Asian giant hornets, Vespa mandarinia, are large insects from East Asia, sometimes known as “murder hornets.” Their presence in the United States has drawn public attention and concern.
Presence in the United States
Asian giant hornets were first detected in the United States in December 2019, with two reports confirmed near Blaine, Washington, close to the Canadian border. Subsequent eradication efforts focused primarily on Whatcom County, Washington. In October 2020, entomologists located and eradicated the first live nest in the U.S. in Blaine. Additional nests were found and destroyed in Washington state during 2021.
Extensive surveillance, including trapping and tracking individual hornets, was crucial for preventing establishment. After three consecutive years without any confirmed detections, the Washington State Department of Agriculture (WSDA) and the United States Department of Agriculture (USDA) officially declared the Asian giant hornet eradicated from Washington and the entire United States in December 2024. Despite this declaration, the WSDA plans to continue precautionary trapping in 2025 to ensure the hornets do not re-emerge.
How to Identify Them
Asian giant hornets are the world’s largest hornets, with queens reaching up to 2 inches in length and workers typically measuring 1.5 to 2 inches, boasting a wingspan of about 3 inches. A key identifying feature is their distinctly large, orange or yellowish head, which is often wider than their shoulders. Their bodies have a dark brown or black thorax and an abdomen with smooth, dark orange or brown stripes alternating with black bands.
Distinguishing them from native insects is important to avoid misidentification. Cicada killer wasps, which can be up to 1.5 inches long, have a narrower, dark head that matches their thorax and their yellow abdominal stripes are typically uneven or jagged. The European hornet, Vespa crabro, the only other true hornet established in parts of the eastern U.S., is smaller, measuring 1 to 1.5 inches, and has a mostly pale yellow abdomen with black stripes, lacking the prominent orange head of the Asian giant hornet.
Threats They Pose
Asian giant hornets are considered a threat primarily due to their predatory impact on honey bee populations and other native pollinators. They can attack honey bee colonies, entering what is known as a “slaughter phase” where they decapitate adult bees. This aggressive behavior allows a small group of hornets to destroy an entire honey bee hive within a few hours.
After eliminating the adult bees, the hornets then occupy the hive to harvest the bee larvae and pupae, which they carry back to their own nests to feed their young. While their sting is potent and can be painful, potentially causing severe reactions or being lethal in cases of multiple stings or allergies, Asian giant hornets are not inherently aggressive towards humans unless provoked or their nest is disturbed.
Reporting Sightings and Control Efforts
Public reporting plays a significant role in monitoring invasive species like the Asian giant hornet. If an individual suspects a sighting, they should contact their state’s department of agriculture. Providing photographs, the location and date of the sighting, and a description of the insect or any observed damage is helpful for confirmation.
Control efforts by authorities involve various methods, including setting up traps baited with substances like orange juice and rice wine to capture hornets. Once live hornets are caught, radio tags can be attached to them to track their flight paths and locate their hidden underground nests. Upon discovery, these nests are typically eradicated through methods such as vacuuming hornets from tree cavities and then treating the nest with foam and carbon dioxide.