Sun's a butterfly beauty treatment

With warm weather boosting woodland butterfly species, experts are reporting unusual colour variations which would have been the highlight of collections.

Matthew Oates, conservation adviser at the National Trust, managed to photograph a purple emperor with markings so rare, he said it would only be seen "once in a purple moon - which is rarer than a blue moon".

The purple emperor usually has white markings on its purple iridescent wings, but this particular butterfly was missing them. Mr Oates said: "In the heyday of old-fashioned butterfly collection, this was the dream of every collector, as there were so few of them."

He said colour variations tend to occur in high populations in good weather, and that this month's warmth has boosted numbers among woodland species such as the silver-washed fritillary and the white admiral. Mr Oates said it could even help push up numbers among common species such as the peacock and red admiral, of which relatively few have been seen this year.