USA: why billions of cicadas will soon invade the country

Entomophobes will not like this news. Billions of cicadas are preparing to invade America’s forests and suburbs in the coming weeks due to the meeting of two specific groups of cicadas that will frolic at the same time. A phenomenon that has not happened since 1803.

The cycad family includes more than 3,000 species of insects around the world. Most of them spend their lives underground, as larvae. They emerge as adults to molt and reproduce.

“Periodic” cicadas

Some appear every year, while others, called “periodic” cicadas, appear every 13 or 17 years. There are two groups of cicadas participating in the phenomenon this year: Group XIX, which appears every 13 years and has already begun to do so in North and South Carolina (southeast). It will be followed by Group XIII in the Midwest, which appears every 17 years. In central (northern) Illinois, both may be present in the same location.

“When they come to the surface, they do so in large numbers, which is exciting for parents and children,” says entomologist Gene Kritsky of Mount Saint Joseph University, who has developed an app that allows anyone to collect data on these red-eyed critters.

A phenomenon that we remember and whose stories are passed on from generation to generation. Just like, for example, witnessing an eclipse. “This is what science does: you make hypotheses that lead you to predictions, the predictions are tested, (…) this has value at a time when some people seek to discredit science,” notes Gene Kritsky.

Scientific miracle

Without much protection, periodical cicadas rely on their numbers for the survival of the species: thanks to the hordes growing at the same time, birds, foxes, raccoons, turtles and other predators quickly become saturated, explains AFP. John Lill, professor of biology at George Washington University.

In a study published recently in the journal Science, John Lill and colleagues show that a cluster of cicadas that emerged in Washington in 2021 led to an increase in the number of caterpillars abandoned by birds that focused on the cicadas. Result: increased consumption of young oak shoots.

Other studies show that the years when oak trees produce the most acorns always follow two years after the cicadas emerge. The more acorns there are, the larger the population of mammals that feed on them grows, the higher the risk of Lyme disease in humans.

The phenomenon “shows that there are potentially long-term ecological consequences that will be felt for many years after the cicadas emerge,” Mr. Lill adds.

Changing of the climate

Then the strange sound of male cicadas mating is heard. “We have received several calls regarding what sounds like a siren, howling or roaring,” the Newberry Sheriff’s Office in South Carolina (Southeast) posted on Facebook this week. According to Chris Simon, a researcher at the University of Connecticut, climate change is disrupting the cicadas’ internal clock.

Given global warming in the United States, longer plant growing seasons provide more food and faster growth for cicadas. “I predict that more 17-year cicadas will turn into 13-year cicadas,” she said, “and eventually the trait will be assimilated genetically.” “It’s difficult to know what this means for this species in the long term,” he adds.