The recent sunny weather has brought the welcome return of butterflies to our countryside and gardens. One particular species you may have noticed very recently is a large orangy-pink butterfly with black wingtips, flying powerfully across the landscape, gliding and swooping down to take nectar from flowers.
This is the Painted Lady.
The remarkable thing about these insects is that many of them have travelled to the UK from North Africa, 2000 miles to the south, from where they started their journey. It is little wonder that many of them look a bit battered and faded given the epic nature of their voyage. Research has shown that some of them make the trip in one effort, flying at a height of about 500m and an average speed of 30 mph, navigating using the sun. Others arriving will be first or second generations, having been born in continental Europe. It is the longest insect migration on earth.
There are many hazards along the way that can affect the number of Painted Ladies arriving in the UK. Violent rainstorms can have a devastating effect and strong northerly winds and lack of sunshine, (which the insects need to fly), can slow the migration. In some summers there can be very few butterflies or even none. In other years the numbers arriving can be spectacular. Such was 2019 when swarms of butterflies hit landfall on the east coast of the UK, hundreds of thousands of them blanketing the countryside, with a particularly impressive display on the Farne Islands just off the Northumberland Coast.
Why do these insects make such a perilous endeavour? The answer is the same reason that makes any creature migrate; it is the search for food. The Painted Lady caterpillar has a preference for thistles and the adult insects pursue this food plant as the heat of summer travels northwards across Africa and Europe.
The urge to migrate northwards is driven by the lengthening daylight while the insect is in its larval stage - the caterpillar. When the butterflies arrive in the UK they breed and produce a new home grown generation, which take to the wing later in the summer. The caterpillars that give rise to these insects have lived their short lives while the days were shortening, post Summer Solstice. This declining daylight has the effect of programming the adult butterflies to fly southwards, and so they do, crossing the channel to make the return journey to their original African feeding grounds. This incredible discovery was made using a combination of professional academic research and citizen scientists who monitored numbers of Painted Ladies in both the UK and continental Europe.
So look out for Painted Ladies in the coming weeks and imagine the journeys they have made, and who knows, this could be another ‘Painted Lady Year’.