This is one of the few butterflies that hibernate as adults, and you may come across them indoors in the dead of winter. In Britain they first emerge in March, and in mild years they are still seen on the wing as late as October.
In mild winters the hibernation of Small Tortoiseshells is sometimes interrupted on warm January or February days, when they can be seen basking on south-facing walls.
Small Tortoiseshells can be found throughout Europe, from the Mediterranean right into northern Scandinavia (and eastwards through Asia to the Pacific Coast).
In Britain these common and well known butterflies are particularly fond of Buddleia blossom in gardens and on railway embankments; they also take nectar from thistles, and so they are often to be seen on untended banks of spate rivers.
As the specific epithet implies, the larval foodplants of this species are nettles of the genus Urtica, and most commonly the Stinging Nettle, Urtica dioica. In some parts of England, notably the Midlands, the common name Bobby Howler was applied to the Small Tortoiseshell Butterfly, but the reason for this is obscure.
The Large Tortoiseshell butterfly (Nymphalis polychloros) is similar in appearance but does not have the large black patch on the underside of the hind wing. This butterfly is now very rare in Britain and indeed extinct in most regions, turning up occasionally but very locally in parts of southern England and Wales.