Still, Engel recalled her own encounter with Brood X in 1970, after a high school softball game, when the girls returned to a bus that was parked under some shade trees - with the windows open. "By the time we got back in the bus, it was full of them," she said. "For a bunch of teen-age girls, it wasn't a pleasant experience."

The ick factor again.

Cicadas don't bother house pets - quite the opposite. Cats and dogs often find the surfeit of clumsy, crunchy insects the irresistible equivalent of an all-you-can-eat buffet. They just don't know when to stop eating.

Dr. Kim Hammond, a veterinarian at the Falls Road Animal Hospital, remembers the 1987 invasion. "The dogs got into huge piles of them, got sick and threw up," he said. "They don't even chew - they inhale."

Cicadas are safe for human consumption, in moderation - provided they haven't been exposed to insecticide (which is not recommended). Kritsky, who has eaten cicada nymphs "Cajun-style, stir-fried and raw in salads," likens the taste to "cold canned asparagus." Low in carbs, the nymphs are Atkins-diet friendly, he says.

Ick factor aside, many will find the spectacle fascinating. "This is gonna be active, raw nature," Raupp said. "They're gonna be mating, flying, crashing into buildings, running away from birds. They're gonna be eaten, having sex, laying eggs, falling out of treetops. And people will have the opportunity to witness everything that happens in biology."

The Brood X invasion is the largest insect emergence in the world. Although its precise boundaries are fuzzy, the heaviest populations are in Indiana, extending into southern Michigan and western Ohio.

Most of Maryland lies in a second zone that extends from northern New Jersey, across the southeastern half of Pennsylvania, into Delaware, Northern Virginia and eastern West Virginia. A third segment extends from northern Georgia to eastern Tennessee and western North Carolina.

Maryland is host for other broods too. The largest is Brood II, which appeared in 1996, in Calvert and St. Mary's counties.

Periodical cicadas in North America have been in retreat for centuries as agriculture and development have destroyed their wooded rural habitat.

But the future might not be entirely bleak. In fact, Clay said, "a central theme of our research is that humans have modified the landscape in a way that may make it more conducive to higher populations of cicadas and bigger outbreaks."

Suburban developers are converting farmland to parklike suburbs with grass and scattered trees, "which is really excellent habitat for cicadas," Clay said. Ditto for golf courses.

Meanwhile, in undeveloped rural areas, small farms are being abandoned, so forests are returning. The cicadas will likely follow, although "it would be a slow encroachment," Clay said.

Not everyone will welcome them. Dr. John R. Lion, a Baltimore psychiatrist, noted in 1987 that the cicadas' appearance, brief frenzy and death provoked anxiety, revulsion and even suicidal thoughts in some patients.

In a column for The Sun, he concluded that "these weird little bug-eyed bugs ... actually stirred up some buried panic about mortality, and they pushed buttons within us that made us flee in horror, or stare in wonder, or duck and hide. Was our existence to be equally brief and puny?"