Though orchids are considered some of the most beautiful flowers in the world, their scent has evolved over eons to precisely emulate the smell of a dead body. In fact, according to biologists, orchids emit an odor extremely similar to roadkill. Why would flowers need to stink of death?
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In a study published today in The Annals of Botany, South African biologists report on their research into why these flowers reek of death. It turns out that they can only be pollinated by a very specific type of fly, which is attracted to the smell of dead bodies.
Botanist Timotheüs van der Niet and his colleagues located several pieces of rotting roadkill in their native South Africa, and studied the flies they found landing on it. The ones who were most covered in orchid pollen were all "flesh flies," who lay their eggs in corpses.
At left, you can see a picture of one of the flies emerging from an orchid covered in tiny yellow balls of pollen.
Van der Niet said:
The flowers of the orchids are incredibly specialised. Not only do they have to entice flies in, but they have to get flies of the right size into the right position to pick up the pollen. We've found that scent plays a hugely important role in pulling in the flies, and even inside the flower different scents attract the flies into the right location to pick up the pollen. The combination of smell and sight is irresistible to some flies. The level of carrion mimicry is amazing; we even saw a female fly leave larvae in a flower because it thought it was carrion.
What this study proves is that flowers can evolve to attract very specific kinds of flies, placing them in a delicate balance with the ecosystem where only a few species will ever be attracted enough to the flowers' scent to spread their pollen around.
Quipped van der Niet about the study: "It also disproves a cliché, you don't always catch more flies with honey."
Read the full scientific paper at the Annals of Botany