Silver Washed Fritillary (Argyniss paphia)
It is essentially a butterfly of woodlands, especially areas of well established woodland, both deciduous and coniferous. This is certainly a butterfly of the south and there are several sites in Dorset where it can still be found.
Not as common as it once was, where it does occur it can be quite numerous, especially at the peak of its flight time, the whole month of August.
It had just the one brood each year and the eggs are laid in the crevices of tree bark (notably oak) and that is where the larvae return to to hibernate before emerging as adult butterflies the following summer.