Image Credit: Ryan Hodnett
Hover-flies (Syrphidae – whole family) – pollenivores. Unlike most non-bee flower-visitors, the hoverflies actually consume pollen. By consuming pollen the amount of pollen grains left for pollination becomes much less, but by spending the extra time to consume the pollen they visit more portions of the flower and more pollen ends up stuck to their face, chin and belly. The pollen on their bellies is what ultimately is important for pollination (as it is on the bee body as well). Though female bees groom themselves constantly and remove some of this type of pollen, I don’t think that hover-flies engage in grooming.
A classic hornet-mimic hoverfly clearly feeding on pollen, rather than nectar.