Brood XXIII

Brood XXIII (also known as the Mississippi Valley Brood) is a brood of 13-year periodical cicadas that last emerged in 2015 around the Mississippi River in the states of Louisiana, Mississippi, Arkansas, Tennessee, Missouri, Kentucky, and Illinois.

The brood was also seen in Southwestern Indiana and Western Kentucky around the Ohio River, and as far north as Weldon Springs State Park in DeWitt County, Illinois.

Every 13 years Brood XXIII cicadas tunnel en masse to the surface of the ground in late-April to early-June of emergence years to molt, mate, lay eggs, and subsequently die off over the course of a few weeks.

After the eggs hatch, the nymphs burrow back underground to further develop and grow for the next 13 years before emerging again, completing the cycle.

The extreme number of emerging cicadas is often given as an example of predator satiation.