Women might use perfume to impress each other or to attract men. But scientists say that it could attract something else: angry hornets.
Japanese researchers extracted venom from the world's largest species of hornet and found that the venom contains at least one ingredient, also used in perfumes, that prompts other hornets to attack at the slightest whiff.
Representatives of the fragrance industry said the study is flawed and the results misleading. "It's a nice story, but these guys are wrong," said Glenn Roberts, a spokesman for the Washington-based Fragrance Materials Association.
But experts on insect pheromones - chemicals that trigger a particular response - say that the findings are consistent with what they've been saying for years: that insects respond to a variety of scents and signals.
"It's very good science," said Thomas Eisner, an entomologist at Cornell University who reviewed the study. "The lesson is, if you are going into country where there are going to be wasps and bees, you'd do well not to wear perfume."
Scientists know that honeybees might be agitated by rotting bananas. Ants spray a chemical to warn other ants of a threat, and mosquitoes find victims at summer picnics by the carbon dioxide they emit. Decades of pheromone research also has led to traps that will attract and kill mosquitoes, ants, wasps and bees.
"Insects use chemical cues of one sort or another to get key signals from their environment," said Lou Bjostad, a Colorado State University entomologist who also reviewed the study. "We've known that for decades."
The researchers at Tamagawa University took venom from three frozen samples of Vespa mandarinia, a species indigenous to Japan, where it's known as the giant hornet. They analyzed the contents, created an extract and then exposed a competing hornet species to it. The smaller hornets, Vespa simillima xanthoptera, responded as if they were under attack, the study says.
"The crude venom extract caused intense alarm and defensive behavior, with worker hornets flying excitedly around the nest and rushing toward the target," the study says.
Masato Ono, the lead author, declined in e-mail responses to identify specific perfumes that contain the compounds, but said the chemicals also are found in additives used to create banana, apple and other fruit flavors in commercially prepared foods.
Eisner said it's not surprising that a hornet's pheromones alarm a competitor. "You have winners and losers in the animal world, and when a winner produces a chemical, you can expect the loser to become chemically aware and respond to it," he said.
The giant hornet that emits the venom is not found in North America but has several cousins on the continent. "They're not here yet, but give them time, they will be," said Eisner, who has studied pheromones in termites and ants.
A hornet is a kind of wasp and a member of the hymenopteran family of insects that includes bees, wasps and yellow jackets. All use venom - which contains 30 different compounds - to defend themselves or to kill or paralyze prey.
The study, published in today's issue of Nature, notes that hornet and bee stings kill dozens of people each year and recommends that products with the compounds be screened to see if they attract hornets. Wasp and bee stings kill about 45 people in the U.S. and 70 people in Japan each year.
The researchers say three compounds that alarmed the hornets were in the venom of all seven species of hornet found in Japan. They identified the chemicals as 2-pentanol; 3-methyl-1-butanol, and 1- methylbutyl - 3 - methylbutanoate.
Roberts said that only one of the compounds, 3-methyl-1-butanol, is used in perfumes. He added that the compound, one of hundreds of ingredients used in perfumes, is highly volatile, evaporates quickly and is generally used in much smaller quantities than the researchers used in their tests.
"It's like studies where they give rats tons and tons of something to see what effects it will have, but the dosages are much higher than what you would have in the real world," he said.
The Food and Drug Administration does not require perfumers to list their ingredients on containers. "A lot of these fragrances have several hundred ingredients, so as a practical matter, they're just not listed on a label," said Roberts, the industry spokesman.