The life cycles of periodical cicadas require either 17 or 13 years to complete, depending on the species. Scientists sort these cicadas into broods (i.e., cohorts) based on when they emerge and label them with Roman numerals. Of the 15 broods that exist, 12 have 17-year life cycles and a more northern distribution while three have 13-year life cycles and a more southern distribution.

In certain locations, the 17-year broods and 13-year broods of periodical cicadas overlap; occasionally, they emerge in the same year. Spring 2024 was unique in that Brood XIII (17-year) and Brood XIX (13-year) both emerged, and their ranges overlapped in central Illinois. The last time this happened was in 1803, when Thomas Jefferson was president of the United States.

Learn more on the Periodical Cicadas in Wisconsin page.

This article was posted in Healthy Ecosystems, Number Crunching, Summer 2024 and tagged cicadas, Entomology.