How are maggots produced?

Maggots hatch from fly eggs. Because fly eggs are so small they normally go unnoticed, many people mistakenly believe maggots appear on their own. Flies prefer to lay eggs in humid, protein-rich environments, depositing them while they feed, which is why toilets and garbage sites tend to have more maggots.

Fly eggs hatch quickly, turning into maggots in about six hours. After hatching, the maggots crawl toward higher, drier places, harden into pupae in the dry environment, and finally break out of the pupa as adult flies.