Weeks prior to the mass emergence, Magicicada nymphs will sometimes construct mud chimneys to help evade ground moisture.
These chimneys are hollow in the center which is where the nymphs temporarily reside.
These mud fortresses are usually one to two inches in height but can become several inches tall.
Chimneys usually appear after a rain shower which can water log a nymph's underground burrow. Majority of the nymphs remain an inch or so below the ground surface, prior to emerging.
Magicicada Emergence Holes
When the Magicicada invasion begins, the nymphs leave their underground burrows to begin their adult life. This occurs when the soil temperature reaches approximately 64 degrees Fahrenheit at an 8 inch depth.
The emergence holes decorate the ground underneath the forest canopy.
Photograph taken: 06/99
Cuyahoga County, Ohio