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, as larvae. They emerge as adults to molt and reproduce. Some appear every year, while others, called cicadas “periodicals”come out of the ground every 13 or 17 years.
This year, the phenomenon involves two groups of cicadas: group XIX, which emerges every 13 years and has already started to do so in North and South Carolina (southeast). It will be followed by Group XIII in the Midwest, which emerges every 17 years. In central (northern) Illinois, both could be present in the same location. A phenomenon that we remember, and whose stories are passed down from generation to generation. Just like, for example, witnessing an eclipse.
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Favorite prey of birds, foxes, raccoons and turtles
“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 anyone can collect data on these red-eyed critters. “That’s what science does: you make hypotheses that lead you to predictions, the predictions are verified, (…) it has value, at a time when some people seek to discredit science”notes Gene Kritsky.
Without much defense, cicadas “periodicals” rely on their numbers for the survival of the species: thanks to the hordes that surge at the same time, birds, foxes, raccoons, turtles and other predators are quickly satisfied, explains John Lill, professor of biology at George Washington University . In a study published recently in the journal Science, John 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 — neglected by the birds, which focused 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 cicadas appear”adds John Lill.
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Climate change disrupts cicadas
Then there is the singular – and shrill – sound of male cicadas mating. “We have had several calls regarding a sound that sounds like a siren, wailing or roaring”the Newberry Sheriff’s Office in South Carolina (southeast) said 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 indicated “and, eventually, that this trait will be assimilated genetically”.
It’s unclear what this means for the species in the long term. Likewise, reports Mr. Lill, to know the impact – positive or negative – that the transformation of the land since the colonial era has had on the cicadas. On the one hand, many historical species have disappeared due to deforestation, but those that remain thrive in suburban suburbs that provide ideal conditions for females to lay their eggs.
