A Population Model for Cinnabar Moth and its Food Plant, Ragwort

(1) This paper attempts to model the interaction of populations of the cinnabar moth and its food plant, ragwort, at Weeting Heath between 1966-77. (2) The proposed model is built from three submodels describing: (i) the effects of rainfall and defoliation by cinnabar on the number and biomass of ragwort; (ii) the effects of food supply and adult density on the moth's fecundity; and (iii) the effects of larval density on mortality. (3) Starting with a known population of plants and of cinnabar eggs, together with an estimate of the percentage of plants flowering in the first year, reasonable estimates of plant and moth numbers may be obtained from the model, provided rainfall data are available for each subsequent year.