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Reference: Ohio State University Extension
|Common Name||Scientific Name|
|Humpbacked Fly or Phorid Fly||Megaselia scalaris|
Humpbacked flies can become a nuisance in hospitals (burn units, operating rooms, pathology labs, autopsy rooms, morgues), food establishments (kitchens, soft drink vending machines, garbage receptacles) or homes (faulty septic systems, clogged basement drains, soil of potted plants, drip pans, garbage cans, rotting meat and vegetables). Some are found outdoors in decaying organic matter such as vegetation, animal feces, carcasses of animals, decaying insects and nests of ants, termites, bees and wasps. Flies may run rapidly across windows, TV screens, tables, walls and plant foliage in short, jerky movements, appearing reluctant to fly.
Adult humpbacked or Phorid flies are tiny (1/16 to 1/8 inch long), humpbacked (arched thorax), yellowish-brown insects with a characteristic wing venation. When wings are present, two veins near the front of the wing are very heavy (thickened), terminating about halfway before the wing tip; the remaining three veins are weak (finer), running diagonally not forming any closed cells. The outer third segment of the antennae is much larger than the other two segments and bears a long stout bristle. The head is small with rather large eyes, legs are large with the hind femora laterally flattened (adapted for jumping) and the abdomen short, narrowed and dropping behind. The head and thorax have scattered, large bristles. Larvae are elongated, almost cylindrical, slightly flattened (3/32 inch long), dirty white and tapered at the anterior (front) end. The puparium is boat-shaped (1/8 inch long), light-brown and slightly translucent. Eggs are very small (1/32 inch long) and opaque-white.
Life Cycle and Habits
Humpbacked flies reproduce in moist areas where food and water are present. Eggs are usually laid directly on the decaying material with females laying about 20 at a time (40 eggs over a 12 hour period). Eggs hatch in 24 hours with the three larval stages lasting 8 to 16 days and pupal stage lasting 14 days. The entire life cycle lasts about 25 days or more, depending on temperature, moisture and food available. Females are very strongly attracted to odors of decaying animal material and readily lay eggs on or near it. Larvae have been found feeding in sour milk, decaying plants (corn, onions, pineapple), open wounds of animals and humans, decaying animal and human flesh (cadavers), animal and human feces, decaying insects, laboratory culture media, clogged drains, crypts in a mausoleum, human tissue at hospitals, soil of potted plants, cut flowers in vases, garbage cans, garbage disposals, etc. Larvae do not initiate wounds or attack healthy animals or humans.
Adults have sponging type mouthparts and are sometimes confused with vinegar or fruit flies and fungus gnats due to their small size, flight pattern and breeding habits.
Humpbacked flies do not bite humans but may become a nuisance by their presence in large populations. Since they originate in filthy conditions, there is a possibility of transmitting certain diseases. These flies can cause much anxiety and embarrassment by their presence in hospital burn units, pathology labs, autopsy rooms, morgues, mausoleums, etc. The most important task is to locate and eliminate the larval breeding sources. Carefully inspect the facilities for concentrations of adult flies and decaying odors.
Blacklight electrocuting devices are not effective control agents, but can monitor populations. Also, sticky traps can be used to monitor populations. Flies are attracted to natural light and will fly erratically around lights at night. Sticky traps, placed in several locations with a yellow background color, are most attractive. Place traps after closing and remove for examination before opening if customers are of concern. Monitor at one or two month intervals.
Indoors, thoroughly clean drain pipes and traps with a good, stiff, long-handled brush. Often, it is best to remove the drain trap and use a "snake" in clogged drains to clean the pipes of all gelatinous material, removing the larval food source. Bleach or commercial lye solutions may be poured into the drain pipes after a thorough cleaning by brush, carefully flushing with boiling water. The use of a caustic material (drain cleaner) is effective with repeat applications.
Use a dehumidifier or fan to eliminate or reduce unnecessary moisture or dampness. Avoid accumulation of wet organic matter in roof or ground drainage sites. Keep these areas free of wet leaves. At temperatures of 50 degrees F or lower, life cycles of these flies are suspended. Temperatures around freezing for one to four weeks will kill many insects. Temperatures of 130 to 136 degrees F for a few hours will give good kill. Use high pressure sodium vapor lights (not mercury vapor lights rich in ultraviolet wavelengths) away from doors and windows if exterior light is needed. Damp organic matter of potted plants and pollen on indoor flowers can support these flies. Keep excessive vegetation (grasses, leaves) away from the foundation. Dispose of dead rodents and old bird nests. Clean garbage containers and seal (caulk) cracks and crevices to prevent entry sites into structures.
Indoors, aerosol space sprays of pyrethrins or resmethrin, labeled for small flying insects, will kill adult humpbacked flies, providing temporary control. Repeat applications will be needed to kill newly emerging humpbacked flies until the feeding and breeding source of the larvae are found and removed. Outdoors, licensed pest control operators or applicators can use cyfluthrin (Tempo) or permethrin (Flee) applied to dirty garbage cans, compost piles, outside sewers, window frames, etc. Read the insecticide label carefully and follow directions and safety precautions.
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