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Bee

Source: Wikipedia, the free encyclopedia.

Bees
Temporal range:
Ma
Tetragonula carbonaria (14521993792).jpg
The sugarbag bee, Tetragonula carbonaria
Scientific classification e
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Hymenoptera
(unranked):
Unicalcarida
Suborder: Apocrita
Superfamily: Apoidea
Clade: Anthophila
Families
Synonyms

Apiformes (from Latin 'apis')

Bees are winged insects closely related to wasps and ants, known for their roles in pollination and, in the case of the best-known bee species, the western honey bee, for producing honey. Bees are a monophyletic lineage within the superfamily Apoidea. They are presently considered a clade, called Anthophila. There are over 16,000 known species of bees in seven recognized biological families.[1][2] Some species – including honey bees, bumblebees, and stingless bees – live socially in colonies while most species (>90%) – including mason bees, carpenter bees, leafcutter bees, and sweat bees – are solitary.

Bees are found on every continent except Antarctica, in every habitat on the planet that contains insect-pollinated flowering plants. 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 2 millimetres (0.08 in) long,[3] to Megachile pluto, the largest species of leafcutter bee, whose females can attain a length of 39 millimetres (1.54 in).

Bees feed on

primates and birds such as bee-eaters; insect predators include beewolves and dragonflies
.

Bee pollination is important both ecologically and commercially, and the decline in wild bees has increased the value of 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.[4]

Human

Mayans have practiced large-scale intensive meliponiculture since pre-Columbian times.[3]

Evolution

The immediate ancestors of bees were stinging wasps in the family Crabronidae, which were predators of other insects. The switch from insect prey to pollen may have resulted from the consumption of prey insects which were flower visitors and were partially covered with pollen when they were fed to the wasp larvae. This same evolutionary scenario may have occurred within the vespoid wasps, where the pollen wasps evolved from predatory ancestors. The oldest non-compression bee fossil is found in New Jersey amber, Cretotrigona prisca, a corbiculate bee of Cretaceous age (~65 mya).[5] A fossil from the early Cretaceous (~100 mya), Melittosphex burmensis, was initially considered "an extinct lineage of pollen-collecting Apoidea sister to the modern bees",[6] but subsequent research has rejected the claim that Melittosphex is a bee, or even a member of the superfamily Apoidea to which bees belong, instead treating the lineage as incertae sedis within the Aculeata.[7] By the Eocene (~45 mya) there was already considerable diversity among eusocial bee lineages.[8][a]

The highly eusocial corbiculate Apidae appeared roughly 87 Mya, and the Allodapini (within the Apidae) around 53 Mya.[11] The Colletidae appear as fossils only from the late Oligocene (~25 Mya) to early Miocene.[12] The Melittidae are known from Palaeomacropis eocenicus in the Early Eocene.[13] The Megachilidae are known from trace fossils (characteristic leaf cuttings) from the Middle Eocene.[14] The Andrenidae are known from the Eocene-Oligocene boundary, around 34 Mya, of the Florissant shale.[15] The Halictidae first appear in the Early Eocene[16] with species[17][18] found in amber. The Stenotritidae are known from fossil brood cells of Pleistocene age.[19]

Coevolution

Long-tongued bees and long-tubed flowers coevolved, like this Amegilla cingulata (Apidae) on Acanthus ilicifolius
.

The earliest animal-pollinated flowers were shallow, cup-shaped blooms

acarinaria that appear to provide lodgings for mites; in return, it is believed that mites eat fungi that attack pollen, so the relationship in this case may be mutualistic.[22][23]

Phylogeny

External

This

Heterogynaidae is uncertain.[24] The small subfamily Mellininae
was not included in this analysis.

Apoidea

Emerald Cockroach Wasp.JPG

Heterogynaidae
(possible placement #1)

sensu stricto) Sceliphron spirifex TZ edit1.jpg

Ectemnius.lapidarius.-.lindsey.jpg

(rest of "Crabronidae")

Bembix sp2.jpg

Astata boops a1.jpg

Heterogynaidae
(possible placement #2)

P. gibbosus57306787w.jpg

Anthophila (bees) Abeille butineuse et son pollen.JPG

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.[25] English names, where available, are given in parentheses.

Anthophila
 (bees)

Macropis sp 01.jpg

long-tongued bees

Apis mellifera flying2.jpg

Leafcutter bee (Megachile sp.) collecting leaves (7519316920).jpg

short-tongued bees

Thomas Bresson - Hyménoptère sur une fleur de pissenlit (by).jpg

Iridescent.green.sweat.bee1.jpg

Colletes cunicularius m1.JPG

Stenotritus pubescens, f, side, australia 2014-07-05-12.18.33 ZS PMax.jpg

Characteristics

Bees differ from closely related groups such as wasps by having branched or plume-like setae (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.[26]

Bees have the following characteristics:

  • A pair of large
    ocelli
    ) which provide information on light intensity.
  • 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.
  • The mouthparts are adapted for both chewing and sucking by having both a pair of mandibles and a long proboscis for sucking up nectar.[27]
  • 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 synchronised 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.
  • The abdomen has nine segments, the hindermost three being modified into the sting.[27]

The largest species of bee is thought to be Wallace's giant bee

Meliponini whose workers are less than 2 millimetres (0.08 in) in length.[29]

Sociality

Haplodiploid breeding system

According to

haplodiploid species such as bees because of their unusual relatedness structure.[30]

In haplodiploid species, females develop from fertilized eggs and males from unfertilized eggs. Because a male is

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.[31] Workers often do not reproduce, but they can pass on more of their genes by helping to raise their sisters (as queens) than they would by having their own offspring (each of which would only have 50% of their genes), assuming they would produce similar numbers. This unusual situation has been proposed as an explanation of the multiple (at least 9) evolutions of eusociality within Hymenoptera.[32][33]

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.[34] But, monogamy (queens mating singly) is the ancestral state for all eusocial species so far investigated, so it is likely that haplodiploidy contributed to the evolution of eusociality in bees.[32]

Eusociality

Western honey bee nest in the trunk of a spruce

Bees may be solitary or may live in various types of communities.

semisocial. The group is called eusocial if, in addition, the group consists of a mother (the queen) and her daughters (workers). When the castes are purely behavioural alternatives, with no morphological differentiation other than size, the system is considered primitively eusocial, as in many paper wasps; when the castes are morphologically discrete, the system is considered highly eusocial.[21]

True honey bees (genus

Apis mellifera, native to Europe, the Middle East, and Africa. Africanized bees are a hybrid strain of A. mellifera that escaped from experiments involving crossing European and African subspecies; they are extremely defensive.[37]

eusocial. They practise mass provisioning, with complex nest architecture and perennial colonies also established via swarming.[3][38]

A bumblebee carrying pollen in its pollen baskets
(corbiculae)

Many bumblebees are eusocial, similar to the eusocial Vespidae such as hornets 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.[39] In 2011, the International Union for Conservation of Nature set up the Bumblebee Specialist Group to review the threat status of all bumblebee species worldwide using the IUCN Red List criteria.[40]

There are many more species of primitively eusocial than highly eusocial bees, but they have been studied less often. Most are in the family

orchid bees (Apidae) include some primitively eusocial species with similar biology. Some allodapine bees (Apidae) form primitively eusocial colonies, with progressive provisioning: a larva's food is supplied gradually as it develops, as is the case in honey bees and some bumblebees.[44]

Solitary and communal bees

Most other bees, including familiar insects such as

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 pollen wasps have similar behaviours, and a few species of bee scavenge from carcases to feed their offspring.[26] 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 genera which are commonly known by their nesting behavior or preferences, namely: carpenter bees, sweat bees, mason bees, plasterer bees, squash bees, dwarf carpenter bees, leafcutter bees, alkali bees and digger bees.[45]

A solitary bee, Anthidium florentinum (family Megachilidae), visiting Lantana

Most solitary bees are fossorial, digging nests in the ground in a variety of soil textures and conditions, while others create nests in hollow reeds 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.[46][47]

While solitary, females each make individual nests.[48] Some species, such as the European mason bee Hoplitis anthocopoides,[49] and the Dawson's Burrowing bee, Amegilla dawsoni,[50] are gregarious, preferring to make nests near others of the same species, and giving the appearance of being 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 multiple females use that same entrance regularly.[49]

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 pupation stage during which the insect undergoes complete metamorphosis, followed by the emergence of a winged adult. 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. The sex of a bee is determined by whether or not the egg is fertilised; after mating, a female stores the sperm, and determines which sex is required at the time each individual egg is laid, fertilised eggs producing female offspring and unfertilised eggs, males. Tropical bees may have several generations in a year and no diapause stage.[51][52][53][54]

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.[55]

In most species, larvae are whitish grubs, roughly oval and bluntly-pointed at both ends. They have 15 segments and

exuviae and breaks out of the cell.[55]

Flight

Honeybee in flight carrying pollen in pollen basket

arc, it flaps approximately 230 times per second, faster than a fruitfly (200 times per second) which is 80 times smaller.[61]

Navigation, communication, and finding food

Karl von Frisch (1953) discovered that honey bee workers can navigate, indicating the range and direction to food to other workers with a waggle dance
.

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.[62] Bees navigate using spatial memory with a "rich, map-like organization".[63]

Digestion

The gut of bees is relatively simple, but multiple metabolic strategies exist in the gut microbiota.[64] Pollinating bees consume nectar and pollen, which require different digestion strategies by somewhat specialized bacteria. While nectar is a liquid of mostly monosaccharide sugars and so easily absorbed, pollen contains complex polysaccharides: branching pectin and hemicellulose.[65] Approximately five groups of bacteria are involved in digestion. Three groups specialize in simple sugars (Snodgrassella and two groups of Lactobacillus), and two other groups in complex sugars (Gilliamella and Bifidobacterium). Digestion of pectin and hemicellulose is dominated by bacterial clades Gilliamella and Bifidobacterium respectively. Bacteria that cannot digest polysaccharides obtain enzymes from their neighbors, and bacteria that lack certain amino acids do the same, creating multiple ecological niches.[66]

Although most bee species are nectarivorous and palynivorous, some are not. Particularly unusual are vulture bees in the genus Trigona, which consume carrion and wasp brood, turning meat into a honey-like substance.[67]

Ecology

Floral relationships

Most bees are polylectic (generalist) meaning they collect pollen from a range of flowering plants, but some are

oligoleges (specialists), in that they only gather pollen from one or a few species or genera of closely related plants.[68] Specialist pollinators also include bee species which gather floral oils instead of pollen, and male orchid bees, which gather aromatic compounds from orchids (one of the few cases where male bees are effective pollinators). Bees are able to sense the presence of desirable flowers through ultraviolet patterning on flowers, floral odors,[69] and even electromagnetic fields.[70] Once landed, a bee then uses nectar quality[69] and pollen taste[71]
to determine whether to continue visiting similar flowers.

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.[72]

As mimics and models

Batesian mimic
of bees, taking nectar and pollinating a flower.

Many bees are

hoverflies,[73] all of which gain a measure of protection by superficially looking and behaving like bees.[73]

Bees are themselves Müllerian mimics of other aposematic insects with the same colour scheme, including wasps, lycid 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 recognised warning coloration.[74]

Bees are also mimicked by plants such as the bee orchid 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.[75]

As brood parasites

Brood parasites occur in several bee families including the apid subfamily Nomadinae.[76] Females of these species 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 often the host egg also.[77] In particular, the Arctic bee species, Bombus hyperboreus is an aggressive species that attacks and enslaves other bees of the same subgenus. However, unlike many other bee brood parasites, they have pollen baskets and often collect pollen.[78]

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.[79]

The

dasypodaid genus Hesperapis,[80] while the other species in the same genus attacks halictid bees.[81]

Nocturnal bees

Four bee families (

ocelli, 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.[82]

Predators, parasites and pathogens

Merops apiaster
, specialises in feeding on bees; here a male catches a nuptial gift for his mate.