Insect

Cluster Flies

Cluster flies lay eggs in damp soil, hatching in a week. Larvae parasitise earthworms and pupate in the soil, with adults emerging seasonally—typically in late autumn in temperate regions. They are most commonly found clustering in window edging or roof spaces. This species is globally distributed, with behaviour and lifecycle varying by climate.

Facts

Name: Cluster Flies, Pollenia rudis
Life cycle: Complete metamorphosis
Egg: Laid in damp soil or rotting vegetation. Hatch within 1 week.
Larvae: Seek out earthworms to parasitise shortly after hatching. Development within the host takes several weeks.
Pupae: Migrate out of the deceased worm and pupate in the soil.
Adult: Emergence is environmentally triggered. In temperate climates, two generations per year are typical. Adults overwinter in buildings, sheltering in cracks and crevices. In warmer regions, activity may persist year-round.
Description:
Adults are 6 mm long with a black thorax covered in golden hairs. They often appear in large numbers after cold weather and exhibit slow, sluggish flight.
Habitat:
Larvae are subterranean and parasitic, making them difficult to monitor. Adults spend most of the year outdoors and enter buildings in cooler seasons to overwinter in elevated, undisturbed spaces.

Signs of infestation

Large numbers of adults cluster into cracks and crevices in buildings.
Most commonly found in window edging, roof spaces, and wall cavities.
Activity may spike during warm spells in winter.

References

The British Pest Management Manual. Section 5, pg 151.
Lab notes, Tarakan International.

Cluster Flies

Facts

Signs of infestation

Products

Capabilities