The Cicada Killers Are Coming
Forget the cicadas. Right now, the insects who eat them are about to invade suburbia. These creatures have some of the oddest behaviors you've ever seen.
The invasion of periodical cicadas is over, but a second insect invasion looms. Sphecius speciosus, the Eastern cicada killers, have begun to emerge. And they make the national media hype over the cicadas look rather misplaced. Hunting, warring, patrolling, tunneling, they do more in two months--the length of their adult lives--than periodical cicadas do in 17 years.
With bodies up to two inches in length, huge jaws, and glossy black paintjobs streaked with yellow, they are unmistakable, and more than a little intimidating. They emerge in July and August, to coincide with the hatching of annual-cycle cicadas, their sole prey--larger cousins of the periodical cicadas the nation watched so obsessively earlier this summer.
Cicada killer females construct burrows that are small wonders of engineering and effort. Several feet long, and featuring numerous individual brood chambers at their far end, they require the excavation of hundreds of times the insects' own weight in soil. The female killers manage the feat in just a few hours, using only their jaws and hind legs.
After that they hunt, for the so-called dog-day cicadas of genus Tibicen. A killer paralyzes a cicada with a single sting, but getting it back to the burrow can be an all-day affair. It may be three times the killer's own weight--too heavy to properly fly with. Instead she drags it up the nearest tree, then launches herself, prey in claw, and glides as far as possible toward her burrow. She may have to repeat the process half a dozen times.
Back at the burrow, she deposits the paralyzed cicada in a brood chamber. Then she lays an egg and carefully tucks it beneath the cicada's foreleg, beside the puncture wound from her sting. (The doomed creature looks, creepily, like a wizened old man with a baguette tucked under his arm.) The female then seals the chamber with dirt, the cicada still living and immobilized within it. A few days later the egg hatches and grub begins to eat the cicada alive, using the puncture wood as an entry point. Later, the grub spins a cocoon, in which it metamorphoses into an adult wasp, emerging the following year. (Footage of these behaviors has been kindly posted online by filmmaker Sam Orr, who is working on a documentary about the 17-year cicadas.)
Meantime, the males are trying to win mates. Each claims about a square yard of territory. But because the bare ground on which these territories are established is basically featureless, the boundaries are impossible for the other males to determine. The result is a constant war of all against all. (In one experiment, a researcher laid down a grid of wooden dowels, providing visual cues for territorial boundaries. The violence immediately dropped by 80 percent.) There's a second indignity to male cicada killer life. Tethered by biological duty to their barren patches of earth, they get no relief from the sun, and spend the summer barfing on their own heads to generate a little evaporative cooling.
Despite being top predators, cicada killers are themselves frequently victimized by other insects. Some of these go after the killers' grubs; Chuck Holliday, emeritus professor of biology at Lafayette College and a leading cicada killer expert, recalls seeing one such parasitic fly approach a burrow and, in full flight, drop its egg down the hole "like one of those thermobaric bombs we used at Tora Bora." Aware of the danger, female cicada killers attempt to outwit these "satellite flies"--so named because they hover around the much larger wasps as if orbiting them--by dropping to the ground and remaining motionless for minutes at a time. Other cicada-killer antagonists go after the adults, spiking them with needle-like probosces and sucking out their guts--"the stuff of sand wasp nightmares, if they had them," as the late entomologist and science writer Howard Ensign Evans drily put it in his masterwork.
We humans, happily, have nothing to fear, although we're very likely to encounter the insects. Cicada killers live almost everywhere east of the Rockies and south of Ontario. Moreover, like pigeons, coyotes, and white-tailed deer, they actually benefit from human activity and enjoy suburban living. The soft soil around home foundations, in gardens, and on golf courses and playgrounds is ideal for burrowing. Some of the first research into cicada killer behavior was conducted beside two baseball fields in Brooklyn.
But unlike other wasp species that plague human summers, only the females of the cicada killers have stingers, and both their sting and their temperament are very mild. Holliday has captured, tagged, clipped the wings of, and in other ways harassed thousands of them in the course of his research. "I've done abominable things to these animals, and I've never had one try to sting me," he says. Instead, when threatened, they fly away or, if trapped in a burrow, frantically beat their wings against its walls, producing a loud rattlesnake-like whir. Male cicada killers are entirely stingless, and though they do tend to brusquely approach anything that moves inside their territory, including people, they're simply on the lookout for rivals and potential mates. Since humans are neither, they quickly break off their "attacks."
If your lawn becomes infested with killers and you simply must exterminate them, Holliday has a complete guide. But, as Evans wrote when considering the insect, these aren't "really necessary for the nonentomophobic among us who can tolerate a few brown spots in our lawns and occasional libidinous, dive-bombing male wasps." And Holliday encourages, instead, using them to introduce children to nature's intricate clockworks. Their predictable, curious behaviors are just the thing for capturing young minds. As for adult appreciation, the killers are some of the most effective cicada-silencers around. After the last few months' deafening treetop chorus, their presence should be welcome.