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Paper: Washington Post Title: No Cicadas on Ice Biologists Theorize That 13- and 17-Year Broods Evolved to Survive Climatic Changes Date: May 3, 2004 Evolution has shown living things a thousand ways to save themselves. The leopard gecko's tail pulls off, leaving the cat clutching nature's version of the tear-away jersey. The female pea crab Pinnotheres, unsatisfied with her own shell, spends its life inside an oyster. The bacterium Thermotoga maritima grows in water just below boiling temperature, an environmental niche into which most organisms won't dip a toe. Few strategies, however, are as strange and unlikely as the one periodical cicadas found. These large, ungainly insects in the genus Magicicada spend either 13 or 17 years underground, then emerge nearly simultaneously in densities that can exceed 1 million per acre. Their few weeks of life in the open air are spent molting, calling for a mate (in the case of the buzzing males), copulating and depositing eggs in nests made in gashed twigs (in the case of the diligent females). They do little to defend themselves. They fly poorly, don't fight and taste great. In the parlance of animal behavior, cicadas are "predator foolhardy" -- they are always available for lunch. Birds consume them in the greatest numbers, but many other animals get in on the act. Squirrels, dogs, cats, turtles, fish and spiders all eat cicadas , which for a few weeks are the protein equivalent of manna from heaven. Eventually, though, everyone gets full -- and there are still billions of cicadas alive. This is the survival strategy known as "predator satiation." It is a passive strategy that depends almost entirely on timing. If too few cicadas emerge, or if they come out over an extended period of time, they are likely to be wiped out by predators. If this occurs before they find a mate and create a new generation to carry their genes forward, they will eventually disappear completely. Most species of cicada have life cycles between two and eight years, with a fair amount of variability. If five years is the dominant length, for example, many members of a population may come out in four years -- or not until the sixth. Of course, this isn't apparent to the casual observer. That's because in most places a person hears cicadas -- often more than one species -- every summer. A fraction of the population reaches maturity and emerges every year, making the insects annual, not periodical.
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This note was uploaded on 10/21/2009 for the course HONORS 250 taught by Professor Staff during the Spring '08 term at University of Michigan.

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Cicadas%20on%20Ice - Access World News Page 1 of 3 Paper:...

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