In which type of metamorphosis do insects show major changes during the pupal stage?

The correct choice is complete metamorphosis, which is characterized by four distinct life stages: egg, larva, pupa, and adult. During the pupal stage, significant structural changes occur as the insect transitions from the larval to the adult form. This includes the reorganization of tissues and the development of new structures such as wings and reproductive organs, which are not present in the larval stage. The pupal stage acts as a transformative period where the insect undergoes a remarkable reconfiguration, leading to the emergence of a completely different adult form.

In contrast, other types of metamorphosis, such as incomplete metamorphosis or gradual metamorphosis, involve only minor changes between life stages and do not feature a distinct pupal stage with substantial transformation. In these cases, the young insects (nymphs or larva) usually resemble smaller versions of the adults and undergo several molts without the dramatic reorganization seen in complete metamorphosis. Dimorphic metamorphosis is also not a recognized term in entomological classification and does not refer to a specific process in insect development. Thus, the emphasis on significant changes during the pupal stage distinctly identifies complete metamorphosis as the correct answer.