Unlike honey bees, which overwinter as a colony by clustering together, bumblebees (Genus Bombus) live from spring to fall. Only the fertilized bumblebee queen will survive the winter by finding shelter from the freezing temperatures.
In spring, the queen emerges and searches for a suitable nest site, typically in an abandoned rodent nest or small cavity. In this space, she builds a ball of moss, hair, or grass, with a single entrance. Once the queen has constructed a suitable home, she prepares for her offspring.
The spring queen builds a wax honey pot, and provisions it with nectar and pollen. Next, she collects pollen and forms it into a mound on the floor of her nest. She then lays eggs in the pollen, and coats it with wax secreted from her body.
Like a mother bird, the Bombus queen uses the warmth of her body to incubate her eggs. She sits on the pollen mound, raising her body temperature to between 98° and 102° Fahrenheit. For nourishment, she consumes honey from her wax pot, which is positioned within her reach. In four days, the eggs hatch.
The bumblebee queen continues her maternal care, foraging pollen and feeding her offspring until they pupate. Only when this first brood emerges as bumblebee adults can she quit the daily tasks of foraging and housekeeping.
For the remainder of the year, the queen concentrates her efforts on laying eggs. Workers help incubate her eggs, and the colony swells in number. At the end of summer, she begins laying some unfertilized eggs, which become males. The bumblebee queen allows some of her female offspring to become new, fertile queens. With new queens ready to continue the genetic line, the bumblebee queen dies, her work complete.
As winter approaches, the new queens and males mate. The males die soon after mating. The new generations of bumblebee queens seek shelter for the winter, and wait until the following spring to begin new colonies.