The purple emperor is arguably Britain's most spectacular butterfly — the male's iridescent purple wings are only revealed at certain angles. This canopy-dwelling species has specific welfare requirements tied to sallow trees and old oaks.
Purple emperor welfare is tied to the availability of sallow trees in the understorey of mature broadleaved woodland. Sallow — regarded as a weed by many foresters — has historically been removed from woodland. Butterfly Conservation's sallow-planting programme at major woodland reserves (Fermyn Woods, Knepp) has created new breeding habitat. The Knepp rewilding project in Sussex has produced some of the highest purple emperor densities ever recorded in the UK — demonstrating that natural rewilding processes creating sallow-rich open woodland are highly beneficial. Adults that feed on dung and carrion are vulnerable to disturbance from observers who place bait to attract them for photography — intensive baiting and repeated disturbance is a welfare concern.