The 17-year cicadas are returning to the Midwest after spending the better part of the last two decades drinking sap off of tree roots.

For those of you who don't remember the last cicada invasion of 1990, they will be everywhere, they will be huge, and they will buzz around like millions of old 747 airplanes.,”

The cicadas are coming!

The 17-year cicadas are returning to the Midwest after spending the better part of the last two decades drinking sap off of tree roots.

For those of you who don't remember the last cicada invasion of 1990, they will be everywhere, they will be huge, and they will buzz around like millions of old 747 airplanes.

For those of you who do remember them, the ones coming out late May to mid-June are the offspring of that generation.

A group of cicadas is called a brood. The cicadas of 2007 are a part of the Brood XIII.

They are between one and two inches long, but don't fear if they land on your leg. They are perfectly harmless.

According to Gene Kritsky, professor of biology at College of Mount St. Joseph in Cincinnati, cicadas emerge when the ground temperature reaches 64 degrees. Kritsky developed a formula to hypothesize when the cicadas would come up from the ground. If it is a cold spring, the insects will come out later in the summer.

Kritsky said he expects the cicadas to appear on May 22.

In 2004, his formula predicted the exact day the cicadas emerged from the soil. They were a part of another brood that emerged in Ohio and on the East Coast.

Cicadas that are around every year are called annual cicadas. Kritsky said those cicadas are under the ground for five years with different groups of them coming up every year.

The 17-year cicadas come up using the strategy of safety in numbers.

"They emerge in great numbers to overwhelm their predators," he said. "Their predators get sick of them and the cicadas can then mate in peace."

The insects will be around for six weeks and will finally die after laying their eggs on the trees.

The eggs hatch and the larvae fall to the ground where they burrow into the soil. They spend the next 17 years not moving any farther than one yard.

"Sometimes I dig them up," Kritsky said. "I just cannot wait for them to come up."

The Southern Wisconsin Butterfly Association will take a field trip to observe the cicadas.

"We hope it will be an experience," said Karl Legler, vice president of the group. "We want to see tons of them and hear the noises."

Legler said they are going to investigate where cicadas are likely to be before choosing a place to observe them.

"You can easily miss them if you do not go to the right area," he said.

The sheer mass of cicadas can be frightening to the casual observer but they do not cause much damage to trees or other animals, said Dan Mozgai, founder of cicadamania.com.

Mozgai started the Web site in 1996 after cicadas invaded his friend's wedding.

"People had a fun time with it at the wedding," he said.

Since the wedding his Web site has gotten a considerable amount of attention. It had nearly 50,000 hits in one day in 2004, attention that keeps Mozgai going.

"One guy always asks me where the cicadas will be this year, then goes there and sends me pictures of him eating them," he said. "It kind of grosses me out."

It is true, cicadas are edible – in fact Mozgai said he heard they taste like shrimp.

When you see them on May 22, do not be afraid. They will not eat your children, your dog can eat them and although they are loud, appreciate them, because the next time you see them we will all be 17 years older.

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