Bombylius major flies with its thorax and abdomen oriented at about a forty five degree angle relative to the horizon. It can fly fast enough to be hard to follow with the eye, and it can hover in place for several seconds.
I watched ours for a while. It is reported that the larva parasitize the nests of ground-dwelling bees, and that the females place their eggs in the entrance tunnels of those bees. I was not able to observe this behavior.
This is a fun fly to watch.