The developmental pattern and life cycle of the tick Amblyomma loculosum infesting seabirds and lizards on Aride Island, Seychelles are described. The activity of A. loculosum (from June to September) was coincident with the breeding season of ground-nesting seabirds, particularly Sterna fuscata. Nymphs fed on incubating adults in June, adults mostly on young chicks (July) and larvae on skinks (Mabuya sechellensis) and large chicks (September/October). The distribution of adult ticks fitted an aggregated distribution. Duration of the life cycle is typically one year, and most ticks may survive nymphal diapause. Chicks served as hosts for more than a tick stage in a season. If alternative hosts to seabirds are absent, the tick developmental pattern is different: adult ticks feed on incubating birds, larvae on young chicks and nymphs on large chicks. Skinks are presumably more reliable hosts for larvae than chicks (which suffer frequent mass mortalities) but are of minor importance for nymphs and adult ticks.