Experience-dependent choices ensure species-specific fragrance accumulation in male orchid bees

Male neotropical orchid bees (Euglossini) collect volatile chemicals from orchid flowers and other sources and store them in hind leg cavities. The accumulated fragrance bouquets are later emitted at mating sites. Although most other insects synthesize pheromone blends de novo, specific euglossine perfumes are derived from active choices in a changing fragrance market. Male bees of three species of Euglossa possessed distinctive fragrance phenotypes showing little variation by locality and habitat in mainland Central America. In cage experiments, fragrance choice by male Euglossa imperialis was influenced markedly by a bee's collection history. Collection of a given chemical strongly reduced its attractiveness on subsequent occasions, an effect that was retained over days. Experimentally adding the chemicals directly to bee hind legs produced no effect. We conclude that bees learn and remember chemicals they collect. Innate odor preferences, memory and the avoidance of overcollecting by negative feedback may be the primary mechanisms that ensure unique blends of pheromone analogs in these tropical forest bees.