Monday 14 October 2019

Painted Lady a summer visitor that travels all the way from Africa

The Painted Lady is one of our largest and most beautiful butterflies
The Painted Lady is one of our largest and most beautiful butterflies

Jim Hurley - Nature Trail

The Painted Lady is a large and beautiful butterfly and it's on the wing to be enjoyed at present. It is not a local; it's a migrant. It is a summer visitor to our shores, and it comes all the way from north Africa.

Neither the adults nor their eggs, caterpillars or pupae are capable of surviving an Irish winter. It used to be believed that these warmth-loving annual summer visitors to Ireland died with the first frosts of autumn. It is now known that they don't die but head back to north Africa when the first autumn chills kick in. Vertical radar spotted swarms of them migrating south at an altitude of some 500m well beyond the limit of detection by our unaided eyes.

Albeit that it is a fast and powerful flier, it is amazing that a butterfly could fly from Africa to Ireland and turn around and go back again. It is now known that no individual Painted Lady is capable of achieving that remarkable feat; the journey is accomplished over some six generations.

Painted Ladies in places like Morocco in north Africa set off north on migration and, favourable winds permitting, cross the Mediterranean into Spain. They breed there and the individuals of the next generation take up where their parents left off and journey north to France. They blindly head north driven by some inbuilt genetic programming that is still poorly understood.

The adults of French generation breed and their offspring resume the journey of their parents and grandparents relentlessly following the urge to fly north. They cross the sea and arrive in Ireland to grace our green countryside. The journey is hazardous, so numbers vary from year to year. In a good year, the main influx usually occurs in May and June.

The adults feed by sucking nectar from a wide range of garden and wild flowers. If we have a fine summer the insects breed successfully. The caterpillars feed on Common Nettle, Burdock, mallows and thistles and give rise to an Irish generation of adults in late summer. These individuals start the long trek back to Africa.

Somehow, probably temperature-induced, the inbuilt genetic programming that compelled the butterflies to fly north flips and the Painted Ladies are driven to head south. Successive generations keep going south until they arrive back in Morocco. Once back in Africa, their programming flips again and the cycle of migration is perpetuated.

Wexford People

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