Researchers develop traps to remove invasive giant hornets

(CN) — Researchers developed a method for identifying and potentially removing invasive Asian giant hornets using the sex pheromones of the insects.

The Asian giant hornet — the world’s largest hornet, sometimes referred to erroneously as the ‘murder hornet’ — is not native to North America but has made its way to Washington State and British Columbia, Canada. Scientists do not yet know how the insect arrived but say its invasion of the ecosystem must be stopped before the hornets wreak havoc on North America’s bee population and agriculture industry. Research published Monday in the journal Current Biology aims to provide a possible tactic for curbing the species’ spread.

The researchers identified three compounds present in the sex pheromones of the female Asian giant hornet. Those compounds can be easily purchased from a chemical supply company to fashion what researchers found to be a largely effective trap.

“The females of these pest species produce a sex pheromone that draws in males, often from great distances, because it's to the male's advantage to find females and mate,” explained James Nieh, biological sciences professor at the University of California, San Diego and one of the study’s authors.

Nieh said the traps are largely pieces of cardboard lined with the sticky material seen on rat and mouse traps. Using both a decoy female hornet as a visual stimulus and the odor compounds the researchers identified, Nieh said they attracted hundreds of male Asian giant hornets.

The traps did not attract any females or any other species of insect. According to Nieh, this could prove crucial, as the traps could possibly “provide disruption of the mating system if enough of the males are actually captured within a given area.”

The trap’s success in attracting the Asian giant hornet could also be helpful in monitoring the extent of the species’ invasion. Researchers typically rely on actual sightings of the hornets or reports from beekeepers about dead bees in their colonies.

The removal of the species is important, according to researchers, because the hornets pose a major threat to the biodiversity of North America’s bees. Consequently, they threaten the agriculture industry that the bee colonies help pollinate.

“The reason why [the hornets are] so worrisome is that a single attack has the ability — even in species that have defenses against this hornet — to kill about 30% of the colony,” Nieh explained. “Relatively few hornets can actually kill colonies or do serious damage to them.”  

Rather than patenting their identification of the Asian giant hornet’s sex pheromone, Nieh said he and his fellow researchers wanted to publish their findings quickly so their methods could be more widely used and perhaps remove some of the invasive hornets.

“We think the best thing to do given the urgency of this is to actually run this in the field in North America and Canada and see if it actually works,” Nieh said, adding that they still have components within the sex pheromone to identify that could make the trap even more effective.

Nieh said the research team’s trap was inspired by their previous research on another invasive hornet species in Europe. They extracted the sex pheromones from certain female hornets by rubbing part of their bodies with filter paper. When the strips of filter paper were placed in a cage with 50 male hornets, the males went into a “mating frenzy,” even trying to mate with the other males on the filter paper strips. The electrical neural activity in the males’ antennae showed they were particularly sensitive to the compounds, which the researchers identified through chemical analysis of the filter paper strips.

Nieh and his fellow researchers in North America and China plan to conduct future experiments, including placing the traps greater distances from the colony to see how it affects the male hornets’ responsiveness to the pheromones.

Nieh emphasized that the term ‘murder hornets’ is “catchy,” but has sensationalized the species. He said the hornets are not murderous, only seeking to feed their larvae and subsist as other species do.

“These hornets definitely don't belong here and they should be removed because they will harm our natural ecosystems, and also our agricultural ecosystem by harming honeybees. But we should think of them in their own right as amazing, well-adapted animals. They just don't belong here,” Nieh said.

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