Ummmmmmmmmm the average Bug Zapper uses a transformer to step up the voltage to around 2000 volts. there is a gap between a grounded mesh and the energized mesh with a light inside the 2. when Mr bug passes thru the first mesh and make similtaneous contact with mesh 2 he is basicially vaporized. In terms of current I aint sure but it wouldnt take much current to do in a bug.
They are not good for Skeeters cause skeeters aint attracted to the light,like junebugs or flys .