Bee Prefers Sex With Orchid Over Females

May 27, 2008 -- It's no wonder romantic couples give each other flowers, since researchers have determined one orchid is so attractive to male bees that the males actually prefer sex with the orchid over sex with female bees of their own species.

The finding demonstrates the incredible seductive powers of certain flowers, and how these flowers -- in this case Ophrys orchids -- can compete with female insects for male attention.

The orchid sexual tool kit includes three powerful "weapons" that overwhelm male Colletes cunicularius bees through sight, touch and smell. All three mimic characteristics of female bees that are ready to mate.

"The visual mimicry includes (copying) the color and shape of a female (bee)," co-author Florian Schiestl told Discovery News.

"Tactile memory includes (copying) the hairs on the body of a female," added Schiestl, a University of Zurich botanist and biologist.

He and colleague Nicolas Vereecken focused, however, on the orchid's perfume, which humans cannot smell, but is irresistible to male bees.

One whiff of the scent encourages the bees to hop on flowers and mate with them, just as they would with a female bee. Unbeknownst to the male, pollen from the flower attaches to the bee during the process, so that when he hops to another flower, pollination takes place.

For the study, published in this week's Proceedings of the National Academy of Sciences, the scientists collected 391 virgin C. cunicularius female bees and multiple Ophrys flowers from 15 different populations across Western Europe. Most females within solitary bee species mate just once during their lifetime, so finding virgins wasn't too difficult.

The scientists analyzed the chemical composition of sex pheromones emitted by the female bees and compared this to the chemical make-up of the orchid's perfume. The mixtures were nearly the same, containing the same compounds, except the chemical ratios were different in the orchid, meaning that the flower's perfume wound up being its own unique blend, which the male bees actually preferred over the scent of the female bees' sex pheromones.

The researchers tested this fact by tweaking the female pheromones so that they matched the orchid's perfume. The scent, as expected, drove male bees into a lovemaking frenzy.