Warm weather in the UK last summer saw the extremely rare Large Blue and Black Hairstreak butterflies in their highest numbers since records began.
The population of the threatened Large Blue rose by half, while that of the endangered Black Hairstreak was up by more than 900 per cent.
It is also thought that the cold snap in February and March may have helped the survival of caterpillars and chrysalises.
Despite the rise, last year was still about average and the Butterfly Conservation reported that there has been an decline in the overall butterfly population since records began more than 40 years ago.
The Butterfly Conservation’s Professor Tom Brereton said: “2018 brought some welcome relief for butterflies following five below average years in a row.
“But, 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.
“It remains to be seen what the knock-on effects of the 2018 heatwave will be. We know that extreme events such as this, which are set to increase under climate change, are generally damaging to butterflies.”
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