Pseudoparasites

invertebrate animals that accidentally penetrate the body of an animal or human being and remain there for some time, alive and causing harm. Some pseudoparasites (for example, the larvae of house flies and gray flesh flies, cheese skippers, and various species of myriopods) can reach the alimentary canal with food and cause a variety of disorders. Sheep maggots are found in wounds and ulcers and some myriopods are found in human nasal passages.