Stone (1965) listed six species in the genus Sphaerophoria found in North America east of the Mississippi River:
Yokoi and Fujisaki (2009) described a "hesitation behavior" of Sphaerophoria spp. flies that was not present in several other species of Syrphid they observed, nor in bee species they studied. This behavior consisted of "moving backwards and forwards in front of a flower," possibly assessing the risk of predation, before deciding whether to light there and begin foraging.
Insects of West Virginia