A butterfly officially classed as extinct in the UK has been seen at sites across southern England, says a conservation charity. In recent weeks there have been a flurry of sightings of the large tortoiseshell in Kent, Sussex, Hampshire, the Isle of Wight, Dorset and Cornwall. It has led Butterfly Conservation to declare the large tortoiseshell a resident breeding species in the country once again, as opposed to a migratory one. The species was once found across England and Wales, but was last recorded as a breeding species in the UK in the 1980s. Adults lay their eggs on elm trees and their decline has been linked to the spread of Dutch elm disease across Europe in the 20th Century. There have been rare sightings over the years since it was declared extinct, but they are becoming increasingly common with 20 reported in recent days.…