Lifestyle choice of the world's most cosmopolitan butterfly

The last red admirals and commas are feeding on ivy flowers in autumn sunshine and Britain’s butterfly year is drawing to a close once more.

One butterfly, though, is on the move. I’ve seen several painted ladies this month, but most have already headed south for the winter. The fate of British-born generations of painted ladies was a mystery until recently, when radar finally documented how they ascend to great heights before beginning their reverse migration.

The painted lady is constantly on the move – and how far it moves has only just been discovered by scientists.

Its route between Europe and Morocco is well understood, but biologists Gerard Talavera and Roger Vila have now revealed the painted lady can cross the Sahara desert and breed in the tropical African savannah.

Like the famous North American monarch, the painted lady undertakes its journeys in relays, one butterfly pausing and quickly reproducing – moving from egg to butterfly in eight weeks – before its offspring continues the migration. But Talavera and Vila, of Barcelona’s Institute of Evolutionary Biology and Harvard University, have calculated that an individual painted lady can travel 4,000km – further than a monarch.

The (lucky) lepidopterists spent autumn travelling across Senegal, Benin, Chad and Ethiopia in search of painted ladies, observing more than 20,000 emerging from chrysalises on the shores of the Niger river in Benin.

Such extreme migration looks like a difficult lifestyle choice for a butterfly, but the painted lady neatly solves the problem of too-cold European winters and too-dry African summers. To do so, it needs strength, but also supreme adaptability: its caterpillar’s ability to feed on a wide variety of foodplants has made it the world’s most cosmopolitan butterfly.