From ODNR: Based on the year of adult emergence, cicadas are grouped into broods with each appearing during a different year. Due to staggered development, adults appear somewhere almost every year and since some brood territories overlap, a few areas may experience more than one emergence during a 17 year period. Adult periodical cicadas have red eyes and dark bodies and measure slightly over 1 1/2 inches long. They do not bite or sting. Adults live about four to six weeks during which their sole purpose is to mate and lay eggs. Cicada “songs” will be heard from early morning to late evening as long as adults are present. Males are responsible for the droning noise as they call for mates. Periodical cicadas should not be confused with dog day cicadas which are larger in size, mostly green with black eyes, and appear each August in small numbers.“Flagging” or breakage from slits Adult cicadas do not feed. Damage to deciduous trees (especially oak, apple, dogwood, and hickory) occurs when the female cicada cuts two parallel slits in small (pencil-sized) twigs where she lays 24 - 48 eggs. Sometimes a continuous slit 2 - 3 inches long is formed as she moves up a twig, repeating this process. The slits cause browning, breakage, and scarring on affected branches. The eggs hatch in six weeks and young cicadas, or nymphs, fall to the ground where they burrow into the soil and spend the next 17 years feeding on small roots. At the end of this time, usually in May and early June, nymphs crawl out of the soil and climb up tree trunks or other vertical objects where they shed their nymphal skin and emerge as adults.