Art Silverman, NPR
Smithsonian entomologist Nathan Erwin holds a cicada up to the microphone.
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The Brood X cicadas have emerged, and many residents in 15 states and Washington, D.C., are waking up in the morning to the roar of hundreds of millions of insects looking for love.
In a busy cicada area, it's estimated there are one-and-a-half million cicada nymphs per acre. The subspecies of cicadas known as Brood X has been underground for the last 17 years, tapped into tree roots, feeding and fattening up. Somehow — and no one's sure how — these insects know when it's time to surface and become adults. So in the last year of their 17-year life cycle, when the soil temperature reaches about 64 degrees Fahrenheit, they crawl out of the ground by the billions.
Their goal is to find a vertical surface to climb up; they need to hang vertically so they can split their exoskeletons. Out comes the adult, which unfurls its wings and flies around looking for a mate. The male cicadas do the wooing with a mating calling that, in large numbers, comes across as a high-pitched roar.
After they mate, the females lay eggs in trees and the adults die. Once the eggs hatch, the larvae drop to the ground and burrow into the soil. In 2021, the cycle will repeat.
NPR's Melissa Block talks with Nathan Erwin, an entomologist at the Smithsonian's Museum of Natural History and Scott Harvey, an acoustical consultant with the company Polysonics, who has measured the noise levels of the cicada ruckus.