Encarsia formosa was originally described from specimens reared from an unidentified aleyrodid on geranium (Pelargonium sp.) in 1924 in a greenhouse in Idaho (USA) (Gahan 1924). There are no synonyms in the literature. Morphological descriptions of all life stages are provided by Speyer (1927). Because of releases into greenhouses worldwide, E. formosa has a cosmopolitan distribution and its native range is uncertain.