The western honey bee or European honey bee ( Apis mellifera) is the most common of the 7–12 species of worldwide. The genus name Apis is Latin for 'bee', and mellifera is the Latin for 'honey-bearing' or 'honey-carrying', referring to the species' production of honey.
Like all honey bee species, the western honey bee is Eusociality, creating Beehive with a single fertile female (or "Queen bee"), many normally non-reproductive females or "workers", and a small proportion of fertile males or "drones". Individual colonies can house tens of thousands of bees. Colony activities are organized by complex communication between individuals, through both and the dance language.
The western honey bee was one of the first Domestication insects, and it is the primary species maintained by beekeepers to this day for both its honey production and pollination activities. With human assistance, the western honey bee now occupies every continent except Antarctica. Western honey bees are threatened by pests and diseases, especially the Varroa mite and colony collapse disorder. There are indications that the species is rare, if not extinct in the wild in Europe and as of 2014, the western honey bee was assessed as "Data Deficient" on the IUCN Red List. Numerous studies indicate that the species has undergone significant declines in Europe; however, it is not clear if they refer to population reduction of wild or managed colonies. Further research is required to enable differentiation between wild and non-wild colonies in order to determine the conservation status of the species in the wild, meaning self sustaining, without treatments or management.
Western honey bees are an important model organism in scientific studies, particularly in the fields of Sociobiology, learning, and memory; they are also used in studies of pesticide toxicity, especially via pollen, to assess non-target impacts of commercial pesticides.
Previously it was believed that the various subspecies were all cross-fertile, but in 2013 it was found that the A. m. mellifera queens do not mate with non- A. m. mellifera drones.
The subspecies are divided into four major branches, based on work by Ruttner and confirmed by mitochondrial DNA analysis. African subspecies belong to branch A, northwestern European subspecies branch M, southwestern European subspecies branch C and Middle Eastern subspecies branch O.
In most climates, western honey bees swarm in the spring and early summer, when there is an abundance of blooming flowers from which to collect nectar and pollen. In response to these favorable conditions, the hive creates one to two dozen new queens. Just as the stages of these "daughter queens" are nearly complete, the old queen and approximately two-thirds of the adult workers leave the colony in a swarm, traveling some distance to find a new location suitable for building a hive (e.g., a hollow tree trunk). In the old colony, the daughter queens often start "piping", just prior to emerging as adults, and, when the daughter queens eventually emerge, they fight each other until only one remains; the survivor then becomes the new queen. If one of the sisters emerges before the others, she may kill her siblings while they are still pupae, before they have a chance to emerge as adults.
Once she has dispatched all of her rivals, the new queen, the only fertile female, lays all the eggs for the old colony, which her mother has left. Virgin females are able to lay eggs, which develop into males (a trait found in bees, wasps, and ants because of haplodiploidy). However, she requires a mate to produce female offspring, which comprise 90% or more of bees in the colony at any given time. Thus, the new queen goes on one or more , each time mating with 1–17 drones. Once she has finished mating, usually within two weeks of emerging, she remains in the hive, playing the primary role of laying eggs.
Throughout the rest of the growing season, the colony produces many workers, who gather pollen and nectar as cold-season food; the average population of a healthy hive in midsummer may be as high as 40,000 to 80,000 bees. Nectar from flowers is processed by , who evaporate it until the moisture content is low enough to discourage mold, transforming it into honey, which can then be capped over with Beeswax and stored almost indefinitely. In the temperate climates to which western honey bees are adapted, the bees gather in their hive and wait out the cold season, during which the queen may stop laying. During this time, activity is slow, and the colony consumes its stores of honey used for metabolic heat production in the cold season. In mid- through late winter, the queen starts laying again. This is probably triggered by day length. Depending on the subspecies, new queens (and swarms) may be produced every year, or less frequently, depending on local environmental conditions and a number of characteristics inside the hive.
Worker bees secrete the Beeswax used to build the hive, clean, maintain and guard it, raise the young and forage for nectar and pollen; the nature of the worker's role varies with age. For the first 10 days of their lives, worker bees clean the hive and feed the larvae. After this, they begin building comb cells. On days 16 through 20, workers receive nectar and pollen from older workers and store it. After the 20th day, a worker leaves the hive and spends the remainder of its life as a forager. Although worker bees are usually infertile females, when some subspecies are stressed they may lay fertile eggs. Since workers are not fully sexually developed, they do not mate with drones and thus can only produce haploid (male) offspring.
Queens and workers have a modified ovipositor called a stinger, with which they defend the hive. Unlike those of bees of any other genus and of the queens of their own species, the stinger of worker western honey bees is barbed. Contrary to popular belief, a bee does not always die soon after stinging; this misconception is based on the fact that a bee will usually die after stinging a human or other mammal. The stinger and its venom sac, with musculature and a ganglion allowing them to continue delivering venom after they are detached, are designed to Autotomy when they lodge. This apparatus (including barbs on the stinger) is thought to have evolved in response to predation by vertebrates, since the barbs do not function (and the stinger apparatus does not detach) unless the stinger is embedded in elastic material. The barbs do not always "catch", so a bee may occasionally pull its stinger free and fly off unharmed (or sting again).
Although the Life expectancy of a queen in most subspecies is three to five years, reports from the German honey bee subspecies ( A. m. mellifera) previously used for beekeeping indicate that a queen can live up to eight years. Because a queen's store of sperm is depleted near the end of her life, she begins laying more unfertilized eggs; for this reason, beekeepers often replace queens every year or two.
The lifespan of workers varies considerably over the year in regions with long winters. Workers born in spring and summer work hard, and live only a few weeks, but those born in autumn remain inside for several months as the colony clusters. On average during the year, about 1% of a colony's worker bees die naturally per day.Tautz, J. Phaenomen Honigbiene Springer 2003, 280 pages, pg 47 Except for the queen, all of a colony's workers are replaced about every four months.
Periodically, the colony determines that a new queen is needed. There are three general causes:
Emergency supersedure can generally be recognized because new queen cells are built out from comb cells, instead of hanging from the bottom of a frame. Regardless of the trigger, workers develop existing larvae into queens by continuing to feed them royal jelly, rather than switching them to bee bread, and by extending the selected larvae's cells to house the developing larger-bodied queens.
Queens are not raised in the typical horizontal brood cells of the honeycomb. A queen cell is larger and oriented vertically. If workers sense that an old queen is weakening, they produce emergency cells (known as supersedure cells) from cells with eggs or young larvae and which protrude from the comb. When the queen finishes her larval feeding and pupates, she moves into a head-downward position and later chews her way out of the cell. At pupation, workers cap (seal) the cell. The queen asserts control over the worker bees by releasing a complex suite of pheromones, known as queen scent.
After several days of orientation in and around the hive, the young queen flies to a drone congregation area – a site near a clearing and generally about above the ground – where drones from different hives congregate. They detect the presence of a queen in their congregation area by her smell, find her by sight and mate with her in midair; drones can be induced to mate with "dummy" queens with the queen pheromone. 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, resource availability and specific racial characteristics. Queens generally begin to slow egg-laying in the early fall, and may stop during the winter. Egg-laying generally resumes in late winter when the days lengthen, peaking in the spring. At the height of the season, the queen may lay over 2,500 eggs per day (more than her body mass).
She fertilizes each egg (with stored sperm from the spermatheca) as it is laid in a worker-sized cell. Eggs laid in drone-sized (larger) cells are left unfertilized; these unfertilized eggs, with half as many genes as queen or worker eggs, develop into drones.
Another form of worker policing is aggression toward fertile females. Some studies suggest a queen pheromone which may help workers distinguish worker-laid and queen-laid eggs, but others indicate egg viability as the key factor in eliciting the behavior.
Worker policing is an example of Coercion, where the benefits of worker reproduction are minimized and that of rearing the queen's offspring maximized.
In very rare instances, workers subvert the policing mechanisms of the hive, laying eggs faster than other workers remove them; this is known as anarchic syndrome. Anarchic workers can activate their ovaries at a higher rate and contribute a greater proportion of males to the hive. Although an increase in the number of drones decreases the overall productivity of the hive, it increases the reproductive fitness of the drones' mother. Anarchic syndrome is an example of selection working in opposite directions at the individual and group levels for the stability of the hive.
Under ordinary circumstances, if the queen dies or is removed, reproduction in workers increases because a significant proportion of workers then have activated ovaries. The workers produce a last batch of drones before the hive collapses. Although during this period worker policing is usually absent, in certain groups of bees it continues.
According to the strategy of kin selection, worker policing is not favored if a queen mates just once. In that case, workers are related by three-quarters of their genes, and the sons of workers are related more than usual to sons of the queen. Then the benefit of policing is negated. Experiments confirming this hypothesis have shown a correlation between higher mating rates and increased rates of worker policing in many species of social hymenoptera.Davies, N.R., Krebs, J.R., and West, S.A. An Introduction to Behavioral Ecology. 4th ed. West Sussex: Wiley-Blackwell, 2012. Print. pp. 387–388
Western honey bees can forage over a air-temperature range because of behavioral and physiological mechanisms for regulating the temperature of their flight muscles. From low to high air temperatures, the mechanisms are: shivering before flight and stopping flight for additional shivering, passive body-temperature regulation based on work, and evaporative cooling from regurgitated honey-sac contents. Body temperatures differ, depending on caste and expected foraging rewards.
The optimal air temperature for foraging is . During flight, the bee's relatively large flight muscles create heat which must be dissipated. The honey bee uses 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 warm internal fluid — a "honeycrop droplet" – which reduces the temperature of its head by .
Below bees are immobile, and above their activity slows. Western honey bees can tolerate temperatures up to for short periods.
They lack the thermal defense exhibited by Apis cerana, but at least one subspecies, Apis mellifera cypria, is capable of killing invading through asphyxiation, despite not being able to attain lethal temperatures.Alexandros Papachristoforou, Agnès Rortais, Georgia Zafeiridou, George Theophilidis, Lionel Garnery, Andreas Thrasyvoulou, Gérard Arnold (2007) Smothered to death: Hornets asphyxiated by honeybees. Current Biology 17(18): R795-R796. DOI:10.1016/j.cub.2007.07.033
Western honey bees also change the precision of the waggle dance to indicate the type of site that is set as a new goal. Their close relatives, Apis florea, do not. Therefore, western honey bees seem to have evolved a better means of conveying information than their common ancestors with the dwarf honey bee.
Another means of communication is the shaking signal, also known as the jerking dance, vibration dance or vibration signal. Although the shaking signal is most common in worker communication, it also appears in reproductive swarming. A worker bee vibrates its body dorsoventrally while holding another bee with its front legs. Jacobus Biesmeijer, who examined shaking signals in a forager's life and the conditions leading to its performance, found that experienced foragers executed 92% of observed shaking signals and 64% of these signals were made after the discovery of a food source. About 71% of shaking signals occurred before the first five successful foraging flights of the day; other communication signals, such as the waggle dance, were performed more often after the first five successes. Biesmeijer demonstrated that most shakers are foragers and the shaking signal is most often executed by foraging bees on pre-foraging bees, concluding that it is a transfer message for several activities (or activity levels). Sometimes the signal increases activity, as when active bees shake inactive ones. At other times, such as the end of the day, the signal is an inhibitory mechanism. However, the shaking signal is preferentially directed towards inactive bees. All three forms of communication among honey bees are effective in foraging and task management.
The alarm pheromone has shown to be attractive small hive beetle. Therefore, there is a tradeoff between recruiting guards bees to defend the invaders and attract more beetles. Small hive beetle has a lower sensing threshold for the honeybee pheromone, which exacerbates the damage to honeybee hive.
have selected western honey bees for several desirable features:
These modifications, along with artificial change of location, have improved western honey bees from the point of view of the beekeeper, and simultaneously made them more dependent on beekeepers for their survival. In Europe, cold weather survival was likely selected for, consciously or not, while in Africa, selection probably favoured the ability to survive heat, drought, and heavy rain.
Authors do not agree on whether this degree of artificial selection constitutes genuine domestication. In 1603, John Guillim wrote "The Bee I may well reckon a domestic insect, being so pliable to the benefit of the keeper." More recently, many biologists working on pollination take the domesticated status of western honey bees for granted. For example, Rachael Winfree and colleagues write "We used crop pollination as a model system, and investigated whether the loss of a domesticated pollinator (the honey bee) could be compensated for by native, wild bee species." Similarly, Brian Dennis and William Kemp write: "Although the domestication of the honey bee is closely connected to the evolution of food-based socio-economic systems in many cultures throughout the world, in current economic terms, and in the U.S. alone, the estimated wholesale value of honey, more than $317 million dollars in 2013, pales in comparison to aggregate estimated annual value of pollination services, variously valued at $11–15 billion."
On the other hand, P. R. Oxley and B. P. Oldroyd (2010) consider the domestication of western honey bees, at best, partial. Oldroyd observes that the lack of full domestication is somewhat surprising, given that people have kept bees for at least 7,000 years. Instead, beekeepers have found ways to manage bees using hives, while the bees remain "largely unchanged from their wild cousins".
Leslie Bailey and B. V. Ball, in their book Honey Bee Pathology, call western honey bees "feral insects", in contrast to the Bombyx mori ( Bombyx mori) which they call "the only insect that has been domesticated", and refer to the "popular belief among many biologists as well as beekeepers that bees are domesticated". They argue that western honey bees are able to survive without human help, and in fact require to "be left at liberty" to survive. Further, they argue that even if bees could be raised away from the wild, they would still have to fly freely to gather nectar and pollinate plants. Therefore, they argue, beekeeping is "the exploitation of colonies of a wild insect", with little more than the provision of a weatherproof cavity for them to nest in. Likewise, Pilar de la Rua and colleagues argue that western honey bees are not fully domesticated, because "endemic subspecies-specific genetic footprints can still be identified in Europe and Africa", making conservation of wild bee diversity important. Further, they argue that the difficulty of controlling drones for mating is a serious handicap and a sign that domestication is not complete, in particular as "extensive gene flow usually occurs between wild/feral and managed honeybee populations".
Western honey bees collect flower nectar and convert it to honey, which is stored in the hive. The nectar, transported in the bees' stomachs, is converted with the addition of and storage in a honey cell for partial dehydration. Nectar and honey provide the energy for the bees' flight muscles and for heating the hive during the winter. Western honey bees also collect pollen which, after being processed to Bee pollen, supplies protein and fat for the bee brood to grow. Centuries of selective breeding by humans have created western honey bees which produce far more honey than the colony needs, and beekeepers (also known as apiarists) harvest the surplus honey.
Beekeepers provide a place for the colony to live and store honey. There are seven basic types of beehive: skeps, , top-bar hives, box hives, log gums, D. E. hives, and miller hives. All U.S. states require beekeepers to use movable frames to allow bee inspectors to check the brood for disease. This allows beekeepers to keep Langstroth, top-bar and D.E. hives without special permission, granted for purposes such as museum use. Modern hives also enable beekeepers to transport bees, moving from field to field as crops require pollinating (a source of income for beekeepers).
In cold climates, some beekeepers have kept colonies alive (with varying degrees of success) by moving them indoors for winter. While this can protect the colonies from extremes of temperature and make winter care and feeding more convenient for the beekeeper, it increases the risk of dysentery and causes an excessive buildup of carbon dioxide from the bees' respiration. Inside wintering has been refined by Canadian beekeepers, who use large barns solely for the wintering of bees; automated ventilation systems assist in carbon dioxide dispersal.
In California, almond pollination occurs in February, early in the growing season before local hives have built up their populations. Almond require two hives per acre, or per hive, for maximum yield, and pollination is dependent on the importation of hives from warmer climates. Almond pollination (in February and March in the U.S.) is the largest managed pollination event in the world, requiring more than one-third of all managed honey bees in the country. Bees are also moved en masse for pollination of apples in New York, Michigan, and Washington. Despite honey bees' inefficiency as blueberry pollinators, large numbers are moved to Maine because they are the only pollinators who can be easily moved and concentrated for this and other monoculture crops. Bees and other insects maintain flower constancy by transferring pollen to other biologically specific plants;
Bees produce honey by collecting nectar, a clear liquid consisting of nearly 80 percent water and 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 digestive enzymes to break down the complex sugars into simpler ones. Raw honey is then spread in empty honeycomb cells to dry, reducing its water content to less than 20 percent. When nectar is being processed, honey bees create a draft through the hive by fanning with their Insect wing. When the honey has dried, the honeycomb cells are sealed (capped) with wax to preserve it.
As of October 28, 2006, the Honey Bee Genome Sequencing Consortium fully sequenced and analyzed the genome of Apis mellifera, the western honey bee. Since 2007, attention has been devoted to colony collapse disorder, a decline in western honey bee colonies in a number of regions.
The western honey bee is the third insect, after the fruit fly and the mosquito, whose genome has been mapped. According to scientists who analyzed its genetic code, the honey bee originated in Africa and spread to Europe in two ancient migrations. Scientists have found that related to smell outnumber those for taste, and the European honey bee has fewer genes regulating immunity than the fruit fly and the mosquito. The genome sequence also revealed that several groups of genes, particularly those related to circadian rhythm, resembled those of vertebrates more than other insects. Another significant finding from the honey bee genome study was that the western honey bee was the first insect to be discovered with a functional DNA methylation system since functional key enzymes (DNA methyltransferase-1 and -3) were identified in the genome. DNA methylation is one of the important mechanisms in epigenetics to study gene expression and Gene regulation without changing the DNA sequence, but modifications on DNA activity. DNA methylation later was identified to play an important role in gene regulation and gene splicing. The genome is unusual in having few transposable elements, although they were present in the evolutionary past (remains and fossils have been found) and evolved more slowly than those in fly species.
Since 2018 a new version of the honey bee genome is available on NCBI (Amel_HAv3.1, BioProject ID: PRJNA471592). This assembly contains full chromosome length scaffolds, which means that the sequence data for each chromosome is contiguous, and not split between multiple pieces called scaffolds. The existence of a highly contiguous reference genome for a species enables more detailed investigations of evolutionary processes that affect the genome as well as more accurate estimations of for example differentiation between populations and diversity within populations.
An important process that shapes the honey bee genome is meiotic recombination, the rate of which is strongly elevated in honey bees and other social insects of the Hymenoptera order compared to most other eukaryotic species except Fungus and protozoa. The reason for elevated recombination rates in social Hymenoptera is not fully understood, but one theory is that it is related to their social behaviour. The increased genetic diversity resulting from high recombination rates could make the workers less vulnerable to parasites and facilitate their specialisations to different tasks in the colony.
Arachnid predators of western honey bees include , , Misumena and St. Andrew's cross spiders.
Reptile and amphibian predators of western honey bees include the Cordylus niger, Dactyloidae, and other lizards, and various anuran including the American toad, the American bullfrog and the wood frog.
Specialist bird predators of western honey bees include the ; other birds that may take western honey bees include , , tyrant flycatchers and the summer tanager. Most birds that eat bees do so opportunistically; however, summer tanagers will sit on a limb and catch dozens of bees from the hive entrance as they emerge.
Mammals that sometimes take western honey bees include
Honey bees are not native to the Americas, arriving with colonists in North America in the 18th century. Thomas Jefferson mentioned this in his Notes on the State of Virginia:
Sources may claim that honey bees (Apis mellifera) have become an invasive species in the United States, outcompeting native pollinators for food. However, while the USDA lists Africanized honeybees (Apis mellifera scutellata) as an invasive species, it does not classify western honey bees as invasive.
With an increased number of honey bees in a specific area due to beekeeping, domesticated bees and native wild bees often have to compete for the limited habitat and food sources available. Western honey bees may become defensive in response to the seasonal arrival of competition from other colonies, particularly Africanized bees which may be on the offence and defence year round due to their tropical origin. In the United Kingdom, honey bees are known to compete with native such as Bombus hortorum, because they forage at the same sites. To resolve the issue and maximize both their total consumption during foraging, bumblebees forage early in the morning, while honey bees forage during the afternoon.
A 2017 systematic review looked at the impacts of managed bees on wild bee populations. In addition to honey bees, this includes bumble bees and some solitary bees. The analysis looked at resource competition and changes in plant communities. It also discussed how managed bees may interact with wild bees by transmitting pathogens. It found an equal number of studies reporting both positive and negative effects on plant communities. Studies examining resource competition had significant variability in their results while most studies on pathogen transmission pointed to potentially detrimental impacts. The researchers noted that most studies documented the possibility of certain interactions without actually measuring the direct effects. Do managed bees have negative effects on wild bees?: A systematic review of the literature
The very generalized nature of the honey bee's nectar-gathering activities, potentially visiting dozens of different species in a single day, means that a flower visited by a honey bee will often get very little pollen from its species. This diminished pollination can reduce the plant's ability to produce seeds, especially when the honey bees are squeezing out the native pollinators for a species, a problem occurring all over the United States because of honey bees and other invasive species.
Most flowering plants depend on specialized pollinators to efficiently fertilize them. Cucurbitaceae, for example, are pollinated by that specifically visit the early-blooming male flowers before sunrise, when honey bees are inactive, and then return to pollinate the female flowers later in the day. Such symbiosis also mean that the specialized pollinator will be covered mainly in its host's specific pollen. Unlike native bees, they do not properly extract or transfer pollen from plants with Stamen (anthers which only release pollen through tiny apical pores); this requires buzz pollination, a behavior rarely exhibited by honey bees. Honey bees reduce fruiting in Melastoma affine, a plant with pore anthers, by robbing its stigmas of previously deposited pollen.
Social caste
Queens
Workers
Drones
Queen–worker conflict
Behavior
Thermoregulation
Aging
Communication
Pheromones
Sociality
Domestication
Beekeeping
Products
Honey bees
Pollination
Honey
Beeswax
Bee bread
Bee brood
Propolis
Royal jelly
Genome
Hazards and survival
Parasites, diseases and pesticides
Egyptian honeybee Ark of taste and Apis mellifera carnica. Improved cultural practices and chemical treatments against Varroa mites saved most commercial operations; new bee breeds are beginning to reduce beekeeper dependence on . Feral bee populations were greatly reduced during this period; they are slowly recovering, primarily in mild climates, due to natural selection for Varroa resistance and repopulation by resistant breeds. Although it is generally believed that insecticides have also depleted bee populations, particularly when used in excess of label directions, as bee pests and diseases (including American foulbrood and tracheal mites) are becoming resistant to medications, research in this regard has not been conclusive. A 2012 study of the effect of neonicotinoid-based insecticides showed "no effects observed in field studies at field-realistic dosages." A new study in 2020 found that neonicotinoid insecticides affected the developmental stability of honey bees, particularly haploid males were more susceptible to neonicotinoids than diploid females. The 2020 study also found that heterozygosity may play a key role in buffering insecticide exposure.
Milkweed
Predators
/ref> both and black bears, , , , the North American least shrew and the honey badger.
Immune mechanisms
Innate immune mechanisms
Social immune mechanisms
Grooming
Hygienic behavior
As an environmental threat
Our review found that the majority of studies reach the conclusion that managed bees negatively affect, or have the potential to negatively affect, wild bees through competition, changes in plant communities, or transmission of pathogens.
Close relatives
See also
Bibliography
External links
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