A distinct scent can unleash a flood of memories, volumes worth, as readers of Marcel Proust may recall. But in addition to their memoryenhancing powers, smells are also a royal road to pollination: plants routinely use fragrances to attract bees, moths, butterflies, beetles, and other grazers. Some insects sense redolent flowers, like evening primrose, honeysuckle, and skunk cabbage, well before they can see them. The smell increases with proximity as the pollinator is guided by its nose to the nectar source.
Temperature shifts in the evening may be accompanied by dramatic shifts in odor, with some plants becoming much more aromatic after dark. Nightfragrant flowers are often dull to look at, but that doesn't deter pollinators, who can't discern color shades in the dark and are lured strictly by smell. There's often a changing of the guard at dusk in a flower garden, with nocturnal moths and mosquitoes taking over pollination duties from bees, hummingbirds, and butterflies.
Olfaction, as with other senses, is highly personalized, varying from animal to animal: what appeals to one species may repel another. Bats are drawn to strong, musty odors, whereas bees prefer lighter, floral scents. Many birds, on the other hand, have a poor sense of smell and do not seek out heavily perfumed plant varieties.
At the far end of the olfactory spectrum are flowers like rafflesia, devil's claw, and voodoo lily that give off the smell of rotting meat. While humans might run for cover, carrion flies flock to this rancid stench. As the time for reproduction nears, the voodoo lily, for example, boosts its temperature, which enhances the scent the flies crave. After landing on the slippery petals, the flies slide into a cavity where they are trapped for days, with nothing to do but eat nectar and unwittingly cover themselves with pollen. Once the pollen has been adequately collected, the flowers release the flies with the presumption that they will soon visit other voodoo lily flowers and pollinate them. The cycle continues anew with the nose leading the charge.
More than 80 percent of the world's 250,000 flowering plants depend on animal pollinators, and roughly 15 to 30 percent of the food eaten throughout the world comes from plants pollinated by these creatures.