An Index of Food Limitation in the Field for the Larval Dragonfly Anax junius (Odonata: Aeshnidae)

The fecal pellet mass of larval Anax junius of a given size is closely correlated with food intake. The fecal pellet mass under ad libitum feeding can be predicted from a knowledge of larval size, and the accuracy of the predictions is not sensitive to wide variation in the diurnal schedule of feeding, water temperature between 15 and 25°, and dietary composition. Comparisons of masses of fecal pellets produced by field collected larvae with predicted masses for ad libitum feeding should, therefore, be a measure of the degree of food limitation in the field.