Pest Facts: Phorid/Humpbacked Fly

Though they may look similar to Fruit Flies , phorid flies can often be identified by their habit of running over surfaces rather than flying, giving them the nickname "scuttle fly".  The arched thorax of the adult gives them a humpbacked appearance, which gives rise to the common name humpbacked fly. Infestations often require methodical inspection techniques to uncover the point source(s). Their ability to utilize small amounts of pooled water containing organic material for larval development sites provide a wide range of harborage areas in most accounts. 

Color: Dark Brown to Black
Legs: 6
Shape: Small oval
Size: 1/16-1/8 ”
Antennae: Yes
Region: Found throughout U.S.

Habits

Besides their characteristic short and erratic flight, adult phorid flies have a peculiar habit of rapidly running across windows, TV screens, tables, walls, and plant foliage.  The entire life cycle last 25 days or more depending on the environmental conditions, and the availability of food. Some species occur on fungi, while others are parasites of various insects, including ants and termites. Sometimes phorid larvae are of economic importance in the mushroom industry.   

Habitat

They are attracted to moist decaying matter, where they both eat and lay eggs.  Some species are known as "coffin flies" because they've been observed to live in dead bodies even after burial.

Threats

Because they are drawn to food, phorid flies can be a threat to human health by transmitting various contaminants to food.

Prevention

  • Repair faulty plumbing, install drain traps, and check trap function.
  • Eliminate standing water.
  • Clean floor drains and drip pans with a brush and flush at least twice a month.
  • Clean air ex-changer units.
  • Thoroughly clean floor areas under food preparation surfaces and equipment twice a month.
  • Clean trash receptacles, recycling bins and compactors twice a month.
  • Discard old cut flowers and clean, remove or dispose of vases.
  • Avoid over-watering plants.
  • Food service accounts need to practice proper warehousing to ensure rotation of Fresh produce, such as onions and mushrooms.

Mechanical/Exclusion:

  • Seal cracks and crevices in areas where moisture can accumulate, e.g., sink splash boards.
  • Accessible floor drains can be cleaned of organic material using an electric drill fitted with a 12 inch extender or a 3 inch diameter wire sanding wheel. This set-up is aided by running tap water into the drain during and following the procedure to flush away debris.
  • Double-sided tape can be used on the bottom of window panes to trap adult flies. A razor blade easily removes the tape after use.
  • Some phorid fly species are attracted to lights, and might be drawn to insect light traps.
  • Replace mercury-vapor lamps at entrances with sodium-vapor lamps and/or locate exterior lights away from the building and direct the light back toward it.

Chemical:

  • Contact your pest control professional if the above referenced treatments do not work.
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