By: Emma Cockerill
Summary. Brood X debuted in North America with a mighty chorus earlier this summer. Trillions of Cicadas emerging across North America after 17 years underground did not disappoint. Blanketing the North East, Mid-Atlantic and Mid-West regions, the unmistakable sound of male Cicadas battling for attention filled the air. Cicadas are unmistakably loud, their song can reach 100 decibels, almost as loud as an ambulance siren. Brood X is particularly important as it is the largest of all Cicada broods. Broods are groups of Cicada which emerge either annually or periodically depending on the species. Periodical broods are groups of Cicadas which share the same years of emergence after a period of time. There are 15 periodicals which emerge on either a 17-year or 13-year cycle. During their time a couple of feet underground, nymph Cicadas develop and feed on sap from tree roots. On the year of emergence when the soil temperature hits about 64⁰F, after soaking rain, Cicada’s tunnel to the surface to mature and grow wings. It is a survival strategy of Cicadas to emerge in such large groups for predator protection. The purpose is to overwhelm the potential predators with a great number in the hopes that enough will survive to reproduce. Broods are numbered by Roman numerals corresponding to the emergence year since records began in the late 1800’s. Given each Broods scarce visibility over such long periods of time, research during the scheduled year of emergence is critical. Ecologists have been anticipating the arrival of Brood X in 2021, a unique opportunity to take advantage of technologies not in existence 17 years ago. Cicadas are harmless and native to North America and have been tracked and cataloged by scientists and citizens alike for over a hundred years. Not until recently, however, does every person have a smart phone with a camera and GPS. Citizen science was of great importance this year, with every willing person able to take a picture and upload the location of Brood X to community maps. Two mapping programs were created in preparation for Brood X’s arrival earlier this year. Cicada Safari and iNaturalist both launched free apps for citizens to participate, yielding results never possible 17 years ago. Tracking Brood X and comparing to historical maps can give us clues to how urbanization and climate change has affected the biodiversity and habitability of the land.
Why we should care? Cicadas are an indication of environmental health and provides essential ecosystem services. As humans ravage the landscape, it is more important than ever to preserve the Cicadas for our own benefit.
Howard Russell is interviewed in this article by Michigan Radio in April, before the emergence of Brood X began. Russell is an Entomologist at Michigan State University. He explains the historical Brood X distribution specific to Michigan and why it is so important to preserve our mature trees. Cicadas need mature trees for their roots as a food source when burrowed underground. Deforestation in the Mid-West has limited habitats available for many broods. Russell also revealed that past cycles of Brood X in Michigan have been sighted in Washtenaw, Lenawee, Genesee, Oakland and Livingston Counties. He explained that undisturbed preserves such as Cherry Hill Nature Preserve near Ann Arbor provides the perfect accommodation for the insects to live.
Science in Action.
Dr. Gene Kritsky is the Dean of Behavior and Natural Sciences Mount Saint Joseph University, Cincinnati, Ohio.
Dr. Kritsky is an entomologist who has published numerous books and journals on insects and evolution. This year, he published a book on Brood X, ‘Periodical Cicadas: The Brood X Edition’. He has studied Cicada brood history over many centuries. His previous research in Ohio discovered that the distribution of 17-year periodical Cicadas match the geographic regions created by the ice ages. Kritsky and his colleagues developed the app, Cicada Safari, to track sightings during the Brood X emergence. He explains the importance of tracking Brood X as the distribution is an indication of how their survival is faring. Periodical broods are fairly resistant to climate change but Kritsky insists habitat loss is the main threat to Brood X due to deforestation.