These small flies are about 1/8 inch long. They may appear to be like other gnats indoors, except that they have an erratic walking behavior that is characteristic and separates them from other indoor flies.

Family Phoridae. These flies may breed in clogged drains, especially in septic drains and sewer pipes that are leaking into the ground. They may be found throughout the year in some infestations.

The breeding site must be located to achieve control. Check all locations that have organic matter, such as sewer lines and other drain pipes, both indoors and outdoors close to the structure.