Brood XXI
Brood XXI (also known as the Floridian Brood) was a brood of 13-year periodical cicadas that inhabited the Florida Panhandle and the area around the Alabama–Mississippi border. It was last seen in 1870 and is presumed extinct. Brood XXI was only one of four 13-year broods prior to extinction. The surviving three are Brood XIX (the "Great Southern Brood"), Brood XXII (the "Baton Rouge Brood"), and Brood XXIII (the "Mississippi Valley Brood").