Cluster Flies over common nuisance overwintering pests that invade home and businesses in the fall when temperatures cool off in pursuit of a warm and safe place to hibernate over the winter. They favour attics and wall cavitiies. On unusually warm winter days they often awaken thinking it is spring and loudly swarm windows and lights trying to get outside, catching homeowners and business owners by surprise.

A cluster fly is slightly bigger than a house fly with a dark grey-checkered abdomen and golden coloured hairs on their thorax. They are sluggish in flight and therefore easy to swat. They often appear to have no sense of direction, and may even look dead.

They do not feed or  breed inside buildings, and instead lay their eggs outside in the soil in the springtime. Cluster flies are not related to livestock production, nor do they develop in manure or garbage. They are not a sign of unsanitary conditions (like fruit flies) nor do they bite. They are often more a pest to those living in the country or in rural areas.

Getting rid of cluster flies is best achieved through prevention. This includes pest proofing in the spring and fall, and hiring a licensed pest control professional to treat the perimeter of your home and building with a residual spray. In some cases cluster flies will be an ongoing issue and can never be 100% eliminated. They can be controlled and managed by taking the same preventative actions.