Effects of Age and Meal Composition on Feeding Behavior and Postfeeding Diuresis in Adult Helicoverpa zea (Lepidoptera: Noctuidae)

Abstract

The effects of age and meal composition on feeding behavior and postfeeding diuresis in corn earworm moths have been investigated. Meal size is governed by the type of sugar present and its concentration, and postfeeding weight loss appears to be regulated by the effect of the ingested meal on hemolymph osmolarity by the control of crop emptying. For each age group tested, meal size increased with increasing sucrose concentration. Meal size also increased with insect age at any given sucrose concentration. High concentrations of ingested sucrose resulted in an increase in hemolymph osmolarity, and a reduction in crop emptying and subsequent postfeeding weight loss. Intrahemocoelic injection of glucose or trehalose following low-concentration sucrose meals was also effective in reducing postfeeding weight loss. Glucose and fructose meals were usually smaller than sucrose meals, but the patterns of postfeeding diuresis were similar. These results strongly suggest that there is a postdigestion control site for the regulation of postfeeding diuresis in this insect, and that hemolymph osmolarity and its effect on crop emptying serve to control the processing of a meal following feeding.