Country Life: Giant cicadas will emerge after 17 years

March 23, 2004|GARY MOYERS

It sounds like the plot for a cheap horror movie.

Billions of giant insects appear out of the ground every 17 years, driving humans insane with the noise.

And their only predator is a mutated version of the common wasp, now big enough to crunch and carry one of the giant insects in its jaws.

OK, that's an exaggeration. Still, entomologists in Kentucky are predicting a large emergence this summer of a periodical cicada known as Magicicad, also called Brood X, and the Danville area could be a hot spot.

"The largest concentrations 17 years ago were in northern and southcentral Kentucky, but it looks like there will be isolated dense concentrations around Danville," said Dr. Lee Townsend, professor of entomology at the University of Kentucky. "There may be some surprises for people who live in developments that have been built near wooded areas since the last emergence."


Dr. Mike Barton, professor of biology at Centre College, remembers the Brood X emergence in 1987.

"I remember going to Cincinnati, and even driving up the interstate, you could hear them constantly," he said. "If you had a patch of them in your neighborhood, the noise was constant."

Barton said the sound made by a large group of Brood X cicadas will be noticed.

"It can be overwhelming," he said. "And it's constant. They're only out for a couple of months, but there is no doubt the noise will be heard."

The Brood X cicadas will emerge in May, Barton said, and the time above ground is brief.

"They're only going to spend a few months above ground, and the sole purpose is to mate," he said. "Some of them don't even eat while they're above ground. They die when they complete their mating task."

Townsend wrote in "Periodical Cicadas in Kentucky" that the visual impact of the emergence is striking, but the most impressive feature about the insects is the noise. He calls them the loudest insect, making a sound from specialized abdominal structures called tymbals. The noise is primarily a mating call, which is the sole reason for the cicada emergence - to mate and produce more cicadas.

Just before emergence, cicadas build a 6- to 8-inch tall mud "chimney," one sure way to predict concentrated areas of cicada population. The adults move immediately to vertical objects, according to Townsend's information, and shed their skin, leaving empty brown skins, which have split down the back.

After mating, females lay eggs. They slit the bark of trees and then insert a row of eggs into the wound, and the eggs hatch in six to eight weeks. Nymphs fall to the ground and burrow down to the root system where they stay for the next 17 years. Damage occurs as they use their piercing/sucking mouthparts to feed on sap in the roots.

Barton said the primary threat posed by cicadas is to trees and plants. The most damage is caused by adults when they carve the slits in the bark to lay their eggs. An orchard of fruit trees in an area of heavy emergence, he said, could suffer significant damage.

Methods of control for the cicada, said Townsend, include pruning smaller branches from infested trees and using certain insecticides near the root structure. He advises people who wish to control the cicada population to contact their extension agents at the first sign of emergence, or when they discover the mud chimneys.

Because the cicada emerges only once every 17 years, few predators have evolved that feed on the insect. One exception is the cicada killer wasp, a variant of the yard wasp.

"Even the cicada killer wasp doesn't make much of a dent in the cicada population because of timing and sheer numbers," said Townsend. "The wasp commonly appears in August to feed on other, more frequently-appearing types of cicadas, and that's near the end of the cycle for the periodical cicada. And, there are simply so many cicadas, the wasps are overwhelmed."

Barton said the cicada killer wasp impresses with its sheer size.

"They are big enough to kill and fly away with a cicada, so they're very large," he said. "That's a big wasp."

Fortunately, Townsend said the wasps generally stay away from humans, though they can deliver a painful sting if disturbed.

Brood X cicadas don't sting or bite, and they carry no known diseases, making them relatively harmless to humans.

But when they emerge, they do make themselves known with a symphony of astounding proportion, said Townsend.

"We will know they're here, because they will announce their arrival with great fanfare," he said. "Summer nights in Kentucky this year will have a distinctive sound signature."

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