From ScienceDaily:
The nest of black garden ants, Lasius niger, consists of an underground part made up of a network of galleries, and a mound of earth composed of a large number of bubble-shaped chambers closely interconnected with each other. Using 3D imaging techniques such as X-ray tomography[2] and a 3D scanner, the researchers characterized the 3D structures made by the ants as well as the construction dynamics. In addition, they analyzed the individual building behavior of the ants.
In the part located above ground, the insects pile up their building materials forming pillars that encircle the chambers. The ants preferentially deposit their soil pellets in areas where other clusters of pellets have already been created. They add a pheromone to their material, which stimulates the other ants to build on the same spot, leading to the formation of regularly spaced pillars. When the columns reach a height equal to the average body-length of an ant, the workers build caps on top of the pillars. They use their body size as a template to determine when they should stop building vertically and begin to deposit pellets laterally. The ants thus use two types of indirect interactions in order to build complex architectures.
In addition, the pheromone breaks down over time at a rate that depends on climate conditions, which enables construction to adapt to the environment. More.
Amazing how all the live ants all just happen to do all this, and meanwhile the water remains water and the sand remains sand.
See also: Does intelligence depend on a specific type of brain? No.
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Here’s the abstract:
The nests of social insects are not only impressive because of their sheer complexity but also because they are built from individuals whose work is not centrally coordinated. A key question is how groups of insects coordinate their building actions. Here, we use a combination of experimental and modeling approaches to investigate nest construction in the ant Lasius niger. We quantify the construction dynamics and the 3D structures built by ants. Then, we characterize individual behaviors and the interactions of ants with the structures they build. We show that two main interactions are involved in the coordination of building actions: (i) a stigmergic-based interaction that controls the amplification of depositions at some locations and is attributable to a pheromone added by ants to the building material; and (ii) a template-based interaction in which ants use their body size as a cue to control the height at which they start to build a roof from existing pillars. We then develop a 3D stochastic model based on these individual behaviors to analyze the effect of pheromone presence and strength on construction dynamics. We show that the model can quantitatively reproduce key features of construction dynamics, including a large-scale pattern of regularly spaced pillars, the formation and merging of caps over the pillars, and the remodeling of built structures. Finally, our model suggests that the lifetime of the pheromone is a highly influential parameter that controls the growth and form of nest architecture. (Public access) – Anaïs Khuong, Jacques Gautrais, Andrea Perna, Chaker Sbaï, Maud Combe, Pascale Kuntz, Christian Jost & Guy Theraulaz. Stigmergic construction and topochemical information shape ant nest architecture. PNAS, 18 January 2016 DOI: 10.1073/pnas.1509829113