Bumble Bee Lifecycle - Page 2
When a queen secures a nesting site, she prepares it for her immature offspring called "brood." Near the entrance tunnel, the queen forms a honey pot. The honey pot is made of wax produced glands under the exoskeleton of the queen's abdomen. The honey pot is filled with a store of regurgitated honey that will enable the queen to survive during periods of bad weather when foraging is unfavorable.
Once the honey pot is constructed, queens begin to further prepare the nest by working the pre-existing insulating material into a snug insulation cavity the size of a tennis ball. The queen may reinforce the insulation cavity by plastering regurgitated nectar on the cavity walls. Inside this insulation cavity, the queen will form a pollen lump by moistening pollen collected from flowers with honey and working it into a ball. The queen will lay 5-12 white sausage shaped eggs inside the pollen lump and immediately cover the brood clump with a coat of wax. This wax covering is believed to help prevent the pollen from drying out. The pollen lump is made in close proximity to the honey pot so that the queen can feed on honey while incubating her brood. Queens incubate the brood clump by sitting on the eggs, and transferring heat through her abdomen onto the brood. Eggs must be kept near 30C, and will hatch after 5 days. The milky white larvae that emerge from these eggs have a distinct head and 13 body segments. Over the next 14 days, larvae feed on pollen in the lump. Bumble bee species can be divided into two groups based on how they feed their
larva. Pollen storers bring pollen back to the nest and store it in empty pupal cocoons and specially made wax cells. The queen and workers use the pollen stores to progressively feed the larvae by opening up the brood clump, and regurgitating a pollen and nectar mixture into the larval cell. Adults of pollen storing species are relatively equal in size because they are progressively fed as larvae. The other group of bumble
bees called 'pocket makers' build waxen pouches near larval chambers and brood clumps. Workers collect pollen and load these pouches with the pollen. The larvae will then feed on this pollen through their larval chamber. Depending on where an individual larva is compared to the pollen pouch determines the amount of food it will receive. As a result, adults from pocket making nests vary greatly in size. Both pocket making and pollen storing species complete four larval stages called instars. At the end of each instar the larvae molt and become larger. During the fourth and final instar each larva spins an individual silken cocoon. Inside this cocoon the larvae will begin their next developmental stage called the pupal stage. The pupal stage is an inactive stage where immatures' internal organs and body structures begin to mature. Pupae or pupa singular look much like adults but lack adult coloration and hardened exoskeleton. During the pupal stage, the queen will scrape the wax covering from the pupal cells and reuse the wax for another set of brood. Before the adults emerge, the queen begins another set of brood by attaching several additional brood cells with wax to the outside of the older cocoons. After 14 days, adult bumble bees emerge from the silken cocoons. Cells are arranged in a circular shape so that new brood clumps do not impede the emergence of adult bees. When the adult bees emerge, the empty pupal cells are cleaned out and become storage pots for honey and pollen.
Soon after the emergence of the first workers, the queen no longer forages for pollen and nectar. The queen will remain in the nest laying eggs and tending to her young. The female workers take over the responsibilities of collecting pollen and nectar. They also help care for their immature siblings, tend to the queen, and defend the hive. A loose division of labor exists in the bumble bee nest, where one group of workers remain in the nest and help raise the brood and the second group are foragers which bring food back to the nest. Whether a worker becomes a household bee or a forager is decided on the size of the individual bee (Alford 1975; Brian, 1952; Miyamoto, 1963; Sladen, 1912). Smaller workers remain in the nest and are called household bees. 
Household bees build cells to store honey and pollen, care for the young, and defend the nest. Larger workers will forage for nectar and pollen and are called foragers. Foraging bees generally forage within a half-mile radius of the nest and return at night. They begin to forage at two days old and have a life expectancy of four to six weeks. Foraging workers can be observed throughout the spring and summer collecting pollen and nectar for the hive. Although a division exists, house-hold bees will forage for food during times of stress or if the number of foragers drastically decreases.
A nest population can reach between a dozen and several hundred worker bees over the life of the colony depending on the species and the amount of forage food brought in . Over the course of the summer more and more workers are born. With the rising population more food is brought into the nest and eventually the nest reaches its peak. During the nest's peak reproductives are produced. The queen begins to lay
unfertilized eggs and those eggs will grow into adult males. Adult males emerge from their pupal cells and begin to feed. Males do not contribute in collecting food or helping rear young. The sole purpose of the males are to mate with the queens. After 2 to 3 days of feeding they leave the nest permanently. Outside the nest, they feed on nectar from flowers. At night they seek shelter under flowers, plant leaves or other protected areas.
During the cool morning hours it is not uncommon to find several males huddled together in sleeping aggregations under such structures. A few days after the males leave the nest, virgin queens will emerge from their pupal cells. Virgin queens are produced from fertilized eggs and will become next year's queens. As larvae, future queens are fed large amounts of pollen and nectar. The only difference between the virgin queens and workers is that queens are fed larger amounts of food as larvae. After the queens emerge, they feed for 2-3 days and will leave their home nest never to return. Upon leaving the nest, virgin queens will feed on floral nectar and mate with the waiting males. Each species of bumble bees engage in one of three mating behaviors. The first mating behavior is where a male perches on a tall structure, such as the top of a yucca plant, and waits for queens to fly by. Once a queen is spotted, the male will pursue her for mating. Males exhibiting this mating behavior typically have enlarged eyes, possibly for better seeing the queens. 
These males are also highly territorial, and will dart at anything that flies into their flight zone. The second mating behavior is when males create a scent trail, marking their flight path with pheromones. Males will place their scent on structures such as plants, trees and logs and will patrol their path looking for queens. Queens of the same species will be attracted to the pheromones and follow the scent trail. When a male sees a queen following his trail, he rockets to her, knocking her to the ground where he mates with her. The third mating behavior is where males wait at the entrance of a bumble bee nest for virgin queens to leave. Once a queen is spotted, the male will attempt to mate with her. Once fertilized, queens will continue to feed, building up their fat bodies for the approaching winter. Once enough fat bodies are stored, queens will begin searching for suitable overwintering locations to construct their hibernaculums. Once their hibernaculums are constructed, queens bury themselves in and begin hibernation. These overwintering queens are the colony's contribution to the next generation. They carry the genetic torch, ensuring their specie's flame is not extinguished.
