Fannia canicularis, or the “little house fly,” as the species is more commonly known, is a common household pest throughout the US. Males of this species are frequently found within houses, while females generally remain outdoors. Unlike common house flies, which are generally concentrated within particular areas within infested homes, little house flies are often found infesting multiple rooms throughout households. According to one study that investigated many fly-infested homes, an average of 66 percent of all house flies inhabiting homes were found in the kitchen, while only 41 percent of all little house flies within infested homes were found in the kitchen. Little house flies are also more cold-hardy than common house flies, which is why the former emerges earlier in the year than the latter.

Little house flies are known for flying aimlessly and erratically throughout homes where they tend to hover around people’s heads. As their common name suggests, little house flies are smaller than common house flies. Common house flies are between 4 and 7.5 mm in length, while little house flies are between 3 and 5 mm in length, and this minimal size difference is not always clear to the naked eye. Common house flies and little house flies are similar in appearance, but the latter is more slender. In Louisiana where the climate is relatively warm, little house flies can appear in homes throughout the year, as they remain active as long as temperatures are above 40 degrees. Little house flies are also far less tolerant of high temperatures than common house flies, which explains why little house fly infestations are particularly common during the fall and winter seasons.

In homes, little house flies avoid sunlight by congregating in shaded areas, and they favor excrement and rotting vegetable material as breeding sites. Larvae tolerate a wide moisture-range, which makes little house flies particularly difficult to control. While common house flies are considered significant mechanical vectors of bacterial disease, little house flies rarely land on food items due to their habit of constantly remaining airborne.

Have you ever encountered flies within your home during the winter season?