Certain flies are attracted to open wounds on animals or humans. The blow fly is one such fly and the screw fly is another. The fly lands and lays eggs on the open wound. The eggs hatch and the maggots burrow into the wound. This condition is called myiasis. Some burrowing maggots will go deep into the body and lodge in certain places. They may infect the genitalia, anus, intestines, eyes, mouth, ears and sinuses of the host.