Speckled Wood Butterfly (Pararge aegeria)
The eggs are laid on a variety of grass host plants. The caterpillar is green with a short, forked tail, and the chrysalis (pupa) is green or dark brown. The species is able to overwinter in two totally separated developmental stages, as pupae or as half-grown larvae. This leads to a complicated pattern of several adult flights per year.

Speckled wood butterfly
An attractive looking butterfly.