The Prosimulium of Canada and Alaska (Diptera: Simuliidae)

The 33 species of Prosimulium Roubaud known from Canada and Alaska are reviewed. These are segregated into four subgenera: Distosimulium new subgenus, containing one species; Parahelodon new subgenus, containing three species; Helodon Enderlein, containing seven species of which clavatum, martini, and susanae are new, and one (known only from the larva) remains undescribed; Prosimulium s. str., containing 25 species of which approximatum, constrictistylum, impostor, mysticium, neomacropyga, and woodorum are new. Species of the last subgenus are segregated into three species groups. A lectotype is designated for P. ursinum (Edwards). Descriptions, distribution maps, keys, and 158 illustrations for the identification of the known adults, pupae, and larvae are provided.