Carton nests are created by ants as they transform large cavities in the soil and tree trunks by filling them with carton nests, whose internal structure is partitioned and resembles a sponge; a cardboard-like substance consisting of chewed plant material often mixed with soil, made by certain insects for building nests.

The ant carton consists of particles of wood, dry vegetable material, and soil glued together with sugary secretions collected by the ants from aphids and other homopteran insects (bugs that pierce plant tissues and suck out the sap).

The fungal mycelium (loose network of delicate filaments hyphae or threadlike filaments that form the body of a fungus) grows through the walls of the carton which are strengthened by the symbiotic fungus which reinforces them in the same way that steel mesh or rods reinforce the walls of buildings.