Like the return of a summer blockbuster movie, millions of cicadas, with their ear-piercing mating calls, are about to burrow up from underground after a 17-year hiatus. But the questions are when, where and which type?
“There's a lot of buzz this year, pardon the pun, about the emergence of brood 10, or as it's written Brood X,” said entomologist Dr. Art Evans, who you may remember from VPM’s long running program “ What’s Bugging You?”
Evans says Brood X, which is among the largest of the species, won’t emerge in Central Virginia. The closest sites will be in Northern Virginia.
“In Virginia, we have several 17-year broods and we also have a 13 year brood as well,” Evans said. “And when we talk about these broods, whether they're 13 or 17 year, it involves six species of periodical cicadas.”
But Evans said that seeing Brood X in Central Virginia is highly unlikely.
“If anyone sees any 17-year cicadas, here in the Richmond area, that would be big [bug] news,” he said.
If you find yourself in the northern part of the state, though, Evans says it’s easy to tell them apart from other broods.
“You can distinguish them visually,” Evans said. “They have a different extent of orange markings on their black bodies, and they have very different calls to.”
Brood X cicadas can emerge as far west as Illinois and Michigan to New York, and as far south as Georgia.
“But the primary centers of the emergence will be in the Ohio River Valley and then in West Virginia, Northern Virginia, Pennsylvania, and Maryland,” he said. “But there's still a couple that pop up in other places too.”
Brood X is just one group of a dozen broods, or “year-classes.” While underground, the cicadas--at this stage called nymphs--are feeding on the saps of tree roots to help them grow.
“There's some really interesting science that's going on right now, trying to figure out this puzzle ,” of which cicadas belong to which groups, Evans said.
And, if you’re confused as to why you may hear cicadas every year in Central Virginia, you’re not alone.
“Generations overlap. And so that's why we see them annually. And they don't come out until later,” Evans said.
The fun, he said, is trying to figure out which cicadas are burrowing up from the ground every year.
“And that's where there's a lot of interest in people trying to figure out are those actually members of this particular brood, Brood X?” Evans said. “Or are they stragglers from other broods? Are they ones that are coming out four years early or one year late? You know, that's where a lot of excitement is trying to figure out all the strange and wonderful aspects of these periodical cicadas.”
Then, depending on the species, their life cycle can be anywhere to two or three or more years emerging, Evans said.
And, to confuse the emergence process further, there are periodical and annual cicadas. The broods fall under the periodical format.
“Although nearly all of the periodical cicadas in a given region emerge in the same year, the cicadas in different regions are not synchronized and may emerge in different years,” according to University of Connecticut, which has an enormous amount of information.
As a result, they say it’s possible to find adult periodical cicadas in almost any year by traveling to the appropriate location.
The Sound of a Lawnmower
Once out of the ground, cicadas’ main goals are to shed their shells and then find a mate.
According to website EarthSky, “the males head toward the tops of trees and let out a loud whirring noise that can fill the air at up to 80 to 100 decibels, equal to the intensity of a lawn mower or motorcycle.”
“When they start chorusing together, that just shuts everything down. I mean, not only are you overwhelmed by their sheer sound, but they're influencing the behavior of other animals including ourselves,” Evans said.
Evans said those sounds, which are some of the loudest in nature, are the mating calls of male cicadas. Their muscles perform an intricate sequence of movements that happen at 60 cycles or more per second. They use a body part known as a “tymbal,” like the instrument.
“So you have this incredible sound that is produced by the cicadas and the shape of the tymbals,” Evans said. “And the air chambers that are inside the male's abdomen helps amplify the sound.”
He said all these things combined together means that each species of cicada has its own particular call, which the females can detect.
“They happen to emerge right around the time of graduations and you know, the first weddings of the season,” he said. “And so a lot of people are very unhappy with the appearance of cicadas because they can greatly impact outdoor activities.”
You’ll be able to hear the chorus for about four to six weeks.
During the brief life window, and after the males find a mate and well, mate, female cicadas lay their eggs in tree limbs or twigs. Once the eggs hatch, the nymphs burrow far underground near tree roots to start the process all over again.
For local bug lovers in Central Virginia, Evans says the Richmond-area will see annual cicadas starting around mid-may.
“They're in there now waiting. When the soil temperatures reach 64 degrees Fahrenheit or more for a sustained period, that's when it will start seeing the emergence,” said Evans.
Evans said there’s so many unanswered questions around cicadas and so much fascinating science too, such as systematics of ecology and evolution that anyone who may ask “what’s the point,” of cicadas, is missing the bigger picture.
