The life cycle of Bumble bees is different from that of honey bees and also differs slightly depending on the species. Most bumble bee species are social insects and create colonies with a single queen. However, their colonies are much smaller than honey bee colonies. They can be as small as 50 individual bees but rarely exceed more than 500 bees.
The Cuckoo bumblebee (Bombus Bohemicus), a member of the subgenus Psithyrus in the bumblebee genus Bombus of the Apidae family is an exception. Cuckoo bumble bees are parasitic. This means they do not build nests or form colonies of its own. Instead, the queen searches for nests of other bumblebee species and takes over killing the resident queen. She then lays her own eggs and the workers of the invaded colony care for the brood.
Bumble bees typically do not hibernate during the winter months. They migrate within colonies or form clusters in sheltered environments. When conditions become too harsh for survival, some species enter a state of dormancy similar to hibernation until they appear again when more favorable conditions return. This is known as “diapause“.
Making a nest
The life cycle of the bumble bee starts with a single queen. In the springtime, from around March onwards, bumblebee queens emerge from their subterranean winter abode to establish their new home. However, some species may appear as early as February. First, they need to replenish themselves. They do this by visiting flowers for nectar and pollen. Once they found a suitable nesting site, they start to collect bits of dead vegetation to form a base layer, which they shape into a nest. They keep collecting more material from the surrounding environment, including bits of grass, moss, leaves and hair to add to her nest. Queens are incredibly industrious and can create an impressive nest with just her mandibles!
As soon as the nest is finished, the queen starts building wax cells where she lays her eggs. Interestingly, bumblebees have a unique ability to generate heat through their flight muscles. The bumble bee queens utilize this special talent to incubate their brood to hasten its development. Like honey bee queens, they can decide to lay fertilized or unfertilized eggs. Unfertilized eggs become haploid males, and fertilized eggs grow into diploid females and queens.
The eggs hatch after 4 days. They start out as small maggot-like creatures, and quickly begin to feed and grow. The larvae go through a series of development stages, in which they shed their skin three times. After approximately 14 days the pupae they metamorphise into a fully developed young bumble bee, chewing their way out of the cocoon to begin their new life. The entire cycle from egg to adult bumble bee typically takes around four weeks.
Bumble Bee Workers
The first brood of the life cycle develops into female worker bees that takes over from the queen attending and feeding the young. Like honeybee workers, they also perform other duties like foraging and cleaning. To feed the next brood, they regurgitate the nectar into small holes that they make in the brood cells. They also provide the brood with pollen. This is done either by creating pockets at the base of the brood cells from which they can feed themselves, or by storing it in wax pots and feeding it to them directly.
Once the first wave of workers has matured and left the colony, the empty cocoons are utilized as short-term storage containers for nectar. Bumblebees do not produce nor store honey in large quantities like honeybees.
By summer, there are usually many bees in a colony. Throughout the summer season, the queen produces one generation of worker bees after another. After the first or second batch of offspring emerges, the team of workers take over the responsibility from the queen to collect and gather food. This allows the queen to focus on laying eggs and nurturing larvae.
Male Bumble Bees
As the colony grows bigger and more populous, the queen starts to produce male bees (drones) and new queens. Drones will leave the nest in search for chance to mate as soon as they emerge. Bumble bee males have been observed exhibiting polygynous behavior, mating multiple times with different female partners. This is in stark contrast to honey bee males, who typically mate with only one single female. This difference in mating behavior is likely due to the different reproductive strategies of the two species.
Unlike many other species of bees, bumblebees do not form swarms. Instead, they form what is known as a ‘drone cloud’ – a large group of males flying around a nest in search of a mate. These clouds are often the most visible part of a bumblebee colony.
Once the young bumble bee queens emerge, they sometimes stay at the nest for a while to build fat reserves, which help them prepare for the diapause. In temperate zones, young queens (gynes) leave the nest in the autumn months to mate. Like honeybees, they often mate multiple times. The fertilized queen will remain in a state of diapause below ground until spring when she will emerge and the cycle starts again.
Unlike honeybee colonies that can survive the winter, only the new bumble bee queens survive. All other members of the colony will have perished by late autumn. So when spring time arrives, the cycle starts again.
Bumblebees play an important role in our environment; they help pollinate plants to help make sure that food crops are successful. They also work hard to make sure that flowers remain thriving and colorful, adding beauty to many landscapes. In addition, bumblebees are beneficial predators which help to control pests in gardens and fields alike. Without these invaluable pollinators, our planet would be a much less diverse place!