Asian Giant Hornet in the Northwest U.S.

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The Asian Giant Hornet (AGH) (Vespa mandarinia) has not been found in Ohio.  In fact, it has not been confirmed anywhere in the U.S. beyond the extreme northwest corner of Washington State.


Previous BYGL Alerts noted that AGH had never officially been confirmed in North America.  That changed September 18, 2019, when an AGH nest was found and destroyed in the town of Nanaimo on Vancouver Island, British Columbia. The identity of the hornets was confirmed by Canadian entomologists and international experts contacted by the British Columbia Ministry of Agriculture.  It was the first confirmed report of AGH being found in North America.


In December 2019, the Washington State Department of Agriculture (WSDA) confirmed that a dead hornet collected by a resident in Blaine, WA, was AGH.  Blaine is on the U.S. – Canadian border almost directly across the Strait of Georgia from Nanaimo, B.C.  It was the first confirmation of an AGH adult being found in the U.S.; however, no nests were discovered.  


Subsequently, WSDA was notified of three more potential AGH sightings near Blaine and in Bellingham, WA, which is located around 10 miles south.  Although specimens were not confirmed, two of the sightings were made by experienced beekeepers.  The WSDA will be deploying detection traps this season in the Blaine and Bellingham areas.


You can read more details about the confirmations by following the hotlinks listed under "The Confirmations" below.



The Hornet

AGH is the world's largest hornet with a body length of 1.5 – 2" and a wingspan from 1.5 – 3".  Two of its most notable features are its large orange or orangish-yellow head and distinct orangish-yellow and reddish-brown bands on its abdomen.


Asian Giant Hornet


AGH produce annual underground nests often taking advantage of cavities created by burrowing rodents and other animals.  Their seasonal development matches that of our own North American yellowjackets (Vespula spp.) and bald-faced hornets (Dolichovespula maculata) with the nests only being used for one season. 


Despite the social media hype and dubious web postings, experts consistently note that AGH is not particularly hostile towards humans, pets, and large animals.  As with our native yellowjackets and bald-faced hornets, AGH generally goes about its business unless its nest is threatened.  Of course, swatting at an AGH may also elicit a painful introduction to its 1/4" stinger.


However, AGH is a predator of other insects and extremely aggressive towards European honey bees (Apis mellifera).  AGH will mass-attack honey bee hives and quickly dispatch the workers primarily by clipping off their heads.  They then rip out the honey bee larvae and pupae, fly back to their underground nests and feed the mellifera meat morsels to their young.


Asian Giant Hornet


This discriminating taste for honey bees is a two-edged sword.  On one hand, AGH can be highly destructive by quickly devastating honey bee hives.  On the other hand, their strong preference for honey bee meat means beehives are highly effective in revealing undetected AGH populations.  For this reason, beekeepers will most likely be the first to observe AGH in an area where this non-native has established new outposts.


PLEASE NOTE:  A possible AGH discovery is meaningless unless it's officially confirmed by a regulatory agency such as the Ohio Department of Agriculture (ODA) or the USDA Animal and Plant Health Inspection Service (USDA APHIS).  A specimen is required for an official confirmation.  Thus, it's very important to collect a specimen (dead specimens kept frozen) and contact the ODA if you live in Ohio.


While photographs can't serve as official confirmations, efforts should still be made to take pictures because they help to separate AGH from various look-a-likes.  Likewise, "sightings" carry no official recognition unless backed by a photograph or more importantly, a specimen.




The two insects most commonly mistaken for AGH are European Hornets (V. crabro) and our native Cicada Killer Wasps (Sphecius speciosus).  Cicada killers are the largest native wasp found in Ohio.  They appear with the arrival of their namesake food item, Annual Dog-Day Cicadas (Tibicen spp.; family Cicadidae), and disappear once annual cicada activity concludes for the season.


Cicada Killer


Dog-Day Cicada


European hornets were first found in the U.S. in New York State around 1840.  Since that time, the hornets have spread to most states east of the Mississippi and a few states to the west.  European hornets are impressively large, measuring 1 - 1 1/4" in length.  Their black and yellow markings on their abdomen make them look like yellowjackets on steroids; however, their head and thorax have distinct chestnut-colored markings.  Yellowjackets have black and yellow markings on the head and thorax.


European Hornet






Technically, European hornets are now the only "true hornet" found in Ohio.  Taxonomically, our native bald-faced hornets are not hornets; they are grouped with yellowjackets which is why they are in the same genus as native Aerial Yellowjackets (D. arenaria).


Bald-Face Hornet


Unlike our native yellowjackets and wasps, European hornets can cause noticeable girdling damage to twigs and branches of trees and shrubs by stripping bark to the white wood.  It is speculated that the hornets are extracting sugar from the phloem tissue.  Although the damage may be noticeable, it's seldom significant enough to cause concern.


European Hornet


European hornets construct paper nests that may look similar to the bald-faced hornet nests.  However, they are most often found in hollow trees and sometimes in the walls of homes.  They do not produce underground nests.


Normally, European hornets overwinter just like our native bald-faced hornets, paper wasps, and yellowjackets with only the queens that are produced this season surviving the winter.  The new queens leave the nests to seek protected overwintering sites; old nests are not re-used.  However, occasionally the entire European hornet nest will survive the winter if they are sufficiently protected.  Indeed, although it is rare, nests in Ohio have been observed surviving through three winters. 


European Hornet


European Hornet


European hornets are reputed to be highly aggressive and their large size does make them look pretty scary.  However, during past encounters with this hornet, I was able to take close-up images and move branches with hornets on them without being stung or even charged by the hornets.  Still, landscapers should be cautious around these large stinging insects.  Like wasps and yellowjackets, they are capable of stinging repeatedly. 


The European hornets may also fly at night and are attracted to porch lights or lights shining through windows.  They have been known to repeatedly charge windows at night inducing panic in homeowners.



The Confirmations

The following websites document the AGH discoveries in Washington State as well as British Columbian and also provide additional helpful information:


WSDA Pest Alert: Asian giant hornet


Washington State University Extension, Additional Information on Asian Giant Hornet


WSDA Asian Giant Hornet Reporting in Washington State


British Columbia Ministry of Agriculture, Three Asian giant hornets found in Nanaimo


British Columbia Ministry of Agriculture, Asian giant hornet nest eradicated in Nanaimo


British Columbia Ministry of Agriculture, Pest Alert: Asian Giant Hornet