Butterfly's 900% boom as larvae 'turbo-charged'

A wildlife charity says numbers of a rare butterfly in a wood have "boomed", exploding by 922% after it was reintroduced.

Butterfly Conservation (BC) said it had recorded 746 Wood Whites at Fineshade Wood in Rockingham Forest, near Corby, Northamptonshire, compared to just 73 in 2025.

Twenty adult Wood Whites, a butterfly classified as endangered in Great Britain, had been taken to the Forestry England site in 2024 from Hazelborough Forest and Bucknell Wood, close to Silverstone.

The charity said the tally of recent sightings had been "absolutely extraordinary" and heat "may have turbo-charged larval growth".

BC said male Wood Whites performed "courtship displays in which they land opposite females, extend their tongue-like proboscis and wave their head and antennae back and forth over the female's wings".

The butterfly used to be much more common across southern England and eastern Wales, but since 1992 its distribution has dropped by 76%.

Dr Jamie Wildman, BC's central England conservation manager, said: "The number of butterflies being seen by our volunteers and members of the public is absolutely extraordinary.

"We're delighted to see the population boom so quickly since the start of the reintroduction.

"Only two years ago we were releasing butterflies here in the hope that one day the woodland would support a thriving population again.

"Seeing hundreds of Wood Whites flying through Fineshade today shows what's possible when habitat restoration, scientific research and hundreds of volunteer hours come together."

The reintroduction was made possible by funding from Natural England's Species Recovery Programme.

The charity said on 15 July one volunteer had counted no fewer than 42 Wood Whites, thought to be offspring of the first brood, which hatched in May.

BC believes the warm spring might have accelerated caterpillar development.

Dr Dan Hoare, its director of nature recovery, said: "If the ground is wet enough to start with and the foodplants are in the ditch edge, sheltered and supported by taller grasses, then the heat may have turbo-charged larval growth and helped them get through before the worst of it.

"As butterflies are so sensitive to temperature, tracking their fortunes can provide crucial insights on which species might be winners and losers from our rapidly changing climate, helping us plan effective climate adaptation."

If the success continued, the charity said Fineshade Wood would be a "beating heart" for the Wood White, sending butterflies out into the surrounding countryside and woodland.

Mark Underwood, forest centre manager at Fineshade Wood, said: "I know anecdotally Forestry England staff and our visitors have been spotting lots of these beautiful butterflies.

"We're proud to partner with Butterfly Conservation on such a successful reintroduction."

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