In light of an exceptionally large brood in 1998, this spring's emergence of 13-year periodical cicadas in central Missouri was forecast to be overwhelming. However, it appears that the excessive rain and cool temperatures have, at the very least, delayed the spectacle.
Unlike the annual dog-day cicadas, periodical cicadas emerge in massive numbers every 13 or 17 years. Following a prolonged stage as nymphs beneath the soil, they climb onto a tree or other structure and molt to the adult phase, which lasts only a month or so. As adults, these cicadas are focused purely on producing the next generation; the scratchy calls of the males create a deafening chorus from dawn to dusk which increases in concert with the daily temperature. Once mating has occurred, the female lays her eggs in furrows along the tender stems of shrubs and trees, causing significant damage when the cicada broods are massive. If not eaten by birds, the eggs hatch and the nymphs drop to the ground where they burrow beneath the soil and attach themselves to a root for the next 13 or 17 years.
In the Midwest, periodical cicadas generally emerge by mid May and their noisy, adult population peaks by the end of the month before fading away in June. From an evolutionary point of view, it appears that these mass breeding cycles serve to overwhelm predators (crows, jays, raccoons, opossums, house cats etc.), thereby ensuring that their next generation is safely emplaced. As we move into a hot, dry spell next week, we'll likely experience the full impact of the cicada invasion.
