Abstract
Oocytes of queen bumble bees from southern Alberta were partly developed when the queens emerged from hibernation in the spring. Early emerging species had less autumnal ovariole development and fed longer in spring before establishing a nest than did later emerging species. The main increase in oocyte size was synchronous with the finding of a suitable nest. The mean length of the largest oocyte for workers for all species was small, less than 0.7 mm, clearly indicating that workers contribute few males to the population.