Sex traps can lure thousands of male giant hornets to their death, study finds

By Megan Marples, CNN

Watch out giant hornets, your next mating could be your last.

Researchers found that giant hornets can be lured into traps using sex pheromones, according to a new study published in the journal Current Biology.

The hornets, Vespa mandarinia, are an invasive species in North America and are originally from Asia. While Asian bees have adapted to protect themselves from the predatory hornets, North American bees have not.

Giant hornets have wreaked havoc on the bee population in the United States. It’s estimated the giant hornets — the largest in the world — harm over $100 million of bee-pollinated crops production annually.

Many people often refer to them as “murder hornets,” but it’s a sensational name that should be avoided, said study author James Nieh, professor and associate dean in the department of biological sciences at the University of California San Diego.

“They are predators, but so are lions and tigers, and we don’t call them murder lions,” he said.

Trapping the invasive insects

Nieh’s team created a series of traps using sex pheromones to attract male hornets. Pheromones are chemicals that are produced to convey information within a species, according to Nieh.

Male hornets are attracted to the female hornet’s sex pheromone, so researchers used their own mixtures of synthetic pheromones along with a natural sex pheromone from a female Vespa mandarinia to test which traps would perform the best.

Each trap was outfitted with a dummy female hornet to attract the males as well, Nieh said.

“Hornets would be attracted and fly around the traps, but none of them would land if there was nothing there that looked like a female hornet,” he explained.

After setting them up near hornet colonies in China’s Yunnan province, the researchers found that the queen-equivalent pheromone was the most successful. It’s made of hexanoic acid, octanoic acid and decanoic acid, the study said.

The winning trap captured more than 16 times more hornets than a trap without pheromones, according to the study. After leaving the traps out for a day, the scientists were able to capture thousands of hornets, Nieh said.

Stopping the hornets in their tracks

Researchers used materials similar to a sticky mouse trap, making it easy for other scientists to re-create them and use them on hornets around North America, Nieh said.

The chemicals can also be easily purchased at chemical suppliers in the United States, which makes it even easier to implement this trapping method, he added.

While it’s an effective method to capture a large number of giant hornets in a short period of time, it may not be an ideal system, said Allen Gibbs, a professor in the department of life sciences at the University of Nevada, Las Vegas, who was not involved in the study.

“This method attracts males, but if they’ve already mated, the females are free to fly off and start a new colony,” he said.

Additionally, the hornets only mate for a few months in the fall, so the trapping method could only be implemented during that time, Gibbs noted.

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