What term describes the phase in which insect larvae develop into adults?

Metamorphosis is the term that specifically describes the process by which insect larvae transform into their adult forms. This process encompasses the significant physical changes that occur within the organism. Insects that undergo metamorphosis typically progress through distinct stages, such as egg, larva, pupa, and finally, adult. Each stage is characterized by unique physiological and morphological changes.

Emergence refers to the act of an adult insect leaving its pupal case, which may occur after the metamorphosis process is complete, but it does not encompass the entire transformation. Hatching involves the breaking of an egg and is relevant to the early stages of an insect's life cycle, while development is a more general term that refers to the overall growth and changes an organism undergoes throughout its life cycle. Thus, metamorphosis specifically captures the transition from larva to adult, making it the correct term in this context.