Colonies of the tiny ant, Pheidole adrianoi line the chambers of their nests with whole or fragmented black sclerotia (resting stages) of an ectomycorrhizal fungus associated with longleaf pine. Mycelia sprout abundantly from the fragments, binding the surrounding sand into stable structures. The number of whole sclerotia in nests ranged from 480 to 9400, but the accumulated fragments probably bring the total much higher. The behavior represents a large investment in foraging and fragmentation. Tests that the ants eat sclerotia or mycelia were negative, as were tests of antibiotic activity against soil bacteria and fungi. Zinc casts of nests showed them to be 25 to 70 cm deep with three to seven chambers connected by a thin, vertical shaft. Excavation and census of live nests averaged 40 cm deep, with 70 minor workers and 13 major workers. Most nests were queenless even when they contained brood, suggesting that colonies were polydomous, a condition confirmed by occasional trails between nests. Portions of the chambers of live nests served as trash piles in which broken sclerotia, former repasts and dead workers accumulated.

Abstract Many social insects construct nests, which are fundamentally important to the success and survival of the colony. We review recent work on understanding the construction and function of social insect nests and attempt to identify general principles of collective construction and nest architecture in insect societies. We look across taxa, including termites, ants, social bees, and social wasps, specifically focusing on experimental studies that have elucidated the mechanisms by which insect nests are successfully built. We find that selecting materials and nest sites are crucial decisions made by social insects that impact both the resulting nest architecture and colony survival. Social insects utilize cohesive, malleable material to build nests. Often, nests are constructed in a modular manner, allowing social insects to exploit a variety of materials while growing to accommodate population explosions from a few individuals to millions. We note that the regulatory principles that coordinate building behaviors are consistent across taxa. Specifically, encounter rate, positive and negative feedback cycles, stigmergy, and genetic influence all govern the actions of multiple builders and result in a cohesive, functional structure. We further consider empirical studies that demonstrate how nests impact collective behaviors and help insect societies flourish. We find that all social insect nests serve the same key functions: to protect residents and to offer a means of organizing their collective behaviors. Ultimately, we expand our analysis to experiments utilizing robot models of societies, which aim to uncover unifying themes of construction and space use by collectives. Overall, we show that social insect nests represent engineering and construction marvels that provide fundamental insights into how biological collectives succeed in the natural environment, and we suggest that the use of robotic models may provide insight into these fascinating behaviors and structures.