LAST summer's cold, chilly weather wasn't just depressing for people - it's also depressed the numbers of some of Britain's most threatened butterflies, a Dorset charity has discovered.

Grayling and Grizzled Skippers recorded their lowest numbers since records began, said Butterfly Conservation, which is based in East Lulworth.

After 2016 - the fourth worst year on record for our native butterflies - the charity said it hoped the insects would bounce back.

However, Grizzled Skippers and Grayling had their worst year on record for the second year running. Grizzled Skipper numbers were down nine per cent compared to 2016 and the population has now more than halved since the 1970s. Grayling declined by 6 per cent compared to 2016; its numbers have shrunk by 63 per cent over the last decade.

The threatened Dingy Skipper saw numbers fall by 22 per cent compared to 2016 and the rare Marsh Fritillary experienced a decline of 12 per cent over the same period.

Professor Tom Brereton, Associate Director of Monitoring at Butterfly Conservation, said: “There is little comfort in these results for the UK’s hard-pressed butterflies. Last year was the seventh worst in the 42-year series."

There was gloomy news, too, for the more common species. Despite Red Admiral numbers being up 78 per cent compared to 2016 and Comma numbers rising by 91 per cent, the Large White - one of the UK’s most well-known and widespread butterflies - saw its numbers tumble by 19 per cent.

Butterflies need warm, dry weather during their flight periods in order to feed and mate, said Prof. Brereton. "But a cold snap at the end of April saw other spring species such as the Grizzled Skipper and Duke of Burgundy struggle."

The figures were collected as part of the annual UK Butterfly Monitoring Scheme - UKBMS - led by Butterfly Conservation in partnership with other wildlife organisations. The scheme has run since 1976 and involves thousands of volunteers collecting data at a record 2,693 sites across the UK.