ABSTRACT. Feeding patterns of Locusta migratoria L. nymphs, kept under LD 12:12 at 30°C with ample food, were analysed over the first 6 days of the fifth instar. A number of differences were found between the light and dark phases. (1) More was eaten during the light than the dark, with the differences becoming progressively larger over the 6 days. (2) During light phases most insects showed an increasing tendency to feed with time since the last meal, while in the dark the probability of starting to feed remained constant. (3) There was little variation in feeding patterns within the light phase, but marked changes occurred within the dark phase, feeding declining to a low level in the last 4h. The amount eaten during a meal was regulated similarly in the light and dark, with time rather than amount eaten being of paramount importance in terminating a meal. The time when feeding started was somewhat influenced by the size of the preceding meal, but once feeding began meal size was largely independent of the preceding meal. The importance of food quality in determining the pattern of feeding is discussed.