Phorid Fly

The phorid fly is a small fly that resemble fruit flies in appearance, but unlike the fruit fly, have visibly expanded, laterally flattened hind femora and lack the red eye color that is the classic trademark of the fruit fly.  Phorid flies are approximately 1/8 inch in length, including the wings.  The most prominent feature of this fly is the rounded, elevated shape of its thorax.  The high arch of the thorax gives it the common nickname of humpbacked fly.  The adults exhibit a characteristically short and erratic flight.  The most easily recognized behavior of the adult fly is running rapidly across surfaces when disturbed.  Under similar circumstances, most flies immediately take flight in response to nearby movement.

The reproductive potential of these flies is tremendous and very large numbers may appear in a short time.  The female can deposit about 40 eggs in a 12 hour period, and lay approximately 500 eggs during her lifetime.  The tiny eggs are deposited on or near the surface of decaying organic matter.  Larvae emerge in 24 hours and feed for 8 to 16 days.  The larvae then crawl to a drier spot to pupate.  The life cycle from egg to adult can be completed in as little as 14 days under warm, moist conditions, but may take as long as 37 days under cooler or less than optimum conditions.

In structures, these flies can be found breeding wherever moisture exists around plumbing and drains in bathroom and kitchen areas, garbage containers, garbage disposals, crawl space areas, wall voids, or basements where plumbing leaks provide wet areas supporting mold or fungal growth.  These breeding areas are occasionally very difficult to locate.  Other areas to check are where any fruits or vegetables are stored outside of refrigerators or coolers.  Also inspect recycling bins, garbage cans, damp mop closets and used rag storage bins, and beneath refrigerators where dust and other organic deposits can be found in damp evaporation pans.  When searching for breeding sources, remember that the larva can only survive in decaying organic matter that remains moist.

Prevention Tips

Clean any moist, organic areas, especially drains, with appropriate cleaners and a stiff brush to remove any film.

Hidden areas under kitchen equipment and sinks where moist, organic debris can accumulate should not be overlooked.

If these measures do not help, a plumber may be needed to check for hidden cracks and leaks in plumbing lines around your home.

Food should not be left out for long periods of time.

Trash should be kept covered and removed often.

Rinse beverage cans or bottles if you recycle.

Make it a habit to clean your garbage disposal.