Noticing more cicadas this year in the U.S.? There may be a reason

Noticing more cicadas this year in the U.S.? There may be a reason

Some Americans are getting a preview of summer 2024, when two periodical cicada broods will emerge simultaneously for the first time in 221 years—an event rarer than Halley’s comet.

Published September 5, 2023

6 min read

Growing up in Taiwan, Michelle Wong always marked the start of summer by one thing: the steady hum of cicadas.

“I always loved to hear them,” she says, adding that the noise was also a sign they were ending the school year.

Now 54 and a photographer living in Austin, Texas, Wong still spends her summers listening to the song of the cacophonous insects. Wong photographs cicadas near her home and posts the images to citizen science apps, some of which are even cicada-specific, like Cicada Safari.

Many of these sightings are of annual cicadas, potato chip-size insects with green-tinted wings that pop out of the ground, usually starting in June. They’re a different beast from periodical cicadas, red-eyed animals that emerge from the soil in the millions to create an ear-splitting chorus of clicks for about a month before they die.

Fifteen different periodical cicada groups, or “broods,” live in forests across the eastern U.S., emerging in 13- to 17-year cycles. In 2024, two of these groups—Brood XIII and Brood XIX—will steal the show, emerging simultaneously for the first time in 221 years, an event rarer than Halley’s comet.

However, some of these cicadas are making their appearance in summer 2023, a year early, according to research from Mount St. Joseph University in Cincinnati. On Cicada Safari so far in 2023, users have reported at least 700 periodical cicada stragglers; they recorded more than 400 in 2022.

It’s not completely unheard of for the insects come out early, even up to four years ahead of schedule. But scientists are warning that early cicada emergences could become more frequent as climate change ushers in earlier springs and longer periods of warmth.

“The question is, are these reports just simply more common now because of the internet? Or is there something biologically going on where there are more cicadas?” says John Cooley, an entomologist at the University of Connecticut whose periodical cicada mapping project was initially funded by the National Geographic Society. (Learn how insects are disappearing at an alarming rate.)

To find answers, Cooley compiles yearly data from the research community and citizen science apps to map how broods are changing over time—and he’s received more records of cicadas emerging “off-cycle” in recent years than ever before.

Climate connections

A periodical cicada’s existence is intimately intertwined with the forests that surround it. During its brief foray above the surface, an adult cicada will lay 400 to 600 eggs in the tree branches. Eventually its offspring will hatch and fall from their perch into the soil, where they will dig down and spend most of their lives. But how do they track the passing of time and know when to emerge?

“It’s a huge mystery,” says Chris Simon, an evolutionary biologist from University of Connecticut who specializes in cicadas. The leading theory is that these insects have an internal molecular clock synced to the seasonal flow of fluid, or xylem, that passes through a tree’s roots each spring, which cicadas sip on as food.

But, due to climate change, spring in North America is starting earlier: Some areas in the Midwest and Northeast, including New York City, saw some of the earliest spring leaf and flower blooms on record in 2023, according to the USA National Phenology Network. That’s lengthening the growing seasons of the trees that feed the cicadas, possibly providing extra nutrients that cause the underground bugs to mature faster, according to John Lill, a cicada researcher and biology professor at George Washington University in Washington, D.C.

After a cicada reaches its final stage of development, it will only emerge when the soil temperatures reach roughly 65 degrees Fahrenheit, which is normally during late April or early May. But earlier springs could lead to warmer temperatures than before, prompting cicadas to emerge ahead of time.

Most of the time, off-cycle cicadas are scarce and quickly gobbled up by predators such as birds. However, in recent years, scientists have identified larger groups of stragglers than before; in 2020, a large group of Brood XIII were reported in Chicago and several other states, four years ahead of time. (Read: Nature is out of sync, and that’s reshaping everything, everywhere.)

“The question of whether or not the cicadas are going to be able to keep pace with the pace of climate change in terms of their evolutionary responses is an open one,” Lill says.

The cicada network 

The popularity of cellphones and social media have allowed cicada researchers to pull data from a network of citizen scientists to precisely track these loquacious insects.

“The one lone researcher poking around the forest is limited by the amount of territory you can cover. You can now tap into large amounts of the population and get a better idea” of what’s going on, says Elias Bonaros, a 50-year-old New York City cardiologist who first connected with Simon when he was a curious boy of seven years old.

Bonaros now helps run a Facebook group, the Cicada Discussion, Science and Study Group, with nearly 2,000 members that’s dedicated to cicada spotting and identification.

Another popular app for cicada enthusiasts is iNaturalist, a joint initiative of the California Academy of Sciences and National Geographic Society, where Wong has already uploaded more than 103 annual cicada shots in 2023. (Read why citizen science has surged since the pandemic.)

Cicada Safari has amassed more than 551,000 photos of periodical cicadas from users across the country since it was founded in 2019. These images help scientists determine trends in periodical cicada populations, according to Gene Kritsky, a professor emeritus at Mount St. Joseph University in Ohio who helped create the app.

“It’s like a big science experiment in your backyard,” Kritsky says.

Next year, the apps will likely see even more activity as Brood XIII surfaces across the midwestern U.S., while Brood XIX is expected to spread mostly across southern states such as Alabama and Arkansas.

“Nobody else in the world has anything quite like this, just for the scale of what’s going to happen next year,” Cooley says.

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