Brood X is just inches away, silently underfoot and out of sight — but not for long.

Expected to emerge en masse sometime later this month or early May, Brood X — also known as the Great Eastern Brood — is one of a number of separate broods of periodical cicadas which appear in regular intervals throughout eastern portions of the United States. This particular brood, the geographically largest, will appear in about 15 states, including Maryland and Washington, D.C.

“Annual cicadas come out every year, but there are periodical cicadas, known as Magicicadas, that emerge in either 13- or 17-year intervals,” explained Kyle Rambo, environmental planning and conservation director for NAS Patuxent River. “Brood X is a 17-year cicada, and there are at least a dozen 17-year broods.”

Unlike annual cicadas which are greenish in color, periodical cicadas are marked by reddish-orange eyes, legs and wing veins. The last emergence of Brood X was in 2004 and what residents will see this month is a result of the rampant breeding that took place 17 years ago.

Periodical cicada lifecycle

Periodical cicadas spend most of their life underground feeding on fluids from the roots of deciduous trees, growing from the size of a small ant to nearly the size of a two-inch adult. Once the top 8-inches of soil has reached a temperature around 64 degrees, the mature nymphs crawl out from underground, leaving visible holes about the width of a small finger and immediately head for a tree or other vertical surface to shed their shell.

“They must split their shell and pull themselves out,” Rambo said. “Think of it as pulling off your socks without using your hands. They need a rough surface to cling to for resistance and if that’s not tree bark, it might be the side of your house, your deck or fence, a cement wall, or a brick patio. And they’ll leave their empty nymphal casing hanging there.”

By the next morning their exoskeleton will have hardened and they’ll be able to fly, heading off for the treetops to fulfill their sole purpose — to mate and reproduce. Male cicadas have a special ribbed organ called a tymbal, which they vibrate to produce a sound that attracts females, and that’s when their loud, seemingly endless, buzzing chorus begins. Many sources note the sound produced by large numbers of cicadas can easily reach 90-100 decibels, the equivalent of a lawnmower or motorcycle; but, thankfully, they’re diurnal creatures and will quiet down in the evening.

“If you’re hearing any noise at night, it’s likely katydids or crickets, not cicadas,” Rambo said.

As menacing as they might look, cicadas do not bite or sting, are not poisonous and are not known to transmit any disease. The only damage they may do is to small, young trees or shrubs.

“The females have a saw-like ovipositor and will cut small slits into live tree branches to deposit their eggs,” Rambo said. “If small thin limbs get heavy enough with eggs, they can break off. The slits will also leave small scars behind on the branches.” (Experts recommend covering young trees in fine netting to protect them.)

Once the eggs hatch, the nymphs fall to the ground below and burrow into the soil, beginning a process that will repeat itself again, in precisely the same way, 17 years from now.

A harmless benefit to wildlife

Rambo also noted the mass emergence offers a sudden over-abundant food source for all species of wildlife.

“It’s a great protein source and everything eats them,” Rambo explained. “Foxes, raccoons, skunks, bats, birds, reptiles, amphibians and even things that don’t normally eat insects, like squirrels, will eat them. It’s a boon to wildlife and everything will exploit the resource. Everything will be healthy and everything will breed. It’s a good thing ecologically.”

Some domestic cats and dogs might also feast on the bounty, though Rambo says there’s no need for pet owners to worry.

“Your pet may puke from eating too many, but the cicadas are not poisonous or harmful to them in any other way,” he noted.

Can we eat them too?

Have an adventurous palate? Rambo encourages people to try cicadas, what he half-jokingly refers to as “a perfect gluten-free, low-fat, free-range, high-protein, organic snack.” And he speaks from experience.

“Last time they emerged, I collected nymphs, which are white and squishy, and fried them in butter with a little Old Bay; they were delicious,” he said. “I put them on a plate and skewered them with toothpicks, like hors d’oeuvres. If people like softshell crabs, it’s basically the same thing. They’re both arthropods.” (In fact, online sources warn that if you’re allergic to shellfish, you should not eat cicadas.)

If you haven’t stopped reading in horror and are actually willing to give Rambo’s culinary “treat” a try, he suggests going out at night, well after dark, and looking at the base of trees and on the leaves and branches of the shrubs growing beneath them.

“Go out with a flashlight and look for them; they’re pure white,” Rambo said. “Take them and drop them into a bucket of ice water to chill and preserve them. Don’t just drop them into a container or the next day you’ll find they’ve developed an exoskeleton, molted their skins, and the new version has orange wings and eyes.”

Because copperhead snakes will also be out at night seeking the same nymphs you are, it’s advisable to take a little extra caution.

“Copperheads are nocturnal snakes and cicadas emerge at night, so they may be feeding a little more aggressively,” Rambo warned. “If you’re walking through the woods at night, be careful, carry a flashlight and watch where you’re walking. But that same caution really applies any time of night in any year. Always watch where you put your feet.”

If nighttime nymph foraging isn’t your thing, no need to worry, there are plenty of online recipes for full-grown cicadas too. In fact, in much of the world, insects are already a common and culturally-accepted food source. As Rambo notes, we Americans tend to be “gastronomically prudish.”

At Pax River and in the surrounding community, we can expect to notice cicadas flying around, observe the shed nymphal casings they leave behind, spot lots of them sitting all over the limbs and trunks of trees — especially in thickly forested areas — and see them lying dead on the ground.

“They’re kind of oblivious to everything,” Rambo noted, “so they’ll occasionally run into cars, buildings and people, too.”

Whether you’re fascinated or horrified by the pending Brood X explosion, the cicadas will be around approximately four to six weeks before things begin to quiet down again by the end of June.