There are several flies within a structure that may indicate that you are experiencing a plumbing problem or a moisture problem.
Today we finally got to a solution of a Phorid fly problem. Phorid flies are also known as Coffin flies, Scuttle flies, Hump back flies, Drain flies. The correct term in my opinion is a Phorid or Scuttle fly so that there is no confusion on the insect one is talking about.
These are small flies that run more than they fly. They breed in areas that other insect do not breed in. The breeding medium is typically in an anaerobic mess of organic matter that is high in moisture. This breeding medium in my experience is disgustingly odourous.
A problem of Phorid flies is indicated typically with large numbers of these flies. The Phorid fly will travel to light, you will usually find them on window sills or in a Fly Light Trap.
Fly light Traps are they only method of managing the problem without fixing the problem that caused them to be present . Fly Light Traps only catch the adults.
When a facility encounters Phorid flies one would experience a high number of them daily and they would be visibly annoying. If fly light traps are present in the Fly management program in your facility there would be allot caught. Insect monitors that are present in the pest management program you have would also catch some adults.
In order to to resolve the problem the breeding medium needs to be found. Having a sewer camera service is essential in locating broken sanitary lines under the floor. Once a break in the sanitary line has been located cutting open the floor and excavating is required. Upon excavating you might realize that you require a sucker truck service in order to remove the contaminated substrate. In all cases of Phorid fly and Moth fly issues we have found a substantial amount of grey water under the slab, it needs to be removed.
The following images give you a pretty good idea what needs to be done.