Do bumble bees fly south? Hibernate? Keep themselves warm like honey bees? Why don’t we see them flying around on a warm winter day?
Even though honey bees and bumble bees are closely related (in the family Apidae) and even though they are both social bees, their life cycles are very different. While entire honey bee colonies can survive a northern winter, bumble bee colonies cannot.
A newly mated queen hibernates in the ground
A newly mated bumble bee queen overwinters by hibernating in a small nest in the ground, just big enough for her. This tiny abode, known as a hibernaculum exists 5 to 15 cm below the soil surface. For safety, the tiny opening is often obscured by mulch or leaf litter. As winter temperatures get colder, the queen produces a chemical in her body (glycerol) that keeps her from freezing, and she remains buried all winter.
After she emerges in the spring, the queen searches for a site to use as a nest for her future colony. Spring queens examine holes in the ground, looking for potential nesting sites. They often prefer sites that once belonged to other animals such as rodents or birds. The queen may go in and out of a potential site many times before moving on or making a selection.
Some species of bumble bees search for a nest above ground. Popular spots include empty bird nests, mailboxes, compost heaps, and barn lofts.
Starting a family in spring
Once she has decided on a site, the queen begins building a nest, laying eggs, and foraging for nectar and pollen. At first, she does all the work by herself–a single working mother. But after the first batch of brood emerges, the new workers assist in foraging, nest maintenance, and raising their sisters. Eventually, the queen will have produced enough workers that she no longer has to leave the nest, and egg-laying becomes her full-time job.
The population of the bumble bee nest continues to increase all summer and into the fall. But at some point, often late in summer, the queen begins to produce virgin queens and males instead of just workers. These new queens and male bees mate with bees from other colonies.
The cycle repeats in autumn
After mating, a new queen goes off to find a place to spend the winter just as her mother did. The rest of the colony, including all the workers, the males, and the original queen, perish with the approach of winter. Each of the hibernating queens, by herself, will awake in spring and begin the daunting task of finding a home and building a brand new colony from scratch.
Honey Bee Suite