As the evolved form of the butterfly is much bigger than the un-evolved, it would be unreasonable to expect the wings to still work, and indeed they don't. The wings have regressed to the point of being used only as a show of colour or importance. Flight was still possible, as an artificial form of wings had been developed long ago that used the same muscles as the wings did, but these were only widely used by the army and weren't usually worn in public.
Copyright 1999 Ian Rennie, for Remiel Productions.