Children ask: What ever happened to those cicadas?

Four second-graders at Robert Crown School in Wauconda were wondering about cicadas. Here's what they wanted to know:

Claire Hansen : "Are the cicadas going to be alive in 2009?"

Mackenzie Zehner: "Are the cicadas dead?"

Lauren Lehner: "Why do cicadas only come every 17 years?"

Vanessa Kaye: "Are there still cicadas outside?"

Cicadas are dark colored insects with very large wings and red eyes. They grow to about one-half inch in length. They don't bite or sting. They have a very distinctive chirp that sounds like a chorus of buzz saws. When the 13- and 17-year cicadas swarm the land, the chirping can be quite loud.

Nature can be as weird as a plot in a sci-fi thriller. In May, billions of cicadas emerged from underground burrows. In some places, so many were present that they covered sidewalks and lawns.

There are two main types of cicadas. Annual cicadas, also known as dog day cicadas, appear every year, while periodic cicadas remain underground for 13 or 17 years and then appear. Both types burrow underground, emerge as nymphs, shed their outer shells and live outside as adult bugs.

Doug Taron, curator of biology at the Peggy Notebaert Nature Museum in Chicago, said the annual cicadas, the ones that emerge every year, will be alive in 2008 and 2009 and every year after.

The Magicicadas, those that only appear every 17 years, won't be seen until 2024. But both types are alive and well right now -- underground, as nymphs.

Are they dead?

"The cicadas that everybody saw outside are all dead," Taron said. "They have a very short life span of about one and a half months. But they are alive underground for 17 years."

Why 17 years?

"The 17-year and 13-year (cicadas) take a very, very long time for emergence as adults," Taron said. "This is an adaptation that allows cicadas to avoid predators."

Are there still cicadas outside?

"Baby cicadas are outside. All are underground. They will become adults next summer when they emerge," Taron said.

Here are some more facts about cicadas. The babies burrow near tree roots so they can feed on tree sap while they remain underground. The burrows can be up to a foot deep. Once they emerge, they shed their shells and begin their lives on top of the earth as adults.

Only the males chirp, a sound made from a special spot in their abdomen by rubbing their wings together. This is the way they attract a mate. Once they find a mate, the female cicada makes slits in a tree branch and deposits up to 600 eggs. It takes four to six weeks for the nymphs to hatch, then they drop to the ground and burrow underneath the tree.

The 13- and 17-year cicadas are only known to exist in the U.S., in some northern states and some southern states, all east of the Mississippi River.

There are benefits to the mass invasion of cicadas. They loosen the soil to allow for more plant growth, their annoying habit of laying eggs in tree branches is a natural way of pruning, and they are food for larger insects and other animals.