Cluster flies

Identification

  • Colour Dark grey
  • Size From 8 mm to 10 mm long
  • Description Have golden or yellowish hairs on their thorax, while their abdomen features a black and silver checked pattern. Their wings overlap across the abdomen when at rest.
  • Notes Cluster flies strongly resemble house flies, but are larger, darker, and slower.

General Facts

Why do I have cluster flies?

Cluster flies enter homes in the late summer months and the early fall, looking for somewhere to hibernate as the temperatures drop and winter approaches. West and south facing buildings, with large, open lawns, exposed to more sunlight, are especially attractive to cluster flies.

The pests find their way in through openings in the wall, like cracks and crevices near window and door frames, open and unscreened windows, and unscreened vents that provide access into the building.

Once inside, cluster flies then gather together in isolated and protected locations, such as attics and wall voids, to hibernate for the winter.

How worried should I be about cluster flies?

Cluster flies do not pose a danger to humans and do not breed in the homes they invade, but they are widely regarded as a nuisance, especially as they usually hibernate en masse. When they collectively emerge in the spring, it produces swarms that gather around windows.

As well, indoor warmth and unseasonably warm weather can interrupt hibernation, prompting the mass of cluster flies hidden away to suddenly become active again. Homeowners often see the emerging insects flying toward windows and other sources of light on warmer winter days.

As well, the excrement of hibernating cluster flies can stain curtains and walls. Cluster flies that die during hibernation can attract larder beetles, which use the fly carcass as a food source and then remain in the home. To stop an infestation, get help from a professional pest control service.

How can I prevent cluster flies invading?

Vacuum up any cluster flies you see, Use insect light traps to capture them, Seal cracks and crevices in outer walls

Other pests related to Cluster flies

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