Puritan settlers in Massachusetts experienced an extraordinary sight in the mid-1600s. Millions upon millions of winged, red-eyed insects sprang from the earth. Since they didn't know any better, the immigrants compared them to Old Testament pestilential swarms and dubbed them "locusts."

Cicadas Emerge in Eastern USA
(Photo : Richard Ellis/Getty Images)
RESON, VA - MAY 16: Adult cicadas dry their wings on leaves May 16, 2004 in Reston, Virginia. After 17-years living below ground, billions of cicadas belonging to Brood X are beginning to emerge across much of the eastern United States. The cicadas shed their larval skin, spread their wings, and fly out to mate, making a tremendous noise in the process.

They were, however, mistaken. This was the first published record of periodical cicadas, which appear every 13 to 17 years in the Midwest and East Coast of the United States. This year, trillions of insects will emerge from the ground and migrate to the forest, where they will sing noisy mating songs while sipping tree sap.

National Geographic said Brood X, or the 2021 cicadas, is the largest of the 15 recognized periodical cicada broods. These inch-long insects would soon appear in vast swaths of Indiana, Ohio, Pennsylvania, Maryland, Washington, D.C., and elsewhere.

Many people on social media are terrified of the cicadas' shrill calls, as well as their disgust in general.

"If the cicadas ruin summer 2021, I [would] scream," said one Twitter user.

Although the Puritans arrived nearly 400 years ago, some Americans still confuse cicadas for locusts, an entirely different species of insect known for devouring crops.

 Jeffrey Lockwood, an entomologist and professor of natural sciences and humanities at the University of Wyoming, said there's nothing to be afraid of with cicadas, and seeing such a large swarm of insects is a special pleasure, according to

What is Brood X?

CNet said the eastern United States is home to six species of periodical cicadas and they emerge in a different year. Broods are collections of cicadas that appear in the same year.

This season, members of Brood X, or the Great Eastern Brood, one of the largest broods of 17-year cicadas, will emerge from their underground lairs to flaunt their black bodies and bright red eyes. Expect to see Magicicada septendecim, Magicicada cassini, and Magicicada septendecula, all of which are 17-year species.

ALSO READ: Brood X Cicadas Are Crawling Out of the Ground Sooner Than Expected

Why Are They Suddenly Emerging?

The insects are expected to shed their skins and emerge from the ground for a month-long mating ritual. And it's expected to be a show-stopper. As part of their mating rituals, cicadas climb trees and sing mating songs that can reach 100 decibels!

Dr Jessica Ware, an entomologist at the American Museum of Natural History, told CBS News that this would be a "pretty big event." In the coming weeks, trillions of cicadas will emerge and sing in the hopes of finding a partner in Americans' backyards, according to Ware.

Cicadas are the world's longest-living insects, spending the majority of their lives underground as "nymphs." Cicadas can live underground for up to 17 years, depending on the species, by feeding on the roots of trees.

The latest brood (Brood X) is the largest of the 12 "broods" and is turning up this year as part of their 17-year cycle.

But, according to Ware, this has little to do with time and is also determined by a variety of factors, including hormonal fluctuations accompanied by temperature changes.

Cicadas, unfortunately, do not have a long lifetime. The insects have three to four weeks to mate after emerging from underground. They are also supposed to lay their eggs during their lifetime.... before they die out.

In essence, the insects spend their formative years underground and only have three to four weeks to complete all tasks before they are eventually allowed to come to the surface.

RELATED ARTICLE: Expect Trillions of Brood X Cicada To Invade the US After Hibernation For 17 Years

Check out more news and information on Cicadas on Science Times.