Cluster Flies

What do cluster flies look like?

Cluster flies are often mistaken for common house flies due to their similar appearance, but there are some key differences to look out for. For example, cluster flies are generally larger than house flies, measuring between 3/8th to ½ inch in length when fully grown. Their bodies are gray in color and may feature black markings. Additionally, unlike house flies that have a metallic appearance, cluster flies are covered in gold-yellow hairs. Another notable characteristic of house flies is their sluggish movements; they’re not as frantic acting as house flies. 

cluster fly

What do cluster flies eat?

Adult cluster flies feed on flower nectar, plant sap, and other organic matter. They do not feed during the winter months. 

Cluster fly larvae burrow into the soil to feed on earthworms. 

Are cluster flies dangerous?

Cluster flies are mainly considered to be nuisance pests; they don’t bite or sting and do not carry or transmit disease to people or animals.  They do not lay eggs indoors and will not damage property or cause any serious problems. 

Why are cluster flies called cluster flies?

When cluster flies are in their over-wintering sites, they will “cluster” together. Outside they also tend to cluster together in groups, especially on the sunny sides of homes. 

Why do I have cluster flies?

During the fall and spring seasons, it is not uncommon for homeowners in Maine to find cluster flies in their homes. Adult cluster flies search for protected over-wintering sites, such as the cracks and crevices inside houses, sheds, barns, and other man-made structures during the late summer or early fall. When spring arrives and the weather warms, cluster flies leave their over-wintering sites to lay eggs on the soil.

Why am I seeing cluster flies in the middle of winter?

Cluster flies can become a nuisance in the middle of the winter when warmth or light lures them from their over-wintering sites. 

How do cluster flies get inside?

Like other pests, cluster flies enter homes and other structures through cracks, gaps, and openings around doors, windows, cables, wires, and pipes. Really, any opening outside of the dwelling is a potential entry point for these pests. 

How do you get rid of cluster flies? 

If your home has suddenly been taken over by cluster flies, contact Pine State Pest Solutions to find out what steps can be taken to eliminate cluster flies. 

How can I prevent a cluster fly infestation

To prevent a cluster fly infestation, you need to remove access to your home or building.  We recommend the following cluster fly prevention tips:

  • Inspect window and door screens; if there are any holes or tears, be sure to repair or replace them.  
  • Seal gaps, cracks, and openings on the exterior of the structure from the foundation to the roof. 
  • Cover vents with tight fitting mesh.
  • Repair or replace any loose or missing roof shingles or siding.
  • Install a tight-fitting cap over the chimney. 

For help with pests, contact Pine State Pest Solutions

Pine State Pest Solutions proudly provides pest control services in Portland, Augusta, and communities throughout Kennebec, Androscoggin, Sagadahoc, Oxford, Cumberland, and York counties.


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