Recipe found for orchid aphrodisiac.

Researchers have at last figured out the recipe for one of nature's sexier perfumes, the scent produced by an Ophrys orchid. The blend packs more power than they expected.

The odor wafting from the small, reddish-brown blooms of the European Ophrys sphegodes drives male bees of the species Andrena nigroaenea into such a frenzy that they try to mate with the blossoms. The blooms offer no nectar and depend on these delusory encounters for pollination.

Early attempts to analyze the scent yielded compounds that evoked only mild interest from male bees. Researchers had speculated that the flowers attracted only those bees "with a low threshold for sexual stimuli," as Florian P. Schiestl of the University of Vienna and his colleagues describe the work.

Using new techniques, however, they located and identified a much more potent aphrodisiac. In the June 3 NATURE, they describe exposing male bees to extracts of various parts of both flowers and female bees. The flower power came from the waxy coating on part of the bloom, suggesting that the sexual attractant may have had its evolutionary roots in waterproofing.

The team then ran extracts of both flower and bee parts through a gas chromatograph hitched to male-bee antennae and checked to see which compounds kicked up nerve-cell activity.

Fifteen substances from female bees interested males quite a bit, and the orchid flower turned out to produce 14 of them. A synthetic blend of these fairly simple compounds, straight-chain saturated and unsaturated hydrocarbons, drove males wild with passion. But to the human nose, notes Vienna's Manfred Ayasse, the scent "is almost nothing."