Periodic cicadas, with life cycles of 13 or 17 years, are endemic to eastern North America. In the coming weeks, a brood of 17-year cicadas will emerge across the upper Midwest, from Iowa to Michigan. Their emergence is triggered by soil temperature, which must remain at or above 64 degrees for a week or more; depending on latitude, this generally occurs from mid May to early June.
After emerging from the soil, cicada nymphs climb onto trees, shrubs and other vertical structures and rapidly molt to the adult form, leaving dried skins behind. These adults will live for 3-4 weeks, driving humans crazy with their overwhelming numbers and piercing buzz; the latter is delivered by the male cicada in a fenzied effort to attract a mate. During their brief life span, adult cidadas do not eat and cause no direct injury to foliage; however, the females lay their eggs in the tender parts of trees and shrubs and this can lead to widespread damage to vegetation. Once the eggs hatch, the nymphs drop to the ground and burrow into the soil; there they attach to a root and patiently nourish themselves for the next 17 years.
While making life miserable for suburbanites, adult cicadas provide a wealth of nourishment for birds, raccoons, opossums and squirrels; they are also consumed by cats, dogs and some adventurous humans.
