This rare British butterfly looks familiar, but its genome tells a very different story

The British swallowtail butterfly (Papilio machaon britannicus) is the U.K.'s only native swallowtail and its largest native butterfly. It's instantly recognizable by its striking light yellow-and-black wings, with twin tail-like markings splashed in bold blue and red. Habitat for this endangered species has largely been limited to the damp bogs and marshes of eastern England, especially the iconic Norfolk Broads, where its life cycle is closely tied to a single host plant, milk-parsley.