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Within a few months they will claw their way out of the underground, red eyes twinkling and a deafening song filling the air. It will be a convergence of creatures the likes of which have not been seen in the United States since Thomas Jefferson was president – and won’t happen again until 2245. It’s a rare emergence of insects that some call cicadapocalypse.
Billions of cicadas are expected to surface this spring when two different broods – one that appears every 13 years, and another every 17 years – emerge at the same time. The 13-year group, known as Brood XIX, or the Great Southern Brood, is the largest periodical cicada brood, spanning the southeastern United States. The Northern Illinois Brood, or Brood XIII, is published every 17 years.
“It’s rare that we see double broods of this size,” says Dr. Jonathan Larson, an extension entomologist and assistant professor at the University of Kentucky. “We’re talking about an absolute oddity of nature, one of America’s coolest insects.”
While the idea of a cicadapocalypse may seem ominous, experts predict that the two broods will not overlap significantly, and that the insects themselves, while loud and numerous, are harmless. Here’s what you need to know heading into cicada season.
What you need to know about cicada broods
This spring’s insects are part of a genus or group of cicadas in the eastern U.S. known as the Magicicada, or periodical cicadas. Three species arise in a 17-year cycle, and four species in a 13-year cycle. (Scientists have long debated the meaning of these numbers, which are both prime numbers – some researchers have suggested that appearing in these prime numbered years makes the periodical cicadas less likely to be killed by predators with a 2- or 3-year life cycle. But the jury is still out.)
The pattern that periodical species follow is different from that of “annual” cicadas, which don’t actually have an annual life cycle, even though you can see them every summer in much of the United States. The nymphs, or babies, of yearling crickets spend two to five years underground, growing slowly, until they are ready to emerge. There are so many overlapping generations that there seems to be a steady stream of these crickets every year.
It is easy to distinguish between annual and periodical cicadas. Annuals generally appear later in the year than magazines. For example, the annual cicadas of the genus Neotibicen usually appear during the dog days of summer, around August, while the magazines appear in the spring. Although there are numerous species of annual cicadas, many are large and greenish. Periodical crickets are smaller and usually black, with bright red eyes and orange-tinted wings and legs.
Cicadas are divided into groups called broods based on when they emerge. A brood can contain crickets of multiple species. As long as they mature at the same time in the same 13 or 17 year cycle, they count as members of the same brood.
When and where will the crickets emerge?
This spring’s periodical cicadas will appear when soil temperatures 8 inches deep reach 64 degrees Fahrenheit (about 18 degrees Celsius). This will probably happen sometime in mid-May. The adult life cycle of the individual insects lasts only a few weeks, but their emergence will be staggered, so there will be about six weeks of crickets.
That month and a half will be chock full of loud singing, mating and then dying, like “the most macabre Mardi Gras you have ever seen,” Larson said.
Parts of the Midwest and Southeast are under cicadas this spring. Northern Illinois, along with southern Wisconsin, eastern Iowa and northwestern Indiana are likely to encounter Brood XIII insects; central and southern Illinois, most of Missouri and scattered areas of Kentucky, Tennessee, Virginia, Maryland, North Carolina, South Carolina, Georgia, Alabama, Mississippi, Louisiana and Arkansas will get Brood XIX bugs.
There are some areas in central Illinois where the geographic ranges of the two broods have historically been close and could potentially overlap. However, predictions of a cicadapocalypse – in which Brood XIII and Brood XIX appear in the same place at the same time – are likely exaggerated.
“We’re not even sure that they’re really going to overlap,” said Dr. Chris Simon, a professor of ecology and evolutionary biology at the University of Connecticut. Her research group at the university maintains a website with information about cicadas, including maps showing where the broods historically originated.
The double emergence of Broods These two broods haven’t been above ground at the same time since 1803, and after this year they won’t be reunited until 2245.
However, the co-occurrence of several cicada broods somewhere in the United States is not that rare. It last happened in 2015; it will happen again in 2037.
Preparing for crickets
Even though a large overlap between the two cicada broods is unlikely, having one brood in an area still means numerous insects.
“You would expect lots of cicada exoskeletons to cover your trees and shrubs. You would expect to hear a lot of noise,” Larson said. The insects are most likely to be in wooded areas near water, he added.
Although the sheer number of insects, along with their signature loud jackhammer sounds and bright red eyes, may make some people hesitate, Larson notes that crickets are harmless. They pose no risk to garden plants. However, if you have young trees, crickets can potentially damage them when the insects cut into branches to lay their eggs. You can limit this damage by covering the trees with cicada nets.
Cicadas will not bite or sting you or your pets. If your dog eats one or two cicadas, he said, the animal will be fine.
Dogs aren’t the only ones tempted to eat crickets; people have been eating them for thousands of years. “They have kind of a natural, sweet nutty flavor,” Larson said. (However, if you are allergic to shellfish, you should avoid eating crickets; a protein in shellfish that has been linked to allergies is also present in many insects.)
If you live in an area where cicadas appear this spring, you can download community science apps to help researchers study these bugs.
“The main thing we want people to know is that they need to download the Cicada Safari app, which is free on the internet, and all they have to do is photograph the crickets that they see,” Simon said. Those photos are sent to scientists, who then map where and when the cicadas emerge: information vital to scientists studying how climate change affects the cicadas and to predict future cicada activity.
In addition to the larger scientific story of cicadas, Larson said he hopes people will embrace cicada spring simply because it’s a rare opportunity to see some of the world’s most unusual insect behavior.
“These are some of the coolest insects in America,” Larson said. “I really hope that people will appreciate this for what it is: this unique natural phenomenon that you won’t find anywhere else. It is beautiful.”
Kate Golembiewski is a freelance science writer based in Chicago who is particularly interested in zoology, thermodynamics and death.
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