Polleniidae
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.
Pollenia rudis
common cluster fly, attic fly, loft fly, buckwheat fly
Pollenia rudis, the common cluster fly, is a medium-sized blow fly in the family Polleniidae. Adults are notable nuisance pests of buildings, overwintering in attics and wall voids in large aggregations during cold months. The species is an obligate parasite of earthworms in its larval stages, with well-documented host specificity to certain lumbricid species. Native to Europe, it has been introduced to North America and New Zealand, where it occurs wherever its earthworm hosts are present.
Pollenia vagabunda
cluster fly
Pollenia vagabunda is a cluster fly in the family Polleniidae, widespread across Europe and introduced to North America, where it was first recorded in 1958. Unlike carrion-associated blow flies, this species has a life cycle tied to earthworms and other hosts rather than decomposition. Adults are known to overwinter in buildings and have been documented on carrion, though not tied to specific decomposition stages. The species has also been recorded in Algeria and shows potential forensic relevance.