Stability of Growth and Consumption Rates and Food Utilization Efficiencies When Insects Are given an Excess of Food

Abstract

Third-instar tobacco hornworms, Manduca sexta (L.), were given various amounts of food to determine the effect of food availability on growth and consumption rates and utilization efficiencies. When 0—5% of the food was left over, relative growth rate, relative consumption rate, and efficiency of conversion of digested food had not yet plateaued. When ≥5% of the food was left over, food consumed was no longer correlated with food available. Consequently, providing as much as twice the amount of food required to complete the stadium did not appreciably alter the rates and efficiencies. With as much as triple the food needed to complete the stadium, only the magnitude of the relative growth rate was significantly changed, and the degree of variation in the rates and efficiencies was not altered. Thus, it may be better to give larvae too much food, with up to twice that needed to complete the stadium, than risk larvae reducing the amount of food to <5% of that given to them, whereupon relative growth rate, consumption rate, and conversion of digested food may decline.