From mapping cicadas to measuring sound, researchers track the brood around St. Louis (2024)

ST. LOUIS — Cicadas, it turns out, are in some unexpected places across the region. Forest Park, yes. But also where the Pruitt-Igoe housing complex once stood in north St. Louis.

They seem to have reached their peak. And their noisy vibrations appear to be annoying humans — and, possibly, other animals that rely on sound to communicate.

As residents across the region fight to avoid — or marvel at — this year’s wave of a half-trillion periodical cicadas, researchers here are tracking their movements and finding some early and surprising trends.

“It’s interesting how patchy they are,” said Robbie Doerhoff, a forest entomologist for the Missouri Department of Conservation.

Generally, experts said the bugs’ whereabouts can mirror development trends as they can be harder to come by in densely urbanized places and far more prolific in bigger, more undisturbed pockets of greenery such as parks, cemeteries and areas outside the city.

And although the data are still coming together, early glimpses of the trends offer some surprises — and paint a more complex picture than a stark urban-suburban-rural divide in cicada density.

For instance, plentiful cicadas can be found in Benton Park but not in the adjacent neighborhood of Soulard, said Aimee Dunlap, a biology professor at the University of Missouri-St. Louis and co-director of its Whitney R. Harris World Ecology Center.

And in some previously densely developed places — like the partially forested site of the former Pruitt-Igoe apartments, which were demolished in the 1970s — cicadas have been found at some of the greatest densities of anywhere in the region, on par with the hot spot seen in Forest Park’s Kennedy Woods, said Dunlap. The periodical cicadas emerge by the billions every 13 years.

“We’re seeing cicadas all around (Pruitt-Igoe) — that was a surprise for me,” said Dunlap. “They’ve not had very many generations to make it there, but they are dense and they are spilling over into all of the surrounding areas.”

Seeking the public’s help

Using an app called Arduino Science Journal, Dunlap and some colleagues are harnessing help from the general public to track where they encounter the cicadas during their long-awaited but short-lived emergence. Similar mapped-out data on cicada distribution can be found through other websites and digital formats, such as iNaturalist.

Of course, it can often be even easier to hear the cicadas than to see them, as males buzz loudly to attract mates.

And researchers, including Dunlap, are even using the insects’ tinny, pulsating din to help quantify their abundance — combining visual observations with decibel readings from audio recordings.

She’s not the only local scientist lending an ear to the insects.

At five sites around the region, Kasey Fowler-Finn, a biology professor at St. Louis University, is examining how the cicadas’ ruckus might affect communication by other species.

Do cicadas stop birds from singing?

“You have this massive influx of singing that can be extremely loud,” said Fowler-Finn. “What does that do for birds that are trying to communicate with each other or other insects that are using airborne sound?”

With data collection ongoing, she doesn’t have any findings to share yet but suspects that sonic communication from other species could indeed be altered by this year’s noisy newcomers — much the way humans might need to pause their own cellphone conversations when the outdoor volume of the bugs crescendos.

“You’re unlikely to continue your conversation,” she said. “I would imagine that animals have a similar problem.”

She said that depending on their density, the sound from cicadas can reach 100 decibels or higher — “enough to make it hard to think,” she added. For comparison, a jackhammer or rock concert registers about 100 decibels.

Fowler-Finn also wonders if cicadas might communicate in more ways than meet the human ear. For example, she studies animal species that communicate by sending vibrations through plants or trees — the second-most common form of communication in the animal kingdom behind chemical signaling, she said — and expects that cicadas could employ similar tactics alongside their audible calls that transmit sound over longer distances.

It’s hard to say if the region has hit its “peak” for cicada activity as the bugs emerged in different places at slightly different times based on soil temperatures. But experts generally said that virtually all of the periodical cicadas have emerged by now and that the region could currently be experiencing the maximum volume as males only start buzzing after their new exoskeletons have hardened.

The clock is ticking in their rush to mate and create the next generation of cicadas, soon to begin another 13-year burial. Experts said the region’s above-ground ranks of the cicada brood will probably disappear in the next couple of weeks or so.

And although a flood of published research and academic findings are sure to follow in their wake, some individuals — like Dunlap — will miss the bugs themselves.

“They’re super cool insects,” she said. “I’m definitely going to miss them when they’re gone. I know that’s not true for everyone, but I love ’em.”