Periodical cicadas are native to eastern North America and mass emerge in in huge broods. Cicadas do not bite people and are usually at most a mild nuisance because of the noise they produce. Young trees can sometimes be damaged or killed, but this can usually be avoided by delaying transplant or covering at-risk trees with netting.
- Common name: Periodical cicada
- Scientific name: Magicicada species
- Order: Hemiptera (true bugs)
- Family: Cicadidae (cicadas)
Periodical cicadas are native to eastern North America and are found nowhere else. There are seven species, three of which have 17-year lifecycles and four of which have 13-year lifecycles. 17-year cicadas generally have a northern distribution while 13-year cicadas are more southern, although they exhibit considerable overlap in the middle of the United States from North Carolina and Georgia west to Missouri and both types may be found in the same forest. Three species of 17-year cicadas occur in Pennsylvania and may emerge at the same time.
Adult periodical cicadas are about one and one-half inches long, mostly black in color with reddish-orange eyes and wing veins (Figure 1). Periodical cicadas may be confused with various species of annual cicadas, which emerge every year. However, they can be distinguished based on size, color, and emergence time: annual cicadas are larger with greenish wing veins (Figure 2) and emerge from July through September instead of late May through early June.
Figure 1. Periodical cicada (Magicicada septendecim). Photograph by Matt Bertone, used with permission.
Figure 2. Annual cicada (Neotibicen species). Photograph by Matt Bertone, used with permission.
Three species of periodical cicada occur in Pennsylvania and can be distinguished based on differences in color and the songs of the males (Figure 3). Magicicada septendecim are the largest species. They have wide orange bands on the abdomen that are equal to or wider than the black bands and typically have an orange spot on the side of the pronotum. Magicicada septendecula are smaller than M. septendecim, have narrow orange bands on the abdomen, and lack an orange spot on the side of the pronotum. Magicicada cassinii are also smaller than either M. septendecim and usually have entirely black abdomens that lack orange bands (thing yellow bands may occasionally be present) and like M. septendecula, they also lack an orange spot on the side of the pronotum. To hear the differences in the songs of the males, listen to the examples of cicada calls on Cicada Mania.
Figure 3. How to distinguish the three 17-year cicada species. Image produced by Chao Wu, used with permission.
Life history and behavior
Periodical cicada nymphs live in the soil at depths of two to twenty-four inches, where they feed on sap from tree roots. When nymphs determine it is the year to emerge, they burrow to about an inch beneath the soil surface in April. If the ground is too damp, the mature nymphs build a protective earthen turret, which can help identify where cicadas will emerge (Figure 4). When the soil temperature reaches 64°F, the nymphs exit the ground and crawl a foot or more up tree trunks, weeds, or other upright objects. In Pennsylvania, this usually occurs in late May or early June, depending on how warm or cold spring temperatures were. The adult cicadas then shed the nymphal exoskeleton, which is left behind, in an hour or less. At this point, the cicadas are soft, white, and unable to fly as the exoskeleton takes a few hours to harden (Figure 5). Once the exoskeleton is hardened the adults are capable of flying but are rather clumsy fliers and often collide into objects. This makes them easy prey for various birds, which gorge themselves on the cicadas. While stragglers may emerge a few days earlier or later, the main emergence of a periodical cicada brood often occurs over one or just a few nights.
Figure 4. Periodical cicada turrets. Photograph by John Pearson via Bugguide, used under a CC BY-ND-NC 1.0 license.
Figure 5. Cicada molting (annual cicada shown but the process is the same for periodical cicadas). Photograph by Matt Bertone, used with permission.
Soon after emerging, males begin to sing while females remain silent. About 10 days after emergence, females mate and begin depositing eggs in twigs and branches of various trees and woody shrubs. Using a saw-like ovipositor, a female cicada cuts a small pocket into a twig, in which she deposit 24-28 eggs. She then moves forward, cuts another pocket, and lay more eggs (Figure 6). The pockets are placed close together in a straight row and sometimes form a continuous slit for two to three inches (Figure 7). Adults periodical cicadas live for three to four weeks above ground and each female can lay 400-600 eggs over a lifetime
Figure 6. Female periodical cicada laying eggs in a tree branch. Photograph by Lacy L. Hyche, Auburn University via wtbblue.com. Used under a CC BY-NC 3.0 license.
Figure 7. Periodical cicada damage to a tulip tree branch. Photograph by Tim Tigner, Virginia Department of Forestry via wtbblue.com. Used under a CC BY-NC 3.0 license.
The eggs hatch six to seven weeks after they are laid. The white, ant-like nymphs work their way out of the twig slits, drop to the ground, and enter the soil, where they feed on fluids from plant roots for the next 17 years.
Periodical cicadas are clumsy fliers and easy prey for a variety of birds and other insect-eating predators. Mass emergence of periodical cicadas is therefore thought to be a form of predator avoidance – if millions of cicadas emerge at the same time, predators quickly eat their fill and leave the vast majority of cicadas alone to reproduce. This idea is supported by the fact that early- or late-emerging cicadas are generally not numerous enough to successfully reproduce because most of them are eaten.
While individual periodical cicadas typically live for 13 or 17 years, mass emergences of periodical cicadas usually happen somewhere in the eastern United States every year (Figure 8). Each yearly emergence is referred to as a “brood” and is designated by a Roman numeral. The numerals I through XVII (1-17) are assigned to the 17-year broods, and XVIII through XXX (18-30) to the 13-year broods. The numbering of the 17-year broods began with the 1893 brood, which was designated as Brood I. In 1909, Brood XVII appeared, and in 1910, Brood I appeared again. There are at least 13 broods of 17-year cicadas and five broods of 13-year cicadas. Because the broods are designated by Roman numerals, they should be spoken as numbers. For example, Brood X is “Brood Ten” and not “Brood Ex”.
Figure 8. Periodical cicada broods. Image by A. M. Liebhold, M. J. Bohne, and R. L. Lilja, USDA Forest Service. Public Domain.
Eight different periodical cicada broods exist in Pennsylvania (see list below), all of which require 17 years to reach maturity. Several of these broods are very small. Brood X, known as the “great eastern brood,” is a large brood that emerges across 15 states and has heavy concentrations in eastern Pennsylvania.
Periodical cicada broods of Pennsylvania and next emergence year.
- Next emergence: 2025—Brood Number: XIV Counties where cicadas may emerge: Adams, Bedford, Berks, Blair, Centre, Clearfield, Clinton, Cumberland, Franklin, Huntingdon, Lackawanna, Lehigh, Luzerne, Lycoming, Mifflin, Montour, Northumberland, Perry, Potter, Schuylkill, Snyder, Tioga, Union, and York Counties
- Next emergence: 2029—Brood Number: I. Counties where cicadas may emerge: Adams, Cumberland, and Franklin Counties
- Next emergence: 2030—Brood Number: II. Counties where cicadas may emerge: Berks, Bucks, Carbon, Chester, Dauphin, Delaware, Lancaster, Lebanon, Lehigh, Luzerne, Monroe, Montgomery, Northampton, Philadelphia, Pike, Schuylkill, and Wyoming Counties
- Next emergence: 2033—Brood Number: V. Counties where cicadas may emerge: Fayette, Greene, Somerset, Washington, and Westmoreland Counties
- Next emergence: 2034—Brood Number: VI. Counties where cicadas may emerge: Bucks, Dauphin, Lancaster, Lehigh, Montgomery, Northampton, Philadelphia, and Westmoreland counties
- Next emergence: 2035—Brood Number: VII. Counties where cicadas may emerge: Allegheny, Butler, Washington, and Westmoreland Counties
- Next emergence: 2036—Brood Number: VIII. Counties where cicadas may emerge: Allegheny, Armstrong, Beaver, Butler, Cambria, Clarion, Crawford, Fayette, Forest, Huntingdon, Indiana, Lawrence, Mercer, Venango, Washington, and Westmoreland Counties
While the majority of the cicadas associated with each brood emerge every 13 or 17 years, individuals of any given brood may emerge 1-4 years early or late. The largest off-year emergences are associated with a four-year acceleration of 17-year cicadas that emerge after 13 years, although emergences of 13-year cicadas after nine years are also known. It's thought these accelerations and decelerations are associated with brood formation, such that when enough cicadas of a given brood emerge off-cycle they can form a new brood or join an existing brood. Recently published genetic evidence that supports this hypothesis showed that Brood V actually consists of at least four genetic subpopulations that are derived from portions four broods that accelerated or decelerated to join Brood V.
While some overlap of broods occurs, especially along margins where two broods meet, different broods are largely geographically isolated and connect like puzzle pieces across eastern North America. It's unclear why this occurs, especially in light of multi-year brood accelerations and decelerations, which should in theory produce parent-offspring broods that overlap in geographic area. There have been some suggestions that nymphs may compete for resources underground so that it is difficult for cicadas of different broods to overlap geographically but the mechanisms that keep broods separated need to be studied in much more detail.
Off-cycle emergences and the associated genetic underpinnings are also likely related to species formation. The closest relative of each 13- and 17-year cicada species is a species with the opposite yearly cycle, such that there are three pairs of 13- and 17-year sibling species (with one pair involving a second 13-year species that has a limited geographic range) (Figure 9). In fact, the 13- and 17-year species in each group are morphologically indistinguishable and best identified by the broods they emerge with. This close relationship between 13- and 17-year cicadas has been recognized for so long it was even incorporated into the names of the individual species: for example, the Decula group species are Magicicada septendecula and Magicicada tredecula. Genetic evidence has shown that the splits between species groups occurred 4 million and 2.5 million years ago, while the oldest split between a 13- and 17-year species happened approximately 500,000 years ago. So the species groups split from each other and existed for 2-3.5 million years before each of the three groups independently split again into 13- and 17-year species relatively recently. Other studies of periodical cicada DNA have shown that the species in each species group share certain genes that indicate occasional mating and gene flow between 13- and 17- year species.
- Magicicada septendecim (17 year species)
- Magicicada tredecim (13 year species)
- Magicicada neotredecim (13 year species)
- Magicicada septendecula (17 year species)
- Magicicada tredecula (13 year species)
- Magicicada cassini (17 year species)
- Magicicada trecassini (13 year species)
Figure 9. Periodical cicada species groups. Figure composed by Michael Skvarla, Penn State University.
So while it was once thought that cicada broods were largely static and unchanging, it is becoming increasingly clear that periodical cicada broods and even our concept of what species exist is much more complicated. The ranges of broods changing over time; accelerated or decelerated emergence times can lead to populations merging, the formation of new broods, and possible new species forming; and potential competition between cicadas of different broods along the boundaries between broods. The increasing use of community science to map where periodical cicadas emerge and DNA tools to tease apart how cicadas of different broods are related will continue to shed light on this complicated biological web.
Threat to human health
Cicadas do not bite or sting and are not a threat to people or pets.
Damage to trees
Female cicadas cut slits into twigs and stems of woody plants into which they oviposit (lay eggs). They prefer stems that are 3/16″ to 7/16″ in diameter. The slits the females create can appear as short punctures or extent up to 2-3 inches. While annual cicada oviposition does not usually damage trees, periodical cicadas emerge in such high numbers that they can collectively cause heavy damage that results in twig and stem dieback (Figure 10). Large, otherwise healthy trees can withstand this damage without long-term consequences, although they may be aesthetically unpleasing for a time. However, small trees that have a majority of the branches within the cicadas' preferred size range can be severely affected and sometimes be killed. This is especially true of small, stressed trees, such as those that have been recently transplanted or are balled and burlapped in preparation for sale or transplantation.
Figure 10. Twig and branch dieback caused by periodical cicada oviposition. Photograph by Daniel Herms, The Ohio State University via wtbblue.com. Used under a CC BY-NC 3.0 license.
Deciduous trees are preferred hosts, especially oaks, maples, apples, and other trees that often have twigs of the appropriate size, although cicadas are not too picky and have been recorded to oviposit in more than 80 different species. Periodical cicadas do not usually deposit eggs in coniferous trees, although coniferous hosts are not totally unknown.
A periodical cicada year is a time of feasting for an array of creatures. Grackles, crows, and other birds dine voraciously on the adults, while fish will literally gorge themselves on cicadas when they are abundant in trees and shrubs along a stream. However, the large number of cicadas present is likely to outstrip the ability of predators in a given area to effectively control the insects. That's the whole point of the cicadas mass emerging as a brood afterall.
If possible, transplanting trees should be avoided the fall and spring before a periodical cicada emergence. Pruning trees should also be avoided during this time as branches injured by cicadas can be pruned out after they die off.
Trees under 10 feet tall can be protected by netting with ½” mesh to exclude the cicadas (Figure 11). Netting should be applied before cicada emergence and kept on the 4-6 weeks cicadas are present. In most cases, netting trees is more effective than spraying chemical pesticides in terms of cost and damage reduction.
Figure 11. Trees protected against cicada damage by mesh netting. Photograph by James B. Hanson, USDA Forest Service via wtbblue.com. Used under a CC BY-NC 3.0 license.
Although not as effective as netting, chemical pesticides can be used to reduce damage to small trees when netting is not practical, such as in a large fruit orchard. Chemical control is almost never more effective as netting for private homeowners who want to protect a handful of trees. When used, chemical pesticides often need to be applied every 2-3 days as new cicadas immigrate from nearby areas. Chemical pesticides can also kill beneficial mites and insects, which can exacerbate pest issues later in the season. For more information about the use of chemical pesticides, especially in tree fruit situations, please refer to this Penn State fact sheet .
Pesticide applications are not recommended for large, otherwise healthy trees as they can withstand the pressure of cicada oviposition with little to no long-term effects and any aesthetic damage is ephemeral.
Pesticides are poisonous. Read and follow directions and safety precautions on labels. Handle carefully and store in original labeled containers out of the reach of children, pets, and livestock. Dispose of empty containers right away, in a safe manner and place. Do not contaminate forage, streams, or ponds.
The first version of this fact sheet was written by Greg Hoover in 2013 and was heavily revised and updated by Michael Skvarla in 2021.
References and additional reading
Du, Z., H. Hasegawa, J.R. Cooley, C. Simon, J. Yoshimura, W. Cai, T. Sota, and H. Li. 2019. Mitochondrial genomics reveals shared phylogeographic patterns and demographic history among three periodical cicada species groups. Molecular Biology and Evolution 36(6): 1187-1200.
Kritsky, G. 2004. Periodical cicadas: the plague and the puzzle. Indiana Academy of Science, Indianapolis, Indiana. 147 pp.
Kritsky, G. 2021. Periodical Cicadas: The Brood X Edition. Ohio Biological Survey, Columbus, Ohio. 154 pp.
Marshall, D.C., K.B.R. Hill, and J.R. Cooley. 2017. Multimodal Life-Cycle Variation in 13- and 17-Year Periodical Cicadas (Hemiptera: Cicadidae: Magicicada). Journal of the Kansas Entomological Society 90(3): 211-226.
Mozgai, D. 2021. Cicada Mania. Accessed 23 March 2021.
Sadof, C. 2021. Periodical cicada in Indiana. Purdue University fact sheet, E-47-W. Accessed 23 March 2021.
Sota, T., S. Yamamoto, J.R. Cooley, K.B.R. Hill, C. Simon, and J. Yoshimura. 2013. Independent divergence of 13- and 17-y life cycles among three periodical cicada lineages. PNAS 110(17): 6919-6924.
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