House Flies Identification Guide

House Fly Identification Guide

Physical Characteristics

House flies (Musca domestica) are medium-sized flies about 4 to 8 millimeters long. That is roughly the size of a small pea. The easiest way to spot them is by the four dark stripes on their gray upper body.

Adult house flies have large red-brown eyes. In males, the eyes almost touch. In females, the eyes are farther apart. Their bodies are covered with fine hairs. They have a dull gray color with yellow patches on the sides of the belly.

House flies do not bite. Instead, they have sponge-like mouthparts. They spit saliva onto food to dissolve it, then sponge up the liquid. This is one reason they spread germs so well.

House flies are strong fliers. They can travel several miles from where they breed. You will often see them buzzing around kitchens and landing on food over and over.

Common Species

The common house fly (Musca domestica) is the most common fly found in homes across North America. It came from central Asia but has spread around the world. You can find it on every continent except Antarctica.

Other flies that look like house flies include:

• Lesser house fly (Fannia canicularis): A bit smaller and thinner. Often flies in circles under lights or hanging objects.
• Face fly (Musca autumnalis): Looks similar but is mostly found near cattle and other farm animals.
• Stable fly (Stomoxys calcitrans): Looks like a house fly but bites and feeds on blood.

House Fly Behavior and Biology

House flies go through four life stages: egg, larva (maggot), pupa, and adult. In warm weather (77 to 86 degrees), the whole cycle takes just 7 to 10 days. This fast cycle lets fly numbers grow quickly in summer.

Female house flies lay 75 to 150 eggs at a time in moist, rotting material. One female can lay 500 or more eggs in her life. Eggs hatch in 12 to 24 hours when it is warm. The white, legless maggots eat the rotting matter around them for 3 to 7 days. Then they move to a drier spot to pupate.

The pupal stage lasts 3 to 6 days. During this time, the maggot changes into an adult fly inside a brown case. Adults push out of the case and can fly within a few hours. Adult house flies live 15 to 30 days. They may live longer when it is cooler.

Feeding Habits and Disease Spread

House flies like garbage, animal waste, rotting plants, and human food. They cannot eat solid food. They must spit up saliva and stomach juices onto food to turn it into liquid before eating.

Because flies land on filth and then on your food, they can spread germs. Studies show house flies can carry over 100 types of germs. These include bacteria, viruses, and parasites. Diseases linked to house flies include:

• Typhoid fever
• Cholera
• Dysentery
• Salmonella
• E. coli
• Eye infections

Good sanitation and keeping food covered are key to stopping flies from spreading illness.

Seasonal Activity

House flies are most active in warm weather when they breed fast. In the north, outdoor fly numbers drop a lot in winter. However, flies can still live indoors where it is warm and food is around. In southern states, house flies stay active all year.

Peak fly season runs from late spring through early fall. Warm, humid weather speeds up breeding. Cool weather slows it down.

Treatment Methods for House Flies

Good fly control combines cleaning, keeping flies out, and killing flies that get in. Sprays alone do not work well. You must also get rid of what attracts flies in the first place.

Sanitation and Source Removal

The best way to control house flies is to remove their breeding sites. Key steps include:

• Garbage: Keep trash in sealed cans and take it out often. Clean your trash cans to remove smells that draw flies.
• Pet waste: Pick up pet waste in the yard right away. Keep litter boxes clean.
• Compost: Turn compost piles often and keep them covered. Do not add meat or dairy, which attract flies.
• Food waste: Clean up spills fast. Store food in sealed containers. Keep your kitchen clean.
• Farms: On farms, handle manure through composting, spreading, or removal.

Keeping Flies Out

Stop flies from getting inside your home:

• Fix or replace torn window and door screens
• Add door sweeps and seals around doors
• Keep doors and windows closed when you can
• Businesses can use air curtains at entrances

Traps and Physical Controls

You can reduce fly numbers without chemicals:

• Fly traps: UV light traps work well indoors. Bait traps help reduce flies near buildings.
• Fly swatters and sticky traps: Simple and work well for a few flies.
• Air flow: Good ventilation makes spaces less appealing to flies.

Chemical Options

When cleaning is not enough, you may need to use insecticides:

• Residual sprays: Applied to surfaces where flies rest. Must follow label directions.
• Baits: Fly baits with attractants and poison can cut fly numbers when placed near activity areas.
• Space sprays: Kill flying adults fast but do not last.

House flies often become resistant to pesticides over time. That is why it helps to rotate products and combine methods for better long-term results.

Biological Control

On farms and in large buildings, natural enemies can help control flies:

• Parasitic wasps: Tiny wasps attack fly pupae and reduce adult fly numbers. You need regular releases to keep them working.
• Predatory insects: Some beetles and other bugs eat fly larvae in manure and compost.

References

• House Fly - University of Florida Featured Creatures
• Musca domestica, House Fly - LSU AgCenter
• House Flies - Penn State Extension
• Filth Flies - Kentucky Pesticide Safety Education
• House Fly Management - University of California IPM