Western honey bee

A bee swarm. Bees are non-aggressive in this state, since they have no hive to protect.

Unlike most other bee species, western honey bees have perennial colonies which persist year after year. Because of this high degree of sociality and permanence, western honey bee colonies can be considered superorganisms. This means that reproduction of the colony, rather than individual bees, is the biologically significant unit. Western honey bee colonies reproduce through a process called "swarming".[11]

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,[12] 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 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.[13] 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.

Larvae (left) and eggs (right)

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 western 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 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 bees of any other genus and 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 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).[11]

Although the average lifespan 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.[14] 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.[15] Except for the queen, all of a colony's workers are replaced about every four months.

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 queen larva are both fed royal jelly, which is high in protein and low in flavonoid, during the first three days. After that, workers are switched to a diet of mixed pollen and nectar (often called "bee bread"), while queens 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[18]—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 its end, the old queen is usually 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 try 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.

Peanut-like queen brood cells extend outward from the brood comb

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 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 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 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.

Development of a drone pupa

Pupae of 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 mate with a given queen in flight; each dies 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. Given their larger size (1.5 times that of worker bees), inside the hive it is believed that drones may play a significant role in thermoregulation. 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.[19]

Foraging honey bee

The western 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).

Western honey bees can forage over a 30 °C (54 °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.[27]

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).[28]

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

A large honey bee swarm on a fallen tree trunk

Western honey bee behavior has been extensively studied. 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.[29] 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.

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, dwarf honey bees, do not.[30] Therefore, western honey bees seem to have evolved a better means of conveying information than their common ancestors with the dwarf honey bee.[31]

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.

Pheromones (substances involved in chemical communication) are essential to honey bee survival. Western honey bees rely on pheromones for nearly all behaviors, including mating, alarm, defense, orientation, kin and colony recognition, food production and integrating colony activities.[32][33]

There is some degree of variability of sociality between individuals.[34][35] Like a great many other social insects, A. mellifera engages in trophallaxis.[34][35] When the duration of trophallaxis pairings was measured, it was found that like human social interactions, there are durable long-term trends for each individual bee.[34][35] There is less inter-individual variation than found in humans however, possibly reflecting the higher genetic relatedness between hivemates.[34]

Honey bees are one of the products of a beehive. They can be purchased as mated queens, in spring packages of a queen along with two to five pounds (0.91 to 2.27 kg) of honey bees, as nucleus colonies (which include frames of brood), or as full colonies. Commerce of western honey bees dates back to as early as 1622, when the first colonies of bees were shipped from England to Virginia. Modern methods of producing queens and dividing colonies for increase date back to the late 1800s. Honey was extracted by killing off the hive, and bees and bee products were mainly an object of local trade. The first commercial beekeeper in the United States is considered Moses Quinby of New York, who experimented with movable box hives, which allow extraction without killing the hive. The improvements in roads and motor vehicles after World War I allowed commercial beekeepers to expand the size of their businesses.[49]

Western honey bee pollinating a flower

The western honey bee is an important pollinator of crops; this service accounts for much of the species' commercial value. In 2005, the estimated commercial value of western honey bees was just under $200 billion worldwide.[50] A large number of the crop species farmed worldwide depend on it.[51] Although orchards and fields have increased in size, wild pollinators have dwindled. In a number of regions the pollination shortage is addressed by migratory beekeepers, who supply hives during a crop bloom and move them after the blooming period. Commercial beekeepers plan their movements and wintering locations according to anticipated pollination services. At higher latitudes it is difficult (or impossible) to overwinter sufficient bees, or to have them ready for early blooming plants. Much migration is seasonal, with hives wintering in warmer climates and moving to follow the bloom at higher latitudes.

In California, almond pollination occurs in February, early in the growing season before local hives have built up their populations. Almond orchards require two hives per acre, or 2,000 m² (22,000 sq ft) 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,[52] 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;[53] this prevents flower stigmas from being clogged with pollen from other species.[54] In 2000, Drs. Roger Morse and Nicholas Calderone of Cornell University attempted to quantify the effects of the western honey bee on only US food crops. Their calculations came up with a figure of US$14.6 billion in food crop value.[55]

Honey is the complex substance made from nectar and sweet deposits from plants and trees, which are gathered, modified and stored in the comb by honey bees.[56] Honey is a biological mixture of inverted sugars, primarily glucose and fructose. It has antibacterial and anti-fungal properties. Honey from the western honey bee, along with the bee Tetragonisca angustula, has specific antibacterial activity towards an infection-causing bacteria, Staphylococcus aureus.[57] Honey will not rot or ferment when stored under normal conditions, but it will crystallize over time. Although crystallized honey is acceptable for human use, bees can only use liquid honey and will remove and discard any crystallized honey from the hive.

Western honey bee with "tongue" partially extended

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 wings. When the honey has dried, the honeycomb cells are sealed (capped) with wax to preserve it.

Mature worker bees secrete beeswax from glands on their abdomen, using it to form the walls and caps of the comb.[58] When honey is harvested, the wax can be collected for use in products like candles and seals.

Bees collect pollen in a pollen basket and carry it back to the hive where, after undergoing fermentation and turning into bee bread, it becomes a protein source for brood-rearing.[59] Excess pollen can be collected from the hive; although it is sometimes consumed as a dietary supplement by humans, bee pollen may cause an allergic reaction in susceptible individuals.

Bee brood, the eggs, larvae, or pupae of honey bees, is edible and highly nutritious. Bee brood contains the same amount of protein that beef or poultry does. Bee brood is often harvested as a byproduct when the beekeeper has excess bees and does not wish to have any more.

Propolis is a resinous mixture collected by honey bees from tree buds, sap flows or other botanical sources, which is used as a sealant for unwanted open spaces in the hive.[60] Although propolis is alleged to have health benefits (tincture of propolis is marketed as a cold and flu remedy), it may cause severe allergic reactions in some individuals.[61] Propolis is also used in wood finishes, and gives a Stradivarius violin its unique red color.[62]

Royal jelly is a honey bee secretion used to nourish the larvae and queen.[63] It is marketed for its alleged but unsupported claims of health benefits.[64][65] On the other hand, it may cause severe allergic reactions in some individuals.[66]

Western honey bee populations face threats to their survival increasing interests into other pollinator species, like the common eastern bumblebee.[70] North American and European populations were severely depleted by Varroa mite infestations during the early 1990s, and U.S. beekeepers were further affected by colony collapse disorder in 2006 and 2007.[71] Improved cultural practices and chemical treatments against Varroa mites saved most commercial operations; new bee breeds are beginning to reduce beekeeper dependence on acaricides. 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." [72] 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.[73] The 2020 study also found that heterozygosity may play a key role in buffering insecticide exposure.[73]

An East African lowland honey bee (Apis mellifera scutellata) in Tanzania extracts nectar from a flower, as pollen grains stick to its body

Insect predators of western honey bees include the Asian giant hornet and other wasps, robber flies, dragonflies such as the green darner, some praying mantises, water striders and the European beewolf.

Arachnid predators of western honey bees include fishing spiders, lynx spiders, goldenrod spiders[74] and St. Andrew's cross spiders.

Reptile and amphibian predators of western honey bees include the black girdled lizard, anoles, and other lizards, and various anuran amphibians including the American toad, the American bullfrog and the wood frog.

Specialist bird predators of western honey bees include the bee-eaters; other birds that may take western honey bees include grackles, hummingbirds, 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.[75]

Mammals that sometimes take western honey bees include bears, opossums, raccoons, skunks, the North American least shrew and the honey badger.