Fly specks seen on surfaces visited by house flies are the excreted wastes. Female house flies deposit their eggs in decaying matter such as grass clippings, garbage, and human and animal excrement. Horse manure is the preferred breeding medium. Each female deposits about 100-150 eggs on appropriate food. Eggs hatch into worm-like creatures called maggots.
Maggots lack definite heads, eyes, antennae, and legs.
Their bodies are pointed at the front end and gradually widen at the rear. Fly maggots feed on the material in which they find themselves. Following three larval molts, mature larvae stop feeding and burrow into drier surrounding areas, where they pupate. The pupa is a chestnut brown, oval object within which the larva changes into an adult house fly. Adults mate within one to two days after emerging from their pupal cases.