An anthomyiid fly (Anthomyiidae)

An anthomyiid fly (Anthomyiidae)

Observation - An anthomyiid fly (Anthomyiidae). Description: A fly on a Marsh Marigold flower. Where's a good place to start in learning to identify these critters? Edit: Changed to match Martin's ID. Many thanks.

A fly on a Marsh Marigold flower. Where's a good place to start in learning to identify these critters?
Edit: Changed to match Martin's ID. Many thanks.