This is an edition of The Atlantic Daily, a newsletter that guides you through the biggest stories of the day, helps you discover new ideas, and recommends the best in culture. Sign up for it here. The first thing you should know about the New World screwworm is that it isn’t actually a worm; it’s a fly. At the larva stage, it twists into the flesh of its host, devouring it from within. These wormlike maggots feed on all kinds of warm-blooded animals (the fly’s scientific name is Cochliomyia