n. a social structure among nonhuman animals in which there is a marked division of labor, with only a few individuals that reproduce and many more nonreproductive individuals that guard the nest, gather food and nest materials, or help to care for the young. Eusociality is a common form of social structure in colonial species of bees and wasps (see social insects): The haplodiploidy mode of inheritance helps to explain the adaptiveness of nonreproductive helpers caring for the young of the queen. —eusocialadj.