How Long Do Flies Live Indoors? Fly Lifespan, Warning Signs & When to Call a Pro

Homeowners will be pleased to learn that — when deprived of food and water — flies will only last inside 2 – 3 days indoors. One could argue, however, that any second spent sharing your home with a fly is one second too long.

To avoid playing host to unwanted house flies, homeowners must first understand what makes their space such a prime breeding ground for these pesky critters. In this blog, we’ll answer:

• Where do flies lay their eggs?
• How long can flies live indoors — and how does that compare to outdoors?
• Will house flies go away on their own?
• When should you contact a fly control professional?

Where Do Flies Lay Their Eggs?

The common house fly is a small, flying insect with a dull gray body approximately ¼ inch in length. They usually lay their eggs on moist, decaying, organic materials, including:

• Animal feces
• Trash
• Grass clippings

University of New Hampshire Extension entomologists note that a single female typically lays 75 to 150 eggs per cluster, and can deposit anywhere from 350 to 900 eggs in her lifetime. White, legless maggots hatch from the eggs, growing to about ½ inch in size before entering their pupal stage. A dark brown cocoon called the puparium is formed, and later, the flies emerge as adults that can search for egg-laying sites to perpetuate the cycle. In warm conditions that entire cycle can take as little as one to two weeks, which is how a single overlooked breeding site can produce six to eight generations in a single year.

How Long Do Flies Live Indoors — and How Does That Compare to Outdoors?

The exact life cycle of a fly depends on the species, and so does its lifespan as an adult. The general life expectancy for a house fly is 15 – 25 days when kept in optimal conditions — flies thrive in moist, warm environments with lots of food and water sources, which is why proper prevention and pest control techniques are critical for preventing an infestation.

Indoors, a fly will only live a few days.  A typical indoor environment lacks food resources.  Outdoors, that same fly typically survives only about 15 to 25 days. Predators, wind, rain, and swinging temperatures all take a toll in a way that a heated, food-stocked home simply doesn’t. That’s the real reason an indoor fly problem can outlast an outdoor one: a fly that makes it inside has less working against it, not more incentive to leave.

When deprived of food and water altogether, the picture changes fast. Flies can only survive for 2 – 3 days without food or water, regardless of whether they’re indoors or out.

Will House Flies Go Away From Inside My House?

Sometimes — but not reliably enough to count on. A house fly can die on its own from stress as it tries to escape a home, but as the lifespan numbers above show, it doesn’t have much reason to leave a warm space with steady food and water, and it may live long enough to lay several batches of eggs before it does. The key to getting rid of flies quickly is making sure your home isn’t attractive to them in the first place. To help get rid of unwanted house flies, homeowners should:

• Remove any standing water, such as pet bowls or dirty dishes
• Utilize tight fitting screens on windows and doors
• Clean up trash and secure bins with a tight lid
• Store leftovers inside the refrigerator
• Keep toilet lids closed when not in use

When to Contact a Fly Control Professional

While house flies will go away on their own some of the time, there are occasions when an infestation deserves professional attention. Be on the lookout for the following signs that indicate it’s time to contact a fly control professional:

• Dark Clusters: If you notice small, dark clusters of spots inside light fixtures or high up on walls and ceilings, this could be a sign of a house fly breeding ground. A joint University of Arizona and Oregon State University Extension IPM guide notes that these specks are fecal matter and regurgitated stomach contents that flies leave on the surfaces where they rest — and that house flies favor resting on ceilings and other vertical surfaces overnight, which is why the marks tend to show up there first.
• Fly Sightings: Large numbers of flies buzzing around your property should be monitored closely — especially when observed near garbage areas.
• Maggot Sightings: Spotting maggots means flies are reproducing in or around your home, which could lead to a serious infestation.

When you need help eliminating flies from your home, GreenHow is here to help. Our team has years of experience removing fly infestations with the most powerful yet eco-friendly materials available. Allow us to flush out the flies in your home once and for all by calling us at (617) 964-4733 to request a free fly inspection today!

Frequently Asked Questions

How long do house flies live indoors? Typically 1 to 3 days in optimal conditions — warm temperatures, and steady access to food and water let them live toward the upper end of that range.

How long do house flies live outdoors? About 15 to 20 days. Predators, weather, and temperature swings shorten their lifespan compared to the stable conditions inside a home.

How long can a fly survive without food or water? Only 2 to 3 days, whether it’s indoors or outdoors.

Will a fly inside my house die on its own? It might, but not on a timeline you can count on. With steady warmth and food, an indoor fly can live long enough to lay several batches of eggs before it dies — which is why sanitation and exclusion matter more than waiting it out.

What do the dark spots on my ceiling or light fixtures mean? They’re fly fecal matter and regurgitated stomach contents left on resting surfaces, and they’re one of the clearest signs of an active house fly population indoors.

Related Fly Posts from GreenHow

• House Flies: Why You Have Them and How to Get Rid of Them for Good — full identification, life cycle, and control guide
• What Attracts Flies to My House? — the smells and conditions that draw house flies and fruit flies indoors
• How to Get Rid of Fruit Flies in Your Home Kitchen — our residential fruit fly guide
• Fruit Flies in Restaurants — the commercial food-service version

Or explore our full pest control services.

Other sources for additional information:

• House Fly Fact Sheet — University of New Hampshire Extension
• Gouge, D.H. (University of Arizona) and Stock, T.W. (Oregon State University). “Flies in the Kitchen.” School & Home Integrated Pest Management (IPM) Newsletter, June/July 2022.