Proc. Natl Acad. Sci. USA doi:10.1073/pnas.0902685106 (2009)

Ant colonies can build large nests with a range of architectures. But what contributes to this diversity? Etienne Toffin and his colleagues at the Free University of Brussels photographed groups of Lasius niger ants every 10 minutes for 90 hours as the insects built a nest in a thin layer of sand sandwiched between two glass plates.

The pictures revealed that nest building occurs in two stages. At first, the nest grows quickly in a circular shape. Later, it begins to branch, with buds appearing along the nest wall, some of which go on to become additional chambers. Ant group size affected nest shape; 40% of the 50-ant groups never transitioned to the second stage during the experiment, whereas only 12% of the 300-ant groups remained in the first stage.