This May, all across the Eastern United States, a very special event will occur. Brood X periodical cicadas—a 17-year species of cicadas—will emerge. These insects have now spent 17 years underground feeding on tree roots and waiting for the soil to warm to just the right temperature. Historically, the emergence of these insects has been in decline, so this year will be an important marker to determine the health of the brood overall.
Cicadas are harmless insects and provide food for all sorts of animals, but birds in particular. Their habit of emerging in force of numbers seems to have evolved as an evolutionary survival strategy.
Brook cicadas have one of the longest insect lifespans. The 13 or 17 years life cycle of these red-eyed insects is typically marked by their emergence from the soil. The cicada nymphs will head for tree branches to molt one final time, emerging as adults. This is when they begin singing their (extremely loud) songs. The song—which sounds like a very loud buzzing or screaming sound—can be heard until the very last of the adults has died and fallen to the forest floor. These songs bring the cicadas together to breed. The cicada life cycle has three stages: egg, nymph, and adult. Once the adults have joined to breed, the female cicadas will cut holes into tree branches and lay eggs inside. The eggs will remain there for six-to-ten weeks depending on the species of cicadas. Then tiny nymphs, about the size of a grain of rice, emerge and work their way down to the ground where they burrow for the next 13 or 17 years.
Not all cicadas have such a long life cycle. 13-year cicadas and 17-year cicadas are called “periodic cicadas” or “brood cicadas” and have a long lifecycle while annual cicadas, as their name implies, only live for one year.
There are 15 different broods of cicadas, which means that nearly every year some of these cicadas will hatch out and sing their summery song. While no one knows for sure when the annual cicada emergence will happen, the American Museum of Natural History lists May 13th as a likely start date for cicada season. So keep your eyes and ears open and if we’re all lucky, we’ll have a strong cicada season this year! If you see cicadas and want to help out scientists studying them, you can report periodical cicadas using the Cicada Safari App, available on the Google Play Store or the Apple Store.