A study is underway to revise the taxonomy of two closely related genera of mayflies from the Leptophlebiidae ; Nousia (Navás 1918) and Koorrnonga (Campbell and Suter 1988). Nymphs continue to be collected extensively throughout Victoria, New South Wales and Tasmania to be reared in specially designed chambers in the laboratory. Two or three species of Koorrnonga and 17 species of Nousia have so far been identified but are yet to be confirmed by adult association. Factors affecting rearing success have been examined.