Escaping the Antlion’s Trap: Pressure Dependent Friction on Granular Surfaces

Synopsis

An antlion creates a trap in the form of an inverted cone in sand close to the avalanche angle. An ant which enters the trap is, most of the time, unable to escape whereas a heavier insect finds it easier to escape. In order to understand this problem a recent paper [1] studied the sliding of objects on an inclined granular surface close to the avalanche threshold. Heavy objects creates deformations which stabilise the object on the surface whereas light objects hardly disturb the surface and thus are also stable. For objects of intermediate weights the deformations are such that they generate sliding of the objects on the slope. The result of the experiments is a stability diagram and a proposed link between the diagram and the inability of some insects to escape the antlion trap.

References
[1] J. Crassous, A. Humeau, S. Boury and J. Casas, PRL 119, 058003 (2017).