Attack of the Teenagers! Cicada Edition
Noisy, hungry and constantly surrounded by their friends--in some ways, periodical cicadas are typical teenagers. These chirping, black, inch-long, red-eyed, winged insects pull off one of the neatest tricks in nature! While a few cicadas pop up on the East Coast every summer, periodical cicadas only appear once every 17 years. (And some periodicals appear once every 13 years, but that's a different story.)
These cicadas come from eggs planted long ago in tree branches. Tiny, six-legged nymphs hatch out of them, fall to the ground, and scurry down into the soil. Once underground, they settle down on the tree roots and begin to feed. Then they stay down there, nice and snug, sucking sap for 17 years. That's right, 17 years! Periodical cicadas are North America's longest-lived insects.
Now it's time for the cicadas to become adults, mate and lay new eggs. They start burrowing back up to the surface through dime-sized tunnels. There are a few different groups (or "broods") of 17-year cicadas in the United States, but the largest of these is Brood X. These cicadas long ago circled 2004 on their calendars as the year to party. Okay, they don't really have calendars or pens, and they don't exactly party. But they do know--scientists are not sure how--exactly when to buzz off in search of mates.
Michael Schauff is the associate director of ARS' Plant Sciences Institute in Beltsville, Maryland, and in 2004 he was leading research at the Institute's Systematic Entomology Laboratory. He says the cicadas are basically harmless, but they get all over everything. If you were around in 2004, you probably remember.
They overwhelm yards, bump into windows, fly into people's faces, and--when they finally die off, about four weeks after showing up--their bodies clutter the sidewalks and clog rain gutters and downspouts.
Where Are They?
These periodical cicadas don't show up everywhere, but do cover large areas, mostly in the eastern United States.
"People start seeing them in early-to-mid May in parts of Virginia, West Virginia, Maryland, Pennsylvania, Delaware, New Jersey, western North Carolina, Kentucky, Georgia, Tennessee, Ohio, Indiana, and southern Michigan," says Schauff. "Other states may see them as well."
The more big, old trees there in an area, the more cicadas there generally are. During their soil stage, the cicadas settle themselves anywhere from 2 inches to 2 feet below the surface. Seventeen years later, when the bell inside their tiny insect brains goes off, telling them it is time to reproduce, they move up to just about an inch below ground. Then they wait. During this time, their bodies begin to change, so they'll be ready for life in the above-ground world.
The first signs of them that most people see are muddy little mounds resembling tiny volcanoes, or chimneys. They make these as they climb out of the ground. After dark, the cicadas emerge in a rush, as if responding to some secret signal. They crawl a foot or more up tree trunks and weeds. There, they hold tight and shed their underground skins, much as snakes slither out of theirs. They wait a day or two for their soft, white skin to harden and their wings to dry. Then they fly off.
Doing What Comes Naturally
About 5 days after flying up into the trees, the males "sing" to attract females. This song is actually a shrill sound they make by using body parts called "timbals," located near their stomachs. When thousands and thousands of cicadas do this at the same time, it makes quite a racket!
About 10 days after they fly into the trees, the cicadas mate. Afterwards, the females use a saw-like device at the end of their abdomens to puncture the bark of a twig and make tiny pockets in the young wood. Then they deposit 10 to 20 eggs in each pocket. One female can lay 400 to 600 eggs.
The cicadas stick around for about four weeks, generally from mid-May to mid-June. They can be a bit of a nuisance, but do they cause any real damage? If there is any harm, it is to small or newly planted hardwood or fruit trees and grapevines. That's because cicadas make small incisions near the tips of tree branches in which to lay their eggs. The branch beyond the incisions often dies. So, although big trees won't be hurt by this, little ones may suffer.
It takes about six to 10 weeks for new nymphs to hatch from the eggs. Then the whole 17-year-long cycle starts anew.
-- By Luis Pons, formerly Agricultural Research Service Information Staff
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