Bees and the pollination partnership

Bees descend from hunting wasps, probably crabronid wasps, that fed their young with captured insects. At some point in the Early Cretaceous, a lineage began to feed larvae pollen and nectar instead, and bees (Anthophila) were born. Molecular dating places the origin at about 120 million years ago, soon after flowering plants spread. The oldest fossils are in Burmese amber about 100 million years old, such as Melittosphex burmensis, whose branched body hairs resemble the pollen-catching hairs of bees, though whether it was a true bee is disputed.

The partnership benefited both sides. Flowers offered nectar and pollen, bees carried pollen from plant to plant, and plants that were visited by bees reproduced more successfully. Bees developed hairy bodies and pollen-carrying baskets or brushes on their legs, and flowers developed colors, scents and shapes that guide bees. Today there are over 20,000 species of bees, and they pollinate a large share of the crops that humans eat. The stingless bee Cretotrigona, from Late Cretaceous New Jersey amber, shows that bees were already diverse before the end of the era.