Some freshwater swamp mosquitoes overwinter as:

Freshwater swamp mosquitoes commonly overwinter in the adult stage, and this is particularly true for certain species that enter a state of dormancy. When conditions become unfavorable, such as colder temperatures or reduced food sources, these mosquitoes adapt by seeking out sheltered areas where they can survive through the winter months.

Hibernating adults can find protection in places such as leaf litter, tree holes, or other sheltered environments where they remain in a dormant state until warmer weather returns. This strategy allows them to emerge quickly when conditions become favorable again and start the reproductive cycle, contributing to the mosquito population's persistence from year to year.

Other life stages, like larvae and pupae, may not survive the complete freezing conditions typically found in winter, as they require more stable aquatic environments. Similarly, while some mosquitoes can lay eggs that will survive through winter in a state of dormancy, the question focuses on those that specifically overwinter as adults, which is why hibernating adults is the correct choice in this context.