The reintroduction of a rare butterfly that had been extinct in Britain has been hailed a success after the insects bred in the first year.
The large blue butterfly was introduced to Rodborough Common in Gloucestershire last year, after five years of special landscape preparation to create the right conditions for the species.
Large blue butterflies have a remarkable life cycle, which involves the larvae tricking a particular species of red ant into carrying them into their nest where they feed on ant grubs before emerging the next year as butterflies.
The species was declared extinct in Britain in 1979, but was first reintroduced from populations on the continent nearly 40 years ago and has been established at a number of sites across southern England.
Experts have recreated conditions for the Myrmica sabuleti ant species by encouraging growth of wild thyme and marjoram, which the butterfly feeds and lays its eggs on.
The scheme at Minchinhampton and Rodborough Commons is the largest ever reintroduction of large blues in the UK. Some 1,100 were larvae taken from other West Country locations and released last August on the 867-acre site owned by the National Trust.
An estimated 750 butterflies have successfully emerged at the site over the summer, and the team members monitoring the scheme have recorded large blues mating and eggs laid on thyme and marjoram.
It is the first time for 150 years the large blue butterfly, largest and rarest of all nine British blue butterflies, has been recorded at Minchinhampton and Rodborough Commons.
It follows work to prepare the site by partners including the National Trust, Butterfly Conservation, Limestone’s Living Legacies Back from the Brink project, Natural England, Royal Entomological Society (RES) and the Minchinhampton and Rodborough Committees of Commoners.
David Simcox, research ecologist and co-author of the commons management plan, said: “The butterfly needs high densities of the heat-loving red ant Myrmica sabuleti, which has a crucial role to play in the lifecycle of the butterfly."
In summer, the butterfly larvae deceive the ants into thinking they are their own young and carrying them into the nest to complete their life cycle by feeding on the ant grubs until they are ready to pupate and emerge.
Amid the success of the reintroduction, the National Trust is warning that the coronavirus pandemic has had a major impact on the charity’s finances just as it is focusing on nature and climate emergencies.
Ben McCarthy, head of nature conservation and restoration ecology, said: “Now, more than ever, we need support so that we can continue with our vital nature conservation work to improve the state of nature in the UK and achieve carbon ‘net zero’.”