Bumblebees are important pollinators. Understanding their nesting habits offers insight into their biology and contributes to their conservation. These fuzzy insects establish new colonies each spring, with a single queen searching for a suitable location to raise her offspring.
Physical Characteristics of Nests
A bumblebee nest differs considerably from the organized, hexagonal structures of honeybee hives. Bumblebee nests contain a messy, lumpy group of round wax cells and pollen lumps. The queen constructs small wax pots for storing nectar, along with wax brood cells where eggs are laid. Silk cocoons from developing bees can also be visible within the nest.
The size of a bumblebee nest varies depending on the species and the colony’s age, with established nests potentially housing up to 400 individuals, though some species have smaller nests with around 50 workers. Bumblebee nests are lined with insulating materials such as leaves, animal fur, or dry grass, which help regulate temperature.
Underground and Surface Nesting
Most bumblebee species prefer to nest in dry, enclosed spaces that offer insulation and protection from the elements. A common choice for many species is abandoned rodent burrows, as these provide ready-made, insulated cavities. Bumblebees do not dig their own burrows but instead utilize existing holes. These underground nests can also be found in natural depressions, under tree roots, or within dense clumps of grass.
Surface-level nesting sites include areas under sheds, in compost heaps, within thick leaf litter, or under dense, mossy vegetation. Queens seek out locations that are dry and do not receive excessive direct sunlight, which could lead to overheating. When searching for a site, a queen may fly in a slow, zig-zag pattern, low over the ground, using both sight and smell to investigate potential spots.
Above-Ground Nesting
While less common than ground nests, some bumblebee species also establish colonies above ground. Locations include birdhouses, wall cavities, attics, tree holes, old furniture, under building foundations, or within patio furniture cushions.
These above-ground nests are found in pre-existing cavities, as bumblebees do not chew through wood or create their own extensive tunnels. They are opportunistic nesters, utilizing spaces that already provide shelter and insulation.
Distinguishing Bumble Bee Nests
Identifying a bumblebee nest involves observing both the physical characteristics of the nest entrance and the behavior of the bees themselves. Bumblebee nest entrances are small, sometimes no larger than a penny, though they can vary. Observing bees consistently entering and exiting a specific hole or clump of vegetation is a strong indicator of a nest. Bumblebees are generally docile and will only sting defensively if they feel their nest is threatened, for example, by vibrations from a lawnmower.
Unlike honeybees, which form large swarms and build highly organized hexagonal combs, bumblebees do not swarm. Their nests are comparatively small, housing dozens to a few hundred individuals, not tens of thousands. Bumblebees also have fuzzy, stout bodies, distinct from the more slender, less hairy appearance of wasps or the shiny abdomens of carpenter bees. Carpenter bees bore into wood, while bumblebees utilize existing cavities.