Antlion sand interaction: A study of repose angle

The antlions dig a conical simple pit in sand to catch ants. The funnel shape of the trap is deliberate with a critical angle of repose and is steep and shallow enough to trigger avalanches and cause struggling prey to fall into the funnel. The trap should be designed by optimizing pit morphology according to natural selection. In the current study, antlion behavior and pit morphology in the sand samples with different particle shapes and particle size distributions were studied. The small larvae build in fine sand and silty sand, while larger ones prefer fine to medium sands. However, there is no preference for sands with different particle shapes. Further, the static and dynamic angles of repose for the sand samples were measured, and the slope of the pits was compared with the repose angles. The angle of the heap slope oscillated between an upper angle or angle of sliding (the angle that triggers a landslide) and a lower angle named repose angle.