Asian giant hornets currently not a concern for Pa., eastern North America

June 17, 2020

UNIVERSITY PARK, Pa. — Recent alarming news reports aside, Asian giant hornets — sometimes referred to, hyperbolically, as "murder hornets" — are not an immediate concern in the Northeast, nor are they likely to be for a long time, if ever, according to an entomologist in Penn State's College of Agricultural Sciences.

But Michael Skvarla, assistant research professor of arthropod identification, says the stinging insect, recently discovered in the Pacific Northwest, might cause issues for beekeepers if the hornet, scientifically known as Vespa mandarinia, becomes established and widespread in North America.

"The term 'murder hornets' originally was coined by a few Japanese media outlets several years ago, and a recent New York Times story using that description went viral, causing a bit of panic in the United States," Skvarla said. "In their native range, they commonly are called 'great sparrow bee' in Japan, 'tiger head bee' in China and 'general officer hornet' in Korea."

He explained that even the common name "Asian giant hornet" — its most frequently used moniker in English — could be confusing, because another large species, Vespa velutina, the yellow-legged hornet, is sometimes known as Asian hornet, and Vespa crabro, or European hornet, is sometimes called giant hornet.

Until the Entomological Society of America, which governs the use of common names for insects in the United States, decides on the official designation for V. mandarinia, Skvarla contends that calling it "sparrow wasp" or "sparrow hornet" may be the best way to distinguish this species from others, since those names are similar to a name used in the wasp's native range.

Whatever it's called, V. mandarinia is a source of anxiety, in part, because of its size. Skvarla noted that Asian giant hornet queens are among the largest wasps in the world and can grow to a length of more than 2 inches, with a wingspan of 3 inches.

Asian giant hornet and baldfaced hornet queens

A Vespa mandarinia (Asian giant hornet) queen can grow to more than 2 inches in length. Here, a V. mandarinia queen (right) is compared to a queen of the baldfaced hornet, which is a native species.

IMAGE: Washington State Department of Agriculture

"However, the queens are seen outside the nest only when they are hibernating or in the spring before workers have emerged," he said. "Asian giant hornet workers can grow to 1.5 inches in length and are similar in size to some wasps that occur in Pennsylvania."

Skvarla stressed that Asian giant hornets are not present in Pennsylvania and are not known to occur in North America outside of Washington state and Vancouver Island, British Columbia, where colonies were found and eradicated in the second half of 2019. Additional queens were discovered in the same area in the spring of 2020, and attempts to find and eradicate colonies are ongoing.

Asian giant hornets are strikingly colored, with yellow heads, a black thorax, and yellow-and-black or yellow-and-brown striped abdomens. They typically build their nests underground, usually in abandoned rodent burrows in forests, often in association with pine roots. Nests sometimes are constructed in dead, hollow trunks or roots of trees, but these are never more than 3 to 6 feet above the ground.

Among wasp species found in eastern North America, the one most commonly confused for Asian giant hornets is the European hornet, which is similar in size, shape and color. However, the two species can be distinguished by several features.

For instance, Asian giant hornets' abdomens are banded yellow, black and brown, whereas European hornets' abdomens are black toward the front and yellow toward the rear with rows of black teardrops. Also, European hornets typically build nests inside natural cavities, such as hollow trees and inside the walls of buildings, usually 6 feet or higher above the ground.

Another species sometimes mistaken for the Asian giant hornet is Sphecius speciosus, known as the Eastern cicada killer. But, Skvarla pointed out, cicada killers have terminal abdominal segments that are completely black as opposed to Asian giant hornets' yellow-banded abdomen. In addition, cicada killers lack any yellow on the head.

"It's not clear that Asian giant hornets are 'more deadly' or more likely to induce an allergic reaction than honey bees, yellowjackets and other social wasps."

— Michael Skvarla, Penn State assistant research professor of arthropod identification

Asian giant hornets, like other social wasps, can be defensive when they feel their nest is threatened or when they are defending a food source. Skvarla said stings from this insect, when they do occur, are extremely painful. "However, they don't seek people out just to sting them for no reason like some human-hating guided missile."

Perhaps contributing to V. mandarinia's reputation for "murder" are reports indicating that Asian giant hornets kill about 50 people a year across their entire range — which includes large swaths of eastern Asia — due to sting-induced allergic reactions and, more rarely, multiple organ failure due to a large number of stings.

"This statistic often is alarming for people, but for perspective, an average of 62 Americans are killed every year by bees and wasps for the same reasons," Skvarla said. "From 2000 to 2018 in Japan, where these wasps are most common and abundant, an average of 21 people died per year from all wasp, hornet and bee stings combined, with Asian giant hornets accounting for only a subset of those deaths."

The venom of Asian giant hornets isn't even as lethal, on a per volume basis, as that of some native wasps, according to Skvarla. However, Asian giant hornets are large and deliver a proportionally large volume of venom per sting.

"That being said, it's not clear that Asian giant hornets are 'more deadly' or more likely to induce an allergic reaction than honey bees, yellowjackets and other social wasps," he said, "although there is a forthcoming paper that summarizes what little we know from the medical literature about Asian giant hornet stings."

What is clear is that Asian giant hornets are lethal to the honey bees and other insects upon which they prey. Japanese honey bees, which have co-evolved with Asian giant hornets, have defenses against them, but European honey bees — the species used in commercial honey production — are more vulnerable.

Individual hornets can kill many honey bees, discarding the heads, legs and abdomens and taking the protein-rich thoraxes back to the nest to feed the colony. Groups of three or more hornets can attack and decimate an entire honey bee hive.

"We're not sure how Asian giant hornets might impact honey bees and American beekeepers," Skvarla said. "Beekeepers in Asia have implemented a variety of strategies to combat the hornets. If this species becomes established and widespread in North America, some or all of these strategies potentially could be used here as well."

More information about the Asian giant hornet can be found on the Penn State Extension website.

(Media Contacts)

Last Updated June 22, 2020