Curious Nature: The cicadas’ summer songs
Vail, CO Colorado
Did you hear the nighttime summer orchestra this year? In July and August, 26 different species of cicadas emerge here in Colorado to molt their young skin, becoming full adults, ready to mate. The males attract the females with their buzzing song, which is emitted from tymbals, or domed, drum-like organs on the sides of their abdomens. Like opera singers, the males contract and release their stomach muscles, making the tymbals resonate. A large air sac in the abdomen greatly amplifies this sound, as you have surely heard. One group of Colorado cicadas lacks these tymbals and “sings” by clicking together their wings. Imagine if your stomach growled as loud as the cicada’s song!
Males will sing for four to six weeks, until successfully attracting a female and mating, at which point the female begins to lay eggs in slits that are carved out in the trunks and branches of trees. After mating, the adults die, returning nutrients to the soil and plants that they spent the past two to six years taking from. The eggs hatch after six or seven weeks, at which point the small young, called nymphs, drop to the ground and burrow beneath the soil surface, as deep as 10 feet. There, they spend the next two to seven years sucking sap from tree roots, until they emerge to break out of their nymph shells (which are what you find left behind on trees) as grown adults, and the cycle continues. It takes only one day for the nymphs to break out of their shells, the wings to expand and the new adult shells to harden.
With life cycles of two to seven years, cicadas are some of the longest-living insects (most live less than one year, some only for a week). Periodical cicadas, which are found east of the Mississippi River, have life cycles of 13 or 17 years and are the longest-living cicadas. These ones emerge in masses, feeding all inhabitants of the forest who take advantage of the largest feast they’ll see in a lifetime. Once the birds, turtles and skunks are stuffed, the remaining cicadas mate and then die and fall to the forest floor, resulting in a marked growth in forest life. Although they remain underground during their lifecycle, different broods are on different schedules, which is why you’ll see, or at least hear, cicadas each summer.
One misconception about the cicada is that it is the same as a locust, which describes certain migratory grasshoppers. This error came about when early European settlers first experienced the mass emersion of periodical cicadas. Because they were unfamiliar with these North American cicadas, they mistakenly identified them as locusts, which had been described in the Bible. Linked to that misunderstanding is the idea that cicadas damage plants and crops. While locusts feed on crops, cicadas do not. The nymphs that spend the majority of the lifecycle feeding on sap from roots cause no detectable harm to the plants, as they mature slowly. The only potential harm that may be caused is when large numbers of cicadas insert eggs into the stems of trees and shrubs, potentially, but not necessarily, causing some twig dieback. Generally speaking, however, these curious creatures feed the forest rather than harm it and cause nothing but wonder in our natural world!
Kate Iberg is a naturalist at Walking Mountains Science Center. During her free time, she can be found on hiking trails, rafts, a bike or her snowboard.