Butterflies and moths have been baffled by this year’s extreme weather, with many species appearing at unusual times, Butterfly Conservation said today.
But while the hot, dry spring and one of the warmest autumns on record saw butterflies on the wing from early March all the way through to December, the cold damp summer saw many species struggle.
The charity’s Big Butterfly Count this year revealed numbers of common species were down 11% in the face of a miserable summer.
The poor results followed the unusually hot spring, in which species such as the pearl bordered fritillary and the grizzled skipper emerged weeks ahead of normal.
The black hairstreak, which normally appears in June, was seen in May and the Lulworth skipper, a Dorset species, was on the wing seven weeks early.
The warm weather returned in autumn, prompting the arrival of a number of migrant moths from as far as southern Europe.
Humming-bird hawk-moths had their best year on record in the UK, with Butterfly Conservation receiving 9,000 reports of sightings, outstripping the previous record of 6,500.
The UK also saw the highest number of rare flame brocade moths in 130 years, with a colony discovered in Sussex, while exotic species such as the crimson speckled moth and vestal moth were also seen this autumn.
A rare marsh fritillary was spotted in mid-September, almost eight weeks after it should have disappeared for the year, and red admiral butterflies are still being spotted.
And the unseasonably warm winter has caused spring usher moths, Hebrew characters and common Quakers to appear months early.
Butterfly Conservation surveys manager Richard Fox said: “The weather is a matter of life and death for butterflies and moths, and 2011 has been a year of extremes.
“It’s too soon to tell exactly how the UK’s butterflies and moths have fared but the signs are that spring species, including many threatened butterflies, benefited from the hot weather in April and May.
“In contrast most summer-flying species struggled to survive in the cold and damp.
“Autumn brought a reprieve for our beleaguered butterflies and moths, with many native species able to extend their flight periods or squeeze in an extra brood, as well as the arrival of marvellous migrant moths from overseas.”