It is possible that Brood XI is not extinct. Brood XI hasn’t been recorded since in 1950’s, however, David Marshall of the University of Connecticut “would not be surprised if there are small patches of them that have been missed since much of southern New England is not that densely inhabited”.
If you’re in the Connecticut, Massachusetts, or Rhode Island area this spring and you hear or see a Magicicada, please let us know.
1907 Map of Brood XI from Marlatt, C.L.. 1907. The periodical cicada. Washington, D.C. : U.S. Dept. of Agriculture, Bureau of Entomology.