These new reproductive individuals fly out and mate. The bees in the old hive die with the coming of winter, but the fertilized young queens hibernate and found their own nests the next spring. Because bumblebees have division of labor correlated with sterile castes, they are said to be eusocial (i.e., truly social), but their colonies, which must be founded anew each year because they cannot survive the winter, are by no means as complex as those of honeybees.