OXYGEN-CONSUMPTION IN THE FORAGING HONEYBEE DEPENDS ON THE REWARD RATE AT THE FOOD SOURCE

Oxygen consumption of the honeybee Apis mellifera ligustica was measur ed as a function of the flow rate supply of sucrose solution at an aut omatic feeder located inside a respirometric chamber. Trained bees fre ely entered the respirometric chamber and collected the sucrose soluti on supplied. The mean value of the O-2 consumption rate per visit incr eased with the sucrose flow rate, and for a given flow rate, with incr easing locomotor activity. However, when no locomotor activity was dis played, O-2 consumption also increased with increasing nectar flow rat e. Crop load attained at the end of the visit showed a positive relati onship with the nectar flow rate; however, for a given flow rate, O-2 consumption showed either no correlation or a negative one with the fi nal crop load attained. It is concluded that the energy expenditure of the foraging bee is controlled by a motivational drive whose intensit y depends on the reward rate at the food source.