Orchid aids pollination with roadkill

Roadkill or orchid – they both smell the same to flesh flies and a South African orchid which mimics the smell of rotting flesh used this to lure flies into its flowers to aid pollination.

This type of mimicry is often an unsuccessful way to pollinate a plant according to Timotheüs van der Niet, but the Satyrium pumilum – a non-nectar bearing plant found in sandy moist conditions near small streams – uses it to its advantage.

“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,” said van der Niet. “But what we didn’t know was how successful this was.”

Van der Niet and his team staked out a region of farmland with many orchids on it and found a carrion – a dassie or rock hydrax – for comparison.

“Because of the high density of orchids, we didn’t see many flies visiting the flowers, but on the nearby dassie carcass we caught lots of flies carrying orchid pollen, providing ample ‘smoking gun’ evidence of how common this interaction was,” van der Niet said.

Not every species of carrion fly carried the orchid pollen – the ones carrying the pollen were flesh flies, mostly female, which are better at finding food sources than other flies.

The flowers of the orchids are incredible specialised – not only do they have to entice flies in, they have to get flies of the right size into the right position to pick up the pollen, said van der Niet. Scent plays an important role in luring flies to the right location to pick up the pollen.

“The combination of smell and sight is irresistible to some flies,” he said. “The level of carrion mimicry is amazing; we even saw a female fly leave larvae in a flower because she thought it was a carrion.”