Which rare butterfly, found only on a few limestone hills in Gloucestershire and reintroduced to other sites, is named for the distinctive white fringe on its wings?

• A Small blue
• B Chalkhill blue
• C Adonis blue
• D Large blue ✓

The large blue (Phengaris arion) was declared extinct in 1979 before being successfully reintroduced from Swedish stock in the 1980s after discovering its complex relationship with a specific ant species.