The Secrets of Swarming Instinct: Why Do Bees Leave the Hive?
The Biological Purpose of Swarming
Swarming is the natural method of reproduction for bee colonies, programmed by evolution to ensure the survival of the species. While a single bee cannot live independently, the colony as a “superorganism” strives to divide when it reaches the peak of its development. This process typically occurs from late May to early June, after the first strong nectar flows (e.g., spring honey flow) have ended, when a large number of young bees, not yet burdened with work, accumulate in the hive.
The Chemical Brake: Queen Substance
The key to colony unity is the queen substance, primarily produced by the queen’s mandibular glands. The main component of this pheromone is 9-oxo-2-decenoic acid.
- Function: It inhibits the development of ovaries in worker bees and prevents them from building queen cells for swarming.
- Distribution: Bees from the so-called retinue lick this substance from the queen’s body and pass it to each other during feeding (trophallaxis).
- Deficit: When the queen ages, becomes ill, or when the colony becomes too populous, the amount of pheromone per worker bee decreases. Just 5–6 hours after the substance disappears, the bees “sense” its absence and begin constructing queen cells.
Factors Triggering Swarming Fever
The swarming instinct is activated by a combination of genetic and environmental factors:
- Overcrowding and lack of space (congestion): A lack of empty cells for egg-laying limits the queen’s fecundity.
- Poor ventilation (stuffiness): High temperature and elevated CO2 concentration (even up to 8.3%) provoke bees to form clusters under the hive (so-called beards).
- Excess of royal jelly: When there are more nurse bees in the hive than brood to feed, the surplus of produced royal jelly alters their physiological state and stimulates the instinct.
- Lack of nectar flow: A break in the influx of nectar (e.g., between orchard and raspberry blossom) promotes idleness and swarming.
The Mechanics of Swarm Emergence – A Step-by-Step Process
Step 1: Preparation (The Cup Stage) Bees build queen cell cups on the edges of the combs, into which the queen lays eggs. In strong colonies of Caucasian bees, up to 10 are built, while other races build significantly more.
Step 2: The Queen’s Diet and Slimming Down Worker bees stop feeding the queen royal jelly, forcing her to eat honey. As a result, the queen reduces egg-laying, her ovaries shrink, and her body weight decreases enough for her to regain the ability to fly.
Step 3: The Work of Scout Bees Even before the swarm emerges, scout bees search for a new home. They assess potential cavities for protection from wind, scent, and distance (too close risks food competition).
Step 4: Swarm Emergence (The Prime Swarm) The first swarm (the prime swarm) with the old queen usually emerges on the 9th day after eggs are laid in the cups (after the first queen cell is capped).
- Timing: Most often between 10:00 AM and 1:00 PM on a sunny day.
- Signal: Scout bees perform specific movements and produce sounds, to which the bees respond by massively filling their honey crops (provisions for about 3 days of flight).
- Cluster Formation: The bees settle on a branch, and thanks to the Nasonov gland (releasing a specific scent), they guide the remaining workers to the queen’s location.
The “Singing” of Queens and Subsequent Swarms
If the swarming fever persists, the colony may send out subsequent swarms (after-swarms, casts) with young, unmated queens.
- Piping (Tukanie): The first emerged queen runs over the combs, emitting high-pitched “ti-ti-ti” sounds.
- Quacking (Kwakanie): Queens still confined in their cells respond to her with muffled “quack-quack” sounds. The bees deliberately prevent them from emerging to avoid immediate fighting and to allow the next swarm to depart.
The Energetics of a Swarm
A single bee consumes up to 25% of its body weight daily, while bees in a swarm cluster lose only 1.5% of their mass per day. This allows the swarm to survive cold nights and preserve the energy essential for the rapid construction of a nest in a new location (so-called swarm energy).