In the coming weeks, as temperatures warm across a dozen states in the mid-Atlantic region, billions of Brood X cicadas will emerge from the soil and head for the trees to shed their exoskeletons, unfurl their wings, sing, mate, lay eggs and die.
Wonder about their purpose? Well, it’s not complicated, according to Gaye Williams, an entomologist with the Maryland Department of Agriculture.
“I mean, they’re not great writers or anything,” she said. “They exist to make more cicadas, the same as people.”
Certain types of the insect—known as annual, or “dog day” cicadas—are present every year, filling the humid air with distinctive buzzing each summer. But this year’s cicadas are different, part of a periodical “brood” that mature underground and then emerge in cycles of 13 or 17 years. This year’s group, Brood X (that’s 10, in Roman numerals), is also known as “the big brood,” Williams said, “because there are so many of them.”
Opinions differ on the brood’s distribution, though hot spots in the mid-Atlantic region are likely to include swaths of Pennsylvania, Maryland, Washington, D.C., West Virginia and Virginia, according to a map from cicadas.info, a tracking and information site.
Brood X consists of three species, Williams said—Magicicada septendecim (the most common and also the largest), Magicicada septendecula, and Magicicada cassinii (the smallest of the three). All have the same basic color scheme, with black bodies, orange wings and distinctive red eyes, though there are slight variations—different hues or buzzes—between them.
The brood’s life cycle began 17 years ago during the last emergence in 2004, after the cicadas mated and the females made their way to the treetops to lay their eggs. Every female cicada has “an egg layer—like a little knife,” Williams said. “She’ll find twigs—usually she prefers ones about the thickness of a pencil, so she can hold onto them with her feet—and then cut little slits in them, and then lay the tiny eggs in the slits.” Each slit is injected with a chemical that prevents the tree from closing them up, Williams said.
The female dies shortly after laying the eggs, and several weeks later, her offspring, known as nymphs, emerge from the eggs. They’re tiny—about a millimeter and a half long—and white, with microscopic red eyes and a fuzzy coating. Once they’ve molted, the nymphs drop from the branch to the ground, and the lucky ones—“who don’t land in a dog dish full of water, or on a hot car”—start to dig. Once underground, they hunt around for a tree root, then attach to it and begin to feed on sap. They’ll remain there, growing slowly, molting and maturing, for 17 years, until it’s time to emerge.
And so, Williams said, it’s incorrect to proclaim that the cicadas are coming.
“They aren’t coming. They’ve been here, underground, this whole time,” she said. “They’ve been carrying on their normal little insect lives. They shed their skin, they grow, they rest at each of these stages for a couple of years.”
And the Escape Begins
Their emergence comes in stages, triggered by temperature changes that warm the soil to around 64 degrees. The cicadas start by digging their escape tunnels—each about the width of a finger—and then sit inside, waiting for warmth. Some outliers have already come out, but the masses will start in the coming weeks, perhaps as soon as this weekend, Williams said.
“It’s going to be like a tide,” she said. “That first bit just wets the sand, and then, suddenly, you’ll be three feet deep in the water. It’ll be so much fun.”
Traditionally, it starts on a warm night, with multiple cicadas digging out from underground and scuttling around until they find a vertical surface (preferably a tree) and start climbing. Once they’re attached to the bark, the cicadas shed their final exoskeleton, unfurl their wings, and wait for their new bodies to harden. And then the mating ritual—and the loud buzzing of the cicadas’ love song—begins.
“The males have to get out there and start bragging together before the girls are interested. They start chorusing—all three species have different sounds, which is how they segregate themselves—and then they really get serious and it becomes a kind of crooning,” Williams said.
The buzzing, which can be as loud as a leaf blower or a lawn mower, attracts the female cicadas, who take their pick of the pack, Williams said.
“Basically if a girl gets near they start poking at her, and if she doesn’t like him she kicks him away, flicking her wings around,” she said. “Then another guy says, ‘Hey, what’s going on over here?’ So it’s pretty busy. Eventually, at some point, she’ll decide there’s a guy she likes, and then they get to it.”
It’s hard to say what drives that decision, Williams added. “Maybe it’s something in the way he walks up, or his song, or who knows what,” she said. “They have very tiny brains. They work! But they’re very tiny, so who knows what motivates them.”
The males die after mating, and the females follow suit after laying their eggs, starting the cycle over again.
The whole process takes several weeks, and it’s loud, and visible—the ground littered with crunchy discarded exoskeletons and pockmarked with thumb-sized escape holes—but it’s harmless, Williams said.
Cicadas can’t hurt humans—they don’t sting or bite, and they’re not poisonous—and while they may collide with us on occasion during their clumsy attempts at flight, it’s not intentional.
“Their wing-to-body ratio is not that good, so they are not little hummingbirds and they don’t fly well,” Williams said. “But if they do bang into you, and they had voices, they’d say, ‘Oop, sorry, ma’am,’ because they’re just aiming for the trees.”
Local cicada celebrations
Some cities have found creative ways to celebrate the emergence of the cicadas, including cicada bingo in Fairfax, Virginia., and the Cicada Parade-a, a large-scale public art project in Baltimore. In Maryland, Gov. Larry Hogan proclaimed May and June as Magicicada Months, asking residents to use the opportunity to learn about the insects and to refrain from trying to kill them with insecticides or other chemicals (it won’t really work and endangers other insects, he said in a statement).
While it might seem overwhelming, the cicadas’ ritual is a normal part of nature, Williams said—even if it feels like a lot to deal with on top of a global pandemic, the echoes of murder hornets and that one day last week where we all had a slight chance of being killed by that Chinese rocket.
“We had the pandemic and the stupid rocket and now we have one of the most remarkable natural phenomena on the planet,” Williams said. “I mean, this isn’t even making lemonades out of lemons, it’s just having a really good time. This doesn’t happen anywhere else, and it’s amazing.”
source: NextGov
