Any day now, if the weather behaves, wooded areas along the Atlantic coast will be thick with red-eyed, orange-winged bugs that have not seen daylight since 1996.
The 17-year cicadas spend most of their lives underground. But every 17 years the adult insects crawl out from the soil to feed on tree sap, mate, lay eggs on pencil-thin tree branches, and then, die.
There are also species of periodical cicadas that emerge from the ground every 13 years. Both 13-year and 17-year cicadas are categorized by broods, or groups of cicadas that have the same emergence year.
Brood numbers go back to 1893 when an entomologist at the Department of Agriculture decided to label groups of cicadas that appeared every 17 years, starting with Brood I, said Gene Kritsky, a biology professor at the College of Mount St. Joseph in Cincinnati, O.H.
There are 12 different broods of the 17-year cicada and 3 different broods of the 13-year cicada. Typically, only one brood emerges in one region at one time, re-entering the world in extraordinary numbers.
Gene Kritsky/The IAS cicada websiteThis map shows the geographic distribution of Brood II, the eastern brood of periodical cicadas.This year, folks on the East Coast will see trees and shrubs blanketed by Brood II, the only group of 17-year cicadas to appear in states that run along the Atlantic from North Carolina to Connecticut.
Suburbanites can expect anywhere from a few hundred thousand to 1.5 million cicadas per acre, according to Thomas Moore, a cicada expert at the University of Michigan.
Although records show that 17-year cicadas were seen on the steps of New York City’s general post office in 1928, it’s not likely that urban folks will witness the phenomenon in full force. “It’s possible, but they are more likely to be in places that are little more rural, and sometimes in residential areas where there a lot of houses,” said Moore.
Periodical cicadas usually come out between April and June when the soil about a foot below the surface hits a magical temperature — about 64 degrees Fahrenheit. After climbing out from the dirt, the cicadas shed their skin and begin feeding on grass and shrub roots as well as trees. Almost any kind of tree will do although they seem to like cedar and white pine.
Researchers are currently developing a map to see where Brood II has emerged to date. The map below from Magicicada.org is based on 500 user-submitted reports, last updated May 7.
The cicadas not only make a visual presence. Male cicadas make a loud buzzing noise to attract females, which can cause quite a racket. Imaging more than 1 million cicadas “singing” in unison. There are three different species of 17-year cicadas within Brood II, which all make slightly different noises. Moore described one of the larger species as sounding like a mixture between a whistle and a hum. “It sounds semi-musical, but maybe a little eerie, ” he said. Kritsky said it sounded like the words “Pharaoh, Pharaoh” on repeat.
The acoustics can be deafening. Back in 2004, Kritsky found that the sounds produced by a colony of Brood X cicadas was louder than the sound of a typical jet flying into Reagan National Airport. The buzz also causes the body of the cicada to vibrate, which may surprise predators, like birds, fish, dogs, and foxes, that often gorge themselves on the unfamiliar bug, sometimes to the point of sickness.
Years ago, Moore recalls seeing a bird that was so stuffed after binging on cicadas that it could not get off the ground.
The success of reproduction is also linked to weather. Cicadas only sing when it is sunny and and they can not fly if there is frost. By the end of July or August the eggs will start hatching. The hatchlings, or nymphs, will drop to the ground. If the nymphs are not first devoured by predators like ants and mites they will safely burrow into the earth through cracks and crevices, said Moore.
The next time these young cicadas emerge from the ground they will be full-grown and ready to reproduce. In the meantime, the cicadas will spend their time eating, growing, and digging little tunnels.
A common misconception is that cicadas spend all that time underground hibernating, Gene Kritsky, a biology professor at the College of Mount St. Joseph in Cincinnati, O.H., told Business Insider. In fact, the bugs are mostly passing days, weeks, and years sucking on tree root known as xylem tissue. Xylem, which is over 90 per cent water, is a very poor source of nutrition, which may explain why the cicadas have such long life cycles, said Moore.
It’s not clear why periodical cicadas only come out every 13 or 17 years, but the nation’s cicada experts (of which there only about half a dozen according to Kritsky) suspect that the long underground life cycle protects the cicadas from predators since the hunters can’t remember that the insects are going to come out again.
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