Mystery of the vanishing butterf ly

sMALL tortoiseshell butterfly numbers have plummeted this year despite the summer heatwave.

sightings were down 32 per cent compared to last year, the Big Butterfly Count

has revealed, with only 23,000 spotted by volunteers over three weeks.

This was the worst summer for the species in the history of the annual survey.

A long, warm summer should be good for butterflies and caterpillars so this is a blow for the small tortoiseshell, pictured, which has suffered a 75 per cent decline since the 1970s.

However, some butterflies did enjoy a bumper season, with large increases of small, large and green-veined whites compared to last year.

The highest ever numbers of holly blue were spotted, up 122 per cent on last year, while the common blue increased by 51 per cent on 2017, enjoying its best year since 2010.

However, populations of red admiral, comma and gatekeeper were all down on last year.

For some species, the warm weather well before the count in high summer could mean they flourished before volunteers were out, experts said. However, the long-term trend for many common species – from butterflies and birds to hedgehogs and bees is one of decline, said Richard Fox, from wildlife charity Butterfly Conservation, which organises the count.

He said: ‘In a summer when the weather is typically British, and rainy, and the small tortoiseshell performs badly, you could say that’s perhaps not surprising.

‘But in a year when the summer weather is fantastic and most species seem to do well, the small tortoiseshell not doing well is even more dramatic and concerning.’

He said more research was needed to uncover the reasons for the decline in numbers.

Mr Fox said the findings also highlighted the survey’s importance since the results show how common species are faring.

This year, a record 100,000 people took part in the count, spotting almost a million butterflies in the countryside, parks and gardens.

The most commonly spotted butterfly was the small white, followed by the large white and the gatekeeper in third place.