The Seventeen-Year Roar
Every seventeen years, billions of insects crawl out of the ground at once across the eastern United States, and fill the air with a deafening roar.
What was reported
Periodical cicadas spend seventeen years underground as nymphs, feeding on tree roots. Then, in a single spring, they all emerge together: up to a million per acre. In 2021, Brood X came out across fifteen states, from Georgia to New York.
The males sing in chorus, making a whirring, pulsing roar that can reach the volume of a lawnmower and goes on for weeks. Early settlers mistook them for the plagues of locusts in the Bible, and some saw them as an omen.
Explanations offered
Emerging in such vast numbers means predators can't eat them all, and their prime-numbered cycles may help them avoid predators on shorter cycles. How they count the years is still not fully understood.
- When
- Every 17 years, most recently 2021
- Where
- Maryland, USA
- Witnesses
- Millions of people in the eastern United States
- Status
- Explained
Famous cases are real, widely reported events. Each file sets out what witnesses said and the explanations that have been offered, without taking a side.
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