Nutritional status affects the endurance of dispersing insects. Populations of many insects show considerable variation in fat storage and vigor as a result of variation in food quality and the quantity and maternal partitioning of nutrient resources to progeny (T. Wagner et al. 1981, Wellington 1980). Many species exhibit obligatory flight distances that are determined by the amount of energy and nutrient reserves; dispersing individuals respond to external stimuli only after depleting these reserves to a threshold level. Hence, less vigorous individuals tend to colonize more proximal habitats, whereas more vigorous individuals fly greater distances and colonize more remote habitats. Because crowding and nutritional status are negatively related, the per capita accumulation of adequate energy reserves and the number of dispersing individuals should peak at intermediate densities when resource quality and quantity are still sufficient to promote insect development and vigor.
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