Nest structure engineering of the leaf-cutting ant, Acromyrmex landolti, in the semiarid Caatinga biome

Nest architecture is a key factor in the development of ant colonies. Species-specific constructed nests can be simple such as surface-level nests or elaborate such as subterranean or arboreal nests. Subterranean nests are more difficult to study and their internal structure is little known. This study was carried out with the objective of studying the structure of leaf-cutting ant nests in an extreme environment. For such, seven nests of Acromyrmex landolti were excavated in a semiarid region of the Caatinga, an exclusively Brazilian biome. The nests were measured both externally and internally and then photographed. Nests were found in open and sunny areas and externally all nests presented a loose soil mound, straw protection over the entrance hole, and a refuse dump. The number of underground chambers found ranged from 4 to 17, with differing heights, widths, and lengths. The chambers were found from near the surface of the ground to a maximum depth of 1.70 m. Our results showed that strategies used by A. landolti include the construction of an ornate straw tower at the entrance of the nest and the construction of deep underground rooms, with the chambers of fungi near the water table. The structure of the nests of A. landolti is probably related to its habit of building their nests in open, sunny locations associated with environmental factors characteristic of the semiarid climate of the Caatinga biome.