You may have heard of “murder hornets,” or Asian giant hornets, which made international headlines after a small number were spotted in the Pacific Northwest in 2019 and 2020. They are currently confined to the far northwestern corner of Washington State, in part due to a targeted campaign to find them and eradicate their nests.
Even so, the discovery of these aggressive, two-inch-long insects known for decimating entire honeybee colonies led to concern throughout the United States, with many people misidentifying local wasps as murder hornets. What many people are actually seeing, according to entomologist Justin Schmidt at the University of Arizona, is a harmless native wasp with an equally fierce name: the cicada killer.
The name is fitting. Females are large, measuring up to an inch and a half in length, and they prey exclusively upon cicadas, which they find, grapple with, and inject with venom. This paralyzes the cicada, which the wasps then carry back in flight to their subterranean lairs. Since mid-July, cicada killers have been emerging from their underground burrows and buzzing around people’s yards.
Cicada killers go after the more dependable seasonal cicadas, not the periodical species, such as Brood X, which descended upon the eastern U.S. in May. Though there are four species of cicada killer in North America, all of them are similar in appearance and behavior.
Despite their large size and bright yellow and brown coloring, cicada killers are harmless to humans—they’re “gentle giants of the wasp world,” Schmidt says. Male cicada killers don’t sting, and, unlike Asian giant hornets, female cicada killers avoid people and rarely deploy their stingers. You’d actually have to handle them to ever be in danger, says Schmidt, who has received thousands of stings and in the process created the Schmidt Sting Pain Index.
When it does happen, a female cicada killer’s sting is very mild, almost negligible—it feels like a mere pinprick, and hurts less than the sting of a sweat bee, says Joe Coelho, a physiological ecologist at Quincy University in Illinois who studies the predators. For comparison, the Asian giant hornet’s sting hurts much more, akin to being “stabbed by a red-hot needle,” researcher Shunichi Makino said in a previous interview.
But even though cicada killers are a “big, scary-looking insect, they have nothing. They can’t afford to sting you because they call their own bluff. It’s amazing how afraid people are of them based on appearance alone,” Coelho says.
Anatomy of a hunt
To find well-camouflaged cicadas, female cicada killers search trees using their large eyes and keen vision. When they attack, they inject the insects with a cocktail of fast-acting venom, irreversibly preventing the cicada from moving. How it works, nobody knows, Coelho says. But it turns them into zombies of sorts, all the better to be fed upon by the wasps’ young. Research by one of Coelho’s past graduate students showed that envenomated, paralyzed cicadas can actually live longer than normal, healthy cicadas.
But if she’s successful, the female must now carry her heavy quarry back to her nest using her powerful wings, all while holding the cicada with her middle legs. Coelho’s research shows that eastern cicada killers (Sphecius speciosus) actually succeed in hunting and ensconcing cicadas more than 80 percent heavier than them—nearly twice their weight—which should not be physically possible. They do it, Coelho explains, by “cheating” a little: carrying the cicadas up trees or other vertical surfaces and furiously flying toward their hole. This can be repeated multiple times until they reach their home, during which time they drag the cicadas underground.
Back in her subterranean chamber, the female lays an egg on her immobilized prey, which will provide food for the growing larvae. To produce a male offspring, the wasps only need one cicada. But females, which are roughly twice as big as males, require two cicadas to develop properly. Once a chamber within the nest contains one or two cicadas, she seals it off, makes another, and keeps hunting.
In a good year she may create and fill more than a dozen of these chambers; a single wasp may hunt and kill more than 30 cicadas after emerging around mid-July and dying about six weeks later.
Once the larval wasps feed on the cicadas, they hang out underground over winter, then emerge after finally developing into full adults in mid-summer the next year, starting the cycle over again.
Most cicada killer sightings are actually males, which surface from their burrows shortly before females each summer, explains John Alcock, an entomologist at Arizona State University. When the females appear, the males viciously compete to mate with one, each of which only breeds once. Unlike females, males are aggressive, and will chase and buzz at animals that approach their territory, including humans. They even go so far as pretending to sting, a behavior called pseudo-stinging.
The males “are very loud and obvious, and people get freaked out,” Coelho says—especially since the insects seem to prefer disturbed habitats and areas with open ground and low vegetation, such as suburban lawns.
Yet the species is a crucial predator in the ecosystem, helping keep populations of cicadas in check. Their incredible hunting abilities also provide a fascinating natural history lesson for children, Schmidt says. (Learn more: 'Murder hornet' mania highlights dangers of fearing insects and spiders.)
“So if you do have some cicada killers in your yard,” Alcock says, “rejoice rather than run for the wasp spray.”