Spatial and temporal patterns of predation by ants on eggs of Cactoblastis cactorum

Predation of Cactoblastis cactorum (Berg) (Lepidoptera: Pyralidae) eggs by ants was studied for a summer and a winter generation on prickly pear Opuntia ficus‐indica (L.) Miller plants in the field. Egg Predation between plants was spatially density‐dependent in the winter but not in the summer generation. To test for the presence of delayed density‐dependent mortality within generations, percentage egg Predation during 5‐day periods was plotted against the number of eggs available in each period. Data points joined in a time sequence moved in an anticlockwise direction in the summer generation, suggesting a delayed density‐dependent response by the ants, whereas in the winter generation the points moved in a clockwise direction. The degree of coincidence of the C. cactorum eggs with the peak larval production periods of the ants is suggested as the main reason for the temporal changes in egg Predation.