Rare UK butterflies enjoy best year since monitoring began

Hot summer of 2018 boosted large blue, and black hairstreak, but small tortoiseshell declined

Patrick Barkham

Mon 8 Apr 2019 06.30 BSTLast modified on Mon 8 Apr 2019 11.48 BST

The golden summer of 2018 saw two of the UK’s rarest butterflies, the large blue and the black hairstreak, enjoy their best years since scientific monitoring began.

More than two-thirds of British butterfly species were seen in higher numbers last year than in 2017, but despite the ideal butterfly weather, it was still only an average season – the 18th best in 43 years of recording.

Species whose caterpillars feed on grasses struggled as grass withered in hot weather, while there were mysterious ongoing declines for the small tortoiseshell and the peacock, both garden favourites. Despite the warmth, both butterflies had their third-worst year since the UK Butterfly Monitoring Scheme – the longest-running scientific insect monitoring project in the world – began in 1976.

Prof Tom Brereton of Butterfly Conservation said: “There were not as many butterflies around as we might have expected given the fabulous weather over much of the butterfly season, and overall, 2018 ranked as barely better than average.

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