Sub-Optimal Foraging in the Ant-Lion Macroleon quinquemaculatus

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Abstract
The prey acceptance/rejection behavior of 3rd instar M. quinquemaculatus larvae feeding on the small ant Pheidole sp. is described and quantified. Small larvae always caught and consumed the ant but larvae weighing > 59 mg fed inconsistently, becoming increasingly selective with increasing size. The growth rates of consistently feeding, inconsistently feeding and starved ant-lion larvae were measured. Inconsistently feeding larvae showed a 53% greater weight loss than starved larvae of the same size, i.e., there was a net weight loss from feeding on Pheidole. This sub-optimal behavior can be explained by assuming that hunger lowers the feeding threshold sufficiently for the predator to attack unsuitable prey.