Questions and Answers about the Asian Giant Hornet
Updated: Jun 18
By Riley Waytes, NBSBC Director
A collection box of Vespa mandarinia. Image from the
Smithsonian National Museum of Natural History.
A recent article on Asian Giant Hornets in the New York Times (‘‘Murder Hornets’ in the U.S.: The Rush to Stop the Asian Giant Hornet’) has prompted some questions and concerns about Asian giant hornets in British Columbia and their impacts on both humans and bees. We hope that we can put some of those concerns to rest with some additional information.
What was reported in the article?
In 2019 an Asian giant hornet was seen in White Rock, BC and a nest of Asian giant hornets (Vespula mandarinia) was discovered and subsequently removed in Nanaimo
Also in 2019, two Asian giant hornets were found in the northwest part of Washington state
Finally, last year a hive of honey bees in Blaine, WA was killed in a manner reminiscent of how Asian giant hornets might attack a honey bee hive, although there was no direct evidence showing that Asian giant hornets were responsible
Genetic testing suggested that the hornets in Nanaimo and the hornets found in Blain were not connected.
What else do we know?
Records at the Royal BC Museum and the Spencer Entomological Collection suggest that 2019 was not the first year that Asian giant hornets (Vespa species) have been found in British Columbia
However, 2019 was the first year that an established Asian giant hornet nest has been found
The hornets in Nanaimo were Vespa mandarinia; a single specimen of Vespa soror was collected in the lower mainland in spring of 2019
The Asian giant hornet nest in Nanaimo was thought to be completely eradicated. The entire colony and brood combs were destroyed.
What is an Asian giant hornet?
While individuals of several species have been found in BC, Vespa mandarinia is the first species known to have established a nest
This species originates from Asia
They are a notably large insect, from around 3.5 cm in length for workers and up to 5 cm in length for queens
Their colouration includes a large orange head, predominately black thorax, and an orange- and black-striped abdomen
They typically nest in the ground or near the ground (e.g., in hollowed-out logs).
Why are Asian giant hornets considered to be a problem?
Asian giant hornets prey on other insects and are considered to be a natural enemy of honey bees. While honey bees native to Asia (including Apis cerana japonica) have developed defenses against Asian giant hornets, European honey bees (including the western honey bee, Apis mellifera) have not
Asian giant hornets do not target humans or other mammals. However, they will sting if provoked or threatened
Like other introduced species, their presence can negatively affect native species and ecosystem functioning.
Do Asian giant hornets kill native bees?
Asian giant hornets consume adult and larval insects, which is not limited to honey bees. They would likely opportunistically consume native bees. However, given the differences in ecology and life history traits of native bees compared to honey bees (comparatively smaller colonies for social bees like bumble bees, and minimal adult and larval bee presence in solitary bee nests), the interaction will likely be different than that of Asian giant hornets and honey bees.
What native Hymenoptera could be mistaken for Asian giant hornets?
Hornets are defined as large eusocial wasps in the genus Vespa. There are no native Vespa species to Canada, although the European hornet (Vespa crabro) has been introduced in the eastern part of the United States and Canada
Larger, social species of wasps including bald-faced hornets (a species of yellowjacket wasp in the genus Dolichovespula), yellowjackets (Vespula species), and paper wasps (Polistes species) may be mistaken for hornets. These wasps are typically black-and-yellow or black-and-white striped and are smaller than Asian giant hornets
Other non-wasp Hymenopterans include the elm sawfly (Cimbex americana), a large species of sawfly that (like other sawflies) does not possess a stinger
Bumble bees are large-bodied, fuzzy Hymenopterans. While very dissimilar in appearance to Asian giant hornets, their large size (especially that of queens) could possibly make people unfamiliar with bee identification mistake them as hornets
Why do native wasps matter?
Wasps are an important and often underappreciated source of pest control. They are an essential part of a healthy ecosystem
What can we do to combat Asian giant hornets and help native wasps?
Currently the concern about Asian giant hornets is largely precautionary. However, any sightings should be reported. Should you encounter one, contact the Invasive Species Council of BC (see link below for more details)
Becoming familiar with how to identify Asian giant hornets is helpful to ensure you have the correct species. Check out the first link below to learn more about how to identify them
Learn more about native species of Hymenopterans (including bees!). This will help you recognize invasive intruders, as well as to give you a better understanding of the insects that we share our world with.
Please do not unnecessarily kill native Hymenopterans
Update (May 31, 2020):
As of this date, there have been two sightings of the Asian giant hornet in the Pacific Northwest in 2020: one in Langley, BC and one in Custer, WA. Both of the hornets were collected and had their identities confirmed by local officials
We continue to encourage those concerned about the potential presence of the Asian giant hornet to learn how to recognize Asian giant hornets, as well as to become familiar with native species of wasps and other Hymenopterans. BC residents should report Asian giant hornet sightings to the Invasive Species Council of BC
For more information about the recent Asian giant hornet encounters (and to see a size comparison between the Asian giant hornet and the native bald-faced hornet), see the following article in the Smithsonian Magazine:
The BC Ministry of Agriculture has put out a pest alert on the Asian giant hornet, including photos of the hornet as well as some look-alike species: https://www2.gov.bc.ca/assets/gov/farming-natural-resources-and-industry/agriculture-and-seafood/animal-and-crops/plant-health/pest_alert_asian_hornet.pdf
A BC Government bulletin on the Asian giant hornet from March 2020: https://news.gov.bc.ca/releases/2020AGRI0013-000517
The December 2019 issue (volume 29, issue 2) of the Entomological Society of BC’s newsletter Boreus contains an article about the Asian giant hornet nest in Nanaimo (‘Scientific Note-- Alien Invasion Thwarted: nest of Asian Giant Hornet, Vespa mandarinia extirpated in Nanaimo, BC’): http://entsocbc.ca/publications/boreus-newsletter/
Resources like E-Fauna BC and BugGuide offer photos and information about insects that can be found in British Columbia and elsewhere. These are useful tools for learning more about native species:
Thank you to Claudia Copley from the Royal BC Museum for providing information about Asian giant hornets in British Columbia.
As a final note, here are some friendly native Hymenopterans as a reminder that they aren’t all scary:
A scoliid wasp (from Ontario) delighting in a flower. Photo by Sarah Johnson.
A cimbicid sawfly (Trichiosoma sp.) relaxing on a leaf. Photo by Sarah Johnson.
A square-headed wasp (Ectemnius cephalotes) perched on a leaf. Photo by Chanta Ly.
A yellowjacket joining a bumble bee on a flower. Photo by Chanta Ly.