As many as 40,000 periodical cicadas may cling to a single tree, creating a noise level that may exceed jets flying overhead and nearby interstate traffic. Furthermore, periodical cicadas are much more damaging to trees - due partly to their sheer numbers and method of egg laying. The female cuts a slit in the tips of branches to lay her eggs,'' Crutchfield says. She may cut four to 20 slits in a single branch. It causes the tips to die.'' Because annual cicada numbers are so evenly distributed each year, they cause minimal damage to trees.
Annual cicadas are larger than periodical cicadas, averaging about two inches in length.
They tend to have mottled dark-green bodies, green eyes and green legs. Periodical cicadas are smaller, averaging about an inch and a half in length. They have black bodies, red eyes and orange legs. The adult of both types of cicadas lives only a few weeks. People have little to fear from cicadas despite their menacing appearance.