Many memorable things happened in 2020: Australian bushfires, COVID-19 pandemic, teleworking, wearing masks, the race to create a vaccine, a presidential election, and … murder hornets.
Already fearful of catching an unseen virus, people began to fear for their lives from possibly being stung by a 2-inch hornet! Every large insect with wings was fearfully looked upon and the question was asked, “Is this a murder hornet?”
“Murder hornets” are also known as Asian giant hornets (Vespa mandarinia,) native to northern India through East Asia. In August 2019, the hornet was first reported in the Vancouver Island area and later detected in Washington state, and found again in May 2020.
Entomologists quickly began an eradication program to stop this species from spreading, and although they have been successful in stopping the spread of the hornet, they have been unable to stop the fear which rapidly spread across the nation. People feared the hornet was now in their state.
Anxious callers phoned their County Extension Agents with reports of the “killer hornets” in their backyards.
So why all the fuss? Do they attack humans?
The Asian giant hornet usually does not attack humans unless they feel threatened. They will sting to defend their nest or defend a beehive they are attacking. Their stinger is formidable, being much longer than any of our native bees or wasps in the United States and can easily pierce through the protective clothing of a beekeeper. The hornet’s venom is also more toxic. And like other wasps and hornets, they can sting multiple times, unlike a honeybee which has a barbed stinger they leave behind after stinging a victim. For people with an allergic reaction to bee stings, a sting from this hornet could cripple or kill.
Mass hornet attacks are very rare. About 50 people die in Japan every year due to Asian giant hornet stings. In comparison, a total of 89 people in the United States died in 2017 due to a bee, wasp or hornet sting.
To understand the real threat posed by the Asian giant hornet, the life cycle and biology needs to be understood. Beginning in spring, a fertilized queen emerges from the winter and begins to feed on sap, developing her ovaries, and looking for a nesting site. Most nests are typically located in underground cavities made by another animal, such as a rodent.
Once the queen selects a nesting site, she enters a solitary phase in the summer and begins to build the nest, forages, lays eggs, and cares for the young. When the nest numbers around 40 workers, the queen becomes homebound, allowing the workers to assume all duties outside of the nest. By late summer or early fall, the colony begins to produce males and next year’s queens. These new reproductives, as they are called, do not forage and so the workers must obtain food with high protein to help them develop. In the fall, the developed males leave the nest before the females, perching at the entrance nest waiting to mate with the new queens as they emerge from the nest about one month later. (Yes, you read that correctly: brothers mating with sisters.) These new queens must mate before winter occurs because there will be no males available the following spring when the females emerge. During winter, the fertilized female (the new queen) will overwinter in a sheltered spot in soil, rotting wood, or piles of straw. The cycle begins again the next spring when the new queen emerges from overwintering and seeks a nesting site.
It is the little honeybee (and many species of native bees) that need to fear the possibility of Asian giant hornets becoming established in the United States. (And if you are a beekeeper, you, too, are naturally worried about this becoming a reality.) Around 50 Asian giant hornets can wipe out an average-sized honeybee colony of 30,000 workers in less than two hours. These murderers expel a special pheromone onto the hive signaling other hornets this colony is the target. The giant hornets overwhelm the honeybee guards, which are a fraction of the hornet’s size, and enter the colony, beheading honeybee workers as they make their way through the hive. They continue marauding through the hive until the hornets eventually find the queen and swiftly slay her, too. Then the hornets seek out the nursery and steal the unprotected honeybee larvae and pupae to take back to feed the developing reproductives. Honeybee larvae and pupae are an excellent source of protein for the future queens.
Did you know about one in three bites of food comes from crops that depend on animals for pollination and bees are one of the most important pollinator groups? Many of the fruits, nuts, and vegetables pollinated by bees are very nutritious, so losing pollinators means less healthy food for us. The real danger of the Asian giant hornet becoming established in the United States is not so much as stinging and killing humans but wiping out honeybees and other native bees, reducing the number of our dwindling pollinators.
You may be wondering how soon will the Asian giant hornet reach Louisiana? Based on the average rate of spread of a related species in Europe, scientists looked at geography, habitat, and wing speed to help determine the potential spread of the Asian giant hornet in the United States over the next 20 years. The good news is that if the Asian giant hornet has not been completely eradicated on the West Coast, it will not likely make it across the western mountain ranges, without human help that is. Let us hope the careful monitoring and trapping process established by the Washington state entomologists eradicate this awful pest.
If mankind helps the Asian giant hornet to rapidly cross the United States from the West Coast, it will help to know some of our common insect species you might confuse for the murder hornet (see illustration on page 13). Keep in mind the sheer size of this giant hornet — almost 2 inches long. We do not have many insects that come close to that size, but there are several in the South that have similar coloration. The USDA Animal and Plant Health Inspection Service has provided information on Asian giant hornet lookalikes (https://www.aphis.usda.gov/aphis/ourfocus/planthealth/plant-pest-and-disease-programs/honey-bees/agh/asian-giant-hornet), such as the Eastern cicada killer, common species of yellowjackets, other hornets, sawflies, paper wasps, and bees. The Eastern cicada killer is the closest common insect in size to the giant hornet. All other lookalikes are significantly smaller.
Maybe being cooped up inside our homes for weeks and months, isolating, social distancing and wearing masks made our imaginations run wild when the “murder hornet” discovery was shared. In a typical year, it would have simply been called the Asian giant hornet.
(Stacy Blomquist is a Public Affairs Specialist for the USDA Forest Service, Kisatchie National Forest, and a backyard beekeeper.)