Reproductive cycle
Most bumblebees form colonies annually. In late summer or autumn, fertilized young queens overwinter and emerge in spring. Then, they form a new colony.
When the queen emerges looking for a place to nest (which varies in each species). After that, queen builds two bowls, usually coated with wax. A bowl full of pollen, in which lays eggs. In another bowl, reserves of honey serve as food for the larvae. Shortly after (one week in Bombus pascuorum), the larvae begin to weave a cocoon around. After pupation, Queen reuse the wax.
About a month after commissioning, the first workers will hatch. The workers are responsible for the care of laying and the queen is dedicated only to lay eggs. Gradually, the colony is increased.
For example,
A few species of the genus Bombus are thought to be bumblebees parasites. Bumblebees parasites have no laborers, but they have males and females. After overwintering, one fertilized female invade the nest of another species and destroys part or all of the eggs. Then, female puts her own eggs and goes. The workers of the host species take charge of the care and feeding eggs.