Page "Bee" Paragraph 12

The population value of bees depends partly on the individual efficiency of the bees, but also on the population itself.

Thus while bumblebees have been found to be about ten times more efficient pollinators on cucurbits, the total efficiency of a colony of honey bees is much greater due to greater numbers.

Likewise during early spring orchard blossoms, bumblebee populations are limited to only a few queens, and thus are not significant pollinators of early fruit.