Every 17 years, they crawl out of the ground in droves and cover trees, swarming large chunks of the Midwest and deafening us with their perpetual mating calls.
It may sound like a horror movie, but it’s far from it. It’s the periodical cicada known as Brood X (or 10), which will swarm the Midwest this spring, including the western part of Ohio, especially areas such as Cincinnati, Dayton and even east of Columbus.
Because the last time Brood X emerged was 2004, it’s a big spring for the entomologists who study them, according to Joe Boggs, assistant professor with OSU Extension and Ohio State's Department of Entomology.
“The problem with periodical cicadas is we know far less than what we think we know; it’s a complex story,” he said. “But we’re learning more with each brood.”
There are annual cicadas and periodical cicadas, which emerge every 13 or 17 years in a given spring.
The lifecycle of a cicada starts with females laying hundreds of eggs in tree branches. Those eggs hatch, and ant-like nymphs fall to the soil, burrow underground and feed on tree roots.
When it’s time – each year, 13 years or 17 years – the nymphs emerge, shed their nymph skin and develop a shell and wings. The males then sing in a chorus to attract females. They mate and females lay their eggs.
It’s the same lifecycle for annual and periodical cicadas, but annual cicadas emerge in relatively low numbers in the summer, which gives them the common name of “dog-day cicadas.” Periodical cicadas emerge en masse in huge numbers in the spring with the females causing noticeable damage as they lay their eggs.
Cicadas are not locusts, Boggs explained.
Locusts are highly migratory and destructive grasshoppers that haven’t been around North America since the end of the 19th century. Cicadas, meanwhile, stay in one area and co-exist with their environment.
Cicadas stay underground for most of their lives to avoid predators. And when they emerge, they do so by the billions.
“It’s called ‘predator satiation,’” Boggs said. “You flood the market. A lot of cicadas die when they emerge because of animals eating them but not enough to affect the population.”
A big brood
Brood X includes three species – Magicicada septendecim, Magicicada cassini and Magicicada septendecula. Why that matters is each species will come up at different times during the spring.
“The perception is once they come up, you get a big number. And as they start to go away, you think it’s over, then here it comes again like a tsunami,” Boggs said. “But one species will arrive in big numbers first, another in the middle and a third toward the end.”
When Brood X arrives this year, entomologists can do better DNA analysis than they could in 2004. That should help them understand the species associated with Brood X better. Also, geographical mapping should be more precise this year with help from technology.
Researchers are even asking people to send in pictures and report when and where they’re seeing cicadas emerge with a new app called Cicada Safari.
“It’s going to be very helpful to report real time where people are seeing emergences occurring,” Boggs said. “It could be we’re seeing this brood break up and expand, or they could be joining.”
Because we’ll have three different species, we’ll have three different songs. Some can be incredibly loud, even distressing to people.
Protecting trees, pets and your ears
Cicadas tend to stay with one tree or area for their lifespan. So if the trees in your neighborhood were planted in recent years, or you don’t have any old trees nearby, you probably will miss them altogether.
If you have older trees, or live near a forest or cemetery or park with older trees, you will probably see and hear cicadas.
Should you protect your trees?
Boggs recommends waiting to see if any cicadas actually show up. If they do, remember: They don’t do a lot of damage. The eggs they lay and where they feed after emerging are in the smaller tree branches. This may cause “flagging,” but it’s about as dangerous as pruning a tree.
However, if you see cicadas on your tree and you do want to protect them, simply brush them off and wrap them in a mesh netting. You can find cicada netting online or at gardening stores.
Also, don’t spray! Because cicadas have a piercing or sucking mouthpart, insecticides will have a limited effect on them but may kill other insects or parts of the trees themselves.
What about pets?
Some animals, dogs for instance, eat a lot of them. While cicadas aren’t poisonous, animals can get sick from overindulging, which might mean a trip to the vet. So watch your pets.
What about all the noise?
Cicadas can be loud, deafening in fact.
The males’ singing – that buzzing, clicking or vibrational noise – is a synchronized chorus call to attract females to mate.
“There’s a lot of perceived strategies to chorusing to attract females,” Boggs said. “And because we’ll have three different species, we’ll have three different songs. Some can be incredibly loud, even distressing to people.”
So if you are visited by cicadas this spring, you may be in for an earlier wakeup call.
But hang in there.
After all, once they’re gone this spring you won’t be visited by Brood X for another 17 years.