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A bumblebee (or bumble bee, bumble-bee, or humble-bee) is any of over 250 species in the genus Bombus, part of Apidae, one of the bee families. This genus is the only Extant taxon group in the tribe Bombini, though a few extinct related genera (e.g., Calyptapis) are known from . They are found primarily in the Northern Hemisphere, although they are also found in South America, where a few lowland tropical species have been identified. European bumblebees have also been introduced to New Zealand and Tasmania. Female bumblebees can sting repeatedly, but generally ignore humans and other animals.
Most bumblebees are eusociality insects that form colonies with a single queen. The colonies are smaller than those of , growing to as few as 50 individuals in a nest. Psithyrus are brood parasite and do not make nests or form colonies; their queens aggressively invade the nests of other bumblebee species, kill the resident queens and then lay their own eggs, which are cared for by the resident workers. Cuckoo bumblebees were previously classified as a separate genus, but are now usually treated as members of Bombus.
Bumblebees have round bodies covered in soft hair (long branched ) called 'pile', making them appear and feel fuzzy. They have aposematism, often consisting of contrasting bands of colour, and different species of bumblebee in a region often resemble each other in mutually protective Müllerian mimicry. Harmless insects such as Hoverfly often derive protection from resembling bumblebees, in Batesian mimicry, and may be confused with them. Nest-making bumblebees can be distinguished from similarly large, fuzzy cuckoo bumblebees by the form of the female hind leg. In nesting bumblebees, it is modified to form a pollen basket, a bare shiny area surrounded by a fringe of hairs used to transport pollen, whereas in cuckoo bumblebees, the hind leg is hairy all around, and they never carry pollen.
Like their relatives the honeybees, bumblebees feed on nectar, using their long hairy tongues to lap up the liquid; the proboscis is folded under the head during flight. Bumblebees gather nectar to add to the stores in the nest, and pollen to feed their young. They forage using colour and spatial relationships to identify flowers to feed from. Some bumblebees nectar robbing, making a hole near the base of a flower to access the nectar while avoiding pollen transfer. Bumblebees are important agricultural , so their decline in Europe, North America, and Asia is a cause for concern. The decline has been caused by habitat loss, the mechanisation of agriculture, and .
Charles Darwin referred to bumblebees as "humble-bees" in his 1859 book On the Origin of Species, emphasising their importance in pollinating clovers and other wildflowers. The term humblebee remained in use through the nineteenth century, but was gradually replaced by bumblebee in both scientific and common language during the twentieth century.
Early analyses of morphology and behaviour suggested that complex eusociality evolved twice within the corbiculate bees, once in the ancestor of the Apini and once in the Meliponini. Molecular and morphological data indicate that the primitively eusocial Bombini are, despite appearances, closely related to the Meliponini, while the Apini and Euglossini form a separate branch. Cardinal and Danforth (2011) described this dual-origin model as consistent with earlier evidence from social and anatomical traits.
More recent phylogenomic studies based on the mRNA expression profile from more than 3,600 genes support instead a single origin of eusociality within the corbiculate bees. Romiguier et al. (2015) found that the Bombini, Meliponini, and Apini form a single clade, with Euglossini as their sister group, implying that advanced social organisation arose once in the common ancestor of these three tribes.
Revisiting the "corbiculate controversy", on the mismatch between morphological and molecular analyses in 2021, Diego Sasso Porto and Eduardo A. B. Almeida find that morphological analysis still suggests that Bombini are sister to a clade containing Apini and Meliponini, as shown in the phylogenetic tree. They propose "a more conciliatory" scenario involving "a diversification followed by several extinctions" so that Meliponini and Bombini shared "few apomorphic changes", while the similarities between Meliponini and Apini could be convergent evolution caused by "similar biology or similar eusocial behaviors".
The earliest divergence estimates suggest that the Bombini originated between 25 and 40 million years ago, whereas the Bombini–Meliponini clade dates to roughly 80–95 million years ago, around the time the corbiculate group as a whole diversified.
Several Oligocene and Miocene species have been assigned to modern subgenera, including Bombus (Mendacibombus) beskonakensis and B. (Paraelectrobombus) patriciae from Turkey, B. randeckensis from Germany, B. cerdanyensis from Spain, and B. trophonius from the Czech Republic.
These fossils indicate that the major subgenera of Bombus were already differentiated by the Miocene and that diversification of the tribe was well underway by the Oligocene.
At the northern limits of their range, species such as Bombus polaris, B. alpinus, and the parasitic B. hyperboreus occupy Arctic tundra ecosystems that extend as far north as Greenland and Canada's Ellesmere Island. These populations endure some of the planet's shortest flowering seasons and coldest conditions, marking the northernmost boundary of Eusociality insect life.
Many species of Bombus, including the Psithyrus group of cuckoo bumblebees, have evolved a form of Müllerian mimicry. This is a system in which different bumblebee species within the same region share similar warning color patterns, so that a predator only has to learn once to avoid any of them. In California, for example, several largely black species like B. californicus, B. caliginosus, B. vandykei, B. vosnesenskii, B. insularis, and B. fernaldae, form one such mimicry group. Another group in the same region includes species banded in black and yellow. In both cases, the shared coloration gives all members of the group a selective advantage.
Parasitic, or cuckoo, bumblebees also tend to resemble their hosts more closely than would be expected by chance, especially in regions such as Europe where parasite and host species have evolved together. This resemblance is likely another case of Müllerian mimicry, rather than a strategy to deceive the host through aggressive mimicry.Fisher, R. M. & Sampson, J. (1992). "Mimetic coevolution between cuckoo bumblebees and their hosts". Evolution. 46 (3): 775–783.
Unlike the well-known "dance" communication of honeybees, bumblebees do not perform a spatial waggle or round dance to indicate the location of food sources. Instead, when a forager returns from a successful trip to the nest, it often moves rapidly and excitedly around the nest for several minutes before departing again to forage.
Bumblebees have also been observed to engage in social learning. In experiments with Bombus terrestris, workers were trained to solve a novel task (string-pulling) to obtain a reward, and naïve individuals that observed trained demonstrators were significantly more successful than those that did not. Furthermore, subsequent work showed that novel problem-solving behaviours can spread through bumblebee colonies via social learning under open-diffusion conditions.
In the early spring, the queen comes out of diapause and finds a suitable place to create her colony. Then she builds wax cells in which to lay her eggs which were fertilised the previous year. The eggs that hatch develop into female workers, and in time, the queen populates the colony, with workers feeding the young and performing other duties similar to honeybee workers. In temperate zones, young queens () leave the nest in the autumn and mating, often more than once, with males (drones) that are forcibly driven out of the colony. The drones and workers die as the weather turns colder; the young queens feed intensively to build up stores of fat for the winter. They survive in a resting state (diapause), generally below ground, until the weather warms up in the spring with the early bumblebee being the species that is among the first to emerge. Many species of bumblebee follow this general trend within the year. Bombus pensylvanicus is a species that follows this type of colony cycle. For this species the cycle begins in February, reproduction starts in July or August, and ends in the winter months. The queen remains in hibernation until spring of the following year in order to optimize conditions to search for a nest.
In fertilised queens, the ovaries only become active when the queen starts to lay. An egg passes along the oviduct to the vagina where there is a chamber called the spermatheca, in which the sperm from the mating is stored. Depending on need, she may allow her egg to be fertilised. Unfertilised eggs become haploid males; fertilised eggs grow into diploid females and queens. The that stimulate the development of the ovaries are suppressed in female worker bees, while the queen remains dominant.
To develop, the must be fed both nectar for and pollen for protein. Bumblebees feed nectar to the larvae by chewing a small hole in the brood cell into which they regurgitate nectar. Larvae are fed pollen in one of two ways, depending on the bumblebee species. Pocket-making bumblebees create pockets of pollen at the base of the brood-cell clump from which the larvae feed themselves. Pollen-storing bumblebees keep pollen in separate wax pots and feed it to the larvae.
After the emergence of the first or second group of offspring, workers take over the task of foraging and the queen spends most of her time laying eggs and caring for larvae. The colony grows progressively larger and eventually begins to produce males and new queens. Bumblebee workers can lay unfertilised haploid eggs (with only a single set of ) that develop into viable male bumblebees. Only fertilised queens can lay diploid eggs (one set of chromosomes from a drone, one from the queen) that mature into workers and new queens.
In a young colony, the queen minimises reproductive competition from workers by suppressing their egg-laying through physical aggression and . Worker policing leads to nearly all eggs laid by workers being eaten. Thus, the queen is usually the mother of all of the first males laid. Workers eventually begin to lay male eggs later in the season when the queen's ability to suppress their reproduction diminishes. Because of the reproductive competition between workers and the queen, bumblebees are considered "primitively eusocial".
Although a large majority of bumblebees follow such monogynous colony cycles that only involve one queen, some select Bombus species (such as Bombus pauloensis) will spend part of their life cycle in a polygynous phase (have multiple queens in one nest during these periods of polygyny).
Bumblebees use a combination of colour and spatial relationships to learn which flowers to forage from. They can also electroreception both the presence and the pattern of electric fields on flowers, which occur due to atmospheric electricity, and take a while to leak away into the ground. They use this information to find out if a flower has been recently visited by another bee.
Bumblebees can detect the temperature of flowers, as well as which parts of the flower are hotter or cooler and use this information to recognise flowers. After arriving at a flower, they extract nectar using their long tongues ("Tongue") and store it in their crops. Many species of bumblebees also exhibit "nectar robbing": instead of inserting the mouthparts into the flower in the normal way, these bees bite directly through the base of the corolla to extract nectar, avoiding pollen transfer.
Pollen is removed from flowers deliberately or incidentally by bumblebees. Incidental removal occurs when bumblebees come in contact with the stamen of a flower while collecting nectar. When it enters a flower, the bumblebee's body hairs receive a dusting of pollen from the anthers. In queens and workers this is then groomed into the Pollen basket (pollen baskets) on the hind legs where it can be seen as bulging masses that may contain as many as a million pollen grains. Male bumblebees do not have corbiculae and do not purposively collect pollen. Bumblebees are also capable of buzz pollination, in which they dislodge pollen from the anthers by creating a resonance with their flight muscles.
In at least some species, once a bumblebee has visited a flower, it leaves a scent mark on it. This scent mark deters bumblebees from visiting that flower until the scent degrades. This scent mark is a general chemical bouquet that bumblebees leave behind in different locations (e.g. nest, neutral, and food sites), and they learn to use this bouquet to identify both rewarding and unrewarding flowers, and may be able to identify who else has visited a flower. Bumblebees rely on this chemical bouquet more when the flower has a high handling time, that is, where it takes a longer time for the bee to find the nectar once inside the flower.
Once they have collected nectar and pollen, female workers return to the nest and deposit the harvest into brood cells, or into wax cells for storage. Unlike honeybees, bumblebees only store a few days' worth of food, so are much more vulnerable to food shortages. Male bumblebees collect only nectar and do so to feed themselves. They may visit quite different flowers from the workers because of their different nutritional needs.
The female Psithyrus has a number of morphological adaptations for combat, such as larger mandibles, a tough cuticle and a larger venom sac that increase her chances of taking over a nest. Upon emerging from their cocoons, the Psithyrus males and females disperse and mate. The males do not survive the winter but, like nonparasitic bumblebee queens, Psithyrus females find suitable locations to spend the winter and enter diapause after mating. They usually emerge from hibernation later than their host species. Each species of cuckoo bumblebee has a specific host species, which it may physically resemble. In the case of the parasitism of B. terrestris by B. (Psithyrus) vestalis, genetic analysis of individuals captured in the wild showed that about 42% of the host species' nests at a single location had "lost their fight against their parasite".
The great grey shrike is able to detect flying bumblebees up to away; once captured, the sting is removed by repeatedly squeezing the insect with the mandibles and wiping the abdomen on a branch. (1993). 9780198575108, RSPB / Oxford University Press. ISBN 9780198575108 The European honey buzzard follows flying bees back to their nest, digs out the nest with its feet, and eats larvae, pupae and adults as it finds them.
Bumblebees are parasitised by tracheal mites, Locustacarus buchneri; including Crithidia bombi and Apicystis bombi; and including Nosema bombi and Nosema ceranae. The tree bumblebee Bombus hypnorum has spread into the United Kingdom despite hosting high levels of a nematode that normally interferes with queen bees' attempts to establish colonies." Parasites fail to halt European bumblebee invasion of the UK ", Bumblebee Conservation Trust (retrieved 6 February 2015) Deformed wing virus has been found to affect 11% of bumblebees in Great Britain." New study shows how bumblebees can be infected by honeybee diseases ", Bumblebee Conservation Trust (retrieved 6 February 2015)
Female bee moths ( Aphomia sociella) prefer to lay their eggs in bumblebee nests. The A. sociella larvae will then feed on the eggs, larvae, and pupae left unprotected by the bumblebees, sometimes destroying large parts of the nest.
Bumblebees are Northern Hemisphere animals. When red clover was introduced as a crop to New Zealand in the nineteenth century, it was found to have no local pollinators, and clover seed had accordingly to be imported each year. Four species of bumblebee from the United Kingdom were therefore imported as pollinators. In 1885 and 1886, the Canterbury Acclimatization Society brought in 442 queens, of which 93 survived and quickly multiplied. As planned, red clover was soon being produced from locally-grown seed. Bumblebees are also reared commercially to pollinate tomatoes grown in . The New Zealand population of buff-tailed bumblebees began colonising Tasmania, away, after being introduced there in 1992 under unclear circumstances.
Some concerns exist about the impact of the international trade in mass-produced bumblebee colonies. Evidence from Japan and South America indicates bumblebees can escape and naturalise in new environments, causing damage to native pollinators. Greater use of native pollinators, such as Bombus ignitus in China and Japan, has occurred as a result. In addition, mounting evidence indicates mass-produced bumblebees may also carry diseases, harmful to wild bumblebees
and honeybees.
In Canada and Sweden, it has been shown that growing a mosaic of different crops encourages bumblebees and provides higher yields than does a monoculture of oilseed rape, despite the fact that the bees were attracted to the crop.
Bumblebees are in danger in many developed countries due to habitat destruction and collateral pesticide damage. The European Food Safety Authority ruled that three neonicotinoid pesticides (clothianidin, imidacloprid, and thiamethoxam) presented a high risk for bees. While most work on neonicotinoid toxicity has looked at honeybees, a study on B. terrestris showed that "field-realistic" levels of imidacloprid significantly reduced growth rate and cut production of new queens by 85%, implying a "considerable negative effect" on wild bumblebee populations throughout the developed world. Another study on B. terrestris had results suggesting that use of neonicotinoid pesticides can affect how well bumblebees are able to forage and pollinate. Foragers from bee colonies that had been affected by the pesticide took longer to learn to manipulate flowers and visited flowers with less nutritious pollen. In another study, chronic exposure in a laboratory setting to field-realistic levels of the neonicotinoid pesticide thiamethoxam did not affect colony weight gain or the number or mass of sexuals produced. Low levels of neonicotinoids can reduce the number of bumblebees in a colony by as much as 55%, and cause dysfunction in the bumblebees' brains. The Bumblebee Conservation Trust considers this evidence of reduced brain function "particularly alarming given that bumblebees rely upon their intelligence to go about their daily tasks." Research was published in the Journal of the Federation of American Societies for Experimental Biology by Chris Connolly and others.
Of 19 species of native nestmaking bumblebees and six species of cuckoo bumblebees formerly widespread in Britain, three have been extirpated, eight are in serious decline, and only six remain widespread. Similar declines have been reported in Ireland, with four species designated endangered, and another two considered vulnerable to extinction. A decline in bumblebee numbers could cause large-scale changes to the countryside, resulting from inadequate pollination of certain plants.
Some bumblebees native to North America are also vanishing, such as Bombus balteatus, Bombus terricola, Bombus affinis, and Bombus occidentalis; one, Bombus franklini, may be extinct. In South America, Bombus bellicosus was Local extinction in the northern limit of its distribution range, probably due to intense land use and climate change effects.
The world's first bumblebee sanctuary was established at Vane Farm in the Loch Leven National Nature Reserve in Scotland in 2008. In 2011, London's Natural History Museum led the establishment of an International Union for Conservation of Nature Bumblebee Specialist Group, chaired by Dr. Paul H. Williams, to assess the threat status of bumblebee species worldwide using Red List criteria.
Bumblebee conservation is in its infancy in many parts of the world, but with the realization of the important part they play in pollination of crops, efforts are being made to manage farmland better. Enhancing the wild bee population can be done by the planting of wildflower strips, and in New Zealand, bee nesting boxes have achieved some success, perhaps because there are few burrowing mammals to provide potential nesting sites in that country.
The origin of this claim has been difficult to pin down with any certainty. John H. McMasters recounted an anecdote about an unnamed Swiss aerodynamicist at a dinner party who performed some rough calculations and concluded, presumably in jest, that according to the equations, bumblebees cannot fly. cited in
In later years, McMasters backed away from this origin, suggesting there could be multiple sources, and stating that the earliest he had found was a reference in the 1934 book Le Vol des Insectes by French entomologist Antoine Magnan (1881–1938). Magnan had applied the equations of air resistance to insects, giving the result that their flight would be impossible, but "One shouldn't be surprised that the results of the calculations don't square with reality". The following passage appears in the introduction to Le Vol des Insectes:
Magnan refers to his assistant André Sainte-Laguë."The bumblebee story can be traced back to a 1934 book by entomologist Antoine Magnan, who refers to a calculation by his assistant André Sainte-Laguë, who was an engineer. The conclusion was presumably based on the fact that the maximum possible lift produced by aircraft wings as small as a bumblebee's wings and traveling as slowly as a bee in flight would be much less than the weight of a bee." Some credit physicist Ludwig Prandtl (1875–1953) of the University of Göttingen in Germany with popularizing the idea. Others say Swiss gas dynamicist Jakob Ackeret (1898–1981) did the calculations.
The calculations that purported to show that bumblebees cannot fly are based upon a simplified linear treatment of oscillating airfoil. The method assumes small amplitude oscillations without flow separation. This ignores the effect of dynamic stall (an airflow separation inducing a large vortex above the wing), which briefly produces several times the lift of the aerofoil in regular flight. More sophisticated aerodynamic analysis shows the bumblebee can fly because its wings encounter dynamic stall in every oscillation cycle.
The evolutionary biologist John Maynard Smith pointed out that bumblebees would not be expected to sustain flight, as they would need to generate too much power given their tiny wing area. However, in aerodynamics experiments with other insects, he found that viscosity at the scale of small insects meant even their small wings can move a very large volume of air relative to their size, and this reduces the power required to sustain flight by an order of magnitude.
In 1599, during the reign of Queen Elizabeth I, someone, possibly Tailboys Dymoke, published Caltha Poetarum: Or The Bumble Bee, under the pseudonym "T. Cutwode". This was one of nine books censorship under the Bishops' Ban issued by the Archbishop of Canterbury John Whitgift and the Bishop of London Richard Bancroft.
Emily Dickinson made a bumblebee the subject of her parody of Isaac Watts's well-known poem about honeybees, "How Doth the Little Busy Bee" (1715). Where Watts wrote "How skilfully she builds her cell! How neat she spreads the wax!", Dickinson's poem, "The Bumble-Bee's Religion" (1881), begins "His little Hearse-like Figure / Unto itself a Dirge / To a delusive Lilac / The vanity divulge / Of Industry and Morals / And every righteous thing / For the divine Perdition / of Idleness and Spring." The letter is said to have enclosed a dead bee.
In 1847, Ralph Waldo Emerson published his poem "".
The entomologist Otto Plath wrote Bumblebees and Their Ways in 1934. His daughter, the poet Sylvia Plath, wrote a group of poems about bees late in 1962, within four months of her suicide, transforming her father's interest into her poetry.
The scientist and illustrator Moses Harris (1731–1785) painted accurate watercolour drawings of bumblebees in his An Exposition of English Insects Including the Several Classes of Neuroptera, Hymenoptera, & Diptera, or Bees, Flies, & Libellulae (1776–80).
The surname Albus Dumbledore in the Harry Potter series (1997–2007) is an old name for bumblebee. J. K. Rowling said the name "seemed to suit the headmaster, because one of his passions is music and I imagined him walking around humming to himself". J. R. R. Tolkien, in his poem Errantry, used the term Dumbledor for a bumblebee. Among Beatrix Potter's "little books", Babbity Bumble and other members of her nest appear in her 1910 The Tale of Mrs. Tittlemouse.
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