Why do antlions throw sand at prey trying to escape a pit?

Antlion larvae dig funnel-shaped pits in dry, sandy soil to trap small insects. When prey falls into the pit and attempts to escape by climbing the loose, unstable walls, the antlion uses its head to vigorously toss soil at the insect. This action causes the prey to lose its footing and fall back into the bottom of the pit, where the larva is waiting to seize it with its powerful, sickle-like jaws.123