Climate change could be behind the decline of more than three-quarters of the UK's butterflies, a study has found.
Some 76% of the UK's resident and regular migrant butterflies have fallen in number over the last 40 years, according to a joint report by the charity Butterfly Conservation and the Centre for Ecology & Hydrology (CEH).
While numbers are in decline across Europe, the UK has been hit the worst, with Southern Britain most affected.
Reasons behind the drop are not fully understood, but the "varied" effects of climate change, deterioration of suitable habitats and increased use of herbicides and pesticides are thought to have played a part.
Butterfly Conservation vice-president Chris Packham said the plight of the UK's winged insects was one that "should shame us all".
The BBC Springwatch presenter said: "As a society we are guilty of standing idly by as once common species, never mind the rarities, suffer staggering declines.
"We are finally facing the meltdown that was coming all along.
"There is a very, very urgent need to understand the reasons for the decline, which are likely to be complex."
Widespread species such as the Wall, Essex Skipper and Small Heath now rank amongst the most severely declining butterflies in the UK. The Gatekeeper, one of Britain's most abundant butterflies, has experienced a 44% slump in the last decade.
Agricultural intensification, including the decline of flower-rich meadows, removal of hedgerows and increased nitrogen being released into the environment, is believed to have had an impact on numbers.
The report, The State of the UK's Butterflies 2015, warns that climate change has had "much more varied, subtle and worrying impacts on butterflies than had previously been realised".
Warmer temperatures are attracting more foreign butterflies to Britain's shores, with populations of common migrant species - the Clouded Yellow, Red Admiral and Painted Lady - showing a dramatic increase since the 1970s.
Mr Packham said: "Climate change has had a significant impact - some of the migrant species are increasing, because of milder winters and warmer, wetter springs. However, the bread and butter of British butterflies are not benefiting."
The differing effects of climate change are also believed to have contributed to a North-South split in rural areas, with butterflies in England declining while those in Scotland show no long-term trend.
Despite the stark situation overall, recording and monitoring of the UK's butterflies has "never been stronger", with data from the last decade revealing a more positive trend.
Intensive conservation efforts have had a "breakthrough" effect on the fortunes of some of the UK's most endangered butterflies, the report said.
The threatened Duke of Burgundy has increased by 67% while even the UK's most endangered butterfly, the High Brown Fritillary, has been relatively stable in the last decade.