Contrary to popular impression, face flies do not breed and multiply in attics and homes, nor do they feed during the winter. In spring, the face flies mate shortly after emergence from winter quarters. Females then fly to pastures and seek horses or cattle. They feed on exudations from eyes and nostrils, and lay their eggs in fresh cow dung. Several generations occur in pastures each summer before the flies again seek protection for the winter.
Some homes are attractive to face flies and vulnerable to their entry year after year.
Thus, accumulations of dead flies in unseen places eventually can be measured by the bucketful or scoop shovel. The carpet beetles lay eggs on the dead flies. Hatching beetle larvae use the flies as food. Upon reaching adulthood, the beetles quickly initiate another generation. Eventually the carpet beetles find their way into the living space of the home, where they may cause extensive damage to carpets, carpet backing, woolens, and other non-synthetic clothing.