Periodic crickets, as they are called, spend almost their entire lives a foot or two underground, living on sap from tree roots. Then, in the spring of their 13th or 17th year, adult cicada nymphs dig out of the ground synchronously and in large numbers for a short adult stage. Really huge numbers.
The insects climb the nearest vertical surface, often the tree whose roots supported them. They shed their exoskeletons and blow their wings. Then, after resting for a few days, recovering and waiting for their shells to harden, mating begins. The frenzy is impossible to miss once the males start broadcasting their high-pitched mating song. This is done through sound-producing structures called tymbals on either side of their abdomen.
“They can gather … in parks, forests, neighborhoods, and can seemingly be anywhere,” explained Michigan State University entomologist Gary Parsons in an MSU question and answer session on the phenomenon. “When they are so numerous, they fly, land and crawl everywhere, also occasionally landing on people.”
Here are answers to some of the key questions about the emergence of this spring’s great cicadas.
What is Brood X?
The eastern United States is home to six species of periodic crickets that emerge in different years. Groups of crickets that share the same emergence years are known as broods.
This spring, it’s time for members of one of the largest broods of 17-year-old crickets, dubbed Brood X or the Great Eastern Brood, to nestle out of their subterranean hideouts and show off their black bodies and bold red eyes. Expect to see all three 17-year-old strains: Magicicada septendecim, Magicicada cassini, and Magicicada septendecula.
Which states will be affected?
Parts of 15 states, as well as Washington, DC, will 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.
When do the crickets emerge?
The return of the crickets usually starts around early to mid-May (although it can come earlier) and lasts until the end of June. Needless to say, it is a spectacle. Some people consider the mass of insects an annoying annoyance, 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 pop up to experience the sights and sounds and help scientists map crickets.
A free app created at Mount St. Joseph University in Cincinnati called Cicada Safari and available for iOS and Android lets the cicada-curious record periodic cicada sightings. 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. Cicada mapping helps scientists to periodically verify insect life cycles, as well as relationships with each other, to gain a better understanding of biodiversity, biogeography and behavior and ecology.
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 trackers may see “laggards” of other broods this year.
“From a biological perspective, four-year laggards of each of these broods are interesting because they can cause gene flow between them,” explains the University of Connecticut. “From a practical standpoint, the four-year laggards of all these broods complicate mapping efforts because it is difficult to assign populations to a brood.”
Laggards may confuse map efforts, but the university insists that a “misleading map is worse than no map at all.”
Why are so many coming out at once?
It is thought that by emerging in such large numbers, enough of them can live on to mate – in fact, force in number.
The crickets usually start hatching when soil temperatures reach 64 degrees Fahrenheit (18 degrees Celsius) 8 inches (20 centimeters) underground. “That seems to be the trigger that makes them all show up in one area in a few days or weeks,” says Parson. A warm rain often causes their emergence.
Because periodic crickets are sensitive to climate, patterns of different broods and types reflect climate change, note John Cooley and Chris Simon, professors of ecology and evolutionary biology at the University of Connecticut.
“For example, genetic and other data from our work indicates that the 13-year-old species Magicicada neotredecim, found in the Upper Mississippi Valley, originated shortly after the last Ice Age,” they write in a piece for The Conversation. “As the environment warmed, 17-year-old crickets consecutively emerged in the area, generation after generation, after 13 years underground, until they were permanently shifted into a 13-year cycle.”
How does the male mating call sound?
It varies by species, but it can sound like a high-pitched electric buzz, a chirp, or a rattle. Fast forward to 2:14 in Sir David Attenborough’s video above to listen closely. The females respond to the call of the males by clicking their wings, and all the back and forth movement makes for a decent symphony.
Can crickets hurt me?
The insects are harmless. They do not sting, bite or carry disease, and they usually do not enter, although they do collect on outside walls.
“The only way they could get in is accidentally fly in through an open door or window, or because they landed on a person who then carried them in unnoticed,” said Parsons.
How long will Brood X last?
Mass mating takes three to four weeks. Shortly after, the newly hatched nymphs will crawl to the edge of the tree branches where the females laid their eggs, fall to the ground and burrow. And so the cycle begins again. Godspeed, Brood X.