Final answer:
The legless, immature feeding stage in complete metamorphosis is known as the larva. In insects, this is exemplified by the caterpillar stage of butterflies, which eventually transforms into the pupa stage before becoming an adult butterfly.
Step-by-step explanation:
The legless, immature feeding stage you are asking about is characteristic of animals that undergo complete metamorphosis. In this process, the immature form is called a larva, which looks very different from the adult form. For example, a butterfly's life cycle starts with an egg, which then hatches into a caterpillar (larva). The caterpillar is the feeding stage where it eats and grows before entering the pupa stage. In the pupa stage, it does not eat or move, and it undergoes a transformation, reorganizing its tissues into the adult form.
Famously, the caterpillar metamorphoses inside the pupa to emerge as a butterfly. Many insects, like beetles, ants, flies, and butterflies, develop through this process from larvae. Amphibians, like frogs, also go through metamorphosis where the tadpole (larva) stage involves a significant transformation to become a land-dwelling frog with legs and lungs instead of gills and a tail.