Over two days a mud dauber wasp (Sceliphron spirifex) built and stocked a nest on our dining room wall.


What I found so interesting was that as the wasp added a dollop of mud to the structure, it vibrated its wings. Vibrate – stop – vibrate – stop. What was that all about?

Does it have something to do with the fact that mud can be a thixotrophic substance? Solid at rest, but when disturbed it becomes liquid? Perhaps by vibrating the mud, the wasp was able to shape it, but when it stopped vibrating, the mud set instantly and kept its shape. I’m just guessing.

Thixotrophy can also cause landslides during earthquakes: solid wet soil suddenly turns liquid from being shaken up.

Reading up on this I discovered there is a whole range of substance that show ‘non-Newtonian’ qualities, and a different name for each: rheopecty, pseudoplastic, dilatant.

A really fun example of a dilatant substance (solid when agitated, liquid otherwise) is ‘magic mud’ or ‘oobleck‘, a cornflour-water mixture. Have fun!