Cluster Flies

With the warm weather you may start to notice cluster flies.

Cluster FliesWhat are they?

Cluster flies are slightly larger than the house fly and appear to fly more sluggishly. They can be recognised by:

  • distinct lines or stripes behind the head
  • short golden-coloured hairs on the thorax
  • irregular light and dark gray areas on the abdomen.

They are not known to be harmful, just a nuisance.

When do they appear?

When the weather starts becoming warmer in the spring they will become active and will be more noticeable. During the summer and early autumn cluster flies are rarely noticed as they are away from buildings (near earthworms!). As the season cools they want to hibernate and seek shelter in nooks and crannies in houses and other buildings. 

Where do they appear?

Cluster flies are usually found in rural or semi-rural areas and can be found in loft spaces or sometimes in unused rooms, or around window seals. They are usually seen in large groups and will often be noticed around sunny windows.

How do I control them?

You can try and control the clusters by using:

  • Fly sprays (always read the instructions)
  • Fly Swats
  • Sticky papers
  • Vacuum cleaners (to suck up large clusters)
  • UV insectocuters

(NB take care not to install one over food preparation areas and do not install in lofts as they may be a fire hazard)

It’s out of Control!

If the infestation is out of control and you are experiencing new batches 2-4 times a year, we would suggest calling in a pest control company such as:

CMPC  (County Mole & Pest Control)

Icon phone sml 0800 731 3647


It is extremely difficult to prevent cluster flies entering a property. Fly proofing a building is not 100% effective. However, caulking around windows, and sealing obvious entry points can help.

Sometimes a single building in a row of apparently identical buildings will be selected for clustering year after year. This doesn’t mean that this house has poor hygiene standards – it is just random.