Ecology of Species ofBombusLatr. (Hymenoptera: Apidae) in Southern Alberta. V. SubgenusSubterraneobombusVogt

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Abstract
Both Nearctic species of Subterraneobombus occur in southern Alberta, but Bombus (Subterraneobombus) appositus Cress. is confined to the wooded areas whereas B. (S.) borealis Kby. is confined to the prairie. Both are adaptable in their nest-selecting habits and are among the latest species of Bombus to emerge and establish nests in their respective habitats.Both species made large first broods; B. appositus averaged 13 ± 3 cocoons in 119 first broods. B. appositus never had more than two broods of workers, and B. borealis had only one. Both constructed pollen pockets beside and beneath the young larvae of the second and succeeding broods. Queens of B. appositus required about 23 days to rear the first workers. The largest workers of both species were considerably smaller than average-sized queens. Colonies of both species were relatively small; those of B. appositus averaged less than 100 individuals, the largest being 246. Both species were apparently sparse producers of wax.Queens of both species apparently mated with males in the nest or immediately upon leaving the nest. New queens of B. appositus dug about one inch into the ground to hibernate.Females of the cuckoo bee, Psithyrus insularis (Sm.), succeeded in having their young reared to maturity in nests of B. appositus.