With about fifty species in North America it is hard to generalize. However most bumble bees are colonial; there is a queen and workers living together in a hive, with the queen being the mother of all the workers. The colonies can vary in number from no more than a couple of dozens to a few hundreds.
Early in the spring the adult queen that was born and mated the previous season emerges from its wintering place, hidden under bark or in some other safe place. It starts looking for the right place to raise its family. This can be a rodent’s burrow or a similar hole. In some cases just a tussock of grass will do. Once she finds a satisfactory locale she starts redecorating her property, making it more suitable for her babies.
She builds some wax containers, which she fills with food, nectar and pollen and she builds a larger mass or brooding cell, made of a mixture of wax, pollen, nectar and her own saliva. This is where she lays a batch of eggs. For the next two weeks or so, she takes care of this brood by adding more food as needed and by keeping it warm during the night or colder weather. She does this, as brooding birds do, by lying on top of the egg mass. Her belly has even a hairless patch, just like such birds, which helps to transfer the heat from her body to the brooding cell where the growing larvae are.
The larvae grow rapidly on that nutritious mixture and soon a half dozen or a dozen adults emerge from this brood. They are smaller than the queen and they are all worker females. They set to work right away taking care of housekeeping and going out for more nectar and pollen. Now the queen doesn’t need to go out and hardly does so from then on. She simply stays home laying more eggs and being attended by the workers.
The colony keeps growing and by the fall the queen lays eggs which will become the future queens and also lays some male eggs.
When the new queens emerge, they don’t do any work in the colony. They just go out and mate with males, possibly from another colony. After that they start looking for a safe place where to spend the winter. The old queen, all the workers and the males die shortly afterward.