Which transformation stage is characterized by a significant change from a larva to an adult mosquito?

The pupa stage is critical in the life cycle of a mosquito, as it represents a significant transformation from the larval form to the adult mosquito. During this stage, the mosquito undergoes extensive morphological changes. Unlike the larval stage, which focuses on feeding and growth, the pupa is a non-feeding stage where the mosquito prepares for emergence as an adult.

In the pupa stage, the larva undergoes metamorphosis, during which the tissues and organs of the larva are reorganized and developed into the structures of the adult form, such as wings and reproductive organs. This transition makes the pupa stage vital for the completion of the mosquito's life cycle.

The egg stage involves the initial reproductive phase where eggs are laid but does not feature the dramatic physical changes seen in the pupa. The larva stage, while important for growth, is more about feeding than transformation. The nymph stage is not applicable to mosquitoes, as it pertains to the life cycles of other insects, such as certain aquatic insects, that do not have a pupal stage. Hence, the pupa stage is correctly identified as the stage marked by the significant change leading to the emergence of the adult mosquito.