The significance of multicomponent pheromones in denoting specific compositions

The chemical composition of Dufour's gland secretions of 13 species of halictine bees was investigated. The secretions were composed of a series of macrocyclic lactones, hydrocarbons and isopentenyl esters. The number and relative intensities of these compounds were unevenly distributed among the species, i.e. the secretions were species specific. Based on the empirical data, an algorithm was constructed in order to assess how many of the components present in a secretion are required to discriminate between species, non-related conspecific individuals or nestmates. The results demonstrate that the number of components required for recognition increases with the increase in the level of specificity and with the number of individuals to be identified. The number of compounds denoting identity in a species specific blend may be surprisingly low. Using a similar technique, we assessed the number of components a secretion must contain in order to obtain individual recognition at different levels of relatedness. Several predictions regarding the level of recognition that can be attained by a given pheromone in a given population can be made from these theoretical results.