As an EE, I'm getting nervous about the safety of these recommendations.
They can be implemented safely, but don't try it unless you *really*
understand what you are doing.
Save yourself alot of grief: Buy a submersible aquarium heater with a
built-in thermostat. Set the temperature to 80-85F, put the heater in a
quart glass jar filled with water, and set the jar in your terrarium. Make
sure and keep the water topped up. You'll get nice even heat and the
hot water contributes to keeping the humidity up.
Another trick is to time your lights to run at night. That way you don't
overheat the tank during the day, and you get extra heating during the cool
of the evening. This works best if your terrarium is in a room that doesn't
get much outside light. Otherwise the day length will be confused.
-- Rick