Keith Clay remembers the late spring of 1987 well. His cat wouldn't eat, and the fish in nearby lakes and ponds wouldn't bite. The summer roads and sidewalks were as slick as the icy pavement in the dead of winter.\nWhat was the reason for these anomalies? \nFor the first time in 17 years, swarms of cicadas emerged from the ground in southern Indiana. And this spring, it's about to happen all over again.\nWith two pairs of wings, a set of compound eyes and more than 1,500 different species, cicadas have long been an object of fascination. They have been used in folk medicine, as food, as forecasters for changes in weather and war, and some species have even been caged for their melodic song. \nThe cicada population in southern Indiana, specifically the 17-year periodic cicada known as Brood X, has been a source of interest among scientists and non-scientists alike. It was this group of cicadas that was causing Clay, an IU professor of biology, such problems 17 years ago. But this time around, he is working on research with the IU Cicada Project, which studies the cicadas and their impact on forest succession in southern Indiana.\nAs the years go by, the subterranean cicadas move a bit closer to the surface each year, so by the 17th year, they are just under the soil and ready to emerge. For evidence of this, one only has to dig up a handful of dirt in the forested areas surrounding Griffy Lake to see the pale-colored nymphs, or insect larva, awaiting the hatch.\n"The goal of the (IU Cicada) Project is to investigate the importance of the periodical cicada on the forest ecosystem," Clay said.\nTo those who have never experienced the outbreak, as well as to those who have, the number of cicadas that emerge as part of Brood X can be overwhelming, to say the least. As Clay remembers, his cat was too busy feeding on the bugs and their dead carcasses to be bothered with any store-bought cat food set out for her. \nEric Garza, an IU graduate student, remembers one of the last outbreaks in the region. He said he and his friends used to "collect buckets full of them."\nThe periodic cicadas are different from the typical "dog day" cicadas -- the type that appear every year in late summer and create the constant dull hum that typifies a hot August day. Rather, the cicadas of Brood X are one of several broods that appear in late spring. Native only to the eastern regions of North America, the various broods of 17-year periodic cicadas differ from each other only in terms of the year and the region in which they emerge.\nUnderstandably, most people view the presence of cicadas as a once-in-17-year occurrence. Commonly forgotten, however, is the fact they are actually present in the environment, albeit underground, for all that time.\n"I'm really excited to see the emergence," said IU graduate student Adam Baumgart-Getz. "But for the first time in 10 years, I'll have time for fishing, and the cicadas will ruin it!"
The tree effect\nThis spring's generation of cicadas began their life cycle in the late summer of 1987. The cicadas hatched from their eggs, fell from the trees where they had been laid and burrowed themselves in the soils of the trees. Subsisting for 17 years on the sap and nutrients from the tree roots, these cicadas have been called the "Rip Van Winkle" of the insect world, which is somewhat of a misnomer since they don't spend their entire 17 years sleeping.\nDuring most of their time underground, the insects rarely move far from the point of birth, but for them to survive underground, they must build extensive cave-like networks in the soil.\nGiven their habit of laying eggs in the branches of trees, many scientists once thought the most damage was inflicted on the ecosystem during the year of emergence. But Clay, along with Jim Speer, a professor in the department of geography and anthropology at Indiana State University, is working on a study that has shown tree growth rates experience a sharp increase in the years of emergence and a gradual decrease in the years following, with the lowest growth rate occurring in the year just prior to the outbreak.\nSpeer and Clay have been working together on cicada research, both are interested in the effect the cicadas have on the forest ecosystem dynamics. Since they know exactly when the outbreaks occur, Speer, a dendrochronologist -- someone who uses tree rings to study past environmental events -- looks at the years in the tree rings to find any evidence of an impact from the cicadas.\nOne theory surrounding this growth rate phenomenon suggests cicadas inflict more damage on the trees while underground, where they act as a kind of leech, sucking the sap and other nutrients from the roots. But once they emerge from the ground and release their hold on the roots, the tree is able to grow more productively without the constant drain on its resources.\nStill, the damage inflicted on forests during the spring of emergence is not insignificant. Adept at slicing open the branches of young trees, the female cicada has a sharp tool-like organ that she uses to cut open a branch while simultaneously inserting her eggs into the newly-created gap.
Bug frenzy\nSo, why spend so much time studying a bug that appears only every 17 years? \nThough only appearing rarely, cicadas have been extensively studied by scientists because of their unique life cycle. However, there are aspects of this insect that are not as well-known. Clay hopes to fill in some of these gaps with his research.\n"Our project is not really on the insect itself but the impact," Clay said. "If all the cicadas disappeared from the planet, would it make a difference?"\nLuke Flory, a Ph.D. candidate in the biology department, worked on the IU Cicada Project during the summer of 2002. He examined the distribution of cicadas by digging up the soil and counting the number of nymphs present in a specific area. In about three to four gallons of unearthed soil, he would find up to 40 cicada nymphs. \nFlory recently witnessed the tail-end of an outbreak of 13-year cicadas in nearby Green County, but he's looking forward to the outbreak here. Flory said if he wasn't already going to be living in Bloomington this June, he and his wife had planned to come back just to witness the event.
Cicada symphony\nBy early June, what should southern Indiana residents expect? \nClay said to watch Alfred Hitchcock's thriller, "The Birds," to get a frightening prospect for what's to come. For the entomophobics, people afraid of bugs, Clay promises, unlike the birds in Hitchcock's film, the cicadas won't attack.\nBut one of the mysteries of this unique insect still remains unsolved. Now in the 17th year of their life cycle, through some unknown signal, the cicadas sense it is time to emerge. Scientists have yet to discover exactly what prompts the emergence of the insects. Some may emerge early and others late, but for the most part, they all emerge around the same time in late May and make their presence known with the arrival of their distinct, hypnotic whirr.\nAt his desk, Dan Willard, a professor in the School of Public and Environmental Affairs, recalls hearing the sounds of the cicadas. The male cicadas court their female counterparts through an insect song, and eventually, they all come together in a synchronic symphony of insect lilt.\n"The sound is a dandy," Willard said.\n-- Contact staff writer Katie White at kathwhit@indiana.edu.
