SPRINGDALE, Ark. — A rare, once-in-a-lifetime cicada co-emergence is just months away from occurring, with millions of the colorful insects expected to emerge from the ground across the U.S. and fill the summer air with their distinctive song.
This year is a big one for cicada fanatics because Broods XIII (13) and XIX (19) are set to co-emerge. But what is a co-emergence, what are broods, and where have these special cicadas been for over a decade?
Here, we break down why 2024 is a special year for cicadas and why people across the country will be seeing more of them than usual.
Cicada Life Cycle
Cicadas are six-legged insects found all over the globe, known for their distinct sounds, shiny colors, and leaving their husks to coat tree trunks during the summer.
Most people probably notice some cicadas every summer. More often than not, those are annual cicadas, or “dog day cicadas,” which come out every year when things warm up.
This year’s big event, the emergence of Broods 13 and 19, involves periodical cicadas, a type of cicada special to the U.S.
While there are around 3,400 species of cicada worldwide, only seven are periodical.
What are periodical cicadas?
"Periodical cicadas are found only in eastern North America. There are seven species — four with 13-year life cycles and three with 17-year cycles," according to the University of Connecticut (UCONN) cicada project.
There are 15 broods, each of which features one or more of the seven periodical cicada species.
Periodical cicadas emerge when soil temperatures reach around 64 degrees at depths of 7-8 inches.
There are seven total species of periodical cicadas in the U.S. These species spend the majority of their lives underground in a "nymph" state.
There, the nymphs feed on fluids from tree roots. Eventually, in the spring of their 13th or 17th year, mature cicada nymphs emerge, being active for four to six weeks.
13-year cicadas are more common in more southerly regions of the U.S. as the warmer temperatures lead to faster maturation.
Male cicadas congregate in "chorus centers," utilizing their unique and recognizable mating calls to attract females, who eventually mate and lay hundreds of eggs in the stems of plants. Within two months of emerging, the adult cicadas die, completing the life cycle.
The eggs will hatch later that summer, and the nymphs will burrow underground to develop for another 13 or 17 years.
Austin Jones, an entomologist at the University of Arkansas, says that the 13- and 17-year emergences occur due to an adaptation to better handle predators.
"The emergence cohorts are known as broods and their synchronized emergence is thought to be a way to overcome predators with a 'you can’t eat us all' strategy," Jones said.
The 2024 Co-emergence
In cicada terms, emergence is when a brood of periodical cicadas is mature and leaves its underground burrows to mate, lay eggs, and die.
A co-emergence is when a 13-year brood and a 17-year brood happen to emerge in the same year, a typically rare occurrence, and one that people will be lucky to experience in 2024.
This year, Broods 13 and 19 are set to co-emerge for the first time in 221 years. This will be the first co-emergence of these specific broods since 1803. With another 221-year gap after this year, the next co-emergence for Broods 13 and 19 will be in 2245.
Brood 19, or the “Great Southern Brood,” emerges every 13 years and features four different cicada species. The brood can be found in Alabama, Arkansas, Georgia, Iowa, Illinois, Indiana, Kentucky, Louisiana, Maryland, Missouri, Mississippi, North Carolina, Oklahoma, South Carolina, Tennessee, and Virginia.
Additionally, the Great Southern Brood also happens to be the largest of the periodical cicada broods.
Brood 13, or the “Northern Illinois Brood,” emerges every 17 years and features three cicada species. The brood can be found in Iowa, Illinois, Indiana, and Wisconsin.
John Cooley, an associate professor of Ecology and Evolutionary Biology at UCONN-Hartford, says that Brood 19 is the largest of them all, and can contain billions of cicadas.
“Periodical cicada broods vary in size—the smallest is Brood VII, just about contained in the Onondaga Nation south of Syracuse. The largest is Brood XIX, set to emerge in your area in 2024 (and extending from MD to OK, IL to LA),” Cooley said.
Cooley notes that periodical cicada emergences involve several million cicadas per acre. While that seems like a lot, Cooley says to remember that insects generally come in large numbers.
“That sounds astonishing…. But how many ants, mosquitoes, or flies are there in an acre? Insects come in large numbers. For larger broods, that means billions and trillions of insects will be out,” Cooley said.
Cooley says that the rareness of this year’s co-emergence is exacerbated by the fact that Brood 13 and 19 share a boundary.
“A co-emergence of 13- and 17-year broods that share a boundary is something that happens only every 30-60 years,” Cooley said. “To get another boundary-sharing co-emergence, you’ll have to wait until 2076 when Broods XIX and XIV will co-emerge.”
Cooley says that if you miss 2024, you’ll have to wait until 2037 for the co-emergence of IX and XIX or 2041 for the co-emergence of XIII and XXIII, with co-emergences also expected in 2063 and 2067.
Effect of the Co-emergence
While millions of cicadas will emerge this spring and summer, Cooley says that most people may not even notice a difference in their everyday life.
“Although it is a co-emergence year, that won’t mean there will be any more cicadas out in a given area because the 13- and 17-year cicadas do not overlap. Most people actually won’t even be able to tell that something special is happening,” Cooley said.
While the co-emergence will go unnoticed by some, Cooley says that, as part of the natural world, it’s important to understand cicadas.
“Cicadas are part of the natural world, and these species are millions of years old. They are a part of the forest. It’s important to understand how our environment works because in a certain sense, insects such as this are ‘canaries in the coal mine' that tell us something about forest health,” Cooley said.
Jones says the effects of the co-emergence can be looked at from a human perspective and an environmental perspective.
"As for residents, impact of the Brood XIX emergence will be somewhat dependent on where folks are located and how much time they spend outdoors. Male periodical cicadas have a tendency to congregate in wooded areas where they will all ferociously call hoping to attract females so the more wooded an area, the more this will likely impact your serenity," Jones said.
"From the perspective of the ecosystem, this is a huge event. These animals have been living underground, slowly soaking up nutrition and building biomass for 13 years, way longer than the average insect lives. When they all emerge at once, it’s time for many predatory and scavenging critters to feast," Jones added. "Having the emergence occur is also a good sign that things haven't changed too much in the environment due to climate change or human modification of the habitat to prevent this wonderment from occurring."
Jones says that most cicadas limit their calling to daylight hours, so you don't have to worry about being kept up at night by choirs of mating cicadas.
How to spot Annual and Periodical Cicadas
While the annual cicadas and periodical cicadas may be out at the same time, there is one notable feature that may help spot.
One way to distinguish annual cicadas from periodical cicadas is with the color of their eyes. Annual cicadas typically sport black or green eyes, while periodical cicadas typically boast bright red eyes.
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