Researchers prepare for 17-year cicada onslaught

		May 14, 2004

	Research
	Researchers prepare for 17-year cicada onslaught Brood X cicadas will cause limited damage to trees, yard plants Ties that bind

By John R. Hughey

Photo by Chris Meyer

Melanie Hunter, managing editor of the Kelley School of Business publication Business Horizons, surveys the cicada towers beneath the deck of her home on the east side of Bloomington.

Newspaper headlines read like horror film titles: Day of the Cicada, Cicada Mania and Here Comes Brood X.

Periodic cicadas are this year’s media darlings, a peculiar phenomenon ripe for hyperbole. Indiana University Bloomington is emerging as one of the staging grounds for environmental research surrounding their arrival.

Leading a bulk of the Bloomington research is Keith Clay, director of the university’s research preserve. Over the past several summers, with help from college students and research assistants, this biology professor roamed southern Indiana digging holes, scooping dirt, plucking out bugs and then tallying his finds in an attempt to identify regions where the cicadas are most heavily entrenched.

“People don’t find it odd that I’m out digging bugs,” said Clay, adding that any lingering reservations disappear after he shares what type of bug he’s after. “Old-timers remember the 1987 outbreak.”

And so does Clay.

Clay describes the insects’ arrival as a virtual invasion. After emerging from underground, the cicadas begin their mating ritual, producing roaring chirping calls and carving notches into tree limbs for egg depositing. The event sounds rather harmless until Clay shares the magnitude of a million-or-so chirping insects covering the ground, climbing trees and carving slits into branches.

“I remember walking down by Lake Griffy and being overwhelmed by the sheer volume. I couldn’t take it. The sound was deafening,” said Clay, remembering the cicada’s last emergence in 1987, which happened to be Clay’s first year at IU. “If you were driving, it was difficult to stop because the roads were so slick from squashed cicadas.”

These insects appear every 17 years, climbing out from their underground burrows after living off tree roots for nearly two decades. Once ground temperatures reach at least 64 degrees most likely during May—watch out: Mating season is in full swing for several million or so cicadas. After the mating frenzy, eggs are deposited in tree branches, the 2004 brood dies off and the new batch burrow underground, waiting another 17 years before repeating the cycle.

The event is so grand, Clay compares the emergence to a natural phenomenon. Marveling at the scale, he says the cicada bio-mass exceeds any wild animal—measuring 1,000 cicadas per meter. “It’s kind of like the salmon that go upstream—there’s safety in numbers.”

Researchers have tapped into the community’s collective memory of past outbreaks in counting and sharing information on where the cicada outbreaks are heaviest. A Web site was created to help in gathering data.

http://www.indiana.edu/~act/cicada/

In addition to community recruits, ground zero for cicada research is Naval Surface Warfare Center, Crane Division, a 30-minute drive from the IU campus. Jim Speer, a professor in the department of geography and anthropology at Indiana State University, has teamed with Clay in researching the environmental impact created by the cicada emergence. Clay also is focusing research at the IU nature preserve. Untamed patches of forest underbrush are prime cicada breeding ground, due to plenty of small trees that are preferred by egg-laying cicadas. During the past several years, Clay and his team of graduate student researchers have attempted to gather information on how many cicadas will emerge. Now, during the current emergence, they will document the potential environmental impact.

One of the techniques Clay is employing is a netting patchwork over underbrush. Alternating between covered trees and uncovered, researchers will be able to gauge the result of cicada egg-laying. Trees preserved from cicadas can be compared to the trees chosen for egg depositing.

One theory Clay hopes to research revolves around the idea that a community’s growth and development alters the cicadas’ habitat. Cicadas usually choose trees and shrubs offering smaller branches while avoiding dense forests. Early data from Clay’s past summer digging exhibitions seem to support this idea. A housing development just east of Bloomington produced the highest concentration of cicada larvae, said Clay. During the 1987 outbreak, trees in this particular neighborhood were new. Just-planted trees and shrubs were inviting to egg-laying cicadas.

“They take a gamble when they lay their eggs. Are the trees still going to be there in 17 years? If the land is clear cut, the cicadas are toast,” said Clay, offering his take on one of the possible reasons cicadas prefer young trees over mature forest. “Bloomington has changed a lot (since 1987) and it will be interesting to see how that has affected the cicadas.”