Rare continental butterfly survives UK winter for first time.
Patrick Barkham, Thursday 19 March 2015.
A rare continental butterfly which until last summer had only once before been seen in Britain has survived the winter, raising hopes it will breed here for the first time. The scarce tortoiseshell (Nymphalis xanthomelas) was spotted in unprecedented numbers in Kent, Lincolnshire, Suffolk and Norfolk last summer, after flying through Holland on a long migration from eastern Europe. One of the butterflies was seen again over two days last week in Holt country park, Norfolk, a sign it successfully hibernated over winter.
According to Butterfly Conservation’s head of monitoring, Dr Tom Brereton, the woods near Holt provide suitable conditions for the butterfly, which feeds on sap from birch trees in the spring and lays eggs on willows.
If fine spring weather helps females and males to find each other to mate, the butterfly, also known as the yellow-legged tortoiseshell because of its distinctive straw-coloured legs, will breed in Britain for the first time.
“This new sighting is a truly historic event as it marks the first time this stunning butterfly has ever overwintered successfully in Britain,” said Brereton.
“We’ve been waiting apprehensively over the last couple of weeks for news to see if any scarce tortoiseshells would emerge from hibernation following last year’s mini invasion. The butterfly prefers very cold winters and we weren’t sure if any would survive our mild season.
“If more emerge as we head into spring, 2015 could see the first UK-born scarce tortoiseshells on record.”
Until last summer, the only record of a scarce tortoiseshell in Britain was a single female seen near Sevenoaks in 1953. Usually found between China and eastern Europe, an unprecedented migration of this large, mobile butterfly last summer saw at least 30 sightings in Britain, mainly concentrated in Norfolk but also as far north as Tyneside and west to Devon.
The butterfly is very similar in appearance to the small tortoiseshells commonly found in gardens across Britain but the scarce tortoiseshell tends to be larger, with yellow legs and a yellow patch on its upper forewing instead of white.