This thesis is a study of the developmental stages of two species of grasshopper. The primary aims have been to establish the number of nymphal instars in each species, to describe and illustrate the anatomical differences between these instars (both within each species and between the two species), and to report any information obtained on the life histories, habitat preferences and the duration of the egg and nymphal stages of the two species selected. Grasshoppers of the family Acrididae occur throughout New Zealand from sea-level to over 7,000 ft. The known fauna comprises twelve species belonging to six genera. Eleven of these species belong to the endemic genera Sigaus (5 species), Brachaspis (2 species), Paprides (2 species) and Alpinacris (2 species). The genus Phaulacridium is represented by one endemic species, P.marginale, which is closely related to the Australian species P.vittatum (Key, pers. comm.). The only species which is not endemic is the cosmopolitan Locusta migratoria. In this thesis the two species selected for study were Phaulacridium marginale (Walk.) and Sigaus campestris (Hutt.).