A swarm of bees is one of nature’s most dramatic sights, often appearing as a dark, buzzing cloud or a large, hanging cluster on a tree branch or post. While this mass of moving bees may look aggressive, swarming is a necessary and natural process of reproduction for the honeybee colony. It is a highly coordinated survival mechanism that ensures the continued existence of the species by splitting one robust colony into two new ones.
The Primary Trigger: Colony Overcrowding and Reproduction
The fundamental cause of swarming is the colony’s need to reproduce itself. This process is set in motion when the hive population booms, leading to overcrowding and congestion inside the nest. As the population density increases, the queen’s pheromones, which maintain colony cohesion, become diluted and less effective throughout the hive.
Workers interpret this diminished pheromone signal as a sign that the colony is too large, triggering preparations for division. They begin constructing specialized, peanut-shaped structures known as swarm cells, usually along the bottom edges of the honeycomb. The existing queen lays eggs in these cells, and workers feed the developing larvae royal jelly to raise new queens. To prepare for flight, workers also reduce the current queen’s food intake, causing her to lose up to half her body weight so she can fly with the departing swarm.
The Departure: How the Swarm Forms
Once the new queen cells are capped and a virgin queen is close to emerging, the old, mated queen leaves the original hive, taking roughly half of the adult worker bees with her. Before departing, the worker bees gorge themselves on honey, filling their stomachs to carry fuel for the journey and the effort of building a new nest.
The group exits the hive in a massive cloud of flight, often settling on a nearby object within a few dozen yards of the original nest. This temporary resting location, called a bivouac, allows the queen to rest and the swarm to cluster tightly around her. The cluster, which can hang from a tree branch or post, serves as a staging area while the next phase begins.
The Search for a New Home
While the swarm remains clustered, dozens to hundreds of older, experienced worker bees known as scout bees fly out to find a suitable permanent cavity. These scouts search for ideal locations, such as dark, dry enclosures like hollow trees, rock crevices, or wall voids that offer protection and space.
Upon returning to the cluster, a scout bee communicates the location and quality of her finding using a precise figure-eight movement called the waggle dance. The direction of the dance indicates the direction of the proposed site relative to the sun, and the duration of the “waggle” portion indicates the distance. Other bees inspect the most promising sites, and the swarm reaches a collective decision through this democratic process. Once a quorum is reached, the entire cluster takes flight, moving to establish their new home.
Swarm Temperament and Safety
Despite the unnerving appearance of thousands of bees, swarms are docile and non-aggressive. This is because the bees are focused entirely on survival and relocation, not defense. They have no home, brood, or stored honey to defend, which are the primary triggers for defensive stinging in an established colony.
If a swarm is encountered, the safest action is to remain calm, avoid sudden movements, and keep a safe distance. Do not spray the bees with water or chemicals, as provoking them is the only thing likely to trigger defensive behavior. Contact a local beekeeper or beekeeping association for safe, humane removal and relocation.