Annual cicadas are Hemipterans, or true bugs. They exist in a larval state for most of their life cycle, and the nymphs reside underground where they tap into tree roots and extract fluid. The adults emerge in mid-summer, and their incredibly loud pulsating buzzes become a staple audio feature of the dog days.
There are ten species of annual cicadas in Ohio, and all can more or less be readily distinguished by the sounds that they make. Cicadas don't use a file and scraper system to make their songs, as do the Orthopterans (katydids, crickets and the like). Instead, they have a specialized organ known as a tymbal, and the insect uses powerful muscles to rapidly contract and release the tymbal, creating a "song" that can allegedly hit 120 decibels in some species!
The annual cicadas are not to be confused with the 17-year periodic cicadas that emerge in mass and cause such a ruckus.
This Swamp Cicada was good enough to "sing" right under my nose, and I took the opportunity to make this short video. I'm sure you'll recognize the sound!