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The Periodical Cicada’s Timing

CICADAS, insects resembling locusts, live on all continents except Antarctica. Unique to the northeast of America, however, are the periodical cicadas, which have long fascinated biologists.

A cicada
Consider: Millions of periodical cicadas appear suddenly in the spring for just a few weeks. During their short time in the sun, they shed their juvenile skin, sing deafeningly, fly, reproduce, and then die. Strangely, the next generation appears either 13 or 17 years later, depending on the species. What happens to these insects in the meantime?

To answer, we need to understand the periodical cicada’s unique life cycle. About a week after appearing, adult insects mate and the females lay from 400 to 600 eggs inside tree twigs. Soon thereafter, the adults die. Within the next few weeks, the eggs hatch and the young nymphs drop to the earth, burrow into the soil, and begin a life underground, where they suck fluids from the roots of shrubs or trees for several years. Either 13 or 17 years later, the new adult generation emerges to repeat the cycle.
According to an article in Nature magazine, the complex life cycle of these cicadas “has confounded scientists for centuries. . . . Even now, entomologists are trying to understand how the insects’ peculiar life cycles evolved.” It is an unprecedented mystery in the animal kingdom.

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