generating shocks

Hi. I am trying to set up an experiment (a demonstration, at first) of classical (Pavlovian) conditioning on bugs. I thought the easiest thing to do would be to give them little electric shocks (without killing either of us).

More information: I will put the bugs (caterpillars, really) in a box, generate a vibration, then give them a shock. They produce a particular response when stressed and I'm hoping that the vibrations will become associated with the shock and will trigger that response in anticipation of the shock. Periodically, I'll omit the shock and see if they produce that response.

I know how to generate the vibration. I know how (more or less) to set up the timing and repeated trials. The shock is the problem. I don't want to fry them but I also don't want them to ignore the shock. Suggestions?

Once I figure the shock out, I'll want to keep track of the number of shocks and the number of times I don't give a shock on a little screen so I can film it as a demonstration. Afterwards I plan to run a bit more complicated experiment.

I suggest doing some research, as those sorts of experiments have been done many, many times, even with such simple animals as flatworms (first reported in 1955).

Google "training planaria with electrical shocks" for examples. You may even be able to find a copy of the 1987 student lab manual describing similar experiments with earthworms!