Britain's list of native butterflies just grew by one — and for the first time in six decades, the large tortoiseshell can call these islands home again.
Butterfly Conservation has officially declared the large tortoiseshell (Nymphalis polychloros) a resident species in the UK after a flurry of early spring sightings confirmed that the insect is not just visiting, but breeding and overwintering in British woodlands.
Individuals have emerged from hibernation in Kent, Sussex, Hampshire, Dorset, Cornwall, and the Isle of Wight — a geographic spread that leaves no doubt: this beautiful, elusive butterfly is back.
'The signs are really positive, which is lovely,' said Richard Fox, head of science for Butterfly Conservation. 'It is resident and therefore it is another species to add to Britain's total, which is good news.'
The large tortoiseshell became extinct in Britain by the 1960s. Unlike its more common relative the small tortoiseshell — a garden visitor whose caterpillars eat nettles — the large tortoiseshell is a tree-dwelling species. Its caterpillars feed on elm, willow, aspen, and poplar, and the adults are far more secretive.
For decades, the loss of elms due to Dutch elm disease was blamed for the butterfly's disappearance. But lepidopterists now believe Britain may have always been at the northern edge of the species' natural range — and that rising temperatures driven by climate change have helped it expand northward again.
Population increases in the Netherlands and France, combined with warmer conditions in southern England, have created the conditions for recolonisation. Since 2020, large tortoiseshell caterpillars have been found feeding in the wild — first in Dorset, now more widely — proving the species is breeding.
The insect hibernates as an adult butterfly, emerging in spring to mate and lay eggs. Its offspring will take to the wing in midsummer, meaning this spring's sightings could herald a burgeoning population by summer's end.
Butterfly Conservation is urging the public to log any observations on iRecord, a free citizen science app, to help track the butterfly's expanding range.
Britain's native butterfly count now stands at 60 — and for the first time in the charity's 58-year history, the large tortoiseshell is among them. 🦋
*Sources: The Guardian · Butterfly Conservation · iRecord UK*
