How do antlion larvae build cone-shaped pits in sand?

Antlion larvae, which belong to the order Neuroptera, construct their characteristic funnel-shaped pits in dry, sandy soil using a precise, repetitive process.1

The larva utilizes its oval-shaped abdomen as a plow to loosen the sand. It then heaps these particles onto its large, square head and flicks them clear of the pit's perimeter. This action is repeated until a symmetrical, funnel-shaped trap is formed, typically measuring 2.5 to 5 cm deep and 2.5 to 7.5 cm wide at the edge.1

Once the pit is complete, the larva buries itself at the bottom, leaving only its powerful, sickle-like jaws exposed. When a small insect wanders over the edge, the loose sand causes it to slide to the bottom, where it is seized by the larva. Not all species engage in this behavior; some, such as Dendroleon obsoletus, hunt by waiting in hiding places rather than building pits.21