The queen bumblebee is the sole founder and largest individual within her colony. Her substantial size reflects her reproductive role, which requires considerable energy reserves and a large body cavity for producing eggs. This physical dimension fluctuates dramatically throughout her life cycle, influencing her survival and the ultimate success of the entire colony. Understanding the queen’s size provides insight into her demanding life history.
Physical Dimensions of the Queen
The body length of a queen bumblebee varies significantly across the nearly 250 species in the genus Bombus. Common North American and European queens typically measure between 17 and 25 millimeters. For a common species like the Buff-tailed bumblebee (Bombus terrestris), the queen’s length often falls in the 20 to 22 mm range.
The queen’s weight is even more variable than her length, generally ranging from 0.46 to 0.85 grams, depending on the species and her physiological state. Her body mass is dominated by a robust thorax, which houses the powerful flight muscles necessary for foraging after hibernation, and a large abdomen.
How Size Changes Over the Queen’s Life Cycle
The queen’s size is not static, undergoing major changes driven by her annual cycle of hibernation and reproduction. A newly emerged queen is the largest bee produced by the colony, having received significantly more pollen as a larva than her worker sisters. This extensive feeding allows her to develop a large exoskeleton and accumulate substantial fat reserves before she mates and enters winter diapause.
During the winter, the queen survives entirely on these stored lipids, and her body mass decreases as she burns fat. When she emerges in the spring to begin colony founding, she is lighter than her pre-hibernation peak, having depleted a portion of her stores. She then forages heavily to replenish her energy before locating a nest site and laying her first batch of eggs.
The most noticeable size change occurs later in the season when the queen becomes “gravid,” meaning her abdomen swells significantly with developing eggs. At this point, she stops foraging and remains inside the nest, focusing solely on egg production. Her newly emerged worker daughters take over the tasks of gathering food and maintaining the colony. This egg-laying phase represents her maximum functional size and weight.
Comparing the Queen, Worker, and Drone
The queen is the largest of the three castes, a crucial visual distinction from the smaller workers and the medium-sized drones (males). In common species, the queen is often two to three times the size of a typical worker, whose length may measure 8.5 to 17 mm. Workers are the smallest caste, characterized by their relatively slender build.
Drones are intermediate in size, generally larger than workers but smaller than the queen, typically measuring between 12 and 18 mm in length. While the queen is robust across her entire body, the drone can be identified by a plumper, more barrel-shaped abdomen and noticeably larger compound eyes that meet or nearly meet at the top of the head. The queen’s most distinguishing feature is her massive abdomen, which is necessary to house the reproductive organs capable of generating the entire colony’s population.