Phorid Flies Identification Guide

Phorid Fly Identification Guide

Physical Characteristics

Phorid flies are small insects, about 1 to 4 millimeters long. That makes them roughly the size of a fruit fly or smaller. Their most obvious feature is a noticeable hump on their upper body when seen from the side. This hump is why they are often called “humpbacked flies.” The arched shape helps tell them apart from other small flies in homes.

These flies have short antennae on the front of their head. Small bristly hairs often hide them. Their color ranges from tan to yellowish-brown or black. Some species have darker stripes on the abdomen. The back legs are larger and flatter than the front legs. This design helps them jump.

The wing pattern also helps with identification. Phorid flies have thick veins near the front edge of each wing. Three to four lighter veins run across the rest of the wing. Overall, their wings look simpler than most other flies.

House flies buzz around and land directly. Phorid flies act differently. When disturbed, they run fast across surfaces in short, jerky bursts before flying away. This “scuttling” behavior is so unique that pest experts often use it to identify them.

Common Species

The two most common household phorid fly species in North America are Megaselia scalaris and Dohrniphora cornuta. Megaselia scalaris is especially common. It is sometimes called the coffin fly or scuttle fly. This species eats many different things and can breed in a wide variety of organic materials.

The family Phoridae is large and diverse, with over 4,000 species found worldwide. Most species live outdoors where they help break down dead plants and animals. However, several species will move indoors when they find good breeding conditions.

Phorid Fly Behavior and Biology

Phorid flies go through four life stages: egg, larva, pupa, and adult. In warm conditions, they can complete their whole lifecycle in just 14 days. In cooler weather, it may take up to 37 days.

Female phorid flies reproduce quickly. A single female can lay 20 eggs at a time and up to 40 eggs in just 12 hours. Over her 30-day lifespan, one female can lay 500 to 1,000 eggs. The eggs are tiny and boat-shaped. Females usually place them at the edge of breeding material.

Larvae hatch within 24 hours in warm conditions. These legless, whitish-gray larvae feed on decaying organic matter for 8 to 16 days. Then they crawl to a drier spot to pupate. The pupae are oval and slightly flattened with small breathing horns. Adults emerge about one week later.

Adult phorid flies are strong fliers for their size. With help from wind, they can travel up to six miles in 24 hours. However, they usually fly short distances and prefer to run across surfaces. Adults are most active during the day and are drawn to light.

Breeding Habits and Habitat

Phorid flies can breed in more types of materials than almost any other fly that infests buildings. This makes them hard to control. Potential breeding sites are many and often hidden from view.

Common indoor breeding sites include:

• Organic buildup inside drain pipes and garbage disposals
• Rotting produce, especially potatoes and onions
• Trash containers and recycling bins
• Dirty mop heads and cleaning equipment
• Areas with pet waste or spilled pet food
• Decomposing matter in wall voids or beneath floors
• Broken sewer lines and damaged septic systems
• Wet, compacted soil in potted plants
• Grease traps and floor drains in commercial kitchens

Outdoors, phorid flies breed in decaying plant matter, animal waste, and dead animals. Problems start when these flies find good breeding spots inside buildings.

Moisture is essential for phorid fly breeding. Any area that stays damp and has organic matter can become a breeding site. This is why water leaks, condensation, and drainage problems often go hand in hand with phorid fly infestations.

Treatment Methods for Phorid Flies

Good phorid fly control means finding and removing the breeding source. You can kill adult flies in many ways, but new flies will keep appearing as long as larvae have somewhere to grow. Here are methods that work well for treating phorid fly infestations:

Source Identification

Before treatment can work, you must find all breeding sites. This can be hard because phorid flies often breed in hidden areas. Start by checking the obvious spots:

• Check stored produce, particularly potatoes, onions, and other root vegetables
• Examine all floor drains, sink drains, and garbage disposals
• Look under and behind appliances where food debris may accumulate
• Inspect pet areas for waste or spilled food
• Check potted plants for excessive moisture or decaying organic matter

If you have removed obvious sources but flies keep coming, look for hidden breeding sites. Sticky traps placed around the home can show where flies are most active. Ongoing infestations often point to broken plumbing or moisture problems in the structure.

Sanitation and Source Removal

The key to phorid fly control is removing the organic material where larvae grow. This takes more than surface cleaning:

• Dispose of all rotting produce and clean storage areas thoroughly
• Clean drains with enzymatic cleaners that break down organic buildup. Standard bleach and chemical cleaners do not remove the slimy film where larvae feed as well
• Clean under appliances, around trash containers, and in other areas where food debris accumulates
• Address any moisture problems that create conditions favorable for breeding
• Clean and dry mop heads, sponges, and other cleaning tools that may harbor organic matter

In commercial kitchens and food service areas, pay close attention to grease traps and floor drains. Also check spots where pressure washing may have pushed food debris into cracks.

Addressing Hidden Sources

When phorid flies keep coming back after thorough cleaning, look for hidden breeding sources. Broken sewer lines under concrete slabs are a common cause of ongoing infestations. Signs that may point to sewer line problems include:

• Flies emerging from specific locations repeatedly
• Unusual odors, especially near floor drains
• Previous plumbing problems or slow drains
• Damp spots on floors with no obvious source

A plumber with a camera can inspect pipes to find damage. Smoke testing can also show cracks in sewer lines by revealing where smoke enters the building. To eliminate these hidden breeding sites, broken pipes must be fixed and contaminated soil removed.

Monitoring and Prevention

After getting rid of an active infestation, stay alert to prevent them from coming back:

• Maintain clean drains with regular enzymatic treatments
• Store produce properly and dispose of overripe items promptly
• Keep trash containers clean and tightly sealed
• Address moisture problems and plumbing leaks immediately
• Clean under appliances and in hard-to-reach areas regularly
• Use sticky traps to monitor for early signs of new activity

Insect light traps can catch adult flies but will not solve an infestation by themselves. They work best as monitoring tools to spot activity before fly numbers grow.

References

• Phorid Flies - NC State Extension
• Phorid Flies - Penn State Extension
• Flies - UC IPM
• Small Flies - University of Kentucky Entomology