blowfly, name for flies of the family Calliphoridae. Blowflies are about the same size as, and resemble, the housefly; because they are usually metallic blue or green they are also called bluebottle or greenbottle flies. The eggs are laid on the material that serves as food for the larvae, e.g., decaying flesh and other organic matter. Blowflies are often carriers of disease, such as dysentery. The larvae of certain species of blowfly, raised under germ-free conditions and known as surgical, or medicinal, maggots, are used to consume dead and dying tissue and thus promote healing. The screwworm fly, common in the S United States, may invade wounds or orifices in wild and domestic animals and sometimes in humans. If females, which mate only once, mate with a sterile male, the eggs fail to hatch. Blowflies are classified in the phylum Arthropoda, class Insecta, order Diptera, family Calliphoridae. See insect.