All: key separating Usiini from Apolysini in Evenhuis, 1989: “Systematics and Evolution of the Genera in the Subfamilies Usiinae and Phthiriinae (Diptera: Bombyliidae) of the World." Contact me
All: key separating the components of Usiini (Usia s. str., Usia (Micrusia), U. martini, U. versicolor, and Parageron s. lat.) in Gibbs, 2014: A world revision of the bee fly tribe Usiini (Diptera, Bombyliidae) Part 2: Usia sensu stricto." Link
All: key to genera of Parageron s. lat. (Ectopusia, Parageron s. str., Parusia, Protypusia) in Gibbs, 2023: “A world review of the bee fly tribe Usiini (Diptera, Bombyliidae) — Part 3: Parageron Paramonov s. lat." Link
Iran: key to species in Gharali et al., 2010: “Two new species of the genus Apolysis (Apolysini, Bombyliidae, Diptera) from the north of Iran." Link
United States: outdated key to species as Apolysis and Oligodranes in Melander, 1946: “Apolysis, Oligodranes and Empidideicus in America (Diptera, Bombyliidae)." Link
All: key to species in Gibbs, 2023: “A world review of the bee fly tribe Usiini (Diptera, Bombyliidae) — Part 3: Parageron Paramonov s. lat." Link
All: key to species in Gibbs, 2023: “A world review of the bee fly tribe Usiini (Diptera, Bombyliidae) — Part 3: Parageron Paramonov s. lat." Link
All: key to species in Gibbs, 2023: “A world review of the bee fly tribe Usiini (Diptera, Bombyliidae) — Part 3: Parageron Paramonov s. lat." Link
All: key to species of Usia (Micrusia), U. versicolor, and U. martini in Gibbs, 2011: “A world revision of the bee fly tribe Usiini (Diptera, Bombyliidae)—Part 1: Usia subgenus Micrusia, U. versicolor (Fabricius) (= black-haired species) and Usia martini François." Link
All: key to species of Usia s. str. in Gibbs, 2014: “A world revision of the bee fly tribe Usiini (Diptera, Bombyliidae) Part 2: Usia sensu stricto." Link