhead beach. He caught a sand dab, carried it towards the sand where he repeatedly dropped it, then carried it back and washed the sand off it before flying away.

Eoin O’Flynn, Termonfeckin, Co Louth

Sunflowers are noted for following the movement of the sun. I have noted that lupin flowers do the same.

Martin Crotty, Blackrock, Co Louth.

It is called phototropism or heliotropism and is caused by growth hormones, auxins, in the stem. They are photophobic and move constantly to the darker side of the stem causing it to bend towards the light.

Corncrakes are present again in Sligo harbour on both Oyster Island and Coney Island, and can be heard at Rosses Point.

Shaun Connor, Rosses Point, Co Sligo.

Michael Viney welcomes observations at Thallabawn, Carrowniskey PO, Westport, Co Mayo. E-mail: viney@anu.ie. Include a postal address.