As the temperature warms, daylight increases and flowers begin to blossom, bees can rapidly increase in size and nutrient storage. Because of this, beekeepers have a major task: managing swarms. Swarming is natural system for reproduction, as colonies split into two separate entities. But swarming can also impact colony health, especially if the swarm is not recovered. For sample, the colony is now half the size, so it is splitting an uphill battle for honey production and winter preparation. Because of this, beekeepers must understand the signs of swarming and prevent it.


Why do bees swarm?

Honey bees swarm for a variety of reasons, which include: 1) colony is crowded, 2)abundance of resources, 3) older queen, and 4) mite infestation and/or disease. Typically, bees swarm during the spring because bees are packed into a single brood box as they pack the colony with brood, pollen and nectar. Beekeepers must understand why bees swarm in order to prevent it.

  • Colony is crowded

Colony can become crowded in the spring. If all the frames a packed with bees, then the colony likely needs space.

During the spring, bees rapidly increase in size. This size is attributed to queen laying, as the queen begins laying ~2000 eggs per day. When these eggs eventually become adults, bees can easily become overcrowded. Populated brood boxes are necessary for proper colony health; however, overcrowding often leads to swarming. 

  • Abundance of resources
Resource allocation can inhibit egg laying area for the queen. This is a picture of bee collected pollen.

During the spring, the colony can easily pack the brood boxes with nectar and pollen. However, this may inhibit brood laying area for the queen. While the queen will lay heavily if resources are brought in, the queen cannot lay eggs if space is not available. As nectar and pollen are brought in, this can eventually eliminate brood laying space. If space is not available, then the colony may swarm

  • Old queen
This queen has begun to fail.

An older queen does not necessarily mean the colony will swarm, but the colony is more likely to swarm with an older queen. The colony can sense an older queen because the queen’s pheromone levels decrease and the brood pattern becomes spotty.

  • Mite infestation or disease
This colony is infested with Parasitic Mite Syndrome, mite transmitted viruses

Colonies may swarm if mite levels, pest, pathogens, and diseases reach an uncontrollable levels. Oftentimes, colonies with high disease or mite load will not just swarm, unless these colonies have a genetic predisposition for swarming. For example, africanize bees will abscond or swarm in the presence of various diseases, pest, and pathogens. The backyard beekeepers often does not need to worry about this cause of swarming.

Signs of Swarming

I stated reasons for swarming above, such as space restrictions, resource abundance and older queens. Most beekeepers can prevent swarming by simply providing space or splitting in the spring, and making sure the colony has a young queen. However, if beekeepers do not inspect colonies regularly, they may be in for an unpleasant surprise: signs of swarming. But what are the signs of swarming. They include: 1)size of brood box, 2)bees outside of entrance, 3)size of queen, and 4)Queen cells.

  • Size of broodnest

The colony may look very small because either the colony swarmed or the colony is preparing to swarm. Thus, the size of broodnest is a useful signal for swarming. If the broodnest is small, inspect the colony for other signals of swarming, such as bees outside the entrance and open queen cells.

  • This empty box was placed next to the swarm on the ground and the bees immediately started to enter.
    This empty box was placed next to the swarm on the ground and the bees immediately started to enter.

    Bees outside entrance

Bees releasing pheromone at the hive entrance to guide the rest of the swam in.
Bees outside the entrance can indicate possible swarming, but not always. Look at this signs!

If bees are bearding, this does not necessarily mean the colony is preparing to swarm. However, if bees are outside the entrance due to swarming reasons, this is often too late. The colony is receiving signals from scout bees about their new location and the hive is preparing to launch! If you see bees outside the entrance, these are signs that the colony is about to swarm:

  1. The bees are making a loud sound, almost like a roaring sound
  2. Bees are not only at the entrance, but flying around the colony. This prerequisite of swarming often looks like a “cloud”.
  3. Swarming mostly occurs during mid-morning, so this is when bees may be at the entrance.

Swarming can be confused with bee bearding, but bee bearding occurs due to different reasons, such as overheating and lack of ventilation. While bees at the entrance can indicated swarming, other signs must be considered.

  • Size of queen

After her initial mating flight, the queen is too large to fly. This is because the queen develops mature ovaries for queen laying. But if a colony swarms, the queen also needs to leave the colony, and many times, the older queen leaves with the swarm. In order to swarm, the queen must become smaller. As the colony prepares to swarm, the queen ceases egg laying and becomes smaller. The workers batter and hit the queen to make her smaller, which is a brutal but necessary process. If the colony is about to swarm, eggs will limited and the queen will be quite small. 

  • Queen cells
Swarm cells
Emergency queen cells
Superscedure cells

Queen cells are an obvious sign of swarming. Swarm cells, however, are different from superscedure cells or emergency cells. Swarm cells are found on the bottom on the comb, whereas superscedure and emergency cells are found in the middle. If a colony is about to swarm, there may be handful of swarm queen cells within the colony. The queen cell(s) may be open, which indicates the queen has already hatched. This means the colony has or is about to swarm.


Swarming has many signs, both early and advance. Beekeepers can prevent swarming by providing space in the spring, which often comes down to understand the colony. I will outline preventative and remedial measures in a later blog, but by understand these signs, hopefully swarms can be prevented!

Garett Slater