The cicada killer wasp is a one-bug specialist.
When the whirring, whining drone of dog-day cicadas vibrates through the haze of Virginia’s late-summer heat, it also marks the season when another species arises. A determined hunter, the cicada killer wasp prowls the air with a single prey in mind—its victims fated for an unpleasant end.
Cicada killers (Sphecius speciosus) are Virginia’s largest wasp; adult females are about two inches long and equipped with a nasty-looking stinger at the business end of their abdomens. Yet despite their intimidating size, they pose no real danger to humans, says Dr. Kal Ivanov, associate curator for invertebrates at the Virginia Museum of Natural History in Martinsville.
“They don’t sting to defend their nest, like paper wasps or yellow jackets,” Ivanov says. If you step on one or catch one, you might get stung, he says, but really they’re not interested in you.
For cicadas, though, it’s a different story.
Adult cicada killers emerge from their underground burrows in the summer months, when annual cicadas (Neotibicen canicularis) are abundant, says Ivanov. The males arrive above-ground first and fiercely defend their territory against other males. They’ll also put on an aggressive show towards any human or beast that might stumble into their turf, but it’s all sound and fury—the males have no stinger whatsoever.
When the females emerge, the males go about what is literally their life’s only purpose: they mate and die soon after.
For the female, though, the work is just beginning. For her offspring-to-be, she must excavate an underground tunnel lined with small oval chambers. She digs with her front legs and pushes the soil behind her with her back legs, moving as much as a half-gallon of dirt per tunnel. She might dig as many as four tunnels, which can extend a foot or more underground. In the right setting—with soft, well-drained soil, preferably near trees loaded with cicadas—you might find hundreds of these tunnels, Ivanov says.
Once she’s dug a home for her progeny, it’s time to fill the pantry. So, off she flies in search of cicadas. It was once believed that the wasps hunted by sound. But in fact their preferred target are female cicadas, which don’t “sing,” so it appears the cicada killer wasps find their prey by sight instead.
Once the wasp has a cicada in sight, “she will land, grab it, and sting it near the front of the body and paralyze it,” Ivanov explains. But then she has to haul it back to the tunnel. A cicada is not what you’d call a delicate morsel. “The cicada is about twice the size of the wasp and it is very heavy,” says Ivanov. The wasp clasps the paralyzed cicada belly-up and, in something of a downward glide, “will try to use gravity to fly to the tunnel,” says Ivanov. “If she miscalculates and lands in the grass near the tunnel, she may abandon the prey and hunt another.”
But when she successfully gets the cicada to the hole, she’ll drag it into one of the prepared chambers. Sometimes she’ll stuff in one or two more, before laying a single egg in the chamber, sealing it, and flying off to repeat the process for the next chamber.
Now comes the grim part. The egg will hatch within 48 hours, Ivanov says, and “then the larva starts feeding on the paralyzed cicada while it is still alive.” Chowing through that hapless living meal, the larvae grow quickly in their individual chambers, completing larval development in just a few weeks before spinning a cocoon inside the chamber and pupating until the following May or June.
“Pretty much 90 percent of their life is spent underground,” Ivanov says.
Come the following summer, the new generation of wasps dig straight up to the surface to emerge once again, their life-cycle tied with another year’s cicadas.
If you should spot some of these big wasps in the dog days of summer, Ivanov points out that no, they’re definitely not “murder hornets,” the headline-grabbing Asian giant hornets which (may it remain so) have not been found in Virginia.
Cicada killers, he says, serve as “a natural way of keeping the cicada population in check.”
This article was originally published in our August 2022 issue.
