Southern Water is hoping to help save a butterfly which was once common in the woodlands and meadows of Sussex but is now teetering on the edge of extinction.

The varied habitat on which the pearl-bordered fritillary (Boloria euphrosyne) depends for survival has dwindled so much the butterfly has become an endangered species.

Changes in climate and land management patterns have created such a shift in the environment required for the butterfly to thrive it is now allocated the highest possible conservation priority in the UK's biodiversity action plan.

Despite their scarcity, fritillaries have been spotted in an area about three miles from Southern Water's reservoirs at Darwell and Powdermill, both near Battle.

The company's environmental scientists are now hopeful they can woo the species back to the county and encourage colonies to develop by recreating the perfect habitat.

The pearl-bordered fritillary - which has silvery-white pearl markings on orange, cream and black wings - lives in woodland clearings where trees have recently been cut or coppiced and there are areas of grass, bracken and open scrub.

It depends on a mosaic of open areas for movement between colonies and for food.

Caterpillars and adult butterflies feed on common dog violet, heath dog violet and marsh violet.

Changes in woodland management in recent years have led to the decline of the species.

Practices such as coppicing and thinning are in decline and many areas have been planted with conifers.

Clearings have become increasingly shady and overgrown while bracken habitats are no longer managed through grazing. Southern Water aims to tackle this by coppicing the woodland hazel and sweet chestnut trees around its reservoirs and maintaining open tracks through the woodlands.

It is working with the forestry service, which maintains the site, to apply for grants and create an "alluring habitat".

Butterflies have long been regarded above all insects as creatures of beauty in Western culture. Yet in the past 20 years, according to a study in the US journal Science, about 70 per cent of all butterfly species in Britain have shown signs of decline.

Nick Ellis, an environmental scientist at Southern Water, said: "This beautiful and rare butterfly is becoming scarce in the UK. It is a priority species on the UK biodiversity action plan but we hope we can boost its presence in our region by working to secure grants and create a new, safe environment on our sites for them to breed."