How do cicadas make their signature sound, so eerie and amazingly loud?

WHEATON, Ill. (AP) — The most noticeable part of the cicada invasion blanketing the central United States is the sound — an eerie, amazingly loud song that gets in a person's ears and won't let much else in.

"It's beautiful chaos," said Rebecca Schmidt, a U.S. Department of Agriculture research entomologist. "It does make this kind of symphony."

The songs — only from males — are mating calls. Each periodical cicada species has its own distinct song, but two stand out: those of the orange-striped decims or pharaoh cicadas, and the cassini cicada, which is smaller and has no orange stripes on it...