Periodical Cicadas

Description of periodical cicadas

Four characteristics of the periodical cicadas make them exceptional even by the standards of the incredible and fascinating world of insect species.  The first is the 13 and 17-year life cycles. The life span of 13 or 17 years puts the periodical cicadas among the longest-lived insects in the world.  All but a few weeks of those 13 or 17 years are spent as a nymph, 18 to 24 inches deep in the soil of wooded and forested areas, feeding on sap from tree roots. 

The second phenomenon is how all the cicadas in an area emerge at once in a highly synchronized fashion.  The nymphs develop slowly and at different rates, but they have all developed fully at the end of the 13 or 17 years and begin digging their way to the soil surface. 

Life cycle of periodical cicadas

During late May and June, the nymphs surface and climb up tree trunks, posts, and poles.  The outer shell of the nymph splits along the middle of the back, and the winged adults laboriously emerge over the course of about one hour.

Each adult may live for 5 or 6 weeks.  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.  This causes moderate twig dieback and some disfigurement (“flagging”) of forest and woodland trees, but no long-term consequences.  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 they are known for.  The males sing with a loud buzzing or drumming sound that goes on all day long.  The constant 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.  The resulting high-pitched, rapid clicks are resonated through air sacs to control sound volume and quality, and the upward angles of the wings form a megaphone-like chamber that further controls the sound.

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 the massive emergence of periodical cicadas takes patience and planning but is worth the wait.  Don’t miss this opportunity!  For a map of periodical cicada broods and a list of locations by year, see https://cicadas.uconn.edu/broods/.