What is the term for the immature form of an insect that hatches from an egg and is different from its adult form?

The term for the immature form of an insect that hatches from an egg and significantly differs from its adult form is indeed referred to as larva. In many insect species, the larval stage is characterized by a distinct morphology and behavior that are quite different from those of the adult. For example, caterpillars are larvae of moths and butterflies, and they often have different feeding habits and ecological roles compared to the adults.

Insects undergo a process known as complete metamorphosis, which includes four life stages: egg, larva, pupa, and adult. During the larval stage, the primary focus is on growth, and these immature forms typically consume large amounts of food to store energy for development. This growth culminates in the pupal stage, where the insect undergoes transformation into its adult form.

Other options represent different stages or forms in the life cycle of insects but do not specifically describe the initial immature phase. The pupa is a transitional stage between the larva and the adult, while nymphs are immature forms of insects that undergo incomplete metamorphosis, appearing more like small adults and lacking a distinct larval stage. Finally, the adult stage is the fully developed form of the insect.