Large tortoiseshell butterfly confirmed no longer extinct in UK | Wildlife

The great tortoiseshell – an elusive and enigmatic butterfly that went extinct in Britain in the last century – is once again a UK resident species, with a spate of sightings in early spring.

Britain’s list of native butterflies has grown to 60 with the return of the insect after individuals emerged from hibernation in forests in Kent, Sussex, Hampshire, Dorset, Cornwall and the Isle of Wight.

These observations led Butterfly Conservation to declare the large tortoiseshell (Nymphalis polychloros) a resident species in the UK – as opposed to a migratory species – for the first time in the association’s 58-year history.

“The signs are really positive, which is very pleasing,” said Richard Fox, Butterfly Conservation’s chief scientist. “It’s resident so it’s another species to add to the UK total, which is good news. It’s not yet well established enough to say it’s definitely back and will be widespread in many landscapes – we’re still in that area of ​​uncertainty at the moment, but there are some encouraging signs.”

Unlike the small tortoiseshell (Aglais urticaria), found in gardens and whose caterpillars feed on nettles, the greater tortoiseshell is an arboreal butterfly whose caterpillars feed on trees such as elm, willow, aspen and poplar.

It is larger, as its name suggests, and lacks the white markings found on its more widespread counterpart.

The loss of elms due to Dutch elm disease was once thought to be a factor in the extinction of the great tortoiseshell in the UK in the 1960s, but lepidopterists now believe that Britain may always have been at the northern edge of its natural range and that the species’ return is now favored by global warming.

It last flourished in Britain during a series of fine summers in the 1940s, but in recent years increasing numbers of people have migrated across the North Sea and the English Channel due to increasing populations in the Netherlands and France.

Higher temperatures this century have also helped many continental butterfly species settle or re-establish themselves in Britain, including the spectacular Clifden nonpareil butterfly.

The greater tortoiseshell first reappeared in large numbers in the UK on the south coast in 2006-2007, but many subsequent sightings have been attributed to unauthorized releases by butterfly breeders keen to re-establish this charismatic species.

Since 2020, large tortoiseshell caterpillars have been found feeding on trees in the wild – first in Dorset and now more widely – confirming that the butterfly is breeding again in Britain.

The insect hibernates as an adult and emerges in the spring to mate and lay eggs. Its offspring take flight as adult butterflies in mid-summer, raising hopes that this spring’s sightings will create a booming population later in the year.

Butterfly Conservation, which added the species to its first sightings page, is urging people to record all their sightings on iRecord, a free citizen science app, which helps build a picture of the butterfly’s distribution and population expansion.