Cluster Flies in the Home
Author(s) Phillip J. Pellitteri
Cluster flies are black, sluggish, bumbling flies that invade homes, office buildings, hospitals, and other shelters every fall in search of a place to overwinter. They enter through cracks and holes in buildings and collect in attics and wall voids. When their resting place warms up, cluster flies resume activity and can be seen crawling on walls or flying around windows or other light sources. Active flies often die within 1–2 days, but if large numbers of flies have invaded a building they will be a major nuisance from fall through early spring (2 pages).