Large Blue back in Britain

Conservationists are celebrating the recovery of a highly endangered species of British butterfly.

Despite more than 50 years of effort to halt its decline, the Large Blue butterfly was pronounced extinct in Britain in 1979.

A team of dedicated lepidopterists have worked tirelessly since to bring the butterfly back to our countryside. This week marks the 25th anniversary of the large blue butterfly reintroduction.

Sir David Attenborough will be among the speakers at a celebration event, in Somerset, now the location of the largest concentration of large blues in the world. Also this week a major peer reviewed scientific paper on the reintroduction project will be published.

Professor Lord May of Oxford, recent President of The Royal Society and former Chief Scientific Adviser to the UK Government, said: "The recovery of the large blue butterfly is the world's largest-scale, longest-running successful conservation project involving an insect.

"It illustrates perfectly how the application of sound science can be used to solve some of the apparently intractable problems that face conservationists worldwide today."

The Large Blue is one of the worlds most threatened species. The British reintroduction was based on major scientific breakthroughs, and the development of a pioneering model for conservation which is now being used to restore rare butterfly species across Europe.

Professor Jeremy Thomas, a Fellow at the Centre for Ecology & Hydrology (CEH) led the reintroduction programme with colleague David Simcox. Professor Thomas said: "The success of this project is testimony to what large scale collaboration between scientists, conservationists and volunteers can achieve.

"Its greatest legacy is that it demonstrates that we can reverse the decline of globally-threatened insect species once we understand the driving factors."

The Large Blue has an unusual life-cycle, which made its conservation difficult. When the caterpillar is three weeks old it tricks red ants into believing it is one of their own grubs and is taken underground to be placed with the ant brood. The caterpillar spends the next ten months feeding on the grubs before pupating in the nest the following year and then emerging to crawl above ground as a butterfly.

The reintroduction in 1984 was based on the discovery that large blue caterpillars can only survive in the nest of one particular species of red ant, Myrmica sabuleti.

Changes in countryside management were found to be responsible for the extinction. Alterations in grazing coupled with myxomatosis in rabbits left grassland too tall and shady for the heat-loving Myrmica sabuleti.

Today suitable habitat has been restored to more than 50 former sites, and the butterfly can be found on 33 of them in the south-west of England. Other rare species of plants, insects and birds now benefit from the same conservation work as the large blues because they had suffered from the same changes in agricultural practices.

This is a tribute to a major conservation programme underpinned by innovative science and implemented by a determined and broad partnership of scientists and conservation bodies including CEH, Natural England, Somerset Wildlife Trust, National Trust, University of Oxford, Butterfly Conservation, J&F Clark Trust and Gloucestershire Wildlife Trust.

Network Rail has also contributed to the reintroduction by working with CEH and Natural England to develop some of the largest colonies in northern Europe. As part of Network Rail's engineering works on two sites, CEH designed plans that created optimum habitats for large blues, at a net financial saving for Network Rail.

The success of this project has led to a major, European-funded research programme, MacMan. It uses the approach pioneered by the large blue project to understand and then conserve four other globally threatened species of large blue, which exist outside of Britain, across Europe.

Dr Nigel Bourn, Director of Conservation, Butterfly Conservation said: "Over 70 per cent of Butterfly species in the UK are in decline.

"This fantastic project shows what can be done for even the most challenging and endangered species when you have a great partnership, world-leading science and long-term funding to ensure continuity of action. It demonstrates that it is possible to save threatened butterflies when we have sufficient resources in place".