Two broods of periodical cicadas, Brood XIII and Brood XIX, are expected to emerge at the same time in a dual emergence event across 16 U.S. states, resulting in more than a trillion cicadas buzzing around the Midwest and Southeast of the country this spring. The two broods belong to distinct groups of Magicicada, each with a 17- and 13-year life cycle respectively. This rare natural event, which takes place once every 221 years, will see both broods simultaneously tunnel through the ground to the surface from late April onwards. Experts have suggested that the dual emergence could lead to interbreeding between the two broods. This is according to The New York Times.
“Under just the right circumstances and with just the right number of individuals cross breeding, you have the possibility of the creation of a new brood set to a new cycle,” Floyd Shockley, an entomologist and collections manager at the Smithsonian National Museum of Natural History, told the Times.
Seven species of cicadas, known as periodical cicadas, spend the majority of their lives underground as nymphs and feed on sap that seeps from tree roots. Depending on the species, after 13 or 17 years of living in the dark, the insects use their front legs to burrow to the surface and transform into adults. The males produce a loud song by vibrating membranes on the sides of their bodies to attract mates, which can be louder than the sound of a plane in a chorus, according to The New York Times. After mating, females cut slits in tree branches to lay their eggs.
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Adult periodical cicadas live for three to four weeks before dying and never see their eggs hatch, which takes roughly three weeks. The newly hatched nymphs then drop to the ground and tunnel down into the soil to start the cycle again.
Brood XIII, which emerges every 17 years, and Brood XIX, which emerges every 13 years, will appear in a narrow strip across northern Illinois and eastern Iowa. Brood XIII, also known as the Northern Illinois Brood, will also be present in small areas of Wisconsin and Indiana. In contrast, Brood XIX, or the Great Southern Brood, will be widespread throughout the Midwest and Southeast.
The overlap zone is so narrow that the number of cicadas may not be noticeably bigger in Illinois and Iowa than in other states, said Gene Kritsky, a professor emeritus of biology at Mount St. Joseph University in Ohio and author of “A Tale of Two Broods: The 2024 Emergence of Periodical Cicada Broods XIII and XIX” (Ohio Biological Survey, 2024).
Kritsky informed Live Science via email that a single acre (0.4 hectare) of wooded land can house over 1.5 million cicadas. Unfortunately, deforestation has caused the destruction of much of the canopy needed for these insects to flourish.
As per Shockley’s statement to the Times, cicadas will gather in clusters in wooded areas and green urban spaces located near their emergence points. In urban regions, their corpses must be removed as they emanate an unpleasant aroma similar to that of decaying nuts.
The dual emergence event taking place this year is expected to continue until early July. Scientists strongly advise against disturbing the cicadas as they are beneficial to the ecosystem, harmless to humans, do not sting, and do not carry diseases.
When cicadas emerge, they create tiny holes in the soil which aerate it. Additionally, when females lay their eggs, they trim the branches of trees, resulting in the growth of more flowers and fruits the following year, Kritsky explained this to Live Science.
“The large number of adult cicadas provides a food bonanza to all sorts of predators, which can have a positive impact on their populations,” he said. “Finally, after the cicadas die their decaying bodies contribute a massive amount of nitrogen and other nutrients to the soil.”
“Don’t be scared of it,” Shockley told the Times. “Embrace it for the wondrous event that it is, and embrace the fact that it’s very temporary. It will be intense but short-lived.”
