What term refers to the different immature stages of an insect?

The term that refers to the different immature stages of an insect is "instars." This terminology is specific to the developmental phases that insects undergo as they grow, particularly in those that undergo metamorphosis. Each instar represents a distinct stage between molts, where the insect sheds its exoskeleton to grow in size.

For insects that experience complete metamorphosis, there will typically be multiple instars before the final stages of pupation and adulthood. In contrast, terms like larvae and pupae refer to specific stages within the life cycle but do not encompass the entire range of immature stages. Eggs are the initial stage of development and do not represent the active developmental phases of the insect post-hatching. Thus, "instars" is the most precise term for describing the various stages of immaturity in an insect's life cycle.