Blue dawn for UK's rarest butterfly

A flower-strewn hillside overlooking the valley made famous by writer Laurie Lee is set to become a flagship site for the UK's rarest butterfly - the previously extinct Large Blue.

Rough Bank sits in the Slad Valley in the Cotswolds, a landscape evocatively brought alive in Lee's autobiographical novel Cider with Rosie.

The site has been acquired by Butterfly Conservation who plan to re-introduce the Large Blue to the reserve - a location which is already home to four species of blue butterflies.

The Large Blue became extinct in the UK in 1979 and is threatened across the world, but painstaking conservation work has led to its re-introduction at a tiny number of sites in Southern England.

The Rough Bank reserve could become a key site for the species as it expands back into the Cotswolds from its re-introduction base in Somerset's Polden Hills.

The butterfly has a fascinating lifecycle which is closely linked to a species of red ant. Large Blue caterpillars resemble ant grubs and use this likeness to trick the ants into carrying them into the heart of their nests.

Once inside they feast upon ant grubs and will live in the nest for up to two years.

The caterpillar transforms into a chrysalis which produces a song mimicking the queen ant which ensures further protection.

The discovery of this symbiotic relationship between ant and butterfly was crucial to the successful re-introduction of the species.

Rough Bank is already home to the Adonis, Chalkhill, Small and Common Blue and it is hoped that the threatened Duke of Burgundy will also return.

The reserve is biologically rich - the main area of flower-rich grassland is a site of Special Scientific Interest (SSSI) boasting a wide range of orchids.

Laurie Lee's 1959 novel Cider with Rosie is set amidst the landscape of the Slad Valley and it is likely that he roamed Rough Bank as a youth.

Rough Bank was secured with help of a grant from Natural England but public support is still needed to secure further funds for acquisition and management costs.

Dr Martin Warren, chief executive of Butterfly Conservation, said: "This site gives us a unique opportunity to put something very special back into the Cotswold landscape and create a wonderful new reserve for the Large Blue and other butterflies.

"We urgently need the public to help us acquire this site and ensure it is managed in the best way possible."

The restoration programme will involve grazing the site with cattle, clearing some scrub to create open, sunny conditions and checking the right ants are present.

The butterfly will then be released as young caterpillars, sourced from existing colonies in Somerset, and placed carefully for adoption by the ants.