Swarm Management

A swarm is the honey bee colony's natural way of reproducing: the old queen and about half of the worker bees leave the hive to found a new nest, while the part left behind rears a new queen. Swarm management is less about suppressing this instinct than about steering it under the beekeeper's control; with regular inspections, giving space on time and, when needed, an artificial swarm, both the bees and the harvest are protected.

What is a swarm, and why do bees swarm?

Swarming (casting a swarm, issuing a swarm) is not a disease or a beekeeper's mistake; for the colony it is the reproductive goal of the year. For the beekeeper, however, it means losing much of the workforce and that year's harvest. In addition, the second and third swarms that follow one after another (afterswarms, or casts) weaken the parent colony even further.

What triggers swarming?

• Lack of space: No empty cells left in the brood nest for the queen to lay in; combs clogged with honey or nectar (honey-bound).
• Overcrowding: As bee density rises, the distribution of queen pheromone through the colony weakens; this is an important trigger of swarm preparations.
• An old queen: As the queen ages, her pheromone output falls; colonies with young queens swarm noticeably less.
• A strong nectar flow and heat: Abundant forage and a stuffy, hot hive increase the reproductive urge.
• Genetics: Some breeds and lines are markedly swarmy; breeding from colonies with a low swarming tendency reduces this trait.

None of these factors may be enough on its own; when they pile up, the colony crosses the threshold and starts preparing.

Signs of swarm preparation

• Eggs in queen cups: Bees may build empty queen cups (play cups) at any time; but if an egg has been laid in them, preparations have begun.
• Queen cells on the bottom edges of frames: Swarm cells are usually built in large numbers along the bottom edges and sides of the frames.
• More drone brood and no empty cells left in the brood nest.
• The queen slimming down: Before swarming, workers feed the queen less; she becomes lighter so that she can fly, and her laying declines.
• Less foraging, and bees that look idle and cluster in front of and inside the hive.

How do you tell a swarm cell from a supersedure cell?

Not every queen cell means swarming. Swarm cells are usually numerous and lined up along the bottom edge or sides of the frames. Supersedure (silent queen replacement) cells, on the other hand, are few (often 1–3) and in the middle of the comb face; the colony replaces its ageing queen without swarming. In a colony that has become queenless, emergency queen cells converted from worker cells are seen on the comb face. This distinction is not absolute, but it guides the decision on whether to intervene: supersedure cells are generally left alone.

When does a swarm issue? The eight-day rule

About 8 days after the egg is laid in a queen cell, the cell is sealed, and about 16 days after, the new queen emerges. The first (prime) swarm usually leaves with the old queen, in suitable weather, around the time the first queen cells are sealed.

This is why the inspection interval during the swarming season must be less than eight days; in practice hives are checked every 7 days. A beekeeper who looks every ten days sees the queen cells only after they have been sealed, which usually means after the swarm has left.

How do you prevent swarming?

• Give space on time: Empty comb or foundation for the queen in the brood nest, and a super on top, before congestion sets in.
• Take out sealed brood: Giving a frame of sealed brood close to emergence from a strong colony to a weak one both lowers the pressure and strengthens the other colony.
• Requeen: A young queen markedly reduces the swarming tendency. Many beekeepers replace their queens every two years.
• Ventilate: A hot, stuffy hive triggers swarming; in summer open the entrance fully and provide shade.
• Use a drone frame: A frame that allows bees to build drone cells concentrates the demand for drone brood in one place; cutting it out once sealed also contributes to varroa control.
• Select lines with a low swarming tendency: Breed from colonies that, according to your records, do not swarm.

Cutting out queen cells is not a solution on its own. If the colony has made up its mind, it builds new ones within a few days, and missing a single cell is enough for a swarm to issue. Moreover, cutting out all the cells without noticing that the old queen has already left with a swarm leaves the colony queenless. Removing the symptom without removing the cause does not work.

If swarm preparations have started: the artificial swarm

If larvae are seen in the queen cells, the colony has made its decision. The most reliable course is to make the swarm yourself. The classic artificial swarm method is carried out as follows:

1. Move the parent hive a few paces to one side, and put a new hive on its old site.
2. In the new hive, put a frame with the queen on it (it must have no queen cells) and foundation or empty comb beside it. Put the super on top of this hive.
3. The foragers return to the old site, i.e. to the new hive with the queen; the colony behaves as if it has swarmed, and the swarming urge subsides.
4. The brood, young bees and queen cells stay in the old hive that was moved aside. Leave the one or two best-looking cells here and reduce the rest; otherwise afterswarms will issue.
5. About a week later the old hive can be moved once more to direct the remaining foragers to the hive with the queen; this prevents the old hive from swarming again.

The result is two colonies, with the honey-gathering force concentrated mostly in the hive with the queen. The old hive goes through a short broodless period until the new queen starts laying; this is a favourable window for varroa treatment.

What to do if a swarm has left: collecting a swarm

A swarm leaving the hive usually settles on a nearby tree branch, bush or wall and waits in a cluster while scout bees search for a new nest. Swarming bees have full honey stomachs and no brood to defend, so they are usually calm. Protective clothing should still be worn.

1. Preparation: A ventilated swarm box or an empty hive with a few combs in it is prepared.
2. Collecting: The branch holding the swarm is shaken with one firm movement so that the bees drop into the box. Where it cannot be reached, a brush or swarm scoop can be used.
3. Checking for the queen: Wait a few minutes. If the queen is inside, bees at the entrance raise their abdomens and fan their wings to spread scent, and the bees outside stream in. If the bees gather back on the branch, the queen has stayed outside; repeat the process.
4. Hiving: The swarm is put into its new hive in the late afternoon or evening. Frames with foundation are given; feeding syrup for a few days speeds up comb building.
5. Varroa: Because the swarm is broodless for a few days, an authorised treatment applied before there is sealed brood effectively reduces the mite load.

The health history of a swarm collected from elsewhere is unknown; keeping it apart from other hives for the first few weeks and watching its brood carefully is a good precaution.

What should you do with the hive that swarmed?

• The hive contains many queen cells. After the prime swarm, the first virgin queens to emerge may also leave as afterswarms, and the colony dwindles.
• Within a few days of the swarm leaving, reduce the cells and leave the one or two sealed cells that look best.
• About a week later, check for newly built emergency cells and remove them.
• While the virgin queen makes her mating flights, the hive is not opened unnecessarily; look for eggs about 3–4 weeks later.