Giant Bumble Bee

B. dahlbomii is predominantly red-orange in color. The thorax of the bee is completely red-orange while the abdomen is generally a lighter shade of orange with a small amount of lightening/discoloration towards the end. Like most bumblebees, the abdomen of the bee has a rounded tip. The head, wing and leg region of B. dahlbomii are distinctly black in color. B. dahlbomii has relatively short antennae and a distinct forewing and smaller hindwing that are usually tucked in above the main thorax area (they lie almost flat). Relatively long bristles cover almost the whole thorax and abdomen of B. dahlbomii, giving the bumblebee an extremely furry appearance. The leg and head regions are covered by shorter bristles than the thorax and abdomen. B. dahlbomii queens usually have relatively heavy body masses of around 0.5-1.5 grams and large head-to-tail lengths of up to 4 cm. These measurements make B. dahlbomii one of the largest bumblebees in the world and give it the nickname the "flying mouse".

B. dahlbomii is the only native bumblebee species in southern South America. Its range extends from 30 degrees southwards to the southern tip of mainland South America. It is endemic to temperate forest regions in central/southern Patagonia. B. dahlbomii is distributed throughout Patagonia, where it coexists with two non-native species that belong to the same genus, Bombus terrestris and Bombus ruderatus. In its distribution in Chile and Argentina, including Patagonia, B. dahlbomii occupies forest environments that have both continuous and fragmented (scattered) distribution of plants, flowers and other resources. Individuals in these two environments have slightly different morphological and behavioral features. Although some reports cite B. dahlbomii outside of southern South America, they fail to substantiate their findings; when compared to other South American bumblebees, B. dahlbomii's range is relatively confined.

B. dahlbomii queens initiate colonies. Queens forage for nectar and pollen that are used to feed the initial brood of a new colony nest site. The foraging activity of queens usually stops once the first brood develops into fully mature workers that can forage to feed immature siblings and alleviate the queen's need to perform such duties. After this happens, the queen assumes her main role of laying and incubating the brood eggs to further propagate the colony and produce new workers. Once workers begin foraging activities, B. dahlbomii queens seem to venture out of nests less frequently, but are still found in the outside of nests quite often.