Now that Brood X cicadas have tunneled from their underground homes in the eastern US, you may be wondering when they will leave. Here̵
What is Bread X?
In case you’re new to Brood X, it’s a group of periodic crickets, which are different from annual crickets. They spend most of their lives a foot or two underground, subsisting on sap from tree roots. Then, in the spring of their 13th or 17th year, depending on the type, adult cicada nymphs emerge for a short adult stage, synchronously and in large numbers. They mate and then die, and their newly hatched offspring fall to the ground and burrow for the next 13 or 17 years.
Groups of crickets that share the same emergence years are known as brood. Insects belonging to one of the largest broods of 17-year-old crickets, called Brood X or the Great Oriental Brood, are now making their appearance.
After hatching, the insects climb to the nearest vertical surface. They shed their exoskeletons and inflate their wings. After a few days of rest and waiting for their shells to harden, mating begins. The burst of activity is impossible to miss once males start broadcasting their high-pitched mating song. This happens through sound-producing structures called tymbals on either side of their abdomen.
Mass mating lasts at least three to four weeks. Soon after, the newly hatched nymphs crawl to the edge of the tree branches where the females laid their eggs, fall to the ground and burrow for the next 17 years. And the cycle starts again.
When will Brood X cicadas disappear?
The insects usually begin to emerge when soil temperatures 20 inches below ground reach 64 degrees Fahrenheit (18 degrees Celsius), with warm rain often triggering their emergence. Once above ground, they generally have a lifespan of four weeks, depending on the weather. Since the crickets usually start appearing around early to mid-May, they should start dying off in late June or early July.
“Because the emergence was spread out over seven or more days of variable weather, they can be five weeks in one area or even slightly longer,” said Chris Simon, a professor of ecology and evolutionary biology at the University of Connecticut. “They generally decrease gradually.”
Brood X cicada emergence in pictures: what it looks like when trillions of insects appear
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Where does Brood X come from?
Parts of 15 states, as well as Washington, DC, hear the romantic serenades of males in trees, trying to attract females. The states are Delaware, Georgia, Illinois, Indiana, Kentucky, Maryland, Michigan, North Carolina, New Jersey, New York, Ohio, Pennsylvania, Tennessee, Virginia, and West Virginia.
Cooler than usual weather in parts of the US this year has delayed their appearance in some places, and in others they are not showing up at all due to development, pesticide use and invasive species.
Residents in places where they have shown up in full are busy sharing images and sounds on social media.
What do Brood X cicadas sound like?
It varies by species, but their call may sound like a high-pitched electrical buzz, chirp, or rattle. (Hear it below.) The call of a group of men can exceed 90 decibels, about the same level as a motorcycle about 8 meters away. The females respond to the males’ come-here calls by clicking their wings, and all the back and forth creates a signature symphony.
“If you don’t live in a place with crickets, I can best describe the sound as a broken car alarm crossed with a UFO landing,” shared a Twitter user in Washington, DC. Hear the sounds for yourself in the videos above or the audio below. And, make sure you hear cicadas and not a car or house alarm.
Hear the 17 year old crickets
Can Crickets Hurt Humans? What about trees?
No, the insects are harmless. They don’t sting, bite, or carry disease, and they don’t usually get inside, although they do gather on exterior walls.
“The only way they got in is by accidentally flying in through an open door or window, or because they landed on a person who then carried them in undetected,” Parsons says.
During dense emergence, females may lay enough eggs in branches to damage young trees, but the abundant egg-laying also naturally prunes trees, resulting in more flowers and fruit in the years that follow. The crickets also have other ecological benefits. Periodic crickets aerate large amounts of soil when they emerge en masse, and when they die, their decaying bodies enrich the soil with nutrients.
Can pest control agents help me?
When people call for help during the emergence of cicadas, those involved in pest control are largely in a position to educate customers about why the pest professionals don’t show up and spray their yard with pesticides.
“We really want people to understand and know that pesticides are not the answer, which sounds really funny when it comes from a pest control company,” Frank Meek of pest control company Orkin. “Pesticides are not the thing to use on this insect. They don’t work for it, and it’s a waste of product, and it’s an environmental hazard to just spray down because you’re afraid of the crickets.”
Why do so many crickets come out at once?
It’s thought that by showing up in such great numbers, enough of them can avoid predators and live on to mate — force in number, in fact.
What can scientists learn from cricket mapping?
Some people see the mass of insects as a, but others welcome it as an awe-inspiring natural wonder. Some in the latter category even regularly travel across the US to areas where cicadas appear to experience the sights and sounds and help scientists map the creatures.
Mapping cicadas helps scientists verify the life cycles of the periodic insects, as well as the interrelations of broods, to better understand biodiversity, biogeography and ecology.
A free app created at Mount St. Joseph University in Cincinnati called Cicada Safari and available for iOS and Android lets citizen scientists record periodic sightings of cicadas. They can also record sightings on the Cicada Mania and iNaturalist websites, a joint initiative of the California Academy of Sciences and the National Geographic Society.
Because periodic cicadas are climate sensitive, patterns of different broods and species reflect climate changes, note John Cooley and
“For example, genetic and other data from our work indicate that the 13-year-old species Magicicada neotredecim, which is found in the upper Mississippi Valley, formed shortly after the last ice age,” they write in a piece for The Conversation. “As the environment warmed, 17-year-old crickets in the area emerged sequentially, generation after generation, after 13 years underground until they were permanently shifted to a 13-year cycle.”
Because Brood X occurs four years after Brood VI and four years before Brood XIV, and because the three broods are adjacent in parts of their geographic range, cicada followers may spot “stragglers” of other broods this year.
“From a biological perspective, four-year-old stragglers from one of these broods are of interest because they can trigger gene flow between these broods,” explains the University of Connecticut. “From a practical perspective, four-year-old stragglers from one of these broods complicate mapping efforts because populations may be difficult to assign to a brood.”
Laggards can confuse mapping efforts, but the university emphasizes that a “misleading map is worse than no map at all”.
Godspeed, Brood X.