Figure 17.

A. The carbon dioxide concentration in air taken from Pogonomyrmex badius nest chambers of increasing depth. The concentration in the deepest chambers is about 5 times that at the surface (2 replicates). B. The distribution of nest area by decile is roughly the mirror image of the carbon dioxide concentration, suggesting that the carbon dioxide concentration gradient might serve as a template for nest excavation and worker assortment. The steepest gradient is in the top half-meter or so, and this is also the zone with the most rapid decrease in chamber area (see Fig. 9).