The amounts eaten by Locusta migratoria migratorioides (R. & F.) on seedling grasses was less than on mature grasses in four other Acridids, Nomadacris septemfasciata (Serv.), Chortoicetes terminifera (Wlk.), Melanoplus sanguinipes (F.) and Schistocerca gregaria (Forsk.). Palatability of the young grasses increases with age, becoming maximal 6-10 weeks from the time of germination. Similar preferences were shown by other Acridids. Time-lapse film studies on Locusta showed that not only is less time spent feeding on seedling grasses, but that locomotor activity levels are considerably higher. Survival studies on the same species showed higher mortality on the seedlings as compared with the mature leaves at all stages of nymphal development, while on seedlings no individuals survived to the adult stage. Lipid-soluble materials were removed from seedling leaves with chloroform or acetone and this rendered them more acceptable, while the extract applied to mature leaves resulted in reduced palatability.