The ant tower

When fire ants, Solenopsis invicta, need to build temporary shelters due to natural events such as flooding of their nest, they can work together to build temporary shelters call bivouacs using their bodies while they build their more permanent subterranean nest.

Below is an example of a bivouac.

They are able to build these structures without a central leader and the towers they build allow each ant to bear a low amount of weight (only ~3 ant weight).

Below are some videos of the ant tower experiments. Feel free to download but please credit David L. Hu of Georgia Institute of Technology.

SI 1 Ant tower complition.mp4

Time-lapse video of ants building around a low friction central support of varying sizes.

SI 2 Tower_close_up.mp4

Close up view of the tower building process. From disorder, these ants are able to build a stable structure. Video is in real time.

SI 3 buckling.mp4

However, they need to build complete rings around the central support. Otherwise, buckling of of partial towers can occur. Video is in real time.

SI 4 xray_125x.mp4

In order to see what happens on the inside. We fed ants x-ray contrast medium and film the tower through an x-ray machine. We see that the tower is in a constant state of sinking and reconstructing. Video is sped up 128 times.

SI 5 tunnel_128x.mp4

We also filmed underneath a finished tower. We can see from the highlighted regions that these fire ants also form tunnels inside the tower.