Honey bee swarms, the dense, buzzing clouds that appear in springtime, are the primary method of reproduction for a honey bee colony. This sudden mass migration is often misunderstood, but it is not an attack. The spectacle of thousands of insects moving as a single unit naturally leads to curiosity about the number of bees involved.
The Biological Mechanism of Swarming
Swarming is triggered by springtime growth causing overcrowding within the original hive. As the colony population expands and available space decreases, the bees prepare to split the colony. This congestion, combined with an abundance of nectar and pollen, signals the time for colony reproduction.
The process involves worker bees raising a new queen in the existing hive. Once the new queen cells are capped, the queen leaves with a significant portion of the worker population, typically 40% to 70% of the adult bees. The original hive is left with the remaining bees, brood, and the developing new queen, ensuring the mother colony’s survival.
The departing swarm gorges on honey before leaving to provide fuel for the journey and wax production. This consumption makes the bees docile and less likely to sting, as they focus on establishing a new home.
Typical Population of a Bee Swarm
A primary bee swarm, the first to leave the colony, commonly contains between 5,000 and 10,000 individual bees. The total number is highly variable and depends on the strength and size of the parent colony before the split. A very large colony may cast a primary swarm of 20,000 bees or more.
Smaller “after-swarms” may occur later, containing only a few hundred to a couple of thousand bees, often accompanied by an unmated virgin queen. A typical swarm often weighs between three and seven pounds, representing the mass of the bees and the honey they consumed.
The weight-to-bee ratio provides a reliable metric, averaging 3,000 to 4,500 bees per pound of clustered swarm. For example, a five-pound swarm contains roughly 15,000 to 22,500 bees. Visually, a cluster the size of a basketball often holds around 9,000 to 19,000 bees.
Methods for Estimating Swarm Population
Since counting individual insects is impossible, beekeepers and researchers rely on indirect methods to estimate the population of a swarm. The most accurate field method involves calculating the total weight of the clustered bees. Knowing the typical weight of a single worker bee allows the total mass to be converted into a population estimate.
The volume of the cluster is another common way to quickly gauge population size using visual comparisons. Honey bees cluster at a density of about 1,500 to 2,000 bees per liter of space. This density allows for quick, though less precise, estimations based on the size of the temporary cluster.
For example, a cluster that fills a five-gallon bucket is estimated to contain 15,000 to 20,000 individuals. Researchers also use digital methods, such as photographing the swarm and using image analysis software to count bees in a known area, then extrapolating that count to the entire cluster.
The Swarm’s Next Steps
After leaving the original hive, the entire bee mass temporarily settles close by, often on a tree branch or shrub, forming a dense, beard-like cluster. At this stage, the swarm is focused on finding a permanent new nest site and is generally calm. The decision-making process is delegated to a small fraction of the group called scout bees.
These experienced scout bees fly out to locate and evaluate potential nesting cavities, such as hollow trees or wall voids. Upon returning, successful scouts communicate the quality, direction, and distance of their find using the waggle dance. The dance direction corresponds to the new site’s location relative to the sun.
The duration of the waggle run indicates the distance, and the vigor of the dance communicates the site’s quality. Other scout bees visit the advertised locations, and the entire swarm reaches a collective decision through quorum sensing. Once enough scouts agree on the best site, the entire swarm takes flight and migrates to its new home.