Why are there so many cicadas this year?

Ask Tom Why

Dear Tom,
Why are there so many cicadas this year?

Marianne Johnson Western Springs; Yolanda, Brookfield; Carol Caruso, Mark McCauley

Dear Marianne, Yolanda, Carol, and Mark,
The Chicago area’s “big” cicada event is the 17-year cicadas, and those will not arrive until 2024, having last emerged in 2007. These cicada life cycles are genetically driven and not affected by weather, though the nymphs emerge in spring when the soil temperatures reach 64 degrees. They are about 4 centimeters long, and while deafening and overwhelming in numbers, they do not sting or bite. However, this area also hosts “annual” cicadas, ones with non-synchronized, multiple-year life cycles where adults emerge every year. The cicadas that are currently emerging are a sub-brood of the 17-year cicadas, known to arrive four years earlier in a 13-year cycle.

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