How do I get rid of Cluster Flies?
Scientific Name: Pollenia rudis (Fabricius)
How to Identify them?
Cluster flies are close relatives of blow flies and resemble house flies (3/8 inch) in size, but they have a more robust body structure. They are nonmetallic gray, lack thoracic stripes, and have yellow or golden hairs on their backs, behind their heads, and around the base of their wings. Cluster flies appear narrow when at rest because their wings completely overlap their backs. The larvae are typical spindle-shaped maggots, but people never see them since they develop as parasites in earthworms.
Pest Biology
In the spring, female flies mate and lay their eggs in soil crevices. The eggs hatch within three days, and the larvae burrow into earthworms’ bodies, where they develop. This process takes 27 to 39 days. Typically, cluster flies have four generations per year.
What are their Habits?
Cluster flies become annoying because they overwinter as adults in the attics and wall voids of structures, especially older frame buildings. The species’ common name reflects its habit of gathering in clusters before hibernation. They enter structures to seek shelter from cooling temperatures.
How to remove and prevent them?
No effective control exists for the larval stage of these flies because they develop in earthworms. To control cluster flies, start before they enter buildings in large numbers. The most effective long-term control in structures attractive to overwintering adults is sealing entry points in the walls and roof of the structure.
