For long periods of time, life goes on comfortably inside the hive. On long, warm, sunny days, the queen is busy laying eggs. They house bees keep the hive in good working order. They do this by cleaning and polishing cells and packing them with honey and pollen. This honey is produced from the nectar collected by the forager bees. The house bees add enzymes to the nectar to change its chemical composition. As the water in the honey evaporates and the bees respire, the hive becomes humid and warm. The house bees are responsible for fanning in order to cool and freshen the hive. They must also devote considerable attention to the needs of the queen and the queen's egg laying. After the queen lays eggs, the house bees must cap the comb cells, and rear the brood. House bees must also secrete wax and build comb in anticipation of the need for future brood and food storage. In preparation for their jobs as foragers, house bees will take orientation flights. Honey bees can raid another hive as a method of collecting resources. Some of the older house bees are assigned to guard the hive and ward off attacks. During the daylight hours, forager bees are going about the business of collecting nectar and pollen. Drones looking to mate make their daily afternoon flights.
These conditions cannot continue forever. At some point, the hive will become overcrowded or will be disturbed. Environmental conditions may change - the hive may be under attack by a bear, by ants, or by fire. In these instances, the hive must make a critical decision.
When the population of a colony becomes too large for its nest site, the bees begin performing several special activities. Some of these activities are visible to someone observing the hive. Bees can be seen clustering outside the hive. Scout bees begin to search for a new site. Even on a clear warm day, a hive preparing to divide into two or more colonies does little foraging. Inside the hive, the house bees begin to construct large vertically hanging queen cells. The workers begin to engorge themselves on the honey reserve in preparation for a swarm.
The scouts begin by making an exhaustive search for nearby sites. The typical choice for a new hive is a quarter to a half mile away. However, the bees are willing to look considerably farther if it is necessary. They seek out cavities having on opening less than 12 square inches situated 3 or more feet above the ground. Ideally, the entrance to the cavity is well below the roof. The preferred sizes are between 600 and 6000 square inches. This volume is small enough so that the colony is likely to outgrow it within a year, but large enough so that the hive has a good chance for survival. The shape of the cavity does not seem to matter.
If a scout finds a potential site for the new hive, she will communicate the location of her finding in much the same way a forager communicates the location of a food source. The scouts inspect each others findings and reach a consensus. If the weather conditions are right, the hive is now ready to make its move.
Swarming is initiated by a special dance, the Schwirrlauf, the German word for whir dance. During the Schwirrlauf, workers move without stopping in straight lines across the comb. Every couple seconds, they vibrate their partially spread wings. These dancers also make occasional five second contacts with other worker bees. During this contact the bee makes a continuous piping sound.
For situations that are not emergencies, the colony may divide. Part of the hive stays behind with the new queen, which may still be in her larval state. Although scientists are not certain on this point, the bees that swarm seem to be a random selection from the entire population. Thus, the swarm contains a mixture of bees of all ages. The majority of swarms take place within an hour of the middle of the day. Because drones do most of their flying in the afternoon, morning swarms are likely to contain drones.
When a swarm first emerges from the hive, it chooses a nearby bush or tree to settle. This is a particularly dangerous time for the colony. For example, if rain begins falling at this point, the bees cannot fly to their new nesting site and resume their usual activities. Consequently, the colony might starve. If the weather remains suitable, the bees make sure that their queen is present. The scouts then leave the swarm to find their choice for a new hive and to verify that the area is still favorable. Most of the scouts then return and report to the others its location by performing a wagtail dance on the surface of the swarm. At first the hive moves very slowly - taking 5 minutes to move 100 yards. At this time, the colony again checks that the queen is with them. The swarm then spreads out to fill a space about 50 yards in diameter and speeds up to 6 miles per hour - flying between 3 and 10 feet above the ground over and not around obstacles. A couple hundred yards before reaching the site of their new hive, the swarm slows down. The scout bees at the new site are performing a "breaking" dance as a guide to the scouts that are escorting the swarm.
At this time, the scouts take positions near the hive entrance and leave a scent to attract the queen and workers. Most of the workers will enter the site before the queen enters.
For hives having a high population, additional swarms of bees may leave at the time that virgin queens are making their nuptial flights. In this manner, the original colony may divide to form several new colonies.
If the swarm takes with it an older queen, then shortly after establishing the new hive, the queen is replaced by a daughter. This event, termed supercedure, also takes place in any colony that has an old or failing queen. The queen produces a chemical substance that inhibits her replacement. As time goes on, she produces less and less of this substance. As a consequence, her ability to forestall being superceded becomes weaker and weaker. Like the case in which house bees detect that the colony is about to divide, the bees begin to produce queen cells. Typically, they will not make quite as many queen cells as they make in preparation for colony division. Supercedure is necessary because the queen has a diminished capacity for laying brood. Also the lack of spermatozoa in the spermatheca means that the queen is more likely to lay unfertilized eggs, that is, eggs that will become drones.
When a young queen hatches into a colony having a queen, the older queen is usually killed. In some situations, the older queen continues living and producing brood until her successor begins to lay. Sometimes the workers will kill an old queen with no other queen present or before the young queen starts producing brood. In either circumstance, because young queens produce little of the chemical that inhibits supercedure, the worker will begin to develop emergency queen cells. These cells are made by enlarging worker cells.
After the young queen emerges, the hive may choose to kill any of the remaining queens while they still reside in their cell. This can be a risky strategy. If the young queen fails to return to the hive after her nuptial flight, the the colony will perish. The hive may also choose to attack other queens after they have emerged. The bees can also prevent the first young queen from attacking the young queens still in their cells by leaving or adding wax to the queen cell capping. They can also feed these young queens while they are still in their cells. For very large colonies, this delay in queen emergence allows the hive to divide into more than two colonies.
Bees can face a variety of enviromental emergencies - food or water resources become scarce or the bees sense a threat to the hive. Under these circumstances, the entire colony can leave the hive at a moment's notice and take off to find a new nest. This type of behavior is call absconding.
The European continent has cold winters. This environment favors those bees who can store food for long periods of time and survive in the hive having little activity. This strategy favors colony division as a method of migration.
On the other hand, scarcity of resources is a common occurrence in Africa. During hard times, one method of survival for the hive is to raid another hive. A second method is to move the entire colony to more favorable surroundings. Thus the honey bees in Africa that have been selected over the centuries are those that have the propensity to abscond and the ability to move long distances to find a new home. These bees are extremely protective of their hive and brood and are much more sensitive to hive disturbances. This protective behavior is the source of the tales of the "killer bee".
Absconding is the central strategy for migration for African honey bees. Because they use a hive for a shorter period of time, perhaps as short as six weeks, the honey bees of Africa are far less selective in their choice of hives and will settle on a much smaller space to build the hive. These traits persist in the hybrid European-African honey bee. These hybrid bees have spread through large parts of Central and South America because of their tendency to make frequent moves.
At the present time. we are witnessing this migration in Arizona. We can see that bees are moving quickly into places that are favorable for their survival - habitats that have sufficient water and pollen resources and are sufficiently warm. Their eventual habitat in Arizona and in other parts of the United States is now a topic of active research.