Creature Feature

Phorid Flies

Phorid flies are small flies that mostly breed in decaying animal or plant material. Some are parasites, as in the genus Pseudacteon, which contains species that have been released in the United States to biologically control red imported fire ants. The larvae of these phorid flies decapitate worker ants by consuming the contents of the head and causing it to fall off. 

In structural pest management, phorid flies are found breeding in a wide variety of materials. They are common in medical waste and corpses and, therefore, in healthcare facilities and mausoleums. Where animals are cared for, they can breed in soiled bedding and feces. In food handling establishments, they can breed anywhere moist organic matter is allowed to accumulate, for example, underneath equipment and in poorly maintained grease traps. The worst-case scenario is when a plumbing line breaks underneath a building’s foundation and phorid flies breed in the soil moistened with organic matter, then enter the building through openings in the floor.

Ideally, phorid flies are best managed by finding and removing breeding sites. This is not always possible, such as in mausoleums. If breeding sites are difficult to maintain clean, a borate solution can be applied to essentially convert the breeding medium into a toxic bait that will kill the larvae. Insect light traps can help remove a significant number of adults from the environment. An appropriately labeled fly bait can also be applied to surfaces where adult flies tend to congregate.