Like a scene from a science-fiction movie, red-eyed insects are popping up now in freshly turned gardens, squirming beneath logs and stones and digging tunnels as they plot their escape.

After a 17-year wait, a few cicadas are making an early break from the subterranean world. If scientific predictions hold, the insects will appear en masse in the Chicago area May 22.

For now, if you flip a log or stone in the Fullersburg Woods Forest Preserve in Oak Brook, you may see scores of the cicadas, still in a nymphal stage, along with even more of the half-inch holes they're digging -- some at the end of chimney-like protrusions from the soil.

In Wilmette, Martha Hellander was moving a steppingstone in her garden last week and was shocked to find 17 tan-colored cicada nymphs underneath.

"It was really creepy," said Hellander, 54, who moved into the home 16 years ago, one year after the last appearance of the insects that emerge only every 17 years. "I sort of screamed and dropped it and then I went back, because I was curious. There were so many of them."

Some nymphs also have been seen emerging in the Wonder Lake yard of a gardener volunteer for the University of Illinois Extension. That's typical, said Phil Nixon, an extension entomologist. A few cicadas always come before they're expected or up to a year afterward.

"There always are a handful of early emergers, and of course they're going to be nailed by birds right off the bat," Nixon said. "There's not that many, so they're going to get picked off."

Exactly why and when the full swarm of cicadas will emerge -- in densities of up to 1.5 million an acre -- is one of nature's mysteries. The best scientists can tell is it's a combination of factors including the weather, the length of the day and the ground temperature.

Using a formula based on April temperatures and projections of when the soil will reach a temperature of 64 to 65 degrees, Gene Kritsky, an entomologist at the College of Mt. St. Joseph in Cincinnati, predicted the exact date of the emergence of the same species of cicada in Ohio three years ago: May 14. He had set up 15 monitoring stations around Cincinnati and watched.

"It was like clockwork," said Kritsky, one of the nation's leading cicada experts.

Applying that formula to northern Illinois, Kritsky says cicadas should emerge here in late May. But in 1990 cool weather delayed the full emergence in the Chicago area until early June.

When the time comes, the cicadas will emerge for about two weeks, said Kritsky, but a steady rain coinciding with the soil reaching the right temperature will drive them out quicker.

"If you have a nice, good rain to soften the soil, then they'll come out in droves," he said.

The batch expected this year is called Brood XIII and its days are numbered. Seventeen years ago they hatched as ant-sized nymphs and then grew through five juvenile stages about a foot underground, feeding on tree roots and wintering below the frost line.

Before long, the inch-long nymphs will emerge, find a nearby leaf and molt to become hard-shelled, black adults. They don't bite or damage property, but they'll make a tremendous racket as they desperately look for mates. A few weeks later, they'll die.

Allison Lehnen, an environmental educator for the Lake County Forest Preserve District, said she's seen woodpeckers poking their beaks into the ground in her Mettawa back yard and eating bugs that have been tunneling their way to the surface.

"You could see them dig in a spot and then get one and gobble it down," Lehnen said. "They're getting closer."

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jbiemer@tribune.com

cflynn@tribune.com

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