Spring has sprung, and it carries different meanings for everyone. For baseball fans, it means regular trips to the stadium replete with hot dogs and Cracker Jack. For students and teachers, it means being that much closer to summer.

And for those who live in the Northeast, spring means the emergence of periodic cicadas for the first time in 17 years, an event affectionately dubbed Cicadapocalypse. Soon, parts of Ohio, New York, Pennsylvania, Maryland, Virginia and West Virginia will see hordes of these insects rise up from the ground, blanket the skies and descend upon the earth, issuing their loud, shrill mating calls all the while. As billions of cicadas emerge, they can reach an overwhelming density of 1.5 million insects an acre in places, reports the Washington Post.

If this sounds doomsday-esque, don't be alarmed — despite their ominous appearance, cicadas are harmless. These herbivores are concentrated solely on finding mates and laying eggs. They carry no diseases, and they neither bite nor sting. And contrary to popular belief, they are not locusts (or even closely related to them).

Cicadas are large insects of the family Cicadidae. The ones that will emerge this spring are of the genus Magicicada, which are limited to eastern North America. These cicadas are known as the periodical cicadas or the 17-year cicadas due to their abnormally long life cycles and the length of time in between appearances. The reason for their impeccably-timed life cycles is still not completely understood by scientists.

Periodic cicadas emerge to mate, lay eggs in tree twigs and beget the next generation. Cicadas spend the first 12 or 16 years of their lives (depending on the species) underground, sucking out nutrients from tree roots for survival and molting several times. Upon their final molt, they tunnel out into the world and males begin to attract females to mate. They do this by congregating and producing songs through membranes on their bodies. These songs — which are more akin to loud, whirring buzzes — can be as loud as 100 decibels and arouse female cicadas. The matured cicadas then mate, the females lay eggs, and the process begins anew.

Cicada waves are known as broods, and each brood covers a different swath of the country. This year, the Brood V cicadas will surface; next year, Brood VI will emerge in Georgia, North Carolina and South Carolina, according to Cicada Mania. Cicadas emerge generally when the soil where they lay dormant reaches 64 degrees Fahrenheit. You can track the date that the insects will emerge in your area on Cicada Mania or ask longtime residents who no doubt remember the last time the swarms rose up. The season of the cicadas usually starts between April and June and should end by late July.

At their worst, periodic cicadas are irritating. Their mating calls are ear-splitting, and they can overwhelm outdoor areas — so it might not be the best idea to get married outdoors in the Northeast this summer. If you run a garden, nursery or orchard, be sure to protect your plants by bringing them indoors or covering them with screening material.

With such short life spans, the cicadas are usually all dead and grounded by late July, if not earlier. So as you're walking in Brood V-affected states, that might explain the crunchy sound you hear.

Editor's note: This file was originally published in April 2013, but has been updated with new information.