The bumblebee life-cycle differs from that of honeybees.
Our hives contain the large earth bumblebee, Bombus terrestris. Bumblebees are members of the same family of bees as honeybees, the Apidae. Neither honeybees or bumblebees are native to New Zealand. Bumblebee species were introduced from the United Kingdom for the pollination of red clover at the turn of the 20th century, with four species becoming established. Prior to that, all clover seed had to be imported from the UK at large cost, as New Zealand had no native species that would readily pollinate clover flowers. It was the first instance of a species imported solely for its pollination services! Much later, year round bumblebee rearing techniques were developed, primarily for the pollination of large scale greenhouse tomato crops, and bumblebees have been commercially reared in New Zealand for this purpose since the early 1990's.
Bumblebees produces a nest, rather than a true hive, but we will refer to them as hives for the sake of convenience. A honeybee hive in the wild can survive for many years, while a bumblebee hive is an annual event, with only young and freshly mated queens surviving through the winter in their native distribution. In New Zealand, the warm conditions mean that some hives will often continue for longer periods, but the queen stops laying eggs after the hive produces reproductives (new gynes and males), and the existing hive is never revived by another queen. As the bumblebee hive does not overwinter, there is no need for the storage of large quantities of honey, so bumblebees do not produce quantities that can be commercially used by humans.
Bumblebees develop their hive from a single mated queen, unlike honeybees, who start new colonies with a swarm of worker bees and a queen. In spring, a young mated bumblebee queen emerges from an overwintering hole, where she has been hibernating. She will spend some time searching around for a suitable site to establish her new hive. In the wild this might be an abandoned rodent hole, or a dense low shrub. Once she has found the hive site, inside it she builds a small honey pot out of wax, which she exudes from between segments of her abdomen. She visits flowers to collects nectar to fill the honey pot, and collects pollen to make small balls (mixed with nectar) as a food store for her young.
She lays a group of fertilised eggs on the pollen balls, which she will brood over to keep warm, much like a bird would. The underside of her thorax is hairless, which enables her to efficiently transmit body heat to the young. She maintains the hive’s heat at around 30˚C. During this time she still makes short trips outside to continue to collect pollen and nectar. Once the eggs have hatched the larvae eat the pollen balls provided. Pollen is high in protein, which is necessary for the larvae to grow and develop. After a period the larvae stop feeding and pupate. Approximately 2 weeks later, the adult worker emerges.
After a few days workers take over the brooding and eventually the foraging duties from the queen, who focuses on laying more worker eggs. She will stay within the hive from now on. The hive continues to develop, and can vary in size from 80 to 400 individuals at its peak. Initial workers are small, but future adults will increase in size as the hive becomes stronger and more resources can be devoted to their development.
At some point the hive will start generating gynes (unmated queens), who, after mating, will become the following year’s queens. The gynes, like the workers, are born from a fertilised egg. It is thought that the queen prevents the early production of gynes by releasing a pheromone, which she subsequently stops. Gynes are feed more during the larval stage to assist their development and give them their increased size. At roughly the same time the queen and possibly some dominant workers will lay unfertilised eggs, which will develop into smaller males. Bumblebees have a haplodiploid sex-determination, simply put, the queens, gynes, and workers have 2 sets of chromosomes (from the egg and sperm), while the males have just a single set (egg only). This means that no male bumblebee has a father, or can ever have sons, but they do have a grandfather, and can have grandsons!
Males do not collect pollen for the hive, and quickly leave to find a gyne to mate with. Gynes will also leave the hive to mate, but will return to build up fat reserves necessary to survive the winter. Finally, the young queens leave the hive to find suitable over-wintering holes, and the cycle begins again the coming spring.
Our rearing process closely matches the normal life-cycle of the bumblebee, however, by providing them with favourable weather and nutrient conditions, we are able to produce hives on a year round basis. This enables us to provide hives any week of the year, which is especially important to the glasshouse industry, and means the consumer gets great quality fruits and vegetables in the middle of winter!