Medium-sized flies from 1/4-inch to 3/8-inch in length.
Shiny, metallic blue, green, or copper, depending on the species.
Blow flies and bottle flies are important scavengers in nature as they are one of the first insects to reach a dead animal. These flies are part of the decomposition process that recycles nutrients back into the soil. The maggots of these flies may be used by forensic entomologists to place the time of death in murder cases. They also breed in garbage containers, dumpsters, and decaying vegetative matter (e.g., compost piles).
These flies are extremely common and can be found one to a few at a time in homes or businesses during the warm summer months. They are attracted to buildings by food odors and also warm/cool air currents emitting through cracks around doors and windows or through doors propped open for ventilation purposes. The sudden appearance of dozens of blow flies or bottle flies within a building signals a potential dead rodent, bird, or other animal in the wall, ceiling, attic, or crawl space.
In most cases involving blow flies and bottle flies around homes, the problem is twofold: (1) flies are being attracted to the building by trash containers or pet manure and (2) openings (e.g. doors) exist that are permitting flies to enter. To minimize problems with flies, take the following steps: Throw trash away in trash cans in plastic bags. Bags reduce odors associated with garbage and trash thus attracting fewer flies to the area. Locate trash receptacles as far from the building as possible. Those flies that are attracted to the area will therefore be away from the back door. Keep doors and windows closed unless they are equipped with tight-fitting screens. Ensure all edges of doors and windows have tight weather-stripping. Flies can squeeze through amazingly small cracks. If the presence of these flies is due to a dead animal within the building, finding the location of the carcass and its removal is necessary, but is not easily accomplished.