Most Wanted: Phorid Fly


June 22, 2015

Phorids (Megasellia scalaris) fly from fermenting filth, frequently fouling food and inflicting infections.

Aliases: Coffin fly, Humpbacked fly, Scuttle fly

Description: Adult flies are 1/10- to 1/16-in. long, with a wingspan of less than 1/4 in. The thorax is dark brown or tan with a distinctive humped appearance. Their wings have no cross veins.

Life Cycle: Phorid fly life cycles involve complete metamorphosis — eggs, larvae, pupae and adults. During a 12-hour period, each female places about 40 eggs on decaying organic matter. Larvae emerge from eggs within about 24 hours; they feed for eight to 16 days, depending on conditions. Larvae display the unique behavior of swallowing air when exposed to pools of liquid, which allows them to float. Larvae crawl to drier spots to pupate, and then adults emerge. Under ideal conditions, the life cycle is complete in about 14 days. Under lesser conditions, it might take as long as 40 days.

Habitat: Phorid fly developmental habitats include environments such as mausoleums, homes, public restrooms, floor drain systems, Dumpsters, trash containers, carrion or rotting meats, vegetable wastes, and failing sewer vaults and pipes.

Food: Larvae feed on fermenting organic materials, carrion, sewage and feces. Adults feed on carbohydrates and exudates (sweat, blood, etc.).

Range: Phorids are well established throughout the United States, especially within aging and decaying urban infrastructures.

Significance: As an endophilic (interior-loving) species, phorid fly populations are increasing. Factors include heavy rains, decaying biological waste-handling systems, and aging municipal sewer and septic systems that collapse or fail because of blockages. Flies easily locate and exploit these failures.

Dr. Stuart Mitchell, D.O., Ph.D., M.P.H., B.C.E., a board-certified physician and entomologist, is principal technical specialist for PestWest Environmental, as well as PMP’s Technical Editor. He can be reached at or 515-333-8923.

About the Author

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MITCHELL, D.O., DVM, PsyD, BCE, is technical director of PestWest, and a frequent contributor to PMP.

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