Cluster flies are 3/8” long, and a non-metallic grey colour with golden hairs behind the head and base of the wings.
They reproduce in the spring with females laying their eggs in the soil. Larvae develop in the bodies of earthworms. Development from egg to adult takes approximately 27-39 days.
Adults will hide in cracks and crevasses, wall voids, and attics of various structures during the winter. In the spring, they emerge around the windows and lights trying to exit the structure.