May 15, 2011

13-Year Cicadas Again Buzzing The South

Throughout the southern United States and as far north as Illinois and Indiana, the noisy sounds of billions of red-eyed cicadas are ringing out for the first time since 1998.

After living quietly underground for the past 13 years, the insects -- dubbed the "Great Southern Brood" by scientists -- are emerging to mate and quickly die off.

One traveler through the area said he heard a high-pitched whirring so loud he thought the engine of his truck was overheating. "I was getting ready to raise my hood when I realized that I was hearing the 13-year cicadas," Charles Seabrook, a Georgia writer and naturalist, told Reuters.

"The most common description I've heard is that it's an alien invasion," said Nancy Hinkle, a University of Georgia professor of entomology. "It sounds like the mother ship is hovering down in the woods."

The cicadas are called "periodical" cicadas because they remain underground for years before surfacing to mate and die, unlike annual cicadas that surface each summer. There are also 17-year cicadas found throughout the Northeast and Midwest, said Hinkle.

"The periodical cicadas are about 30 percent smaller than the annual cicadas," Hinkle told Reuters. "And periodical cicadas have bright red eyes."

Cicadas are commonly mistaken for locusts. But unlike locusts, cicadas don't bite and they are not harmful to humans or crops.

And while they remain underground for years at a time, they are not dormant that entire time. "They are actively growing," said Hinkle. "The little nymphs are down in the ground, they've got their mouth parts attached to tree roots and they're sucking the juice out of tree roots."

With little clarity as to why they surface every 13 years, they do so in mass numbers like clockwork. They shed a layer of skin, leaving behind a shell, and inflate and dry their wings, allowing them to fly.

The loud whirring repetitive sounds occur as males attract females by furiously vibrating membranes in their abdomens, which produces the loud drone. "It is one of nature's great oddities," said Seabrook.

The insects' lengthy life cycles are abound by many theories. One is that they reproduce in such numbers all at once to ensure their existence, effectively keeping predators from being able to eat all of them.

Cicadas are a tasty snack for many animals, including turkeys, raccoons, skunks and coyotes. "They make tremendous dog toys," Hinkle noted, adding that "dogs love to play with cicadas because they buzz. People let their dogs play with them just for the entertainment value."

The show will soon be over, however. After mating, females lay eggs on tree branches and, within a week or so, most of the adults die or get eaten. The little cicadas hatch, fall to the ground, and then burrow into the soil, not returning for another 13 years -- in 2024.


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