WHEATON, Ill. (AP) 鈥� The most noticeable part of the blanketing the central United States is the sound 鈥� an eerie, that gets in a person's ears and won't let much else in.
鈥淚t鈥檚 beautiful chaos,鈥� said Rebecca Schmidt, a U.S. Department of Agriculture research entomologist. 鈥淚t does make this kind of symphony.鈥�
The songs 鈥� only from males 鈥� are mating calls. Each 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 its belly.
鈥淭he one we鈥檙e hearing the most is the cassini, a buzzy trail that goes up in a wave and is coming back down,鈥� Jennifer Rydzewski, an insect ecologist at DuPage County Forest Preserve, said in an interview in a clearing near a bunch of trees.
鈥淎nd every time it goes up in a wave and comes back down, you鈥檒l see in the treetops a bunch of them start flying out, so they鈥檒l make a call and then jump to a new branch and make the call again. So it鈥檚 actually like different groups that are coming in waves.鈥�
The other one is a 鈥渃onstant whirring hum, which is the pharaoh's staccato鈥� and every now and then an individual call that sounds like 鈥渆ee-ooo鈥� can be heard, she said. Others have said the sound is more like 鈥渇ffaaaro, fffaaaro."
The sound comes from a white membrane on the male's midsection that is made to vibrate, Schmidt and Rydzewski said. The area beneath it acts like an echo chamber.
鈥淚t鈥檚 a lot of the same sort of physics as an instrument,鈥� Schmidt said. 鈥淪o if you think about like a drum, you can have a pretty small drum that is being hit by somebody that鈥檚 not hitting it that hard, and it still makes quite a lot of noise."
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By Seth Borenstein, The Associated Press
