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Given the right conditions (especially in springtime), a colony will typically divide itself and swarm, taking the old queen with them, and leaving behind “swarm cells” containing replacement daughters about to emerge.

Practical application: It is normal for a colony to reproduce by swarming once it's filled its cavity (whether a tree hollow or a hive). This normally occurs during the local “swarm season,” and especially with queens that are over a year old. Some swarming may also occur in crowded colonies later in the season.

One can generally tell whether a colony is preparing to swarm by tipping up the brood chamber (or upper brood box in a double). Most (but not all) swarm cells will be built along the bottom bars of those brood frames (Figures ).

Practical application: Queen cells are easily damaged if one attempts to cut them from a wooden frame. But frames containing queen cells can be carefully moved to a split.

Figure 5.16 Typical queen cells, some sealed, some in development, along the bottom bars of an upper brood chamber. This colony could be split, with each portion receiving at least one frame with a queen cell.

Figure 5.17 Typical swarm cells along the bottom bar of the upper brood chamber.

Figure 5.18 Bottom view of swarm cells prior to sealing. Note the huge amount of jelly beneath the young larvae, which will be consumed after sealing of the cell. Also note the typical presence of drone cells and drones. Of interest is that the jelly fed to larvae (including the queen) allows for transgenerational immune priming via dsRNA.

Source: Maori et al. (2019).

Figure 5.19 An emerged queen cell, indicating that the colony has recently swarmed, and that it is too late to take preventative measures.

The colony swarms prior to the emergence of the queen cells. If the weather does not permit swarming, or if resources dry up, the colony will destroy the swarm cells without swarming.

Practical application: If the colony has recently swarmed, you will generally be able to see emerged cells, often with the round capping still attached (Figure 5.19). If, on the other hand, all the queen cells have been chewed out from the side, the colony may have “changed its mind.”

Practical application: A colony first issues a “prime swarm” containing a mated, successful, but typically aging queen. If the remaining colony is still too large for the cavity, one or more virgins may leave in “afterswarms.” Young queens will not tolerate a rival sister (Figure 5.20). In the case of either a swarm or an afterswarm, only one queen will be left remaining.

Swarming is coordinated by a few “experienced” workers (Rangel and Seeley 2008, 2010) rather than being controlled by the queen. The queen is pushed to exit the hive. Not all queens (which may not have flown for a year or more) are able to do so (Figure 5.21).

Practical application: With time, the setae (“hairs”) on a queen's body get worn off, especially on the top of her thorax. This is one way to tell how old a queen is.

After emerging from the hive, a swarm temporarily bivouacs on a tree limb or other resting place while the scouts decide upon a permanent nest site. Beekeepers use this opportunity to “hive” a swarm by shaking it into an empty (not containing bees) hive (Figure 5.22).

Practical application: A swarm may contain several queens, most being virgins. Workers may form protective walnut‐sized “balls” around them, that can be picked up and used to start new colonies.

Once a swarm settles into a new cavity, the new colony is in a race against time, since the average longevity of a worker bee is about 35 days, and it takes around 20 days to complete a brood cycle. It is astounding how rapidly a swarm can build out a new hive and grow – provided that there is either a nectar flow on, or the colony is fed sugar syrup.