Honey bees mark artificial flowers with scents that advertise about the previous history of the flower to subsequent foragers. Unrewarding flowers are marked with a scent, after a single visit, that makes the flower less attractive to subsequent foragers. Previously rewarding flowers are initially less attractive than unvisited flowers but become more and more attractive with each rewarding visit. Flowers that have rewarded bees four times are more attractive than unvisited flowers. This attractant is applied by the bees in response to the presence of nectar and is not, as has been suggested by other researchers, inadvertently applied to anything on which the bee lands. Similar scent-markings are applied to a real flower, Lotus corniculatus. One visit was enough to make a flower less attractive to subsequent foragers but flowers that consistently offered high amounts of nectar became more attractive than unvisited flowers. Repellents may be used by bees to avoid revisiting recently emptied flowers while attractants may be applied to flowers within a patch that consistently offer high rewards. The possible selective pressures responsible for the evolution of scent-marking was investigated by doing an energetic analysis. The presence of scent-markings in a patch results in a 33% increase, over an unmarked patch, in the amount of sugar obtained per time. The attractive scent-marking was extracted from a glass flower and maintained its biological activity when applied to a clean glass flower. The extract was chemically analyzed using gas chromatography-mass spectrometry. Four chemicals were identified; none of the chemicals has previously been found in honey bees. Mandibular glands were analyzed as a possible source of the attractant. Although none of the components was found in the gland extracts, two previously unidentified chemicals were found. / Graduation date: 1994