The painted lady butterfly

The flight time from Marrakesh to London is about three and a half hours. That’s a direct flight with a speed of about five hundred miles per hour. The journey for a butterfly born in the Atlas Mountains of Morocco flying north towards the UK is significantly less direct and much more impressive.

Painted lady butterflies are a familiar site in Britain but unlike most of our regular butterflies they don’t survive our winter in any form (ie egg, caterpillar, chrysalis or adult butterfly). Their regular presence in our countryside and gardens during summer is due to them being strong migrants flying over two seas and a distance significantly greater than fifteen hundred miles.

With suitable conditions in the Atlas Mountains in spring many hundreds of thousands of painted lady butterflies might be born and if the winds are favourable many of them will head north on a journey which takes them across the Mediterranean, through Portugal, Spain and France. Some might reach southern England in March, but more will arrive in April, May and June.

Some butterflies won’t make it to the UK, they might stop along the way to breed but because their progeny can be produced quite quickly the next generation continues the northward journey started by their parents arriving with us in summer.

One thing is certain. We always see painted lady butterflies in Britain during the summer and in a good year we can witness an invasion with huge numbers across the whole of the country. Recent major invasions have occurred in 2019 and 2009, prior to that it was 1996 but these occurrences have been happening regularly for a long period of time; records of similar invasions in 1879 and 1903 confirm this.

Given the effort it takes to get here I can only assume that painted lady butterflies must enjoy the British summer. When they arrive their first task will be to feed on nectar from flowers in our gardens, hedgerows and meadows. Next they must breed. Important in this process is to find the appropriate plants on which their caterpillars will feed.

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The spear thistle is the most commonly used food plant for painted lady butterflies.

Painted lady food plants

Painted ladies very much like thistles, particularly the spear thistle, aka common thistle, Cirsium vulgare. Their choice of food plant is reflected in the butterfly’s scientific name, Vanessa cardui, because thistles belong either to the carduus or cirsium family depending upon the shape of their seed heads.

As gardeners we can help by leaving a patch of our garden to go wild and welcome the growth of thistles in a sunny sheltered spot. Seeing painted lady butterflies laying eggs and watching as their caterpillars develop will be our reward.

The painted lady caterpillar forms a protective web around itself where it feeds.

Caterpillars and life cycle

Painted lady caterpillars form protective webs around themselves to prevent birds from eating them. Inside the web the black spiny caterpillar eats the leaf and as it gets bigger the small webs become larger tents sometimes embracing several leaves. Their webs become ever more conspicuous as they fill with the caterpillar’s own droppings before eventually the caterpillar pupates. The whole process from egg to adult butterfly is quite short, maybe between thirty and forty days.

Because of this quick turn around we usually see a fresh generation of vibrant new painted lady butterflies during the summer. It isn’t uncommon to see them feeding on flowers of buddleia in gardens alongside other large butterflies such as peacocks and small tortoiseshells. But the next few months will be very different for these species.

Peacock butterflies and small tortoiseshells will survive our winter in their adult form giving them an easy start next year, but painted ladies can’t do this. Instead this brave new generation of painted lady butterflies need to start a southerly migration.

The return journey

In a superficial way this journey might be likened to the migration of birds such as swallows and house martins but in one very significant way it is quite different. The butterflies undertaking this reverse migration are not the same butterflies that arrived in spring. They might be one or two generations down the line. It is astonishing that butterflies can make such long journeys and I am always equally amazed that the individual butterflies know which way to fly.

Some of the individuals born in Britain might make it all the way back to Morocco, others might stop along the way. Any that are left behind in the UK are likely to die without the chance to lay eggs of their own. Maybe one day painted lady butterflies might over-winter here and their lives might be a little easier but for now let’s revel in this tenacious miracle of migration.

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