In social wasp colonies there are usually three castes: the egg-laying queens (one or more per colony), the workers, or sexually undeveloped females, and the drones, or males. Social wasps build nests of a coarse, papery material, prepared by masticating wood fiber. The eggs are deposited in the compartments, or cells, of the nest, where they develop into larvae and then pupae, emerging as adults. Adult social wasps feed chiefly on nectar and plant sap but feed the larvae with masticated animal food. In temperate regions a colony lasts a single season, the drones and workers dying in the fall. The mated queens take shelter during the winter and in spring lay eggs and start new colonies. In the tropics colonies continue indefinitely, dividing when they grow very large. The paper wasps ( Polistes ), of nearly worldwide distribution, usually hang their nests, consisting of a single comb (layer of cells), from eaves, branches, or other shelters. The hornets and yellow jackets ( Vespa ), found throughout the Northern Hemisphere, build a large, round nest of many combs, covered with a paper sheath; in some species this nest is built underground.