If a species is horrible enough, do we have the right to kill it forever? Seventy years ago, a nightmare parasite feasted on the live flesh of warm-blooded creatures in North America: the screwworm. That is, until a young scientist named Edward F. Knipling discovered a crucial screwworm weakness and hatched a sweeping project to wipe them out. Knipling’s seemingly zany plan to spray screwworms…