Periodical cicadas are insects that belong to the order Hemiptera, which includes the stink bugs, bed bugs, aphids, and cicada families.
What makes periodical cicadas so fascinating, is their long life cycle. After hatching, the immature cicadas, called nymphs, spend 17 or 13 years underground feeding on roots, before emerging in May and transforming into adult cicadas.
Periodical cicadas were first recorded by the Pilgrims at Plymouth Colony in 1634, but they were known to the Native Americans for centuries prior to European contact. Brood X was first reported in 1715 in Philadelphia.
The photos below show a cicada nymph in the fall of its 16th year, a 17-year old nymph that has just emerged from the ground, an adult cicada that has not yet completed it transformation, a large number of adult cicadas on a shrub, and the empty shells that remain after the adult emerges.
Join Cicada Safari to help map the 2021 emergence of the periodical cicada Brood X. Simply download the free app from the Apple app store or Google play, then go on a safari to find periodical cicadas. Photograph and submit the periodical cicadas to Cicada Safari, and after the photos are verified, they will be posted to the live map. Cicada Safari was created by Dr. Gene Kritsky working with the Center for IT Engagement at Mount St. Joseph University in Cincinnati.
Brood X is the largest of the 17-year cicada broods, occurring in parts of 15 states. Periodical cicadas emerge in large numbers when the soil temperature reached 64º F and often after a soaking rain.
The soil temperature reaches the critical temperatures in the more southern locations first. The cicadas are expected to start emerging in early May in the southern states, in mid-May in southern Indiana and Ohio, and a week later in northern Indiana, Maryland, Pennsylvania and New Jersey .
• There are three species of 17-year cicadas. They are named Magicicada septendecim, Magicicada cassini and Magicicada septendecula.
There are four species of 13-year cicadas. They are named Magicicada tredecim, Magicicada neotredecim, Magicicada tredecassini, and Magicicada tredecula.
• Groups of cicadas that share the same emergence years are called broods. The brood number is usually given in Roman numerals. Charles Marlatt, an entomologist working for the Department of Agriculture, designated that all the cicadas that emerged in 1893 and at 17-year intervals thereafter as Brood I [one]. The cicadas that emerged in 1894 were called Brood II [two] and so on. The 13-year cicadas that emerged in 1894 were called Brood XVIII [eighteen] and so on. The cicadas that will this year in 2021 belong to Brood X [ten].
• Not all cicadas count the years correctly. In 2000, based on collections of cicada nymphs during their 17 years underground, Dr. Gene Kritsky predicted that thousands of cicadas would emerge four years early in May of 2000. That did, indeed, occur, and in five locations the numbers that emerged were so great that the cicadas sang, mated, and laid eggs. The natural question that followed, was will these early offspring keep a 13-year life cycle or shift back to 17 years? In 2013, a few hundred cicadas emerged, but the adults were all eaten by predators and no singing and mating occurred. It was a different matter in 2017, when more of the offspring of the early 2000 cicadas emerged and were joined by newly accelerated Brood X cicada that were emerging four years before the next Brood X emergence in 2021. In 2017, there were 33 locations in SW Ohio where periodical cicadas emerged in numbers large enough to satiate predators, sing, mate, lay, eggs, and the eggs hatch. This is now a new population of Brood VI in SW Ohio. We will be waiting until 2034, to see if this population becomes permanent.
• Only the male cicadas sing. They have sound-producing structures called tymbals on either side of the abdomen.
• It is easy to tell male cicadas from female cicadas. To do so turn the cicada over: the female will have a groove in which is found the ovipositor; the male’s abdomen will terminate with a square shaped flap
• Adult cicadas do not eat solid food, but do drink fluids to avoid dehydration.
• Adult cicadas do not sting or bite humans, and they do not carry diseases. But they can harm young trees when female cicadas lay their eggs in the tree’s new growth. It is not recommended that you spray to kill the cicadas, because they fly into a tree to lay their eggs and spraying will not kill these incoming cicadas. If you have a young tree, you can loosely wrap the branches with cheesecloth to keep the female from laying her eggs.
• Pesticides are not effective at controlling periodical cicadas. They are not pests and do not need to be killed.
• Periodical cicada years are quite beneficial to the ecology of the region. Their emergence tunnels in the ground acts as a natural aeration of the soil. The large number of adult cicadas provides a food bonanza to all sorts of predators, which can have a positive impact on their populations. The females’ egg-laying in trees is a natural pruning of the trees that results in the tree producing more flowers and fruit in the following year. Finally, after the cicadas die their decaying bodies contribute a massive amount of nitrogen and other nutrients to the soil.
• Periodical cicadas are best eaten when they are still white, and they taste like cold canned asparagus. Like all insects, cicadas have a good balance of vitamins, are low in fat, and, especially the females, are high in protein.
• Periodical cicadas are often incorrectly called locusts. Locusts are grasshoppers and cicadas are more closely related to aphids than grasshoppers. The term locust started to be used around 1715 in the English colonies, when citizens tried to make sense of the cicada emergences by equating them with the biblical plagues and the fact the John-the-Baptist ate locusts. The Native Americans also ate cicadas.
There are many ways to learn about this wonder of nature. They are useful in teaching biology, mathematics, history, and art. Click on the activities to download free handouts.
Cicada Websites and Books
cicadas.uconn.edu is a fantastic site maintained by Dr. John Cooley. Mapping data submitted to the MSJ Cicada Safari app is shared with cicadas.uconn.edu as part of a combined mapping effort. This site has many links to the major publications about periodical cicadas.
Periodical Cicadas: The Brood X Edition
Available in three versions
Every seventeen years, millions of cicadas rise from the soil of the eastern United States to fly, mate, and fill the air with their noisy song. Periodical Cicadas: The Brood X Edition examines how the study of Brood X cicadas shaped our understanding of these “bugs of history.” First documented in Philadelphia in 1715, Brood X was and is the largest of the 17-year cicada broods, occurring in 15 states that include several major cities. Periodical Cicadas: The Brood X Edition discusses the natural history, evolution, behavior, and distribution of periodical cicadas and provides an overview of the eighteen emergences that have occurred since the brood was first reported. It offers a perfect starting point to learn about these insects and to enjoy them as one of the wonders of our natural world. Published by the Ohio Biological Survey.
Periodical Cicadas: the Plague and the Puzzle covers the history of our understanding of these “bugs of history.” When cicadas were first observed they were thought to predict a plague, but that notion gave way to the puzzle how these insects with their long life cycles evolved. Extensively referenced, this book is the ideal introduction to these insects for those readers wanting more details.
To receive the MSJ press kit, email Dr. Gene Kritsky to obtain the key to the press kit, including high quality photographs. Please provide contact information, and write “Press” in the subject box, and you will be directed to the press webpage.