Unexpected Spring Parsley vistors

Descrission:

While I have seen different species of bees on Cymopterus longipes in the past, I don't recall seeing these flies before. One of the earliest native plants to bloom in our area.March 24, 2012, Red Butte Garden natural space, Salt Lake City, Utah, approx. 5400 ft. elev.(Note comments below from Kerry Matz that these appear to be March Flies in the family Bibionidae.)