Musca autumnalis, commonly known as the “face fly,” is native to Europe, west Asia and east Africa, but they have become well established in the northeast US and Canada. Face flies are well known for their annoying habit of flying into people’s eye-sockets in order to feed on ocular discharge, which can result in pink eye and other medical conditions. In addition to this annoying habit, face flies are also notable for swarming into homes in large numbers during the fall in order to overwinter in well-concealed areas. These flies remain inactive within homes all winter before reemerging once spring arrives. Therefore, homeowners who experience a nuisance face fly swarm in their home during the fall can expect another come spring. Unfortunately, face flies are in the habit of returning to the same homes year after year for overwintering purposes, and they travel long distances in order to do so. Annual infestations are likely to occur in homes located near agricultural areas, as face flies breed on manure.
Adult face flies are between 4 and 6 mm in length, and they resemble house flies. Female face flies are known for laying single eggs one at a time or in batches of 7 to 36. Generally, females produce four or five batches of egg during their lifetime. Adults live for only around ten days, but the last generation during the fall can live for several months. Females prefer to lay their eggs on fresh cow excrement, but they avoid breeding on excrement that is dry or mixed with hay. It is believed that face flies tend to return to the same overwintering sites each year due to their attraction to volatile chemicals left by previous generations of overwintering flies. Face fly hibernation is interrupted by unseasonably warm winter days, especially in the southeastern states, but in the northeast, face flies are likely to overwinter in homes until spring.
Has your home ever been infested with flies that darted toward your face?