During that time the males and females mate and the females lay the eggs that are the start of the next generation. Eggs are laid into the small twigs of trees and shrubs. The eggs hatch after 6 to 7 weeks and the newly hatched nymphs fall to the ground, burrow until they find a suitable tree root, and begin the feeding. The third special feature of periodical cicadas is the incredible noise for which they are known. The incessant buzzing sound is produced by two shell-like drums located along the sides of the abdomen.
Strong muscles vibrate the drum membranes several times per second.
And finally, periodical cicadas can occur in numbers that stagger the imagination and repulse the squeamish. Populations can reach up to a million and a half cicadas per acre. That can mean as many as 40,000 cicadas per tree. Witnessing a massive emergence of periodical cicadas takes patience and planning but is worth the wait. Iowa State University , Ames, Iowa.