Final answer:
Monarch butterflies immigrate to the United States in the spring to breed.
Step-by-step explanation:
Monarch butterflies overwinter in Mexico and fly to the southern United States in the spring to breed. They are not hibernating in the United States, but rather they are immigrating to the United States for breeding. This migration is a natural behavior for monarch butterflies, and it allows them to take advantage of the warmer climate and availability of resources in the southern United States during the breeding season.
Learn more about Monarch butterfly migration