In 'Dune', what is the name of the sandworm's larval stage?

In 'Dune', the sandworm's larval stage is called a sandtrout.

Sandtrout are small, leathery creatures that form the earliest known stage of the sandworm life cycle on Arrakis. The Fremen also call them “Little Makers.” They are adapted to detect and contain water, a remarkable trait on a desert planet where exposed moisture is dangerous to the sandworm ecosystem. Sandtrout gather around underground water sources and create living barriers that trap water beneath the surface.

Their role connects Arrakis's ecology to the production of spice. When water disrupts the sandtrout colonies and underground chemical processes, a pre-spice mass forms. Pressure eventually drives that material toward the surface, where exposure to air and sunlight helps produce melange, the spice central to the Imperium's economy and space travel. Shai-Hulud is the Fremen name for an adult sandworm, while “Maker” is another name for the mature creature. Sandtrout are therefore not adult worms, but a distinct juvenile or larval phase in the cycle described in Frank Herbert's novels.