The Brood X cicadas have started appearing in Maryland above ground for the first time in 17 years.

The 17-year cicadas are on the move in Maryland.

Signs of the creatures have cropped up everywhere from yards to trees.

"THEY'RE HEEEERE!" the Maryland Department of Natural Resources reported Sunday, advising residents they may notice unusual sights and sounds over the next couple of months.

Since 2004, the Brood X cicadas have been burrowed underground feeding on sap from tree roots.

Brood X periodical cicadas, also known as the Great Eastern Brood, are only found in the eastern United States and emerge once every 17 years.

Their sound is one distinguishing characteristic.

"Male cicadas produce the loudest sounds in the insect world," according to the National Park Service. "Entomologists believe that the sound protects these insects by hurting predators' ears."

The emergence of the insects en masse is also believed to help protect against predators.

Billions of cicadas are expected this year, according to the Maryland Department of Agriculture.

Once soil temperatures rise above 64 degrees, the insects come out.

Residents may see exit holes that are about 0.5-inch in diameter, according to the Maryland Department of Agriculture.

Those in Silver Spring, Columbia and Cecil County reported seeing the holes in late April and early May. Read more at Patch