Prepare for an invasion last seen when Bill Clinton was president. 

Entomologists anticipate an enormous brood of 17-year cicadas emerging from extreme North Georgia all along the East Coast. 

"In places where they're going to be present, there could be as many as one billion per square mile," University of Maryland entomology professor Michael Raupp explains.

Professor Raupp says cicadas are noisy but harmless.  "They can sing at about 90 decibels (which is) about the same volume as a jet aircraft taking off or a really loud lawnmower," he points out.

The intrusion is not long-lasting.  Adults live only two to four weeks above ground, just long enough to breed the next 17-year cycle.