There are eighteen species of bumblebee in Scotland, the Great Yellow Bumblebee, Bombus dintinguendus, is the rarest. It was once found across Britian, but is now only found in the Western Isles, Orkney and on the far north coast of mainland Scotland, remaining populations are largely on crofts and nature reserves.
Bumblebees are social insects that live in colonies that are made up of both males and females. Females are divided into queens and workers, the queens are the largest and are responsible for establishing colonies, the workers are smaller and perform the domestic tasks of the colony.
Colonies do not survive from year to year, they survive as long as potential food plants are flowering, once food becomes scarce the new queens hibernate until the following year. In the spring the queens emerge and search for a suitable nest site, often using abandoned rodent burrows, to set up a colony of her own. In the nest they rear small daughter bees, the workers, which take over foraging for food. The nest grows until it may have a hundred or more workers, for the Great Yellow Bumblebee the numbers of workers is quite low; this may be because the workers tend to be quite large compared to other bees species. In August – September the nests rear new queens and male bees, which leave the nest to mate. The mated queens burrow into the soil to hibernate and do not re-emerge until the following spring. The old queen, her workers and the males all die in Autumn, and the old nest decays and disappears.
Bumblebees forage all day and sometimes at night. Bad weather can affect flight but bees are renowned for their ability to work in conditions that may hamper other insects. They seem to be well adapted to withstand cold conditions and their hairy coats can act as insulation. Heat production is essential for flight and unless a bumblebee can raise its body temperature to above 30ºC it will be unable to stay airborne because its sluggish activity will mean that the wings beat too slowly.
The Great Yellow Bumblebee is a large sized bee with a yellow or brownish body with a black band between the wings. Adult bees are found between April and September. Working bees are quite fast and therefore may be difficult to approach when feeding. It’s scientific name, Bombus distinguendus, comes from the fact that when protecting their nests the bees omit a strong aromatic odour to warn off predators.
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