Record-breaking spring sees rare butterfly numbers rise

Butterfly experts said the conditions were perfect for the insects, which emerged weeks earlier than usual.

Dr Tom Brereton, head of monitoring at Butterfly Conservation, said: “The great spring weather provided respite for our beleaguered butterflies but wide-ranging conservation efforts are needed to reverse long-term declines.”

The Duke of Burgundy butterfly, which has suffered recent declines, saw its population rise by 65 per cent between 2010 and 2011 thanks to the hot, dry weather. Other rare butterflies to flourish were the Grizzled Skipper, which saw a 96 per cent rise, and the Pearl-bordered Fritillary, whose population rose by 103 per cent.

The data, collected by the UK Butterfly Monitoring Scheme, recorded major population falls for common species including the Peacock and Small Tortoiseshell as the warm spring turned into a colder-than-usual summer, however.

The scheme, which has run since 1976 in conjunction with Butterfly Conservation and the Centre for Ecology and Hydrology (CEH), sees volunteers collect data during the summer from more than 1,000 sites across the UK.

Dr Marc Botham, from the CEH, said: “Annual trends show us how strongly the day-to-day weather can affect butterfly populations in the short term but the UKBMS dataset collected over 36 years reiterates the importance of long-term data in assessing the state of UK butterfly populations beyond these annual fluctuations.

Other butterflies to record rises in population were migrant butterflies the Red Admiral, with a 123 per cent increase, and the Clouded Yellow, with a 41 per cent increase. Grass-feeding butterflies the Lulworth Skipper, only found on the Dorset coast, saw a 84 per cent increase after years of decline and the Northern Brown Angus, mostly found in Scotland, recorded a 21 per cent rise.