Orchid Lures Prey with Scent of Death

Research led by Dr. TimotheĆ¼s van der Niet at the University of KwaZulu-Natal in South Africa shows that the South African orchid Satyrium pumilum lures flies into its flowers by mimicking the smell of rotting flesh. A new study comparing the scent of the orchids with that of roadkill was published online on March 13, 2011, in the Annals of Botany. The orchid S. pumilum is found in sandy, moist conditions near small streams across the Cape floral kingdom of South Africa. The flowers are a puzzle. They don't carry any nectar and even if they did, the spurs that would hold it are the wrong shape to feed any visitors. So how do they attract insects to pollinate their flowers? Dr. Van der Niet said: "We know it's common for orchids to deceive insects into pollinating them. We also know that some plant species can mimic carrion to attract flies. What we didn't know was how successful this was. Mimicry is often a very poor way to pollinate a plant. So we set out to observe the plants in the wild and see if we could work out how they were attracting flies." The team staked out a region of farmland with many of the orchids on it. They then went about finding carrion for a comparison. Dr. Van der Niet said: "We didn't kill creatures to entice the flies. Instead we used dassies (rock hyraxes). They're small animals and they look a little like a guinea pig. You can find them almost anywhere in South Africa, and that means you can also find them as roadkill. So we examined the flies visiting the dead dassies, and compared them to the flies visiting the orchids. Because of the high density of orchids we didn't see many flies visiting the flowers, but on the nearby dassie carcass we caught a lot of flies carrying orchid pollen, providing ample 'smoking gun' evidence of how common this interaction was.
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