“We keep seeing these little flies in the kitchen, but we can’t figure out where they are coming from. Aunt Sammie says they are fruit flies, but they don’t have red eyes, and the internet says fruit flies have red eyes.”
Phorid flies are the same size as fruit flies, but there are important differences in appearance, behavior, and biology. Their dark eye color alone is enough to distinguish them from fruit flies, which have red or dark-red eyes, and they prefer different breeding sites than fruit flies, though there is some overlap. As with fruit flies, if you are finding phorid flies inside, they are almost surely breeding inside.
Phorid flies have several other names. Humpbacked flies describes their appearance when viewed from the side. Scuttle flies describes the jerky, erratic way they run instead of, or before, taking flight. Coffin flies describes one of the many situations in which they breed.
Phorid fly larvae can breed in a wide range of decaying vegetable or animal matter. This includes things like decaying vegetables, such as a “lost” potato; the organic gunk that accumulates in the bottoms of garbage cans and dumpsters; garbage disposals; pet feces or litter boxes; animal carcasses, such as a dead rat or bird; the decaying organic matter that accumulates in drip pans of refrigerators or air conditioners; wet areas due to plumbing or structural leaks; pots with dead plants or vases of cut flowers that have stood too long; and many similar settings. All it takes is a little decaying organic matter. In commercial kitchens, phorid fly larvae can breed in the organic matter that accumulates in small crevices under the feet of kitchen equipment. Organic matter that accumulates under tile floors that have cracks or missing grout is another potential breeding site. The bottom line is that phorid flies breed in some nasty places and you don’t want the adults hopping around in your kitchen or on your food.
Control: The key to phorid fly control is to find and eliminate their breeding source. Sometimes this is as easy as finding and discarding a “lost” bag of rotten potatoes. The most difficult phorid fly problems to solve involve broken sewage lines under buildings, as phorid flies can establish heavy, persistent infestations in sewage-contaminated soil. Fortunately, the first case is much more common than the latter, but, as described above, phorids can breed in a range of other situations as well. In most cases insecticides are of little or no use; finding and eliminating the breeding source(s) will solve the problem. In commercial settings, such as commercial kitchens, microbial-based cleaners can be used in mop water and in drains to eliminate breeding sites by eliminating accumulations of decaying organic matter in cracks, crevices, and drains.
For more information on phorid fly control see pages 41-43 of Extension Publication 2443, Control Household Insect Pests.
Blake Layton, Extension Entomology Specialist, Mississippi State University Extension Service.
The information given here is for educational purposes only. Always read and follow current label directions. Specific commercial products are mentioned as examples only and reference to specific products or trade names is made with the understanding that no discrimination is intended to other products that may also be suitable and appropriately labeled.
Mississippi State University is an equal opportunity institution.
Bug’s Eye View is now on Facebook. Join the Bug's Eye View Facebook group here.