Some books list this family as Nemeobiidae. These butterflies are commonly known as the metal marks because of the metallic-like spots on the wings. There are over 1500 species world wide, but just one species in Europe, see below.
The Duke of Burgundy, Hamearis lucina, above is found in southern England, but is rare in the north, and absent from Scotland and Ireland. There can be two generations a year in the south. In the U. K. they fly from May to August in the south, and May to June in the north.
The yellow eggs are laid on cowslip and primrose leaves. The caterpillars look a little like a woodlouse or even a slug, and feed from June to August. The pupa is attached by silk to the underside of a foodplant leaf until the following May. The adult flies in May and June in sunny woodlands, clearings and wildflower meadows. Adult wingspan is 24 - 34 mm, forewing 14 - 17 mm.