The UK's butterflies suffered a "catastrophic" year in 2012, with most species declining in the face of one of the wettest years on record, a study has shown.
Of 56 butterfly species monitored, 52 saw numbers decline from the previous year, with 13 experiencing their worst year in records dating back to 1976 as the insects struggled to mate and find food and shelter in the washout summer.
Threatened species were already experiencing long-term declines before the deluges of 2012 and wildlife experts are now warning struggling butterflies could become extinct in some areas of the UK as a result of the wet weather.
The critically endangered high brown fritillary saw numbers fall by 46% on the previous year and the endangered heath fritillary saw numbers halve, the UK Butterfly Monitoring Scheme by Butterfly Conservation and the Centre for Ecology and Hydrology found.
The black hairstreak, one of the UK's rarest species, saw its numbers fall by 98%, while other hairstreak species also fared badly, with the green hairstreak down by more than two thirds (68%) and the white-letter hairstreak down 71%.
Common species also suffered, with the common blue numbers falling by 60%, brown argus down by almost three quarters (73%) and large skippers down by more than half (55%) in 2012 compared with 2011.
The two "cabbage white" species, large and small whites, both saw their numbers collapse by more than half, while garden favourite the small tortoiseshell saw its populations continue to decline with falls of 37% on 2011 figures.
Dr Tom Brereton, head of monitoring at Butterfly Conservation, said: "2012 was a catastrophic year for almost all of our butterflies, halting progress made through our conservation efforts in recent years. Butterflies have proved before that given favourable conditions and the availability of suitable habitat they can recover, but with numbers in almost three-quarters of UK species at a historically low ebb any tangible recovery will be more difficult than ever."
Only four species saw populations increase in 2012 compared with 2011, including the grass-feeding meadow brown whose numbers rose by a fifth (21%) and the Scotch argus which thrives in damp conditions and saw numbers increase by 55%.
The figures came from thousands of volunteers who braved the wet, miserable weather to collect data on butterflies every week throughout the summer at more than 1,000 sites across the UK.