Pollenia rudis

Definition

A species of blow fly in the family Polleniidae, commonly known as the common cluster fly or attic fly. Adults are medium-sized, dull gray flies with golden thoracic hairs that overwinter in aggregations within human structures, particularly attics and wall voids, becoming conspicuous in autumn and early spring. Unlike most calyptrate flies, the larvae develop as parasites of earthworms rather than in carrion or decaying matter.

Etymology

Example

Homeowners often mistake large numbers of P. rudis emerging from wall voids in spring for a blow fly infestation, but the sluggish behavior, golden thoracic pile, and absence of larval development in the structure distinguish this overwintering species from true household pests such as Lucilia or Calliphora.

Synonyms

• common cluster fly
• attic fly
• loft fly

Related Terms

• Polleniidae
• Cluster fly
• Overwintering
• calyptrate
• blow fly
• earthworm parasite

Usage Notes

Distinguished from the Pollenia species complex by subtle morphological characters; field identification often relies on association with overwintering behavior in buildings. The common name "cluster fly" also applies to other Pollenia species, so precise identification requires examination of thoracic chaetotaxy or genitalic structures.