Entomologists, agriculture biologists, and beekeepers in Washington state and British Columbia have been working to stop an invasive insect pest, the Asian giant hornet (AGH) ever since it was spotted late last year. Also known as Vespa mandarinia—or, more commonly, murder hornets—the insects have captured imaginations with their size, large stingers, and practice of tearing off the heads of other bees as they wipe out entire hives. Adam Dolezal, professor of entomology and affiliate faculty member of the Carl R. Woese Institute for Genomic Biology, notes that so far the hornets have been observed only in small numbers, and it is unlikely they will spread to Illinois in the near future. He answered questions about the hornets for University of Illinois Extension.
Do we have them in Illinois?
No. Right now, AGHs have only been observed in very small numbers in parts of the Pacific Northwest. Agencies in this region are taking aggressive action to eradicate this early introduction and prevent spread out of the region.
How are they identified?
AGHs bear many similarities to other wasps and hornets that live in Illinois. In Illinois, the most likely wasps to be confused with AGHs are European hornets, bald faced hornets, paper wasps, yellow jackets, and cicada killers. All of these wasps are commonly found in the U.S., are smaller, and have key differences in their appearance.
Without a side-by-side comparison, it can be difficult to use size as a criteria; however AGHs are up to 1.8 inches long — about the length of 2.5 pennies lined up—much larger than these other wasps. European hornets look similar but are usually a maximum of only 1 inch long (about the size of a quarter).
While there is color variation in AGHs, they usually can be identified by their bright orange or yellow head. AGHs build large paper football-shaped nests high in trees, similar to those built by European and bald faced hornets. Paper wasp and yellow jacket nests look very different.
Are they really “murder hornets” or pose a risk to humans?
The popular press has dubbed AGHs as “murder hornets” due to their large size, highly predacious life history, and painful sting that has resulted in some human deaths. While AGH’s can deliver a large volume of venom with a sting, the venom itself does not appear to be more dangerous than that of other wasps. Like most other wasps, they are not overly aggressive towards humans unless their nest is threatened or they are otherwise provoked. Those with confirmed or suspected insect sting allergies should, of course, take caution around these and other wasps and follow guidelines recommended by a medical provider.
One notable challenge with removal of AGH colonies is that their large size and long (~1/4 inch) stinger makes it more likely for them to sting through thick clothing, including bee suits. Like with other hornets, care should be taken to use appropriate personal protective equipment if removal of a wasp nest is undertaken.
Should I remove a wasp nest?
AGHs have not been found in Illinois and are unlikely to occur in the near future. In regions where they have been detected, eradication efforts are underway. Other wasps that are likely to be observed in Illinois usually do not require removal unless they pose direct risks to humans, pets, or livestock.
Most wasps are not aggressive unless provoked and can be safely left alone. Wasps are important insect predators that feed on nuisance and crop pests. While mostly predacious, many wasps also perform some pollination when they collect nectar from flowers. If a wasp nest does need removed, take caution and consult with professional pest removal services, if necessary.
What are the risks for honey bees?
Like all hornets, AGHs are highly predacious, mostly on other insects. AGHs are set apart from other hornets, however, due to their specialization in attacking and feeding on honey bee colonies. As a group, AGHs can devastate a much larger bee colony within the hour; these dramatic attacks on bees have increased their notoriety and influenced their “murder hornet” moniker.
In their native range, the Asian honey bee (Apis cerana) has adaptations to deal with these predators, attacking destroying the hornet scouts and preventing them from leading the entire hornet colony to the hive. The Western honey bee (Apis mellifera), originally native to Europe and now common throughout the world, lacks such adaptations. In areas where AGHs are being reported, beekeepers are recommended to remain vigilant. In Illinois, beekeepers often observe wasps, bees, and flies stealing food from open bee hives, but these are rarely a risk to the colony.