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Why are there Flies in my House and Where Do They Come From?

Every spring, it’s the same thing. You have flies sneaking their way into your house, buzzing around your head, and finding something sticky to eat on the counter.

If you happen to live near farmland or even have a compost pile, you know what a fly infestation looks like every spring – it’s like a scene from a bad horror movie! In one afternoon, you could have hundreds of flies hanging onto your patio door screen, trying to get into your house.

Fly Facts

The typical housefly lives between 15 to 25 days. Flies are more active during the day, but they can be a pest at nighttime as well when they’re looking for someplace to sleep.

Indoors, houseflies live on floors, walls, and ceilings. It is also common to see house flies near windows.

Did you ever wonder why they are attracted to windows? If you think they are trying to get outside – you are giving them too much credit! For the most part, flies are attracted to windows for warmth. And, once they get to the window, they simply get confused as they fly around trying to find a food source.

You may have a housefly problem outside because flies will sleep in plants, fence wires, garbage cans, and on the ground.

When you ask, “Where are the flies coming from?” You can look at the temperature and wind current as well. On warm summer days (85°F and higher), flies will catch a cool breeze from your air conditioning unit and come inside. Conversely, on cooler days, houseflies hitch a ride on a warm air current, such as any heat coming from your house.



What Do Houseflies Look Like?

The typical housefly is

  • Dark gray
  • Between 1/8” to 1/4” long
  • Has six legs and antennae
  • Has a small, oval body, and two wings that overlap on their back.

Houseflies are found throughout the U.S. The larvae are maggots—those creamy white-gray rice-like critters that you see wiggling around on an old banana peel in the garbage.


What Do Houseflies Eat?

Houseflies, like their many cousins, eat filthy things—such as garbage, manure, rotting fruit, and dead animals. You can reduce the number of flies that come into your backyard by making sure all dog messes are cleaned up, and your trashcan has a solid lid on it. Flies can transfer bacteria from feces to food.


Why are Flies in my House?

Flies are just trying to survive and, inside your house, flies will land on your food, soda, dog food and many other things to get a tasty meal. Anything sweet will definitely attract flies.

Can houseflies smell? Yes, they do. When flies smell something awful, like a lot of trash lying around, they will assemble in your yard or your home.


Ready to get rid of house flies?

What is the Housefly’s Life Cycle?

Lifecycle of a fly



How Do Houseflies Spread Disease?

Many people ask, “Are houseflies dangerous?”

Yes, actually they are. Houseflies carry over 100 pathogens that they spread when they land on your hamburger or when they lay eggs on your dog’s waste. Plus, these filthy flies constantly defecate—wherever they happen to land, including your kitchen island.

Additionally, houseflies will eat a piece of food or garbage, throw it back up, and then eat it again in liquefied form. When flies go through this eating process on your counter or table, they’re spreading bacteria.

Where do houseflies lay their eggs? In the same places where they eat. Houseflies will lay eggs on garbage, manure (including any dog or cat feces) or dead animals (also known as carrion).

As stated earlier, houseflies carry over 100 diseases, such as salmonella, malaria, and tuberculosis, among many others.

Of course, houseflies don’t only hang out in your home. They will also pester you and your friends when you’re enjoying your backyard. If you have a cookout, you may spend half your time swatting flies away from your grill.

Will houseflies bite you? Nope. But other types of flies will bite, including the horsefly, mosquito (yes, mosquitoes are part of the fly family), and the stable fly. If your home is in a rural area, you may notice more houseflies and other fly species.


Learn More:

How to Get Rid of Mosquitoes in a Yard


Houseflies vs. Cluster Flies

Houseflies and Cluster Flies look similar but, there are some big differences.

Most importantly, Houseflies are disgusting and spread disease by feeding on, among other things, dog poop, garbage, rotting carcasses and an array of other lovely menu items.  When Houseflies land, they poop – and vomit wherever they want!  Think, hamburger, potato salad, picnic…

Cluster Flies can definitely land on something gross, and then land on your food but – that would be like someone that stepped in dog poop – they didn’t try to do it – and Cluster Flies don’t try land on gross stuff to get a meal. Ok, no more gross stuff (for now)!

Here’s the good news – Cluster Flies don’t spread disease.

Cluster Flies feed on much safer organic matter such as sap, honey dew, plant nectar and other mostly harmless things. So, if you see Cluster Flies, in a – you guessed it – cluster (ha!) don’t jump to the conclusion that you have a dead animal in your house (or rotting garbage, etc.). Because that is not what Cluster Flies eat.

How to Know if You Have Houseflies or Cluster Flies?

Cluster Flies absolutely do look similar to Houseflies however, there are three things to look for to properly identify your flies:

  • Cluster Flies are noticeably larger than Houseflies – 8-10 mm in length compared to house flies that are about 6-7 mm long.
  • Cluster Flies are clumsy fliers – it’s like they’re drunk.
  • Cluster Flies do more, ‘clustering’ than Houseflies (seriously – they do).

Where do Cluster Flies Come From?

Cluster Files lay eggs in the soil. Those eggs hatch and eventually morph into adults that look like large Houseflies.  In the adult stage, they fly around as you would expect – looking for light, warmth, food and water.

Do Cluster Flies bite?

No, they don’t bite, sting, pinch, punch or kick.

Do Cluster Flies Cause Damage?

Cluster Flies don’t damage homes. Besides being a nuisance, the main concern is other insects that can infest your home in search of a tasty, dead Cluster Fly, meal. (Preferably, cooked medium or medium rare).

It is best to clean up dead Cluster Flies (or any insects) that you find – even it if is in a remote area like an attic – to prevent other insect populations from exploding.

Why are Cluster Flies in my House?

Cluster Flies get into houses to establish a place to live and, eventually, overwinter. Like their name, they congregate in large numbers – very often in attics. They can get in through any type of small opening. The best way to keep Cluster Flies out of your house is to seal any gaps, cracks or other openings.



How to Keep Bugs Out of a House


Housefly Control Measures

Fortunately, you’re not stuck with having to live with a housefly infestation. Indeed, there are three ways to shoo those flies out of your house and backyard:

  1. Keep a clean house – Remember that phrase, “cleanliness is next to godliness”? Well, that’s the first line of attack to keep houseflies out of your home and backyard.


Here are some cleaning tips:

  1. Change your kitchen trash often
  2. Clean out your kitchen trashcan regularly
  3. Cover all food and drinks
  4. Wipe up any spills and crumbs from the table or countertop
  5. Make sure there are tight lids on outdoor trashcans
  6. Fix any broken seals, vents, or torn screens inside your house
  7. Rinse out all bottles and cans before placing them in your recycling container
  8. Clean up your yard too, including dog waste
  9. Dispose of any food lying around
  10. Scrub your outdoor grill and remove any bits of food that are in the grill


  1. Use biological controls – While you may be squeamish around spiders and wasps, these two critters prey upon houseflies. So, you may want to think twice about wasp control or sweeping that cobweb off the corner of your porch.


You probably have parasitic wasps on your property. Don’t kill them! Most parasitic wasps won’t sting people, but they will eat your houseflies, among other pests.


Don’t forget about the Venus flytrap and other predator plants. These predator plants may not completely solve your housefly problem, but they’ll help you keep flies in check.


  1. Call your local exterminator – If you have an infestation of houseflies and you can’t get rid of them using the above controls, then a pest control company is the next place to turn to for help.


Your local pest control company will keep you and your family safe while getting rid of those filthy flies.


*Warning – Pesticides are poisonous. Read and follow directions and safety precautions on labels. Handle carefully and store in original labeled containers out of the reach of children, pets, and livestock. Dispose of empty containers right away, in a safe manner and place. Do not contaminate forage, streams, or ponds.


Need help protecting your home from flies and other common pests with our Year-Round Pest Control Program? Contact us to find out more.

Need more information about our fly control services within the Allentown and Bethlehem area or the Reading and Wyomissing area?