Phorid flies are very small, even for flies, being about 2mm long. They have a distinct humpbacked appearance when seen from the side. Occasionally, phorid flies become a problem indoors. Though they are more active in the summer months, they are frequently seen even in cold weather.

 Phorid flies breed in decaying animal or vegetable material, including corpses and feces. The breeding site must be moist and somewhat warm. Areas around drains, particularly floor drains, garbage disposals, trash or garbage areas, and areas around any plumbing leak are common trouble spots. Under the right conditions, a rodent carcass inside a wall can produce thousands of these flies.

Like all flies – phorids start live and an egg that hatches into a larva. Fly larvae are often called maggots. These larva shun light and prefer to feed in dark places. They grown as they feed, and at some predetermined point are ready to pupate into the adult, winged stage of the fly. Mating occurs almost immediately. And if the breeding medium is still sufficiently moist, more eggs may be laid on it, thus several generations of flies can arise from one petrified rat carcass. It can be very difficult to find the breeding sites of these flies. Perhaps the worst scenario of all is phorid flies breeding in soil contaminated by a break in the underground sewer line. We have seen this happen many times. A crack, or leak in a sewer line allows much water, along with the raw sewage to leak into the soil surrounding the pipe. Adult flies find this area, possibly by being able to detect and follow minute traces of methane and other sewer gases. Eggs are lad in the contaminated soil and the process is underway. A problem such as this is not easily solved. First, the leak must be located – after this the floor will have to be broken up and the leak fixed. This is the easy part. Now all the contaminated soil will have to be removed and replaced. This can easily be several tons of soil Possibly the worst part of all is that, when the job is done, you kind of have to thank the phorid flies for calling your attention to a potentially dangerous leak, which would have to be corrected whether there was an insect problem or not.