Adults are 1/16 to 1/4 inch long and dark brown to yellow in color. Phorid flies may be confused with fungus gnats, especially since they often appear indoors. The most obvious characteristic of the phorid fly is the humpbacked appearance of the thorax from the side view. The wings have several dark veins. Mature larvae are 3/8 inch long, creamy to grayish white, and tapered at the head end. These larvae have small but visible projections on the rear end.

Adult females lay eggs in larval food sources, which vary widely but are always composed of moist rotting matter. Adults may feed on flowers or the larval food. Several species are breeders in human corpses, earning them the name "coffin flies," and they can be problematic in mortuaries and mausoleums. Other species are of concern in hospitals, where larvae have been found in open wounds of patients. Still others are associated with sewage. Their habit of running across a surface rather than taking flight right away earns them the name "scuttle flies.

The filthy habits of phorid flies make them potential disease carriers. When phorid flies become numerous inside a structure, they almost always indicate a problem with sanitation that needs to be corrected. They will breed in any moist area with organic matter and have been found in rotting potatoes and onions, mop heads and buckets, beneath appliances, in garbage disposals, elevator shafts, and drains. Overwatered houseplants can breed fungus gnats or phorid flies, 2 species that are commonly mistaken for each other. When phorid flies appear inside a structure for weeks or months, it often indicates a more serious problem: a broken sewage pipe beneath the slab foundation. Consider this if the structure was built on slab and look for cracks in the slab if there is access. Place inverted clear plastic cups or tape over the suspected entryway to confirm the origin of flies from beneath the slab. A plumbing contractor should be consulted to examine the sewer line using a fiber optic scope or test for leaks by injecting colored smoke into the line to determine if the smoke escapes from cracks in the floor.