Maggots come from the eggs of flies. They are the larval stage of flies. Maggots transform into pupae, which later molt into fully formed adult flies.
An adult fly lays small eggs in an area in which maggots are likely to find food. This includes garbage, animal droppings, raw meat and the carcasses of dead animals. Some maggots prefer sweeter foods like rotting fruit. Each egg produces one maggot. The maggots eat and grow rapidly. Periodically, maggots molt out of their exoskeletons and grow a new one. The amount of times a maggot molts depends on its species. After a specific amount of time, each maggot forms a protective pupa. Inside the pupa, the maggot morphs into an adult fly.