Shiny, metallic blue or green; 1/4- to 3/8-inch.
Bottle flies are one of the first insects to reach a dead animal, and the sudden appearance of dozens of them within a building signals a dead rodent, bird or other animal in the wall, ceiling, attic or crawl space. They breed in garbage containers, dumpsters and decaying vegetative matter. They are attracted to buildings by food odors and also warm or cool air currents coming through cracks around doors and windows.
Bottle flies feed on a variety of food materials but prefer fermenting or decaying organic matter.
Fly control is challenging because their larval sites must be located and eliminated for success, and these sites may be some distance from where the adults are a nuisance. Throw trash away in trash cans in plastic bags, and locate trash receptacles as far from the building as possible. Keep doors and windows closed unless they are equipped with a tight-fitting screen. While a dead animal behind a wall or in a crawlspace is not always easily found, if you suspect a dead animal it must be removed.