What’s the Ruckus: Summer of the Cicadas
by Greg Podniesinski
That may be what many people are wondering about a month from now when Brood X (also known as the Great Eastern Brood) of periodical cicadas begins to emerge from the soil. Having spent the past 17 years quietly feeding on sap from tree roots, periodical cicada nymphs will migrate to the soil surface and emerge. The emerging nymphs quickly climb up any object and complete their metamorphosis into adults. Shortly after that, our forests, parks, and towns will be whirring with the din of calling males (the females don’t sing). For those who don’t recall the sounds from the last Brood X eruption (back in 2004), at peak, the collective volume of singing males can exceed 100 decibels (similar to standing near an active airport runway or front row at a rock concert).
Looking like aliens with their red eyes and stout, 1.5-inch black bodies, Brood X periodical cicadas will emerge over one to several days, nearly in unison, when soil temperatures reach about 64 F°, in numbers estimated in the billions. They are nearly defenseless and poor flyers (they may fly directly into objects), so they fall prey to nearly every predator, including fish, birds, amphibians, reptiles, and mammals. Although easy prey, their strategy of emerging simultaneously overwhelms their predators. There are simply too many adult cicadas for predators to put a dent in their numbers.
Periodical cicadas are only found in eastern North America, occurring in about 30 populations or “Broods”, each restricted to certain regions. Broods I – XVII are 17-year broods and occur in northern areas, while Broods XVIII-XXX are 13-year broods and are found in the southern US (the shorter life cycle is likely due to the warmer climate). In Pennsylvania, Brood X cicadas occur in a swath from about Franklin to Lancaster Counties and north to about Lackawanna and Monroe Counties. Note that these are different from the annual cicadas, which appear in late July to September and have green eyes and green veins on their wings.
Cicadas are not harmful to us; they don’t sting or bite (they actually don’t feed as adults). However, they can cause damage to trees and may kill recently planted trees and shrubs. While they don’t feed on trees and shrubs, female cicadas cut slits in twigs and insert their eggs. The damaged twigs often brown and die soon after. A large tree can tolerate this damage, but younger trees may not. It’s recommended to cover susceptible tree plantings during the cicada breeding period (or delay planting).
It may seem odd for cicadas to lay eggs in twigs, as the newly hatched cicada nymphs don’t feed on them and soon fall to the ground after hatching. However, by laying eggs on tree twigs, it guarantees that the nymphs will land above tree roots, where they can burrow down and feed for another 17 years.
By the way, the male cicada mating call comes from two hard membranes on either side of its abdomen called tymbals. That’s the ruckus!
For more information on periodical cicadas, see the Penn State Extension website: https://extension.psu.edu/periodical-cicada
About the Author
Greg Podniesinski is chief of the Natural Heritage Section of the PA Department of Conservation and Natural Resources – Bureau of Forestry, as well as State Director of the PA Natural Heritage Program. Podniesinski has worked for the Bureau for the last six years, and a total of 10 years with DCNR. He has also spent 20 years working with the PA Natural Heritage Program. Podniesinski earned his B.S. in Biology from the University of Notre Dame, his M.S. in Zoology from the University Of Maine and his Ph.D. in Environmental Science from the SUNY College of Environmental Science and Forestry at Syracuse. He has a particular interest in plant community ecology, floodplains, fens, bogs, shale and serpentine barrens, and is especially fond of native orchids and serpentine barren plants. Learn more about DCNR here.
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