Bees are the most effective pollinators because they actively collect large amounts of pollen to feed their developing young, and they are very effective at distributing pollen among flowers compared to other insects. However, other insects are important as well and must not be overlooked. Second to bees, flies are the most effective pollinators. Syrphid flies (in the family Syrphidae) and bee flies (in the family Bombyliidae) actively feed on pollen and nectar and are significant contributors to crop pollination. Bee flies are often mistaken for bees because they share a resemblance through their fuzzy, pollen-attracting body hair.
Butterflies are iconic pollinators. They feed on nectar and incidentally transmit some pollen from plant to plant, however their lack of body hair make them less efficient at pollinating. Similarly, adult wasps also feed on nectar and incidentally carry pollen from one plant to another as they forage, facilitating pollination to some degree.