Arctic bumblebee
Bombus polaris is a common Arctic bumblebee species. B. polaris is one of two bumblebees that live above the Arctic Circle. The other is its social parasite Bombus hyperboreus. 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, and makes insulated nests.
This bumblebee has a wide circumpolar distribution, found in Canada, Arctic Alaska, Arctic islands (Devon Island, Ellesmere Island, Baffin Island and Greenland), northern Scandinavia and across Arctic Russia (Nenets, Yamalo-Nenets, Sakha 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.
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 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.
Large zygomorphic flowers of Pedicularis are dependent on B. polaris. B. polaris works the spikes of Pedicularis upwards from the bottom. Through this behavior, the adaption of gustatory 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.
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. 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 bumblebees from temperate climates.
