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Ancient Mystery: Synchronized Emergence of Periodical Cicadas

Posted By Prucia Buscell, Thursday, May 02, 2013

Residents of the Northeastern United States can soon expect a wildlife phenomenon not seen elsewhere in the world. Brood II Cicadas, Magicicada septendicum, the cousins of crickets and katydids and one of the longest living insects in the world, will emerge from their 17-years of living underground. Millions will fill the skies, cover trees and plants, mate, lay eggs, and then die, leaving piles of dead cicada bodies on the ground. It’s a life cycle that has intrigued scientists for centuries.

They’re harmless-they don't bite, sting or damage property-so environmentalists caution against insecticides. But they can be annoying. Males buzz to attract females, each of whom will then lay hundreds of eggs to perpetuate their kind. Listen to cicada love song here. The National Geographic reports the noise at its peak reaches 110 decibels, about as loud as a chain saw, and may repel some predatory wolves, foxes, birds and reptiles that might otherwise eat them. Cicadamania.com describes their biology and habits, and even suggests bagpipes to scare live ones away from outdoor events.

Their real protection is their numbers. Craig Gibbs, writing in the New York Times, explains there are so many of them that even voracious consumption by predators won’t make much of a dent in their population. They’ve been seen in clusters of up to 1.5 million per acre.

This spring’s Brood II cicadas are the offspring of Magicicadas last seen in 1996. (Other broods have 13 year life cycles.) The genetic mechanism that prompts them to emerge is triggered when the ground warms to a consistent 64 degrees F. They live underground from Connecticut to North Carolina, and build above ground chimneys that keep soil and water from falling into the hole as they prepare to emerge.

How and why did these creatures evolve their synchronized life cycles? Gibbs says one theory is that their cycle was a response to atmospheric cooling during the Pleistocene, to guarantee sufficient populations for successful reproduction. Some researchers think their evolutionary history may hold clues to how future climate change could impact cicadas and other insects.

Another theory is that their long life and synchronous emergence makes predators unable to anticipate their presence. Daniel Stone writes National Geographic News that the cycles of 13 and 17 years, both prime numbers in mathematics, may aid their survival. He reports on Brazilian research suggesting that a cicada with a 17 year cycle and a parasite with a two year cycle, for instance, would meet only twice in a century.

Cicadas help aerate the soil, and living or dead, they are a source of protein for large and small creatures. They were reportedly a delicacy for Iroquois and Onondaga Indians, and adventurous eaters can find recipes online for cicadas chopped and fried.

Several citizen science projects, such as the New York Public Radio RadioLab Cicada Tracker, may contribute to an understanding of these mysterious ancient creatures.

Tags:  buscell  complexity matters  nature 

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