You may be talking about cicadas. Do you live in the Southern part of the US? Here is part of an article from the online version of USA Today:
World's largest cicada brood begins hatching in the South
An enormous brood of cicadas that covers parts of 16 states is beginning to wake from its 13-year slumber underground.
The inch-long insects, which are sometimes mistakenly called 17-year locusts, have been reported hatching in South Carolina, Georgia, Mississippi, North Carolina and Arkansas. They will appear farther north as soil temperatures reach 64 degrees.
"There are billions of them in the trees," Greta Beekhuis says, speaking by phone from her porch in Pittsboro, N.C. The sound of the cicadas is clearly audible over the line. "When I drove from my house to the grocery store, I ran over thousands of them. They're everywhere. The air is just thick with them."
The cicadas don't bite or sting and only suck liquid from tree branches, but their sheer numbers, and the din they make when the males start singing as they search for mates, can be annoying.
Enjoy them, says Gene Kritsky, editor of the journal AmericanEntomologist. "It's like watching a nature video in your backyard."
For those who find walking through bugs to be the ultimate gross out, there's good news: The cicadas will die in a month, and the next generation won't emerge until 2024. Scientists call these cicadas the Great Southern Brood or Brood XIX. It is the world's largest "periodical" brood, one that surfaces after years.
Cicadas aren't dangerous, and are non-toxic and even edible, says Kritsky, a biology professor at the College of Mount St. Joseph in Cincinnati. "The Iroquois ate them all the time."
Even so, the bugs are annoying: They get in people's hair, their cars, their picnics and their houses.
Periodical cicadas have one of the more amazing life cycles. They exist in only one place in the world: the eastern United States. Females lay eggs in tree twigs, which hatch in six to eight weeks.
The "nymphs," as the newly hatched cicadas are called, are 1/10th of an inch long and drift down to the ground, where they quickly crawl 10 inches under the soil. They attach to tree and bush roots, sucking out nutrients as they grow.
At the end of 13 years, for 13-year varieties, or 17 years for 17-year cicadas, they come up out of the earth over the course of a few weeks, as many as a million per acre, Kritsky says. They shed their skin and turn from white to black. The males begin to sing and they mate with the females, who then lay their eggs in twigs, beginning the cycle again.
In all there are 15 broods, as the offspring groups are known: 12 of the 17-year variety and three of the 13-year kind. So most years, there is a brood hatching somewhere. Greg Hoover, an entomologist at Pennsylvania State University, says there was none in 2009 or 2010, which means the arrival of this year's Brood XIX "could kind of come as a surprise to people."