Noisy and ready to mate, billions of cicadas are preparing to invade American forests and suburban suburbs.
In the coming weeks, two particular groups of cicadas will frolic at the same time. A phenomenon that has not happened since 1803, when Thomas Jefferson was still president and the United States bought Louisiana from France.
The cicada family includes more than 3,000 species of insects around the world. The majority of them spend their lives underground, in the form of larvae. They emerge as adults to molt and reproduce.
Some appear every year, while others, called “periodic” cicadas, emerge every 13 or 17 years.
This year, the phenomenon involves two groups of cicadas: Group XIX, which emerges every 13 years and has already begun to do so in North and South Carolina. It will be followed by Group XIII in the Midwest, which emerges every 17 years. In central Illinois, both could be present in the same location.
“When they surface, they do so in large numbers, which excites parents and children,” according to entomologist Gene Kritsky, of Mount Saint-Joseph University, who developed an application so that everyone can collect data on these red-eyed critters.
A phenomenon that we remember, and whose stories are passed down from generation to generation. Just like, for example, witnessing an eclipse.
“That’s what science does: you make hypotheses that lead you to predictions, the predictions are verified, […] this has value, at a time when some people seek to discredit science,” notes Gene Kritsky.
A scientific marvel
Without much defense, the “periodic” cicadas rely on their numbers for the survival of the species: thanks to the hordes that surge at the same time, the birds, foxes, raccoons, turtles and other predators are quickly satisfied, explains to the AFP John Lill, professor of biology at George Washington University.
In a study recently published in the journal ScienceJohn Lill and his colleagues show that a group of cicadas that emerged in Washington in 2021 led to an increase in the number of caterpillars, abandoned by birds, which concentrated on the cicadas.
Result: consumption of young oak shoots has increased.
Other research shows that the years when oak trees produce the most acorns always follow two years after cicadas emerge. The more acorns there are, the more the populations of mammals that feed on them grow, the greater the risk of Lyme disease in humans.
This phenomenon “shows that there are potentially longer-term ecological impacts reverberating for years after the cicadas appear,” adds Mr. Lill.
Human impacts
Then there is the singular, shrill sound of male cicadas mating.
“We have had several calls regarding a sound that sounds like a siren, wailing or roaring,” the Newberry, South Carolina Sheriff’s Office posted on Facebook this week.
According to Chris Simon, a researcher at the University of Connecticut, climate change is disrupting cicadas’ internal clocks.
With global warming in the United States, a longer growing season for plants provides more food and faster growth for cicadas. “I predict that more 17-year-old cicadas will turn into 13-year-old cicadas,” she said, “and eventually that trait will be assimilated genetically.”
It’s difficult to know what this means for the species in the long term, Lill adds.