Some of the flower flies aka hoverflies family Syrphidae are so large that they closely resemble bees. Often I can't tell that they are flies, not bees, until I zoom into the photos and see the distinctive differences.
For example, here is a flower fly on a Siskiyou Wooly sunflower.
You can always tell from the distinct pattern, then there is only one pair of wings, the antenna are short and stubby, and there is no pollen stored anywhere on their bodies.
There are nearly 900 species of flower flies in North America.
They also pollinate and their larvae eat scales, aphid and other soft-bodied plant pests.
Here is another kind of flower fly on a California yellow yarrow Eriophyllum confertiflorum .
Both flower flies are feeding on the nectar of "open flowers" (as opposed to tubular flowers).