Encyclopedia of Entomology

Bees essentially are wasps that turned to pollen for dietary protein. A combination of distinctive features, taken together, make bees unique among insects. (i) Sociality, characterized by overlapping generations, cooperative brood care and a reproductive division of labor between fertile queens and sterile female workers, has evolved multiple times within the bee lineage. Presumptive intermediate stages of sociality are represented by at least several living species, and thus are available for observation, evolutionary study, and experimental manipulation. (ii) Bees, unlike most other herbivorous insects, dine solely on pollen and nectar or floral oils. This dietary transition from their carnivorous ancestors was accompanied by the evolution of branched body hairs which aid bees in picking up pollen, plus modification of the hind legs or ventral abdominal surface for carrying large loads of pollen. These features typically distinguish bees from wasps. (iii) Unlike most insects, each adult female of every nonparasitic bee species, whether social or not, rears her young in a nest. Thus, all food and shelter needs of bee larvae are provided by their mother, or one or more sisters if the species is social, or the host female if the species is parasitic. (iv) From the central nest, females daily venture forth repeatedly on spatially extensive foraging trips to acquire floral resources for their brood. These trips require remarkable navigational skills equaled by few other insect taxa. (v) As a consequence of their extensive foraging at flowers, bees have become the primary biotic agents of pollination for continental floras worldwide. No other animal group so dominates this, or the other great plant-animal mutualism, seed dispersal.