screwworm

screwworm, (genus Cochliomyia), any of four species of North and South American blow fly species named for the screwlike appearance of the larva’s body, which is ringed with small spines. Screwworm maggots are serious pests that attack livestock, deer, and other animals, including humans. The true screwworm, or New World screwworm (Cochliomyia hominivorax), and the secondary screwworm (C. macellaria) develop in surface wounds of domestic and wild animals and occasionally of humans. Each female deposits 200–400 eggs near an open wound or mucous membrane. The larvae burrow into the tissue and, when mature, drop to the ground to pupate. Severe infestations (myiasis) may kill the affected animal, sometimes in as little as one or two weeks.