Quick answer
A house fly (Musca domestica) is a gray, non-biting fly under 3/8 inch long, marked by four dark stripes on its back, that breeds in garbage, manure and other moist, rotting matter and can carry germs from that waste onto food.
It is the most familiar of the “filth flies.” Under summer conditions it can go from egg to adult in about 7 days, so the fix is almost always removing what it breeds in.
Quick facts
The key facts about House Fly, with sources:
Key takeaways
- House flies breed in garbage, pet waste, manure and rotting produce, not in clean homes.
- They go from egg to adult in about a week in summer, so numbers can jump quickly.
- They do not bite, but they carry germs from waste onto food and counters.
- Flies indoors almost always came from outside, so screens and sealed gaps are the first defense.
- Sprays are a last resort; many house fly populations resist common insecticides.
What a house fly is and how to recognize one
The house fly is a medium-sized gray fly that follows people and animals everywhere. UC IPM describes it as under 3/8 inch long, with four dark stripes down its back 1.
Its sponging mouthparts cannot bite, so it eats solid food by first wetting it with saliva and can bring up liquid onto food to help 1.
It belongs to a group called filth flies: flies that breed in waste. NPIC lists the house fly, little house fly, face fly, stable fly, blow flies, bottle flies and fruit flies among the common nuisance species 3.
House flies are most common in the hot summer months 1. Where winters are mild they can breed all year, with many generations 4.
A fly that bites is not a house fly
The stable fly looks very similar but has a stiff, pointed mouthpart and bites, usually around the ankles 5. If a “house fly” is biting you, it is likely a stable fly.
How a house fly develops
House flies go through complete metamorphosis, and the timings below come from UC IPM and Texas A&M.
- Eggs are laid in batches of about 100 to 150 in warm, moist organic matter 1 and hatch within a day 5.
- Larvae, or maggots, are cream-colored and feed for about a week through three stages, the young ones burrowing away from light 15.
- Pupae form inside a hard shell called a puparium after older larvae crawl to drier, cooler spots to pupate 1.
- Adults emerge after 4 to 6 days, can mate within a day and live up to about 25 days 56.
- Eggs100–150 per batch; hatch within a day
- MaggotsThree stages over about a week
- PupaInside a puparium; 4–6 days
- AdultLives up to about 25 days
- Back to step 1
Breaking the cycle at the maggot stage, by removing what they eat, is the most effective control. Source: [1] [5]
UC IPM puts egg to adult at as little as 7 days in summer 1, and Texas A&M says about 8 days under ideal conditions, with up to 12 generations each summer 5.
House fly look-alikes found in and around homes
| Fly | Looks like | Breeds in |
|---|---|---|
| House fly | Gray, four dark stripes, under 3/8 in 1 | Garbage, manure, grass clippings, rotting produce 1 |
| Little house fly | About 2/3 the size; no stripes 2 | Poultry manure, fermenting grass, compost 2 |
| Stable fly | Similar, but with a biting mouthpart 5 | Manure and wet rotting plant matter 2 |
| Blow fly / bottle fly | Larger, metallic blue, green or black 4 | Carrion, pet waste, a dead animal in a wall 4 |
| Cluster fly | Dark gray with golden hairs 4 | Earthworms in lawn soil; overwinters in walls 4 |
Worked example: tracing a summer fly problem
Example: flies build up around a home in July, and each step of reading the clues follows UC IPM, NPIC or Colorado State guidance.
| Clue | Likely cause | Fix |
|---|---|---|
| Many flies near the side yard | Uncovered trash cans or bags left out 3 | Tight lids; trash out once or twice a week 3 |
| Maggots in the bottom of a bin | Breeding inside the can 3 | Wash cans regularly with soap and water 2 |
| Flies around the dog run | Damp pet droppings breed maggots 3 | Bag and remove droppings at least weekly 1 |
| Flies at the compost pile | Fresh grass clippings and food waste 1 | Cover and manage the pile; keep it away from doors |
| Flies indoors near the kitchen | Entry through torn screens or open doors 1 | Repair screens; keep doors closed 3 |
In summer, Colorado State notes trash may need removing every 4 to 5 days 4, since a full cycle can finish in about a week.
Where you will see house flies and their signs
- Around trash, dumpsters, compost and pet areas 3.
- On light walls and ceilings, where they leave small dark spots of droppings and regurgitated fluid 1.
- Near livestock: barns, poultry houses and feedlots are major breeding sites 5.
- In restaurants and food businesses, where health inspections check for flies.
- On a service quote: a recurring pest control plan may include fly lights, bait stations near trash areas or exterior resting-surface treatment.
What works best against house flies
Sanitation and screens do most of the work. UC IPM says flies inside a building almost always came from outside, so sealing cracks and fitting screens is the first line of defense 1. Removing outdoor waste at least once a week takes away the places they breed 1.
For a few flies indoors, a fly swatter or sticky ribbon works. UV light traps can help indoors when they do not compete with sunlight 1; our page on how insect light traps work covers placement. Outdoors, baited cone traps work if they are not competing with nearby garbage 1.
Limits of fly control
- Sticky fly paper handles only a few flies in small spaces, not heavy infestations 1.
- Baits alone will not control flies that can reach garbage 1.
- House flies resist many registered insecticides 1; NPIC adds sprays give only temporary relief 3.
- Flies can travel far; a 2023 review cites reported flights of 7 to 32 km, or about 4 to 20 miles 6.
- Bug zappers near food can scatter insect body parts over several feet 1.
What drives the cost of fly control
For homes, most fly control costs little more than better trash handling and screen repair. Paid work grows with the number of breeding sites, such as animal pens or a restaurant dumpster, and with add-ons like fly lights or exterior treatments.
Commercial kitchens and farms pay more because waste volume is high and inspections demand results. See the cost guide for how service plans are priced.
How a professional fly program works
A good program follows integrated pest management, with chemicals last.
- Identify the fly: NPIC says different flies need different controls 3.
- Find breeding sites: trash, drains, pet waste, compost, dead animals 34.
- Remove or fix them: lids, cleaning, waste pickup, dumpster at least 50 feet from doors 3.
- Exclude: screens, door closers, sealed gaps 1.
- Trap and monitor with light traps indoors and cone traps away from buildings 1.
- Treat only if needed: a licensed company may treat outdoor resting surfaces 1.
Routine habits that keep flies down
- Bag kitchen waste, use cans with tight lids and rinse bottles and containers before they go in the recycling bin 13.
- Pick up pet droppings at least weekly 1.
- Keep doors closed and screens repaired, and fix leaky drains and garbage disposals that stay wet and smelly 3.
- Trash cans lidded and washed
- Pet waste removed
- Screens intact
- Compost covered
- Drains not leaking
Health risks and when to call
House flies move from waste to food, and UC IPM says they are known to carry bacteria and viruses that cause diarrhea, cholera, food poisoning, dysentery and eye infections 1.
A 2023 research review found more than 200 types of disease-causing bacteria on adult flies from cities and farms, and E. coli O157:H7 survived on a fly’s body for up to 13 days 6.
Call a professional if flies stay high after you fix trash and screens, if you see maggots coming from a wall (a dead animal may be inside), or if you run a food business.
Keep sprays away from food
Do not spray insecticides on food areas, and follow the label exactly. Never use a bug zapper near food preparation 1. Call Poison Help at 1-800-222-1222 if anyone swallows fly bait or spray.
Pesticide and health-code rules for fly control
Every fly bait, spray or strip sold in the U.S. is a pesticide registered by the EPA, and its label is the law. NPIC suggests trying lower-toxicity products first and following all label directions 3. Our pesticide safety page explains how to read and follow a label.
Food businesses also answer to state and local health codes, which generally require keeping flies out of food areas. Companies applying products for pay must hold a state license; see pest control licensing.
House fly vs fruit fly vs mosquito
House fly myths
- Myth House flies bite.
- Reality Their sponging mouthparts cannot bite; biting look-alikes are stable flies 15.
- Myth A spray will fix it.
- Reality Sprays give temporary relief; removing breeding sites is the lasting fix 3.
- Myth Flies are breeding inside my clean kitchen.
- Reality Flies indoors almost always came from outside 1.
- Myth Bug zappers are good near the grill.
- Reality UC IPM warns against zappers near food because body parts scatter 1.
- Myth Fall flies on upper windows are house flies.
- Reality They are often cluster flies coming out of wall voids 4.
How climate and setting change fly pressure
House flies peak in hot summer months 1, and in areas with mild winters they keep breeding year-round 4. Rural homes near barns, poultry houses or feedlots face the heaviest pressure, since those are major breeding sites 5.
In colder regions, the flies seen on upper-floor windows in fall and winter are more often cluster flies, which enter on south and west walls in late summer 4. Check the seasonal calendar for local timing.
- 7 daysEgg to adult in summerUC IPM
- 100–150Eggs per batch, several batchesUC IPM
- 200+Disease-causing bacterial types found on fliesNayduch et al. 2023
When it matters to you, and what to do next
For a few flies indoors, swat them, fix the screens and check the trash. With many flies outdoors, find the breeding source within about 100 feet and remove it. Maggots coming from a wall, or flies that persist after cleanup, call for a licensed company that can trace the source.
If you run a food business, a scheduled program with monitoring is the norm. Before you sign, our guide to choosing a company lists the questions worth asking.
Quick decision guide
For a few flies, fix screens and trash. For swarms outside, find and remove the breeding site. For maggots from a wall, or flies that last after cleanup, call a licensed pro.
Questions about House Fly
Where do house flies come from?
House flies come from moist, rotting material outdoors, such as garbage, manure, pet waste, grass clippings and spoiled produce. Females lay eggs there, and maggots develop in about a week. UC IPM says flies inside a building almost always came from outside through open doors, gaps or torn screens.
How long do house flies live?
Adult house flies live up to about 25 days, according to Texas A&M AgriLife, and some can survive winter in sheltered places. The full trip from egg to adult can take as little as 7 days in summer. Because they breed so fast, removing breeding sites matters more than killing adults.
Do house flies bite?
No, house flies cannot bite. UC IPM explains they have sponging mouthparts and eat by wetting food with saliva. If a fly that looks like a house fly is biting you, it is likely a stable fly, which has a stiff, pointed mouthpart and often bites around the ankles.
Are house flies dangerous?
Yes, mainly by spreading germs. UC IPM says they carry bacteria and viruses linked to diarrhea, food poisoning, dysentery and eye infections, picked up from waste and left on food. A 2023 research review found more than 200 types of disease-causing bacteria on wild flies, so keeping them off food is the main protection.
Why are there so many flies in my house suddenly?
A sudden swarm usually means a nearby breeding source, such as garbage, pet waste or a dead animal in a wall or attic. Blow flies in large numbers can signal a dead mouse or squirrel, per Colorado State. In fall, flies on upper windows are often cluster flies coming out of wall voids.
What is the fastest way to get rid of house flies?
For flies already inside, a swatter, sticky ribbon or indoor UV light trap works quickly. For lasting control, remove the breeding source: cover and clean trash cans, pick up pet waste and fix screens. UC IPM says insecticides should be a last resort, and many house fly populations resist them.
Do fly traps work?
Yes, when used in the right place. UC IPM says sticky ribbons handle a few flies in small spaces, UV traps work indoors away from sunlight, and baited cone traps work outdoors if not competing with garbage.
Place smelly cone traps well away from doors, and treat every trap as support for sanitation rather than a replacement.
How do I keep flies away from my trash cans?
Use cans with tight lids, bag all food waste, and set trash out at least once a week. In summer, Colorado State suggests removal every 4 to 5 days. Wash cans regularly with soap and water, and rinse food containers before recycling. NPIC advises keeping dumpsters at least 50 feet from doors and windows.
Sources
- UC Statewide IPM Program, Pest Notes: Flies (Publication 7457, April 2015), retrieved .
- UC Statewide IPM Program, Flies (Home and Landscape), retrieved .
- National Pesticide Information Center, Flies, retrieved .
- Colorado State University Extension, Flies in the Home, retrieved .
- Texas A&M AgriLife, Field Guide to Common Texas Insects: House Fly, retrieved .
- Nayduch et al., House Flies Are Underappreciated Yet Important Reservoirs and Vectors of Microbial Threats, Microorganisms (2023), retrieved .
Expert review
Written by the HyrePest Research team. Not yet reviewed by an outside expert. We say so rather than imply a review that has not happened; see our editorial policy.
How the numbers were checked: Identification, life cycle, disease agents and management follow UC IPM Pest Notes 7457 and its web page; development timings and adult life follow Texas A&M AgriLife; control steps follow NPIC; look-alike flies follow Colorado State Extension; bacterial and flight figures are from a 2023 peer-reviewed review.
Texas A&M’s field guide calls house flies medically harmless; we follow UC IPM and the peer-reviewed review on germ carriage.
Suggest a correction. We fix errors and say what changed.