• Locusta migratoria;
  • Spodoptera littoralis;
  • dietary selection;
  • feeding behaviour;
  • compensation;
  • nutrition.

ABSTRACT Final instar nymphs of Locusta migratoria (L.) and larvae of Spodoptera littoralis (Boisduval) were given an artificial diet deficient in either protein or digestible carbohydrate for a single meal during ad libitum feeding, after which they were provided with a choice of two diets, one containing protein but no digestible carbohydrate and the other containing carbohydrate but no protein. Detailed analyses of feeding behaviour showed that locusts exhibited a degree of compensatory dietary selection following the single deficient meal. No such response was evident for the caterpillars, although previous work (Simpson et al., 1988) has demonstrated that compensatory selection behaviour is marked in this species after periods of 4 h or more on the same deficient diets. These results show that locusts are able to respond extremely rapidly to the nutritional quality of their food by utilizing nutritional feedbacks. This capability may have important implications for the study of foraging strategies in other herbivorous insects.