Video: Orchid lures bees with promise of sex with strangers

Male bees with an urge to add to the gene pool are exploited by orchids that pose as irresistibly scented exotic females, new research suggests.

Sexually deceptive orchids rely for their own reproduction on male insects’ drive to copulate. If a male mistakes the flowers for a female insects, his fruitless mating attempts will pollinate the orchid.

Some orchid flowers are so exciting to males that they even ejaculate on the flower, but although the visual deception is often superb, what really drives the males wild is the female sex pheromone cocktail that the orchid imitates.


Now Nicolas Vereecken and Florian Schiestl at the University of Zürich in Switzerland have discovered a new trick in the orchids’ repertoire of sexual lures.

Inbreeding bees

When they studied geographic variation in pheromone mixes between 15 different populations of the bee Colletes cunicularius and the orchid that mimics it, Ophrys exaltata, they were surprised to find that the flowers consistently smelled slightly different than the female bees in any given population.

“This was not at all what we expected. If the orchids thrive on imitating female bees, the match should be as perfect as possible”, says Schiestl.

Unless, of course, the males like their girls just a little bit different.

Since the bees enjoy a quiet life and do not travel much, Vereecken and Schiestl speculated that inbreeding may be a common problem. Mating with a stranger may be a welcome opportunity to stir up the gene pool for a bit more variety.

Exotic dancers

And indeed, male bees have the hots for exotic perfume. Given the choice between a dummy infused with the pheromone cocktail produced by the girl bee next door and another one with the bouquet of a female from another population, the males visited the scent that was new to them 50% more often.

But orchid scent, with yet greater differences in the pheromone mix, was even more popular. In choice tests it attracted males up to five times as often as that of a local female.

Manipulating the natural perfume blend of the bees to mimic that of the orchids also nearly doubled the bees’ attractiveness to males.

In other species, such as mice, rare females are popular when inbreeding is common. “When outbreeding is desirable, it makes sense for males to look for females with exotic scent,” says chemical ecologist Manfred Ayasse at the University of Ulm in Germany. “But in this case, what they find instead is the orchid.”

Journal reference: Proceedings of the National Academy of Science (DOI: 10.1073/pnas.0800194105)