To see one, look in sheds, outhouses, farm buildings, natural hollows in trees, caves, rock crevices and stone walls.
| Winter is a difficult time for adult butterflies and moths because of the low temperatures and there being little food about. Many get around the problem by changing their life cycles to avoid being an adult in the winter. Most species will instead spend the winter safely as an egg, caterpillar or in a chrysalis. However, some species of butterfly will hibernate as adults during the cold winter months, including Peacocks, Small tortoiseshells, Red Admirals and Brimstones. A few may wake up on warmer winter days, but it risks wasting energy and with few flowers around to top up with nectar, they could die. Most butterflies will not become active or wake from hibernation until the first warm days of spring, usually in early March, when the first flowers appear.
DO NOT DISTURB THEM. If they wake up, they will waste precious energy and may die before spring.
For more info see
https://www.britishbutterflies.co.uk/winter.asp