May 25, 2004

Contact: Roger Martin, KU Center for Research, (785) 864-7239.

Cicada's call serves important function, says KU professor

LAWRENCE -- Periodical cicadas are hatching in the eastern United States this month, but Kansans must wait till 2015 for another visitation by the noisy insect that reappears every 17 years.

Cicadas make a fierce racket, as anyone who has lived through a summer of their singing knows. They make it by buckling the ribbed membranes on their bellies.

The sound is broadcast to the outside world through the cicadas' ear drums, according to Michael Greenfield, University of Kansas professor of ecology and evolutionary biology and an expert on insect sound.

"This implies that cicadas are largely deaf during their singing," Greenfield said.

The sound is a call to sexually receptive females. Greenfield said, "Evidently female cicadas don't perceive the sound as awful."

A single cicada isn't even all that loud, he said.

"The numbers and density of cicadas are so great that the sound from the chorus can be intense," he said. "It's the stadium effect."

In fact, the loudest insect in Kansas is actually a katydid, the robust conehead, Greenfield said. At about a yard away, its sound is in the 90 decibel range -- the level produced by a motorcycle.

"You wouldn't want to be sitting immediately next to one all evening," Greenfield said.

The world's loudest insects are the Australian bladder cicadas and the bladder grasshoppers of South Africa, Greenfield says. They're about 10 decibels louder than the Kansas katydid and audible more than half a mile away.

The May emergence of cicadas in the eastern United States involves a group called Brood 10. Kansas cicadas, which emerged in 1998, belong to Brood 4.

Brood 4 cicadas range from Illinois to central Kansas -- the western edge of periodical cicada range.

If a male cicada's love call appeals to a female, Greenfield says, she replies with a flicking of wings. He approaches and courts.

If refused, he flies a short way and starts in again, much as male fireflies will.

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