Blue heaven...return of butterfly we nearly lost
A BUTTERFLY that was once extinct in Britain has bounced back to enjoy its best season in 80 years, experts said yesterday.
The Large Blue is now found in higher concentrations in southwest England than anywhere else in the world.
It was declared extinct in the UK in 1979 but was reintroduced from Sweden in 1984.
Thanks to decades of conservation management and ideal weather this summer, numbers have boomed.
The UK population has reached 17,000 at 50 sites where the grass is closely cropped to create ideal conditions.
Two of the sites – the Gloucestershire Wildlife Trust and Royal Entomological Society’s Daneway Banks and Somerset Wildlife Trust’s Green Down – saw 10,000 adults fly and lay more than 250,000 eggs on the abundant thyme and marjoram flowers.
Numbers there grew 74 per cent and 64 per cent respectively compared to last year.
The boost is welcome because it is the only UK butterfly so threatened globally that it is in the International Union for Conservation of Nature’s Red Data Book. The recovery is a triumph for conservationists who discovered that the Large Blue is a sneaky creature that relies on one specific type of red ant – Myrmica sabuleti – to raise its young.
The butterfly’s caterpillars spend three weeks feeding on thyme and marjoram before emitting scents that trick ants into thinking they are its own grubs.
The ants drag the caterpillars into their underground nests to rear them in safety. They “reward” their hosts by eating their grubs for 10 months before pupating the following year and crawling above ground as a butterfly.
Professor Jeremy Thomas, of Oxford University, who pioneered the reintroduction, said: “The success of this project is testimony to what large scale collaboration between conservationists, scientists and volunteers can achieve.”