Snail Killing/ Marsh Fly-Coremacera marginata

I was going to put up a different image but this is an unusual one, and although the title sounds horrible I've never seen one attack a snail.....yet!
The Extra is what was going to be my main image
SYRPHINI Chrysotoxum bicinctum (Female) A wasp mimic hoverfly and what a beauty she is.

Draco