Ecology of Species of Bombus Latr. (Hymenoptera: Apidae) in Southern Alberta. III. Subgenus Cullumanobombus Vogt

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Abstract
The subgenus Cullumanobombus is represented by Bombus rufocinctus in the Nearctic region. In southern Alberta, its distribution is confined to the wooded areas. There, it is adaptable in its nest-selecting habits, and establishes nests mostly in June. It made 11.2 ± 1.4 cells in the first brood. In each cell, one egg was laid in the first brood, 4.2 ± 1.2 eggs in the second and third, and 8.2 ± 3.9 in the fourth and later broods.Queens required about 22 days to rear workers. The second and third broods were usually workers and the fourth and later broods usually males or queens. The workers in a colony varied little in size. The dominant color pattern was B. rufocinctus s. str. This species is a prolific producer of wax.The queens mated in the morning and hibernated in the afternoon, about an inch deep in the soil.Many queens invaded other nests of the same species. The natural enemies were the three species of Psithyrus indigenous to the area, the big-headed fly, Physocephala texana, and ants.