Attic-flies
Guides
Pollenia
cluster flies, attic flies
Pollenia is a genus of blow flies commonly known as cluster flies or attic flies. Unlike typical carrion-feeding blow flies, these insects are parasitoids or predators of earthworms and other invertebrates. Adults are medium-sized flies that frequently enter buildings in autumn to overwinter in sheltered locations, becoming active on warm winter days and emerging in spring. The genus contains approximately six species in North America, with Pollenia rudis and P. pediculata being most common. Species identification requires microscopic examination of setae patterns.