Bumblebee
From Wikipedia, the free encyclopedia
- This article is about the flying insect. For other uses see Bumblebee (disambiguation) or Bombus (disambiguation).
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Bumblebees (also spelled bumble bee, also known as humblebee) are flying insects of the genus Bombus in the family Apidae.
Bumblebees are social insects that are characterized by black and yellow body hairs, often in bands, a commonality among the majority of the species of Bombus. However, some species are known to have orange or even red on their bodies, or may be entirely black.[1] Another obvious (but not unique) characteristic is the soft nature of the long, branched setae, called pile, that covers their entire body, making them appear and feel fuzzy. They are best distinguished from similarly large, fuzzy bees by the form of the female hind leg, which is modified to form a corbicula; a shiny concave surface that is bare but surrounding by a fringe of hairs, used to transport pollen (in similar bees, the hind leg is completely hairy, and pollen grains are wedged into the hairs for transport). Queen and worker bumblebees can sting, but the sting is not barbed like that of the honey bee, so they can sting more than once.[2] Bumblebee species are non-aggressive, but will sting in defense of their nest, or if harmed.
Like their relatives the honey bees, bumblebees feed on nectar and gather pollen to feed their young.
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[edit] Biology
[edit] Anatomy
The blood or hemolymph, as in other arthropods, is carried in an open circulatory system. The body organs, heart, muscles, etc. are surrounded in a reservoir of blood. The heart does pulse blood through its long tube, though, so there is a circulation of sorts. In fertilised queens the ovaries are activated and when the queen lays her egg it passes along the oviduct to the vagina. In the vagina there is a container called the spermatheca. This is where the queen stored sperm from her mating. Before she lays the egg she will decide whether to use sperm from the spermatheca to fertilise it or not. Non-fertilised eggs grow into male bumblebees, and only fertilised eggs grow into females and queens. As in all animals hormones play a big role in the growth and development of the bumblebee. The hormones that stimulate the development of the ovaries are suppressed in the other female worker bees while the queen remains dominant. Salivary glands in the head secrete saliva which is mixed with the nectar and pollen. Saliva is also mixed into the nest materials to soften them.
The bumblebee tongue is specialised to suck up nectar via capillary action. At rest or when flying the tongue is kept inside a sheath and folded under the head and thorax. The abdomen is covered with dorsal tergites and ventral sternites. Wax is secreted between these plates. There are three very important things about bumblebee hair, it is thick, branched and warningly-coloured. Thick hair can act as insulation keeping the bee warm in cold weather. When flying a bee builds up an electrostatic charge, and as the parts of a flower are usually well grounded (the stigma more so than other the flower parts), the pollen is attracted to the bee's hairs when it lands on the flower. When a pollen covered bee enters a flower, because the stigma is better grounded than the other parts of the flower, the charged pollen is preferentially attracted to the stigma.
A bumblebee does not have ears, and it is not known whether or how a bumblebee can hear sound waves passing through the air, however they can feel the vibrations of sounds through wood and other materials. The heart, like that in most other insects, runs down the entire length of the body. The fat body is a nutritional store. Before hibernation queens eat as much as they can to enlarge their fat body. The fat in the cells is used up during hibernation.
[edit] Habitat
Bumblebees are typically found in higher latitudes and/or high altitudes, though exceptions exist (there are a few lowland tropical species). A few species (Bombus polaris and B. arcticus) range into very cold climates where other bees might not be found. One reason for this is that bumblebees can regulate their body temperature, via solar radiation, internal mechanisms of "shivering" and radiative cooling from the abdomen (called heterothermy). Other bees have similar physiology, but it has been best studied in bumblebees.[3]
[edit] Nests
Bumblebees form colonies. However, their colonies are usually much less extensive than those of honey bees, because of the small physical size of the nest cavity, the fact that a single female is responsible for the initial construction, and the restriction to a single season (in most species). Often, mature bumblebee nests will hold fewer than 50 individuals, and may be within tunnels in the ground made by other animals, or in tussock grass. Bumblebees mostly do not preserve their nests through the winter, though some tropical species live in their nests for several years (and their colonies can grow quite large, depending on the size of the nest cavity). The last generation of summer includes a number of queens who overwinter separately in protected spots. The queens can live up to one year, possibly longer in tropical species.
[edit] Diet
Bumblebees extract nectar from a flower using their long tongue ("glossa") and store it in their crop. Some species (e.g., B. occidentalis and B. affinis) of bumblebee also exhibit what is known as "nectar robbing": instead of inserting the mouthparts into the flower normally, these bees bite directly through the base of the corolla to extract nectar, avoiding pollen transfer. These bees obtain pollen from other species of flowers that they "legitimately" visit.
Pollen is removed from flowers deliberately or incidentally by bumblebees. Incidental removal occurs when bumblebees come in contact with the anthers of a flower while collecting nectar. The bumblebee's body hairs receive a dusting of pollen from the anthers which is then groomed into the corbiculae ("pollen baskets").
Once they have collected nectar and pollen, bumblebees return to the nest and deposit the harvested nectar and pollen into brood cells, or into wax cells for storage. Unlike honey bees, bumblebees only store a few days' worth of food and so are much more vulnerable to food shortages. However, because bumblebees are much more opportunistic feeders than honey bees, these shortages may have less profound effects. Nectar is stored essentially in the form it was collected, rather than being processed into honey as is done in honey bees; it is therefore very dilute and watery, and is rarely consumed by humans.
[edit] "Cuckoo" bumblebees
Bumblebees of the subgenus Psithyrus (known as cuckoo bumblebees, and formerly considered a separate genus) are a lineage which has lost the ability to collect pollen, and are instead cleptoparasitic in the colonies of other bumblebees. Before finding and invading a host colony, a Psithyrus female (there is no caste system in these species) will feed directly from flowers. Once she has infiltrated a host colony, the Psithyrus female will kill or subdue the queen of that colony and forcibly (using pheromones and/or physical attacks) "enslave" the workers of that colony to feed her and her young.
[edit] Reproduction
In temperate zone species, in the autumn, young queens ("gynes") mate with males (drones) and diapause during the winter in a sheltered area, whether in the ground or in a man-made structure. In the early spring, the queen comes out of diapause and finds a suitable place to create her colony, and then builds wax cells in which to lay her fertilized eggs from the previous winter. 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 honey bee workers. New reproductives are produced in autumn, and the queen and workers die, as do the males.
Unlike the workers of more advanced social insects, bumble bee workers are not reproductively sterile. Workers will commonly lay and successfully rear haploid male eggs late in the season. This reproductive competition between workers and the queen is one reason that bumble bees are considered "primitively eusocial".
[edit] Sting
Queen and worker bumblebees sting, but only do so in self-defense or if their nest is disturbed. Female cuckoo bumblebees will aggressively attack host colony members, and sting the host queen, but will ignore other animals (including humans) unless disturbed. See Schmidt Sting Pain Index.
[edit] Bumblebees and people
Bumblebees are important pollinators of both crops and wildflowers.
[edit] Agricultural use
Bumblebees are increasingly cultured for agricultural use as pollinators because they can pollinate plant species that other pollinators cannot by using a technique known as buzz pollination. For example, bumblebee colonies are often emplaced in greenhouse tomato production, because the frequency of buzzing that a bumblebee exhibits effectively releases tomato pollen.[4]
The agricultural use of bumblebees is limited to pollination. Because bumblebees do not overwinter the entire colony, they are not obliged to stockpile honey, and are therefore not useful as honey producers.
[edit] Endangered status
Bumblebees are in danger in many developed countries due to habitat destruction and collateral pesticide damage. In Britain, until relatively recently, 19 species of native true bumblebee were recognised along with six species of cuckoo bumblebees. Of these, three have already become extinct[5] [6], eight are in serious decline and only six remain widespread (numerous species of bumblebees live in Narberth, Pembrokeshire, which is known as the "bumblebee capital of all Wales"). A decline in bumblebee numbers could cause large-scale sweeping changes to the countryside, due to inadequate pollination of certain plants.
In response to this, a new organisation has recently been set up - The Bumblebee Conservation Trust aims to halt these declines through conservation and education (see links).
[edit] In popular culture
- The Flight of the Bumblebee is a famous orchestral interlude written by Nikolai Rimsky-Korsakov for his opera The Tale of Tsar Saltan, composed in 1899-1900.
- The character Bumblebee Man from The Simpsons is a Mexican slapstick comedian who dresses in a bumblebee costume. He is based on El Chapulín Colorado, a famous Mexican comedy character who dresses in a red grasshopper costume.
- In the north-east of Scotland bumblebees are known as 'foggy bummers'.[7]
- Bumblebee of Transformers
[edit] Bumblebee myths
[edit] Flight
According to 20th century folklore, the laws of aerodynamics prove that the bumblebee should be incapable of flight, as it does not have the capacity (in terms of wing size or beat per second) to achieve flight with the degree of wing loading necessary. Not being aware of scientists 'proving' it cannot fly, the bumblebee succeeds under "the power of its own arrogance" (McFadden et. al. 2007). The origin of this myth has been difficult to pin down with any certainty. John 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.[8] In later years McMasters has backed away from this origin, suggesting that there could be multiple sources, and that the earliest he has found was a reference in the 1934 French book Le vol des insectes by M. Magnan. Magnan is reported to have written that he and a Mr. Saint-Lague had applied the equations of air resistance to insects and found that their flight was impossible, but that "One shouldn't be surprised that the results of the calculations don't square with reality".[9]
It is believed[citation needed] that the calculations which purported to show that bumblebees cannot fly are based upon a simplified linear treatment of oscillating aerofoils. 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 that the bumblebee can fly because its wings encounter dynamic stall in every oscillation cycle.
[edit] Buzz
One common, yet incorrect, assumption is that the buzzing sound of bees is caused by the beating of their wings. The sound is the result of the bee vibrating its flight muscles, and this can be done while the muscles are decoupled from the wings, a feature known in bees but not possessed by other insects. This is especially pronounced in bumblebees, as they must warm up their bodies considerably to get airborne at low ambient temperatures.[3] This is how bumblebees can sometimes reach an internal thoracic temperature of 30 degrees Celsius.
[edit] Selected species
- Bombus affinis
- Bombus appositus
- Bombus ashtoni
- Bombus bifarius
- Two-spotted Bumblebee Bombus bimaculatus
- Bombus borealis
- Bombus citrinus
- Cullum's bumblebee, Bombus cullumanus
- Great Yellow bumblebee, Bombus distinguendus
- Golden Northern Bumblebee Bombus fervidus
- Yellow-faced bumblebee Bombus flavifrons
- Bombus fraternus
- Bombus frigidus
- Grey-necked bumblebee Bombus griseocollis
- Small Garden bumblebee, Bombus hortorum
- Frisky bumblebee Bombus impatiens
- Bombus insularis
- Bombus kirbyellus
- Red-tailed bumblebee Bombus lapidarius
- Bombus lucorum
- Orange-rumped Bumblebee Bombus melanopygus
- Blaeberry Bumblebee Bombus monticola[10][11]
- Bombus occidentalis
- Bombus pascuorum
- Bombus pensylvanicus
- Bombus perplexus
- Northern bumblebee Bombus polaris
- Bombus pratorum
- Large Garden bumblebee, Bombus ruderatus
- Bombus rufocinctus
- Short-haired bumblebee, Bombus subterraneus
- Shrill Carder bee, Bombus sylvarum
- Bombus sylvicola
- Orange-belted bumblebee Bombus ternarius
- Buff-Tailed bumblebee, or Large Earth Bumblebee, Bombus terrestris
- Bombus vagans
[edit] Associated parasites
- Tracheal mites - Locustacarus buchneri
- Protozoans- Crithidia bombi
- Microsporidia- Nosema bombi