ABSTRACT
Four new species of Harpellales are described from the midgut and hindgut of aquatic Diptera larvae: Stachylina manicata and Stachylina lotica (Harpellaceae), and Smittium gigasporus and Smittium ouseli (Legeriomycetaceae). Stachylina lotica is the first Harpellales reported from Psychodidae; the other three were found in Chironomidae. Stachylina manicata was collected in a cattail swamp, whereas the other species were taken from clear mountain streams.