• Genus: Pollenia
• Species: rudis
• Wings fold directly over the abdomen when at rest (often overlapping)
• Thorax has a dark gray to olive sheen, covered in golden hairs (absence of thoracic stripes)
• Abdomen features a distinct checkered or mottled pattern
• Slower, buzzing flight

Identification:

CFs are relatively large (~10 mm) and superficially resemble HFs, but can be distinguished by a broader, darker body, golden thoracic hairs, and a dull checkered abdomen. CFs are not filth-associated and do not reproduce in and around organic waste. Adults are often lethargic indoors, especially during cool temperatures, and may accumulate in attics, wall voids, and other structural spaces, especially near windows during fall and winter.

Habitat & behavior:

• Development does not occur in garbage, feces, or decaying organic matter.
• Develops within moist, well-drained soils, where larvae parasitize earthworms (especially Grey worm, Aporrectodea caliginosa).
• Grey worm is widespread in temperate soils.
• Grey worm is a preferred CF host because of shallow burrowing behavior, which increases its exposure to CF eggs placed within the soil.
• CF adults feed upon nectar and plant sap.
• CF adults seek overwintering refuge in and around structures such as attics, wall voids, and other cryptic spaces during late summer and fall.
• Frequently observed indoors on warm winter days interacting with windows or light sources.
• Exhibits sluggish, noisy flight.
• Adults display thigmotaxis (preference for tight contact with surfaces) and cluster in protected crevices.
• Aggregates in upper interior spaces, often annually returning to the same structural feature via pheromone or site fidelity cues

Public health significance:

CF is not understood to be a mechanical disease vector. Large indoor accumulations of dead, desiccated CFs can fragment over time, creating airborne particulates that may exacerbate asthma and allergies in sensitive individuals. Additionally, decomposing CF corpses may serve as a secondary attractant and nutrient source for Dermestid beetles (Coleoptera: Dermestidae), Cockroaches (Blattodea), and even commensal rodents. This initiates a successional chain of opportunistic pest infestations within structural voids.

Lifecycle (Holometabolous or “whole change”)

• Reproduction: Oviparous or places eggs in soil
• Development: Larvae are obligate parasites of Earthworms
• Pupae develop in soil
• Adults emerge in late summer
• Bivoltine or two generations per year (depending upon climate)

Quick facts:

Environmental role:

CF larvae are natural parasitoids of Earthworms, contributing to soil ecology by regulating annelid populations. While considered a nuisance indoors, CFs pose no significant risk to public health and do not reproduce within structures.