Bombus polaris
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''Bombus polaris'' is a common Arctic bumblebee species. ''B. polaris'' is one of two
bumblebee 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 group in the tribe Bombini, though a few extinct related genera ...
s that live above the Arctic Circle. The other is its social parasite ''
Bombus hyperboreus ''Bombus hyperboreus'' is a species of Arctic bumblebee with a circumpolar distribution. The species is primarily found in the arctic areas of Greenland, northern Scandinavia, and Russia. In 2015 the nearctic species, '' Bombus natvigi'', was sep ...
''. ''B. polaris'' is a social bee that can survive at near freezing temperatures. It has developed multiple adaptations to live in such cold temperatures. B. polaris has a thicker coat of hair than most bees, utilizes
thermoregulation Thermoregulation is the ability of an organism to keep its body temperature within certain boundaries, even when the surrounding temperature is very different. A thermoconforming organism, by contrast, simply adopts the surrounding temperature ...
, and makes insulated nests.


Taxonomy and phylogeny

''Bombus polaris'' is part of the family Apidae, which is part of the larger class of Insecta. Apidae is the largest family of bees, including several species of bees used by humans for honey consumption. ''B. polaris'' is part of the subgenus '' Alpinobombus'' along with '' Bombus alpinus'', '' Bombus balteatus'', ''
Bombus hyperboreus ''Bombus hyperboreus'' is a species of Arctic bumblebee with a circumpolar distribution. The species is primarily found in the arctic areas of Greenland, northern Scandinavia, and Russia. In 2015 the nearctic species, '' Bombus natvigi'', was sep ...
'', and '' Bombus neoboreus''. ''Alpinobombus'' bees occur in arctic and high alpine regions. It is of the
Bombini The Bombini are a tribe of large bristly apid bees which feed on pollen or nectar. Many species are social, forming nests of up to a few hundred individuals; other species, formerly classified as ''Psithyrus'' cuckoo bees, are brood parasites of ...
tribe, which feeds on pollen or nectar.


Description and identification


General appearance

''Bombus polaris'' has a thicker coat of hair than temperate bees in order to slow heat loss. Although the coloration of this bee is variable, the thorax is usually black with orange-yellow edges, while most of the abdomen is orange-yellow with a black tip. ''B. polaris'' also has a higher abdominal temperature than its temperate cousins.


Worker appearance

The variation in the color of the pubescence is noticeably variable. The pubescence of the apical dorsal abdominal segments varies from deep rust color to a dull yellow color. There is also a considerable variation in the size of the workers. Some can be scarcely 10 mm in length, while others can be much larger.


Thermoregulation

''B. polaris'' has a bio-mechanical method of bringing its body to a much higher
abdominal The abdomen (colloquially called the belly, tummy, midriff, tucky or stomach) is the part of the body between the thorax (chest) and pelvis, in humans and in other vertebrates. The abdomen is the front part of the abdominal segment of the torso ...
temperature than its temperate relatives. The ability of ''B. polaris'' to fly in deep cold is due to a process called
thermoregulation Thermoregulation is the ability of an organism to keep its body temperature within certain boundaries, even when the surrounding temperature is very different. A thermoconforming organism, by contrast, simply adopts the surrounding temperature ...
, which allows it to raise its internal body temperature up to 38 °C.Sutton, A
The Brief Busy Life of the Arctic Bumblebee.
Alaska Fish and Wildlife News, June 2012.
For this reason ''B. polaris'' is likely to outcompete any temperate bumblebee species that might seek to expand to the northern range.


Nests

The nests are heavily insulated, an important factor in the bees’ energy conservation in the harsh polar environment. At the start of the colony cycle, the lone queen maintains a nest temperature of about 25-30 °C However, when she makes foraging trips at frequent intervals, the temperature of the nest declines. At an air temperature of 10 °C, the nest temperature generally does not decrease lower than 7 °C in the half hour that the queen is
foraging Foraging is searching for wild food resources. It affects an animal's fitness because it plays an important role in an animal's ability to survive and reproduce. Foraging theory is a branch of behavioral ecology that studies the foraging behavi ...
. After all of the sixteen to seventeen larvae of the first brood have developed into workers, the nest temperature is maintained at a steady 35 °C, and the comings and going of the queen and other foragers do not appear to affect it. The nest of ''Bombus polaris'' also appears to have a higher temperature than those of honeybees and
bumblebee 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 group in the tribe Bombini, though a few extinct related genera ...
s from temperate climates.


Structure

First, a fertilized queen must locate a suitable nesting site. After this, she builds a cell to store provisions, and then a hatch camera to house her offspring. ''B. polaris'' queens use a mixture of pollen and wax to build these initial structures. The hatch camera’s construction is soon followed by that of a wax base. On top of this base, the queen deposits a clump of dust covered in flower nectar, subsequently ringed by a wax roller. She then lays her eggs into the clump and covers them with a dust mixture and a wax membrane.


Distribution and habitat

This bumblebee has a wide circumpolar distribution, found in
Canada Canada is a country in North America. Its ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, covering over , making it the world's second-largest country by tot ...
, Arctic
Alaska Alaska ( ; russian: Аляска, Alyaska; ale, Alax̂sxax̂; ; ems, Alas'kaaq; Yup'ik: ''Alaskaq''; tli, Anáaski) is a state located in the Western United States on the northwest extremity of North America. A semi-exclave of the U.S. ...
, Arctic islands ( Devon Island, Ellesmere Island, Baffin Island and
Greenland Greenland ( kl, Kalaallit Nunaat, ; da, Grønland, ) is an island country in North America that is part of the Kingdom of Denmark. It is located between the Arctic and Atlantic oceans, east of the Canadian Arctic Archipelago. Greenland i ...
), northern
Scandinavia Scandinavia; Sámi languages: /. ( ) is a subregion in Northern Europe, with strong historical, cultural, and linguistic ties between its constituent peoples. In English usage, ''Scandinavia'' most commonly refers to Denmark, Norway, and Swe ...
and across Arctic
Russia Russia (, , ), or the Russian Federation, is a transcontinental country spanning Eastern Europe and Northern Asia. It is the largest country in the world, with its internationally recognised territory covering , and encompassing one-eig ...
( Nenets,
Yamalo-Nenets The Yamalo-Nenets Autonomous Okrug (YaNAO; russian: Яма́ло-Не́нецкий автоно́мный о́круг (ЯНАО), ; yrk, Ямалы-Ненёцие автономной ӈокрук, ) or Yamalia (russian: Ямалия) is a fed ...
,
Sakha Sakha, officially the Republic of Sakha (Yakutia),, is the largest republic of Russia, located in the Russian Far East, along the Arctic Ocean, with a population of roughly 1 million. Sakha comprises half of the area of its governing Far Ea ...
and Chukotka). As of 2015, ''B. polaris'' is common and is not listed as endangered. ''Bombus polaris'' is an alpine species. They exclusively live at the summits of mountains. This clear separation between alpine species and subalpine species may be due to superior competition from the subalpine species, leading to a suboptimal habitat occupation of the alpine species. An alternative explanation is that the alpine bee species possess both the ability and body type to survive the colder temperatures, which naturally separates the two types of bees into distinct ecological territories. Alpine species usually have a larger body length in comparison to subalpine species.


Colony cycle


Initiation

''Bombus polaris'' queens
hibernate Hibernation is a state of minimal activity and metabolic depression undergone by some animal species. Hibernation is a seasonal heterothermy characterized by low body-temperature, slow breathing and heart-rate, and low metabolic rate. It most ...
for about nine months, suspended in an almost lifeless state in a mouse nest or some other burrow and waiting for the ground to warm. After this, ''B. polaris'' fertilized queens emerge from hibernation, visiting flowers and looking for areas to build potential nests. This signals the start of the seasonal cycle of development. Recently started colonies can be found in June or July.


Growth

''B. polaris'' is a social bee that requires a completion of at least two generations every year. To make up for this short amount of time, the queens produce many workers per generation. The initial brood is a clutch of around twenty larvae that emerge in about ten days. Arctic bumblebee larvae grow fast, and will experience a near tropical environment due to the heat production of their queen, and later on, of the workers. Arctic bumblebees have a larger initial brood as an adaptation to speed up the colony cycle in the very short growing season. Since the queen has time to produce only a few broods, she must also lay very large egg clutches. The life cycle is sped up by incubating the eggs internally that are already in the abdomen, thus increasing the rate of egg production and egg growth.


Behavior


Foraging

''Bombus polaris'' is one of the few bumblebee species where the queen will continue to forage while some workers have already emerged in the nest. She divides her time between incubating her brood and regulating the temperature of the nest to leaving the nest to forage. The food reserves gathered in the day are generally sufficient for only one night. When the bees exhaust their food, they enter
torpor Torpor is a state of decreased physiological activity in an animal, usually marked by a reduced body temperature and metabolic rate. Torpor enables animals to survive periods of reduced food availability. The term "torpor" can refer to the time ...
and cease to incubate. Occasional periods of semi-starvation lasting for a day or two do not harm the colony. The bees simply become drowsy and remain in a state of suspended animation.


Life history and survivorship curves


Colonies

The colony begins in the summer in June. The colony is only able to survive for two or three months until winter hits again. All
workers The workforce or labour force is a concept referring to the pool of human beings either in employment or in unemployment. It is generally used to describe those working for a single company or industry, but can also apply to a geographic reg ...
, drones, and most females die with the colony.


Workers

The queen's first brood after the start of the colony will develop into worker bees – small sterile females who will enlarge the nest, forage, and tend to the next generation of bees. Worker bees will die along with the colony at the beginning of winter.


Queens

The queen is the sole survivor of her colony after 9 months of hibernation during the winter. In the Arctic, only one queen per colony on average will survive the winter to renew the next life cycle. The colony only has one or two months to complete the social cycle of two generations. The old queen dies with her progeny.


Males

The queen's second brood in late summer include male drones and fertile females who are candidates for next year's queen. The drone's sole function is to fertilize the females, but most females will die along with the drones at the beginning of winter.


Interaction with other species


Food

Large
zygomorphic Floral symmetry describes whether, and how, a flower, in particular its perianth, can be divided into two or more identical or mirror-image parts. Uncommonly, flowers may have no axis of symmetry at all, typically because their parts are spirall ...
flowers of ''
Pedicularis ''Pedicularis'' is a genus of perennial green root parasite plants currently placed in the family Orobanchaceae (the genus previously having been placed in Scrophulariaceae '' sensu lato''). Description Between 350 and 600 species are acce ...
'' are dependent on ''B. polaris. B. polaris'' works the spikes of ''Pedicularis'' upwards from the bottom. Through this behavior, the adaption of
gustatory The gustatory system or sense of taste is the sensory system that is partially responsible for the perception of taste (flavor). Taste is the perception produced or stimulated when a substance in the mouth reacts chemically with taste receptor ...
organs to sugar is offset by the increasing concentration of sugars in the nectar up the spike. This behavior is also significantly related to pollination.


Predators

Predators of ''Bombus polaris'' include the
Buff-breasted sandpiper The buff-breasted sandpiper (''Calidris subruficollis'') is a small wader, shorebird. The species name ''subruficollis'' is from Latin ''subrufus'', "reddish" (from ''sub'', "somewhat", and ''rufus'', "rufous") and ''collis'', "-necked/-throated" ...
(''Tryngites subruficollis''),
common eider The common eider (pronounced ) (''Somateria mollissima''), also called St. Cuthbert's duck or Cuddy's duck, is a large ( in body length) sea-duck that is distributed over the northern coasts of Europe, North America and eastern Siberia. It breed ...
(''Somateria mollissima''), and
Long-tailed duck The long-tailed duck (''Clangula hyemalis''), formerly known as oldsquaw, is a medium-sized sea duck that breeds in the tundra and taiga regions of the arctic and winters along the northern coastlines of the Atlantic and Pacific Oceans. It is th ...
(''Clangula hyemalis''), which will either eat the bees or feed them to their young.


Parasites

''
Bombus hyperboreus ''Bombus hyperboreus'' is a species of Arctic bumblebee with a circumpolar distribution. The species is primarily found in the arctic areas of Greenland, northern Scandinavia, and Russia. In 2015 the nearctic species, '' Bombus natvigi'', was sep ...
'' habitually takes over the nests of ''Bombus polaris''. Because of the short Arctic summer, ''B. polaris'' normally has time to produce only one brood of workers before the colony has to raise queens. When ''B. hyperboreus'' takes over the nest, all of her young are raised as queens by the ''B. polaris'' workers. Thus, ''B. hyperboreus'' workers are not produced and pollen collectors are never seen.


Humans

Due to its cold tolerance the ''Bombus polaris'' appears to be one of the earliest pollinators of vegetation in the Arctic each year. Some plants they pollinate include Arctic poppies, Arctic roses, and
Arctic willow ''Salix arctica'', the Arctic willow, is a tiny creeping willow (family Salicaceae). It is adapted to survive in Arctic conditions, specifically tundras. Description ''S. arctica'' is typically a low shrub growing to only in height, rarely to ...
s. Their pollinator effect seems to be heaviest in the early spring, but decreases as the year continues. Samuel Robinson has found that, by the time most scientists arrive for the brief warm summers, the "Bumblebees (Bombus ''spp.'') and Butterflies and Moths (Lepidoptera) were found to play a minor role in pollination, while flies (Dipterans) were shown to be the major pollinators."Samuel Robinson, "Plant-Pollinator Interactions at Alexandra Fiord, Nunavut", ''Trail Six'', Vol.5, 2011. One of the leading modern experts on ''B. polaris'', Bernd Heinrich, agrees with this finding, saying that when "it gets warm, there’s a lot more fly pollination, and there’s actually some pollination by mosquitoes, as well."


References


External links

*NatureServe. 2015
''Bombus polaris''.
NatureServe Explorer Version 7.1. Accessed 3 March 2016.

{{Taxonbar, from=Q1924172 Bumblebees Hymenoptera of North America Hymenoptera of Europe Hymenoptera of Asia Insects described in 1835 Insects of the Arctic