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Ask the Orkin Man

Where are these giant house flies coming from?

Question: For the past week, we keep getting hordes of giant house flies flying out of our laundry room. We can’t find where they’re coming from or why. They always appear on the fluorescent light fixtures, and every time we kill them all, a few hours later there are more. How do we figure out where these are coming from?

 

ANSWER: What you have seen may be cluster flies. They are sometimes mistaken for the common house fly, but they have a completely different life cycle. These flies are very common inside houses, especially  during the early spring.

The life cycle of the cluster fly (Polenia rudis) begins in the spring when they leave the overwintering sites (attics and wall voids of houses) and lay their eggs in the soil. The larval or maggot stages of this fly attack and eat earthworms. There are several generations of cluster flies during the summer. Each time the female returns to lay eggs in the soil. However, the flies of the last generation (mid to late August) will spend the winter in a protected location, and start the life cycle over again in the following spring.

Cluster flies begin searching for a place to spend the winter during the last month of summer, usually in late August and early September.  They will gather on the sides of houses that are warmed by the afternoon sun. They collect there by the hundreds or thousands. Some of the flies find openings and make their way inside the house. They spend the winter inactive until the temperature goes up.

Control of these flies is not easy. Call your local Orkin Branch office and a highly trained Orkin Pest Specialist will conduct a thorough inspection, assess the extent of the infestation and develop a customized solution backed by science.

Inspect the outside of the house. Make sure attic vents are all screened. Repair window screens and check weather stripping on exterior doors.

Related Questions:
The Orkin Man used the information above to also answer the following questions submitted by Orkin.com users:

Question: Do you have a treatment for house flies?

Question: I have house flies caked on the outside of my house. I have a black tin roof and white siding. Is this normal? If not, is there anything that can be done about them? They are swarming, it sounds and looks awful.

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