CLUSTER FLIES

Cluster flies are similar in size to a house fly. However, they do not breed inside buildings, and instead lay their eggs outside in the soil in the springtime.

They enter buildings to winter over when the temperature begins to drop in the fall, and typically spend the winter dormant in attics and wall spaces. Once the temperature begins to rise again, they can be spotted inside, usually around sun-warmed windows.

Typically, infestations are treated preventively in the fall, before the flies enter the building to winter over. This treatment is exterior, applied to the building's fascia, soffits and exterior walls. However, if a spring treatment is required, that treatment will be internal, and involves fogging the attic spaces in which cluster flies winter over, and treating the area around internal window frames.