Western honey bee

Behavior

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. 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. 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 may be produced every year, or less frequently, depending on local environmental conditions.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. 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, 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 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 is thought to have evolved in response to predation by vertebrates, since the barbs do not function 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.

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

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, 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.

Africanized bees have spread across the southern United States, where they pose a slight danger to humans. As an invasive species, feral honey bees have become a significant environmental problem in non-native areas. Imported bees may displace native bees and birds, and may also promote the reproduction of invasive plants ignored by native pollinators. Unlike native bees, they do not properly extract or transfer pollen from plants with pore anthers; 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.

Predators

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

Arachnid predators of honeybees include fishing spiders, lynx spiders, goldenrod spiders and the St Andrew's Cross spider.

Reptile and amphibian predators of honeybees include the American toad, anoles, the American bullfrog and the wood frog.

Specialist bird predators include the bee-eaters; other birds that may take bees include grackles, hummingbirds, summer tanagers, and tyrant flycatchers. 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.

Mammals that sometimes take bees include bears, least shrews, opossums, raccoons, honey badgers and skunks.

Uses

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.