I have examined the coarse sand like grains on the top of the ant hill. They are somehow modified and don't mix with normal soil or disintegrate in water.The region I live in has red soil.
A quick search on ant hills brings up information from here
The ant hill is a byproduct of ants building their colony. As ants dig their long and winding tunnels beneath the ground, the excess dirt and debris is carried out and placed near the colony entrance, creating the ant hill. At the top of the hill, there will be a small hole that serves as the entrance and exit to the colony. Typically, an ant hill will be made from a combination of dirt, small rocks, pine needles, and whatever other materials were left over after the ants have dug their colony.
Other sites also state same facts on the composition of ant hills, but nowhere I can find any secretion or something which changes the properties of the ant hill soil.
- So do they secrete enzymes or something or mix the soil with plant debris to change the size of grains?
- Does doing this confer some added protection to the ant colony living underground ?