Descriptions of blow and flesh flies
Blow flies and flesh flies are very common flies associated with dead animals. The larvae (maggots) of these flies feed on dead animal tissue and as such are beneficial in nature as decomposer of dead animal carcasses. The appearance of the flies or maggots in the house typically indicates that an animal (i.e. rodent, bird, etc.) has died within the walls or in the attic.
Life cycle of blow and flesh flies
Blow flies and flesh flies are attracted to recently deceased animals, where they lay their eggs. The larvae infest the animal carcass for 5-10 days before they leave the carcass and wander in search of a dry place to pupate. These maggots are unsavory but harmless.
Maggots that are left to develop turn into adult flies in 5-7 days. These are large, sluggish, black or shiny green or blue flies. These flies are harmless. The flies will not deposit eggs or furtherdevelop inside the house. By the time the flies emerge, the original carcass is too old and dry for reinfestation.
Management of blow and flesh flies
The only necessary control for flesh fly maggots is to vacuum or sweep them up and discard. Then check for dead animals in the walls, attic, etc. Control adult flies by swatting or using a ready-to-use indoor insecticide labeled for fly control.
Do you live in Iowa and have an insect you would like identified?
The Iowa State University Plant & Insect Diagnostic Clinic will identify your insect, provide information on what it eats, life cycle, and if it is a pest the best ways to manage them. Please see our website for current forms, fees, and instructions on preserving and mailing insects.
Contact information for each states diagnostic laboratory for U.S. residents. If you live outside of Iowa please do not submit a sample without contacting the Plant & Insect Diagnostic Clinic.