From egg to adult, house flies live anywhere from two weeks to one month. A female fly lays 75 to 100 eggs at a time. The eggs hatch a day later into tiny, legless worms called maggots. The maggot stage lasts 14 to 36 hours.
At the end of the maggot stage, the worms crawl to a dry spot to transform into pupae. The adult fly emerges from the pupa and lives another two weeks to a month longer. Female flies are ready to mate just 36 hours after coming out of the pupa stage. They only mate once, but the females hold on to the sperm to continue laying several batches of eggs before dying.