It will soon get very noisy out in the Western Pennsylvania woods, and that's not even taking into account the ATVs revving through the forests.
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John Rawlins, associate curator of invertebrate zoology, examines Nagicicada cassinii at the Carnegie Museum of Natural History. (Martha Rial, Post-Gazette) |
This month and next those motorized drones will be all but drowned out by the high-pitched mating buzz of tens of millions of 17-year cicadas -- big, black-and-orange-bodied bugs with menacing red eyes that have just started to invade the region's wooded areas.
"This is the big one," said John Rawlins, associate curator of invertebrate zoology at the Carnegie Museum of Natural History. "We get some annual cicadas every single year, but this year we get the 17-year cicadas and, if they show up as they have in the past, there will be thousands per acre. You'll know it when they're out."
Most of the noise from what Rawlins calls the "Pittsburgh Brood," but what is officially known as Brood VIII, will be heard in Allegheny, Armstrong, Beaver, Indiana, Lawrence, Somerset and parts of Washington counties.
This brood last emerged in 1985 and won't be back again until 2019.
Brood V appeared south of Pittsburgh in Greene, Fayette and parts of Westmoreland counties in 1999.
Often mistakenly referred to as "17-year locusts," the 1 1/2-inch-long cicadas are not related to the large, migratory grasshoppers that famously plagued the Egyptians of the Old Testament. They are, rather, the giant kin of leafhoppers, psylids and aphids.
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One male (top) and two female specimens of the Nagicicada cassinii from the collection at the Carnegie Museum of Natural History. (Martha Rial, Post-Gazette) | |
Over the next six to eight weeks, they will crawl out of two-foot-deep holes in the ground where they have spent the last 17 years sucking sap from tree roots and going through a succession of nymphal stages. They will climb up whatever is handy -- trees, houses, telephone poles. There they will grab hold and pop out of their last nymphal skins to emerge as adults.
The newly hatched adults are soft and white but harden and darken in a short time, then take wing. They leave behind hollow, honey-colored exoskeletons that also quickly harden and are often found and collected or crunched underfoot by inquisitive children.
The adult cicadas live for just a few weeks, during which their primary purpose is to mate, starting about 10 days after they emerge out of the ground.
"Females have to wait for the males to call," Rawlins said. "When the male screams, the female comes and they engage in prolonged mating over several hours.
"The males make the noise, but the females have to agree. It's her choice."
Rawlins said the shrill mating call of the cicada -- he alternately refers to it as a "scream" or a "roar" -- is produced by a drum-like part of their abdomens known as tymbals, located just behind their wings.
The bugs use their muscles to vibrate the ribbed membranes which tick-tick-tick-tick rapidly, like the party clickers used on New Year's Eve. The males have a hollow, rounded abdomen which acts as an echo chamber.
"The entire tymbal tick-ticks at 20 to 40 cycles per second and each tymbal has multiple ridges so the individual clicks occur so quickly they aren't discernible to the human ear," Rawlins said. "But they are modulated in a different way by each species. All three of the cicada species in this brood have different calls."
The high-pitched noise can be heard for up to a quarter mile away and is amplified when males band together by the hundreds or thousands.
After mating the females insert their eggs into the twigs of common forest trees using saw-like appendages called ovipositors. This egg laying can damage young trees and heavy infestations can cause "cicada tips," a condition that shows up as drooping leaves and twigs.
"Trees may lose some branches," Rawlins said. "Trees that are younger than four years are more susceptible to damage and owners may want to protect them by covering outer branches with cheese cloth or fine netting until adult cicadas are gone."
The adult cicadas live for three or four weeks and all die off by the end of June. The eggs hatch in six-and-a-half weeks. The ant-sized, white nymphs fall to the ground and burrow deep into the soil where they will spend the next 17 years.
It is this 17-year subterranean sojourn -- and the similar 13-year life cycle of four species of cicadas all living in more southern climes -- that sets the periodic cicadas apart from most bugs and more importantly its predators.
"It's a remarkable evolutionary story that they have experienced a modification of a control mechanism to allow them to emerge periodically," Rawlins said.
"The 17-year cicadas just dump a big load so the sheer numbers overwhelm any predators, and they don't specialize in getting away or even being distasteful," said Rawlins, who on occasion has been known to pop one in his mouth and chew it up. He said they taste like "chalky sawdust, a little oily."
A restaurateur in New Zealand recently did Rawlins one better, serving sun-dried, protein-rich cicada in beetroot and red currant relish with smoked abalone terrine, sourdough bread and, according to an enthusiastic review, "an amusing Pion Gris wine."
Neither the nymphs nor the adults bite back. Nor will they sting or harm people or animals in any way. In fact, they are easy to catch and have few if any defense mechanisms.
