Swarming and Swarm Prevention
Swarming
Swarming is the honey bees' natural means of migration. A majority of the hive population, together with the existing queen, leave and seek out a new location. There may be successive swarms, in which case the queen that accompanies these secondary swarms is usually a virgin. From the standpoint of the beekeeper, swarming is highly undesireable since it seriously reduces honey production. And of course hobby beekeepers, especially those in urban areas, have to be concerned about where the swarm decides to cluster.
Generally speaking, the time of year when swarming is most likely is the spring, particularly from around mid-May to early June. The main, but not exclusive, factor determining whether bees will swarm is the amount of room in the hive. If there is a strong honey flow, the bees may bring in nectar so rapidly that they quickly exhaust the available space, both for storage and for the queen to lay eggs. This is much more likely to happen if the hives are located near an agricultural area where there is an early nectar-producing crop, but can still happen elsewhere, depending on the local flora.
Usually, a swarm will not leave a hive until there is a sealed queen cell from which a new queen will emerge in day or so. If the bees swarm in the spring, the new queen has time to mate, start laying eggs, and the hive can rebuild its strength. If the swarm leaves later, for example mid-summer, that is a potential problem because the hive may not have time to build up adaquate honey stores to last through the winter. Even if some bees survive. their numbers may be too small for the hive to get going in the spring. There must be adaquate numbers of both nurse bees and foraging bees for a hive to do well.
Another factor is the time between honey flows. If there is a strong flow in the spring, the bee population will build up. If there is a long gap before the summer honey flow, the bee population will become very large because older workers are not dying off.
Swarm Prevention
Swarming can be delayed by destroying queen cells as they are built, since a swarm will not leave the hive until a new queen is nearly ready to emerge. This is basically a temporary measure, since the bees will keep trying to raise a new queen for as long as they have the impulse to swarm. Avoiding a swarm generally involves providing more room or, in the case of moveable frame hives, dividing the hive. Since the age of the queen is also a factor in swarming, many serious beekeepers will replace the queen each year or every other year. Requeening can be done in the spring, summer, or in the autumn. There are advantages and disadvantages to requeening in any of these seasons.