The Screwworm Menace: A Dangerous Parasite What is a Screwworm? A screwworm is the larval stage of a type of fly, specifically the New World screwworm fly. These flies lay their eggs on open wounds of warm-blooded animals, including humans. Once hatched, the larvae, or maggots, burrow into the living tissue, feeding on it and causing severe damage. The Dangers of Screwworm Infestation Screwworm infestations