Model for Simulating Consumption and Economic Injury Level for the Range Caterpillar (Lepidoptera: Saturniidae)1

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Abstract
A simulation model for forage consumption by larvae of Hemileuca oliviae Cockerell is described. The model was constructed from a previously published model for population development and mortality, together with the results of laboratory studies on consumption rates and field studies on feeding behavior. Predicted consumption agreed favorably with forage losses observed in the field (R2 = 0.95). The model was used to investigate the relationship between age structure of the insect population and economic injury levels, which are defined for populations in all stages of development. The density of larvae which cause economic damage decreased during early population development because of considerable mortality in the first three instars. Economic injury levels remained relatively constant for the middle developmental period but increased dramatically during the late instars. Implications of the dynamic behavior of the system are discussed with reference to management practices and suppression strategies.