Sketch of the experimental setup (left) and snapshot of one experiment (E66) before termites were added to the setup (right). The white marks on the picture give the scale of the setup, with the distance between successive marks being 1, 3, and 5 cm.

Top: (A) cumulative heatmaps of deposition (P (D); red) and collection activity (P (C); green) normalized by their respective mean values for one experiment (E66), colorbars are the same as in panel (E); (B) cumulative depositions (top) and collections (bottom) per unit area as a function of the Petri dish radius for experiments E58, E63, E65, E66, and E76, all histograms have been normalized and sum up to 1; (C) comparison among experimental depositions (in red), surface curvature (in blue) shown in Fig. 3C, and depositions predicted by simulations (black) shown in Fig. 3C, all the quantities are computed along the radial cut shown in panel (A), depositions are normalized by their maximum value and curvature is in mm−1; (D) cumulative occupancy heatmap normalized by its mean value for E66; (E) depositions (P (D|O); red) and collections (P (C|O); green) conditional to cumulative normalized occupancy for E66.

Top row: snapshots of a building experiment with “pillars” cue (E66) (A) and a building experiment with “wall” cue (E78, in B). Bottom row: snapshots of 3D simulations initiated with copies of the experimental setup E66 (C,D) and E78 (E,F) in which nest growth is entirely determined by the local surface curvature (based on our previously described model (Facchini et al., 2020)). Snapshots C and E refer to t=0, D and F refer to t=9 (dimensionless). The color map corresponds to the value of the mean curvature at the interface air-nest. White indicates convex regions and black indicates concave regions. The scale bars correspond to 1 cm.

Top row: contour of the humidity gradient ∇h obtained solving the Laplace equation Δh = 0 in a cubic domain with a humid bottom boundary h = 100% (in brown) which is mapped from 3D scans of the experimental setup in E66 (A) and E78 (B). At the top boundary h is fixed to h = 70% which was the average value of humidity in our experimental room. Note that h is the relative humidity, thus the magnitude of the humidity gradient |∇h| is measured in mm−1, i.e |∇h| = 0.1 mm−1 means a humidity variation of 10% over 1 mm. Each contour corresponds to a variation of 0.015 mm−1. Pillar tips are associated with a strong humidity gradient; the top of the wall is also associated with a strong humidity gradient, although not as strong as at the pillar tips. Also note that humidity gradient at the top corners of the wall is 30% stronger than on the rest of the top edge. Bottom row: snapshots of chemical garden experiments initiated with “pillars” cue (C), and with “wall” cue (D). All the scale bars correspond to 1 cm.