Is a murder being committed?   This bee-like insect was attacking a hoverfly and had appeared to have dislodged one of the wings and seemed to be biting or strangling the hoverfly.  I know some insects lay eggs in a living host but think they normally choose caterpillars.  Perhaps someone can inform me what the creature is doing.

EDIT   Magi has identified it as a Yellow Dung Fly which hunt and eat flies.