Are all bees important pollinators?

The bees that do not pollinate

Around fifteen to twenty per cent of bee species are cleptoparasites — cuckoo bees. Nomad bees, blood bees, mourning bees, cuckoo bumblebees and dark bees all lack pollen-carrying structures entirely, because they do not collect pollen. They lay in another bee's provisioned cell and their larva eats what the host gathered.

They visit flowers for their own fuel and pollinate incidentally at best. Their ecological value is real and different: an obligate parasite requires an abundant host population, so their presence indicates habitat quality rather than pollination service.

Why some pollen collectors are better than others

This is why a few hundred mason bees can pollinate an orchard that would otherwise need several honey bee colonies. Being untidy is the advantage.

Behaviour matters too

• Buzz pollination. Bumblebees and blue-banded bees vibrate anthers to release pollen; honey bees cannot, which is why tomatoes and blueberries depend on them.
• Nectar robbing. A bee that bites through the base of a flower is fed and pollinates nothing. Short-tongued bumblebees do this routinely to deep flowers.
• Flower constancy. A bee that works one species at a time delivers pollen where it can be used; one that switches wastes it.
• Temperature tolerance. Mason bees and bumblebees fly in cool weather that grounds honey bees, which matters enormously for early fruit blossom.

Why this matters for conservation

Treating bees as interchangeable produces the recommendation to keep hives, which helps one managed species and does nothing for the wild ones. The bees doing pollination work that cannot be replaced are frequently the specialists and the solitary species, and they need habitat rather than hives.