Adults are 1/4 inch to 3/8 inch long with compact, wide bodies.
Blow flies are usually shiny and metallic ranging from bright blue to coppery orange to almost black.
Blow flies are extremely common. They are loud buzzing fliers that are attracted to lights, food odors and warm/cool currents around windows and doors. The sudden appearance of dozens of blow flies in a building could indicate there is a dead rodent, bird, or other animal in the wall, ceiling or attic.
Blow flies are scavengers that feed on trash, decaying animals and animal feces. They are usually the first insects to reach a dead animal. Blow flies are an important part of the decomposition process because they recycle nutrients back into the soil.
Female blow flies lay several hundred eggs on or near suitable food sources such as garbage containers, dumpsters and compost piles. Tiny maggots hatch from eggs in 6 to 48 hours then undergo several stages before becoming adult flies. It takes 16 to 35 days for the development from egg to adult.
Maggots have hook-like mouth parts that tease apart tissues in which they live. Adults have sponge-like mouth parts similar to those of house flies. Blow flies are important decomposers of dead animals and other rotting organic material, such as decomposing plant material. Their larvae are frequently used in forensic science to determine facts about a crime scene.