What causes generation cycles in populations of stored-product moths?

1. Populations of stored-products moths such as the Indian meal moth (Plodia interpunctella) frequently show generation cycles, fluctuations with a period of approximately one generation. 2. Three age-structured models of stored-product moth dynamics were investigated to see which best accounted for the observed period and pattern of Plodia dynamics. 3. A model of Gurney, Nisbet & Lawton (1983) was modified to match Plodia biology. The model assumes uniform competition amongst larvae. It predicted generation cycles, but of too long a period and with the wrong larval cohort structure. 4. The introduction of asymmetric competition (young larvae more sensitive to resource depletion but exerting weaker competitive effects) could produce generation cycles but for parameters appropriate to Plodia predicted cycles with a period of half a generation. 5. Introducing egg cannibalism to the asymmetric competition model led to the prediction of generation cycles of the right period and cohort structure for Plodia parameters.