Threatened wood whites could be seen by 10 April last year, but this year were delayed until early May.
And the Duke of Burgundy butterfly made an appearance in late April this spring, around three weeks later than last year.
Last spring saw butterflies emerging earlier than normal following an unusually mild February and March. But the extreme wet weather that followed resulted in a terrible year for most species.
Butterfly Conservation’s findings, which focus on the UK’s rare and threatened species, show a large contrast with last years’ spring sightings.
Butterflies emerging late from their chrysalises is not necessarily a problem for the insects, but the weather over the next few weeks may be crucial to their success.
Wet weather prevents butterflies from flying, which they need to do to find mates and plants on which to lay their eggs, explained Butterfly Conservation surveys manager Richard Fox.
“If those [weather] conditions carry on for the duration of your life as a butterfly – which might only be a week at best – then you leave no offspring.”
And this year, butterflies appear to be in “very low numbers” following last year’s poor weather.
source : http://www.bbc.co.uk/nature/22546675