Bombus vosnesenskii, the yellow-faced bumblebee, is distributed through western North America

North America

North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...

. This species grows to 1–2 cm (0.393700787401575–0.78740157480315 ) long, with queen being larger than the workers. B. vosnesenskii is characterized by the yellow coloration of the head pile, the mostly black thorax and abdomen, a single yellow thoracic stripe on the lower abdomen, and blackish wings.

Life cycle

The overwintering queen first appears during spring and establishes underground colonies. After laying her first brood she, and the workers

Worker bee

A Worker bee is any female eusocial bee that lacks the full reproductive capacity of the colony's queen bee; under most circumstances, this is correlated to an increase in certain non-reproductive activities relative to a queen, as well...

, will incubate the cluster until the adults emerge. The queen and workers use thermoregulation

Thermoregulation

Thermoregulation is the ability of an organism to keep its body temperature within certain boundaries, even when the surrounding temperature is very different...

 to incubate the cluster. The fuel for the bumblebee's thermoregulation during incubation is derived from honey

Honey

Honey is a sweet food made by bees using nectar from flowers. The variety produced by honey bees is the one most commonly referred to and is the type of honey collected by beekeepers and consumed by humans...

 (when the bumblebee is not foraging), nectar, and pollen

Pollen

Pollen is a fine to coarse powder containing the microgametophytes of seed plants, which produce the male gametes . Pollen grains have a hard coat that protects the sperm cells during the process of their movement from the stamens to the pistil of flowering plants or from the male cone to the...

. Late in the season males and young queens leave the nest and mate. While old males, queens, and workers die. The new queens overwinter and the cycle continues.

Behaviors

B. vosnesenskii, like most bumblebees, use thermoregulation to maintain a stable body temperature several degrees above the ambient temperature. At rest, bumblebees have temperatures close to ambient temperature. To generate power for flight, bumblebees need to raise the temperature of the flight muscles

Insect flight

Insects are the only group of invertebrates known to have evolved flight. Insects possess some remarkable flight characteristics and abilities, still far superior to attempts by humans to replicate their capabilities. Even our understanding of the aerodynamics of flexible, flapping wings and how...

 to above 30 °C (86 °F). The route of heat exchanged in B. vosnesenskii is regulated by the heat transfer from the thorax to the abdomen by the variations of hemolymph

Hemolymph

Hemolymph, or haemolymph, is a fluid in the circulatory system of some arthropods and is analogous to the fluids and cells making up both blood and interstitial fluid in vertebrates such as birds and mammals...

 flow in the petiole, the narrow region between the abdomen and thorax. At low ambient temperature, the hemolymph flows from the thorax and abdomen simultaneously. As a result, the counter-current exchange

Countercurrent exchange

Countercurrent exchange is a mechanism occurring in nature and mimicked in industry and engineering, in which there is a crossover of some property, usually heat or some component, between two flowing bodies flowing in opposite directions to each other. The flowing bodies can be liquids, gases, or...

of heat in the petiole retains most of the energy in the thorax. When ambient temperature is high, the flow between the thorax and abdomen alternate. The amount of counter-current heat exchange in the petiole is reduced and allows hemolymph to transfer large amounts of heat from the thorax to the abdomen.