A nervy brood of out-of-synch cicadas emerged this week across Maryland four years before their prime, serenading residents, pleasing predators and mystifying entomologists.
Sightings of the 17-year cicada species in Northern Maryland, last seen in 1987 crooning en masse from treetops and flitting across suburban landscapes, have stunned bug watchers from Bowie to Baltimore to College Park.
"They're in my yard, in my trees; they're everywhere," said Lamont Brown, who lives off Liberty Road in Baltimore County. "The birds are having a good time. The ants are having a field day. Everybody prospers."
The subterranean insects were not expected to see daylight until 2004, according to life-cycle charts. Why they chose this year to rise from the ground, fly into trees and lay eggs confounds just about everyone.
"The first thing people say is `global warming,'" said GayeWilliams, an entomologist with the Maryland Department of Agriculture. "It doesn't have anything to do with global warming. This is not the apocalypse."
Still, as she picks more than 200 cicada skins out of her trees and yard every morning and hears a thin chorus overhead, Williams is as perplexed as anyone else. From all reports, she said, the red-eyed, thumb-sized bugs appear in large numbers only in specific spots - such as Brown's yard - but in small numbers scattered throughout their breeding ground.
The mysterious short-timers belong to a particular group known as Brood 10. The name refers to one of 12 geographically distinct classes of 17-year cicadas that appear mostly in the Northeastern United States. (Cicadas are not locusts, which are a different order of bug more closely related to grasshoppers.)
Adding to the intrigue, tens of thousands of untimely Brood 10 cicadas also appeared this week in a six-county area in southwestern Ohio.
"It's really cool," said Gene Kritsky, a cicada expert at the College of Mount St. Joseph in Cincinnati. "We have six to eight thousand on campus right now. I've seen some trees with hundreds in them. Yards are inundated. I've even started hearing cicada calls."
The four-year acceleration didn't surprise Kritsky, though. Every year for a decade Kritsky has taken his students to a nearby orchard to dig up a few hundred members of the brood and monitor their growth. On these digs, he said, he discovered some time ago that a portion of the bugs had skipped the usual four-year dormancy stage and was growing at the same rate as 13-year cicadas.
Kritsky is recording samples of cicada counts from Ohio to Maryland submitted to his Web site. Other entomologists and amateurs have been feeding him information that will help document what may be an unusual evolutionary strategy.
He said only a small percentage of Brood 10 is emerging. He guesses that an overpopulation of cicadas underground may have caused a subset to relieve competition for food by coming out early.
Or it could be that the acceleration is an evolutionary strategy that will help this season's offspring form a brood that will emerge in 17 years.
Cicada expert Chris Simon, of the University of Connecticut was roaming the foothills of South Carolina and Georgia this week sampling an emergence of Brood Six cicadas when she heard of the Ohio and Maryland outbreak.
"We expected it," Simon said, speaking by cell phone in a buzzing field of cicadas. "We call it `bet-hedging.'"
By looking at maps of geo- graphic boundaries of cicada broods, she said, entomologists have noticed that major territories for 17-year cicadas often overlap. In Virginia and Southern Maryland the Brood Twos overlap with Brood Sixes from the Carolinas. They emerge at four-year intervals from each other.
Biologists believe that the occasional four-year acceleration prevents a brood from "putting all its eggs in one basket," Simon said, giving the bugs a chance to create a class.
"It's a risky strategy," she said. "But because cicadas produce so many offspring, they can afford to take the risk."