Cluster Flies
Cluster flies overwinter in attics and wall voids, emerging sluggishly on warm winter days.
Background & Behavior
(Pollenia rudis) Also known as attic flies, cluster flies resemble large houseflies but move more sluggishly. They enter homes in autumn to overwinter in attics, wall voids, and window frames. While they don’t breed indoors or spread disease, they can appear in large numbers on warm winter days. Dead cluster flies may attract other pests like beetles or spiders.
DIY Approaches
- Install fine-mesh screens over attic vents and soffits.
- Vacuum window frames and ceiling corners where flies rest.
- Seal cracks around chimneys and siding with exterior-grade caulk.
- Darken attic spaces to make them less attractive for overwintering.
- Set up UV light traps in unused rooms to capture emerging adults.
Professional Services
- Arrange attic fogging or dusting services before overwintering begins.
- Request full home exclusion to close gaps around rooflines and vents.
- Have pest pros maintain exterior residual treatments in early autumn.
- Schedule follow-up inspections in late winter to monitor activity.
- Engage insulation contractors to replace contaminated insulation with treated materials.
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