Rare butterfly survives in county

Coppicing led to the Black Hairstreak's decline (pic: Doug Goddard)

A rare butterfly is now only found in an area around Northamptonshire, conservationists have confirmed.

The Black Hairstreak lives in 45 colonies across a belt of Royal forests from Oxford to Peterborough, a survey by the Wildlife Trust has shown.

The butterfly has become a species of conservation concern, as coppicing has cut the mature blackthorn it feeds on.

The study, carried out by volunteers, tracked the butterfly to Fermyn Woods and Salcey and Rockingham forests.

The "Help the Hairstreak" survey, funded by the River Nene Regional Park and Natural England, was launched in April to monitor the rare insects.

Distinguishing marks

Volunteers have been asked to report sightings of the butterflies to the Wildlife Trust in Northamptonshire.

Tom Day, conservation officer for the Wildlife Trust, told the BBC News website that, aside from nature reserves and national forests, private landowners should watch out for colonies.

Mr Day said: "A lot exist on privately-owned land. We hope landowners can help safeguard the population.

"Around the rest of the country most of the woodlands were managed and coppiced where the trees were cut down regularly on a much shorter rotation of about 10 years - traditionally for firewood - whereas here they were left to grow a lot longer.

"These include areas like Salcey forest, Rockingham Forest - all of those areas that have woodland with very mature blackthorn in them."

The Black Hairstreak can be distinguished through a row of black spots in the outer orange area of its wing and a pattern of white dots in the shape of W.