[at-l] National Geographic News Story

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Some may find this interesting:

Braces for Bug Swarm

John Roach
for National Geographic News
March 29, 2004

Get ready, Brood X is coming. This May billions of black, shrimp-size bugs 
with transparent wings and beady red eyes will carpet trees in the U.S. from the 
eastern seaboard west through Indiana and south to Tennessee. By the end of 
June they'll be gone, not to be heard from or seen again for 17 years. "Many 
people view them with horror or as an aberration and don't appreciate that they 
are a natural part of our eastern forests," said John Cooley, a cicada expert 
at the University of Connecticut in Storrs. The bugs belong to the largest 
group, or brood, of periodical cicadas?insects that spend most of their lives as 
nymphs, burrowed underground and sucking sap from tree roots. They emerge once 
every 17 years, transform into adults, do the business of reproduction, and 
then die. 

The cacophony of their courtship ritual disturbs suburban tranquility, and 
their nests can kill young tree branches. Females make slits in the branches and 
deposit their eggs inside. The process leaves many treetops with brown, 
dangling limbs flapping in the wind. In addition to being a nuisance, the mass 
emergence aerates the soil, provides a feast to thousands of predators, prunes the 
treetops, and provides a pulse of nutrients into the environment, scientists 
say. There are at least 12 broods of 17-year cicadas plus another three broods 
that emerge every 13 years. "A brood is a class year, like the graduates of 
2004 who will be graduating this May," said Gene Kritsky, a biologist and 
cicada expert at the College of Mount St. Joseph in Cincinnati, Ohio. A brood 
emerges almost every year somewhere, sometimes overlapping with others. But none of 
the emergences matches the pure size of Brood X, which includes three cicada 
species: Magicicada septendecim, Magicicada cassini, and Magicicada 
septendecula. Keith Clay, a biologist at Indiana University in Bloomington is engaged in 
a long-term study of the Brood X cicadas. He said people's reaction to the 
17-year phenomenon runs from disgust to awe. "Some people leave town and go west 
where there are no cicadas. Other people plan camping trips timed in the 
middle of the outbreak, because they want to experience it in its full intensity," 
he said. Seventeen-Year Cycle The emergence of the cicadas marks the 
beginning of the last weeks of life for nature's longest-lived insects. Six to eight 
weeks after a female adult cicada performs her last, dying act?excavating a 
nest in a young tree branch and laying her eggs?her eggs hatch and the nymphs 
fall to the ground. The cicada nymphs keep heading down, first grubbing on grass 
roots and then tunneling about 12 inches (30 centimeters) deeper to where they 
feed on small tree roots for the next 17 years. "If you dig in the right 
place, you can find 30 to 50 nymphs in a hole about a foot square [0.1 square 
meter]," Cooley said. After the cicadas have counted 17 years?"we really don't 
know how they count the years," Kritsky said?they are ready to emerge, which 
usually happens in late spring when the soil reaches a temperature of about 64? 
Fahrenheit (18? Celsius). When twilight of their emergence day hits, the 
one-inch-long (2.5-centimeter-long) nymphs crawl out of their holes and up just about 
anything vertical?trees, barbecues, walls, tombstones. Firmly latched onto 
the surface of their choice, the nymphs begin their overnight transformation 
into adults: youthful skin breaks open, milky-white cicada emerges, wings flush 
out, and the body darkens as it outer shell hardens. This emergence also marks 
the beginning of a huge feast. "It's well known that pretty much everything 
starts chowing down on cicadas," Clay said. Dogs, cats, birds, squirrels, deer, 
raccoons, mice, ants, wasps, and, yes, humans make a meal of the insects. 
According to Kritsky, the best time to eat a cicada is just after they break open 
their youthful skin. "When you eat them when they're soft and mushy, when they 
come out of their skin, they taste like cold, canned asparagus," he said. 
Some scientists believe the mass emergence of the cicadas is part of a survival 
strategy. With so many of them, they collectively satiate their predators 
within a few days. Then the billions left uneaten are free to mate. The business of 
finding a mate and reproducing is the sole purpose of the cicadas' short 
existence above the ground. It begins with the males flying to a sunny tree and, 
with thousands of their buddies, beating out a tune on their undersides. "It's 
a high-energy activity, and they, much like a lizard basking in the sun, 
orient themselves to maximize sun exposure, which maximizes body temperature, which 
allows them to sing more vigorously and louder," Clay said. When a male 
successfully attracts the attention of a nearby female, she will flick her wings as 
he finishes his song. A courtship dance ensues, with the male continuing to 
sing up until the physical act of copulation. Shortly after mating, the male 
usually keels over and dies. The female buzzes off to excavate nests in a young 
twig for her 600 or so eggs. Once her egg supply is exhausted, the female 
dies. Six to eight weeks later, the eggs hatch and the 17-year cycle begins anew. 
Cicada Studies As this mass emergence of big black bugs strikes fear and awe 
in suburbia, the scientific community is ready to learn more about them. One of 
the scientists' big questions is what impact the bugs have on the 
environment. Indiana University's Clay will cover some trees with netting so that the 
cicadas will not be able to mate and lay their eggs and thus the nymphs will not 
be able to burrow beneath the trees and feast on their roots for 17 years. "If 
we eliminate cicadas from an area, does it have a significant effect on the 
forest, or is it a minor noise in the system?" Clay said. Within a few years, 
Clay hopes that a comparison of the health of the trees will yield an answer. 
In the years to come, College of Mount St. Joseph's Kritsky will be looking at 
why some cicadas emerge early in their cycle, as did several hundred thousand 
Cincinnati members of Brood X in 2000. The outbreak was big enough for the 
cicadas to satiate their predators, sing, mate, and lay eggs. "If [the year 2000 
Cincinnati nymphs] come out in 2017, we will have seen the evolution of a 
whole new brood," Kritsky said. "That's cool."