Cluster Flies

photo of a cluster flyCluster flies (Pollenia rudis) closely resemble house flies, but they are usually slightly larger and have yellowish hairs on the thorax. There may be four or more generations of cluster flies per season. They do not bite people or animals, and aren’t attracted to garbage. They are, however, parasites of earthworms, and are thus a good indication of a healthy earthworm population nearby. Earthworm populations are largely related to changes in soil moisture, with high population levels coinciding with high moisture content. The more abundant earthworms are, the more likely it is that cluster flies will abound. But when the flies manage to find their way indoors each year in search of warmer temperatures, they can quickly become a nuisance. The fact sheets listed below detail some of the steps people can take to prevent these flies from finding their way indoors.



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