Three simple rules for building a tower, if you are a fire ant

Ig Nobel Prize winner David Hu and colleagues explain the simple rules that fire ants use when they build a tower-of-fire-ants. They explain in a new study:

Fire Ants Perpetually Rebuild Sinking Towers,” Sulisay Phonekeo, Nathan Mlot, Daria Monaenkova, David L. Hu, Craig Tovey,” Royal Society Open Science, vol. 4, 2017, 170475.

In the aftermath of a flood, fire ants, Solenopsis invicta, cluster into temporary encampments. The encampments can contain hundreds of thousands of ants and reach over 30 ants high. How do ants build such tall structures without being crushed? … Here, we present models of the shape of the tower and its rate of growth. In our past work on raft construction, we found ants followed three rules, which yielded accurate predictions for raft growth rate. These rules are as follows:

1. Do not move if ants are on top of you.

2. If atop other ants, repeatedly move a short distance in a random direction.

3. Upon reaching available space adjacent to non-moving ants, stop and link with them.

4. The top layer of the tower is not stable unless there is a complete innermost ring of ants gripping each other around the rod.

We include the fourth rule based on our observations.

Here’s further detail from the study:

Sarah Zielinski has an especially nice writeup of this writeup, in Science News, with added video.

The 2015 Ig Nobel Prize for physics was awarded to Patricia Yang, David Hu, and Jonathan Pham, Jerome Choo, for testing the biological principle that nearly all mammals empty their bladders in about 21 seconds (plus or minus 13 seconds). They describe that research, in the study “Duration of Urination Does Not Change With Body Size,” Patricia J. Yang, Jonathan Pham, Jerome Choo, and David L. Hu, Proceedings of the National Academy of Sciences, vol. 111 no. 33, August 19, 2014, pp. 11932–11937.