What are Cluster Flies?

Cluster flies are a type of fly that are known for their tendency to cluster together in large groups, particularly in the fall and winter months. They are also sometimes called attic flies, because they are known to seek shelter in attics and other warm, protected areas during the winter.
Here are some key characteristics of cluster flies:

1. Appearance: Cluster flies are slightly larger than the common house fly, typically measuring around 8-10 mm in length. They have a dark gray to black coloring with golden hairs on their thorax.
   
2. Habitat: Cluster flies are native to North America and are found throughout the continent. They are often found in rural areas, but can also be found in suburban and urban environments. They are attracted to warm, sunny areas and often seek shelter in buildings, especially during the fall and winter months.
   
3. Behavior: Cluster flies are not harmful to humans or pets and do not bite or sting. They are mostly a nuisance pest, as their large numbers and tendency to cluster together can be unsightly and can produce a foul odor. They typically emerge from their overwintering sites in the spring and may be seen flying around windows and lights.
   
4. Life cycle: Cluster flies lay their eggs in soil, where the larvae feed on earthworms. The adults emerge in the late summer or early fall and seek shelter for the winter. They may enter homes through small cracks and gaps in walls, roofs, and foundations.
   
5. Control: The best way to prevent cluster fly infestations is to seal up any cracks or gaps in your home's exterior and to ensure that all screens on doors and windows are in good repair. Insecticide sprays can also be effective in controlling adult flies.