Abstract

Forest tent caterpillars are an outbreaking forest pest native to North America, whose population cycles have been linked to variations in larval survivorship, adult fecundity and nutrition. These insects only feed as larvae, therefore the acquisition of appropriate nutrients during the larval stage for survival and reproduction of adults is essential. The present work focuses on the nutritional performance and behaviour of this caterpillar based on diets of varying nutritional quality: their preferred tree host (aspen), or artificial food. Caterpillars performed best on their preferred food source. Protein deficiency did have negative fitness consequences, both in larval survivorship, and quality of offspring. Adult body composition was regulated despite variation in food nutrient ratios. Feeding patterns demonstrated that on diets high in protein content, feeding bouts and pauses between feedings were longer than on low protein diets, on which the caterpillars were more active. This difference might be related to post-ingestive effects via haemolymph trehalose levels. There was no difference in the total time spent feeding or in exploratory behaviour between the artificial diets. When faced with aspen, the caterpillars were also active, had short feeding durations and interfeed pauses. Caterpillars on aspen were more likely to leave the trail and discover a new food source, and they preferred balanced artificial diet to aspen foliage. It is suggested that forest tent caterpillars are inefficient at making initial choices, but in the long run they are capable of post-ingestively regulating their body content.