Science
Maps of Two Cicada Broods, Reunited After 221 Years
This spring, two broods of cicadas will emerge in the Midwest and the Southeast, in their first dual appearance since 1803.
A cicada lays eggs in an apple twig.
“Insects: Their Ways and Means of Living,” by Robert E. Snodgrass, 1930, via the Biodiversity Heritage Library
Brood XIII, the Northern Illinois Brood, hatched and burrowed into the ground 17 years ago, in 2007.
Brood XIX, the Great Southern Brood, hatched in 2011 and has spent 13 years underground, sipping sap from tree roots.
The entomologist Charles L. Marlatt published a detailed map of Brood XIX, the largest of the 13-year cicada broods, in 1907.
Historic map of cicada emergence.
He also mapped the expected emergence of Brood XIII in 1922.
Historic map of cicada emergence.
This spring the two broods will surface together, and are expected to cover a similar range.
Modern map of cicada emergence.
Up to a trillion cicadas will rise from the warming ground to molt, sing, mate, lay eggs and die.
A Name and a Number
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.
At least two named broods are thought to have vanished: Brood XXI was last seen in 1870, and Brood XI in 1954.
Not Since the Louisiana Purchase
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.
In 1786 and 1790, the two broods burrowed into Native lands, divided by the Mississippi River into nominally Spanish territory and the new nation of the United States.
An historic map of the United States from 1783.
Brood XIII entered the ground in 1786, and Brood XIX in 1790. (Expected 2024 ranges are overlaid on the map.)
An historic map of the United States from 1783.
As the ground was warming in April 1803, France sold the rights to the territory of Louisiana, which it acquired from Spain in 1800, to the United States for $15 million.
An historic map of the United States from 1801. That spring, Brood XIII and Brood XIX emerged together into a newly enlarged United States.
An historic map of the United States from 1803.
Their descendants — 13 and 17 generations later — are now poised to return, and will not sing together again until 2245. An historic map of the United States from 1868.
A ‘Great Visitation’
After an emergence of Brood X cicadas in 1919, the naturalist Harry A. Allard wrote:
Although the incessant concerts of the periodical cicadas persisting from morning until night became almost disquieting at times, I felt a positive sadness when I realized that the great visitation was over, and there was silence in the world again, and all were dead that had so recently lived and filled the world with noise and movement.
It was almost a painful silence, and I could not but feel that I had lived to witness one of the great events of existence, comparable to the occurrence of a notable eclipse or the invasion of a great comet.
Then again the event marked a definite period in my life, and I could not but wonder how changed would be my surroundings, my experiences, my attitude toward life, should I live to see them occur again seventeen years later.
The transformation of a cicada nymph (1), into an adult (10).
“The Periodical Cicada,” by Charles L. Marlatt, 1907, via the Biodiversity Heritage Library