The Perissommatidae are a family of flies (Diptera) that was newly proposed in 1962. The family contains five species, four from Australia and one from Chile. The Perissommatidae are unusual as they have four eyes. They have a small slender body less than 2 mm in length. Their wings are large in comparison to their bodies and subsequently their flight is weak. Preferring high-altitude forest environments, adults only fly in the winter. In the case of Perissomma macalpinei, numbers of adults have been observed congregate in clumps of foliage, rising in short, zigzag flights in the sunlight above the foliage for short periods before descending.