They're Baaack

By Kristina Dell

They're not locusts (which are a type of grasshopper), but for much of the Eastern U.S. this year, they're certainly a plague. Some cicadas appear almost every year, but the Brood X periodical cicada, as scientists call this variety , is the big one: the world's largest insect swarm. For the next five weeks, sidewalks will be littered with crunchy brown shells, ant treetops will be buzzing with an ear-splitting screech.

Cicadas look scary with their vaguely devil-shaped heads, but they're really harmless, and some communities even look forward to their arrival. Cincinnati, Ohio, for example, is planning cicada festivals, parties and even meals. Gene Kritsky, a cicada expert, is testing out a new recipe this year, cicada chowder. But entomologist John Cooley, who studies cicadas at the University of Connecticut, won't touch it. "Seventeen years underground just to end up as someone's dinner?" he says. "They're too marvelous to waste."

LIFE STAGES (Duration)

1 EGG (6-10 weeks)

In her dying act, an adult female cicada creates the next generation, laying 400 to 600 eggs inside a slender tree branch by cutting small slits in it with her ovipositor, an organ that works like a saw. Six to 10 weeks later, the eggs hatch, and nymphs fall to the ground

2 NYMPH (17 years)

After hitting the ground, the nymphs munch on grass roots and then tunnel down about 12 in. (30 cm) to feed on tree sap by attaching a strawlike organ to the roots. There the wingless bugs stay--for 17 years

Finally, their biological alarm clock goes off. When that time comes, scientists think, a soil temperature of 64-oF (18-oC) signals the nymphs to tunnel back up

3 ADULT (3 weeks)

Transformed overnight into adults, the emerging cicadas start out with soft, milky white bodies. After two hours their wings unfold and dry. They suck some plant fluids and live to mate and lay eggs

Three hours after emerging, their bodies have fully darkened, and their shells begin to harden. Male cicadas head for the treetops, where the warmth of the sun improves their singing

Skin: The night the nymphs emerge, they climb the nearest vertical surface and shed their skins on everything from window screens to lawn chairs

Little drummer boys

The deafening shrill that can be heard almost a mile away is the mating cry of the male cicada. His instrument is called a tymbal, which produces a popping sound in his hollow abdomen. Males from each of the three Brook X species have their own song. One sounds like pha-roah, another makes a sizzling noise, and the last--and rarest--makes a rhythmic call that sounds like a lawn sprinkler

The good, the bad (and they're ugly)

BENEFITS Cicadas do not sting or bite, and they are not poisonous. The insects don't eat much, and healthy trees can actually benefit from the pruning that takes place when branches die from the hundreds of slits the females cut to lay eggs. On the ground, cicada exit holes aerate the soil

NUISANCES Aside from the noise and later the smell from the piles of dead insects, there is some evidence that cicada root sucking can restrict tree growth. And if you were planning to hold an outdoor wedding this month, you may want to reschedule it or move it indoors

GOOD EATIN' They're filled with protein, and people say they taste like cold asparagus. But most of Brood X will end up providing a smorgasbord for a variety of wild creatures, including songbirds, snakes and spiders. The cicada's primary defense is its vast numbers. Predators can gorge all they want, but they'll make only a dent in the cicada population

LIVE LONG AND PROSPER Although the queen termite has a longer lifespan, the 17-year cicada lives longer underground--more than 95% of its life. By comparison:

Cicada (Brood x) 17 years Queen honeybee 7 years Monarch butterfly 6 months

Source: Christine Simon and John Cooley, University of Connecticut; Gene Kritsky, College of Mount St. Joseph; Keith Clay, Indiana University; National Geographic; Cicadamania.org