Declared extinct in the UK in 1979, this year the Large blue butterfly has flown in its greatest numbers since records began at the largest number of sites.


As a result of meticulous conservation efforts, starting with their reintroduction in 1983, southwest England now supports the greatest concentration of Large blues known in the world.

The Large blue is listed as one of Europe's most endangered species of insect, so the increase in their numbers in Britain is of international significance.

Large blue butterfly at National Trust site in the Cotswolds

Twelve new sites are being restored to flower-rich meadows suitable for Large blue breeding. Some of these sites have been started from scratch on arable land, failed conifer plantations and railway constructions or by restoring grazing to degraded downland. These sites already support a third of the UK population of Large blue butterflies.

Female Large blu ebutterfly laying an egg at a site in Somerset
© Jeremy Thomas

The twelve sites link or extend more established populations spanning two landscapes in mid-Somerset, and more recently, in the Cotswold Hills. Six partner organisations are managing the new sites - The National Trust, Somerset and Gloucestershire Wildlife Trusts, J&F Clark Trust, Natural England and Oxford University.

The restorations are being led, supervised and monitored by David Simcox and Sarah Meredith from the Royal Entomological Society, who have designed bespoke management plans for each site. Between 2019 and 2022, funding by the Prince of Wales Charitable Fund made it possible to physically reintroduce Large blues to two sites in the Cotswolds after an 150 year absence.

Sarah Meredith releases the first Large blue caterpillars to new site
Sarah Meredith releases the first Large blue caterpillars for 150 years onto the National Trust's Rodborough Common © David Simcox

David Simcox said of the project "We are extremely proud that the partnership's efforts have enabled hundreds of people to see this stunning and enigmatic butterfly flying on some of the most beautiful grassland sites in the country. The greatest challenge ahead is to secure this expansion in a warming climate and to develop strategies to mitigate the impacts of extreme weather events."

The restoration of this disappearing type of wild meadowland has also provided the ideal breeding ground for numerous other rare species of plant and insect that share the Large blue's habitat. Other insects and plants that have increased or newly colonised the restoration sites include the Shrill carder bee (the UK's second most endangered bumblebee) the Rock-rose pot beetle and green-winged orchids as well as eight red data-listed butterflies.

Shrill carder bee
Shrill carder bee © Jeremy Thomas

Head to the Royal Entomological Society website for more information, and see which butterflies you can spot in your own garden here.


Molly Blair
Molly Blaireditorial and digital assistant

Molly is the Gardens Illustrated's editorial and digital assistant. She has a roof garden and has her RHS level 2.