Seventeen years ago, Brood X cicadas took their places underground, waiting to make their next noisy appearance: 2021. This summer, the cicadas are expected to move into the East Coast and Midwest of the United States.

The Brood X species are one of the seven periodical cicadas, the word used to distinguish between cicadas who have synchronized and longer life spans, such as Brood X, and cicadas with shorter and unsynchronized life spans. Once they emerge from the ground, we should expect mating songs as loud as one hundred decibels in our backyards. They can be louder than a lawnmower while they complete their month-long mating ritual.

The sounds that male cicadas produce to attract mates have been found to damage hearing. They make these sounds from their hollow abdomen; it pulls in and out of these organs, contracting 300-400 times per second.

These insects cause minimal damage to trees, and they do not devour crops like locusts. Instead, they contribute to their ecosystem by trimming weak branches, releasing nutrients back into the soil when they die, and serve as an abundant food source for birds and other animals. There is no need to be afraid of these loud creatures, they do not hurt humans. They do not bite or sting.

Even though the cicadas pose hardly any threat to humans, humans do pose a threat to them. Urban spread and over-development have destroyed cicada populations. Additionally, due to Earth’s heating climate, periodical cicadas are starting to emerge earlier by anywhere from a week to a month than they did just decades ago. Predictions were made that due to rising global temperatures, the number of years they stay underground could shorten.

Apart from climate change, there are also random cases of early sprouts. They are given the nickname of “stragglers,” and they emerge either a little early or late, up to four years in either direction.

Do these cicadas strategically plan out their appearances? An entomologist (a person who studies insects) at the American Museum of Natural History, Jessica Ware, says that she “think[s] it’s not that the cicadas know anything per se.” Instead, she believes that it is “hardwired.” Ware also shares that with the brain of an underground cicada, “[T]here’s a series of biochemical cascades, you know, hormones that rise and fall that set off a trigger. And if you have a certain hormone level and the temperature of the soil is 64 degrees, it’s go time.”

Another entomologist, John Cooley, explains how these cicadas count the seasonal vibration of fluid spreading in the roots they feed on. “They don’t keep track of time, they just count [plant] cycles,” says Cooley.

Above ground, cicadas only live for a few weeks, and Brood X will most likely be gone before Labor Day. These insects have existed for about five million years, around the time the common ancestors of humans and chimpanzees split apart from one another.

When preparing for this year’s infestation, make sure to purchase a hose to shoot the cicadas off your plants, protect inexperienced plants, and refrain from buying any new plants over the next few months, otherwise, you will have to deal with the hum of the cicadas even more.