What Is the Life Cycle of Bumblebees? Egg to New Queen
What is the life cycle of bumblebees? It runs on an annual clock: a single mated queen starts a nest alone in spring, and by the following spring every bee from that colony except her daughter queens is dead. In North America, a bumblebee colony persists for just under one year, moving through four stages: egg, larva, pupa, and adult.
The Four Stages, Start to Finish
Each stage overlaps with the next as the colony grows, but every individual bee passes through the same sequence.
1. Egg
A queen emerges from hibernation in early spring, feeds to rebuild her fat reserves, and searches for a cavity to nest in, commonly an abandoned rodent burrow or a clump of dense grass thatch. Once she has amassed a store of nectar and pollen, she lays her first cluster of eggs, each about 1 millimeter long and creamy white.
- Duration: 3 to 4 days before hatching.
- Detail: This first batch develops entirely into daughter workers, not queens.
2. Larva
The hatched larvae look like pale, legless grubs and cannot feed themselves. The queen provisions them with a mix of nectar and regurgitated pollen and shares the nest's warmth by pressing her body against the brood cells.
- Duration: Roughly 10 to 14 days, with several molts as the larva grows.
- Detail: At the University of Wisconsin's Bumble Bee Brigade research site, the first workers were recorded emerging from their cocoons 2 to 3 weeks after the eggs were laid, spanning the larval and pupal stages combined.
3. Pupa
Before pupating, the larva spins a silk cocoon around itself. Inside, it undergoes metamorphosis, breaking down larval tissue and rebuilding it into the head, legs, wings, and compound eyes of an adult bee.
- Duration: About 1 to 2 weeks.
- Detail: The pupa is immobile and entirely dependent on the nest's temperature staying stable.
4. Adult
The bee chews its way out of the cocoon pale and soft, then hardens and darkens over the next day. The first adults are always female workers, who take over foraging and nest maintenance so the queen can stay inside and keep laying eggs.
- Duration: Workers typically live a few weeks; a queen that survives winter can live close to a year.
- Detail: Only late-season daughters mate and become next year's queens; everyone else in the colony, including the founding queen, dies by autumn.
How Big Does a Colony Get
Colony size depends heavily on species. Documented bumblebee colonies range from as few as about 20 individuals up to several hundred at their summer peak, with most falling somewhere in between. Compare that to a honeybee hive, which commonly holds tens of thousands of workers year-round. Bumblebee colonies stay small because a single queen, not a mated group, builds the entire nest from scratch each spring.
Why the Season Ends the Way It Does
By late summer the colony produces its final generation: unmated males (drones) and new queens (gynes). The drones leave the nest to mate and do not return. Mated gynes feed heavily to build fat reserves, then dig into loose soil or leaf litter to overwinter, often just a few centimeters down. During diapause they produce glycerol-like antifreeze compounds that keep their cells from rupturing in freezing temperatures; overwintering can last 6 to 9 months depending on the species and climate. Meanwhile the founding queen, her workers, and the season's drones all die off as temperatures drop and flowers stop blooming.
Buzz Pollination Sets Bumblebees Apart
Bumblebees pollinate crops that honeybees mostly ignore because they can sonicate: gripping a flower's anther and vibrating their flight muscles to shake pollen loose. Tomato, pepper, and blueberry flowers hold their pollen tightly inside tube-shaped anthers and produce no nectar, so honeybees have little reason to visit them. Bumblebees buzz-pollinate them anyway to collect the pollen itself, and greenhouse tomato growers rely on commercial Bombus impatiens colonies specifically because of this behavior.
Pressure on Wild Populations
Several North American bumblebee species have declined sharply in recent decades, driven by habitat loss, pesticide exposure, climate shifts that push emergence out of sync with flowering, and pathogens spread from commercial bumblebee and honeybee colonies. The rusty patched bumblebee (Bombus affinis) became the first bumblebee species listed as endangered under the U.S. Endangered Species Act, in January 2017, after its numbers had declined across roughly 87 percent of its historical range.
Leaving patches of bare or thatched ground undisturbed, planting native flowering species that bloom from early spring through fall, and cutting back on insecticide use all give queens a better shot at founding a nest that survives to produce next year's queens.
