On 10 May, I had my first sighting of this year’s periodical cicada in Northern Virginia. For seventeen years, three species of Magicicada, the periodical cicada (M. septendecim, M. cassinii, M. septendecula), have been living about 61 cm (2 feet) underground beneath trees across portions of eastern North America. In May 2021, individuals in Brood X (sometimes known as the Great Eastern Brood) began to emerge in the trillions from their long sojourn when soil temperature reached a consistent temperature of 18 degrees C (64 degrees F) or higher.
The last time Brood X emerged was in 2004. For those who witnessed that appearance, or previous ones, Brood X at times feels like a science fiction movie with the creatures swarming and the loud (up to 90 decibel) mating song of the males drowning out conversations (I wonder how the rest of the world will react to our Zoom call being joined by singing cicadas!).
Magicicada are mostly harmless, neither biting nor stinging. Members of the order Hemiptera, the nymphs spend their underground life harmlessly consuming xylem fluids from the roots of deciduous forest trees; the adult female, which deposits its eggs in small slits cut into the ends of branches, rarely causes damage to mature trees and there is speculation that the cicada pruning leads to more abundant leafing and fruiting the following year.
Known to Native Americans for generations, the first known mention of periodical cicada literature is by William Bradford, governor of Plymouth Colony in 1633 (Kritsky 2001, 1). A more detailed (and somewhat inaccurate) account was printed thirty-three years later in the Philosophical Transactions (London) in 1666 by Henry Oldenburgh:
A great Observer, who hath lived long in New England, did upon occasion, relate to a Friend of his in London, where he lately was, That some few Years since there was such a swarm of a certain sort of Insects in that English Colony, that for the space of 200 Miles they poson’d and destroyed all the Trees of that Country; there being found innumerable little holes in the ground, out of which those Insects broke forth in the form of Maggots, which turned into Flyes that had a kind of taile or sting, which they struck into the Tree, and thereby envenomed and killed it. (Oldenburgh 1666, 137)
The first significant documentation by Europeans of what came to be known as Brood X occurred in Philadelphia in 1715 when they were reported by Reverend Andreas Sandel (Kritsky 2021, p.53). In 1748, the Swedish naturalist, Pehr Kalm, travelled to North America to observe the 1749 emergence of Brood X. Kalm comments:
You could hardly find one tree, not in gardens or in the forest, where the trunks were not covered with them. Some had just come out of their shells, while others were still in the process of emerging, so they were half in and half out. Some had started to try their wings. It was remarkable that on the previous day, May 21st there were none to be found. (Kalm 1756, 107; Translation by E.L. Lewis [Davis, J.J 1953])
Kalm’s account, published in 1756, became the basis for Linné’s first scientific description and classification of the periodicical cicada in the 1758 edition of Systema Naturae (10th ed.). Linné’s classification of the periodical cicada placed it in the genus Cicada.
Additional investigations in the early 20th century led entomologist William T. Davis to look more closely at the taxonomy of the 13- and 17- year cicadas and propose a new genus, Magicicada, for the (then) two species of 17-year cicada and the four species of 13-year cicada. Davis noted in his paper with this revision that:
It is evident from the foregoing that our well known red-eyed Seventeen-Year Cicada does not belong where it has been placed, in fact Distant states in his 1905 paper, already cited, in describing his Division Tibicinaria, that Tibicina septendecim “possesses several aberrant characters.” The writer therefore proposes that this important and interesting species be the type of a new genus and be called Magicicada septendecim (Linn.). (Davis 1925, 44)
The term “Brood X” evolved from naturalists trying to make sense of the different emergences across the cicada range. C.L. Marlatt in his important work on cicadas notes:
Of the upward of twenty broods which have been differentiated, most of them have been carefully studied, chronological records collected, and the limits of distribution fairly well determined. For convenience of reference, these broods have been designated by Roman numerals, as Brood VI, Brood XXVI, etc. (Marlatt 1898, 19)
Cicada septendecim was the single species of periodical cicada described by Linné in 1758. A second species in the genus, M. cassinii, was described and published by J.C. Fisher in 1852 and named after his friend and fellow observer, the ornithologist, John Cassin. But, should Fischer and Cassin really get full credit for this discovery? In the 9 May 2021 issue of Scientific American, Catherine McNeur argues that Pennsylvania entomologist Margaretta Hare Morris’ contribution has been erased and that she deserves the credit for identifying the species that Fisher named, C. cassinii (McNeur 2021).
As women could not be members of the Academy of Natural Sciences (Philadelphia) at the time, Morris’ paper describing her findings was read by Professor Johnson during the 15 December 1846 meeting of the Academy. She was later admitted to the Academy in 1859 (having previously been admitted to the Association for the Advancement of Science in 1850 along with astronomer Maria Mitchell as the two first women members) (Academy of Natural Sciences 1859, 354). Morris’ 1846 paper is important not just for potentially identifying a new species, but for noting the way the cicada larvae attach themselves to the roots of trees for the extended period of time they are underground. Morris clearly describes, though without an explicit description, what she posits is a new species:
The larvae were enclosed in a compact cell of earth, with no outlet except that in immediate contact with the root, and as there were no galleries or holes leading from these cells, I infer that the grubs never leave the roots they first fasten on; which may account for the great difference of size; the small ones being starved specimens of the same brood: though I am inclined to believe that there are two species, differing sufficiently in size to account for the discrepancy in size of the larvae found. I noticed this difference in 1817, and again in 1834: the note of the smaller variety, or species, is much shriller than that of the larger, and will never be mistaken when noticed. (Morris 1846, 133) [emphasis added]
Fisher’s description, published six years later in the Proceedings of the Academy of Natural Sciences, is a more typical species description:
… the attention of its members was directed by Mr. John Cassin to the fact that two species had been confounded, and that the insect regarded as the smaller variety was in fact a distinct species, a conclusion at which he had arrived during their previous appearance in 1834 … I propose on these grounds to characterize the smaller species as follows: — Cicada Cassinii, nobis. ♂ total length of body, 9-10ths of an inch of the wings, 1 2-10ths inches; ♀ frequently smaller. (Fischer 1852, 272)
Following Fisher’s description, Cassin adds his own note, focusing, like Morris, on the differing calls of the species:
It was therefore highly gratifying to me to have an opportunity of calling the attention of gentlemen of this Academy to the smaller species which Professor Fisher has done me the honor of naming as above, and particularly to its note. This is quite different from the prolonged and loud scream of the larger species, (which is C. septendecim, Linn.) and begins with an introductory clip, clip, quite peculiar. No disposition to associate with each other exists between the two species, and although I have seen both on the same tree, yet most frequently they were entirely separated, and occupied different parts of the woods. (Cassin 1852, 273)
Interestingly, Cassin cites an earlier observation by S.P. Hildreth (published in 1830) that delineates two varieties of periodical cicadas differing by size and song:
There appeared to be two varieties of the cicada, one much smaller than the other: there was also a striking difference in their notes. The smaller variety were more common in the bottom lands, and the larger in the hills. A continual scream was kept up by the males during the day, but they were silent through the night. (Hildreth 1830, 48)
Clearly, observers had noted that the apparent single species, M. septendecim, showed evidence that there were perhaps two varieties (as per Hildreth) or, more significantly, species (as per Morris). Fischer and Cassin clearly knew of and cited Hildreth’s observation, but were either unaware of, or consciously ignoring, Morris’ relatively recent paper (ironically presented just a few years earlier at the very Academy of Natural Sciences where their description was published).
Though Morris’ contributions to entomology (including additional publications on cicadas, e.g. Morris 1851) were recognized in her admission to prestigious scientific organizations, her important observations on what would become M. cassinii were lost for many years and her work deprecated. As late as 1947, in a short note on “Early Feminine Entomologists in America”, it is commented that “Her entomological conclusions were not always correct.” (New York Entomological Society 1947, 280)
As a final note, rounding out the three species of periodical cicadas was the description of the third species, Magicicada septendecula, described in 1962 (Alexander and Moore 1962, 9).
The 2021 Brood X appearance provides a great citizen science opportunity. Cicada Safari has been developed by Dr. Gene Kritsky working with the Center for IT Engagement at Mount St. Joseph University in Cincinnati specifically to enable those in the range of Brood X to help naturalists document the appearance this year.
Dr. Kritsky told me that he was drawn to the study of periodical cicadas early in his career:
It started the second week of my general entomology course at Indiana University. It was taught by Frank N. Young, Jr. who was the periodical cicada researcher in Indiana. As Frank started to describe these insects, I had the idea that mining the literature for historical records might prove fruitful in understanding the broods and their relationships to each other. So while in Grad School at Illinois, working under Lewis J. Stannard, Jr., the periodical cicada specialist in Illinois, I started searching. When I left in 1977, I had amassed nearly 7,000 historical records of cicadas! have been very gratified that so many of my colleagues and people around the country have embraced my app, CicadaSafari, to help map out this year’s emergence of Brood X. Here it is May 14, the cicadas have not started their major emergence in parts of their range and over 111,000 people are using the app and contributing 5,000+ -photos per day.
Being based at the Smithsonian, I also checked in with Floyd Shockley, the collections manager for the Department of Entomology at the Smithsonian’s National Museum of Natural History, and asked what drew him to study the periodical cicada:
As Collections Manager, I am a broadly trained entomologist rather than a specialist on cicadas (my research focus is actually on beetles). However, I grew up on a small farm in rural Missouri and spent a lot of my childhood outside and exploring nature. I was a naturalist and a scientist even then. Cicadas were always a quintessential sign of summer back home, and given their size they were larger than most other insects so it was easy to find them and “study” them. We also have several broods of periodical cicadas that emerge in Missouri so I got to see them more than most. In fact, I’ve personally experienced 9 of the 15 extant broods of periodical cicadas during my life.
The regular appearance of periodical cicadas over, for most species, what is a significant amount of time means that individual researchers will not have an opportunity to study them over multiple generations. The accumulation of observations and data over decades and even centuries makes the study of periodical cicadas possible.
The importance to researchers of repositories, such as the Biodiversity Heritage Library, that aggregate vast amounts of data gathered over long periods of time is inestimable. BHL allows researchers around the world to access literature that may be difficult or impossible to find locally or easily. Access, whether through metadata or full-text searching, uncover data that might otherwise be lost. As we saw with M. cassinii, it can also help with providing a richer story to the documenting of life on our planet.
References and Additional Suggested Readings
Academy of Natural Sciences (Philadelphia). 1859. Elections in 1859. 1: 354. https://www.biodiversitylibrary.org/page/1653313
Alexander, R.D., Moore, T.E. 1962. The evolutionary relationships of 17-year and 13-year cicadas, and three new species (Homoptera, Cicadidae, Magicicada). Misc. Publs Mus. Zool. Univ. Mich. 121: 1-59. https://deepblue.lib.umich.edu/bitstream/handle/2027.42/56365/MP121.pdf?sequence=4
Cassin, John. 1852. Note on the above species of Cicada, and on the Cicada septendecim, Linn. Proceedings of the Academy of Natural Sciences of Philadelphia. 5: 273-275. https://www.biodiversitylibrary.org/page/26301508
Davis, J.J. May 1953. Pehr Kalm’s Description of the Periodical Cicada, Magicicada septendecim L., from Kongl. Svenska Vetenskap Academiens Handlinger, 17:101-116, 1756, translated by Larson, Esther Louise (Mrs. K.E. Doak). The Ohio Journal of Science. 53: 139–140. https://kb.osu.edu/handle/1811/4028
Davis, W.T., 1925. Cicada tibicen, a South American species, with records and descriptions of North American cicadas. Journal of the New York Entomological Society. 33: 35-51. https://www.biodiversitylibrary.org/page/50783180
Dybas, Henry. (1970). Population explosion — 17-year locust style. Bulletin (Field Museum of Natural History) 41.1: 11-13. https://www.biodiversitylibrary.org/page/2890663
Fisher, J.C. 1852. On a new species of cicada. Proceedings of the Academy of Natural Sciences of Philadelphia. 5: 272-273. https://www.biodiversitylibrary.org/page/26301507
Hildreth, S.P. 1830. Notices and Observations on the American Cidada, or Locust. The American Journal of Science and Arts. 18: 47-50. https://www.biodiversitylibrary.org/page/30953560
Kalm, Pehr. 1756. Beskrifning På et slags Grås-hoppor uti Norra America. Kungl. Svenska vetenskapsakademiens handlingar. 17:101-116. https://www.biodiversitylibrary.org/page/46677076
Kritsky, Gene. 2001. Periodical Revolutions and the Early History of the “Locust” in American Cicada Terminology. American Entomologist, pp. 1-4. https://doi.org/10.1093/ae/47.3.186
Kritsky, Gene. 2021. Periodical Cicadas: The Brood X Edition. Ohio Biological Survey. http://www.worldcat.org/oclc/1246784386.
Linnaei, Caroli. 1758. Insecta. Hemiptera. Cicada. Mannifera. septendecim. Systema Naturae Per Regna Tria Naturae, Secundum Classes, Ordines, Genera, Species, Cum Characteribus, Differentiis, Synonymis, Locis. 1 (10 ed.). Stockholm, Sweden: Laurentii Salvii. pp. 436–437. https://www.biodiversitylibrary.org/page/727347
McNeur, Catherine. May 9, 2021. The Woman Who Solved a Cicada Mystery—but Got No Recognition. Scientific American. https://www.scientificamerican.com/article/the-woman-who-solved-a-cicada-mystery-but-got-no-recognition/
Marlatt, C.L. 1898. The periodical cicada: an account of Cicada septendecim, its natural enemies and the means of preventing its injury: together with a summary of the distribution of the different broods. Publication info: Washington, D.C. :U.S. Dept. of Agriculture, Division of Entomology,1898. https://www.biodiversitylibrary.org/page/48892673
Morris, Margaretta Hare. 1846. Stated Meeting, Dec. 15, 1846. Mr. Vaux in the Chair. Proceedings of the Academy of Natural Sciences of Philadelphia. 3: 131-34. https://www.biodiversitylibrary.org/page/1659400
Morris, Margaretta Hare. 1851. On the Seventeen Year Locusts. Proc. Bos. Soc. Nat. Hist. 4: 110. https://www.biodiversitylibrary.org/page/8870820
New York Entomological Society. 1947. Early Feminine Entomologists in America. Journal of the New York Entomological Society. LV: 280. https://www.biodiversitylibrary.org/page/50768578
Oldenburgh, Henry. 1666. Some Observations of swarms of strange Insects, and the Mischiefs done by them. Philosoph. Trans. London, l(8): 137-38. https://www.biodiversitylibrary.org/page/47594106
Snodgrass, R.E. 1930. The Periodical Cicada. Insects, their ways and means of living. (Smithsonian scientific series, v.5). https://www.biodiversitylibrary.org/page/41170136
BugGuide. Genus Magicicada – Periodical Cicadas. https://bugguide.net/node/view/6970
Catalogue of Life. Magicicada. https://www.catalogueoflife.org/data/browse?taxonKey=5K4G
CicadaMania. A commercial site that has good information about cicadas in general as well as the 2021 Brood X appearance. https://www.cicadamania.com/
Cicada Safari. Companion site to the Cicada Safari app, there’s lots of good information here as well. https://cicadasafari.org/
General Periodical Cicada Information (University of Connecticut). https://cicadas.uconn.edu/
And Brood X map https://cicadas.uconn.edu/brood_10/
iNaturalist Periodic Cicadas. The website for the citizen science app for Magicicada. https://www.inaturalist.org/taxa/83854-Magicicada
Smithsonian National Museum of Natural History. Good information from the Smithsonian on cicadas. https://www.smithsonianmag.com/blogs/national-museum-of-natural-history/2021/04/15/what-expect-when-cicadas-emerge-spring/