May 18 (Bloomberg) -- In the past 17 years, ``Friends'' came and went on television, another George Bush was elected president and the Hubble telescope was launched. Seven billion cicadas missed it all.

Now the cicadas are ready to emerge from their 17-year sojourn underground and invade the Chicago area.

Tree owners and suburban homeowners are fretting as the periodical cicadas, the world's longest-living insect, prepare to crawl out for a monthlong breeding frenzy. Crowds of mating males roar as loud as a motorcycle, and females slit tree branches and small trunks to lay eggs.

The bugs will arrive as soon as next week, but they won't stay long.

``They'll all be gone by July 1, with dead bodies strewn all over the place,'' said Dan Summers, an entomologist for the Field Museum in Chicago.

The emergence in northern Illinois of cicadas, winged bugs about an inch (2.5 centimeters) long, is among the biggest in the U.S., Summers said. The bugs rise when ground temperatures reach 64 degrees Fahrenheit (18 Celsius).

Public gardens protect their trees by wrapping them in nets that look like wedding veils.

``We're really covering the entire tree and making sure there's no way the cicada can go inward to do its damage,'' said Tom Tiddens, plant health-care supervisor for the 385-acre (155- hectare) Chicago Botanic Garden in suburban Glencoe. The 1,700- acre Morton Arboretum in Lisle took similar steps.

Piles of Dead Bugs

Homeowners, meanwhile, are bracing for bug-infested cookouts. Cicadas most affect yards in suburban neighborhoods undisturbed by new construction. The cicadas can cover trees, bushes and cars, leaving residents to sweep or even shovel piles of dead bugs after the mating ends next month.

The cicadas have spent the past 17 years feeding on tree roots and creating tunnels for their exit. They inundate wooded areas without housing construction: Tiddens found 15 tunnels in one square foot at the Botanic Garden.

`They've been working their way up the last couple of weeks,'' said Doris Taylor, Morton Arboretum's plant information specialist. ``They're 5 or 6 inches from the soil line. If you stick a shovel in, you'll probably get two or three of them.''

Newborn cicadas arrive in about 10 weeks, drop to the ground, and restart the process.

Chicago, the third-largest U.S. city, is making the best of it. Morton Arboretum will hold lectures next week and offer programs for children to build cicada toys or noise makers. The Field Museum is opening an exhibit on cicadas today.

``It's kind of a neat experience,'' Tiddens said of the infestation. ``People shouldn't just hide inside. They should go and check it out, because we won't be seeing this for another 17 years.''

To contact the reporter on this story: Darrell Hassler in Chicago at dhassler@bloomberg.net.

Last Updated: May 18, 2007 01:00 EDT