Bees are that form a monophyly clade Anthophila within the superfamily Apoidea of the order Hymenoptera,[Engel, M. S. (2005) Family-group names for bees (Hymenoptera, Apoidea). American Museum Novitates 3476.] with over 20,000 known species in seven recognized families.
Unlike the closely related and , who are carnivorous/omnivorous, bees are that specifically feed on nectar (nectarivory) and pollen (palynivory), the former primarily as a carbohydrate source for metabolic energy, and the latter primarily for protein and other for their . They are found on every continent except Antarctica, and in every habitat on the planet that contains entomophily . The most common bees in the Northern Hemisphere are the Halictidae, or sweat bees, but they are small and often mistaken for wasps or flies. Bees range in size from tiny stingless bee species, whose workers are less than long,
Bees are best known to for their ecological roles as and, in the case of the best-known species, the western honey bee, for producing honey, a regurgitated and food drying viscous mixture of partially digested kept as food storage of the bee colony. Pollination management via bees is important both ecologically and agriculturally, and the decline in wild bee populations has increased the demand and value of domesticated pollination by commercially managed hives of honey bees. The analysis of 353 wild bee and hoverfly species across Britain from 1980 to 2013 found the insects have been lost from a quarter of the places they inhabited in 1980.
Evolution
The immediate ancestors of bees were Aculeata in the family Ammoplanidae, which were Predation of other insects.
Based on phylogenetic analysis, bees are thought to have originated during the Early Cretaceous (about 124 million years ago) on the supercontinent of Gondwana, just prior to its breakup into South America and Africa. The supercontinent is thought to have been a largely xeric environment at this time; modern bee diversity hotspots are also in xeric and seasonal temperate environments, suggesting strong niche conservatism among bees ever since their origins.
Genomic analysis indicates that despite only appearing much later in the fossil record, all modern bee families had already diverged from one another by the end of the Cretaceous. The Melittidae, Apidae, and Megachilidae had already evolved on the supercontinent prior to its fragmentation. Further divergences were facilitated by West Gondwana's breakup around 100 million years ago, leading to a deep Africa-South America split within both the Apidae and Megachilidae, the isolation of the Melittidae in Africa, and the origins of the Colletidae, Andrenidae and Halictidae in South America. The rapid radiation of the South American bee families is thought to have followed the concurrent radiation of within the same region. Later in the Cretaceous (80 million years ago), colletid bees colonized Australia from South America (with an offshoot lineage evolving into the Stenotritidae), and by the end of the Cretaceous, South American bees had also colonized North America.
Following the K-Pg extinction, surviving bee lineages continued to spread into the Northern Hemisphere, colonizing Europe from Africa by the Paleocene, and then spreading east to Asia. This was facilitated by the warming climate around the same time, allowing bees to move to higher latitudes following the spread of tropical and subtropical habitats. By the Eocene (~45 mya) there was already considerable diversity among eusocial bee lineages.
Fossils
The oldest non-compression bee fossil is Cretotrigona prisca, a Apinae of Late Cretaceous age (~70 mya) found in New Jersey amber.
The Allodapini (within the Apidae) appeared around 53 Mya.
Coevolution
The earliest animal-pollinated flowers were shallow, cup-shaped blooms pollination by insects such as , so the syndrome of insect pollination was well established before the first appearance of bees. The novelty is that bees are specialized as pollination agents, with behavioral and physical modifications that specifically enhance pollination, and are the most efficient pollinating insects. In a process of coevolution, flowers developed floral rewards[ Bees also developed structures known as scopal hairs and pollen baskets to collect and carry pollen. The location and type differ among and between groups of bees. Most species have scopal hairs on their hind legs or on the underside of their abdomens. Some species in the family Apidae have pollen baskets on their hind legs, while very few lack these and instead collect pollen in their crops.]
Phylogeny
External
Molecular phylogeny was used by Debevic et al, 2012, to demonstrate that the bees (Anthophila) arose from deep within the Crabronidae sensu lato, which was thus rendered paraphyly. In their study, the placement of the monogeneric Heterogyna was uncertain. The small family Mellinidae was not included in this analysis.
Further studies by Sann et al., 2018, elevated the subfamilies (plus one tribe and one subtribe) of Crabronidae sensu lato to family status. They also recovered the placement of Heterogyna within Nyssonini and sunk Heterogynaidae. The newly erected family, Ammoplanidae, formerly a subtribe of Pemphredonidae, was recovered as the most sister family to bees.
Internal
This cladogram of the bee families is based on Hedtke et al., 2013, which places the former families Dasypodaidae and Meganomiidae as subfamilies inside the Melittidae.
Characteristics
Bees differ from closely related groups such as wasps by having branched or plume-like (hairs), combs on the forelimbs for cleaning their antennae, small anatomical differences in limb structure, and the venation of the hind wings; and in females, by having the seventh dorsal abdominal plate divided into two half-plates.
Bees have the following characteristics:[
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A pair of large compound eyes which cover much of the surface of the head. Between and above these are three small simple eyes (ocelli) which provide information on light intensity.
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The antennae usually have 13 segments in males and 12 in females, and are geniculate, having an elbow joint part way along. They house large numbers of sense organs that can detect touch (mechanoreceptors), smell and taste; and small, hairlike mechanoreceptors that can detect air movement so as to "hear" sounds.
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The mouthparts are adapted for both chewing and sucking by having both a pair of mandibles and a long proboscis for sucking up nectar.
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The thorax has three segments, each with a pair of robust legs, and a pair of membranous wings on the hind two segments. The front legs of corbiculate bees bear combs for cleaning the antennae, and in many species the hind legs bear pollen baskets, flattened sections with incurving hairs to secure the collected pollen. The wings are synchronized in flight, and the somewhat smaller hind wings connect to the forewings by a row of hooks along their margin which connect to a groove in the forewing.
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The abdomen has nine segments, the hindermost three being modified into the sting.
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The largest species of bee is thought to be Wallace's giant bee Megachile pluto, whose females can attain a length of .
Sociality
Haplodiploid breeding system
According to inclusive fitness theory, organisms can gain fitness not just through increasing their own reproductive output, but also that of close relatives. In evolutionary terms, individuals should help relatives when Cost < Relatedness * Benefit. The requirements for eusociality are more easily fulfilled by haplodiploid species such as bees because of their unusual relatedness structure.
In haplodiploid species, females develop from fertilized eggs and males from unfertilized eggs. Because a male is haploid (has only one copy of each gene), his daughters (which are diploid, with two copies of each gene) share 100% of his genes and 50% of their mother's. Therefore, they share 75% of their genes with each other. This mechanism of sex determination gives rise to what W. D. Hamilton termed "supersisters", more closely related to their sisters than they would be to their own offspring.
Haplodiploidy is neither necessary nor sufficient for eusociality. Some eusocial species such as termites are not haplodiploid. Conversely, all bees are haplodiploid but not all are eusocial, and among eusocial species many queens mate with multiple males, creating half-sisters that share only 25% of each other's genes.
Eusociality
Bees may be solitary or may live in various types of communities. Eusociality appears to have originated from at least three independent origins in halictid bees.
True honey bees (genus Apis, of which eight species are currently recognized) are highly eusocial, and are among the best known insects. Their colonies are established by swarms, consisting of a queen and several thousand workers. There are 29 subspecies of one of these species, Apis mellifera, native to Europe, the Middle East, and Africa. are a hybrid strain of A. mellifera that escaped from experiments involving crossing European and African subspecies; they are extremely defensive.
are also highly eusocial. They practice mass provisioning, with complex nest architecture and perennial colonies also established via swarming.
Many bumblebees are eusocial, similar to the eusocial Vespidae such as in that the queen initiates a nest on her own rather than by swarming. Bumblebee colonies typically have from 50 to 200 bees at peak population, which occurs in mid to late summer. Nest architecture is simple, limited by the size of the pre-existing nest cavity, and colonies rarely last more than a year.
There are many more species of primitively eusocial than highly eusocial bees, but they have been studied less often. Most are in the family Halictidae, or "sweat bees". Colonies are typically small, with a dozen or fewer workers, on average. Queens and workers differ only in size, if at all. Most species have a single season colony cycle, even in the tropics, and only mated females hibernate. A few species have long active seasons and attain colony sizes in the hundreds, such as Halictus hesperus.
Solitary and communal bees
Most other bees, including familiar insects such as , leafcutter bees and mason bees are solitary in the sense that every female is fertile, and typically inhabits a nest she constructs herself. There is no division of labor so these nests lack queens and worker bees for these species. Solitary bees typically produce neither honey nor beeswax.
Bees collect pollen to feed their young, and have the necessary adaptations to do this. However, certain wasp species such as have similar behaviours, and a few species of bee Scavenger from carcases to feed their offspring.[ Solitary bees are important pollinators; they gather pollen to provision their nests with food for their brood. Often it is mixed with nectar to form a paste-like consistency. Some solitary bees have advanced types of pollen-carrying structures on their bodies. Very few species of solitary bee are being cultured for commercial pollination. Most of these species belong to a distinct set of genus which are commonly known by their nesting behavior or preferences, namely: carpenter bees, Halictidae, mason bees, plasterer bees, , Ceratina, leafcutter bees, and Anthophorini.]
Most solitary bees are fossorial, digging nests in the ground in a variety of soil textures and conditions, while others create nests in hollow Phragmites or twigs, or holes in wood. The female typically creates a compartment (a "cell") with an egg and some provisions for the resulting larva, then seals it off. A nest may consist of numerous cells. When the nest is in wood, usually the last (those closer to the entrance) contain eggs that will become males. The adult does not provide care for the brood once the egg is laid, and usually dies after making one or more nests. The males typically emerge first and are ready for mating when the females emerge. Solitary bees are very unlikely to sting (only in self-defense, if ever), and some (esp. in the family Andrenidae) are stingless.
While solitary, females each make individual nests.[
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Biology
Life cycle
The life cycle of a bee, be it a solitary or social species, involves the laying of an egg, the development through several moults of a legless larva, a stage during which the insect undergoes Holometabolism, followed by the emergence of a winged adult. The number of eggs laid by a female during her lifetime can vary from eight or less in some solitary bees, to more than a million in highly social species.[ The Bees of the World, Volum 1] Most solitary bees and bumble bees in temperate climates overwinter as adults or pupae and emerge in spring when increasing numbers of flowering plants come into bloom. The males usually emerge first and search for females with which to mate. Like the other members of Hymenoptera, bees are Haplodiploidy; the sex of a bee is determined by whether or not the egg is fertilized. After mating, a female stores the sperm, and determines which sex is required at the time each individual egg is laid, fertilized eggs producing female offspring and unfertilized eggs, males. Tropical bees may have several generations in a year and no diapause stage.
The egg is generally oblong, slightly curved and tapering at one end. Solitary bees, lay each egg in a separate cell with a supply of mixed pollen and nectar next to it. This may be rolled into a pellet or placed in a pile and is known as mass provisioning. Social bee species provision progressively, that is, they feed the larva regularly while it grows. The nest varies from a hole in the ground or in wood, in solitary bees, to a substantial structure with wax combs in bumblebees and honey bees.
In most species, larvae are whitish grubs, roughly oval and bluntly-pointed at both ends. They have 15 segments and spiracles in each segment for breathing. They have no legs but move within the cell, helped by tubercles on their sides. They have short horns on the head, jaws for chewing food and an appendage on either side of the mouth tipped with a bristle. There is a gland under the mouth that secretes a viscous liquid which solidifies into the silk they use to produce a cocoon. The cocoon is semi-transparent and the pupa can be seen through it. Over the course of a few days, the larva undergoes metamorphosis into a winged adult. When ready to emerge, the adult splits its skin dorsally and climbs out of the and breaks out of the cell.[
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File:Apoidea.jpg|Nest of Bombus pascuorum bumblebee, wax canopy removed to show winged workers and pupae in irregularly placed wax cells
File:Carpenter Bee Galleries.jpeg|Carpenter bee nests in a cedar wood beam (sawn open)
File:Bienen mit Brut 2.jpg|Honeybees on brood comb with eggs and larvae in cells
Flight
Antoine Magnan's 1934 book Le vol des insectes says that he and André Sainte-Laguë had applied the equations of air resistance to and found that their flight could not be explained by fixed-wing calculations, but that "One shouldn't be surprised that the results of the calculations don't square with reality".[Ingram, Jay (2001) The Barmaid's Brain, Aurum Press, pp. 91–92, .] This has led to a common misconception that bees "violate aerodynamic theory". In fact it merely confirms that bees do not engage in fixed-wing flight, and that their flight is explained by other mechanics, such as those used by .[ Re: work of Dr. Michael H. Dickinson.] showed that lift was generated by "the unconventional combination of short, choppy wing strokes, a rapid rotation of the wing as it flops over and reverses direction, and a very fast wing-beat frequency". Wing-beat frequency normally increases as size decreases, but as the bee's wing beat covers such a small arc, it flaps approximately 230 times per second, faster than a Drosophilidae (200 times per second) which is 80 times smaller.
Navigation, communication, and finding food
The ethologist Karl von Frisch studied navigation in the honey bee. He showed that honey bees communicate by the waggle dance, in which a worker indicates the location of a food source to other workers in the hive. He demonstrated that bees can recognize a desired compass direction in three different ways: by the Sun, by the polarization pattern of the blue sky, and by the Earth's magnetic field. He showed that the Sun is the preferred or main compass; the other mechanisms are used under cloudy skies or inside a dark beehive.
Digestion
The gut of bees is relatively simple, but multiple metabolic strategies exist in the gut microbiota.
Although most bee species are Nectarivore and Palynivore, some are not. Particularly unusual are in the genus Trigona, which consume carrion and wasp brood, turning meat into a honey-like substance.[ Plant guttation provides nutrient-rich food for insects - Journals]
Ecology
Floral relationships
Most bees are polylectic (generalist) meaning they collect pollen from a range of flowering plants, but some are (specialists), in that they only gather pollen from one or a few species or genera of closely related plants.
In rare cases, a plant species may only be effectively pollinated by a single bee species, and some plants are endangered at least in part because their pollinator is also threatened. But, there is a pronounced tendency for oligolectic bees to be associated with common, widespread plants visited by multiple pollinator species. For example, the creosote bush in the arid parts of the United States southwest is associated with some 40 oligoleges.
As mimics and models
Many bees are colored, typically orange and black, warning of their ability to defend themselves with a powerful sting. As such they are models for Batesian mimicry by non-stinging insects such as bee-flies, Asilidae and hoverflies,
Bees are themselves Müllerian mimics of other aposematic insects with the same color scheme, including , Lycidae and other beetles, and many butterflies and moths (Lepidoptera) which are themselves distasteful, often through acquiring bitter and poisonous chemicals from their plant food. All the Müllerian mimics, including bees, benefit from the reduced risk of predation that results from their easily recognized warning coloration.
Bees are also mimicked by plants such as the Ophrys apifera which imitates both the appearance and the scent of a female bee; male bees attempt to mate (pseudocopulation) with the furry lip of the flower, thus pollinating it.
As brood parasites
occur in several bee families including the apidae subfamily Nomadinae.[Gjershaug, Jan Ove (5 June 2009). "The social parasite bumblebee Bombus hyperboreus Schönherr, 1809 usurp nest of Bombus balteatus Dahlbom, 1832 (Hymenoptera, Apidae) in Norway" (PDF). Norwegian Journal of Entomology 56(1): 28–31. Retrieved 26 September 2015.]
In Southern Africa, hives of African honeybees ( A. mellifera scutellata) are being destroyed by parasitic workers of the Cape honeybee, A. m. capensis. These lay diploid eggs ("thelytoky"), escaping normal worker policing, leading to the colony's destruction; the parasites can then move to other hives.
The in the Bombus subgenus Psithyrus are closely related to, and resemble, their hosts in looks and size. This common pattern gave rise to the ecological principle "Emery's rule". Others parasitize bees in different families, like Townsendiella, a nomadinae apidae, two species of which are cleptoparasites of the Dasypodaidae genus Hesperapis,
Nocturnal bees
Four bee families (Andrenidae, Colletidae, Halictidae, and Apidae) contain some species that are crepuscular. Most are tropical or subtropical, but some live in arid regions at higher latitudes. These bees have greatly enlarged ocellus, which are extremely sensitive to light and dark, though incapable of forming images. Some have refracting superposition compound eyes: these combine the output of many elements of their compound eyes to provide enough light for each retinal photoreceptor. Their ability to fly by night enables them to avoid many predators, and to exploit flowers that produce nectar only or also at night.
Predators, parasites and pathogens
Vertebrate predators of bees include , shrikes and flycatchers, which make short sallies to catch insects in flight.
Specialist ambush predators of visitors to flowers include crab spiders, which wait on flowering plants for pollinating insects; Hemiptera, and ,
Some mites of genus Tarsonemus are associated with bees. They live in bee nests and ride on adult bees for dispersal. They are presumed to feed on fungi, nest materials or pollen. However, the impact they have on bees remains uncertain.
Relationship with humans
In mythology and folklore
Homer's Homeric Hymns describes three bee-maidens with the power of divination and thus speaking truth, and identifies the food of the gods as honey. Sources associated the bee maidens with Apollo and, until the 1980s, scholars followed Gottfried Hermann (1806) in incorrectly identifying the bee-maidens with the Thriae.[Susan Scheinberg, "The Bee Maidens of the Homeric Hymn to Hermes", in Albert Heinrichs, ed., Harvard Studies in Classical Philology (Cambridge MA: Harvard University Press, 1980), 11. ; and many others since questioning Gottfried Hermann's 1806 equation of the Thriae with bee-maidens. Heinrich Gottfried, Homeri nomine dignissimum/Homeric Hymns (Leipzig: 1806), 346 and cxiii. Many took Hermann's unfounded identification at face-value, repeating it ad nauseam, e.g. Hilda M. Ransome, The Sacred Bee in Ancient Times and Folklore (NY: Courier, 1937; reprinted as recently as NY: Dover, 2012), 97. ] Honey, according to a Greek myth, was discovered by a nymph called Melissa ("Bee"); and honey was offered to the Greek gods from Helladic period. Bees were also associated with the Delphic oracle and the prophetess was sometimes called a bee.
The image of a community of honey bees has been used from ancient to modern times, in Aristotle and Plato; in Virgil and Seneca; in Erasmus and Shakespeare; Tolstoy, and by political and social theorists such as Bernard Mandeville and Karl Marx as a model for human society.[ Eagle and the bee on the Napoleonic coat of arms]
In art and literature
Some of the oldest examples of bees in art are Cave painting in Spain which have been dated to 15,000 BC.
W. B. Yeats's poem The Lake Isle of Innisfree (1888) contains the couplet "Nine bean rows will I have there, a hive for the honey bee, / And live alone in the bee loud glade." At the time he was living in Bedford Park in the West of London.
Bees have appeared in films such as Jerry Seinfeld's animated Bee Movie,
Beekeeping
Humans have kept honey bee colonies, commonly in beehive, for millennia.[ Depictions of humans collecting honey from wild bees date to 15,000 years ago; efforts to domesticate them are shown in Egyptian art around 4,500 years ago.]
Among Classical Era authors, beekeeping with the use of smoke is described in Aristotle's History of Animals Book 9.[
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From the 18th century, European understanding of the colonies and biology of bees allowed the construction of the moveable comb hive so that honey could be harvested without destroying the colony.[Thomas Wildman, A Treatise on the Management of Bees (London, 1768, 2nd edn 1770).]
As commercial pollinators
Bees play an important role in pollination , and are the major type of pollinator in many that contain flowering plants. It is estimated that one third of the human food supply depends on pollination by insects, birds and bats, most of which is accomplished by bees, whether wild or domesticated.
Since the 1970s, there has been a general decline in the species richness of wild bees and other pollinators, probably attributable to stress from increased parasites and disease, the use of pesticides, and a decrease in the number of wild flowers. Climate change probably exacerbates the problem.
Contract pollination has overtaken the role of honey production for in many countries. After the introduction of Varroa mites, feral honey bees declined dramatically in the US, though their numbers have since recovered.[Johnson, Kirk (6 October 2010) Scientists and Soldiers Solve a Bee Mystery . The New York Times.][ "Honey bees in US facing extinction" , The Daily Telegraph (London), 14 March 2007.] Winter losses increased to about 1/3.[Benjamin, Alison (2 May 2010) Fears for crops as shock figures from America show scale of bee catastrophe . The Observer (London).]
Apart from colony collapse disorder, losses outside the US have been attributed to causes including pesticide seed dressings, using such as clothianidin, imidacloprid and thiamethoxam.[Gosden, Emily (29 March 2014) Bees and the crops they pollinate are at risk from climate change, IPCC report to warn The Daily Telegraph (London). Retrieved 30 March 2014] In 2018 the European Union decided to ban field use of all three major neonicotinoids; they remain permitted in veterinary, greenhouse, and vehicle transport usage.
Farmers have focused on alternative solutions to mitigate these problems. By raising native plants, they provide food for native bee pollinators like Lasioglossum vierecki[Adamson, Nancy Lee. An Assessment of Non-Apis Bees as Fruit and Vegetable Crop Pollinators in Southwest Virginia . Diss. 2011. Web. 15 October 2015.] leading to less reliance on honey bee populations.
File:Peponapis pruinosaCane-12.JPG| (Apidae) are important pollinators of Cucurbita and .
File:A bee covered with pollen.jpg|A mason bee ( Osmia sp.) covered in pollen
As food producers
Honey is a natural product produced by bees and stored for their own use, but its sweetness has always appealed to humans. Before domestication of bees was even attempted, humans were raiding their nests for their honey. Smoke was often used to subdue the bees and such activities are depicted in Cave painting in Spain dated to 15,000 BC.[
Honey bees are used commercially to produce honey.]
As food
Bees are considered edible insects. People in some countries entomophagy, including the larvae and pupae of bees, mostly stingless species. They also gather larvae, pupae and surrounding cells, known as bee brood, for consumption.[ (This particular Botok recipe uses anchovies, not bees)]
Bee brood (pupae and larvae) although low in calcium, has been found to be high in protein and carbohydrate, and a useful source of phosphorus, magnesium, potassium, and trace minerals iron, zinc, copper, and selenium. In addition, while bee brood was high in fat, it contained no fat soluble vitamins (such as A, D, and E) but it was a good source of most of the water-soluble B vitamins including choline as well as vitamin C. The fat was composed mostly of Saturated fat and monounsaturated fatty acids with 2.0% being polyunsaturated fatty acids.
File:Botoktawon.jpg|Bee larvae as food in the dish botok
File:Fried bees dish.jpg|Fried whole bees served in a Ukrainian restaurant
As alternative medicine
Apitherapy is a branch of alternative medicine that uses honey bee products, including raw honey, royal jelly, pollen, propolis, beeswax and apitoxin (Bee venom).
Stings
The painful Bee sting are mostly associated with the poison gland and the Dufour's gland which are abdominal exocrine glands containing various chemicals. In Lasioglossum leucozonium, the Dufour's Gland mostly contains octadecanolide as well as some eicosanolide. There is also evidence of n-triscosane, n-heptacosane,
See also
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Australian native bees
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Fear of bees (apiphobia)
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Superorganism
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World Bee Day
Explanatory notes
External links
