Rare butterflies have 'stronghold' at Marsland, Devon
A nature reserve has become a stronghold for two rare butterflies, a wildlife trust has said.
In the 1980s a "handful" of small pearl-bordered fritillary and pearl-bordered fritillary butterflies were found at Marsland in Devon.
However, in the past 20 years numbers have increased, "bucking the national trend", said Devon Wildlife Trust.
Butterfly Conservation said across the UK both species had declined by more than 50% since the 1970s.
More than 200 individuals of each species have been recorded this summer, with a similar number counted in 2013 and more than 600 in 2012.
Stephen Hussey, from the trust, said land management had helped increase numbers but he was unsure what had caused the population explosion in 2012.
He said that "one of the UK's greatest concentrations of both species" were present at the site.
"Because of habitat loss both species have seen falling ranges and populations and are now absent from large areas of the UK," he added.
Richard Fox, from Butterfly Conservation, said the pearl-bordered fritillary was "one of our rarest butterflies" and since the 1970s the UK population had declined by 71%.
"The species is pretty much lost from the whole of the east of England and the Midlands and it continues to fall."
Mr Fox said the UK population of the small pearl-bordered fritillary had declined by 56% since the 1970s and was found only in Scotland, Wales and the west of England.