Biff, bash, bosh!

The theory is, apparently, that because flies have such large (proportionately) and complex eyes, they see the world - and in particular any attempt by us to swat them - in slow motion and are thus able to avoid the newspaper, or whatever it is we are trying to duff them with.  You don't seem to get so many flies as you used to, but when I was a kid, they were a continual nuisance and during the summer months most rooms had an old-fashioned fly-paper hanging from the light fitting. The way I was taught was (1) never try to swat a stationary fly - wait until it moves, and then (2) always aim just behind it - the idea being that in an emergency, a fly will take off backwards. Where that came from I don't know, but it did seem to work reasonably well.  Or perhaps I was just faster back then - these days I tend to open the nearest door or window and try to usher the little bugger out with whatever comes to hand.