Orchid Mimics Carrion to Attract Flies

Scientists studying a South African orchid determined, with the clever use of roadkill, that the flower attracts pollinators by mimicking the scent of carrion. Their report appears in the Annals of Botany.

The Satyrium pumilum orchid grows in sandy, moist soil near streams in South Africa. Unlike most flowers, S. pumilum doesn't have any nectar that would attract pollinators. But the flowers do somehow attract flies. And when the scientists placed near the orchids the carcass of a rock hyrax retrieved from a roadside, they found that a lot of the flies were carrying orchid pollen.

Further experiments revealed that the orchids were indeed producing a carrion-like scent, though it was relatively weak. But that was the perfect amount to attract flesh flies that prefer small carrion. The scent is close enough to the real thing that female flesh flies will sometimes even deposit their larvae on flowers instead of in a dead animal.

"What we've done is show for the first time that carrion-mimicking flowers are highly sophisticated tools for orchids," said the study's lead author, Timotheüs van der Niet of the University of KwaZulu-Natal in South Africa. "It also disproves a cliche---you don't always catch more flies with honey."

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Sarah Zielinski is an award-winning science writer and editor. She is a contributing writer in science for Smithsonian.com and blogs at Wild Things, which appears on Science News.