Believe it or not, this works.

http://ufinsect.ifas.ufl.edu/deerfly_trap.htm

I have adapted it to mount on my mower. The key is making sure that the trap is higher than your head when you are seated. I sometimes just drive around and watch the little @#$% land on it. It gives me great pleasure.
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"A fanatic is someone who can't change his mind and won't change the subject" Churchill