The Common Nettle is a primary larval food plant for four species of UK butterflies. I found quite a number of peacock butterfly caterpillars feeding on nettles in my local area during June, the eggs had been laid in May. It is always worth checking that nettles do not have any caterpillars on them before removing them. Also, do leave some nettles, as they are also larval food plants for the Comma, Red Admiral and Tortoiseshell butterflies. A great plant to have!