European honey bee
The European honey bee or Western honey bee (Apis mellifera) is a species of honey bee. The genus Apis is Latin for "bee", and mellifera comes from Latin melli- "honey" and ferre "to bear"—hence the scientific name means "honey-bearing bee". The name was coined in 1758 by Carolus Linnaeus who, realizing that the bees do not bear honey, but nectar, tried later to correct it to Apis mellifica ("honey-making bee") in a subsequent publication. However, according to the rules of synonymy in zoologica nomenclature, the older name has precedence. As of October 28, 2006, the Honey Bee Genome Sequencing Consortium fully sequenced and analyzed the genome of Apis mellifera.
In 2007 media attention focused on colony collapse disorder, a decline in European honey bee colonies in a minority of regions of North America.
The honey bee is native to the continents of Europe, Asia, and Africa. As of the early 1600s, the insect was introduced to North America, with subsequent introductions of other European subspecies two centuries later. Since then, they have spread throughout the Americas.
In the temperate zone, honey bees survive winter as a colony, and the queen begins egg laying in mid to late winter, to prepare for spring. This is most likely triggered by longer day length. She is the only fertile female, and deposits all the eggs from which the other bees are produced. Except for a brief mating period when she may make several flights to mate with drones, or if she leaves in later life with a swarm to establish a new colony, the queen rarely leaves the hive after the larvae have become full grown bees. The queen deposits each egg in a cell prepared by the worker bees. The egg hatches into a small larva which is fed by nurse bees (worker bees who maintain the interior of the colony). After about a week, the larva is sealed up in its cell by the nurse bees and begins the pupal stage. After another week, it will emerge an adult bee.
For the first ten days of their lives, the female worker bees clean the hive and feed the larvae. After this, they begin building comb cells. On days 16 through 20, a worker receives nectar and pollen from older workers and stores it. After the 20th day, a worker leaves the hive and spends the remainder of its life as a forager. The population of a healthy hive in mid-summer can average between 40,000 and 80,000 bees.
The larvae and pupae in a frame of honeycomb are referred to as frames of brood and are often sold (with adhering bees) by beekeepers to other beekeepers to start new beehives.
Both workers and queens are fed "royal jelly" during the first three days of the larval stage. Then workers are switched to a diet of pollen and nectar or diluted honey, while those intended for queens will continue to receive royal jelly. This causes the larva to develop to the pupa stage more quickly, while being also larger and fully developed sexually. Queen breeders consider good nutrition during the larval stage to be of critical importance to the quality of the queens raised, good genetics and sufficient number of matings also being factors. During the larval and pupal stages, various parasites can attack the pupa/larva and destroy or damage it.
Queens are not raised in the typical horizontal brood cells of the honeycomb. The typical queen cell is specially constructed to be much larger, and has a vertical orientation. However, should the workers sense that the old queen is weakening, they will produce emergency cells known as supersedure cells. These cells are made from a cell with an egg or very young larva. These cells protrude from the comb. As the queen finishes her larval feeding, and pupates, she moves into a head downward position, from which she will later chew her way out of the cell. At pupation the workers cap or seal the cell. Just prior to emerging from their cells, young queens can often be heard "piping." The purpose of this sound is not yet fully understood.
Worker bees are infertile females, but in some circumstances, generally only in times of severe stress or with the loss or injury or declining health of the queen, they may lay infertile eggs, and in some subspecies these eggs may actually be fertile. However, since the worker bees are 'imperfect' females (not fully sexually developed), they do not mate with drones. Any fertile eggs that they lay would be haploid, having only the genetic contribution of their mother, and in honey bees these haploid eggs will always develop into drones. Worker bees also secrete the wax used to build the hive, clean and maintain the hive, raise the young, guard the hive and forage for nectar and pollen.
In honey bees, the worker bees have a modified ovipositor called a stinger with which they can sting to defend the hive, but unlike other bees of any other genus (and even unlike the queens of their own species), the stinger is barbed. Contrary to popular belief, the bee will not always die soon after stinging: this is a misconception based on the fact that a bee will usually die after stinging a human or other mammal. The sting and associated venom sac are modified so as to pull free of the body once lodged (autotomy), and the sting apparatus has its own musculature and ganglion which allow it to keep delivering venom once detached. It is presumed that this complex apparatus, including the barbs on the sting, evolved specifically in response to predation by vertebrates, as the barbs do not function (and the sting apparatus does not detach) unless the sting is embedded in elastic material. Even then, the barbs do not always "catch", so a bee may occasionally pull the sting free and either fly off unharmed, or sting again.
Drone bees are the male bees of the colony. Since they do not have ovipositors, they also do not have stingers. Drone honey bees do not forage for nectar or pollen. In some species, drones are suspected of playing a contributing role in the temperature regulation of the hive. The primary purpose of a drone bee is to fertilize a new queen. Multiple drones will mate with any given queen in flight, and each drone will die immediately after mating; the process of insemination requires a lethally convulsive effort. Drone honey bees are haploid (having single, unpaired chromosomes) in their genetic structure and are descended only from their mother, the queen. They truly do not have a father. In essence, drones are the equivalent of flying gametes. In regions of temperate climate, the drones are generally expelled from the hive before winter and left to die of cold and starvation, since they are unable to forage or produce honey or take care of themselves.
The average lifespan of the queen in most subspecies is three to four years. However, there are reports that in the German/European Black Bee subspecies that was previously used for beekeeping, the queen was said to live up to 8 years. Because queens deplete their store of sperm, towards the end of their life they start laying more and more unfertilized eggs. Beekeepers therefore frequently change queens every year or every other year.
The lifespan of the workers varies drastically over the year in places with an extended winter. Workers born in the spring will work hard and live only a few weeks, whereas those born in the autumn will stay inside for several months as the colony hibernates.
Honey bee queens release pheromones to regulate hive activities, and worker bees also produce pheromones for various communications (below).
Bees produce honey by collecting nectar, which is a clear liquid consisting of nearly 80% water with complex sugars. The collecting bees store the nectar in a second stomach and return to the hive where worker bees remove the nectar. The worker bees digest the raw nectar for about 30 minutes using enzymes to break up the complex sugars into simpler ones. Raw honey is then spread out in empty honeycomb cells to dry, which reduces the water content to less than 20%. When nectar is being processed, honey bees create a draft through the hive by fanning with their wings. Once dried, the cells of the honeycomb are sealed (capped) with wax to preserve the honey.
When a hive detects smoke, many bees become remarkably non-aggressive; it is speculated that this is a defense mechanism. Wild colonies generally live in hollow trees, and when bees detect smoke it is presumed that they prepare to evacuate from a forest fire, carrying as much food reserve as they can. In order to do this, they will go to the nearest honey storage cells and gorge on honey. In this state they are quite docile since defense from predation is less important than saving as much food as possible.
The honey bee needs an internal body temperature of 35 °C (95 °F) to fly — which is also the temperature maintained within the cluster. The same temperature is required in the brood nest over a long period to develop the brood, and it is the optimal temperature for the creation of wax. The temperature on the periphery of the cluster varies with the outside air temperature and in the winter cluster, the internal temperature may be as low as 20–22 °C (68–72 °F).
Honey bees are able to forage over a 30 °C (54.0 °F) range of air temperature, largely because they have behavioural and physiological mechanisms for regulating the temperature of their flight muscles. From very low to very high air temperatures, the successive mechanisms are; shivering before flight and stopping flight for additional shivering, passive body temperature regulation in a comfort range that is a function of work effort, and finally, active heat dissipation by evaporative cooling from regurgitated honey sac contents. The body temperatures maintained differ depending on caste and expected foraging rewards.
The optimal air temperature for foraging is 22–25 °C (72–77 °F). During flight, the rather large flight muscles create heat, which must dissipate. The honey bee uses a form of evaporative cooling to release heat through its mouth. Under hot conditions, heat from the thorax is dissipated through the head; the bee regurgitates a droplet of hot internal fluid — a "honeycrop droplet" – which immediately cools the head temperature by 10 °C (18.0 °F).
Below 7–10 °C (45–50 °F) bees become immobile and above 38 °C (100 °F) bee activity slows. Honey bees can tolerate temperatures up to 50 °C (122 °F) for short periods.
Periodically, the colony determines that a new queen is needed. There are three general triggers.
- The colony becomes space-constrained because the hive is filled with honey, leaving little room for new eggs. This will trigger a swarm where the old queen will take about half the worker bees to found a new colony, leaving the new queen with the other half of worker bees to continue the old colony.
- The old queen begins to fail — this is thought to be recognized by a decrease in queen pheromones throughout the hive. This situation is called 'supersedure; at the end of the supersedure, the old queen is generally killed.
- The old queen dies suddenly — this situation is known as 'emergency supersedure'. The worker bees will find several eggs or larvae of the right age-range and attempt to develop them into queens. Emergency supersedure can generally be recognized because the new queen cells are built out from regular cells of the comb rather than hanging from the bottom of a frame.
Regardless of the trigger, the workers develop the larvae into queens by continuing to feed them royal jelly which triggers an extended development as a pupa.
When the virgin queen emerges, she is commonly thought to seek out other queen cells and sting the infant queens within. It is also thought that, should two queens emerge simultaneously, they will fight to the death. Recent studies, however, have indicated that as many as 10% of Apis mellifera colonies may maintain two queens. The mechanism by which this occurs is not yet known, but it has been reported to occur more frequently in some South African subspecies of Apis mellifera. Regardlessthe queen asserts her control over the worker bees through the release of a complex suite of pheromones called queen scent.
After several days of orientation within and around the hive, the young queen flies to a drone congregation point (a site near a clearing and generally about 30 feet (9.1 m) above the ground) where the drones from different hives tend to congregate in a swirling aerial mass. Drones detect the presence of a queen in their congregation area by her smell, and then find her by sight and mate with her in mid air (drones can be induced to mate with "dummy" queens if they have the queen pheromone applied). A queen will mate multiple times and may leave to mate several days in a row, weather permitting, until her spermatheca is full.
The queen lays all the eggs in a healthy colony. The number and pace of egg-laying is controlled by weather, availability of resources and the characteristics of the specific race of honey bee. Honey bee queens generally begin to slow egg-laying in the early fall and may even stop during the winter. Egg-laying will generally resume in late winter as soon as the days begin to get longer and peak in the spring. At the height of the season, the queen may lay over 2500 eggs per day – more than her own body mass.
The queen fertilizes each egg as it is being laid using stored sperm from the spermatheca but will occasionally leave an egg unfertilized. The unfertilized eggs have only half as many genes as the queen or worker eggs and develop into drones.
The European honey bee is the third insect, after the fruit fly and the mosquito, to have its genome mapped. According to the scientists who analysed its genetic code, the honey bee originated in Africa and spread to Europe in two ancient migrations. They have also discovered that the number of genes in the honey bees related to smell outnumber those for taste, and they have fewer genes for immunity than the fruit fly and the mosquito. The genome sequence revealed several groups of genes, particularly the genes related to circadian rhythms, were closer to vertebrates than other insects. Genes related to enzymes that control other genes were also vertebrate-like.
Honey bees use special pheromones, or chemical communication, for almost all behaviors of life. Such uses include (but are not limited to): mating, alarm, defense, orientation, kin and colony recognition, food production, and integration of colony activities. Pheromones are thus essential to honey bees for their survival.
Honey bees are an excellent animal to study with regard to behavior because they are abundant and familiar to most people. An animal that is disregarded every day has very specific behaviors that go unnoticed by the normal person. Karl von Frisch, who was awarded the Nobel Prize for physiology and medicine in 1973 for his study of honey bee communication, noticed that bees communicate through the language of dance. Honey bees are able to direct other bees to food sources through the round dance and the waggle dance. The round dance tells the other foragers that food is within 50 meters of the hive, but it does not provide much information regarding direction. The waggle dance, which may be vertical or horizontal, provides more detail about both the distance and the direction of the located food source. It is also hypothesized that the bees rely on their olfactory sense to help locate the food source once the foragers are given directions from the dances.
Another signal for communication is the shaking signal, also known as the jerking dance, vibration dance, or vibration signal. It is a modulatory communication signal because it appears to manipulate the overall arousal or activity of behaviors. The shaking signal is most common in worker communication, but it is also evident in reproductive swarming. A worker bee vibrates its body dorsoventrally while holding another honey bee with its front legs. Jacobus Biesmeijer examined the incidence of shaking signals in a forager’s life and the conditions that led to its performance to investigate why the shaking signal is used in communication for food sources. Biesmeijer found that the experienced foragers executed 92.1% of the observed shaking signals. He also observed that 64% of the shaking signals were executed by experienced foragers after they had discovered a food source. About 71% of the shaking signal sessions occurred after the first five foraging success within one day. Then other communication signals, such as the waggle dance, were performed more often after the first five successes. Biesmeijer proved that most shakers are foragers and that the shaking signal is most often executed by foraging bees over pre-foraging bees. Beismeijer concluded that the shaking signal presents the overall message of transfer work for various activities or activity levels. Sometimes the signal serves to increase activity, when bees shake inactive bees. At other times, the signal serves as an inhibitory mechanism such as the shaking signal at the end of the day. However, the shaking signal is preferentially directed towards inactive bees. All three types of communication between honey bees are effective in their jobs with regards to foraging and task managing.