Bees may be solitary or may live in various types of communities. The most advanced of these are eusocial colonies found among the honey bees, bumblebees, and stingless bees. Sociality, of several different types, is believed to have evolved separately many times within the bees.
In some species, groups of cohabiting females may be sisters, and if there is a division of labor within the group, then they are considered semisocial.
If, in addition to a division of labor, the group consists of a mother and her daughters, then the group is called eusocial. The mother is considered the "queen" and the daughters are "workers". These castes may be purely behavioral alternatives, in which case the system is considered "primitively eusocial" (similar to many paper wasps), and if the castes are morphologically discrete, then the system is "highly eusocial".
There are many more species of primitively eusocial bees than highly eusocial bees, but they have rarely been studied. The biology of most such species is almost completely unknown. The vast majority are in the family Halictidae, or "sweat bees". Colonies are typically small, with a dozen or fewer workers, on average. The only physical difference between queens and workers is average size, if they differ at all. Most species have a single season colony cycle, even in the tropics, and only mated females (future queens, or "gynes") hibernate (called diapause). A few species have long active seasons and attain colony sizes in the hundreds. The orchid bees include a number of primitively eusocial species with similar biology. Certain species of allodapine bees (relatives of carpenter bees) also have primitively eusocial colonies, with unusual levels of interaction between the adult bees and the developing brood. This is "progressive provisioning"; a larva's food is supplied gradually as it develops. This system is also seen in honey bees and some bumblebees.
Highly eusocial bees live in colonies. Each colony has a single queen, many workers and, at certain stages in the colony cycle, drones. When humans provide the nest, it is called a hive. A honey bee hive can contain up to 40,000 bees at their annual peak, which occurs in the spring, but usually have fewer.
Bumblebees
Bumblebees (Bombus terrestris, B. pratorum, et al.) are eusocial in a manner quite similar to the eusocial Vespidae such as hornets. The queen initiates a nest on her own (unlike queens of honey bees and stingless bees which start nests via swarms in the company of a large worker force). 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 nest cavity (pre-existing), and colonies are rarely perennial. Bumblebee queens sometimes seek winter safety in honey bee hives, where they are sometimes found dead in the spring by beekeepers, presumably stung to death by the honey bees. It is unknown whether any survive winter in such an environment.
Bumblebees are one of the more important wild pollinators, but have declined significantly in recent decades. In the UK, 2 species have become nationally extinct during the last 75 years while others have been placed on the UK Biodiversity Action Plan as priority species in recognition of the need for conservation action. In 2006 a new charity, the Bumblebee Conservation Trust, was established in order to coordinate efforts to conserve remaining populations through conservation and education.
Stingless bees
Stingless bees are very diverse in behavior, but all are highly eusocial. They practice mass provisioning, complex nest architecture, and perennial colonies.
Honey bees
The true honey bees (genus Apis) have arguably the most complex social behavior among the bees. The European (or Western) honey bee, Apis mellifera, is the best known bee species and one of the best known of all insects.
Africanized honey bee
Africanized bees, also called killer bees, are a hybrid strain of Apis mellifera derived from experiments to cross European and African honey bees by Warwick Estevam Kerr. Several queen bees escaped his laboratory in South America and have spread throughout the Americas. Africanized honey bees are more defensive than European honey bees.
Solitary and communal bees
Most other bees, including familiar species of bee such as the Eastern carpenter bee (Xylocopa virginica), alfalfa leafcutter bee (Megachile rotundata), orchard mason bee (Osmia lignaria) and the hornfaced bee (Osmia cornifrons) are solitary in the sense that every female is fertile, and typically inhabits a nest she constructs herself. There are no worker bees for these species. Solitary bees typically produce neither honey nor beeswax. They are immune from acarine and Varroa mites (see diseases of the honey bee), but have their own unique parasites, pests and diseases.
Solitary bees are important pollinators, and pollen is gathered for provisioning the nest with food for their brood. Often it is mixed with nectar to form a paste-like consistency. Some solitary bees have very advanced types of pollen carrying structures on their bodies. A very few species of solitary bees are being increasingly cultured for commercial pollination.
Solitary bees are often oligoleges, in that they only gather pollen from one or a few species/genera of plants (unlike honey bees and bumblebees which are generalists). No known bees are nectar specialists; many oligolectic bees will visit multiple plants for nectar, but there are no bees which visit only one plant for nectar while also gathering pollen from many different sources. Specialist pollinators also include bee species that gather floral oils instead of pollen, and male orchid bees, which gather aromatic compounds from orchids (one of the only cases where male bees are effective pollinators). In a very few cases only one species of bee can effectively pollinate a plant species, and some plants are endangered at least in part because their pollinator is dying off. There is, however, a pronounced tendency for oligolectic bees to be associated with common, widespread plants which are visited by multiple pollinators (e.g., there are some 40 oligoleges associated with creosote bush in the US desert southwest,[7] and a similar pattern is seen in sunflowers, asters, mesquite, etc.)
Solitary bees create nests in hollow reeds or twigs, holes in wood, or, most commonly, in tunnels in the ground. 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. Providing nest boxes for solitary bees is increasingly popular for gardeners. Solitary bees are either stingless or very unlikely to sting (only in self defense, if ever).
While solitary females each make individual nests, some species are gregarious, preferring to make nests near others of the same species, giving the appearance to the casual observer that they are social. Large groups of solitary bee nests are called aggregations, to distinguish them from colonies.
In some species, multiple females share a common nest, but each makes and provisions her own cells independently. This type of group is called "communal" and is not uncommon. The primary advantage appears to be that a nest entrance is easier to defend from predators and parasites when there are multiple females using that same entrance on a regular basis.
Cleptoparasitic bees
Cleptoparasitic bees, commonly called "cuckoo bees" because their behavior is similar to cuckoo birds, occur in several bee families, though the name is technically best applied to the apid subfamily Nomadinae. Females of these bees lack pollen collecting structures (the scopa) and do not construct their own nests. They typically enter the nests of pollen collecting species, and lay their eggs in cells provisioned by the host bee. When the cuckoo bee larva hatches it consumes the host larva's pollen ball, and if the female cleptoparasite has not already done so, kills and eats the host larva. In a few cases where the hosts are social species, the cleptoparasite remains in the host nest and lays many eggs, sometimes even killing the host queen and replacing her.
Many cleptoparasitic bees are closely related to, and resemble, their hosts in looks and size, (i.e., the Bombus subgenus Psithyrus, which are parasitic bumblebees that infiltrate nests of species in other subgenera of Bombus). This common pattern gave rise to the ecological principle known as "Emery's Rule". Others parasitize bees in different families, like Townsendiella, a nomadine apid, one species of which is a cleptoparasite of the dasypodaid genus Hesperapis, while the other species in the same genus attack halictid bees.
Nocturnal bees
Four bee families (Andrenidae, Colletidae, Halictidae, and Apidae) contain some species that are crepuscular (these may be either the vespertine or matinal type). These bees have greatly enlarged ocelli, which are extremely sensitive to light and dark, though incapable of forming images. Many are pollinators of flowers that themselves are crepuscular, such as evening primroses, and some live in desert habitats where daytime temperatures are extremely high.
Bee flight
In his 1934 French book Le vol des insectes, M. Magnan wrote that he and a Mr. Saint-Lague had applied the equations of air resistance to bumblebees 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".[8] This has led to a common misconception that bees "violate aerodynamic theory", but 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 helicopters.[9]
In 1996 Charlie Ellington at Cambridge University showed that vortices created by many insects’ wings and non-linear effects were a vital source of lift;[10] vortices and non-linear phenomena are notoriously difficult areas of hydrodynamics, which has made for slow progress in theoretical understanding of insect flight.
In 2005 Michael Dickinson and his Caltech colleagues studied honey bee flight with the assistance of high-speed cinematography[11] and a giant robotic mock-up of a bee wing.[12] Their analysis revealed sufficient 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 fruitfly (200 times per second) which is 80 times smaller.[13]
In 2008 Barbara Shipman discovered a mathematical connection between the dance of bees and the Flag manifold.[14]
Bees and humans
Bees figure prominently in mythology and have been used by political theorists as a model for human society. Journalist Bee Wilson states that the image of a community of honey bees "occurs from ancient to modern times, in Aristotle and Plato; in Virgil and Seneca; in Erasmus and Shakespeare; Tolstoy, as well as by social theorists Bernard Mandeville and Karl Marx."[15]
Despite the honey bee's painful sting and the stereotype of insects as pests, bees are generally held in high regard. This is most likely due to their usefulness as pollinators and as producers of honey, their social nature, and their reputation for diligence. Bees are one of the few insects regularly used on advertisements, being used to illustrate honey and foods made with honey (such as Honey Nut Cheerios).
In North America, yellowjackets and hornets, especially when encountered as flying pests, are often misidentified as bees, despite numerous differences between them - see Characteristics of common wasps and bees. Although a bee sting can be deadly to those with allergies, virtually all bee species are non-aggressive if undisturbed and many cannot sting at all. Humans are often a greater danger to bees, as bees can be affected or even harmed by encounters with toxic chemicals in the environment - see Bees and toxic chemicals.
In Indonesia bee larvae are eaten as accompanion to rice, after mixed with shredded coconut "meat", wrapped in banana leaves, and steamed.
Gallery
 Bumble bee and honey bee |  European honey bee, Poland |  European honey bee on a Sphaeralcea flower. Mesa, Az |  European honey bee in a Sphaeralcea flower. Mesa, Az |  Sweat bee, Agapostemon virescens (female) on a Coreopsis flower. Madison, Wi |
 Bumblebee, Bombus sp. startles Agapostemon virescens. Madison, Wi |  European honey bee |  European honey bee, Kaunakakai, HI |  European honey bees, Lebanon. |  European honey bee, Lebanon. |
 European honey bee collecting pollen from a rose. |  European honey bee collecting nectar from small flowers. McKinney, Texas. |  Hovering bumblebee at lupine |  European honey bee on Apple blossom |  Bumblebee, Montreal |
 Euglossine bees on orchid Mormodes buccinator (Suriname) |  Bumble bee targeting apple blossom in Calgary, Alberta |  European honey bee |  European honey bee on tufted vetch (Vicia cracca) (Quebec, Canada) |  Honey bee approaching a milk thistle flower |
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