New butterfly species found in British Isles

A new species of butterfly has been found in the British Isles – the first to be discovered here for nearly a century.

The new species looks identical to the Wood White but is physically incapable of interbreeding with it.

Entomologists have so far only found the new butterfly in Ireland but they believe it might also inhabit Britain as a species living "incognito", being mistaken for the normal Wood White.

The discovery could explain why Wood Whites in Britain are mainly found in woodland habitats and are in decline while the "Wood Whites" of Ireland are expanding and live in open habitats, such as road verges, scrub and grassland. Brian Nelson and Robert Nash from the Ulster Museum, working with Maurice Hughes and Martin Warren from the Butterfly Conservation charity, have tentatively called the new butterfly Leptidea reali and given it the common name of "Real's Wood White".

Dr Warren said: "This is an exciting and important discovery, which helps to explain the puzzle of why the Wood White has fared so differently in Ireland compared to Britain.

"It has also highlighted the need for renewed effort to conserve the last remaining British populations of this highly threatened species."

Scientists first documented the two species in 1988 after analysing specimens collected in the French Pyrenees – known as Leptidea reali – but this is the first time that both species have been found living in the British Isles. "You can't tell them apart by looking at their wings. You have to look at their genitalia, which determines who they can breed with," Dr Warren said.

The last new butterfly species to be discovered in the UK was the Essex Skipper in 1889, and the last to be found in Ireland was the Pearl-bordered Fritillary in 1922.