Every 17 years, an army of giant bugs rises from the earth in the Northeast. Cicadas spend most of their lives underground, but eventually they shake off the dirt, come up for a little air and do some mating.

That is what’s happening in Ohio right now — and the bugs cover everything. During this time, 1.5 million cicadas per acre will rise from the ground like zombies. The total number will climb far into the billions.

The cicadas that currently cover parts of the Midwest and Northeast actually hatched 17 years ago. They fell into the ground and burrowed deep to spend nearly two decades in darkness. When they emerge from the ground, they are still considered nymphs until they climb onto a tree or post (or maybe the side of your house) and cling there as they shed their exoskeletons. These bugs crawl out of their own crispy skin and leave it behind, still attached to the tree.

Of course, not all cicadas get to an ideal exoskeleton-shedding location. A lot of them end up covering the ground, leaving people like this poor family in Mansfield, Ohio, with no other option than to clean up the mess.

Once the cicadas have reached adulthood they can mate and lay eggs, and a new 17-year life cycle begins.

The high-pitched humming noise you hear in the video is the mating song of the male cicada. They make this noise by vibrating rib-cage like membranes called tymbals. The cicada’s empty abdomen serves as an echo chamber that amplifies the sound — and it can get pretty loud. Cicadas have been known to produce humming as loud as 100 decibels, the equivalent of a power lawn mower or a motorcycle.