It is the second , third and fourth generations that return to their northern locations in the United States and Canada in the spring .
The generation that overwinters generally does not reproduce until it leaves the overwintering site sometime in February and March .
generation is the second , third and fourth generations that return to their northern locations in the United States and Canada in the spring .
The generation that overwinters generally does not reproduce until it leaves the overwintering site sometime in February and March .