SUMMARY (1) Models are described for the relationships (a) between the percentage of eggs of codling moth disappearing from leaves and fruit in the orchard and numbers of earwigs Forficula auricularia L., and (b) between the percentage of eggs of codling moth sucked out before they can hatch in the orchard and the biomass of their heteropteran and mite predators. (2) For heteropteran predation, introduction of the effect of either alternative prey (Panonychus ulmi Koch) or predator-predator interference does not improve the model, but both together produce significant improvement. (3) The effect of weather (sunshine hours) on the speed of searching also improves the model. (4) Alternative prey and weather make the greatest proportional difference to the percentage of eggs sucked out when predator biomass is low: when more predators are present, these effects are damped by competition and mutual interference or pseudointerference. (5) The model has potential use in management of codling moth infestations in