By now many Americans reading or watching the news have heard about “murder hornets” from Asia invading the American landscape. It is true that in many parts of East Asia, Japan in particular, a large hornet lives and feasts upon honey bees and other insects. This is the Asian giant hornet (AGH), or Vespa mandarinia, which is a relative of the European hornet (Vespa crabro) that we typically see in North America. The European hornet is an import to America that has naturalized, or become established here as if it was native. The Asian giant hornet has just arrived on North America’s west coast, by unknown means. Residents and beekeepers alike are hoping it doesn’t become naturalized in America.
The Asian giant hornet is the world’s largest, measuring 1.6 to 2 inches long, with a particularly large yellow-orange head. It is a social insect, living in colonies built in soil burrows dug by rodents and other animals. While people may not often see Asian giant hornets, beekeepers will definitely notice their decimated colonies of honey bees. It takes a handful of Asian giant hornets to slaughter an entire honey bee colony, after which hornets feed on the larvae, pupae and honey inside the hive. Japanese honey bees, which are a different species of honey bee than what we raise in North America, can fight back against AGH by surrounding and super-heating the wasp in a ball of bee bodies. Our European honey bees also have this defense behavior, but it is unknown how they would fare with this kind of predation. If AGH becomes established in the US and Canada, the greatest threat will be to beekeepers and their honey bees.
The hazard to humans posed by the stings of AGH is real. The venom is toxic and with their long stingers, AGH can inject more venom into a wound than most other stinging insects. Stings lead to intense pain and swelling, and can induce renal failure and anaphylaxis. Multiple stings can be deadly. But, these hornets do not come after humans and left alone, they mind their own business. The efforts to eradicate AGH from Washington State and Canada will be a priority aimed at avoiding their permanent establishment in the US. Unlike claims in some media outlets, it will likely take many years for this wasp to spread across the country on its own if we fail to eradicate it. Beekeepers will be on the front lines of detection.
*** June 2020 UPDATE – A dead queen Asian giant hornet was discovered this spring on a road near Custer, WA, which is close to the western Canada border. This indicates that queens produced by at least one colony in the Fall of 2019 overwintered and emerged. To date (6/3/20) no other detections have been reported.
*** August 2020 UPDATE
In 2020, both Washington and Canada have had new confirmed sightings of the Asian giant hornet. In addition to earlier reports, one queen, one worker and another unspecified wasp have been reported. This means we are not done with Asian giant hornets yet! Finding a queen wasp in May suggests that they survived winter in the Pacific Northwest. As colonies of these and related wasps grow in size through the end of summer, there may be more findings to report. Stay Tuned!
There are several species of wasps in the US that are very commonly confused with AGH and often killed unnecessarily:
Cicada Killer – Sphecius speciosus – a large, native, solitary wasp, does not readily sting or act aggressive toward humans, hunts cicadas, exclusively, digs burrows in the soil where eggs are laid upon the body of paralyzed cicadas. Common in suburban areas.
European Hornet – Vespa crabro – an introduced social species, colonies started by a single queen, colony builds and expands a tan paper ball nest typically in hollow trees and abandoned barns and structures. More common in rural areas. Not aggressive unless harassed.
Baldfaced hornet – Dolichovespula maculata – Large black-and-white wasp, not a true hornet, colonies started by a single queen, nest is a grey paper ball usually high in trees or on the side of structures. Not aggressive unless harassed.
Yellowjackets (many species) – Vespula sp. – Small yellow-and-black wasps that nest in large colonies in soil and other man-made cavities. Can be aggressive, especially in early fall.
Paper wasps – Polistes sp. – Slightly longer than yellowjackets, various colors, long legs, umbrella comb nest with a few to a few dozen wasps. Not aggressive unless harassed.
The Bottom Line: A few Asian giant hornets were discovered in Washington State in 2019. The greatest threat is to honey bees and beekeepers. Efforts to eradicate this wasp are underway. New York does not have Asian giant wasps and hopefully won’t anytime soon.
Residents of the west coast should keep an eye out for Asian giant hornets and residents of Washington State are strongly encouraged to submit reports of sightings to the Washington State Department of Agriculture. If you live in New York and have questions about wasps or any stinging insects, you can contact NYSIPM or your local Cornell Cooperative Extension office for advice or to submit samples for identification.