By Jennifer Berry, Keith Delaplane and Heather N. Kolich
A flurry of recent press coverage has created a surge of interest in the Asian giant hornet, Vespa mandarinia. The coverage is not traced to any recent or local event. The insect was found late last year in Vancouver Island (Canada) and in Washington state. So far, this invasive insect is not present in Georgia, nor in any state east of the Mississippi River.
The photographs and specimens clients are sending to the Forsyth County Extension office are all European hornets (Vespa crabro), which have been in the U.S. since the 1800s.
European hornets, also called giant hornets, can damage plants by stripping bark to build their paper nests. They’re attracted to lights and may beat on windows, but they’re not aggressive.
The easiest way to tell the difference between European and Asian giant hornets is to look at the pattern on the abdomen. While both have stripes, European hornet stripes feature two “paint drips” on either side of the midpoint.
The Asian giant hornet is a “true” hornet and the world’s largest, ranging in size from 1.5 to slightly over 2 inches long (38-50mm).
Asian giant hornets aren’t aggressive towards humans, livestock, or pets, but will sting if provoked. The stinger is nearly ¼-inch long, and stings are extremely painful.
The venom is not the most lethal among bees and wasps, but because the insect is so large, the amount of venom delivered in a sting is more than the dose of other stinging insects Americans typically encounter.
Human sting deaths are low (30-50 annually in Japan) and biased toward individuals who are prone to anaphylactic reactions or to individuals who receive numerous stings. One or a few stings from an Asian giant hornet should not be life-threatening to an average individual.
The major concern is the devastation this giant killer can inflict on honey bee colonies. Just a few Asian giant hornets can annihilate 30,000 bees within hours.
An Asian giant hornet attack on a honey bee colony unfolds in three phases.
1. The hunting phase: Individual hornets capture bees at the entrance of the colony, cut off their heads, and form a “meat ball” from the thorax. Hornets then carry the protein-rich meatball back to their nest to feed their young.
2. The slaughter phase: Hornets mark a colony with a pheromone to recruit their sisters to the site. Then numerous hornets descend upon the colony, kill all of the workers by ripping their heads off, and dump their bodies onto the ground below.
3. The occupation phase: Once the bees are dead, hornets take over the hive and guard the entrance. They collect pupae and larvae and return to their own nest to feed their carnivorous young.
The visible key to an Asian giant hornet attack is a pile of decapitated or ripped apart bees on the ground outside the hive. A a pile of intact dead bees could be the result of pesticides, starvation, or something else.
Asian honey bees have a defensive response to Asian hornet attacks. They “cook” hornets to death by grabbing and surrounding an invading hornet, and then raising their thoracic temperatures to a level that’s lethal to wasps but tolerable to bees. Unfortunately, American honey bees are of European descent and don’t have this behavior.
Other wasps and hornets already residents in our state that may be confused with the Asian giant hornet are:
• Cicada killers, Sphecius speciosus, size range 0.6-2 inches long (15-50mm)
• European hornets, Vespa crabro, size range 1-1.4 inches (25-35mm)
• Southern yellowjackets, Vespula squamosa, size range 0.5 inches (12mm)
• Bald-faced hornets, Dolichovespula maculata, size range 0.75 inches (19mm)
At this time, we need to be vigilant but not over-reactive in watching for Asian giant hornets. If you think you have seen an Asian giant hornet, found evidence of an attack, or have a specimen, please contact your local county Extension agent immediately.
Jennifer Berry and Keith Delaplane are with the University of Georgia Department of Entomology, and Heather N. Kolich is the University of Georgia Agriculture and Natural Resources Extension Agent for Forsyth County.