| MadSci Network: Zoology |
Ants, being the opportunists they are, often build nests under concrete slabs (sidewalks, building foundations, etc.) where they are protected. Their exit holes are thus often in the seams between the concrete segments. The sidewalk probably also offers a smoother "road" to feeding areas than some surfaces. However, if you look around you will find that ants will use just about any solid surface for travel, they may just be more easily seen on sidewalks! I have no good reference for this and am basing my answer on my own observations.
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