A group of bees is most commonly called a "swarm." According to the Northern Prairie Wildlife Research Center, a swarm is also known as a "hive" or a "grist of bees." Swarms assemble in a colony, numbering as high as 35,000 bees in the summer.
There are three types of bees in a hive, living in the colony. It's a highly ordered society, centered around the needs of a single queen. In the colony, thousands of female worker bees accompany hundreds of male drones. By autumn, a grist of bees is almost entirely female, as the drones are evicted from the colony. Swarm numbers dwindle to as few as 5,000 bees as female workers die off, and the queen becomes less productive. Swarms are short-lived. A female worker bee lives about 40 days, and drones live 56 days.