A male orchid bee brushes volatile compounds onto pads of specialised hairs on his front legs, transfers the load in flight, and stows it inside a spongy cavity within the enlarged hind tibia. The stored blend accumulates over his life and is drawn from many sources, including orchid flowers, decaying wood, fungi and resins, so it is a compound signature rather than a single floral scent.
The bees release the mixture during display near perching sites, and it is widely interpreted as a courtship signal that females assess. Direct evidence that females choose males on the basis of the collected blend remains thinner than the popularity of the story suggests, and alternative roles such as species recognition or male aggregation cues are still discussed.
Several hundred neotropical orchid species depend on these visits, offering fragrance instead of nectar and gluing pollen packets onto a bee that arrives only to collect scent. Because males are drawn to pure chemical baits, researchers can census whole communities by setting out compounds such as cineole on blotting paper.