Maps of Two Cicada Broods, Reunited After 221 Years
Historic maps adapted from “The Periodical Cicada,” by Charles L. Marlatt, 1907, via the Biodiversity Heritage Library; modern brood maps adapted from Gene Kritsky, Mount St. Joseph University
Charles L. Marlatt proposed using Roman numerals to identify the regional groups of 13- and 17-year periodical cicadas, beginning with Brood I in 1893.
A brood can include up to three or four cicada species, all emerging at the same time and singing different songs. Long cicada lifespans of 13 or 17 years spent underground have spawned many theories, and may have evolved to reduce the likelihood of different broods surfacing at the same time.
Large broods might sprawl across a dozen or more states, while a small brood might only span a few counties. Brood VII is the smallest, limited to a small part of New York State and at risk of disappearing.
Brood XIII and Brood XIX will emerge together this year, for the first time in more than two centuries. But only in small patches of Illinois are they likely to come out of the ground in the same place.
