European honey bee (Apis mellifera)

The western honey bee or European honey bee (Apis mellifera) is the most common of the 7–12 species of honey bee worldwide. The genus name Apis is Latin for "bee", and mellifera is the Latin for "honey-bearing", referring to the species' production of honey.

Like all honey bees, the western honey bee is eusocial, creating colonies with a single fertile female (or "queen"), many normally non-reproductive females or "workers," and 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 pheromones and the dance language.

The western honey bee was one of the first domesticated 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. Because of its wide cultivation, this species is the single most important pollinator for agriculture globally. Honey bees are threatened by pests and diseases, especially the varroa mite and colony collapse disorder.

Western honey bees are an important model organism in scientific studies, particularly in the fields of social evolution, learning, and memory; they are also used in studies of pesticide toxicity, to assess non-target impacts of commercial pesticides.

Distribution and habitat
The western honey bee can be found on every continent except Antarctica.The species is believed to have originated in Africa  or Asia,and it spread naturally through Africa, the Middle East and Europe.Humans are responsible for its considerable additional range, introducing European subspecies into North America (early 1600s),South America, Australia, New Zealand, and East Asia. 

Western honey bees adapted to the local environments as they spread geographically.These adaptations include synchronizing colony cycles to the timing of local flower resources, forming a winter cluster in colder climates, migratory swarming in Africa, and enhanced foraging behavior in desert areas. All together, these variations resulted in 28 recognized subspecies,all of which are cross-fertile. 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.

Life cycle
Colony life cycle
Unlike most other bee species, honey bees have perennial colonies which persist year after year. Because of this high degree of sociality and permanence, honey bee colonies can be considered superorganisms, meaning that reproduction of the colony, rather than individual bees, is the biologically significant unit. Honey bee colonies reproduce through a process called "swarming".

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 pupal 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 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 shared with wasps, bees, 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 nuptial flights, each time mating with 1–17 drones.Once she has finished mating, usually within two weeks of emerging, she remains in the hive, 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 worker bees, who evaporate it until the moisture content is low enough to discourage mold, transforming it into honey, which can then be capped over with wax 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.

Individual bee life cycle
Like other insects that undergo complete metamorphosis, the western honey bee has four distinct life stages: egg, larva, pupa and adult. The complex social structure of honey bee hives means that all of these life stages occur simultaneously throughout much of the year. The queen deposits a single egg into each cell of a honeycomb prepared by worker bees. The egg hatches into a legless, eyeless larva fed by "nurse" bees (worker bees who maintain the interior of the colony). After about a week, the larva is sealed in its cell by the nurse bees and begins its pupal stage. After another week, it emerges as an adult bee. It is common for defined regions of the comb to be filled with young bees (also called "brood"), while others are filled with pollen and honey stores.

Worker bees secrete the wax 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 ten 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, a stinger, with which they defend the hive. Unlike bees of any other genus and the queens of their own species, the stinger of worker 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 pull free of the body 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 average lifespan of a queen in most subspecies is three to five years, reports from the German-European black bee subspecies 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 will work hard, living only a few weeks, but those born in autumn will remain inside for several months as the colony clusters. On average during the year, about one percent of a colony's worker bees die naturally per day.Except for the queen, all of a colony's workers are replaced about every four months.

Social caste
Behavioral and physiological differences between castes and subcastes arise from phenotypic plasticity, which relies on gene expressionrather than heritable genotypic differences.

Queens
The queen bee is a fertile female, who, unlike workers (which are genetically also female), has a fully developed reproductive tract. She is larger than her workers, and has a characteristic rounder, longer abdomen. A female egg can become either a queen or a worker bee. Workers and queens are both fed royal jelly, which is high in protein and low in flavonoid, during the first three days of their larval stage. Workers are then switched to a diet of mixed pollen and nectar (often called "bee bread"), while queens will continue to receive royal jelly. In the absence of flavonoid and the presence of a high-protein diet, queen bees develop a healthy reproductive tract—a task necessary for maintaining a colony of tens of thousands of daughter-workers.

Periodically, the colony determines that a new queen is needed. There are three general causes:

1. 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 and leave the new queen with the other half of the workers to continue the old one.
2. The old queen begins to fail, which is thought to be demonstrated by a decrease in queen pheromones throughout the hive. This is known as supersedure, and at the end of the supersedure the old queen is generally killed.
3. The old queen dies suddenly, a situation known as emergency supersedure. The worker bees find several eggs (or larvae) of the appropriate age range and attempt to develop them into queens. 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 the larvae into queens by continuing to feed them royal jelly.

After several days of orientation in 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 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.

Workers
Workers are females produced by the queen that develop from fertilized, diploid eggs. Workers are essential for social structure and proper colony functioning. They carry out the main tasks of the colony, because the queen is occupied with only reproducing. These females will raise their sister workers and future queens that eventually leave the nest to start their own colony. They also forage and return to the nest with nectar and pollen to feed the young.

Drones
Drones are the colony's male bees. Since they do not have ovipositors, they do not have stingers. Drone honey bees do not forage for nectar or pollen. The primary purpose of a drone is to fertilize a new queen. Many drones will mate with a given queen in flight; each will die immediately after mating, since the process of insemination requires a lethally convulsive effort. Drone honey bees are haploid (single, unpaired chromosomes) in their genetic structure, and are descended only from their mother (the queen). In temperate regions drones are generally expelled from the hive before winter, dying of cold and starvation since they cannot forage, produce honey or care for themselves. There has been research into the role western honey bee drones play in thermoregulation within the hive. Given their larger size (1.5 times that of worker bees), drones may play a significant role. Drones are typically located near the center of hive clusters for unclear reasons. It is postulated that it is to maintain sperm viability, which may be compromised at cooler temperatures. Another possible explanation is that a more central location allows drones to contribute to warmth, since at temperatures below 25 °C (77 °F) their ability to contribute declines.

Behavior
Thermoregulation
The honey bee needs an internal body temperature of 35 °C (95 °F) to fly; this temperature is maintained in the nest to develop the brood, and is the optimal temperature for the creation of wax. The temperature on the periphery of the cluster varies with outside air temperature, and the winter cluster's internal temperature may be as low as 20–22 °C (68–72 °F).

Honey bees can forage over a 30 °C (86 °F) 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 22–25 °C (72–77 °F). 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 10 °C (18 °F). 

Below 7–10 °C (45–50 °F) bees are immobile, and above 38 °C (100 °F) their activity slows. Honey bees can tolerate temperatures up to 50 °C (122 °F) for short periods.

Communication
Honey-bee behavior has been extensively studied, since bees are widespread and familiar. Karl von Frisch, who received the 1973 Nobel Prize in Physiology or Medicine for his study of honey-bee communication, noticed that bees communicate with dance. Through these dances, bees communicate information regarding the distance, the situation, and the direction of a food source by the dances of the returning (honey bee) worker bee on the vertical comb of the hive.Honey bees direct other bees to food sources with the round dance and the waggle dance. Although the round dance tells other foragers that food is within 50 metres (160 ft) of the hive, it provides insufficient information about direction. The waggle dance, which may be vertical or horizontal, provides more detail about the distance and direction of a food source. Foragers are also thought to rely on their olfactory sense to help locate a food source after they are directed by the dances. Unlike western honey bees, the dwarf honey bee do not change the precision of the waggle dance to indicate the type of site that is set as a new goal.Therefore, western honey bees are better at conveying information than its closely related species and this further supports the notion that former are more evolved than latter.

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 percent of observed shaking signals and 64 percent of these signals were made after the discovery of a food source. About 71 percent 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.

Pheromones
Pheromones (substances involved in chemical communication) are essential to honey-bee survival. Honey bees rely on pheromones for nearly all behaviors, including mating, alarm, defense, orientation, kin and colony recognition, food production and integrating colony activities.

See morre: en.wikipedia.org

https://en.wikipedia.org/wiki/Western_honey_bee