We studied the feeding ecology of the neotropical lizard Ameiva ameiva in a semiarid area in the state of Rio Grande do Norte, Brazil. The main food items ingested were insect larvae and pupae, gastropods, beetles, spiders, roaches and orthopterans. The population specialized more in the consumption of larvae and pupae in the rainy season, and consumed different types of prey more evenly in the dry season. The population niche width in the rainy season was narrower, due largely to a lower degree of individual specialization, despite individual niche widths that did not differ significantly between seasons. Individual specialization was stronger in the dry season, causing an expansion in the population niche width. Sexual differences in diet were small, despite sexual dimorphism in body size. Maximum, average and range of prey sizes were positively correlated with lizard body size, but minimum prey size remained constant, resulting in a positive relationship between body size and individual niche width. Despite differences between adult and juvenile lizards in maximum and average prey sizes, the fact that adults continue to feed on small prey suggests that there may be competition for food resources between age classes.