Thursday, August 26, 2010

Eastern Cicada Killer Wasps (Sphecius speciosus)

A blue jay nailed a cicada at lunch today; I saw it from the screen porch. The cicada buzzed suddenly and long, an auditory exclamation point if ever there was one. Then the tone wavered once, and continued more thinly as he got free of the jay.

The jay jetted after the tailspinning cicada, scolding it.

—Caught it. The cicada’s rasp ended abruptly.

Insect life is fraught; they are lucky their nervous systems are so simple. There are a ton of them, and a ton of checks on their numbers. Annie Dillard summed up their situation: “There is a terrible innocence in the benumbed world of the lower animals, reducing life there to a universal chomp.”

For the past month and a half, we’ve had the cicada killers again in our backyard. These solitary wasps attract attention wherever they live, because they are so large—up to about an inch and a half long—and so busy. They’re damned intimidating! But I urge you to learn more about them. They will not hurt you.

Let’s discuss armament first: The males have none; they literally cannot sting you. They can poke at you with their pointy abdomen, but that’s it. The females can sting, but they won’t—well, unless you are harassing them bodily, just as a hamster will bite you if you squeeze it too hard.

They could conceivably bite you, but then so can a katydid. So let’s just stop thinking of cicada killers as scary, right now.

Cicada killers follow the general lifestyle of most wasps, which is for the females to build a nest, collect insects and spiders, paralyze them, and lay their eggs on them. The newly hatched wasps (why not call them babies?) eat the food their mothers hunted for them. Remember that a mother cheetah brings food to her kittens, too.

Because they’re solitary, each wasp is generally on his or her own; there isn’t much of a communal nest, although apparently sometimes females will share a burrow.

The males are downright hostile to one another. They emerge from their natal burrows before the females do and immediately establish territories. Each male patrols his spot, circling in reconnaissance, resting on a leaf or branch, or hovering over the area, and vigorously chases out just about any kind of winged intruder, even wayward butterflies. . . . It’s like they have lots of testosterone, okay?

We’ve seen some heated altercations between male cicada killers; they grapple in the air; sometimes they drop heavily to the sidewalk, with a cracking sound that just can’t mean anything good for their health.

The males treat female cicada killers quite differently, of course.

Once the females are pregnant, they tunnel into the soil, carrying the dirt in their mouths, creating a nest in which to store cicadas and eggs. These tunnels can be 1–4 feet long, with multiple chambers.

The evidence aboveground can be striking—mounds of dirt in your yard, or in golf courses, in gardens, wherever the earth is light and friable. The entry hole is about an inch wide, and there’s usually a small ditch leading to it that looks like someone dragged a thumb across the mound in a curving path.

Some people get bent out of shape over these mounds, but I contend that the wasps are helping to aerate the soil. And if cicada killers have chosen your soil for their nests, then take it as a compliment: your ground is loose and workable!

So, in case you haven’t figured it out yet: the female cicada killer wasps hunt cicadas, to provide food for their babies.

Cicadas are hefty prey for a wasp—so now you understand why cicada killer wasps are rather large, too. They have to transport a cicada’s dead weight all the way back to the burrow.

And this, too, is remarkable. Howard Ensign Evans described the scene in his book Wasp Farm: “Wasps are now out en masse harvesting the bounty of insects. Hear that cicada stop his song mid-way? Like as not he is a victim of the giant cicada-killer, who will inter him beneath the driveway.”

So, up in the tree, the cicada killer stings the unfortunate cicada, paralyzing it; then she has to fly it home. But it’s too heavy for her to truly “fly”—instead, it’s more of a controlled glide. Sometimes the wasps have to climb up another tree trunk with the prey in order to glide again and gain more distance. If they’re lucky, they land pretty near the opening of the tunnel.

And they quickly lug the cicada inside, where it will never again be seen by human eyes.

I have seen them swoop in many times with their prey. The immediate impression is that a stupendously large bug has just crash-landed nearby. Once—in fact, it was when I was taking pictures of the micrathena—a cicada-laden wasp zoomed right in between my legs. I hadn’t known it, but I was standing exactly in front of her burrow.

I’m sure it took courage on both our parts!

Now that it’s late August, the cicada killers’ lives are winding down, just as the nights have finally gotten tolerably cool and the tree leaves have become faded and leathery. It’s all part of the seasons, the rotation of the Earth, just as each summer the onset of cicada song lets us know it’s time for the dog days, and how many weeks until the first frost . . . and when to look for the new crop of cicada killer wasps.

Books Adored in This Post

Howard Ensign Evans, Wasp Farm (Ithaca: Cornell University Press, 1985).

Annie Dillard, Pilgrim at Tinker Creek (New York: Harper and Row, 1974).

Photographs by Susan Ferber, who has a great time each summer making portraits of our cicada killer wasps. Doesn't she do a great job?

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