Brood II cicadas will make an appearance along the East Coast next month after a 17-year hiatus. Sun reporter Scott Dance offers up what you need to know about these mysterious insects.
BY SCOTT DANCE | THE BALTIMORE SUN
Their stubby bodies cover tree branches and clog drains, and, when there are enough of them, the creatures scream as loud as a passing freight train.
As 17-year cicadas ready to emerge from soil up and down the East Coast, most Marylanders who endured swarms of another batch of the mysterious insects in 2004 will likely have peace and quiet this time around. The brood expected to emerge from the ground next month was largely confined to Southern Maryland back in 1996.
But that doesn’t mean the winged pests won’t show up in some surprising spots. Scientists are watching for changes in the patterns of the more than half a dozen distinct cicada broods that are spread across the Mid-Atlantic. Have their territories shifted over time, for example? And have climate fluctuations thrown off their scheduled emergences?
“If they show up in Baltimore, that would be way cool,” said Michael J. Raupp, an entomology professor at the University of Maryland, College Park. “Whether there is a more current distribution [of cicada broods], nobody knows.”
With the recent spread of technology, scientists hope to develop a more detailed portrait of the members of the genus Magicicada.
When these cicadas were conceived and their parents’ footprint sketched on a map, America Online was the primary consumer gateway to the Internet and only had about 5 million users. The U.S. government, meanwhile, was just two years into deployment of the Global Positioning System.
This time around, entomologists hope broader public observation shared via the Internet and GPS technology will help address questions about how the broods broke off onto different cycles, whether their footprints overlap and what influences helped determine those quirks of nature. The scientists suspect that older observations — and maps that show brood territories aligning like puzzle pieces — lack nuances such as interlocking or shifting boundaries.
Cicadas are not likely to swarm over trees in Baltimore and other parts of Central Maryland yards as they did in 2004. But some will hatch in smaller numbers, as they do in any typical year, following a two- or three-year life cycle.
Half a dozen species of cicadas emerge only once every 13 or 17 years. They spend about a month above ground, with the males broadcasting their shrill mating calls until eggs are laid inside cuts in the tips of tree branches. The adults die.
About two months later, the eggs hatch and nymph cicadas drop to the ground, burrowing beneath tree roots that they feed on until the next cycle begins. After somehow counting the requisite number of seasons in between, the nymphs dig their way back up once the soil temperature reaches about 64 degrees, usually around mid-May. They shed their dried skins and fly about as adults, starting the whole process again.
But what governs that process is a mystery to scientists. While the cycle of life and death is the same for all, as many as seven broods of cicadas have been observed over the past century in the Mid-Atlantic. A cohort of the insects known as Brood X inundated an area that included the District of Columbia, Baltimore and Philadelphia in 2004.
Brood XIX cicadas, a 13-year variety, were the last recorded in Maryland, observed in 2011 on the southern tip of St. Mary’s County and in Tidewater Virginia. Brood V reached parts of Garrett County last in 1999.
The batch expected next month is dubbed Brood II and reaches from the Northern Virginia suburbs through central Virginia and over the North Carolina border, as well as parts of southeastern Pennsylvania into New Jersey. In Maryland, sightings in 1996 were confined to an area surrounding the Patuxent River in parts of Calvert and St. Mary’s counties.
John Zyla, a government contractor with a strong side interest in cicadas, was there to track the brood that year, and he will do so again soon. The last time, the St. Mary’s County resident drove across Southern Maryland, crudely marking X’s on a map when he passed outside the cicadas’ territory, where the chorus of mating calls turned to a “deafening” silence, he said. He has done the same with broods across Maryland and Virginia in other years.
Next month, though, Zyla plans to hit the road in his Chrysler Town & Country minivan with some fancier technology: a laptop mounted on his dashboard. It’s connected to a GPS antenna that lets him precisely mark the cicadas’ territory with the tap of a button.
“With so many people having access to the Internet now, we can get a lot more information a lot quicker,” Zyla said. If the coming brood had reached farther north into Anne Arundel County or beyond in 1996, “someone would have noticed,” he said. Still, he said, he’s open to being surprised.
So is University of Connecticut research scientist John Cooley, with whom Zyla plans to share his observations. Cooley is looking to draw on contributions from enthusiasts like Zyla, as well as more casual observers, to get more detailed data on the cicadas.
“We want to get nice geo-referenced maps, so we can say, ‘Cicadas were here in these densities,’ and then come back and see if they changed,” Cooley said. That has been impossible in the past. “Maps we have do not really let us come close to answering that question.”
The theory is that some broad climate fluctuations have caused cicadas in certain areas to adopt alternate cycle schedules, he said. For example, an early freeze one spring that killed off blooms that later grew back could trick the cicadas into miscounting seasons. Experiments have found that some sort of tally of seasonal cycles, rather than a measurement of time elapsed, is what brings the creatures out from underground, Cooley said.
One thing researchers want to know: In how fine a scale do those diversions occur? It’s possible that there are nooks and crannies along the border between broods’ territories, but scientists don’t expect to find nymphs from separate broods emerging from beneath the same trees.
Other theories hold that underground crowding can shorten the 17-year cycle to 13 years, or that the cycles are prime-numbered as an evolutionary development to prevent overcompetition. Prime-numbered cycles are less likely to overlap with each other. Better understanding how broods interact, compare and contrast could help provide evidence for or against the theories, scientists said.
Still, for some, the cicadas are little more than a nuisance. They pose no dangers, though they can sometimes damage orchards.
Zyla had his infant daughter in tow the last time the cicadas swarmed Southern Maryland, but he doesn’t expect the now 17-year-old to be as willing. His youngest son, age 9, might, though.
“They get tired of listening to me talk about cicadas,” Zyla said.
(Tim Swift contributed to this report on The Darkroom.)