Queens, queens, queens
The bee colony normally has a single reproductive female-the queen. She is specialized for the functions of egg laying and chemical production, especially "queen substance" pheromone. She does not work like the workers and, in fact, cannot survive without workers to care for her. Minimum colony size is one queen and 200 workers.
The queen alternates egg laying with resting behavior. This occurs 24 hours a day. During the winter months there is considerably less egg-laying activity. During the busy spring months, the queen alternates 10-15 minute periods of resting behavior followed by 5-10 minutes of egg-laying behavior. It has been estimated that a queen lays over 200,000 eggs in a year and many queens will produce half a million eggs in their normal two- to three-year life-span.
During resting, a retinue of 12 or more worker bees (right) attend to the queen. They feed her, groom her, remove her wastes and also receive her "queen substance" and other pheromones. The pheromones are shared with other workers in food transmission behavior.
Newly emerged queens are termed virgin queens. They receive less worker attention than mated queens. They are smaller in size since the ovaries in the abdomen remain largely undeveloped until after mating. The first activity of a newly emerged virgin queen is to eliminate any potential rival virgin queens. Then she prepares for mating, beginning orientation flights two to three days following emergence. The queen is ready to mate within a week. Mating flights will last several days during which time the queen will mate with 7 to 17 drones. If a queen does not mate within the first three weeks of emergence, her chance of successfully mating decreases. Once mated, she will not mate again in her lifetime.
Following mating, the queen, now called a mated queen, rapidly gains weight due to ovary development. She can begin to lay eggs in two to three days. Her capability to lay eggs increases rapidly. A healthy queen in a populous colony can produce 1500-2000 eggs in a single day under favorable circumstances.
Queens that do not mate or those that use up their stored sperm can only produce unfertilized (drone) eggs. Such queens are termed drone layers. Colonies with drone layers are doomed, since workers are needed in the colony and fertilized eggs are necessary to raise a replacement queen.
Since there is only a single female reproductive in a bee colony, there is a special procedure to replace her when it becomes necessary to do so. Replacement of a queen by another queen is a process termed supersedure. Replacement of the queen and production of another colony is another behavior called swarming. A third means of replacing a queen, emergency queen rearing, is necessary if the queen dies suddenly, is removed by a beekeeper or is somehow injured or lost from her colony.
Queen failure may lead to reduced egg laying but is apparently measured through chemical pheromone production. Worker bees become restless in as little as one hour after removal of their queen. Replacement behaviors can be observed within four hours. How can the bees tell they are queenless or they have a failing queen? It is not known precisely but apparently bees determine queen suitability by the queen's release of queen substance.
Each worker bee needs to receive a certain level of queen substance daily. This pheromone is distributed through food transmission behavior. If a queen is taken away, the level of this pheromone drops rapidly, though it is persistent. In the case of a failing queen, the queen produces insufficient amounts of queen substance, and therefore is fed back less of the pheromone by the bees of her retinue. This feedback system of queen pheromone distribution is vital for communication.
The first behavior change observable in queen replacement is the laying of a fertilized egg in a queen cup. Queen cups are special cuplike precursors of queen cells Figure 9-3). They are always present in a bee colony, though their numbers are greatest in the spring months. They are built at the lower margin of beeswax comb (lower margins of frames in a beekeeper's hive) and in spaces where the comb is damaged or left open as a walkway to the opposite side of the comb. Sometimes they are built on a piece of burr comb extended outward from the comb face.
Queen cups are oriented with the cell opening downward, unlike the horizontal six-sided worker and drone cells. The different orientation of a queen cell is an apparent stimulus for the bees to feed royal jelly to the larva. Queens can develop normally in a horizontal orientation (or workers in a vertical position) if experimentally reared outside a colony.
The queen herself places the fertilized egg in a queen cup. Worker bees can remove eggs (from queen cups or regular cells) but they are not known to transfer them. The same queen may return to the developing queen cell (Figure 9-4). (Arbitrarily, an occupied cell is called a queen cell versus queen cup when empty). By chewing on the side of the cell, the queen causes the workers to remove and kill the occupant (egg, larva or pupa) inside Figure 9-5). It is possible to observe queen rearing repeatedly aborted in a bee colony. Many more cells are started than are successfully completed. Why bees start and then stop raising queens and the extent of such behavior is not known.
The original mated queen (who started the process of queen replacement by laying eggs in queen cups) may be killed before or after emergence of a virgin queen Figure 9-6) in supersedure or she may depart with a proportion of the adult workers in a swarm before a virgin queen emerges.
Queen supersedure occurs more frequently than most beekeepers appreciate. The behavior of raising queens is more common than realized, because there is a level of unsuccessful queen replacement that occurs under normal circumstances. As a general rule, queen supersedure occurs during the summer or early fall months and involves the rearing of only a few queen cells. Additionally, supersedure queen cells are more frequently positioned on the face of the beeswax comb rather than its lower margin. These circumstances are not always the rule and predicting the eventual outcome of a colony rearing queen cells is very difficult.
Cause of supersedure
Queen supersedure results when a failing queen exists. If a colony, which is raising replacement queens, is reduced in size, the smaller colony often discontinues attempts to raise new queens. Since the bees and the queen determine whether the queen is healthy or failing by the level of production of queen pheromone, a queen may produce enough queen substance to supply a smaller colony, at least until the colony gets bigger again. Removing eggs does not lead to queen replacement behaviors.
Once a queen receives too little queen substance from her attendant workers, via food transmission behavior, she responds by laying fertilized eggs in a few queen cups. She does this over several days.
Workers in no way force her to do this, nor do they apparently transfer fertilized eggs she has produced into the empty queen cups. The queen herself initiates the behavior. If conditions change in the colony (fewer bees, better distribution of the chemicals, etc.) queen rearing may be aborted; if conditions do not change, replacement queens are reared.
Efficient versus inefficient queen supersedure
Supersedure is replacement of the old mated queen with a new queen. If the failing queen dies relatively early in the supersedure processbefore the new virgin queen emerges-it is termed inefficient supersedure. If she survives until the new queen emerges, sometimes leading to the two queens coexisting as a mother-daughter queen colony, then it is labelled efficient queen supersedure.
At some point in supersedure, worker bees apparently kill the old (failing) queen. They do this in a behavior called "balling." A large number of workers crowd (ball) around the queen and some attempt to sting her. She is either stung or crushed to death. The signal or signals for this behavior are not known. The longer the old queen survives, the greater the efficiency because there is less of an interruption or break in the brood cycle.
Since a supersedure colony rears more than one queen, there may be instances when two or more virgin queens emerge at about the same time. In such circumstances the virgin queens will fight and one eventually becomes the sole survivor. Some beekeepers believe killing of the old mated queen in efficient supersedure may also be via fighting between mother and daughter queens. More likely, the workers ball the old mated queen as the colony reduces in size in the fall and the new daughter queen becomes the sole colony queen. It is not precisely known.
The process of queen fighting is not well studied though it is often depicted in films and videos that feature honey bee biology. Worker bees sometimes confine virgin queens in their cells for a day or more.
This probably is not intended to protect them, however. The queens are fed inside their cells when this is done. Confinement often leads to production of a curious sound termed "piping". The more queen cells a colony has, the more likely piping will occur since queens often respond to the piping of another queen.
Swarming is natural colony reproduction. The behavior of swarming is complex. Biologists lack full understanding of several interrelated factors that are responsible for successful swarming in a bee colony It is a basic biology of bees, since division of the colony unit is essential for continued existence of the society.
L.L. Langstroth, the inventor of our modern hive, called swarming a "most beautiful sight." It means different things to different people. Honey bees in a swarm are gentle and can usually be handled with ease.
For beekeepers, swarms represent potential new colonies; at one time they were a welcome sight. Today most beekeepers practice swarm prevention and control. Capturing a swarm that emerged from a bee tree or a neighboring apiary is good management, but represents management failure if the swarm is from the beekeeper's hive.
The general public has little understanding of swarms and so a swarm may be a terrifying sight. The appearance of a swarm has been expressed in history as both a portent of good or bad news. Bees, such as the Africanized bees in South America, which swarm excessively, represent a stinging hazard to be avoided by the general public but a resource for rural subsistence farmers to start a bee hive or rob for their honey later in the season. Bee swarms have halted traffic, delayed a nationally telecast baseball game in Ohio and terrorized the U.S. in the book and movie "The Swarm." Although misunderstood, swarms are only temporary and not a threat, even in the defensive Africanized bee, if simply left alone.
There are many sounds we can hear in a bee hive, do bees hear them too? Bees lack ears or other sound-capturing structures but they do hear! Bees communicate with sounds both in queen rearing and in dance language communication.
In swarming and supersedure, "piping" is a high-pitched sound produced by queen muscle contractions without unfolding of the wings. The thorax vibrates faster with wings folded than when unfolded so the sound is not the usual bee "buzz" but a high pitched "piping" sound.
The queen, as she pipes, presses her thorax against the beeswax comb. Adult queens pipe on or close to the queen cell of developing queens.Worker bees pick up the sound, probably via vibrations, and may be observed to stop or freeze movements in the vicinity of queen piping. The adult queen pipes for a two-second pulse followed by a series of quarter-second toots. If there are virgin queens within queen cells, they respond with a series of ten short pulses.
Piping is more frequently heard in swarming than in supersedure behavior and is more commonly heard after the primary swarm leaves. We do not know what precise role it plays but it is believed piping may help time swarm departure, particularly for afterswarms. Also, it may help the virgin queen locate her potential rivals so she can eliminate them.
The ordinary buzzing sound made by bees when flying may or may not be perceived by bees. If we hold a worker bee in our fingers she too will make a high pitched sound somewhat similar to queen piping. Worker bees will also emit this sound in the hive-perhaps as a warning or alarm sound.
Sound production is vital in dance language communication behavior. Worker bees must precisely time the length of waggling since it encodes the distance to food source portion of the message. The unique noise of the "breaking" dance, signaling swarm departure, may also be a sound the bees can hear.
The perception of substrate "noise" may be via touch receptors rather than airborne sound wave perception. Beekeepers know that jolts and vibrations to the hive serve to alert a bee colony and may result in more stings during colony inspections. The ordinary background hum of bees may likewise be a touch stimulus transmitted through the beeswax comb.
Swarming begins when the mated queen lays fertilized eggs in queen cups leading to developing queen cells. Such behavior is natural for a queen receiving too little queen substance. A few days later, shortly before emergence of a new virgin queen, the old mated queen (with a proportion of the adult worker population) leaves the parent colony and clusters nearby. The leaving is swarming and the cluster is termed a swarm. Scout bees from the swarm find a new home. Once a suitable location has been identified, the bees that swarmed move en masse from the temporary swarm cluster location into a new cavity and establish a new nest.
The parent colony may then yield additional swarms (afterswarms) containing one or more virgin queens and a further proportion of the remaining adult worker population. Eventually the parent colony stops swarming, one virgin queen becomes the monarch and, after she mates, the original colony returns to a normal existence. The issuing swarm contains 41-80% of the adult workers of the original hive (average 66%). The first swarm to leave (primary swarm) usually contains only the old mated queen but it may contain virgin queens if weather conditions have delayed swarm departure. Afterswarms often contain several virgin queens and are smaller in size. Swarms as small as 2,400 bees to as large as 4 1,000 individuals have been reported. Mean populations were 11,800 bees in one study and calculated at 14,000 bees in another.
Events leading to swarming
Swarming is not a random happenstance. It is not known exactly what the clues may be that initiate swarming behavior but it is possible to observe and measure some of the events.
Swarming preparations begin when the queen lays fertilized eggs in the vertically oriented queen cups. Queen cups are constructed, often in great numbers, by the bees as colonies expand in the spring. If queen cups are experimentally removed, bees replace them more quickly during the spring than at other times of the year. Queen cups, by themselves, are not a sign of swarm preparations. Likewise, colonies in the spring rear drones. Raising of drones, like building of queen cups, is a function of season (photoperiod and abundant resources)-the same conditions permit expansion of brood rearing and raising of queens by colonies.
The first outward sign of swarming behavior the beekeeper usually observes is the development of queen cells. Usually the queen selects a number of queen cups and lays eggs over more than one day. Often she selects queen cups at the bottom margin of the comb, although she can use a cup at any location. As in supersedure, the same egg-laying queen can return later to these queen cells at any stage to halt the development progress. Worker bees do not "force" the queen to lay eggs in cups nor do they later protect them from her destruction.
As queen cells develop, it is possible to observe several events in preparation for swarming. The queen begins to lose weight because the workers reduce her feeding or she accepts less food. A queen will lose about one-third her body weight before departing in the swarm. Since a queen is normally very heavy with eggs, most of the weight loss occurs in the abdomen. Workers begin to treat the queen more roughly, including the behavior of vibrating the queen. The queen continues egg-laying behavior but at a reduced rate during these preparations.
Worker bees meanwhile are gaining weight because they tend to engorge with honey when preparing to swarm. This behavior occurs up to 10 days before the swarm issues. Engorgement helps insure a food reserve for the swarm in transit to a new home since there is little foraging by the bees of a swarm. As swarming day comes closer, scout bees leave the parent colony to begin seeking a new nest site.
There is a definite seasonality to swarming. The vast majority of colonies swarm within a six-week period of time in mid-spring. Swarms usually emerge in the middle of the day (10 a.m. to 2 p.m.) on days suitable for bee flight. The process of leaving the original hive is rapid, lasting 10-15 minutes at most. Prior to emergence, bees become quiet in the hive and foraging is reduced. The signal to leave may be the whirring or breaking dance. A few bees perform this agitated zigzag running among the bees in the hive, producing a whirring sound with the wings. The behavior is imitated by other bees. The queen may be pushed toward the entrance by other worker bees.
There is no apparent determination of which bees will go with the swarm versus those that will stay. Bees of all ages join a swarm but the majority are younger (4-23 days old) bees. The bees that leave the hive in swarming rush out of the parent hive, fly in a circular flight motion and then move off a short distance to cluster on a bush, shrub or other convenient location. Most swarms settle within three meters (ten feet) of the ground but some land on the ground while others cluster at higher locations.
Drones join the swarm (average 50/swarm) but, unlike the workers, do not engorge on food reserves before emergence. During swarm issuance, bees from other colonies may join the swarm, particularly bees from queenless hives. Although many bees engorge in the parent hive in preparation to swarm, all do not leave. By re-hiving the bees that swarm (after marking a proportion of the population) and permitting them to swarm again, it will be evident that the same bee may or may not go again, suggesting a random division of the adult population at the time of swarm emergence.
Cause of swarming
There have been many attempts to determine the cause of swarming. Some proximate events have been correlated with the behavior but the ultimate factor or factors are not completely known. Strong, healthy colonies swarm. Timing of swarming is influenced by weather, photoperiod, genetics, age of the queen, queen pheromones (and their distribution), physical crowding and perhaps additional factors.
As is the case with queen supersedure, swarming is strongly influenced by insufficient queen substance. Colonies with young queens are much less likely to swarm than colonies headed by queens more than 12 months old. The ability of a queen to produce queen substance varies with age as well as genetic factors, the conditions under which they were reared and, perhaps, other things. A combination of congestion and queen pheromone insufficiency seems to explain the causal factors of swarming. Queen substance deficiency induces swarming in large colonies that are congested with young bees. The queen may not be deficient but rather congestion causes less efficient distribution of the pheromone. Thus, in the feedback mechanism of queen substance, the queen receives an insufficient amount. She then initiates queen rearing by laying eggs in queen cups.
Full-sized colonies that have a queen producing an adequate level of queen substance do not swarm. Their level of congestion is such that the distribution of the pheromone is not inhibited.
Post-emergence behavior of swarms
Upon exiting the original nest site, swarms move en masse to a temporary cluster site (usually near the parent colony) before movement to the eventual home site. The mass of bees in flight may extend 15-30 m (50-100 feet) in diameter and 2-6 m (6-20 feet) high. The interaction of queen pheromone 9 ODA and worker scent gland is important in retaining the cohesiveness of the flying mass of bees. Individual bees fly in a circular pattern within the swarm. The queen does not lead a swarm but there must be a queen present for the swarm cluster to remain.
After clustering, the bees remain within the swarm itself. The only flight activity is that of scout bees which leave the swarm cluster (exiting from one principle area) to seek a suitable nesting cavity When the scouts return to the cluster, they indicate the location of their find by dancing on the surface of the clustered swarm. They are the only bees active in the swarm; the rest of the bees remain stabilized by queen pheromone. The cluster is organized as a sphere with an outer shell two to three bees thick (older bees generally) while inside there are chains of younger bees. The inside temperature remains in the optimum brood rearing range of 93° F (around 34° C) while the outside temperature fluctuates with that of the environment.
The swarm cluster may remain at the temporary site a few hours or a few days. The swarm moves when all (or nearly all) scout bees are indicating (via dance language) the same site, which generally is not too distant. The whirring or breaking dance stimulates the bees to fly once again. Scout bees apparently guide the flight by odor release.
In rare instances the bees are unable to find a suitable cavity or the scout bees are unable to agree on one single location. The bees stay as a swarm cluster for a longer time period and may consume much of the food reserves in the honey stomachs. These swarms can be defensive if disturbed and might not behave like the typical gentle swarm. A colony's defense of its nest site may be related to a reduction in food reserves but it is more likely that the bees begin to identify with the location and defend the temporary cluster site as they would their hive. Bees in swarms that remain clustered, for more than a day, begin wax secretion and comb construction at the temporary cluster spot.
After settling in a new home site, beeswax comb is quickly constructed. The queen rapidly regains her body weight and begins egg laying. Additional comb must be constructed, brood must be raised and sufficient food must be stored to survive the winter. Survival of such nests established from swarms is less than 25% in the wild but if a colony survives the first winter season, it has a life expectancy of more than five years. In contrast, beekeeper-managed colonies last indefinitely if problems in queen replacement are detected and properly handled. Beekeeper hived swarms properly managed should survive the winter without problems.
Swarms can be created by caging a queen and forcing workers to cluster around her. This is routinely used in teaching situations to demonstrate swarm capture. It is also the technique used at bee meetings for the demonstration of bee beards.
To make a bee beard a queen cage with living queen is tied beneath the chin and bees are forced to cluster around the cage, forming a beard on the face of a person. It is necessary that the worker bees around the queen cage be well engorged with ample sugar syrup before the demonstration is performed to reduce chances of being stung and to reduce flight activity. The sensation of living bees crawling and settling on the body is very unique and only confirmed "bee-ophilics" should attempt this activity.
The same technique is used to create artificial swarms (on wooden crosses, for example). Knowledge of bee communication by pheromones, swarm stabilization behavior, bee recognition of their own individual queen and other secrets of bee biology have come from this technique. It is an interesting experience to remove the queen cage from a clustered swarm and hold it as the bees move from the former location to cluster around their queen in a few short minutes. Many interesting bee behaviors can be studied with artificial swarms.
Under some circumstances, a bee colony may abscond. In absconding, all or most of the adult population leaves or abandons their nest site. The bees cluster like a swarm and scout bees seek a new home site. European race honey bees seem to abscond infrequently whereas the African races (including the Africanized bee in South America) abscond more readily. Absconding may be a relic of migratory movement, which is more common in Africa.
Abandonment of the hive in the fall has been termed "hunger swarming" though it may not always be related to lack of food. In hunger swarming, a large proportion of the bees may depart the parent colony, leaving it unable to continue to function normally. Absconding is seen in colonies that have no brood or developing queen cells, are very small in population, have an unsatisfactory nest site, are disturbed with continued smoking or dripping water, and after exposure to certain noxious chemicals. There undoubtedly are other factors that may cause a colony to abscond.
Emergency queen rearing
A queen may be lost or killed in various ways but she is injured or killed most frequently by the beekeeper. The action is usually unintentional. Beekeepers may on occasion remove a queen from a colony to replace the existing queen. Worker bees notice the sudden absence of a queen and they quickly begin preparations to raise a new queen. No worker can change into a queen - the bees must raise a new queen.
The workers begin to enlarge a few cells containing day-old and two-day-old worker larvae within four hours of the disappearance of the old queen. The number of new queens the bees will rear is highly variable and depends upon many factors. The workers always begin to rear several new queens rather than a single one. The workers start more queen cells than they eventually rear to the adult stage but the criteria used to eventually select the successful ones to be raised to the adult stage are unknown.
Emergency queen cells (right) can be distinguished from the queen cells of swarming or supersedure because they originate from a worker cell. The horizontal orientation of the worker cells, selected for conversion to queens, is quickly changed to the vertical by enlarging the base of the cell and drawing the opening outward and downward. This usually means destroying the cell walls and removing the larvae of three to four cells adjacent to the modified cell.
Thereafter, the newly modified cell is expanded downward like a regular queen cell. The bees feed royal jelly to the developing larvae exactly as when they rear a queen in supersedure or swarming. At the proper time, the cell is capped. Capped emergency cells often seem smaller than capped queen cells started from queen cups.
Upon emergence of virgin queens, there is the behavior of elimination of surplus queens. The end result is one single virgin queen after about a 24-hour period of fighting, elimination of queens, balling, etc. The virgin queen then prepares to mate and begin her new life as the mated queen of the colony. The entire process of rearing an emergency virgin queen takes a minimum of two weeks.
If the emergency rearing of a replacement queen is not successful, the workers are left hopelessly queenless for they now lack fertilized eggs or larvae less than two days of age to again attempt emergency queen rearing. The workers age and the colony will perish unless a beekeeper intervenes and supplies a frame of worker brood (with at least some eggs and young larvae) from another colony, or the colony is requeened.
A certain percentage of beekeeper-managed colonies become queenless each year. Should this occur when there are no eggs or young worker larvae present, the colony is hopelessly queenless unless the beekeeper intervenes. During the active season, queenless; colonies may result from unsuccessful queen replacement. Perhaps in fighting, all the queens were killed. Also mating, which occurs first in the life of the virgin queen, is not without it's hazards and queens can die, get lost, get eaten, etc., while attempting to mate.
Colonies that are hopelessly queenless develop laying workers. Laying workers are worker bees that lay eggs. Normally the worker ovaries are not developed. However, without a queen and her pheromones, plus the absence of inhibition from the presence of worker brood pheromone, worker ovaries begin to develop. After a few weeks, 10% or so of the workers are capable of producing eggs in four to eight ovarioles that develop in their ovaries. These workers cannot mate, so all the eggs they produce are unfertilized and hence develop into males.
Laying-worker colonies, like colonies headed by drone layer queens, have no future. As the workers age and die, there are no replacements, since unfertilized eggs yield drones. The beekeeper can distinguish between laying workers or a drone layer by examining the cells containing eggs. Drone layers are queens so the usual situation of one egg neatly arranged in the bottom of the cell will be evident. Cells with eggs of laying workers are not so regular. The workers often put several eggs, even up to a dozen, in one cell and the eggs are often at odd angles and locations.
Larvae from unfertilized eggs appear normal in worker cells but drone pupae will be identifiably different. Drones reared in worker cells are often smaller-bodied.
Gary, N.E. 1992.Activities and behavior of honey bees. In The hive and the honey bee. Dadant & Sons, Inc. Hamilton, IL. Chapter 8.
Laidlaw, H. H. 198 1. Queen introduction. Bee World 62(3): 98- 105.
Root, A. I. Co. 1996. Queen management. A. I. Root Co. Medina, OH. 49 pp.
Winston, Mark. 1992.The biology of the honey bee. Harvard Univ. Press, Cambridge, MA. 281 pp.
This page is broadly based on chapter 9 of the book Bees and beekeeping by Dr. Dewey M. Caron (In Press).