Since first reported seen in the United States in 2019, the invasive Asian giant hornet (Vespa mandarinia) has sent researchers into a frenzy to eradicate them. The insects, native to East Asia and Japan, can decimate honey bees and native beehives in hours, threatening bee-pollinated crops worth over $3 billion annually in Washington state.
Now, scientists have found a way to use the insects' sex pheromones against horny hornets, reports Isaac Schultz for Gizmodo. When researchers placed synthetic pheromones in field traps that mimicked hornet queens produced, hundreds of males flocked to the site. Details of the study were published this week in Current Biology.
"We were able to isolate the major components of the female sex pheromone, an odor blend that is highly attractive to males who compete to mate with virgin queens," study author James Nieh, an entomologist at the University of California in San Diego, tells Gizmodo. "When these components or their blend was tested in sticky traps, they captured thousands of males."
Entomologists obtained the pheromone by swabbing various virgin giant hornet queens captured in Yunnan, China. The team swabbed each of the queen's sex glands and used gas chromatography and mass spectrometry to identify the compounds that lure in male murder hornets, per Gizmodo.
The top three compounds in the queen's pheromone were hexanoic acid, octanoic acid, and decanoic acid, Science New's Erin Garcia De Jesús reports. Hexanoic acid has a fatty, cheesy, or urinous odor, per Gizmodo. Decanoic acid is pungent and found in fruit flavorings, while octanoic acid is found in animal milk.
When the compounds were tested on the male hornets, the team saw that their antennas retracted, a sign of attraction in the insects. The results were the same when each compound was tested individually and then mixed. To further test out the pheromone, researchers made traps from a sticky board, a fake male hornet, a glass tube filled with the odorous acids, and another tube filled with extracts from the queen's glands, Science News reports.
Male hornets made a beeline for the queen's natural pheromones but also were attracted to the synthetic mix. The queen's pheromones attracted about 500 male hornets, more than twice the number drawn by the three-chemical concoction. Female hornets and other insects were not lured in by the scent, Gizmodo reports.
Based on these results, the team suspects other compounds in the queen's pheromone still need to be identified to make the trap more effective for male hornets.
The study could bring scientists closer to identifying easy ways to trap the invasive insects. Asian giant hornets can be difficult to eradicate because they are elusive and create well-hidden nests. Scientists have previously removed hornets is after identifying a nest and using a vacuum to trap them in a tube.
Timothy Lawrence, a bee scientist at Washington State University who not involved with the study, told Science News that the find is important work and a massive step towards eradicating the insects.
"The sooner we find a reliable way to attract males and find nests, the better," Laurence told Science News.