What Are 'Murder Hornets'? How to Trap the Insects As U.S. Prepares for 2021 Season

Asian giant hornets have developed a fearsome reputation in the U.S. thanks to their size, powerful sting and predilection for decapitating honey bees.

The Vespa mandarinia, better known by its nickname the "murder hornet," is the world's largest hornet and U.S. scientists and federal authorities are gearing up for a new season.

An effort to track and eradicate the giant wasps is being led by officials in Washington state, where they were first spotted in December 2019.

The Washington State Department of Agriculture verified two reports of the hornets near the city of Blaine, marking the first sighting in the country.

Canadian officials found the species in two locations in British Columbia in fall 2019.

Last year, both regions confirmed additional sightings of the hornets, leading to the first eradication of a giant hornet nest in the U.S. last October. A nest was found in a tree at a home in Blaine, and 98 worker hornets were killed.

They are described as an invasive pest by wildlife authorities, As the name suggests, they are typically found in tropical areas of southern and eastern Asia.

Female Asian giant hornets can reach lengths of nearly 2.5 inches, with the workers usually slightly smaller. The flying insects have a bright orange head and big eyes, and their bodies have a distinctive pattern of yellow, black and brown stripes.

Because of their size, the hornets are able to deliver more venom than the typical wasp and can sting repeatedly with enough force to puncture a beekeeper's protective clothing.

Asian giant hornets live in social colonies, started by a single queen, and typically build their nests underground, according to the National History Museum in London.

They are known to feed on other insects, with their ruthless siege on honey bee hives often used to justify the "murder hornet" nickname.

Scientists have documented that Asian giant hornets use scouts to locate bee hives, then put out pheromone markers for the other hornets to follow. The wasps then enter what has been called a "slaughter phase," where they kill the adult bees by decapitation before taking larvae as food. This new food source is aggressively guarded.

Experts say an entire bee hive can be wiped out by a few hornets in hours. European honey bees have no natural or evolved defense against such an attack and an influx of the giant wasps could pose a major threat to bees and the crops they pollinate.

Despite their reputation, it is not believed the hornets are intentionally aggressive and they do not generally attack humans or pets—although they will sting if they feel under threat.

A report by North Dakota State University points out that human deaths from hornet stings are "quite rare," with most linked to allergic reactions. It is not clear how the insects came to British Columbia and Washington, but trade routes are likely.

The Washington State Department of Agriculture says residents can participate in its citizen scientist trapping plan to help eradicate the hornets. It suggests trapping them between July and November, when the workers are more likely to be active.

"Trapping at other times is unlikely to catch Asian giant hornets based on their life cycle and will unnecessarily kill local insects," it has warned on its website.

The agency said it would continue to use orange juice and rice cooking wine in its traps this year, but suggested that citizen scientists in Washington could also try a brown sugar-based bait. It has published detailed instructions on how to create a bottle trap on its website.

Residents are advised to cut a star-shaped opening into the bottle, which is baited with alcoholic rice cooking wine and orange juice, or dark brown sugar and water. The bottle should be placed 6 feet high on trees, close to forest edges if possible.

The location should be logged on the agency's Hornet Watch Trap Submission Map. It must be emptied and refilled once a week, for the full 22-week season.

The department said: "If you find a live Asian giant hornet in your trap when you check it—do not handle the trap. Contact WSDA immediately at 1-800-443-6684. You only need to report catches of suspected Asian giant hornets. If you suspect you have caught one in your trap collection, take a photo and email it, along with the date and trap number, to aghtrapping@agr.wa.gov. Keep the specimen until WSDA confirms your find."

The agency added that its trapping would be focused on Whatcom County, where the wasps were detected in 2019 and 2020. Officials said they were particularly interested in hearing from citizen scientists in Whatcom, Skagit, Island, San Juan, Jefferson and Clallam counties.

Asian giant hornet
A dead Asian giant hornet. U.S. scientists and federal authorities are gearing up for a new season of the insects in the coming months. ELAINE THOMPSON/POOL/AFP/Getty Images