Magicicada Brood II is set to complete a 17-year cycle and fly at some point in April or May, flooding the sky with cicadas all over the Northeast. Following several years in the ground sucking sap from tree roots, they will emerge in their “nymph” state from underground locations in Maryland, Connecticut, North Carolina, New Jersey, New York, Pennsylvania, and Virginia. Once they emerge they will scale and latch onto the trees and molt into their adult forms.
Though the swarms may be loud during the day and very dense in some areas, cicadas are totally harmless. Areas with deciduous trees are expected to see the largest numbers, attracting feeding adults. Large enough swarms might interfere with outdoor activities.
Cicadas reproductive cycle leads them to emerge from underground once every 13 or 17 years. The last time a brood of cicadas emerged in our area was 2004.
They are often confused with locusts, but are not related. At insects.about.com the schedule of various cicada broods is detailed.
(bottom photo from National Geographic)