How Long Do Flies Live?

Most house flies live about 15 to 25 days as adults, and a few make it to two months. The whole trip from egg to adult can take as little as a week in warm weather.

That short life is why one stray fly in your Olympia kitchen can turn into dozens before you know it. At Bigfoot Pest Management, we get this question a lot, usually from someone hoping the flies will just die off on their own.

Sometimes they will. Often they won’t, because each fly leaves hundreds of eggs behind. Below, we cover lifespans by fly type, the four life stages, how weather changes the clock, and how to break the cycle in a South Sound home.

How Long Do Flies Live? Lifespans by Fly Type

A fly’s lifespan depends on its species. Adult house flies usually live 2 to 4 weeks, drain flies about 2 weeks, and cluster flies can survive for months while they wait out winter inside your walls.

Here is a quick comparison of the flies Washington homeowners see most.

Fly type	Adult lifespan	Egg to adult	Where it breeds
House fly	15 to 25 days, up to about 2 months	7 to 10 days when warm, up to 2 months when cool	Garbage, pet waste, compost, manure
Fruit fly	Varies widely with temperature	About 8 to 10 days	Overripe produce, drains, recycling bins
Drain (moth) fly	About 2 weeks	1 to 3 weeks	Slime inside drains and sewer lines
Blow fly (bottle fly)	Varies; not well documented	As little as 7 days	Garbage, dead animals, meat scraps
Cluster fly	Months for adults that overwinter	Several weeks	Outdoors, inside earthworms in lawns

Keep two numbers in mind when you read any fly lifespan claim. “Adult lifespan” means the time a fly spends buzzing around. “Life cycle” means the full trip from egg to adult.

Mixing them up is why you see such different answers online.

The Fly Life Cycle: Four Stages From Egg to Adult

Flies go through complete metamorphosis, which means four stages: egg, larva, pupa, and adult. For a house fly, the egg and larval stages are where most of the time goes, and warm weather speeds every stage up.

According to the University of Florida’s house fly profile, here is how each stage plays out.

Stage 1: Eggs (8 to 20 hours)

A female house fly lays her eggs in batches of about 75 to 150, right on moist, rotting material. The eggs are white and only about 1 millimeter long, and they hatch fast, usually within a day.

Stage 2: Larvae, or Maggots (4 to 30 days)

The larvae are the maggots you may spot in a garbage can lid. They eat and grow, molting as they go. In ideal warm conditions, this stage lasts 4 to 13 days. In cooler weather around 53 to 63°F, it can stretch to 14 to 30 days.

Yes, maggots turn into flies. This is the stage to target, because maggots can’t leave the spot where they hatched.

Stage 3: Pupae (2 to 27 days)

Mature larvae crawl to a drier spot and form a hard brown case called a puparium. Inside, the body rebuilds into an adult. In hot weather, this takes 2 to 6 days. Near 57°F, it can take 17 to 27 days.

Stage 4: Adults (2 to 4 weeks, sometimes longer)

The adult fly pushes out of its case, dries its wings, and starts looking for food. Females can begin laying eggs within a few days. They keep laying for the rest of their lives, which is the real problem.

How Temperature Changes a Fly’s Lifespan

Heat makes flies grow up faster and breed more, while cool weather slows everything down. A house fly can go from egg to adult in about a week at summer temperatures, but the same trip can take two months when it’s chilly.

That matters here in western Washington. Our mild, cool weather means house flies build up more slowly than they do in hot states. Then a warm stretch in July or August hits, and populations jump.

In temperate areas, house flies can produce 10 to 12 generations in a single year. Flies don’t die off completely in winter, either. They ride it out as larvae or pupae in sheltered spots like compost piles and barns, then finish growing when spring warms things up.

How Long Do Flies Live Indoors?

A single house fly trapped inside with no food or water usually dies within 2 to 3 days. With access to food, crumbs, and a little moisture, an indoor fly can live its full 2 to 4 weeks.

The bigger question is whether it has somewhere to lay eggs.

If you keep seeing flies indoors for more than a week or two, something inside or right outside is feeding the next generation.

Common sources include:

• A kitchen trash can or recycling bin with residue in the bottom
• Pet food bowls, litter boxes, or pet waste in the yard
• A forgotten bag of potatoes or onions in the pantry
• Slimy buildup in sink, shower or floor drains
• Compost or yard waste stored near a door

Fruit flies, drain flies, and fungus gnats are the usual suspects when the flies are tiny. Our guide on getting rid of fruit flies fast walks through traps and cleaning steps that work.

Why One Fly Turns Into Many

A single female house fly can lay up to 500 eggs over her short life. With a new generation possible every week or two in warm weather, a couple of flies in June can mean a full infestation by August. That’s why waiting for flies to die of old age rarely works. The adults do die, but their offspring are already on the way.

Lifespans across household pests vary a lot. A fly’s life is measured in days and weeks, while larger pests like squirrels live for years (here’s a look at how long squirrels live). Short-lived pests make up for it with numbers.

Flies win because they reproduce fast, not because they live long.

What Happens to Flies in Washington’s Fall and Winter?

Most outdoor flies slow down and die off as fall turns cold, but their eggs, larvae, and pupae survive to restart the cycle in spring. The fly you notice indoors in October or November is often a different kind: the cluster fly.

Cluster flies look like slightly larger, slower house flies with golden hairs on their backs.

Their larvae live as parasites inside earthworms, so lawns west of the Cascades suit them well. In early fall, adults gather on sunny south and west walls, then crawl through small gaps into attics and wall voids for the winter.

According to Washington State University’s cluster fly fact sheet, they don’t breed indoors. On warm winter and spring days, they wander out and bump around windows, often in rooms you rarely use.

Because they spend the winter resting, cluster flies outlive house flies by a wide margin. Adults that move in during September can still be around in April.

Killing the ones at the window won’t stop next year’s group, since the problem is how they’re getting in.

How to Break the Fly Life Cycle at Home

The fastest way to shorten a fly problem is to take away the places they lay eggs. Adults only live a few weeks, so if no new generation hatches, the problem fades on its own. Work through these steps:

1. Empty and rinse trash cans weekly. Wash the bottom and lid, where maggots hide.
2. Seal food and compost. Use tight lids and keep compost bins away from doors.
3. Pick up pet waste daily. In the yard, this is a top house fly breeding site.
4. Clean drains. Scrub the pipe walls with a brush, then flush with hot water.
5. Check produce. Toss anything soft or leaking, and store fruit in the fridge.
6. Fix screens and gaps. Repair torn screens and caulk gaps around windows, doors, and utility lines. If a screen needs replacing, start by measuring your window screens correctly.
7. Seal up before September. WSU recommends sealing gaps around siding and window frames and screening attic and crawlspace vents before cluster flies look for winter shelter.

Sticky traps and fly swatters help with the adults you already have. They won’t fix the source, so pair them with the cleanup steps above.

Related Questions to Explore

When to Call a Professional

For most house flies and fruit flies, you don’t need an exterminator. Cleaning out the breeding site is the real fix, and a quarterly spray won’t stop a fly hatching from a dirty trash can.

Elliott Hahn started Bigfoot Pest Management in 2021 with one simple rule: don’t sell people something they don’t need. Flies are a good example.

There are a few times when a fly problem points to something bigger:

• Big, shiny blow flies or maggots near a wall, ceiling, or vent, especially with a bad smell. This often means a rodent died inside the wall or attic. Our rodent control service can find how it got in and stop the next one.
• Slow, sluggish flies at the windows every fall and spring. That’s a cluster fly entry problem. Our exclusion repairs seal the gaps they use to get into your attic and walls.
• Flies plus ants, spiders, or mice. When several pests show up together, a year-round pest prevention plan protects the whole house, not just one room.

We serve Olympia, Lacey, Tumwater, Yelm, and nearby South Sound communities, and Elliott still handles new-customer inspections himself.

Conclusion

Flies don’t live long, but they make up for it with speed and numbers. Here are the key takeaways:

• House flies live about 15 to 25 days as adults, and the full cycle can take just a week in warm weather.
• One female can lay up to 500 eggs, so removing breeding sites matters more than killing adults.
• Fall flies in western Washington are often cluster flies, and sealing gaps is the long-term fix.

If flies are pointing to rodents or a gap in your home’s exterior, contact Bigfoot Pest Management for an honest inspection.