Are Murder Hornets in the US? The Northern Giant Hornet Story

Are there murder hornets in the US today?

The northern giant hornet (Vespa mandarinia), nicknamed the murder hornet, is not known to live anywhere in the United States. The last confirmed detections in North America were in 2021. Washington’s standard for declaring an invasive insect gone is three consecutive years without a confirmed find, and that threshold was reached at the end of the 2024 season. On December 18, 2024, the Washington State Department of Agriculture (WSDA) and the US Department of Agriculture (USDA) announced that the hornet had been eradicated.

That does not mean it can never return. In October 2024 a possible sighting was reported in Kitsap County, Washington, but no specimen was collected and it could not be confirmed. Officials still ask people in the Pacific Northwest to report any very large hornets, because a new introduction could arrive the same way the first ones did.

How did northern giant hornets get to North America?

Nobody knows exactly. The hornet is native to East, Southeast and South Asia, and the most likely explanation is that mated queens, which hibernate in sheltered spots over winter, were carried across the Pacific hidden in cargo.

Genetic tests published in 2020 showed that the hornets in British Columbia and those in Washington came from different maternal lines, one matching populations in Japan and the other South Korea. In other words, there were at least two separate introductions within about 80 km (50 mi) of each other in a short period. A dead male found near Marysville, Snohomish County, in 2021 had a different color form and DNA again, pointing to a third source, although it had probably died a year or more earlier.

Timeline of the murder hornet hunt

The October 2020 nest was in a hollow tree about 2.5 m (8 ft) above the ground, unusual for a species that normally nests underground. Later analysis found about 500 hornets in all stages inside, including nearly 200 developing queens. Had those queens mated and hibernated, the population could have multiplied the next year.

How scientists found the nests

Finding a giant hornet nest is hard, because most are hidden underground and workers can forage 1–2 km (0.6–1.2 mi) from home. WSDA staff and volunteer citizen scientists set out bottle traps baited with sweet liquids to catch hornets and map where they were flying.

The breakthrough was radio tracking. Entomologists caught live workers, fitted them with tiny radio tags, released them and followed the signal back to the nest. Crews in thick protective suits then vacuumed the hornets out and removed the nest itself. Some specimens from the nests went to the Smithsonian Institution for research.

Why officials worried so much

Northern giant hornets are not a major danger to people in the open, but they are a serious threat to honey bees. In autumn a few dozen workers can wipe out a hive of western honey bees, which have no effective defense. That made the hornet a risk to beekeeping and to crops that rely on rented hives for pollination.

Studies in 2020 suggested that the cool, wet Pacific Northwest offered suitable climate, and that the hornet could spread north along coastal British Columbia toward southeast Alaska and south into Oregon if it became established. One analysis estimated that control costs could exceed US$100 million a year if it spread across all suitable habitat in North America. Stopping the invasion within about two years of finding the first nest was therefore a notable success.

What people mistook for murder hornets

After the 2020 news reports, insect identification services in the eastern United States were flooded with photos and specimens. None of them turned out to be a northern giant hornet. Most were European hornets, which have lived in the eastern US since the 1800s, eastern cicada killers, southern yellowjackets, or harmless look-alikes such as sawflies, wasp-mimicking flies and even cicadas.

People also tend to overestimate the size of insects they find alarming. Specialists noticed that the look-alikes were routinely estimated at about 1.3 to 1.85 times their real size. The real differences in size are explained in How big are murder hornets?

Is the yellow-legged hornet a murder hornet?

No. In August 2023 a different invader, the yellow-legged hornet (Vespa velutina), was confirmed near Savannah, Georgia, and it has since been the target of an eradication program there. This is the same species that has spread across Europe since about 2004 as the Asian hornet.

The yellow-legged hornet is much smaller than the northern giant hornet, with workers about 20–25 mm (0.8–1 in) long, and it is mostly dark with yellow leg tips. Like its giant cousin it preys on honey bees, so beekeepers take it seriously, but it is not the “murder hornet”.