Table 1.

Mean (±s.d.) values of S. invicta tunnel network structure, topology and activity among three treatments composed of groups of small, large and control workers after 72 h of digging. Area is the total excavated area. Length is the total length of tunnels and width is the mean tunnel width. The probability distribution function of the tunnel widths was fitted by a lognormal function, where w is the local tunnel width and μ and σ are fit parameters. The tunnel network consisted of edges representing tunnels and vertices representing tunnel junctions. A connected component is a self-contained network in which all vertices are accessible from the other. The number of surface entrances and connected components did not differ among treatments. N12h is the number of subsurface ants at 12 h and 〈N〉 is the average number of subsurface diggers over the duration of the test.

treatmentsmalllargecontrol
replicates232424
spatialarea (cm2)34.03 ± 14.7529.99 ± 13.7239.18 ± 13.84
length (cm)159.17 ± 61.73119.17 ± 51.07186.04 ± 70.28
width (cm)0.22 ± 0.040.26 ± 0.070.22 ± 0.05
μ (lognormal fit parameters)−1.35 ± 0.05−1.07 ± 0.03−1.27 ± 0.05
σ (lognormal fit parameters)0.40 ± 0.060.37 ± 0.020.38 ± 0.04
mode[P(width)] (cm)0.220.30.24
network vertices50.70 ± 34.5425.65 ± 19.2061.44 ± 39.76
edges49.78 ± 31.0327.83 ± 17.6158.72 ± 34.98
connected components5.13 ± 3.404.70 ± 2.655.24 ± 3.72
surface entrances7.13 ± 4.325.91 ± 3.307.56 ± 4.55
activityN12h5.00 ± 4.724.52 ± 3.389.76 ± 7.30
N8.46 ± 6.497.01 ± 4.5910.96 ± 6.74