Ptiliidae is a highly diverse yet poorly known group of minute beetles. Approximately 65 genera and over 400 species within three subfamilies have been described worldwide. These numbers are rather conservative, based on the large number of undescribed taxa within existing collections. Acrotrichis is the largest genus, presently containing more than 150 species. Though inhabiting many moderate and tropical regions around the globe (Australia, New Zealand, Japan, South and Central America, Mexico, Africa), only the European taxa have been treated in great depth. Approximately 25 genera and 115 species have been described from America north of Mexico. A key to North American genera is provided by Dybas (1990).

The wing consists of a stalk attached to a long membrane bordered with numerous hairs, giving rise to the common name Featherwing Beetles. Ptiliids represent the smallest known beetles, averaging 0.5 mm to 1.5 mm in length. The extremes range from 0.3 mm ('Nanosella') to 2.0 mm (Acrotrichis godmani). The female spermatheca is a valuable diagnostic character for identifying species, due to its highly variable form. Spermatozoa also exhibit varying characteristics. Female ptiliids develop eggs one at a time within the abdominal region, since egg size is generally half the body length. Morphological polymorphism occurs within some genera (Pteryx, Ptinella, Ptinellodes), usually in the form of 'normal' and 'vestigial' morphs, the latter possessing reduced (or absent) eyes and wings. Some ptiliid genera (Acrotrichis, Bambara, Ptiliopycna) are known to be parthenogenetic.

Adults and larvae of featherwing beetles are usually found together in a variety of habitats including moist leaf litter, mammal nests and dung, rotting cacti, ant and termite colonies, under bark of dead trees, along sand and gravel banks of rivers and streams, beneath seaweed on beaches, and other habitats containing rotting or damp organic material. Some taxa are also specialists of fungi, feeding on the spores produced by the fruiting bodies.