This paper by Eric L. Charnov explores the optimal foraging strategy of the mantid *Hierodula crassa*. Charnov develops a simple model to predict the breadth of diet for a random-encounter situation, which is then compared with the behavior of the mantid. The model assumes that the predator encounters individual prey items, handles them one at a time, and has no time to recognize prey types before deciding to pursue. The goal is to maximize the net rate of caloric intake during a foraging period. The model predicts that the optimal set of prey types to be eaten is those ranked by the ratio of expected net energy to handling time, with the addition or removal of prey types based on their rank. Charnov tests this hypothesis using data from Dr. C. S. Holling's experiments on the mantid's predation of houseflies. The mantid's behavior aligns with the model's predictions: it adds or drops prey types in rank order based on the rate of food intake, and a prey type not in the diet cannot be added by increased abundance. However, Charnov acknowledges that alternative hypotheses, such as increased willingness to stalk further due to hunger, are not excluded. The paper concludes by discussing the limitations of the model and the broader implications of optimal foraging theory.This paper by Eric L. Charnov explores the optimal foraging strategy of the mantid *Hierodula crassa*. Charnov develops a simple model to predict the breadth of diet for a random-encounter situation, which is then compared with the behavior of the mantid. The model assumes that the predator encounters individual prey items, handles them one at a time, and has no time to recognize prey types before deciding to pursue. The goal is to maximize the net rate of caloric intake during a foraging period. The model predicts that the optimal set of prey types to be eaten is those ranked by the ratio of expected net energy to handling time, with the addition or removal of prey types based on their rank. Charnov tests this hypothesis using data from Dr. C. S. Holling's experiments on the mantid's predation of houseflies. The mantid's behavior aligns with the model's predictions: it adds or drops prey types in rank order based on the rate of food intake, and a prey type not in the diet cannot be added by increased abundance. However, Charnov acknowledges that alternative hypotheses, such as increased willingness to stalk further due to hunger, are not excluded. The paper concludes by discussing the limitations of the model and the broader implications of optimal foraging theory.