Washington - They're back.

Seventeen years after a major swarm of bug-eyed cicadas staged one of nature's weirdest - and loudest - mating rituals, their offspring are preparing to rise in Washington's suburbs and the Mid-Atlantic.

Once the ground temperature hits 64 degrees, it's on. A swarm of cicadas known as Brood II will climb from buried lairs from North Carolina to Connecticut with a very short to-do list: find a mate, make babies and die.

It will be the largest cicada population to arrive in the Washington metropolitan region since Brood X surfaced in the eastern United States in 2004. Brood X is thought by some entomologists to be the biggest of the cicada swarms that follow a 17-year life cycle.

But the coming Brood II gang, which has been underground since 1996, is no slouch.

Cicadas look like gigantic flies. They are the orange-eyed relatives of leaf-hopping insects, jumping plant lice and spittle bugs, according to the website Cicadamania. Uprisings occur every 13 years and 17 years, and cicadas that emerge the same year are called broods, which get marked by Roman numerals, like Super Bowls.

"It's an event to remember," said Missy Henriksen, spokeswoman for the National Pest Management Association.

For humans, cicada gatherings are among the most annoying things in nature. But for cicadas, they're like Carnival, college spring break and the Day of the Dead rolled into one event. Like they say in rap songs, a cicada party don't stop.

The coming frenzy of sex and death will last up to six weeks and, entomologists say, probably start around mid-May.

Males "sing," flexing drum-like organs on their bellies to attract females. A single male cicada sounds "like a child's click toy," Cicadamania says. But when hundreds of thousands of the bugs click all at once, it creates an extraordinarily loud screech that travels in waves, day and night, sounding like crickets on steroids.

Not everyone will hear it. Cicada sightings will be spotty throughout the Mid-Atlantic. In the Washington area, residents of the District of Columbia might not see or hear any, but residents in Southern Maryland and Virginia could witness more than their share, entomologists said.

"I vividly remember 17 years ago when the cicadas were everywhere and very, very noisy," said David Ledwith of Falls Church. "I would be on the telephone with someone, and they would ask what that noise was."

People remember Brood X of 2004 most because it was the most recent and because of its sheer geographic size. Weddings were disrupted, grown men beat themselves over the head when cicadas piled on, children tossed and turned in their beds from the noise.

Gaye Williams, an entomologist for the Maryland Department of Agriculture, remembered them from even farther in the past, 1987. "One woman told me her outdoor Montgomery County wedding was June 1 and asked what should she do," Williams recalled. "I said you can make it a cicada-themed wedding because that's what it's going to be."

Brood II's last outing was smaller but still made headlines. News archives from 1996 carry accounts of bug phobics running to shrinks. This year's arrival will be amplifed by updates and tweets; it's the first cicada emergence since Facebook and Twitter became popular.

Expect lots of pictures of an insect even bug lovers say is ugly. Expect tweets from restaurant patios. And expect YouTube videos of bugs making tons of noise.

"I think it is . . . important to let people know that they don't bite or sting," said Todd Michael Day, a resident of Culpeper County, Va. "And that they will invariably fly into a car window at some point. They are big, and they are ugly, but wrecking your car because one just landed on the dashboard is a bad idea."

Such birds as gulls and starlings will flock around the swarm, gulping as many cicadas as they can. "It creates a monstrous pulse of energy into the ecosystem they emerge from," said Sam Droege, a scientist at the U.S. Geological Survey Patuxent Wildlife Research Center.

"Predators can eat their fill, and there are still unbelievable numbers of cicadas that escape to mate, lay eggs and die," Droege said. "Just the dead, rotting bodies alone have a large nutrient impact on the forests and streams in an area."

Females place eggs on thin tree limbs, and six to eight weeks later, nymphs hatch and pour to the ground. They burrow their way to tree and plant roots, where they suck their juice.

There are few happy endings. The cicada nymph mortality rate is about 98 percent, according to "The Ecology, Behavior and Evolution of Periodical Cicadas," written in 1995 by biologist Kathy S. Williams and ecologist Chris Simon.

Given that millions emerge in a cycle and females lay multiple eggs, many nymphs survive. The older they get, the deeper they dig. At 17, some start bumping into each other underground.

When the ground warms, they climb, encased in a shell, which they ditch after emerging with wings. It is mathematically possible for two broods to emerge in the same year but only once every 221 years, Williams and Simon wrote.

Broods V and XXII emerged in 1897, a feat that won't happen again until 2118.

Cicadas might be harmless, said Henriksen, of the pest-control association, but wherever they show up, they will fray people's nerves.

"You remember the pervasiveness, the skins . . . left behind," she said. "They're crunchy. They land on you. People who are fearful of bugs, it will be uncomfortable for them."

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