Flower flies in the Genus Metasyrhus are amazing bee mimics. If you were to see this insect buzzing around your head or your flower bed you would be hard pressed at a glance to tell if it were a bee or a fly. This mimicry gives them outstanding protection against predation. If you look like a bee chances are predators, who have learned the hard way that bees hurt, will leave you alone. One draw back to this mimcry is human predators, who will often swat and ask questions later. Most people never give a thought to the fact that there are harmless insects out there buzzing around their yard that only look like stinging insects, but in fact are harmless flies, minding their own business, pollinating flowers. To people it seems if it looks like a bee, and it sounds like a bee, it must be a bee.
All flies in this genus take nectar from flowers and some will "milk" aphids for the honeydew. Having these harmless flies in your garden is a good thing, they help control aphid populations, and the pollinating they do can only help those already overworked honey bees.
These flies are common throughout all of North America, and can be found in a wide variety of habitats, including woodlands, gardens and open fields. They are often seen "hovering" around flowers which also earned them another common name of "hover fly".
After mating, females will lay eggs singly on twigs or leaves near aphid populations. The newly born larva will feed on aphids. It is not uncommon for them to consume as many as 17 aphids in a single day. Depending upon species it can take from 9 to 14 days for them to reach adult size.
If you see something that resembles a bee, take a deep breathe, don't start swinging, and watch closely, for it may be only a fly.