An experimental survey was carried out in western Spain to investigate both the chronobiology of Hypoderma spp. and the immunoresponse of their bovine hosts. This study was initiated with a new system of obtaining Hypoderma spp. larvae directly from their host, including the eclosion of adults from their pupae, infestation under natural but controlled conditions, and confirmation of the resulting infection. This survey was carried out over 2 cattle grub seasons; it was possible to infest and reinfest the experimental animals and to monitor them by both parasitological methods and by an enzyme-linked immunosorbent assay. This method permitted the evaluation of the development of anti-Hypoderma antibodies during the experiment. The experimental design also enabled us to establish the period of detectable H. lineatum infection to be from December until the end of April with the largest number of warbles observed during March and April. After a pupal period of < 30 d, adults were seen in April and May. Hypoderma bovis (de Geer) showed a delay of 2 m.o. relative to H. lineatum (de Villiers). This study reports a completed biological life cycle of Hypoderma spp. under controlled conditions in both natural and experimental environments.